{"id":29444,"date":"2020-12-15T12:48:53","date_gmt":"2020-12-15T17:48:53","guid":{"rendered":"https:\/\/philip.greenspun.com\/blog\/?p=29444"},"modified":"2020-12-06T11:10:07","modified_gmt":"2020-12-06T16:10:07","slug":"testing-the-first-jets","status":"publish","type":"post","link":"https:\/\/philip.greenspun.com\/blog\/2020\/12\/15\/testing-the-first-jets\/","title":{"rendered":"Testing the first jets"},"content":{"rendered":"\n

Hitler’s Jet Plane: The ME 262 Story<\/a><\/em> (by Mano Ziegler, a Luftwaffe pilot, included with Kindle Unlimited) has some interesting parts, especially regarding just how brave a person would have to be to be a test pilot in World War II Germany. <\/p>\n\n\n\n

Wolfgang Sp\u00e4te shows up and starts flying with minimal prep:<\/p>\n\n\n\n

Continuing his test programme a few days later, he lost power in both engines at 9,000 feet. From an examination of the earlier flight data \u2013 principally in flying at slow speeds \u2013 it could be seen that he had throttled the engines back gradually to 2,000 revs. At the end of this experiment he attempted to regain thrust by pushing the throttle levers backwards and forward repeatedly, but neither engine responded, the rev counter remaining at 2,000. A brownish-black banner of smoke streamed astern from the jets. The engines would not restart and after several more desperate attempts to regain control he had lost so much height that his only alternatives were abandoning the aircraft or crash-landing. Suddenly he recollected Wendel\u2019s instructions for such an eventuality. Wendel had once told him that in this predicament the thrust levers had to be restored to neutral and the engines restarted by the same procedure as if on the ground. At this juncture this advice was clearly not without its perils. If Wendel\u2019s advice was wrong, Sp\u00e4te would have lost so much altitude during the attempt that it would be too late to escape by parachute and he would be forced to crash-land. This might succeed but an explosion was a possibility. Fortified by the philosophy \u2018Nothing is known for sure\u2019, Sp\u00e4te decided to stake all on Wendel. Meanwhile the aircraft had sunk down to 4,500 feet and Sp\u00e4te had no more time to lose. Putting the thrust levers to neutral, he made an injection of fuel and pushed the left throttle very slowly forward. Suddenly there came the short explosive sound that was music to his ears, accompanied by an increase in speed which confirmed that the left turbine had ignited. The engine rev counter climbed to 4,500, a little later to full thrust. The altimeter read only 1,350 feet, but already Sp\u00e4te no longer needed to concern himself with the question of baling out or crash-landing. On one engine he could maintain at least this height. The starboard engine responded similarly and he made a normal landing. This extremely unsettling state of affairs for pilots was typical of what had to be endured when the powerplant of a new aircraft was not unconditionally reliable.<\/p><\/blockquote>\n\n\n\n

Why did the engines quit?<\/p>\n\n\n\n

The investigation into Sp\u00e4te\u2019s almost disastrous flight came up with the explanation that if the Me 262 yawed when running at low revs, the strong lateral airflow could stop the compressor wheels and extinguish the ignition flame.<\/p><\/blockquote>\n\n\n\n

In other words, the same issue that resulted in the death of America’s first female-identifying Navy fighter pilot (Kara Hultgreen<\/a>, who mistakenly tried to fix a bad approach with rudder instead of aileron, resulting in the shutdown of one of her F-14’s engines), though the German test pilot was exploring the flight envelope, not trying to land.<\/p>\n\n\n\n

Luftwaffe general Adolf Galland’s book is quoted in this one, regarding a May 1943 flight:<\/p>\n\n\n\n

