The Unsung British Test Aircraft that made Concorde Possible

Concorde, the world’s only successful Supersonic airliner, was a remarkable achievement for the Anglo-French aviation industry. Able to cruise at twice the speed of sound and at up to 60,000 ft., here was an aircraft really pushing the limits of 60s technology. However, as with any great achievement, there was a great deal of preparation and testing well before the first Concorde took to the skies.

For the purposes of this blog post, I will be ignoring the Concorde prototypes. Important though these aircraft were, their history is well documented and all are popular exhibits at their respective aviation museums. In other words, they don’t really count as unsung.

In addition, since I don’t know a great deal about them, I shall be ignoring French test aircraft for the most part. If you do have some information from that side of the channel, please do let me know.

Without further ado, let us get underway. We shall start with an aircraft that arguably failed. The Bristol 188 was an aircraft built for speed, out of advanced steels developed specifically for the purpose (You can see pictures of it here) Low drag was essential, and so the fuselage was very thin, barely wide enough for a pilot, and considerably thinner than the engines, which were fitted with a reheat. This would spray fuel into the hot engine exhaust, igniting it and producing more thrust, a feature Concorde also had.

Bristol’s design was actually developed as part of the operational requirement, mentioned in a previous post, for a Mach 3 bomber, but it would influence the materials choice for Concorde. Since the steel alloys developed were not proven, aluminum alloys were selected instead. The steel alloys were unproven because the aircraft was something of a flop.

The narrow fuselage and high fuel consumption combined to give it a perilously short range. It never had enough fuel to accelerate to its proposed maximum speed of Mach 2, and spent so little time at supersonic speeds that little useful data was collected. No Bristol 188 flight even made it to an hour in duration, and so the last aircraft, XF 926, was retired in 1964.

One standout feature of Concorde was the delta wing, a sort of triangular shaped aerofoil. This allowed for both low drag at high speeds and high lift at slower speeds, essential for an aircraft of this type. Delta wings were nothing new by the 1960s – the Avro Vulcan, first flown in 1952, featured them, and had been operational with the RAF for years.

Concorde’s delta wing though is what’s called an ogival delta, which means that the wing is not a straight triangle, and instead the leading edge follows a complicated curve, enhancing the lower speed lift of the wing. This had to be tested of course, and so, rather than going to the expense of building an entirely new aircraft, an already fast aircraft was selected to be modified.

The aircraft chosen was WG774, an aircraft which deserves a blog post, nay, a book in its own right. She had started life as a Fairey Delta 2 (and it looked like this) , an extremely fast aircraft for its time of the mid 1950s. It featured straight delta wings, attached to a slender fuselage which contained the single engine. In 1956, WG774, with test pilot Peter Twiss at the controls, became the first aeroplane to fly faster than 1,000 mph, and then broke her own record by over 100 mph. The record was only bettered by the US F-104 Starfighter (another aircraft deserving of a blog post).

Following modification, the aircraft became the BAC (British Aircraft Corporation) 221. Not only were new wings fitted, but many other aspects of the aircraft had been changed, including the air intakes for the engine, the landing gear and the entire cockpit and canopy. Though WG774 was slightly slower in this configuration, it did perform admirably and returned much useful data for the program. The cockpit could already be tilted down, in a similar fashion to Concorde’s “droop snoot”, and this was carried over to the BAC 221 with the new cockpit.

This was necessary due to the high angle of attack that delta wings require to generate lift at slow speeds. Ordinarily, this would mean that the nose would be pointed so high the pilot would have a poor view of the ground, or even none at all, which was hardly satisfactory. Many aircraft over the years would feature a “droop snoot” to solve the problem, including the ill-fated Soviet Tupolev 144, the only aircraft to come close to Concorde’s achievement.

Of course, in the slow speed regime, it was difficult to use one of the fastest aircraft on Earth. Thus, a decision had already been made to build another aircraft to test delta wings at slow speeds, which became the Handley Page HP 115. Fitted with a single, small jet engine, placed rather inelegantly on top of the fuselage, this aircraft proved that it was indeed possible to control a delta winged aircraft at very slow speeds, and flew many times during the 1960s. A picture can be seen here. It was even due to be flown by a certain Neil Armstrong in 1969, but, as I am sure you know, he became otherwise engaged…

There were many other aircraft that contributed, in many small ways, to the Concorde programme, which I have not mentioned here, for example the airliners used to shuttle engineers between the Britain and France. However, I thought that these were the most noteworthy, and certainly the most bizarrely British, and warranted bringing to your attention.

So where are we today? I am pleased to say that examples of all 3 aircraft can be seen at museums in Britain. XF 926, the sole surviving Bristol 188, now resides at the Royal Air Force Museum Cosford, not far from Wolverhampton. The Fleet Air Arm Museum in Yeovilton now houses both a HP 115, and WG774, the only BAC 221 that was ever made, along with a Concorde Prototype. Unfortunately, WG774 is quite literally overshadowed by the bigger, better known Concorde prototype, despite her significant place in aviation history.

As usual, comments are welcomed and encouraged.

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