10. Sud-Est SE.200 Amphitrite ‘L’oie de l’épinette’ (1942)

Flying boats opened up the world in the 1930s. Who needed airports if you could land on water? There weren’t many large airports, so flying boats – in all their grand glamour – led the aeroplane travel revolution. Now air travel routes linking North America, Europe, South America, Africa and Asia were possible.

In the 1930s the French air ministry was tantalised by the possibilities of international travel and identified a need for a transatlantic flying boat airliner to serve Air France. The requirement specified a 6,000 km (3,700 mi) range – and being the 1930s – room for only 20 lucky passengers (and 500 kg of cargo, probably mostly consisting of Pâté en Croûte, Pastis and mistresses’ underwear).

The aircraft manufacturer Lioré et Olivier set about creating a large handsome six-engined aeroplane, the LeO H-49, powered by six of the then-new Gnome-Rhône 14R-26 1600-horsepower radial aero-engine. With the unfortunately timed nationalisation of the French aviation industry, the aircraft became a Sud-Est concern. The hugely impressive flying boat was named ‘Amphitrite’ after the sea goddess and wife of Poseidon from Greek mythology. Before the huge machine could be flown, Germany invaded France – but work continued at Marignane in southern France. The first aircraft, named Rochambeau, flew on 11 December 1942, and what a machine it was.

The German occupiers were impressed by the aircraft and seized it, taking it to Lake Constance in Germany for assessment. It was here that it was destroyed by RAF Mosquitoes. Four other airframes survived for a short time at Marignane, but one was wrecked by a USAAF raid that also severely damaged the other three.

Sadly, 2022 would see another beautiful six-engined giant aeroplane destroyed from the air with the destruction of the world’s biggest aircraft, the Ukrainian An-225.

9. Avro Canada C.102 Jetliner

In the turbulent 1970s, there was a saying about Canada: we could have had French food, British government and American technology but instead, we wound up with American food, French government and British technology.  Well, this over-populated, over-heated world has pretty much gone to shit and now everybody everywhere is up to their neck in cheap plastic crap made in China.  Yes, times change and the potential greatness just swirls off like some beautiful chemtrail in a carbon-laced sky.  Take the Avro Canada C.102 Jetliner, a four-Derwent airliner prototype from 1949. Ahead of the Boeing 707, the Jetliner was Canada’s first jet design and North America’s first jet airliner.  It was the premier regional jet, beating the Sud Aviation Caravelle by a decade and Bombardier by a lifetime.  The C.102 carried the first ever jet air mail: Toronto to New York City in an hour.  Howard Hughes took it for a spin, loved it so much he leased it for six months.  Damn English carpet-baggers running Avro Canada dropped this handsome, commercially promising bird to soak the RCAF budget with the CF-100 instead.  Good work federal government, Trans Canada Airlines and Avro Canada.  It was the perfect prelude to the capable, expensive and cruelly/sensibly quashed CF-105 Arrow.

So where is the C.102 now? Well, the nose is in a museum in Ottawa. Oh, and the landing gear ended up on a farm wagon some place.

9. Avro 722 Atlantic (1952) ‘Vulcan-do’

Flying from London to New York in an airliner based on the Avro Vulcan in less than seven hours would have been a truly remarkable way to travel. Intended for up to 113 passengers, who presumably didn’t mind a bit of noise, the 200,000Ib 600mph Atlantic was not pursued. A bonkers idea from the perspective of economy of operation – but absolutely appealing in terms of delivering noise-loving aesthetes a lovely silver monster. We asked aircraft noise expert Michael Carley his view of the Atlantic and he noted, “If you’re comparing to conventional subsonic airliners, it would certainly be louder than any modern airliner. It would probably have been much louder than any contemporary as well. FAA data taken at Dulles for Concorde and wide- and narrow-body airliners in the seventies have Concorde 10-15dB louder the

8. Convair Model 49

In the 1960s the US Army was growing sick of dependence on inappropriate USAF aircraft for the close support mission. Aircraft like the Republic F-105 Thunderchief were simply too fast and vulnerable to support troops on the ground effectively. Instead, the US Army wanted the versatility and forward-basing possibilities of a vertical take-off platform able to hover. To excel in the tough close support role the type would need to be heavily armed and armoured. This need was expressed formally as the Advanced Aerial Fire Support System or AAFSS.

