Test Pilot | Where US fighters failed over Europe

foreign [Music] testing now you realize that a piston engine can never act up can never go supersonic because of the Dragon the propeller but when you're fighting an enemy you always want to have a marginal performance over their aircraft and the idea was to get to as higher mass number as possible now Mac one is the speed of sound so if you talk about 9.75 that's three quarters of the speed of sound and so on so it's all got to be below what if it's business what has the speed of sound to do with high speed flying to find out let's consider first a single point sending out small pressure waves continuously each wave travels outwards at the speed of sound now suppose the point itself is moving if its speed is less than the speed of sound the pressure waves still travel out ahead but of the point is traveling at the speed of sound the pressure waves cannot travel out ahead of it but the point is traveling as fast as they are this is the kind of way in which the speed of sound affects high-speed aircraft and therefore at high speeds the exact relation between the speed of an aircraft and the speed of sound is important but remember the speed of sound varies with temperature and therefore with altitude it's considerably lower in the stratosphere than at sea level we had captured two German types of aircraft fighter aircraft and landed inadvertent they are um crash landed in this country namely the wolf 190 and the message went 109 and in our tests we knew that these aircraft could fight at a max number of 0.75 now that is called the Tactical Mach number The Mach number which you can fight the maximum what you can find there's a tactical Max number and a critical Mach number the clinical Mach number is the one which is well beyond the Tactical one and it's the one at which if you get that far you have lost control of the aircraft let us consider the airflow around a wing this Wing section is symmetrical like most modern wings it is a typical flying attitude the air is slowed down at the nose to form what is called the stagnation region it speeds up as it passes around the curvature of the wing it slows down again towards the trailing Edge these changes of speed cause changes in the air pressure the yellow regions show reduced and the green increased pressure all these variations and pressure together produce lift and drag the airflow speeds up as it passes over the wing and reaches its maximum speed at a certain point The Mach number here will always be greater than that of the aircraft as a whole called the flight Mach number as the flight Mach number increases so does the local Mach number at the maximum speed up point eventually though the aircraft as a whole is flying at less than the speed of sound just at this point on the wing the air is moving at the speed of sound the flight Mach number when this happens is called the critical Mach number of the aircraft usually written M Crypt for any Wing section M crit will always be less than one we told them what the Tactical Mach numbers and whatnot is but there was no use because in World War II throughout the war not a single Allied fighter ever had a mass meter fitted in it mathematics were only fitted in experimental test aircraft so what we have to do in the cockpits the Americans and our people had a list of his bid against height so we'll tell them when when not to exceed that of course sense of fat body you said you've got a German up your tail and then in the middle gone bad up there you're not going to sit and look at your chops Hill I'm assuming so a heightened so-and-size now it's no good so we had to tell them what the characteristics were of the flight that they would fill in the airplane that would tell them they are approaching trouble and better United a bit fast so that was the job we had to do at low speeds the air behaves as if it were incompressible whatever pressure changes there are are so slight as to cause no color change but as speed increases the air does begin to show signs of compressibility the colors show regions of increasing and decreasing density the red area at the Leading Edge is the stagnation region where the air is being slowed down and becoming denser immediately behind are two blue areas where the rate of speeding up is greatest causing a reduction in density this diagram will remind us of what's Happening as the flight Mach number increases the flow at the point of maximum speed up on the wing reaches Mach 1 the speed of sound the wing has reached its critical Mach number and when this is exceeded a sudden sharp region of increasing density forms on the wing just behind the point of maximum speed up this is a shock wave it is a sudden jump in the pressure of the air it grows and moves back as the Mach number increases what caused the whole the whole situation and European War to change was this the B-17 Flying Fortress that projected the war in Europe from an altitude we were fighting at altitudes of 15 to 20 000 feet normally speaking suddenly this airplane projected the war up to 30 000 feet so it was a new ball game and there at first thought that these aircraft could look after themselves they were very heavily defended a lot of guns and they had a theater if they all start in close formation they would have the Firepower to survive I'm afraid this didn't work out at all and the first way they made like this was against a schweinfoot the ball bearing um Works in Germany and they took 600 forts and lost 60. now you cannot afford to lost weight like that because and each of these aircraft that are 10 men so you lose 60 aircraft 600 men got and their they thought about it and decided that it was just a bit of bad luck so this happened in august 19 43. he said he decided to make another rate against nine foot under the same basis in October 1943 same numbers of aircraft San Antonio unfortunately same result magic figure of 60 is quite coincidental there was 16 liter players lost again another 600 men quite unsustainable so it was decided they must have escort Fighters how are shock waves formed on the rear part of the wing every Point such as this one sends out innumerable tiny pressure waves at the speed of sound in the forward Direction these waves meet airflow in the opposite direction and make less and less progress until they reach a stage where they can't travel any further forward because the airflow itself is moving backwards supersonically it's like trying to step off an escalator going the wrong way pressure waves constantly pile up here and this is the shock wave a shock wave is a very narrow region about one ten thousandth of an inch thick across this region the supersonic airflow is violently reduced to subsonic speeds much of the Air's energy of movement or