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)

Other similar aircraft

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.

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.

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.

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.

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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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.

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.

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.

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.

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.

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

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

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.

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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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?  “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.” 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? 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.” 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.”

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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. 9. Sikorsky UH-60 Black Hawk (1974): the bestselling successor to the Huey, which embodied a new emphasis on crashworthiness and survivability. 8. Aérospatiale AS350 (1974): the hugely versatile, bestselling successor to the Alouette series (which did not embody an emphasis on crashworthiness, unfortunately). 7. Boeing CH-47/Model 234 Chinook (1961): the most successful tandem-rotor helicopter, which continues to have important military and civilian applications. 6. Mil Mi-8 (1961): the world’s most-produced helicopter, with all of the far-reaching, wide-ranging impacts that implies. 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. 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. 3. Sikorsky H-19/S-55 (1949): a pioneering military transport helicopter that helped define air mobility, medevac, and search-and-rescue operations. 2. Bell 47 (1945): the first helicopter certified for civilian use, and consequently essential to the development of the civil helicopter industry. 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. What is the future of rotorcraft technology?  “I foresee a bifurcation of the industry. On the high end, new designs like the Bell V-280, Sikorsky S-97 and SB-1, 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? “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?  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.

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In the midst of a chaotic possible withdraw from Europe, the UK has inked a deal worth almost $2 billion for five US-built E-7 airborne early warning aircraft. According to one former RAF Commander we spoke to it is the wrong deal at the wrong time.  Rumours had persisted since July 2018 that the UK was going to acquire E-7s, and this week it was confirmed. Five E-7s have been ordered and are expected to replace the RAF’s vintage E-3Ds from the early 2020s. The Royal Air Force ordered seven E-3D airborne early warning and control back aircraft in 1987 which replaced the woefully archaic Shackleton AEW.2s (essentially World War II bombers fitted with a radar that entered service on Avenger torpedo bombers in 1946). That Shackletons, a type that struggled to reach 300mph, were asked to survive in airspace chock-full of MiG-31s and Su-27s says much about how the RAF has historically neglected the AEW&C role. Today five E-3Ds remain in service; four are in frontline service and one is used for training, the other two were withdrawn this month. The E-3Ds are obsolete;  Justin Bronk, Royal United Services Institute (RUSI)’s Research Fellow for Airpower and Technology, noted in 2018, “… the E-3, even in modernised form, is no longer a cutting-edge ABM(anti ballistic missile) &S system in a world where proliferating long-range missile systems and emerging non-Western low-observable fighters can force it to stay hundreds of kilometres from contested airspace, placing a higher premium on BLOS (Beyond Line-Of-Sigh) communications capacity rather than onboard sensors…Even when it is able to operate closer to the battlespace, the AN/APY-1/2 mechanically scanned radar array common to all E-3s has significant inherent limitations in terms of its ability to detect low-observable, very slow moving and hypersonic threats, unlike more modern AESA-equipped AWACS types already in service with the US Navy and various air forces around the world. “

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Coming soon: the case for the RAF E-7s