Convair, a company famed for its adventurous designs, responded to the Army’s AAFSS requirement with typical ambition. Drawing on their experience with the tail-sitting XFY-1 ‘Pogo’ they proposed a two-man ‘ring’ (or annular) wing ducted-fan design quite unlike anything else in service, though somewhat similar to the experimental SNECMA C.540 Coléoptère. The concept was bizarre in appearance but Convair believed it was the perfect configuration for an aircraft combining a helicopter’s unusual abilities with some of the offensive features of a military ground vehicle. One of the greatest challenges was creating a cockpit that tilted so the pilot was not facing the sky in the take-off/landing and landed support parts of its mission. This necessitated a complex hinged forward fuselage giving the type its distinctly ‘Transformer’-like looks.

The Convair XFY-1 ‘Pogo’ tail-sitting fighter.

Two co-axially mounted contra-rotated rotors were to be powered by either Pratt & Whitney’s JFTD12 or Lycoming’s LTC4B-11 (GE’s T64 and Allison’s T56 were also assessed as candidates). The duct would generate more thrust from the engine than would the open rotors of a conventional helicopter design, which was a good thing as it was expected to weigh in at around 21,000 Ib (9526kg) fully-loaded.

The untold story of Britain’s cancelled superfighter, the Hawker P.1154, can be read here.

Armament for this monstrous machine would include a central turret with a XM-140 30-mm automatic cannon with 1,000 rounds or a launcher for 500 (!) WASP rockets and two remotely-controlled light machine-gun turrets with 12,000 rounds of ammunition or a XM-75 grenade launchers with 500 rounds. Addition to this already awe-inspiring arsenal were four hard points on the nacelles which could carry Shellelagh or BGM-71 TOW missiles, or even the M40 ‘106-mm ‘ recoilless gun! The weapons could be fired during any part of the flight profile (note the ‘hover firing’ position). The steel armour would be impervious to 12.7-mm rounds, but there was little or no provision for defences or countermeasures against surface-to-air missiles.

7. RF-4X Mach 3 Hellraiser 

In the 1970s, the Israeli air force wanted a reconnaissance aircraft capable of carrying the extremely impressive HIAC-1 camera. The F-4 was considered, but the G-139 pod that contained the sensor was over 22 feet long and weighed over 4000 pounds – and the Phantom did not have the power to carry such a bulky store and remain fast and agile enough to survive in hostile airspace. One solution was to increase the power of the engines with water injection, something that had been done for various successful F-4 record attempts. This combined with new inlets, a new canopy and huge bolt-on water tanks promised a mouth-watering 150% increase in power. This would have allowed a startling top speed of mach 3.2 and a cruising speed of mach 2.7. This level of performance would have made the F-4X almost impossible to shoot-down with the technology then in service.

The F-4X would also have been a formidable interceptor – something that threatened the F-15 development effort, causing the State Department to revoke an export licence for the RF-4X. Even with the increase in power, the Israeli air force was still worried about the huge amount of drag, but a solution came in the form of a slimmed-down camera installation in a specially elongated nose. This meant the interceptor radar had to be removed, which assuaged the State Department’s fears and the project was permitted to continue. However, worries from the F-15 project community returned (as did worries about how safe the F-4X would have been to fly) and the US pulled out. Israel tried to go it alone but didn’t have enough money, so the Mach 3 Phantom never flew. UPDATE: Or so we thought. In 2019 someone close to the project revealed to Hush-Kit that a high-speed Phantom variant had indeed served, though there is nothing in open-source literature.

