A great aircraft is the civil (or military) partnership of a good engine and good airframe, and sometimes a separation is necessary to make way for a more appropriate partner. Many great airframe aircraft have been held back by combination with inappropriate or inferior engines. Here are 10 power-hungry flying machines that finally got the grunt they deserved.
10. Tupolev Tu-22/Tu-22M ‘Ziggy Red Stardust’
The Tu-22 is the David Bowie of aircraft, reinventing itself with such radical vision that you’re left to ponder what exactly is left of the original. Little wonder the supersonic bomber required reinvention really when you consider how awful the original Tu-22 was. The original Tu-22 was abysmal in almost every sense and detested by its crew and maintainers. Appalling unserviceability, misanthropic handling characteristics – a wing that allowed aileron reversal at high deflections – a tendency to pitch up and strike its rear end on landing, disappointing range and poor pilot view were only some of the problems endured by the hapless Soviet aircrew condemned to fly the ‘Blinder’.
The design bureau, Tupolev, was under pressure and didn’t take long to plan a major upgrade to this stinker, starting work the very same year the type entered service, 1962. Ten years later a virtually unrecognisable aeroplane, with different (and variable geometry) wings and a host of other modifications, entered service.
Despite all the radical changes, it didn’t get a new model number, just the humble addition of an M. NATO intelligence more appropriately, but incorrectly, guessed it to be the ‘Tu-26’. But it was still a dog. The terrible Dobrynin RD-7 turbojet of the Tu-22 had been replaced with the newer, but also shit, NK-22.
The most important change didn’t happen until the Tu-22M3 update, which included the replacement of the NK-22 with the hunky-dory Kuznetsov NK-25 turbofan and rather handsome wedge intakes. The new engines came hand-in-hand with other aerodynamic improvemts including a recontoured nose and greater maximum wingsweep. With these all new refinements, the top speed leapt from Mach 1.65 to 2.05 and its range was increased by a third.
(In retrospect I feel terrible comparing a Russian bomber to David Bowie)
9. Blackburn Buccaneer ‘The Speyed Seadog’
Blackburn are famous for making less than brilliant aeroplanes, and the initial Blackburn Buccaneer was no exception. The innovative S.Mk 1 was powered by the de Havilland Gyron Junior, and was a weakling. It was underpowered, as test pilot Dave Eagles quipped in his Hush-Kit interview it “relied on the curvature of the earth to get airborne ”. This was solved when the S.Mk 2 was introduced in 1962, powered by the Spey. Replacing the Gyron Junior of 7,100 pounds-force each with the 11,000 lbf Spey was a masterstroke. The result was a superb low-level aircraft with a long-range (longer even than the Tornado), a virtually indestructible construction and a rock-steady low-level ride. The type proved its worth in Desert Storm, and remained to the end of its life a potent weapon.
8. Douglas C-47/DC-3 ‘Dakota turbo Fanning’
The DC-3 was a civilian airliner developed in the mid-1930s. At the beginning of the Second World War, it was adapted (with minor modifications) into a military transport aircraft and (predominately) designated the C-47. Over 95% of the airframes built were these military versions. During the decade of C-47 production, several engine variants were used, without significant changes to the type or size of the engine. The original DC-3 was powered by the 9-cylinder Wright R-1820 Cyclone 9 producing 1,000 horsepower. The C-47 predominately used the 14-cylinder Pratt & Whitney R-1830 Twin Wasp which produced 1,200 horsepower.
Roughly one-third of the US-built aircraft was the C-47B variant. This aircraft used Pratt & Whitney R-1830-90 engines with a high-altitude two-speed supercharger. This 1942 modification was critical for the China-Burma-India supply routes and allowed the aircraft to carry full payload over the 15,000’ mountain passes.
The Super DC-3 was developed post-war using 9-cylinder Wright R-1820 Cyclones producing 1,475 horsepower. While not commercially viable due to the extensive airframe modifications required, the US Navy converted 100 aircraft and they were designated R4D-8 and later the C-117D. This variant had a cruise speed of 250 mph, up from 224 mph for the original C-47.
