An idiot’s guide to aircraft design – Part 1: How to build the fastest-climbing fighter

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Seconds matter when intercepting enemy bombers or a sky-jacked airliner, so an effective interceptor should have a high climb rate. In layman’s terms a fighter optimised to achieve a high rate of climb will be skinny with a highly swept wing and a large amount of excess power. Here Jim Smith explains the reasons for this.

“Climb rate may be calculated using the equation below. The factors determining the maximum climb rate achievable can be determined from this equation:

((Thrust – Drag)/Weight) x V, where V is the aircraft speed”

If, like me, the sight of an equation has you skim reading and feeling anxious do not worry. I’ll try to explain this in terms even I could understand. Thrust (the force pushing the aircraft forward) minus drag (the force working against thrust) divided by the aircraft’s weight multiplied by the aircraft’s speed gives you the climb rate. We won’t bother learning about the units used for this for now. To relax those intimidated by equations here is a picture of a dog to calm you down.

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I’m a lovely dog and everything is OK. 

“From this equation, we can extract the factors that lead to achieving a high climb rate. The excess thrust available to climb is the difference between the maximum thrust available, and the thrust required to offset drag and maintain level flight.”

Meaning you need a certain amount of thrust to keeping go as you are, any extra thrust left over can help you climb. The more ‘grunt’, the faster you will climb. 

Wings area doesn’t matter

Wing area (how much wing you have) doesn’t matter. The thing about the equation is that it tells you at a glance that wing area does not matter, it’s all about excess power. Where the wing comes in, is in what I would call second order effects. If the wing is too thick the drag will be higher – so the excess power will be less, and the climb rate lower. If the wing is thin and highly swept, the drag rise mach number will be higher, the aircraft speed can be higher, and the climb rate will be greater. Think about rockets. It is not at all necessary to have wings to have a spectacular climb rate.

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Wings are not required for a fast climber. Here Sandra is about to destroy the phallocracy with one small hand movement. 

“The aircraft speed (V) is important, because it is the vertical component of this that is actually the climb rate. However, aircraft speed also affects drag.  As the aircraft speed increases, drag initially typically decreases because, in level flight, at higher speed, the aircraft flies at a lower incidence, and lower lift coefficient, and lift-dependent drag reduces.” For magical reasons the drag reduces as the aircraft’s speed increases. 

However, as the speed increases towards the speed of sound, drag will typically increase rapidly. As local areas of flow become supersonic, drag increases significantly, and the Mach number at which this occurs is referred to as the drag-rise Mach number. Configurations with highly swept wings such as the Lightning, or with very high fineness ratio (length to cross-section, meaning skinny) and thin wings, such as the F-104, will have higher drag-rise Mach numbers, allowing a higher climb-speed (V) and a greater rate of climb.

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Point defence interceptors, like the English Electric Lightning, were so-called because it was envisaged they would react to a threat by climbing rapidly and racing out to intercept bomber aircraft before they could release their weapons. They were ‘point designs’ (nothing to do with ‘point defence’) in that one point – climb rate in this case- dominated the requirements, and were made obsolete once threat aircraft adopted high-speed long-range stand-off weapons.

The maximum climb rate is likely to be achieved at a subsonic speed close to, but less than, the drag-rise Mach number. Configurations with high Thrust-to-Weight ratio, low drag, and a high drag-rise Mach number will achieve the highest climb rate.

At which point, we come to the difficulty. Today’s aircraft simply don’t have the luxury of being point designs.

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Point design means an aircraft designed for one, generally extreme, performance requirement. The Rutan Vogager is an example of an aircraft driven solely by the maximum unrefuelled range.

 

To really maximise climb rate, you also want to minimise aircraft weight. Yes, it can be done – the recent Hush-Kit article on the Streak Eagle showed exactly how to do it. Take the radar out. Take the gun out. Calculate the fuel needed for your flight profile, and minimise the reserves. Strip the paint off. What you end up with is a hot rod that’s only useful for breaking records. 

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It’s not thrust-to-weight that matters – it’s the ratio between the excess thrust available and the weight. The Starfighter was a skinny, low drag aircraft with a thin wing and enjoyed a good climb rate. 

But put a little radar back in, add a couple of heat seeking missiles, and you get something of a specialist interceptor. Fabulous climb rate, miserable range – a Lightning or an F-104, where mission performance has been subjugated to a single point performance parameter – the minimum time to intercept from a standing start.

Climb at all costs 

Of course, the Messerschmitt 163 Komet was perhaps the first exemplar of an extreme point-defence interceptor. Take a tiny aircraft with a rocket motor – light the blue touch paper and watch it climb like an angel, fire off its weapons, run out of fuel and glide back to land.

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Do point-defence interceptors exist in the modern world? Well, not really. A strategic interceptor like the MiG-31 has to cover vast distances, and although having huge engines, also has a massive fuel load to carry. The MiG-31 can achieve high speed and high altitude, but in realistic missions will probably be carrying too much fuel to deliver its potential climb rate.

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For most air forces, standing combat air patrols (CAP) supported by air-to-air refuelling offers a more rapid and further reaching response than the ground-based interceptor responding to a Quick Reaction Alert (QRA) call. Acceleration from (say) CAP at Mach 0.8 at 25,000 ft to Mach 1.8 at around 40,000 ft is now perhaps more of a driver than pure climb rate.

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Nominees for best historic climb rate: the Lightning and the F-104. Technically, the F-104 may have had a greater initial climb rate, but it was scarcely ever employed in the point defence interceptor role, so I prefer the Lightning. For current aircraft, there would not be much to choose between any of the current generation 4.5 fighters Typhoon, Rafale, or even a MiG-31 at light weight.” 

Fast climbers

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According to both Typhoon pilots and Eurofighter nothing can out-climb the aircraft, if this is true, likely contenders for second place include Rafale and F-22. The Typhoon is a low-drag lightweight design, with a large power-to-weight ratio. As it is not a stealth design its aerodynamics are less comprised by a desire for a low radar cross section. The ‘Flanker’ or T-10 series, MiG-29, F-16, F-15 (particularly the F-15K) should also rank highly. A production Su-57 with izdeliye 30 engines seems likely to eclipse all, but this is not yet operational. Jim notes, “I’d expect Typhoon to be very good, Rafale to be very similar. F-22 does have plenty of power, and there have been some rumours that USAF would like more combat persistence, suggesting that operational weights for air combat issues may not be too high. I am a bit sceptical about the Su-57, as its size suggests that significant range is required, and that routine operations will carry significant fuel.”

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Take thirty seconds to click and donate here to keep this site going. Thank you. 

Want to see more stories like this: Follow my vapour trail on Twitter: @Hush_kit

Have a look at  Interview with a Viggen pilot, interview with a MiG-25 pilot, interview with a Gripen pilot, Top 10 BVR fighters of 2018. How to kill a RaptorAn Idiot’s Guide to Chinese Flankers, the 10 worst British military aircraftThe 10 worst French aircraft,  Su-35 versus Typhoon10 Best fighters of World War II top WVR and BVR fighters of today, an interview with a Super Hornet pilot and a Pacifist’s Guide to Warplanes. Was the Spitfire overrated? Want something more bizarre? The Top Ten fictional aircraft is a fascinating read, as is The Strange Story and The Planet Satellite. The Fashion Versus Aircraft Camo is also a real cracker. Those interested in the Cold Way should read A pilot’s guide to flying and fighting in the Lightning. Those feeling less belligerent may enjoy A pilot’s farewell to the Airbus A340. Looking for something more humorous? Have a look at this F-35 satire and ‘Werner Herzog’s Guide to pusher bi-planes or the Ten most boring aircraft. In the mood for something more offensive? Try the NSFW 10 best looking American airplanes, or the same but for Canadians. 

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An idiot’s guide to aircraft design: Introduction

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What is the fastest climbing aircraft? And the best at sustained turn? Which is the nastiest to land..and the nicest? And what is it about a particular aircraft’s design that gives it these qualities? Armed with these questions and many more, I went to pester Jim Smith, a man with significant technical roles in the development of the UK’s leading military aviation programmes, to get answers. 

Fortunately, his answers were far longer than I expected and instead of a one-off article, we will be sharing a fascinating series.

Over to Jim for the introduction.