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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When the F-15 Eagle entered production, Nixon was in office. Now, 47 years later, it is still in production, and in 2019 the United States Air Force requested a radically modernised version, the F-15EX. The reason for its longevity? The Eagle can do almost anything that is asked of it.  McDonnell Douglas F-15N Sea Eagle The effort to replace the F-4 Phantom II in US Navy service had been tortuous. The overweight overly-complex F-111B failed, and in the early 70s its successor the nascent F-14 was also struggling. McDonnell Douglas stepped in offering the F-15N, based on their yet-to-fly F-15A. It had much going for it, being a simpler design than the F-14, with better engines. However, adding a heavy naval landing gear, folding wings for deck stowage and the hugely complicated AWG-9/AIM-54 weapon system — an extremely long range radar/missile combo — would have added so much weight and involved so much work it would have mitigated any advantages the Sea Eagle might have enjoyed. McDonnell Douglas then proposed dumping the AN/AWG-9 radar in exchange for a modified version of the Eagle AN/APG-63 radar adjusted to work with the Phoenix, but the Navy preferred to soldier on with the Tomcat. Had the Sea Eagle succeeded, Top Gun would have been a film about Eagles. That the Russians and Chinese have subsequently successfully adapted the ‘Flanker’ to carrier life is evidence that the Sea Eagle concept was not crazy. We asked an F-15 pilot how confident he would be going against a Flanker, his answer here:  Streak Eagle  In 1975 the US wanted to show off what the new F-15 could do, so they set about creating an especially fast Eagle to break world records and garner global exposure. Now they didn’t exactly cheat, but the machine — the Streak Eagle — was considerably lighter than an operational aircraft. Every possible act of weight reduction took place — the following were all removed: the flap and speed brake actuators, the M61A1 Vulcan 20-mm cannon and its associated systems, one generator, the radar and fire control systems, most of the cockpit displays — even the radios and the paint! And though special measuring equipment was added the aircraft was still extremely light. It had shed approximately 1,800 pounds (817 kilograms), giving it a monstrous thrust-to-weight ratio of 1.4:1. The Streak Eagle succeeded in shattering a series of world records. F-15 ‘Satellite Killer’ The F-15 is the only fighter to have shot down a satellite, something it did in 1985. The weapon for this test was the ASM-135 ASAT designed to destroy Soviet communications-, spy-  and ‘killer’ satellites. To launch the weapon required the specially modified F-15 to climb to 80,000ft, an extreme altitude unachievable in most other aircraft. The United States Air Force wanted 20 F-15A fighters and 112 missiles for the mission and had begun to modify the fleet when ASAT was axed.  It was cancelled for several reasons, including rising costs, international laws intended to limit space warfare and fears that the destruction of multiple satellites could lead to a belt of orbiting debris that could potentially destroy everything else in orbit.

