Rummaging around in the loft as you do this time of year, looking for things to hang on the christmas tree, I found this press cutting, from the early 1990s, inside a 'Airfix' box (actually a Hurricane kit!) http://www.********.co.uk/WW2talk/spitfire_dive.jpg
Geoff, If you read Jeffery Quills, Spitfire he goes into a bit of detail about speed testing the late war piston engine fighters. Ive been doing a bit of research into it. Looking into the post war claims that the Mustang was faster, laminer flow and all that. Quill points out that the best of the late war fighters where faster (in a dive) than the contempory jet aircraft and the fact the spitfire could be safely dived at speeds over mach .9, where many of the jets could not. BTW mach speed test was done with a special Spitifre with a fully feathering prop, but the jist of the article is correct. Mitchels aircraft seemed to hold up to speeds that where never even close to those thought of at the time. Kev I'll dig up some more info, been enjoying it.
Several pilots reported reversal of controls at very high diving speeds during the war. This was due of course to the compression effect when closing to the speed of sound. Several pilots had very narrow escapes due to structural failures in these circumstances. A thoroughly interesting subject Geoff. Regards Tom
Several pilots reported reversal of controls at very high diving speeds during the war. This was due of course to the compression effect when closing to the speed of sound. Several pilots had very narrow escapes due to structural failures in these circumstances. A thoroughly interesting subject Geoff. Regards Tom A good few pilots have died having their aircraft suffered from compression. I'm not sure but I think the P47 had a bad rep for it.
Several pilots reported reversal of controls at very high diving speeds during the war. This was due of course to the compression effect when closing to the speed of sound. Several pilots had very narrow escapes due to structural failures in these circumstances. A thoroughly interesting subject Geoff. Regards Tom The reversal thing is a bit of a media hype and it always gets dragged up like the old cheshnut it is when talking about high speed dives, (wasnt there a silly film about this) It wasnt directly related to the compressability effects, basically what happens is that the loads are so high that the wing deforms as its not stiff enough undoing the aerodynamic effect of the control surface and negating its effect, the controls become heavy and if speed increases further can become completly ineffectual. It isnt a one for one reversal. This shouldnt also be confused with the poor roll control associatted with the earlier marks of Spitfire as speed which where traced to the fabric covered ailerons deforming which where replaced with all alloy ones from mk5 (I think) onwards. BTW the Spit wasnt alone in poor aileron response at speed, many other early war machines suffered as bad if not worse. Kev
A good few pilots have died having their aircraft suffered from compression. I'm not sure but I think the P47 had a bad rep for it. You mean compressabitiy effects? Which is basically a increase in drag as you approach mach 1. Its fairly complex but air isnt passing doing go at the same speed over the whole airframe. The lift part of the upper wing (and prop for that matter) air travels faster so will hit mach1 way before the actual aircraft does, this causes drag, buffeting and all kinds of horrid effects. The air simply cant get out the way fast enough and builds up exactly where you dont want it. The solution to a lot of this is better aeordynamics and the Germans knew this and swept their wings back making the actual air speed over the wing effecivley less (since its now going at an angle). Ive never seen any documentation about speed testing on a 262 or 163 but I bet they where pretty close to mach1 if someone had tried them. I betcha the allies did but there is now way they would admit the Nazis went supersonic before them. Theres a funny story where Sidney Camm is refusing to fit swept wings to his aircraft cos they where German invention, of coure he had to in the end. Never head anything about the P47 in detail but it wouldnt surprise me the Laminer flow P51 and the very thin Spitfire wing would no doubt have wing forms more like modern aircraft, the brick shit house P47 would probably suffer first. Kev
High speed dives were a problem because of heavy loads or compression on the elevators. The P-47C incorporated strengthened tail surfaces, the P-47C still had problems in recovering from high-speed dives. Beyond 500 mph, recovery from power dives was extremely hazardous, with the elevators being unable to respond because of compressibility forces. Weights were installed in the elevator control system in order to help to overcome the compressibility problems that had made high speed dives in the earlier P-47C extremely dangerous. On November 13, 1942, Lts. Harold Comstock and Roger Dyar managed to reach indicated airspeeds of 725 mph during high-speed dives in their P-47Cs. This was beyond the speed of sound, which, if accurate, would have made them the first pilots to break the sound barrier. However, it is likely that the airspeed readings were wildly inaccurate, since the terminal velocity of the P-47 is about 600 mph, and that the true speeds reached were probably in the 500 mph range. On another note I think compression on the elevators is caused when the air flow is the same under the elevator as on top but not sure.