C-47s were also produced during the war in the Soviet Union and in Japan (due to pre-war licensing agreements). In both cases, similar engines produced in those respective countries were used. The Soviet version used the 9-cylinder Shvetsov M-62 producing 900 horsepower, and the Japanese used the 14-cylinder Mitsubishi MK8 Kinsei 43 producing 1,000 horsepower.
On a final note, a few airframes have been upgraded in recent years with various turboprop engines. With similar power, the aircraft performance is only modestly improved. However, the upgrade does significantly improve the engine maintenance and reliability.
7. Lynx RR Gem to LHTEC CTS800 ‘Lynx Wray’s Comanche‘
The Westland Lynx burst onto the scene in the 70s showing previously unknown levels of manoeuvrability for a helicopter thanks to a semi-rigid rotor head hewn from a solid block of titanium and two Rolls-Royce Gem gas turbines. The 2,000 odd horsepower available from two tweaked Gem 60s helping drive G-LYNX to a helicopter World Speed Record of 216kts (400 km/h, M0.32) in 1986, a record which it still holds today.
The Gem began life with de Havilland prior to its merger with Bristol Siddeley in 1961. Rolls-Royce acquired Bristol in 1966 and the engine finally entered production in 1970 as the Gem RR.360. A compact design the Gem features an axial and a radial compressor, mounted on separate concentric shafts, with a third shaft for the power turbine passing through the centre to the reduction gearbox in front of the intake. The small size is aided by reverse flow combustion chambers where compressed air enters towards the rear of the engine before moving forwards to have fuel added. The resultant hot gases then turn through 180 degrees to pass over the three turbine stages which are surrounded by the combustion chambers.
Unfortunately, as with people, as aircraft age they tend to put on weight – the odd defensive aids suite here, an infra-red camera there – and suddenly you’re struggling to see your toes in the morning. A process made worse if rather than flitting around the North Atlantic you find yourself committing the classic blunder of getting involved in a land war in Asia, where the air is hotter and thinner. Both factors that count against engine and rotor blade performance. There are basically two ways out of this inevitable decline, you could choose violence, set higher limits for the engines and gearbox to run at, and accept the parts won’t last as long. Or you could try finding a new engine.
Handily for Westlands, the Light Helicopter Turbine Engine Company (LHTEC) had just want they needed left over from the RAH-66 Comanche programme. The CTS800 despite weighing the same as the Gem produces 35% more power with a max output of 1563shp. Only 300 less than the max continuous power you could get from two Gems. This massively improved the hot and high performance of the Lynx Mk9A introducing novel concepts such as taking a full fuel load, and maintaining level flight after an engine failure, things the Mk9 couldn’t do in places such as Afghanistan or Iraq. The CTS800 also bought with it FADEC controls which are far more responsive and reliable than the frankly baffling system the Gem used to control fuel flow which seemed to involve blowing air from the compressors through a stainless-steel ocarina. Perhaps most confusing of all for aircrew and maintainers bought up on earlier gas turbines is the complete absence of oil or fuel leaks from the LHTEC engine.
The CTS800 was basically hormone replacement therapy for the Lynx and was so successful that after receiving the first of 12 converted aircraft the UK MoD stumped up £42M to have the remaining 10 Mk9s upgraded.
6. Wessex Wright Cyclone to Gnome, via Gazelle ‘Gnome Alone’
The Sikorsky S-58 was an entirely adequate helicopter powered by a Wright Cyclone piston engine that wouldn’t have looked out of place in a Dauntless dive bomber, or a Wildcat. If only because that’s where it started out. US manufacturers apparently having the same problem kicking the radial engine habit as British ones did going cold turkey on the Merlin. In the mid-1960s With the Royal Navy in the market for an ASW and General-Purpose helicopter Westlands hit on the idea of licence building the American aircraft, with one crucial difference. Out went 1200hp of high-octane, war-winning reciprocation and in came the Napier Gazelle. Which looked like an accident in a metal tube factory.