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The F-15 Short Takeoff and Landing and Maneuver Technology Demonstrator In 1984 McDonnell Douglas was tasked with a creating an experimental aircraft that could “land and take-off from sections of wet, bomb-damaged runway under bad weather conditions and severe crosswinds without active ground-based navigational assistance.”  NASA had been studying the idea of fitting thrust vectoring nozzles to the F-15 since the 1970s, and this new test machine (an adapted F-15B) – fitted with canard foreplanes-  was dubbed the F-15STOL/MTD. It was first flown with the low-observable thrust-vectoring nozzles in 1989 and the results were remarkable, according to NASA, “Test flights demonstrated a 25-percent reduction in takeoff roll, and the thrust-reversing feature made it possible for the F-15 to land on just 1,650 ft of runway… In addition, thrust reversal was used during up-and away flight to produce rapid decelerations—a useful feature for close-in air-to-air combat. During the flight program, the F-15 STOL/MTD made vectored takeoffs with rotation demonstrated at speeds as low as 42 mph. The program ended on August 15, 1991, after accomplishing all of the flight objectives.” Rarely discussed but equally amazing- “The most impressive research results in flight dynamics, however, occurred when the Langley researchers equipped the free-flight model with special 2-D nozzles that provided thrust vectoring in yaw as well as pitch. The superior control provided by the multiaxis vectoring was demonstrated when the model was easily flown at angles of attack up to about 85 deg without vertical-tail surfaces.” ACTIVE  In 1993, the  STOL/MTD left USAF and was acquired by NASA, which renamed it the F-15 ACTIVE (Advanced Control Technology for Integrated VEhicles). NASA used the ACTIVE to test several things, including testing new round 3D thrust vectorers. These could support up to 20 degrees of thrust vectoring in any direction. These nozzles were mounted to stock F100-229 engines and were barely heavier than the standard nozzles. The project bears interesting comparison with the Russian Sukhoi ‘Flankers’ that have entered service with 3D vectored thrust nozzles (some of which also have canard foreplanes).  Later in life, the ACTIVE was used to test the next-generation of flight control systems, with the ‘Terminator-like’ ability to learn and analyse the flight properties of the aircraft. In theory, these would allow a pilot to control the aircraft during an emergency by customising thrust vectoring and control surfaces to compensate for specific unpredicted battle damage. The aircraft would be flying in a way it had not flown before, adapting to conditions as they happened. The aircraft was finally retired on January 30, 2009. During its service it had tested propulsion and flight control systems as well as high altitude sensors and communication equipment. It made a major contribution to advanced tactical fighter research.  Quiet Spike  Supersonic flight is largely banned over land as the ‘sonic boom’ produced by an aircraft breaking the sound barrier is loud and potentially destructive. This –somewhat controversial – limitation severely limited Concorde’s success. Gulfstream Aerospace want to bring back supersonic air travel but believe the only way to do this is to make it quieter. They thus teamed with NASA to work on a way to acoustically shape the sonic booms to reduce the noise. The idea was to shape the shock waves with a huge retractable boom on the nose of an aircraft. To test the plausibility of this, a NASA F-15B was selected modified with the semi-retractable ‘spike’ and flew 50 flights from 2006 to 2007. How well this is worked is unclear: a 2013 statement by Gulfstream noted supersonic air travel was still unlikely unless the boom could be reduced. Two x-planes will continue research in this field – the Gulfstream X-54 and the Lockheed Martin Lockheed Martin X-59 QueSST. F-15 2040C Stealth fighters that must carry their weapons internally, like the F-22, do not have enough missiles to fully exploit their potential. One solution to this is for stealth aircraft to work in conjunction with conventional fighters with large weapon loads. The 2040C, proposed by Boeing in 2017, demonstrates this idea taken to an extreme boasting the ability to carry sixteen air-to-air missiles. The aircraft would communicate to Raptors via the cutely named Talon HATE communications pods. F-15SE Silent Eagle  When Boeing started publicising the F-15 Silent Eagle in 2009 it was considered by many as a joke – a ‘stealthy’ version of the notoriously radar conspicuous F-15 seemed hard to take seriously. As did the idea that adding a ton of RCS measures including canted vertical fins, new electronics, an internal weapons bay, the addition of a great deal of advanced Radar Absorbent Material to an aircraft without a USAF order would actually end up being any cheaper than the F-35 it was supposed to counter on price. The world agreed, and despite some interest from Israel and South Korea (who were scared of its potential cost and preferred a less radical Eagle) – no orders have transpired. The project was not a waste of time though – Boeing’s continued aggressive push of the Eagle resulted in new advanced variants and a very significant order by USAF for the F-15X.