Thanks for all your input guys, fascinating stuff. I can imagine air speed indicators would be way out of calibration. Don't think I'd like to try anything like this!
The reversal thing is a bit of a media hype and it always gets dragged up like the old cheshnut it is when talking about high speed dives, (wasnt there a silly film about this) It wasnt directly related to the compressability effects, basically what happens is that the loads are so high that the wing deforms as its not stiff enough undoing the aerodynamic effect of the control surface and negating its effect, the controls become heavy and if speed increases further can become completly ineffectual. It isnt a one for one reversal. This shouldnt also be confused with the poor roll control associatted with the earlier marks of Spitfire as speed which where traced to the fabric covered ailerons deforming which where replaced with all alloy ones from mk5 (I think) onwards. BTW the Spit wasnt alone in poor aileron response at speed, many other early war machines suffered as bad if not worse. Kev The Sound Barrier was the film in which reversing the controls was shown as being the way to safely fly faster than sound. It also featured a Spitfire flying at 5/600 mph in a dive. The film shows British pilots trying to break the sound barrier without mentioning that Chuck Yeager had down so 5 years before. Americans therefore sometimes bring it up when defending themselves against accusations that Hollywood distorts history by attributing British achievements to Americans e.g. in U571. It did, however, win an Oscar, ironically for Best Sound. Ralph Richardson won a number of awards including the NY Critics Best Actor award, the first time that the winner of this award didn't go on to win the Best Actor Oscar.
Thanks for all your input guys, fascinating stuff. I can imagine air speed indicators would be way out of calibration. Don't think I'd like to try anything like this! Yep pretty much. Airpeed indicator works by comparing 2 pressures, when into compressability, the pressures be vastly increased locally, thus giving a vastly too high reading, all depends on the gauge how its sited and damped etc. There where of course no Machometers on ww2 era fighters. Kev
Heres some (Objective??) Drag curve comparisons from the Air Ministry from tests after the war. From Ray Boots fantastic 'From Spitfire to Eurofighter'. Its doenst specify what mk of spitfire ot P51 this was done with but in Quills book he says the tests where done with a special mk XIV which is the single stage Griffon and fast as fu*k. From this you can see how fantastic the Spitfire was in 1935 and how poor the first jets where. Kev
While I have the scanner out, Heres what Aircraft Flight (Barnard and Philpot) have to say about control reversal on WW2 Fighters.
Here's something for all you users of Flght simulator X out there! If you own a copy of Real Air's superlative Spitfire IX & XIV add-on, try taking one of the incredibly accurately rendered Spits up to 30,000 feet or more and then half rolling over into a vertical dive. Just watch the altimeter unwind as the airspeed builds up and - if you've set your flight model preferences to fully realistic - notice how the virtual Spitfire emulates the real thing beautifully and forces you to push/trim forward to keep her diving the more and more the speed increases: the real Spitfire had a tendency to try to gradually pitch up in high speed dives, forcing the pilot to correct it. When you bottom out of your dive, try recovering without overstressing the airframe - not easy. The other thing you might like to do is try spinning the Spitfire. Don't attempt it below 10,000 feet AGL, and once again the Spit's spin characteristics are faithfully replicated, which much creaking and wind noise in the cockpit. Such fun! Real Air have done such a good job that you can even over boost the engine and then it seizes, forcing you to throw back the canopy and glide down to a dead stick landing. You can even do it wheels up if you prefer, and watch the sparks fly as you scrape along the tarmac....
Here's something for all you users of Flght simulator X out there! If you own a copy of Real Air's superlative Spitfire IX & XIV add-on, try taking one of the incredibly accurately rendered Spits up to 30,000 feet or more and then half rolling over into a vertical dive. Just watch the altimeter unwind as the airspeed builds up and - if you've set your flight model preferences to fully realistic - notice how the virtual Spitfire emulates the real thing beautifully and forces you to push/trim forward to keep her diving the more and more the speed increases: the real Spitfire had a tendency to try to gradually pitch up in high speed dives, forcing the pilot to correct it. When you bottom out of your dive, try recovering without overstressing the airframe - not easy. The other thing you might like to do is try spinning the Spitfire. Don't attempt it below 10,000 feet AGL, and once again the Spit's spin characteristics are faithfully replicated, which much creaking and wind noise in the cockpit. Such fun! Real Air have done such a good job that you can even over boost the engine and then it seizes, forcing you to throw back the canopy and glide down to a dead stick landing. You can even do it wheels up if you prefer, and watch the sparks fly as you scrape along the tarmac.... Thanks AC, sounds fun.