Why are aircraft the shape they are?
“This question arises from a discussion between Hush-Kit and I about using specific aircraft as examples to illustrate how various requirements drive aircraft size, shape, wing planform, thrust-to-weight ratio and so on. In best Hush-Kit style, I’ve been asked to look for ‘best and worst’ in a number of categories, for example: High Alpha flight; Acceleration; Sustained turn rate; Instantaneous turn rate; Climb Rate; Agility and manoeuvrability at high and low altitude; nicest and nastiest to land. And of course, the desire is to focus on fighter aircraft.”

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“I’ll explore how different parameters drive aircraft design by considering not only fighter aircraft, but also other types of aircraft, noting that individual performance requirements are not the only requirements that drive aircraft configuration design. We’ll start a discussion of requirements for military aircraft, before looking at specific point performance and other requirements that influence their design.
Mission and Point Performance Requirements.”

BAC Lightning 2.jpg“In general, even fighter aircraft today are likely to be designed to meet a number of mission profiles, coupled with point performance parameters as constraints. So, requirements might be summarised as “deliver missions 1 through 5, while also achieving stated maximum g-loading, climb rate, sustained and instantaneous turn rates”. Each of the missions will have been matched to realistic operational scenarios, such as an interception from Quick Reaction Alert (QRA); an interception from Combat Air Patrol (CAP); an extended duration patrol; and perhaps also surface strike missions with differing weapons fits.
These mission requirements will generally determine the sensors and crew required (one or two-seat for the majority); the weapons, auxiliary sensor and targeting pods and tanks that may be carried externally; and, in the case of stealthy aircraft, what sensors and weapons must be carried internally.”

rs11518_xp693-9102796.jpg“Taken together, these reference missions will allow the ‘payload-range’ of the combat aircraft to be established, and this along with the determination of whether one or two engines is required, will define the size and (largely) the weight of the aircraft.
Point performance requirements will also be set. In some cases, these will be expressed as constraints, rather than targets, and they should also reflect the operating concept of the aircraft, and be coherent with the mission requirements. There is no point specifying a mission requiring extreme range, for example, and at the same time require that the cruise speed of the aircraft be supersonic at low level. If you do this – oh dear – you end up with a TSR2, where low-level supersonic range was apparently an enormous cost driver.”BAC TSR2 IMG_1501.jpg

“One of the reasons that point performance parameters are often set as constraints, is that the turning performance of typical fighter aircraft could easily exceed the tolerance of a human pilot, typically 9g, even with a ‘g-suit’. Consequently, many of today’s fighters are designed structurally to 9g loadings, which effectively means they deliver the same instantaneous turn rate as each other, at least at low to medium altitudes. Sustained turn rates are generally less likely to be structurally limited, and may vary rather more, dependent on wing sweep, aspect ratio, and thrust to weight ratio.
Point performance requirements are likely to include such items as climb rate, field requirements, maximum speed and operating altitude, the structural ‘g’-limit, and possibly others, depending on the role. There will also be plenty of system and reliability and maintainability requirements and targets, but these will not need to be covered here. (For a discussion of BVR combat requirements see my Hush-Kit article here)
The current multi-dimensional approach to combat aircraft requirements has not always been the approach. The Fifties were a period when huge advances had been made in the understanding of aerodynamics and in jet engine design, enabling great leaps in performance. So much so, that the capabilities of the aircraft could outstrip the thinking behind the military requirements being proposed.

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The best example of this is the Douglas A-4 Skyhawk. The Navy had in mind a 30,000-lb twin jet attack aircraft, with a 2,000-lb bomb load. What they got from Douglas was the Skyhawk, eventually with an empty weight around 10,000 lb and max TO weight of 24,000lb, able to carry up to 8,000lb of stores, at high subsonic speeds. (Picture)
In looking at specific requirements, I’ll use some of the older point-driven designs to illustrate the configuration trades being made, and indicate which current aircraft may provide best or worst examples. In addition, some civilian operations also require some fairly extreme configurations, so I’ll also consider some of those.

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We’ll being starting with a relatively straightforward topic, climb rate.”

Click here for part one.

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Want to see more stories like this: Follow my vapour trail on Twitter: @Hush_kit

Have a look at How to kill a RaptorAn Idiot’s Guide to Chinese Flankers, the 10 worst British military aircraftThe 10 worst French aircraft,  Su-35 versus Typhoon10 Best fighters of World War II top WVR and BVR fighters of today, an interview with a Super Hornet pilot and a Pacifist’s Guide to Warplanes. Was the Spitfire overrated? Want something more bizarre? The Top Ten fictional aircraft is a fascinating read, as is The Strange Story and The Planet Satellite. The Fashion Versus Aircraft Camo is also a real cracker. Those interested in the Cold Way should read A pilot’s guide to flying and fighting in the Lightning. Those feeling less belligerent may enjoy A pilot’s farewell to the Airbus A340. Looking for something more humorous? Have a look at this F-35 satire and ‘Werner Herzog’s Guide to pusher bi-planes or the Ten most boring aircraft. In the mood for something more offensive? Try the NSFW 10 best looking American airplanes, or the same but for Canadians. 

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Vote on the Top 10 aircraft of the Royal Navy

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We’ve been so busy researching the top 10 aircraft of the Royal Navy that we forgot to ask your opinion. We’re looking to choose 10 aircraft that best tell the story of British naval air power. Write a 250-word explanation of why your choice should be included (in the comments section below) and if selected, your aircraft and writing will be featured in the final piece. Please include your name. We look forward to finding out your opinions.

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Flying & Fighting in the Saab Viggen: Cold War Thunder

 

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Mikael Grev in the mighty JA 37 Viggen

Thundering over icing mountains, taking-off from motorways and tasked with defending a small neutral country from the biggest war machine in history, the Saab Viggen is a strong candidate for the most charismatic of the Cold War fighters. We spoke to former Viggen pilot Mikael Grev to find out more. 

“I have 600 hours on the JA 37 Viggen, which I flew from 1998 to 2003.  JA stands for Fighter and Strike (in Swedish) but Fighter was what it was all about. It is normally just called the Fighter Viggen and it was the best Viggen version, something all pilots agree on. Or it was the Fighter Viggen pilots that were the best – possibly both – I can’t remember.” Mikael noted with a tongue-in-cheek smile, “There were also Recce and Strike versions of the Viggen. There was almost no rivalry among the pilots of the different versions though.”
Acceleration
“The Viggen was capable of massive acceleration, at low level, as long as you didn’t turn much. The engine had a high-bypass ratio, which means lots of power at low level. On a cold day (we have plenty of those in Sweden) at 30 metres altitude, with 30 % fuel left and a clean aircraft it was like riding a rocket!”

Sustained turn rates
“Pretty bad by today’s standard. Of course, if you stayed at low level it was OK, but you basically controlled a big airbrake with your stick. i.e the Viggen itself was a large airbrake. The first versions actually had a normal air brake, but it was later welded shut since it did nothing compared to the induced drag you could get by pulling a few Gs”

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Instantaneous turn rate

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“OK, but since it didn’t have care free manoeuvring you had to take it a bit easy and keep track of the g-meter. It had a maximum 7g allowed, and that was with quite low fuel, so decent, I guess. It had a clever sound feedback system with beeping tones for high G and alpha (different pitch), so you could pull hard on the stick and still look at the target. But if you wanted that last bit of turn rate, you had to look at the G-meter with one eye and at the target with the other one. And preferably keep one eye one the alpha meter as well. Marty Feldman would be an awesome Viggen pilot!”

 

High alpha performance
“If we, being respectful to an old lady, interpret that as being able to keep exactly the maximum 23 degrees of alpha in a dogfight, it was fantastic. The flight control system was very good, again for the time. No problem to stay between 22-23 degrees while rolling and manoeuvring against a target in a dogfight.

If you went over 23 degrees or 7Gs you would ‘get the knife’ in your hand (a buzzer built into the stick) which told you to push the stick forward. If you went over 23 degrees you would get an automatic report after landing, and you didn’t want that since it also meant ‘a talk’ with the squadron commander. At 26 degrees alpha, or a bit above that, there was a real risk of super-stall.

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There was a trick here that some knew and used. You had to stay above 23 for two seconds or more to get a report. Since every degree count, you could milk it a bit and go back and forth between 24.5 and 23, as long as you didn’t stay above 23 for more than two seconds. If you went above 25 you were toast no matter the duration though.”

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Sensor performance & situational awareness
“Good for the time. We had a moving map in the JA 37 C/D, but it was monochrome, and vector based. The Di version, which came in the last years of service, had a colour moving map, just like in the Gripen.