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Tiny, smart and capable, the Swedish Gripen C is a bantamweight fighter aircraft with a big punch. The Gripen E now in development is a bigger aircraft, close in weight to the F-16. We spoke to SAAB test pilot Jonas Jakobsson about flying a machine that emphasises brains over brawn.  Gripen is a fascinating aircraft, lambasted by the Swiss air force evaluation and loved by its pilots and operators, it does things in a different way. Connectivity, situational awareness and other boring sounding concepts are prioritised over power and speed, resulting in a machine that is cheap to operate and capable of delivering nasty surprises to opponents that underestimate it. Though only around 250 Gripens have been built since production begun in 1987 it has earned Saab an excellent reputation as one of the few aircraft manufacturers that stay close to running timely projects on budget (a key reason for Boeing choosing to partner with Saab for its winning T-X trainer). But is its good reputation just another example of Sweden’s slickness in public relations? Over to Jonas Jakobsson. What is your name, rank, unit and hours on Gripen C? “My name is Jonas Jakobsson and I’m a Major (ret.) and currently an experimental test pilot working at SAAB. I’ve flown well over 1000h in Gripen.” Which other aircraft types have you flown? “During air force training I flew Beagle Bulldog (SK61) and SAAB 105 (SK60). My first aircraft as an operational pilot was the strike fighter version of Viggen (AJ-37) which later was upgraded to AJS-37 indicating that it also had recce capability. I’ve also flown Lansen, Draken, and all the other versions of Viggen. During my career as a testpilot I have also flown a number of helicopters, fighters and trainers.” What were you first impressions of the Gripen? “That it was a true pilot’s aircraft. I really felt that handling the aircraft out to the very edge of the allowed envelope was made really easy by the flight control system. The way information was fused and presented was also very intuitive. This has been a hallmark of SAAB aircraft for a long time. I think much due to the fact that Swedish fighters traditionally are single seat. A good Human Machine Interface compensated for the second pilot…” How would you rate the Gripen in the following categories: A. Instantaneous Turn rates B. Sustained turn rates C. Acceleration D. Climb rate E. Range “Without mentioning specific numbers since this would be classified I would like to expand the question a bit. We have built Gripen to achieve the highest possible operational effect in a number of scenarios defined by our customers. To do this we have to balance a number of factors such as platform performance, sensor performance, weapon performance, avionics, Human Machine Interface etc. The classic metaphor stating that a chain isn’t stronger than its weakest link is relevant for fighters as well! So the answer would be; platform performance is as good as or better than what is needed to reach the high overall operational effect demand of a future fighter.” (Though Jonas avoids answering this question directly I would like to quote from this article “Gripen is a bit of an unknown quantity against modern air superiority machines because it takes a fundamentally different approach to survivability. Whilst in traditional DACT exercises, Typhoon pilots have often referred to the Gripen as ‘cannon-fodder’ due to its inferior thrust-to-weight ratio, speed, agility and armament, in the few cases where the Gripen has ‘come to play’ with its full electronic warfare capabilities, it has given Typhoons very nasty shocks. Against the Su-35S, Gripen would rely on the cutting edge EW capabilities which Saab builds the Gripen (especially the new E/F) around to hide the aircraft from the sensors of the Russian jets in much the same way as the Raptor relies on x-band stealth. These EW capabilities are so highly classified that there is simply no way to assess their effectiveness in the public domain. Having said that, RAF pilots who I have talked to with experience of the Saab fighter’s EW teeth first hand say that the ability of the aircraft to get alarmingly close without detection thanks entirely to EW is very impressive.” The answer that modern air combat has greater emphasis on fighting at a distance is not just an avoidant answer, but if the Gripen was a very energetic aircraft Saab would be keen to share this, as Eurofighter is with the Typhoon. It is however understood that Gripen has a particularly good instantaneous turn rate. ) What are the best and worst aspects of the Gripen? “I personally thoroughly enjoy the incredibly well designed HMI which makes it possible for me as a pilot to process enormous amounts of information and really interpret the tactical relevance of this information. The worst aspect of Gripen to me personally is that we are building such a fantastic and futuristic system but it is all on the inside so to speak. This makes it all a bit abstract and difficult to explain the full potential of the aircraft.”  How would a Gripen do in the following against a Block 52 F-16? A. WVR combat B. BVR combat C. Situational awareness E. maintainability- cost of ownership? “Generally we stay away from direct comparisons but if I were to compare Gripen to other fighters in general I would say that I have already touched on one of the subjects you ask about. Situational awareness in Gripen E is outstanding! All the way from the sensor suite (radar, IRST, missile approach warner, radar warner etc), the local fusion of sensor data in every Gripen, the global fusion of data shared within the tactical air unit (and C2) and via the HMI with the elaborate symbology and wide area display. This information chain and the situational awareness it creates is rally the foundation that all fighting rests on. With this said it comes as no surprise that I think that Gripen helps me as a pilot to perform really well in both BVR and WVR. The Swedish defense traditionally relied heavily on conscript personnel for tasks such as aircraft line maintenance. The operational doctrine of the Swedish air force also included operating from dispersed bases, basically a runway in the forest with no workshops or hangars. These two facts have been part of our design-genome for many years now. The result is that Gripen is very easy to maintain and also very fast to turn around between sorties. Generally we say that time for turnaround between two air-to-air sorties is done in 10 minutes and that is including both refueling and rearming! Ease of maintenance i.e. few hours to fix a potential problem and long mean time between failure add up to a high availability and low cost of ownership.”  Just how good is the Meteor-armed Gripen at BVR combat? Has it a big enough radar to take full advantage? “Absolutely! The radar is well balanced with the weapon reach. But the radar is far from the only source of information we use to get target data…” (By this I understand he is referring to the other sensors and information data-linked to the aircraft from off-board sources.)  What is your most memorable mission? “A number of sorties comes to mind, my first display with the SwAF display team, my very first solo sortie at the air force academy, QRA sorties during the cold war when the Baltic was buzzing with activity or when I got to bring my children up in a jet trainer. But if I had to pick one sortie I think it would be something very different. About 10 years ago I was assigned to 2 Squadron in the South African Air force. My mission was to train the first South African group of pilots on Gripen. After a successful training and 18 months in the country I was about to move back to Sweden. One final sortie remained. It was a night flight and the weather was fantastic with stars everywhere. I spent that hour and a half cruising among the stars and contemplating what a fantastic job I have. When heading back to home base the mission controller greeted me with a cheerful “welcome back to earth sir”. I think the combination of a beautiful scenario and the end of a great mission all added up and made it a very emotional sortie.”