5. Antonov An-71 ‘Madcap‘

Photos: Joe Coles

Inspired by the success of the Israeli Air Force’s E-2 Hawkeye in the 1982 campaign in Lebanon, the Soviet Union went about creating its own tactical airborne early warning and control aircraft – the Antonov An-71.

An operational requirement was formulated in 1982, with the aim of creating a land-based AEW&C aircraft at least as capable as the E-2C. The aircraft was required to have an endurance of at least 4.5 hours and the ability to detect low-flying aircraft and other low-observable aerial targets – and track 120 of them at a time.

After considering the An-12 and An-32 as platforms for the new surveillance aircraft, Antonov opted for the short take-off and landing (STOL) An-72 Coaler. While the ‘saucer’ rotodome was conventional, its position on top of the tail was radical. The tail fin itself was swept forward to compensate for centre-of-gravity changes; the T-tail was replaced by a low-set horizontal tail. To ensure there was enough power despite the weight of all the internal systems, an additional small turbojet was buried in the rear fuselage. Those onboard systems were to be operated by a mission crew of three, in addition to two pilots and a flight engineer.

Briefly, consideration was given to developing a carrier-based version of the Madcap, but there was no way to successfully fold the wing for hangar stowage and the thrust-to-weight ratio was inadequate for a ‘ski jump’ take-off. Instead, the Soviet Navy opted for the more conventional Yakovlev Yak-44 project, which, in the event, never progressed beyond a mock-up.

Deck trials of the Yak-44 mock-up.

Work on the land-based An-71 continued and a first flight followed in July 1985. Another prototype was completed before the programme was axed, the victim of the demise of the Soviet Union.

It’s hard to say whether the An-71 could ever have been a success, but flight trials demonstrated generally good flight characteristics and avionics performance – the radar was shown capable of detecting 400 targets over land of water within a range of 230 miles and simultaneously tracking up to 120 of them. With its rough-field performance, the Madcap might have been a very useful force-multiplier for Soviet tactical aviation operating over Europe’s Central Front in a late 1980s Cold War scenario.

4. Makhonine « Mak-10 » The Flying Extendable Dining Table

Several notable Russian aircraft designers fled to the west following the Russian Revolution of 1917. Sikorsky and Seversky were two of these emigres, and they founded Sikorsky and Republic respectively, two giants of US aviation, but Makhonine – a rather complex individual – took his unusual ideas to France.

By 1931 Ivan Makhonine, was a French nationalised engineer, working on a variable surface wing system (think flying extendable dining table). For take-off, economical cruise and landing the wings of his aircraft were fully extended, for high-speed flight the wing could be telescoped into the thicker inner wing section to reduce drag and lifting surface. In the extended configuration the wingspan gained eight metres.

The whole system was pneumatically operated and was coupled to a manual back-up system. To test his concept, Ivan Makhonine built a large single-engine monoplane equipped with the telescopic wing, the Mak-10 (not to be confused with the MAC-10 submachine gun beloved by Miami gangsters in 1980s movies). It flew for the first time on 11 August 1931, demonstrating that such a wing type could work.

It was nevertheless, like many French aircraft of the time, underpowered. Its twelve-cylinder Lorraine 12Eb engine was enough for such a large aircraft. A second version of the aircraft, the Mak-101, was built at the end of the ’30s to further studies of such an aircraft. The 101 was far more modern, equipped with an enclosed cockpit, retractable landing gear and a Gnome-Rhône 14K Mistral Major engine allowing it to reach 380 km/h. However, before the aircraft could begin its test campaign, the Second World War broke out, and the aircraft was captured by the Germans military. The aircraft was repainted in the colours of the Third Reich and transferred the aircraft to Germany for further tests. Its fate is unknown.