Sensor-wise it had a pretty good radar, but with a limited range of around 60km. The Di version had a bit more due to better processing. The Radar Warning Receiver just told us the quadrant an aircraft locked on from and we had no forward looking infra-red, missile approach warning, laser designator pod or other fancy stuff. The recce camera, I have been told, was state of the art. Fortunately it wasn’t integrated on the Fighter Viggen.”

What was it like using the thrust reverser?

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“Like falling over forwards while braking on the runway. As a pilot you’re used to being pushed backwards, but when it was engaged after touchdown the forces got reversed. The more you push the throttle forward, all the way to full military power, the more you hung in your straps. It was good to have, especially at the road bases when it was icy, but honestly, I wonder if it wasn’t more weight to always carry around than it made good the few times it was used.”

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Another member of the Viggen family was the AJ37  used for ground attack missions.

Could the Viggen have survived against a Flanker?
“Yes, if we had numerical advantage around 2:1. 1 vs 1 air combat manoeuvring would be pointless, and we’d lose every time. The Flankers take more Gs, have a higher sustained turn rate and carries more fuel. Luckily the cold war never got warm.”

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Was its lack of agility an issue?
“Yes, in a sense. But this was in the mid-nineties and a lot of Swedes thought that eternal peace had arrived (Russia was good now and was never ever going to be bad again), and we had something of a strategic timeout. In that way the threat wasn’t really real and nothing military was a real issue. And, the Gripen was already well on its way to enter service and that had much better performance in almost every way.”

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It seemed a very different concept to fighters from other nations – was it an unusual concept? “We do have a very different geographical situation. A large country compared to population and lots of roads. Actually, today we try to get back to the road base system since it is a really good way to disperse the Air Force and make it harder to hit with cruise and ballistic missiles. A road base is easy to shut down but expensive to open again though, so we’ll see how many we can get back into use.”

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 Did you practice dispersed basing or motorway take-offs?
“Yes. The feeling when you stand in the beginning of the runway, ready to take off, with a forest wall a bit over 800m in front of you, is not unlike standing on the platform looking down when bungy jumping. Same thing when landing on that same strip, 800m seems rather short. It looks like it can’t be done, but then you know many have and you just do it.

How good was the SkyFlash missile?
“Not very good compared to AA-10-Alamo-A or C that the Flankers had. And what I know now about missile models and really fast target aircraft, it was very fortunate we didn’t have to use them in combat.”

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What was it like firing the cannon?
“Awesome! The Oerlikon 30mm was really good, not just for its time. It was actually so good that it was loosened a bit to spread the bullets. We had an air-to-air automatic aiming mode for it which used the radar. The pilot just moved the stick in roll and the aircraft calculated and controlled the pitch to hit the target. It was used to fire the gun on larger aircraft with great precision and it hit what it aimed at, if the target was going straight.”

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Click on the type name for interviews with pilots of the following aircraft: MiG-25, B-52, Mirage 2000, Hawk, Tornado, Phantom, F-100, MiG-21, MiG-27, F-35 , English Electric Lightning 

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Best & worst thing about flying the Viggen?
“The sound was the best. It was a deep, soft sound of pure power, just like a muscle car. I sometimes get the question how the Viggen and Gripen differs, and I usually say it’s like a Dodge Charger compared to a Porsche 911.”

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Most memorable mission?
“Since we didn’t ever do anything abroad with the Viggens – they weren’t really made for that – it’s probably the sortie where I flew the fastest. I had plenty of fuel left after a training mission just north of Gotland and were RTB just north of Stockholm. We had gotten the OK to go supersonic and I thought, well why not accelerate all the way home?

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I started at 30.000 ft and the aircraft just accelerated and accelerated. It must have been a newly serviced engine in combination with high pressure and cold air or something because this was more than usual. I throttled back just before feet dry at Mach 1.8+ and it was still accelerating like crazy! Usually there’s no problem reducing the speed with a Viggen but at that speed there was a feature that kicked in that meant you couldn’t go below full military power because of inlet pressure. And you couldn’t take many Gs either because of the high speed. So, land, with houses and stuff, approached and much quicker than estimated since the speed reduction took way longer than expected.

I thought I had broken every window in the Stockholm archipelago. Sitting on the squadron waiting for the first call to come in was a memorable part of that mission. But no one called. Not even a peep. I guess the weather conditions were on my side that time.”

Three words that describe the Viggen?
“Power. Steel. Fighter-Viggen-is-better-than-recce-and-strike.”

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Other articles on the Viggen: Here, here and here.

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Flying & Fighting in the Gripen: Interview with a Swedish Air Force pilot

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Marty Feldman

 

“I know the guys in the Swedish Air Force are very keen to fly their Gripens in air combat manoeuvres against Denmark’s and Norway’s F-35s. I think you can guess why.”

What is your favourite thing about Gripen?

“The large display real-estate. Gripen C/D has a huge Head-Up-Display (HUD) and three large colour Head-Down Displays (HDDs). This gives ample opportunity to create a high-fidelity user interface for the pilot. The big HUD is good for dog-fighting (even though that’s going away, as fun as it was) and HDDs is for Beyond Visual Range air-to-air combat and basically all other mission types that are the chess-playing of today’s air operations. A good pilot user interface and decision support system is an untapped and under developed innovation resource in fighter aircraft, as traditionally “hard” specs have been favoured, perhaps because they are easier to quantify into numbers. In a lot of scenarios, a next-gen system vs a standard “show where the sensor fused enemies are on the map” – can make a 5 to 1 difference. That’s huge, and comparable to the gap between aircraft generations. Gripen E/F will come with an even larger wide area display (WAD) and the possibilities for software upgrades becomes endless. Nowadays my company creates decision support systems for military aircraft and C2-systems, and without large high-fidelity screens to show it on, it wouldn’t be possible. Artificial Intelligence really makes a difference here, but perhaps not in the way many people think of it. AI is for us basically a way to reduce the calculations to fit within a fighter’s limited computing resources.”

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“The pilot is still in-the-loop with our AI though, and makes the tactical decisions, but is being presented with information that is richer and more pre-calculated to how the pilot is thinking. All this wouldn’t be possible without the larger screens that can convey the information. This is why it’s my favourite feature, it makes the aircraft more software upgradable. What is your least favourite thing? The refuelling probe length and position on the Gripen C/D. Even though I know the reasons behind the placing and length (retrofitted into an already set fuselage) it makes a mission component, that should be easy and predictable, an unnecessarily exciting part of the mission. Anecdote coming up! I’ve been told that when Gripen C/D was certified for air refuelling the subject matter expert pilot said something like: “Gripen has probably the world’s worst probe placement but compensates that with the world’s best flight control system.” I concur with the statement. You can fly to the basket/drogue and stay easily within a meter or so of it, positioning your Gripen with almost centimetre precision with the stick, but when you approach it the wake of the canopy will push it outwards. This means that you’ll have to “go for it” and aim a bit on the outside of the drogue. This is not a good recipe for predictability. You do get good at it after a while and learn how to do it safely, but a longer probe wouldn’t harm.”

Would you be confident facing an F-16?

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“Absolutely. I can’t think of anything the F-16 would be better at, if we don’t count ease of refuelling (F-16 is refuelled with a boom and the boom operator does much of the job). Of course, there’s a lot of details and circumstances here, but generally the Gripen is a step or two ahead, especially in my favourite areas. As mentioned, I really like pilot UI and large screens, and F-16 is lacking a bit in that area, so maybe I’m a bit biased. I do like the F16’s side-stick though! I have flown an F-16 and I loved the stick. It didn’t take many minutes to get used to the stiffer stick, and it’s more ergonomic for the pilot in high-Gs (and probably for long missions) to have it on the side. Flying in close formation with another fighter was almost as easy as with the Gripen.”

Which aircraft did you DACT with in Gripen and how would you rank them in terms difficulty to defeat? Any surprises?

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“I’ve flown against F-16s and F-18s. No surprises really, they are what they are. The F-16s are a lot like the Gripens but you can claw yourself closer and closer to their behind, if that is your goal.

For F-18s you have to look out for their ability to do high AOA turns for quick point-and-shoot. They will be sitting ducks after such a move though. The Gripen ‘carves’ through the air better then both and you will not lose as much speed when turning. Saying that, I believe that ACM is mostly a curiosity today, but a damn fun one and good for training aircraft handling. The IRIS-T missile is so good (and as are others) that everything you can see with your eyes is basically within your Weapon Employment Zone, WEZ. You can of course end up in a ‘furball’, having to fight your way out with guns, but it would suboptimal to craft fighters for that purpose today, as anyone with a missile left would win hands down. So, it’s always better to opt for one more missile than guns, if we’re talking ACM.