This was in fact a move of some genius. Although the Gazelle was down on horsepower compared to the Cyclone, 1450shp to 1525shp , it made up for this by being a few hundred pounds lighter. This gave it a power-to-weight ratio of 1.31shp/lb to the Cyclone’s 1.03shp/lb. Unlike the Cyclone the Gazelle didn’t need a heavy clutch and fan to keep air flowing over its cooling fins, nor did it vibrate like a tumble dryer full of bricks. For while the piston engine attempts to recycle dead dinosaurs into a rotational force by accelerating lumps of metal up and down a collection of tubes the gas turbine is a far more civilised device that does its magic by spinning a balanced shaft at high speed. Say 20,400 RPM for the Gazelle or about 10 times what the Cyclone was doing. At the same time gas turbines have about an order of magnitude fewer moving parts which is less of a headache if you’re trying to maintain them.
If one gas turbine is good, then two must be better right? Right. Which is just the approach Westlands took an upgrade was called for. This time two Rolls-Royce Gnome engines  were substituted for the Gazelle. These provided 1350shp each giving the Wessex Mk2 and 5 almost the same performance with One Engine Inoperative (OEI) as the Mk1 achieved with everything working. The Mk1’s OEI performance being something of an obvious weak point. The packaging was made relatively easy due to the compact size of the Gnome, 18.2” wide to the Gazelle’s 33”. In fact, the nose of an early Mk 2 is virtually indistinguishable from a Mk 1, apart from a baffling halving of the number of exhausts. To simplify the engineering challenge the output from the two Gnomes feeds into a combining gearbox the output of which goes to the same input on the main rotor gearbox as the Gazelle and Cyclone’s driveshafts did.
This extra power didn’t significantly alter the basic performance of the Wessex, the main rotor gear box just wasn’t designed to take much more than 1550hp continuously. However, it did allow it to take this basic performance to new places. For example, the H-34A had an out of ground effect hover ceiling of 5,500’, where the Wessex Mk5 had one of 10,000’ at an all-up mass of 11,500lbs. More power, smoother running, and capable of surviving an engine failure the Gnome-powered Wessex were Top Gun to the S-58’s Iron Eagle. 
 Accurate engine power figures are a bit tricky to get as it can be hard to know if the figure quoted is the max continuous power, or just what you can wring out of it for two minutes if your life depends on it. These figures are undoubtedly the latter.
 Inherited from de Havilland who had obtained a licence to build the GE T58.
 An honourable mention could be made for the S-58T where Sikorsky replaced the Cyclone with a Pratt & Whitney PT6T Twin-Pac turboshaft giving similar performance to a Wessex Mk5. But the resulting nose job was too ugly to be considered an all-round success.
(special thanks to Ron Smith)
5. Boeing KC-135 Stratotanker ‘Stratocruising’
The KC-135 is a great example of an aircraft with enough longevity to receive a significant performance upgrade with a new-technology engine. This aerial tanker, which is roughly based on a Boeing 707 airliner (both of which evolved from the Boeing 367-80) first flew in 1956 when turbojet engines were the norm. A turbojet, the simplest version of a jet engine, passes all the engine airflow through the compressor, burner and turbine. By contrast, later turbofan engines have a ducted fan at the front of the engine, and only a portion of the airflow goes through the core of the engine. This allows better optimisation of the engine and provides better fuel and weight efficiency, lower noise and less pollution. The KC-135 originally used four Pratt & Whitney J57 engines each producing 13,000 pounds of take-off thrust (with water injection). The first production turbofan engine, the Rolls-Royce Conway, entered service soon after the KC-135. However, its performance was only marginally better than a turbojet, and an engine retrofit at that time was not justified. Turbofan technology continued over the next twenty years, and it was finally time for an upgrade in the 1980s. And what an upgrade it was! An initial upgrade to the Pratt & Whitney TF33 engine was performed on 157 aircraft. This increased the tanker performance (fuel off-loaded and/or mission range) by 20%. The more significant upgrade came in the mid-1980s with the KC-135R model. This upgrade used the CFM56 engine and was applied to a majority of the fleet. The CFM56 produces 22,000 pounds of take-off thrust, a 60% increase over the J57 engine. This, along with a few airframe upgrades, allowed for a maximum take-off weight increase, and a significant increase in aircraft performance. Compared to the original A model, the R model can offload nearly 30% more fuel, and its mission radius is increased by 60% or more, depending on fuel offload. Takeoff field performance, noise, and emissions are also improved.