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What is the biggest myth about Gripen? “Actually haven’t heard so much negative. Maybe people are too polite to tell me. But I think one might be that a lot of people have the conception that Gripen E only is a slight upgrade to Gripen C because of their similarities in appearance. Nothing could more wrong! It is a totally new aircraft, albeit based on the same general aerodynamic design as Gripen C.”  One Typhoon pilot described Gripen as ‘easy meat’, how would Gripen perform in BFM against the following types? Typhoon, Rafale, Hornet, MiG-29 and F-22. “Again no direct comparison but as I said above, the one with the best information wins the fight. It’s been a fact since world war one and still is. The only difference is how the information is gathered. In the old days looking with your eyes, today and in the future sensors and fusion of sensor data. The classic BFM I would say is no more and if you try it you die. In a world of high of boresight missiles, such as IRIS-T, data-link cueing and helmet mounted displays the within visual range fight looks more and more like a mini-BVR fight.” What should I have asked you? “What’s the best thing about being a Gripen test pilot? The possibility to influence the future design and functionality of Gripen. I think all fighter pilots can relate to this. During training and operational use of the aircraft every pilot formulates his/her ideas of how to improve the design and functionality and now I really get to this. It’s also a huge responsibility. It’s important that I can meet fellow pilots in the air force and feel that we met their demands and built the most pilot friendly and operationally efficient aircraft possible.” What equipment would you like to see integrated into Gripen? “Weirdly enough I will answer more computer power and unlimited broad band data-links. I think this is the key to success in a future scenario. The things you can do with computational power and data sharing is astounding and we are a good way down that path with Gripen E but you always want more. Luckily some clever engineer foresaw this and designed the avionics to be basically plug and play with both new software and hardware!” Thoughts on Gripen Politics is the biggest decider in arms deals, so what are the political advantages of going Swedish? One may be that for some nations it is a less inflammatory move than purchasing from the US and Russia. But is the Gripen independent from the US? In the past the US has beat down potential rivals to its commercial dominance by refusing export licences (something it may have done in the 1990s with AMRAAM during the search for the next Finnish fighter). Though Gripen E will have European missiles (Meteor & IRIS-T) and radar — it has a US-licensed engine and will probably use US guided munitions (Paveway and JDAM) as well as a US or Israeli targeting pod. Also despite Saab’s streamline, unbloated, approach to manufacturing – can spare parts for an aircraft produced in tiny numbers in an expensive country be cheap? Gripen E is likely to be far cheaper to operate than the F-35 and is likely to be the only aircraft offering comparable levels of situational awareness in the near term. This is a big plus, and this is combined with the already operational long range air-to-air Meteor missile. If Saab can keep the Gripen E price down, and a suitable political climate prevails, it should find more customers, even in a massively over-saturated market.