I know the guys in the Swedish Air Force are very keen to fly their Gripens in air combat manoeuvres against Denmark’s and Norway’s F-35s. I think you can guess why.”

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How you rate Gripen in the following areas:

Pilot comfort

“Very Good. You sit great, though not as leaned back as in the F-16. The suit is also great and give you enough support to make 9g fairly tolerable. The small number of gauges and knobs and the good reachability of everything you need to touch during a sortie makes the aircraft wonderful to work with. A side stick would give it a perfect score, but I know pilots that does not share my view on this.”

Instantaneous turn rate

“Perfect. You get 9g almost instantaneously for combat speeds, at most relevant altitudes. The care free manoeuvring means you can pull the stick as fast and hard as you want, and the aircraft will respond with 9g within a second or so, given you don’t have something hanging that make the flight control system automatically limit max g. No need for more here.”

Sustained turn rate

“Good. The Gripen “carves” very well through the air, much because of its all-moving canards and leading-edge slats. Even though it doesn’t have the thrust-to-weight ratio that for instance the Russian Su-35 have, it can hold it own. A pilot always wants more power of course, but if one is looking at the return on investment for more power to get combat effectiveness out of sustained turn rate, a bigger (i.e. heavier and more fuel consuming) engine is a hard sell.”

Climb rate

“Good enough. This is basically thrust-to-weight ratio. I’ve never felt the need to climb faster. I think max speed is more important since a higher speed means a lot in BVR combat. You can fire your weapons at longer distances and go further into an enemy’s WEZ if you have a higher speed.”

Combat effectiveness

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“Very good, with a possible trajectory to become stellar. The large screens on the Gripen makes it formidable for Situation Awareness (SA). Given that air operations are moving into more of a chess game than Top Gun turn and burn, the advantage is moving towards aircraft with great SA. Saab struggled initially, but in the long run it was a rewarding path to certify the on-board software in different levels. They call this app-thinking, and it means that all except the critical systems (like flight control software) run software that is not more critical than normal computer software. This can make it much (and I really mean much) cheaper and faster to develop new functionality for the Gripen. However, change is hard to achieve within a large organisation. If the mindset is still the same as for all other fighters in the world – that software for fighters should be developed like it always has been – the advantage will go away. Our company has bet on the prediction that Saab can and will make that mindset change and accept innovative features from external (and internal) suppliers.

Click on the type name for interviews with pilots of the following aircraft: MiG-25, B-52, Mirage 2000, Hawk, Tornado, Phantom, F-100, MiG-21, MiG-27, F-35 , English Electric Lightning 

Reliability

“Reliability is two-fold. How often will the aircraft break and how fast can it be fixed and sent back up again. Unfortunately, I don’t have the statistics on this, though it is my intuitive belief that Gripen is very reliable and extremely fast to get back up again. In operation Unified Protector (Libya) for instance, we had fewer aircraft and definitely fewer maintenance crew in our detachment than most (all?) other nations, and still managed to get a lot of flying time. I can’t remember a single mission being cancelled because of aircraft failure, and this was the first mission abroad for Sweden in 50 years and a new environment (much hotter). A full turn-around can be as fast as seven minutes if memory serves me, but a more normal time in day-to-day squadron ops is about 30 minutes with one maintenance crew for each aircraft. That is quite unique I think.”

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Was there any upgrades or equipment you wanted when you were on the Gripen?

“Lots! But that might be because I have been an inventor and innovator in this field for the two years. Many of the things are also now in the Gripen E. First and foremost, I would’ve liked to have a Missile Approach Warner (MAW) in the C/D. In a hostile environment you have to spend too much time looking at the ground without one, and the MAW is better at it anyway and never gets tired or distracted with pilot shit. I think the Gripen E’s AESA radar would be my next choice. The much greater search volume is nice, but I’m more excited about the increased flexibility in radar programs, anti-jamming, better low observability target tracking (de-stealthing) and such that AESA gives. When it comes to software, I’m probably most excited about the increased survivability our new optimal evasive manoeuvre AI algorithm HUMAN would give. It takes an incoming missile and calculates an optimal trajectory for the aircraft, given any number of overlapping priorities, like staying in doppler-zero* , aiming your Electronic Warfare System antennas towards it or just physically be as far away from the incoming missile as possible. Few pilots react perfectly when you might have seconds to live and an automated or semi-automated system might do a lot for pilot survival. Would it be too self-serving to also ask for our AI decision support system Rattlesnake? It keeps track of all known enemies and their history, our own capability and conduct massive parallel simulations (now off-line due to our patented AI) to be able to show the pilot (or fighter controller) how to fly to stay away from enemy missiles and how to manoeuvre for an optimal shot. I honestly want it as it would make me almost invincible in a BVR environment.  I could go on and on here, but maybe we should save that for a specific innovation interview?”

*Ed notes (“the classic zero doppler target is one which is on a heading that is tangential to the radar antenna beam. Basically, any target that is heading 90 degrees in relation to the antenna beam cannot be detected by its velocity”)

What was your most memorable mission and why?

Gripen_Libya_pic.jpg “Without a doubt the first mission in the Operation Protector over Libya. It was the first time in 50 years that Sweden was abroad with the Air Force in a conflict and I had the opportunity to lead our first mission into the area. Even though the memories of most of the following missions in the operation have faded, it feels like I remember every minute of that first one, better than any of them. It wasn’t very exciting per-se, and the mission went as planned, but it was uncharted territory psychologically. It was a little extra exciting as I had our squadron commander as my wingman and the mission could not fail, for many reasons, both military and political. It started with a very exciting air refuelling were we had to connect right after take-off due to fuel incompatibilities on the Sigonella base (don’t ask..). The bingo fuel warning alarm went off almost right away and creative manual calculations had to take its place. There were a few refuelling misses involved, the Air Force Chief looking back at us from the tanker, which was a C-130 that was really just a trainer, and me having to do a few short cuts through the Fighter Area of Responsibility to get on station on time and with enough fuel. But other than that, quite uneventful as we were just doing Defensive Counter Air for the tanker fleet. Psychologically it turns out that live missions are very similar to training ones, even pulse wise, but I didn’t know that before taking off. Train as you fight works.”

Would you have been confident going against Flankers?

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“Yes. Going up against Flankers is a very probable and much trained for scenario, given where Sweden is geographically. We’ll do great. One-versus-One air combat manoeuvring  is not how we expect to meet them though. A more likely scenario is large force operations/combined air operations where there’s a lot of aircraft in the area — and the chess game is on with beyond visual range combat in a complicated environment. in this situation achieving Situational Awareness is key to success in denying heavy enemy strike access to our airspace. Flankers are a hybrid of figure and speed skaters. Great for acrobatics, pirouettes and pure speed, but we expect the fight will be more like ice hockey, and we have the best all-round players for that. Throw in great team cooperation with reliable and fast fighter links, and I become even more confident. I guess the Flankers would want to make the battlefield as chaotic as possible so we can’t cooperate and keep our lines. That’s usually what you want when doing offensive operations against a organised defender. I also think they will come in great numbers, trying to saturate our defences and fewer resources. Our answer to that is staying organised, having many options to land for a quick turnaround (we have road bases, though not nearly as many as before) and practice keeping situational awareness in a chaotic environment.

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Gripen C/D+ has great missiles, maybe the best in the world with our integrated Meteor and IRIS-T, so if we can get a lock on then and can be at the right place at the right time, BVR duels shouldn’t be much of a problem. The Flankers have better weapons coming though (e.g. K77M), and our missile advantage might go away, but that’s how this very material sport works. Development is not static though and the Russians are putting a lot of effort into their modernisation and re-arming programme, while Sweden are lagging behind in spending.”

Which three words would you use to describe the Gripen? Well-balanced, cost-effective and future-proof.

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gripens

Which fighter aircraft will Switzerland choose?

 

Hornet

Switzerland is a small landlocked nation with powerful neighbours. It has not fought since its civil war of 1847, and has not fought a foreign nation since 1815. Today the neutral nation defends its sovereignty with a small air force of frontline F/A-18s supported by F-5Es. It now seeks to replace both — and an evaluation of five candidates has begun. 