As a postscript to this story, the B-52 Stratofortress bomber is in the process of a modern turbofan upgrade. The aircraft, from a similar era, was upgraded to TF33 turbofan engines with the H model in the early 1960s. Further upgrades have been discussed for decades, but finally last year a retrofit to the Rolls-Royce F130 engine was approved by the USAF, with full development work now in progress.
4. North American P-51 Mustang ‘The 51st State’
Pairing the most aerodynamically advanced airframe in creation with the best aero-engine in the world was a match made in heaven. An excellent low-level fighter became a superb all-round fighter. Jealous British historians may claim the re-engining was an entirely British idea, but several in the US had also considered this happy marriage.
3. Macchi C.200-C.202/205V
When the Italian air force took the Macchi C.200 to war on the French border, Africa and the Balkans it proved utterly and dangerously outclassed. Its Fiat radial engine generated an unimpressive 870hp, leaving it underpowered compared to Allied opposition boasting 1000hp inline powerplants. Poor thinking in the 1930s had led Italy away from adopting powerful inline engines, in favour of the promise of reliable uncomplicated radials; in reality, all this thinking had got the Regia Aeronautica was a fighter force too slow to survive. Aware of the mauling Italian fighters were receiving, the General Staff frantically turned to Alfa Romeo and Fiat begging for radials of greater power, but none were forthcoming. In desperation, they turned to their German allies to request licence-production rights for the inline Daimler-Benz DB 601, as used by the formidable Bf 109 and Bf 110. The German engine had a far smaller frontal cross-section than the Fiat engine allowing for greater streamlining and far more power. A 601 was fitted to a C.202, and the machine was also given an enclosed cockpit. Thus the ‘Folgore’ was born in 1940- and it was one hell of a fighter. With a top speed of 372mph, it was as fast or faster than contemporary Spitfires and 109s – and its climb rate was spectacular, it was also agile and of extremely rugged construction. In North Africa, the Folgore proved a viciously superior fighter to the Kittyhawks, Tomahawks, Hurricanes and Fulmars it faced.
2. Grumman F-14 Tomcat ‘Flopgun’
The F-14 inherited a curse from the fat wheezy abortive F-111B it was made to replace, the lamentable TF30 engines. The TF30 story goes back even further, as it was originally conceived for the Douglas F6D Missileer a loitering ‘missile-truck’ of an aircraft which never flew. The TF30 proved passable for bombers looking to move extremely quickly at low-altitude without the violence of extreme dogfight manoeuvring and found gainful employment with the F-111. But, as a fighter engine it was terrible. Weak, thirsty, smoky, unreliable, pilots of the otherwise excellent Tomcat had to learn to manage these untrustworthy engines. The TF30-P-414A solved the reliability issue to some extent but the Tomcat was still underpowered. Eventually the Tomcat got the engine it needed, with the fitment of the excellent General Electric F110-GE-400. The new Tomcat was an awe-inspiring machine, with performance to match the world-class weapons and sensors.
The F-14’s engines have a bad reputation, is this deserved?
“Yes, as long as we are talking about the TF30 engines of the F-14A. You may know that the TF30 was intended as an interim engine for the F-14, but for several reasons it ended up as the primary. Plenty of other sources have described its limitations in a fighter. Something hardly ever mentioned is that in order to improve engine stability and longevity, maximum thrust in afterburner was actually decreased to roughly 17,000 lbs per engine. As I mentioned before, the TF30 did have good fuel specs and it also had good thrust, especially at lower altitude – but these points did not outweigh their poor performance as a fighter engine. But still, I flew A-models my entire career and I can tell you pilots did not sit around complaining about the TF30: they learned its weaknesses, worked around them, and went out and flew the best jet they could. They were Navy fighter pilots.” – Dave ‘Bio’ Baranek, TopGun instructor and Radar Intercept Officer
- Avro Manchester ‘So much to answer for’
The famous Lancaster was more than a re-engined Manchester, but was not that much more. In fact, the prototype Lancaster was a conversion of the earlier twin-engined bomber and was initially known as the Manchester III . The obvious change was the addition of two extra engines, but there was also a larger wing, general beefing up and a new undercarriage. Despite these changes it is absolutely fair to describe the Lancaster as a new ‘Manc’. The result was spectacular, and the mediocre Manchester became the most destructive and survivable bomber of its time.