3. Hughes LHX SCAT

In the 1980s, the Hughes company was producing the world’s most advanced helicopter gunship for the US Army, the AH-64 Apache, so felt they were in a strong position to win LHX, the contract to build the next US Army attack helicopter. Their offer was extremely bold and quite unlike any flying machine before or since. The Hughes LHX SCAT had no tail rotor, instead using the NOTAR system allowing a shape that would have had far less drag than any other helicopter. The fuselage was an aerodynamically wasp-like pod with two sharply swept wings and a nose section closer in appearance to a supersonic fighter than an attack helicopter. Smaller than the other proposals, yet equally well armed and fast at an estimated 342mph. It is unclear what Hughes were offering the utility category for LHX.

2. Boeing LHX

Staying on the subject of LHX, Boeing rejected the notion of very high speed, deciding that stealth and advanced sensors were the solution to the requirement for enhanced survivability. Their proposal was shaped for low radar observability — with weapons mounted internally. According to the writer Bill Gunston, the proposal rejected cockpit transparency (windows) in favour of sensors creating an artificial view of the world for the pilot; the reason for this is two-fold, transparencies create problems for stealthy designs and at the time there was a fear of laser dazzling weapons (also seen on the stealthy BAe P.125 concept). 

Boeing’s embrace of stealth over speed won out, and a 1984 review of the proposals agreed. An updated requirement was issued – LHX / LOA – which insisted that the new aircraft must be low-observable (to radar and infra-red sensors) . Such a brief immediately wiped out the chances of any tilt-rotor designs with their massive frontal cross-sections.

The Hush-Kit Book of Warplanes will feature the finest cuts from Hush-Kit along with exclusive new articles, explosive photography and gorgeous bespoke illustrations.Order The Hush-Kit Book of Warplanes here

Boeing LHX SCAT.

Though knocked out of the LHX contest, American interest in high-speed battlefield tilt-rotors would soon return. Replacing the A-10 battlefield support aircraft with a vertical take-off aircraft could prove a boon for forward deployment and potentially offer far greater flexibility. In 1986, Bell and Boeing created a proposal for such a machine, dubbing it the Tactical Tiltrotor. This extremely ambitious machine promised supersonic performance, thanks to an ingenious propulsion system. On take-off, landing and speeds up to 186 mph the aircraft acted as a turboprop tilt-rotor with the engines fed from a central turbojet, above these speeds the rotors folded into the engine nacelle and the turbojet provided direct thrust. In this mode, a top speed of Mach 2 was anticipated. This already radical idea was to be combined with forward swept wings, canards and an internal weapons bay housing eight Hellfire or Stinger missiles. Work continued until 1990, when it was cancelled as the Soviet threat disappeared.

An artist’s impression of an early Bell / Boeing Tactical Tiltrotor concept. 

Various Bell / Boeing Tactical Tiltrotor layouts were studied, including versions with two turbojet engines. 

The novel internal arrangement of the Bell / Boeing Tactical Tiltrotor. 

This glamorous artist impression shows two Tactical Tiltrotors at extremely low altitude attacking with cannon and Maverick missiles. The Tactical Tiltrotor was probably an idea born too early, and included too many risky technical features.

This artist’s impression shows a glass two person cockpit and as a two-ship attack Soviet tanks on a bridge. 

In addition to the battlefield attack variant, a transonic combat utility convertoplane was considered. It appears that this design may have some external features designed to reduce radar conspicuity. 

Would the LHX Stingbat have been any good? Find out here.

1. ShinMaywa US-2

The LHX effort eventually led to the RAH-66 Comanche stealth heliocopter. As attack helicopter projects are as vunerable as an E-scooter on a motorway, the Comanche was cancelled. Not all was lost however, and the LHTEC T800 turboshaft developed by Rolls-Royce and Honeywell for the Comanche has seen considerable use. It powers the Super Lynx 300, AW159 Wildcat, Sikorsky X2 (an experimental co-axial pusher), T129 ATAK gunship and even serves (as a boundary layer control compressor) on a vast flying boat – the ShinMaya US-2.

The US-2 is an unlikely beneficiary of the LHX project. This majestic high-tech flying boat uses the T800 turboshaft for active boundary layer control giving the aircraft’s its spritely short-take off performance.

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