Five fighter types are being pitted against each to compete for a lucrative order for 30-40 aircraft for the Swiss Air Force. From Europe, the Eurofighter Typhoon and Dassault Rafale and the Saab Gripen E; from the US — the Boeing F/A-18E/F Super Hornet, and the Lockheed Martin F-35A Lightning II.

Switzerland selected the Gripen E/F for its fighter needs following an evaluation against the Typhoon and Rafale in 2008. According to a leaked section of the evaluation report, the Rafale had done very well in this evaluation, Typhoon had proved mediocre and Gripen (the C/D rather than then unbuilt E/F was tested) unsatisfactory in several key areas. Despite this, the Gripen was seen as cost effective, and it was hoped that the  upcoming E/F variant would rectify most of the C/D’s shortcomings. The Gripen purchase was a big deal for a small nation, and as has been the case in the past (like the Hornet deal of 1993) was subject to a nationwide vote. The 22-aircraft Gripen contract was rejected by 53.4% of voters in 2014. At least $3.5 billion was expected to be saved, a figure the Swiss people thought better spent on education and social security. The result was interesting, “It is the first time that the left, who had challenged a parliament decision to a nationwide vote, has been successful in a military issue” according to Ppolitical analyst Claude Longchamp in a Swiss Info article. The new purchase will be dependent on a second referendum in 2020.

Who will win the fighter deal? 

F35-comp-5a

To assess the most likely candidate we need to understand a little about the Swiss Air Force and their concept of operations (abbreviated as CONOPS). The Swiss CONOPS prioritises local air policing, against the possibility of a high-end threat, to protect Swiss Neutrality. Their basing model involves hardened and dispersed airfields.

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Historically they have not been shy to pay for high-end capability. They’ve tended to go for expensive and complex systems in the past, notably getting the Falcon missile integrated onto the Mirage IIIS, and adding Electronic Counter Measures and Radar Warning Receivers to the normally austerely equipped Hawker Hunter. More recently they chose the McDonnell Douglas F-18 Hornet over the F-16 because of its radar/weapon combination. They make long-term investments in their aircraft (their Hunters served until 1994 and their F-5Es are still operational) so choose mature but modern systems. They prioritise credible and survivable options, and can afford them when needed. They also dropped any air-ground tasking a few years ago. That means aircraft optimised or compromised by air-to-ground performance are at a disadvantage. That’s a big factor with the F/A-18E, and to a lesser extent with Rafale. The F/A-18E’s big advantage of commonality with its forebear, the legacy Hornet, may not be as tempting as it first seems as the older fleet will be completely withdrawn – though familiarity and a good reputation could help its case. Typhoon is the most capable option in pure air-to-air performance, and unlike the earlier evaluation, AESA radar should be available from the outset – an option Switzerland would be likely to go for. But Typhoon is expensive to purchase and operate. The choice between Rafale and Typhoon revolves around a mixture of cost and how much air-to-air performance is required. Typhoon has a premium performance at a price (though investigations in India have highlighted that the oft-quoted price advantage of Rafale may not be all it seems). The Rafale is a capable aircraft that could serve Switzerland well, but is probably more capable and costly than is necessary.

Switzerland is likely to be more tempted by the later model Gripen, particularly if initial cost is an issue. The MBDA Meteor long-range missile should prove a desirable item and could make a big difference. Today Meteor is operational with Typhoon and Gripen, with Rafale service imminent.

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Switzerland’s defensive posture is about credible deterrence in the situation of a European War — and avoiding being a transit zone for others. The Swiss Government is not happy when NATO assets take short-cuts through their airspace, as sometimes happened during conflict in the Balkans. A fast-climbing fighter with good readiness and availability is vital if the SwAF wishes to deter such intrusions.

The Swiss military is also mindful of Russian influence in subverting politics in parts of Eastern Europe, and they’re wary. The perceived high-end threat threat is thus likely to be a ‘Flanker’ derivative with a long-range BVR weapon. This puts the Super Hornet in the outsider position, mostly down to it being the poorest air-to-air performer, and the oldest technology airframe. The reach of an air-to-air missile is closely tied to the specific excess power (SEP) of the platform in the supersonic manoeuvre when launching, a good sustained turn rate is also vital. The Super Hornet has less SEP at higher Mach than the original and a poor STR compared to its rivals.

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Though the rapid integration of the US Navy’s new BVR missile, probably a large weapon optimised for the Super Hornet could offset the F/A-18E/F’s disadvantage to some extent, this depends on a degree of faith in the development timescale and availability (to a non -priority export nation) of the weapon. This project, rumoured to be progressing well, is currently veiled in secrecy.

Which leaves the F-35A. The aircraft scores highly for situational awareness (SA) and offensive survivability, but is optimised for ground attack and is probably the hardest aircraft to maintain. It has so far had very low readiness rates, a large issue for a small nation wishing to maintain a Quick Reaction Alert force.

It will also not be as easy to deploy as the Gripen E/F. At this stage in time, Gripen E/F seems both the best fit and the likely choice while, probably, being cheaper than the alternatives.

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Sadly, we are way behind our funding targets. This site is entirely funded by donations from people like you. We have no pay wall, adverts (any adverts you see on this page are not from us) or subscription and want to keep it that way– please donate here to keep this site going.

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Revealed: US admits to existence of top secret Mach 6 RS-85 ‘Aurora’ spy-plane

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An artist’s impression of the aircraft.

The United States Air Force operated a “manned strategic reconnaissance aircraft” from 1993 to 2018 according to a press release issued by the Department of Defense today. The type operated under a veil of the strictest secrecy but today its existence was confirmed. 

The Department of Defense admitted it had operated “the fastest aircraft in the world”, to snoop on foreign nations since 1993. Long rumoured in aerospace journalism circles, the aircraft has been described in today’s press release as a “manned strategic reconnaissance aircraft powered by a variable-cycle ramjet capable of operating at speeds and altitudes unobtainable by other aircraft.” This remarkable revelation has raised more questions than answers, including whether the programme has been completely shut down. The release noted, “the aircraft had a top speed exceeding mach 6 and utilized advanced sensors. We can also confirm that it used visual and infra-red light spectrum low observable technology.“—  in layman’s terms a degree of actual invisibility to the human eye or sensors that use light, a technology in its infancy — and until now unknown outside of laboratories.  According to Pentagon spokesperson Luke Mentira, “The type was known as the RS-85 which grew from Project DOLOS in the early 1980s. Its declassification is following its withdrawal from service.” A public reveal of the appearance of the aircraft is expected this week. According to Mentira, “..it looks quite unlike anything else flying and incorporates a high degree of on-wing mission adaptiveness” without qualifying what this meant specifically.

According to long-time aviation researcher and ‘Black projects’ expert Bob Valeta, “This is the most exciting news in the field of aerospace technology that I have ever witnessed – the scope of keeping this classified for so long is mind-boggling. The technologies mentioned are far in advance of anything we guessed at. I am truly amazed.”

Here to read about the 10 Worst Soviet Aircraft. 

The type replaced the Lockheed SR-71 Blackbird in the 1990s, an aircraft capable of speeds at over three times the speed of sound. Until now there has been no official acknowledgment of the RS-85 DOLOS. It is believed that Project DOLOS was an extension of Project Aurora, a 1980s military programme that was accidentally mentioned in a budget report, leading to guesses (now proved correct) of a hypersonic spy-plane.

Of the five retired airframes, one has been earmarked for public display at National Museum of the United States Air Force in Dayton, Ohio “..in the 2020 timeframe.

Click here to read ‘Russia reveals wreckage of US Blackbird spyplane shot down in 1983’

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We have shared more content than ever this month (have a look) and want to maintain this pace.

Thank you. 

The Lippisch P 13: supersonic wonder plane or nazi ‘coke-head’? An assessment by former British technical liaison

 

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Jim Smith had significant technical roles in the development of the UK’s leading military aviation programmes. From ASRAAM and Nimrod, to the JSF and Eurofighter Typhoon. In his life he has provided technical assessments of the YF-22 and YF-23, we wondered what he would make of the Lippisch P 13, an exceptionally ambitious wartime concept for a supersonic interceptor of bizarre appearance powered by a coal-fuelled ramjet.