kinetic energy is dissipated as heat the temperature of the air rises suddenly as it passes through the shock wave there is also a sudden rise in pressure they introduced as the first fighter the one he'd like me secondly this aircraft the P-47 Thunderbolt and neither of these two were a success at all and Jimmy Doolittle same wonders was involved in this right to Turkey him was then the boss of the fighter units in the ex United States and are there and he came to Fogo and he said I'm getting very disconcerting reports from the tail Gunners and my fortresses that when the these Lightnings and Thunderbolts which were acting as top cover on the forts flying two thousand feet above them so the if the forts were attacked they could dive down on the enemy Fighters and the advantage and height and they send them diving down towards the Germans but just passing them and going straight on that's the last we see them they're disappearing into Oblivion sad fact was they were making big holes in the ground in Germany and what was going on why were they all disappearing like this and he sent a lightning and a thumbnail to farnborough and we tested them up as the speed of airflow is increased still further the region of SuperSonic flow goes on growing larger and a second supersonic region starts to form on the lower surface of the wing with another shock wave Shockwave because a vast increase in Drag and may cause serious control trouble thank you at speeds approaching the speed of sound the most important result of the shock wave is to cause the airflow to separate from the winged surface this is called shock-induced separation it produces a large turbulent wake which Alters the pressure distribution lift is reduce and the turbulence creates drag now remember the Germans could fight at seven five a lightning had a tactical Mach number of 0.68 useless the Thunderbolt had a tactical Mach number of 0.71 again useless and we have to tell the exact facts to the Americans so there were dumasly realize that neither of these Fighters were any good the Thunderbolt was very good at Ground attack and there was withdrawn into that role they will do the Lightnings from this escort Judy and put them on reconnaissance work now you may Wonder at this because the lightning distinguished itself in the Far East and then the top two American asses and the whole War were flying Lightnings in the Far East what was the difference the difference was simple as this a fight in Europe was standing in place at thirty thousand feet fight in the Far East never got much above fifteen thousand so because it was mainly a carrier bunny so that is the big difference the thinner the wing the less the air is speeded up and so the critical Mach number is raised these two wings are of the same general shape and of the same angle of incidence the tunnel speed is the same for each as it increases the shock wave forms on the thicker Wing at a Mach number of 0.8 but not a sign yet on the thinner one here it comes at last at a Mach number of 0.9 But Wings can't be made too thin or the landing speed would be too high so what was going to solve the problem well in that time the problem was solved but this wonderful aircraft the Mustang down there b-51 the Mustang was unusual in the fact it had a laminar flow away then if it is soon win as you can see and of course that is the clue to getting higher speed it also at first when it came out and I'm rather useless engine in the American Allison engine which was no good at high altitude so Britain saved it by real engineering it with the rolls-wise well and converted what was a very mediocre fighter into one of the best fighters in World War II certainly the best escort fighter now it had a tactical Mach number of 578. above the five seven five of their Millions here slowed up about 40 times is a schlier in picture of what may happen to an aileron as a result of shock waves the most striking effect of shock waves is a sudden very sharp increase in the aircraft's drag this is because the shock wave heats up the air and compresses it and this absorbs a lot of extra energy which has to be continuously supplied by the engines the rate at which the drag increases is itself highest somewhere around Mach 1. although the actual drag goes on growing all the time this sudden increase in drag above the critical Mach number is what used to be meant by the sound barrier now our own Spitfire was Superior to all these it had a tactical Mach number of 0.80 now normally speaking roughly speaking the difference between your Tactical Mach number and your critical Mach number was about 0.02 for example if you had a Spitfire however so I had a tactical max number of 0.8 and a critical Mach number has could go any height depending on the strength of the pilot playing on the stick and weird Farm bro didn't expand it on this foreign pr11 he died from 45 000 feet down to 28 000 feet now he was a huge man he weighed 17 Stone he was six feet two and he could pull a good hundred pounds on the stick um my limit was about 60 65 pounds and and 28 000 pounds he started to try pull out and as he pulled as he pulled on the stick there was a colossal band and Away went to propeller and most of the reduction here with it the whole machine there as you see and because these came off the center of gravity walked out in the pool at the tail now this is recorded this this was fully instrumented this album and as you know the don't gee that you have that the Spitfire is supposed to break up that is 10g and here we actually recorded 11. and when he when he came to of course he was blacked out the shutters came down and he found himself offered a bite um back up at 42 000 feet and without a propeller and covered in oil but they got these words together said to us they reckoned if he could work the emergency gear of the undercarriage he could land the aircraft back in Formula which indeed he did when I intermission and here's the astonishing thing but right where the William meets the Tuesday at the root of the wing to my other astonishment there was a gap of three inches at both Wings in other words she had slightly swept the wings back and that night number he attained and that died was 0.92 unbelievable with it and that is to this day the highest speed ever attend any personal engine aircraft that was in the 27th of April 1944. [Music]

Channel: Armoured Archivist

Views: 91,204

Keywords: Eric, Winkle, Brown, Fleet Air Arm, Royal Navy, Test Pilot, Pilot, British, World War II, Mustang, Lightning, Thunderbolt, P-38, P-47, P-51, Me109, Me-109, Fw190, Fw-190, speed of sound, mach, critical mach, tactical mach, Spitfire, Mk XI, Mk 11, testing, War Thunder, IL2, Masters of the Air

Id: VQzSQUQ33OQ

Length: 23min 10sec (1390 seconds)

Published: Sat May 13 2023