Phantom Speys and other Phantasies
Reverting to the original theme of the thread, I admit to having a vested interest in what might have been done differently. Back in the 1960's I suggest the RAF should have taken the Buccaneer about 5 years earlier, when various options were offered to the UK MoD. HSA should have been allowed to sell the anticipated Buccaneer Mk 50 follow on order to the SAAF. This might have encouraged other potential export customers to take the aircraft rather than be frightened off by the government's attitude to export weapons sales.
For information on the many potential Buccaneer variants see Roy Boot's book, but in summary they included inertial nav much earlier, terrain following radar, replacing the Blue Parrot attack radar, flat screen displays and a new HUD, internal guns, zero zero seats, 8 pylon wings, additional internal fuel, soft field bogie undercarriage, self starting APU, quick acting blow and even, towards the end of its life, a 'Wild Weasel' variant with the bomb bay stuffed with jamming equipment. An opportunity was probably missed when the engine rings were replaced after fatigue cracks were found emanating from some tapped holes where a bleed air duct passed through. If the replacement rings had been made with a bigger internal diameter it would have been possible to fit a 'large turbine' variant of the Spey and increased the thrust. There were even reheated variants suggested but I think by then the ideas were getting a bit silly.
We should have persisted with the proposals for bigger carriers which could have operated a mix of upgraded Buccaneers with the Phantom FG Mk 1 and would probably have prevented or drastically shortened the Falklands war. With a bigger RAF Buccaneer fleet, all the Phantom FGR 2 aircraft could have been dedicated to air defence rather than many starting life in a ground attack role. This would have helped defer some of the fatigue problems that beset the Phantom in later life.
With a bigger, more capable Buccaneer fleet in service with the RAF, our competitors on the other side of the Pennines could have skipped the Multi Racial Compromise Aircraft and moved, via fly by wire Jaguar and EAP to start a UK only Typhoon programme about 10 years sooner.
Moving from phantasy to the Phantom as some of the earlier posters have pointed out, there were several reasons for fitting the UK aircraft with Speys. The engineering reason was that the increased static thrust was required to permit the aircraft to operate at high all up weights from the smaller UK carriers. (Maybe that would not have been required if we had gone on and built the bigger ones?) The political reason was that it provided work for UK industry and there were lots of other areas where the aircraft were 'Anglicised.' If I remember correctly the rear fuselages were buit at Warton which must have been quite a challenging project at the time as its was a complicated titanium tiled, heat resisting structure. I believe that McDonnell Douglas anticipated many more Spey Phantom orders but none materialised so it must have been a very expensive development programme which I guess UK taxpayers funded.
Although the Spey had more static thrust and better SFC than the J79, the increased air mass flow and bigger intakes meant there was was more momentum drag as speed increased. In addition the reheat variable nozzle was quite a dirty design and the translating shroud and petals created a significant 'dead' area which caused a relatively large base drag penalty. There were proposals for uprated Spey 200 series engines with true convergent/divergent nozzles but they never materialised. However Rolls Royce did eventually allow the Chinese to licence build the engine - I wonder how many are still in service and what changes they made?
Its surprising how threads sometime drift off on a seemingly irrelevent tangent but then miraculously return to the original theme. Mention of low frequency vibration is a case in point. One of the early problems with the Phantom Spey was reheat buzz which was a low frequency, around 6 Hz, combustion instability. I think it was first seen during extended reheat runs during the early testing of the water cooled jet bast deflectors eventuially fitted to Ark Royal. People in close proximity to the aircraft just keeled over and collapsed on the floor as their innards were excited by the resonant frequency pressure waves. I can't remember what fixed it but I think there was some association with 'red standard' engines.
The FAA aircraft were fitted with fast reheat to improve their ability to bolt from the deck if they missed the arrester wires. This was not achieved with a catalytic igniter as suggested earlier as all the reheated Speys had that system. I can't remember all the details but one change was to ensure the throttle valve at the inlet to the reheat vapour core pump was held fully open whenever the engine was above 80% Nh. When reheat was selected, fuel rushed into the vapour core pump inlet as designed, but once the initial demand was satisfied the fuel in a long length of 3 inch pipe had accelerated up to high speed and suddenly had to slow down again. This generated a whopping water hammer pressure spike in the engine fuel feed system and began to damage all the flexible sections of pipework where braided bellows had been fitted to provide some installation compliance. This gave me some very interesting work for a few years and a particularly entertaining visit to RAF Leuchars.
I look back on my association with these two iconic aircraft with great affection and I learned a lot of valuable engineering lessons from my involvement. However with hindsight I have also come to realise just how risky aviation was in that era. When you look at the number of Buccaneer and Phantom aircraft and crews lost because of airframe structural failures or uncontained engine failures it brings home just how far military aircraft engineering has progressed. Whether that justifies todays astronomical costs is perhaps a subject for another discussion