“Hush-Kit has asked me for an assessment of the extraordinary Lippisch L13a. A bold and innovative concept, which, although it did not get to fly, was wind tunnel tested, and was also trialled in glider form. Before I give my thoughts on the aircraft I’ll start by quoting verbatim the Wikipedia entry:

 

"(https://en.wikipedia.org/wiki/Lippisch_P.13a):
Lippisch P.13a
From Wikipedia, 

Lippisch P.13a

Model of Lippisch P13a at the Technik Museum Speyer
Role Interceptor
Designer Lippisch
Status Project
Number built 0
Developed from Lippisch DM-1
The Lippisch P.13a was an experimental ramjet-powered delta wing interceptor aircraft designed in late 1944 by Dr. Alexander Lippisch for Nazi Germany. The aircraft never made it past the drawing board, but testing of wind-tunnel models in the DVL high-speed wind tunnel showed that the design had extraordinary stability into the Mach 2.6 range.[1]

Contents
Design and development[edit]
As conventional fuels were in extremely short supply by late 1944, Lippisch proposed that the P.13a be powered by coal. Initially, it was proposed that a wire-mesh basket holding coal be mounted behind a nose air intake, protruding slightly into the airflow and ignited by a gas burner. Following wind-tunnel testing of the ramjet and the coal basket, modifications were incorporated to provide more efficient combustion.
The coal was to take the form of small granules instead of irregular lumps, to produce a controlled and even burn, and the basket was altered to a mesh drum revolving on a vertical axis at 60 rpm. A jet of flame from tanks of bottled gas would fire into the basket once the P.13a had reached operating speed (above 320 km/h), whether by using a rocket to assist takeoff or by being towed.
The air passing through the ramjet would take the fumes from the burning coal towards the rear where they would mix under high pressure with clean air taken from a separate intake. The resulting mixture of gas would then be directed out through a rear nozzle to provide thrust. A burner and drum were built and tested successfully in Vienna by the design team before the end of the war.
It is not known what armament would have been carried by the P.13a; the MK 103 cannon would have been too heavy and large for such a small aircraft and it is possible that one or two large-calibre machineguns would have been used.
At the end of the war even the prototype DM-1 test glider had not been finished when it was captured by American forces. The Americans ordered Lippisch's team to complete the glider, and it was then shipped to the United States where it was test-flown. According to the National Advisory Committee for Aeronautics the results were positive[2] and lessons learned were incorporated into NASA's research aircraft of the 1950s and on.
Film footage exists which shows a gliding test of a scaled-down model of the P.13a. These tests began in May 1944 at Spitzerberg, near Vienna.[3]
Variants
• Akaflieg Darmstadt/Akaflieg München DM.1 - AKA Lippisch DM.1 A scale flying wind tunnel glider version of the proposed Lippisch P.13a
• Lippisch P.13b - a further development of the P.13a, which never came beyond the drawing board.
The P.13a was completely unrelated to the 1942 project for a high-speed bomber aircraft, but similarly named P.13.
Specifications (P.13a, as designed)
General characteristics
• Crew: one
• Length: 6.70 m (22 ft 0 in)
• Wingspan: 6.00 m (19 ft 9 in)
• Height: 3.25 m (10 ft 8 in)
• Wing area: 20.0 m² (215 ft²)
• Loaded weight: 2,295 kg (5,060 lb)
• Powerplant: 1 × Kronach Lorin coal-burning ramjet

Performance
• Maximum speed: 1,650 km/h (1,025 mph)
• Range: 1,000 km (621 miles)
• Wing loading: 115 kg/m² (24 lb/ft²)" 


The configuration, propulsion system, and claimed performance are all of note, as is the fact that a glider version is known to have been tested. The maximum speed quoted was probably first exceeded by the Fairey Delta 2*, which established a world speed record of 1132 mph on 10 March 1956, just over 63 years ago, and 12 years after the DM 1 glider trials supporting the L 13a program.

(*editor notes: the Bell X-1A appears to have done this earlier, but this was air-launched)

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The British Fairey Delta 2 was the first ground-launched aircraft to exceed 1,000 mph in level flight. (credit: author)

Other similar aircraft

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The adorable Turbomeca Palas.

The aircraft which perhaps most closely resembles the Lippisch in configuration is the Payen Delta, an example of which is to be found in the Musee de L’Air in Paris. This flew successfully, powered by a Turbomeca Palas engine of only 330 lb thrust. Projected developments included a jet trainer, the P 56 Jockey, to have been powered by a 1640 lb thrust Viper engine.

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Another little-known French aircraft of similar configuration, the Gerfaut, was the first European jet aircraft to exceed the speed of sound in level flight, and did so without the use of an afterburner. It too was intended to be developed with the use of an afterburning ATAR 101C engine.

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The aircraft which perhaps most closely resembles the Lippisch in configuration is the Payen Delta, an example of which is to be found in the Musee de L’Air in Paris.

The Fairey Delta 1 was originally designed as a vertical take-off fighter (!), but was modified to become a delta-wing research aircraft, first flying in 1951.

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A small aircraft, with a wing span of only 19.5 ft, rivalling the tiny Payen Delta’s 17 ft and quite similar in size to the P 13a. For comparison, the Chipmunk, which I used to enjoy flying, has a wingspan of 31 ft.

Boulton-Paul P111

Boulton Paul P111 (credit: author)

The Boulton Paul P111 was built to investigate the delta wing in transonic flight. Powered by a Nene turbojet of 5100 lb thrust, it was just subsonic in level flight, and able to reach supersonic speeds in a shallow dive.

The XF-92A was the pre-cursor to the F-102 Delta Dart, and in many ways resembles a turbo-jet powered P 13a. A larger aircraft, with a span of 31 ft, it first flew with an Allison J33 with 5400 lb max thrust, but even when fitted with an afterburner and delivering 8200 lb thrust, its maximum speed was Mach 0.95.

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As part of Operation Paperclip and similar efforts, Alexander Lippisch‘s DM1 research glider had been completed and shipped to the National Advisory Committee for Aeronautics (NACA) Langley Research Center,

Assessment of the P 13a

How to assess the bold and innovative Lippisch P 13a? Readers who have seen my earlier discussion of fictional aircraft (the F-19, Firefox and Stingbat) will be aware that I am prepared to take a pretty open-minded view about the most radical configurations. In the case of the little P 13a, it seems to me necessary to look at the following aspects: propulsion; configuration; stability & control, and performance, and through examining these aspects seek to form a rounded view of the design.

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Propulsion

This is the most challenging area to assess. Whoever heard of a coke-burning ramjet propulsion system for a supersonic aircraft? Well, we must not just reject the unfamiliar out of hand. After all, the Germans had a long history of highly innovative piston engines, had by this time flown both jet and rocket-powered manned aircraft, had deployed operationally a cruise missile powered by a gasoline burning pulse jet, and had fielded an operational liquid-fuelled tactical ballistic missile, the V2.

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To get a feel for the plausibility of a carbon-pellet-burning and natural-gas-initiated ramjet, I checked out the energy-density that might be available. For natural gas, this is about 10% better than gasoline, and for coal around 25% worse. In the system as a whole, the ramjet is likely to be lighter than a turbojet, but this will be offset by pressure storage for the gas, and the rotating drum and storage for the carbon pellets. Apart from a general conclusion that the thermodynamics of propulsion systems should be left to the experts, my overall feeling was that a functioning system might be achieved.

For the moment, in the spirit of exploring the P 13a further, I will assume a viable propulsion system exists. This is a tried and tested way of assessing systems with new technologies. One simply assumes that the technology will work as advertised, and you are then assessing the best possible outcome.

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Of the similar aircraft considered above, it is worth noting that the Fairey Delta 2, considerably larger than the Lippisch, requires an Avon engine with 10,000 lb thrust, and the F-102, capable of 825 mph, required 17,200 lb thrust. To achieve a similar thrust to weight ratio to the Fairey Delta 2, the P 13a would require a thrust of about 3750 lb.

At the tropopause, Mach 1 is about 660 mph, and the claimed max speed of the P 13a at the tropopause would be equivalent to Mach 1.55, just in the acceptable range for the simple pitot intake shown.

Configuration

From the perspective of a concept looking to achieve a design speed of around 1000 mph, or Mach 1.55, drag for this design is going to be a significant problem. There are two main issues: firstly, the wing thickness-to-chord ratio appears far to high to achieve supersonic flight, let alone 1000 mph; and secondly, the configuration was clearly designed when the understanding of wave drag was in its infancy.

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RT Jones

The XF-92A revealed the consequences of a failure to understand wave drag all too clearly. The designers had access not only to trials of the DM-1 glider, but to Lippisch himself, and to wind tunnel test data from NASA Langley showing the DM-1/P 13a wing thickness was too large, and would generate high transonic drag. Flight test revealed the inability of the XF-92A to fly at supersonic speeds, even with the installation of a more powerful engine.