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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Undoubtedly the two most formidable fighter aircraft of the Cold War were the US’ F-15C Eagle and the Soviet Su-27, code-named ‘Flanker’. Which would have had the upper hand in air combat? We ask former USAF F-15 pilot Paul Woodford.  “The Su-27 Flanker, as a threat the USAF F-15 community needed to take seriously, emerged in the late 1980s as significant numbers of the aircraft began to be fielded. During my first two F-15 tours (Soesterberg AB NL from 1978-1982, Elmendorf AFB AK from 1982-1985), the air-to-air threats we trained against were the MiG-21 and -23. By the time I finished a joint staff tour and returned to flying Eagles in 1989, MiG-29s and Su-27s were the primary threats, and we trained seriously against them. If you look at publicly released figures on the F-15, the Su-27, and their weapons, you see right away the Flanker and the Eagle were evenly matched in terms of aircraft performance and weapons capability. Nevertheless, we—Eagle drivers—felt confident we would prevail in combat. This was based on our knowledge of the training hours Flanker pilots got in comparison with ours. When I started flying F-15s again, at Kadena AB on Okinawa, Japan, we trained almost exclusively against forward-firing beyond visual range threats; i.e., Su-27 Flankers and MiG-29 Fulcrums, even though their numbers, at least in our area of operations, were small. If we could defeat aircraft similar in capability to our own, we figured, we could beat anybody. We didn’t know how good the Su-27’s radar was. Ours was damn good, and we had to assume theirs was too. Our air-to-air weapons, the AIM-7M Sparrow and AIM-9M Sidewinder, were on paper evenly matched against the Su-27’s AA-10 Alamo and AA-11 Archer. An advantage the Su-27 had over us was its long-range infrared search and track (IRST) system.

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Now no one would have bet the bank on any of what I’m about to share with you. We had to assume the aircraft and its missiles were at least as good as ours, and that’s how we trained. But there were a few things most of us felt, though we rarely shared those thoughts. Published performance specs and numbers are always best-case, radar target acquisition and missile engagement ranges in particular. The probability of kill for our Sparrows was somewhere around 50%. Pk for the Alamo was probably similar. Short-range heat-seekers were different: the AIM-9M’s Pk was nearly 100%, and we had no reason to think the Archer was any worse. We knew the actual performance capabilities of our own aircraft and missiles were somewhat less than advertised and so, likely, were theirs. But whatever the numbers, we were probably still evenly matched. The big difference was training. We flew, on average, three times a week, training hard against a threat as good as we were. At the time, based on intel, we knew Russian pilots were flying and training far less. Tacticians at the Fighter Weapons School at Nellis AFB in Nevada were working hard on how to beat BVR threats as capable as our own, specifically ways the F-15 and its missiles could defeat the Su-27 and its missiles. They developed what at the time was a classified technique called the f-pole manoeuvre. Basically, we’d enter the fight high, fast, and as head-on to the threat as possible (giving our AIM-7s the longest possible ranges), launch at max optimum range, and immediately crank into hard turns away, right to radar gimbal limits. Our Sparrows were in the air, flying straight at their targets along the shortest possible distance. Their missiles, had they launched at the same range, had to fly farther to get to us. The f-pole manoeuvre, properly executed, might even give their IRST systems a harder problem finding and tracking us, but I can’t attest to that. We had a lot of confidence in this technique and practiced it religiously, and believed it would make the crucial difference in combat. In other words, we thought we were ready for them. We were better trained. We were just starting to field the AIM-120 AMRAAM when I left Kadena for another staff job, and I never flew with it. I’m guessing it gave us a tremendous advantage for a year or so, until the bad guys caught up. Ditto the AIM-9X and today’s enemy equivalent. And of course today everyone knows about the f-pole manoeuvre and we can assume foreign air forces train their fighter pilots in the technique. I don’t get to talk to current USAF fighter pilots much these days, but I bet their level of confidence in being able to defeat enemy threats is no different than ours was.” — Paul ‘Skid’ Woodford Read – Cold War Eagle Driver: F-15 pilot reveals all here Follow Paul’s aviation adventures on his blog here

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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