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R T Whitcomb of NACA Langley

The resolution of this problem was the discovery and articulation of the Area Rule by R T Whitcomb and R T Jones at NACA Langley and NACA Ames respectively, although the principle had earlier been established by Junkers in Germany. As depicted in the illustration accompanying the Wikipedia article, there is no way this configuration would have been supersonic in level flight.

As indicated in the Wikipedia article, payload-range, and armament in particular, is also a concern. The aircraft is very small indeed, and the quoted range looks a little unlikely. Against the principal threat towards the end of the war – US bombers and their escort fighters, an armament of two machine guns seems unlikely to be an effective weapons capability, despite the claimed high speed of the aircraft.

Stability and Control

F-102 (1).jpg

“Wing leading-edge camber, later applied to the F-102, is likely to have both improved high speed stability and reduced drag.”

DVL wind tunnel tests are cited as showing stability of the design up to Mach 2.76. These results would have been regarded as plausible at the time because German capability in supersonic wind tunnel testing was world-leading at the time. However, even were these results to be accurate, transonic testing would be required to reveal the large increase in wave drag which, in my view, would limit the design to subsonic flight.

US testing of the XF-92A showed some good qualities, particularly the relatively slow approach and landing speeds made possible by the leading-edge vortices formed over the wings at high incidence and low speed. A transonic pitch up issue, leading to loads of 6 to 8 g was discovered, as well as the use of wing fences as a means of flow control which made this problem manageable. Wing leading-edge camber, later applied to the F-102, is likely to have both improved high speed stability and reduced drag.

Powered flying controls had been discovered by the US to be necessary to control aircraft in the transonic reason. These are likely to have been fitted to the XF-92A, and were certainly fitted to the F-102, but this need had almost certainly not been identified by the designers of the Lippisch P 13a.

Performance

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A reproduction at the aviation museum in Pungo, Virginia (Thom McCaughey)

As shown in the Wikipedia article, it seems clear the Lippisch P 13a would be very unlikely to be supersonic in level flight. Although I cannot pretend to have a deep understanding of the carbon and gas fuelled ramjet, it seems to me similarly unlikely that the claimed range of 1000 km/621 miles could have been achieved, mainly because of the extremely small size of the airframe.

The development history of the DM-1 –  XF-92A – YF-102 – F-102A  series shows conclusively that a thinner, more sophisticated wing, incorporating leading edge camber, and the application of a coke-bottle (pun intended) fuselage incorporating lessons learned from the Whitcomb/Jones Area Rule would be required to attain anywhere near the claimed speeds.

Overall Assessment

Much to my regret, I have to find the Lippisch P 13a, as the Mythbusters TV program would have said, “Busted”, or at least “very implausible”. The claimed performance could not have been achieved, and the weapons carried were likely to prove ineffective. The claimed supersonic stability is not relevant because it is unlikely those speeds could be reached.

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In addition, the domains of wave drag, transonic pitch up, and roll-yaw coupling were unknown and therefore unaddressed. These issues were encountered in the XF-92A and YF-102 and eventually resolved in the F102A.

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Red Dawn: Why I flew a Soviet Mi-24 ‘Hind’ gunship helicopter over Texas

Me in Mi-24_Skip Robinson Photo

Who are you — and what is your relationship with helicopters?

“I’m an editor with the helicopter industry magazine Vertical, which means I spend an inordinate amount of time writing and thinking about helicopters. I also fly them, although not as regularly these days as I would like! I hold FAA commercial pilot and flight instructor certificates with helicopter and instrument ratings, and have also held commercial helicopter pilot licenses in Canada and Australia.”

Which types have you flown?

“Most of my flight time is in Robinson R22s and R44s, since I learned to fly in Robinsons and spent about 800 hours instructing in them. I also have a fair amount of time in the Airbus AS350 series, the Bell 407, and various Bell mediums (UH-1B/H, Bell 205 and 412).

Then I’m lucky enough to have anywhere from 30 minutes to 20 hours in another 20 different helicopter types, ranging from the two-seat Guimbal Cabri G2 to the mighty Columbia Model 234 Chinook, which I flew as co-pilot on a powerline construction job for one of my more interesting story assignments.

For anyone who’s curious about the other 18 models, they are the Airbus EC120, EC155, and H215; Bell 206B, 206L, 505, and AH-1F; Enstrom 480B; Kaman HH-43 Huskie and K-1200 K-MAX; Leonardo AW139; MBB Bo.105; MD 500 and 902; Mil Mi-24D; Robinson R66; Schweizer 300; and Sikorsky S-55. I’ve flown simulators of a few other aircraft, but maybe the only one worth mentioning is the AW609 tiltrotor.”

What is your favourite helicopter, and why? 

KMAX long line

“I have to say the K-MAX, which is a single-seat heavy-lift helicopter with twin intermeshing main rotors that eliminate the need for a tail rotor. It’s not the most attractive helicopter (it has been described as two broomsticks, um, copulating in a dumpster) and neither is it the most modern (its rotor blades are actually made out of wood). But I’ve been fascinated by it since I first saw one landing on a fire helibase in 2005.

The single seat means that your first flight in the aircraft is also a solo, which is a little intimidating, especially since the intermeshing rotor system gives it somewhat different handling characteristics than a conventional helicopter. But Kaman prepares you pretty well for this by first giving you around five hours of dual flight instruction in the HH-43 Huskie, which has a similar rotor design. Getting to fly a K-MAX in 2014 was a huge thrill, and I was also the first woman to fly the model. It tells you something about the helicopter industry that it took 20 years from the certification date of the aircraft to reach that milestone, but better late than never.”

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What is your opinion of the S-97?

“The compound helicopter that Sikorsky is pitching as the U.S. Army’s Future Attack Reconnaissance Aircraft? It still has a long way to go to prove itself, and it remains to be seen how it will stack up against the competition, but generally speaking I’m a total fangirl.

In particular, I’m really excited about the potential for the rear-mounted pusher propulsor to completely transform the way we fly — for example, by permitting rapid accelerations or decelerations in a level altitude, or the ability to maintain a stationary hover while pointing your nose to look up or down. These are revolutionary capabilities that go against everything that helicopter pilots today understand instinctively about how to fly. If anyone from Sikorsky is reading this, I hope they decide I’m the perfect person to write a pilot report on it.”

Please tell us about your experience with the Mi-24?

Mi-24_Skip Robinson Photo

Sure. The Mi-24 — the fearsome Russian attack helicopter — isn’t something that those of us in the U.S. see very often, but in 2017 I had the opportunity to fly a privately owned Mi-24D in Lancaster, Texas, for a story. It’s one of three owned by the same person, two of which are operational and also available to the U.S. military for adversary orientation training.

Whenever I have a chance, I try to learn as much as possible about an aircraft before I jump in and fly it, even if it’s only for a short demo. Generally speaking, all helicopters have been designed to present a common flight control architecture to the pilot, so without understanding the underlying systems, it’s hard to render any judgment more meaningful than “Yep, flies like a helicopter.”

Mi-24 CPG_Skip Robinson Photo

In this case, I was able to get my hands on a couple of different versions of the Mi-24D flight manual, and I spent a few weeks before my flight studying up on it. I did a double take when I read that prior to engine start-up the throttle (which is a twist grip like a motorcycle throttle) should be closed full left, away from the pilot — so, similar to a motorcycle throttle, but exactly opposite to the throttle in Western helicopters.

Now, there are also some differences with the pedals in the Hind compared to U.S.-designed helicopters, due to the different rotational direction of their main rotors. So in the Mi-24, which has a clockwise-rotating main rotor system, right pedal increases tail rotor thrust, whereas in something like a Huey, the left pedal is the power pedal. But many Airbus helicopters also have a clockwise-spinning main rotor system and right power pedal, and it’s really not a big deal. Right pedal still points the nose to the right, and left pedal points the nose to the left, so if you happen to input the wrong pedal, you’ll notice and instinctively correct, as long as you’re flying smoothly.

However, in certain circumstances, if you were to inadvertently roll the throttle in the wrong direction, you could potentially hurt yourself or the aircraft before you had a chance to recover. So that really caught my attention!

On the day of my flight, my instructor pilot, John Totty, put me through an abbreviated version of the adversary orientation training that he provides to the U.S. military. This was really interesting, because it took that understanding of aircraft systems to the level of tactical application. So, for example, the Mi-24D’s stub wings make it very fast, but also limit its banking ability. If you were facing off against the Hind in a slower but more manoeuvrable helicopter, how could you exploit this to your advantage? I ended our class feeling much more prepared for a Red Dawn scenario.

We combined my demo flight with an air-to-air photo shoot with the other Mi-24D and two R44 camera ships. I rode in the co-pilot/gunner compartment up front, and during our photo shoot there wasn’t much for me to do except marvel that I was flying in a Hind over Texas! Talk about Red Dawn.

Then we broke off to give me a chance to fly the aircraft. The Mi-24D isn’t meant to be flown from the front; the co-pilot/gunner has only basic flight instruments to allow them to make it home in an emergency. Also, the co-pilot’s flight controls are generally stowed: the cyclic is tucked forward, and the pedals are hidden in the sides of the compartment. The controls move into position through hydraulic pressure after the co-pilot squeezes a lever on the collective. Since they’re not designed for routine use, they’re not very ergonomic! So I can’t say it was a very comfortable flight, but I loved every minute of it. And yes, it flies like a helicopter.”

Tell us a little bit about Vertical

“Vertical is still a traditional print magazine — we publish six issues per year, plus four issues of a sister magazine, Vertical 911 (which focuses on the para-public and military sectors). But our online presence has certainly grown enormously since I joined the magazine 10 years ago. We cover all aspects of the civil helicopter industry plus military helicopter operations; so, we’re less interested in the minutiae of the defence industry than in how helicopters are being used in various theatres. That has afforded me some incredible reporting opportunities as well: I’ve been to Afghanistan a couple of times and recently embedded with the Royal Canadian Air Force in Mali.

We’re also really active on social media. All of us editors share tweeting duties, but I handle most of our posts on Facebook and Instagram. Like most people, I have a love-hate relationship with social media, but on balance it’s been a fantastic way for us to connect and share with rotorheads all over the world. Helicopters are involved with an amazing diversity of operations, and social media is a great way to showcase that.”

If you had to choose the ten most important helicopters in history, what would they be and why? 

Wow, tough question. I don’t think there’s any Top 10 list that everyone will agree with, but here’s my stab at it in reverse chronological order by year of first flight (in parentheses).

10. Robinson R22 (1975): the two-seat piston engine model that made helicopter flight training relatively affordable, opening the industry to a wider range of pilots, myself included.

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9. Sikorsky UH-60 Black Hawk (1974): the bestselling successor to the Huey, which embodied a new emphasis on crashworthiness and survivability.

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8. Aérospatiale AS350 (1974): the hugely versatile, bestselling successor to the Alouette series (which did not embody an emphasis on crashworthiness, unfortunately).

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7. Boeing CH-47/Model 234 Chinook (1961): the most successful tandem-rotor helicopter, which continues to have important military and civilian applications.

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6. Mil Mi-8 (1961): the world’s most-produced helicopter, with all of the far-reaching, wide-ranging impacts that implies.

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5. Bell UH-1 Huey (1956): the iconic helicopter of the Vietnam War, which created a generation of pilots and mechanics who would shape the industry for decades to come.

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4. Sud Aviation Alouette II (1955): the first production helicopter to be powered by a gas turbine engine and one whose derivatives, notably the SA 315B Lama, pioneered high-altitude operations.

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3. Sikorsky H-19/S-55 (1949): a pioneering military transport helicopter that helped define air mobility, medevac, and search-and-rescue operations.

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2. Bell 47 (1945): the first helicopter certified for civilian use, and consequently essential to the development of the civil helicopter industry.

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Vought-Sikorsky VS-300 (1940): Igor Sikorsky’s first practical helicopter, and the one that established the single main rotor and tail rotor configuration that has dominated the industry since.8-2.jpg

What is the future of rotorcraft technology

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“I foresee a bifurcation of the industry. On the high end, new designs like the Bell V-280, Sikorsky S-97 and SB-download.jpg1, and Airbus Racer will deliver incredible speed and performance to military and other customers who have the need and the budget for them. Meanwhile, I expect that cost-effective electric VTOL aircraft will take over many missions, like passenger transport, that are currently being performed by light helicopters. There will still be a market for conventional helicopters, but it will be squeezed at both ends.

 

Autonomy will undoubtedly be a big part of our future, too. As someone who spends a lot of time writing about the tragic consequences of human error in helicopters, I don’t think this is a bad thing. But getting to the point where vertical-lift aircraft are routinely flying themselves in congested airspace is going to be hugely challenging. New autonomous systems are going to introduce new failure modes that may be difficult to anticipate, and as the recent 737 MAX crashes illustrate, human pilots don’t have a great track record of compensating for failures in complex systems that are largely opaque to them. There are a lot of smart people working on this problem, but they have a lot of hurdles to overcome.”

What advice would you give to new helicopter pilots?

“Well, if they haven’t already entered the helicopter industry, I would advise them to think long and hard before doing so. The civil helicopter industry in particular is not generally conducive to healthy relationships or work-life balance. Part of this is a necessary consequence of the unique work that helicopters do in hard-to-reach places. However, the industry also has a long history of taking advantage of people’s passion — flying helicopters is incredibly addictive, and there is always someone who is willing to put up with almost anything for the chance to do it.

But if you’re absolutely committed to being a helicopter pilot, then my advice is to constantly be looking to expand your horizons. There’s a tremendous amount of knowledge and talent in the helicopter industry, but it’s largely siloed. For example, depending on where you train and begin your career, you may really need to go out of your way to find instructors who are skilled in mountain flying. It’s worth seeking them out! Every new skill you pick up, every new perspective you expose yourself to will make you a better pilot, and along the way you’re likely to make connections that will open doors for you down the road. This curiosity should extend to every mechanical system on your aircraft, too, because the more you understand about how your helicopter works, the better position you’ll be in to keep yourself safe.”

What is the greatest myth about helicopters?

Predator

“A lot of people still seem to believe that helicopters can’t glide if they have a power failure. In fact they can in a manoeuvre called an autorotation, although the glide path is closer to, say, a turkey’s than an eagle’s. In an autorotation, air flowing upward through the rotor system drives the rotor blades, and the pilot maintains full controllability, as long as the helicopter continues to go generally down. It’s something that helicopter pilots practice extensively during their training, although the success of the manoeuvre in real life depends on a lot of different factors, including what you happen to be flying over when your engine quits. The one advantage that helicopters have over airplanes in this respect is that they don’t need as much real estate for a safe emergency landing.”

Tell me something I don’t know about them.

“How about the origin of the word helicopter? It’s derived from the Greek words helikos (spiral) and pteron (wing). Of course, the impulse of English speakers today is to divide it into “heli” and “copter,” which masks that etymology.”

What do you think about the way helicopters are portrayed in movies

Helicopters white house down

They do seem to explode with uncommon regularity, don’t they? Pretty much anytime a CGI team gets involved with a helicopter sequence, they ruin it for me. I’ve been on the sets of a couple of big-budget action movies, and the actual flying that goes on there is so much more compelling to me than the video game version that makes it into theatres. Movies also give the impression that around 80 percent of the civil helicopter industry is devoted to supporting super villains. This is not actually the case — which is perhaps unfortunate, because I would have so many amazing stories to write if it were.”

What should I have asked you? 

“I think it’s worth mentioning how I became a helicopter pilot. Basically, I was working as a luxury travel writer when I went for my first helicopter ride while on assignment in British Columbia in 2004. The experience was so thrilling that I immediately went home and signed up for lessons. Aviation can feel like a exclusive club, but I think there are all kinds of people who would discover a similar passion given the right exposure to it. I’m proof that you don’t need to be an avgeek from childhood to find success in the industry. Of all of the futures I imagined for myself while growing up in rural New Mexico, someday flying a Russian attack helicopter never remotely crossed my mind. Yet, here I am. Pretty cool, huh?”

 

Elan Head is a helicopter pilot and special projects editor for Vertical, a North American-based magazine covering the helicopter industry.

(Mi-24 photographs: Skip Robinson)

More on her Mi-24 and K-MAX adventures.

 

Sadly, we are way behind our funding targets. This site is entirely funded by donations from people like you. We have no pay wall, adverts (any adverts you see on this page are not from us) or subscription and want to keep it that way– please donate here to keep this site going.

We have shared more content than ever this month and want to maintain this pace.

Thank you. Me in Mi-24_Skip Robinson PhotoMi-24_Skip Robinson Photo