The \u2013 at the time \u2013 fantastic speed of 850 kph in level flight meant a jump of at least 200 kph ahead of the fastest piston-engined fighter anywhere. Moreover, the aircraft could stay up from fifty to seventy minutes. For fuel it used a less costly diesel-type oil instead of the highly refined anti-knock kerosene which was becoming ever harder for us to obtain. First the works chief test pilot demonstrated one of the two warbirds in flight. After it had been refuelled I climbed in. With numerous hand movements the mechanics started up the turbines. I followed the procedure with great interest. The first engine ran smoothly. The second caught fire. In a trice the turbine was in flames. Fortunately we fighter pilots are used to getting in and out of a cockpit rapidly. The fire was soon extinguished. The second Me 262 caused no problem. We set off down the 50-yard wide runway at ever increasing speed. I had no view ahead. These first jet aircraft were fitted with a conventional tail wheel in place of the nose-wheel gear which the type had in series production. Additionally one had to step on the brake suddenly. I thought, the runway is not going to be long enough! I was going at about 150 kph. The tailplane rose at last. Now I could see ahead, no more feeling that you are in the dark and running your head into a brick wall. With reduced air resistance the speed increased quickly. I was over 200 kph and some good way from the end of the runway when the machine took off benignly. For the first time I was flying under jet power! No engine vibrations, no turning moment and no whipping noise from an airscrew. With a whistling sound my \u2018turbo\u2019 shot through the air. \u2018It\u2019s like having an angel push you,\u2019<\/strong> I said later when asked what it was like.<\/p><\/blockquote>\n\n\n\n

As noted above, the first planes literally could not be flown while rolling on their mains and the tailwheel. Pilots had to raise the tail by stepping on the brakes suddenly to get initial lift.<\/p>\n\n\n\n

\"\"<\/a><\/figure><\/div>\n\n\n\n

Hitler had the terrible idea of using the Me 262 as a bomber rather than a fighter, which slowed down development and production to some extent.<\/p>\n\n\n\n

In the Messerschmitt factories and SS-run bomb-proof assembly plants there now began the hectic programme to follow the new plans for turning out the Me 262 fighter as a fast bomber. To extend its range two supplementary fuel tanks of 250 litres each were fitted beneath the pilot\u2019s seat. In the fuselage a 600-litre tank went behind what had been previously the main tank. This additional tank was the counterweight for the two 250-kg bombs slung below forward of the fuselage. Under normal circumstances aircrew would probably refuse to fly an aircraft cobbled together in this manner, even if the air force found it an acceptable addition to the fleet. Even without the possibility of encountering enemy aircraft it was problematic to fly the Me 262 bomber. Meticulous attention had to be paid to how the aircraft was manipulated. The particular problem was the rear 600-litre fuel tank. If this tank was full the aircraft was dangerously unstable without the bombs because the centre of gravity was too far back. Before dropping the bombs, however, the pilot had to ensure that the tank was empty. If he forgot this in the excitement of the moment or was forced to jettison the bombs in an emergency, the Me 262 became very tail-heavy and assumed an attitude out of the horizontal in which control could be lost. In turn the speed would drop to 700 kph or less, at which the aircraft was easy prey for a fighter. It was weakly armed in any case because two of the four machine-guns in the nose had been removed for weight reasons. Finally the Me 262 bomber had no bombsight and the pilot had to use the reflecting gunsight (Reflexvisier or REVI) for bomb-aiming in horizontal flight or a shallow dive. The instrument would have been useful in a steep dive but this form of attack was too dangerous to attempt.<\/p><\/blockquote>\n\n\n\n

The author describes Allied bombing raids as highly effective in disrupting German engineering, tooling, and construction of aircraft. Allied fighters are also reasonably effective in shooting down the Me 262. Pilots who bail out often slam into the empennage and break bones, a good illustration of why the ejection seat<\/a> is important.<\/p>\n\n\n\n

What were the engines like? The book quotes Dr Anselm Franz, who came to the U.S. and become VP of Avro-Lycoming (Werner von Braun and his 1,600 friends at NASA<\/a> were not the only Germans advancing “American” technology):<\/p>\n\n\n\n

Taken as a whole, the 004 jet bears great similarity to the modern jet engine. It consisted of an eight-stage axial flow compressor, six single combustion chambers, a single-stage axial turbine which drove the compressor and a jet with an adjustable needle which was built from the beginning for the later addition of an after-burner. A special regulator had been developed which at higher revolutions kept the selected revolutions and the corresponding gas temperature constant automatically. This regulator was mounted together with other equipment on the upper side of the compressor housing. The starter motor was located in the compressor intake hub. The contract specified a thrust of 600 kg at full throttle, but a large reserve was expected.<\/p><\/blockquote>\n\n\n\n

Materials were terrible compared to those that go into modern jet engines, thus leading to time-between-overhauls of 25-35 hours (125 hours for Frank Whittle’s designs in Britain). TBOs today are 5,000+ hours.<\/p>\n\n\n\n

Willy Messerschmitt is an interesting Silicon Valley-style entrepreneurial figure in the book. He overpromises and underdelivers. The business thrives in the early years of the war, a reminder of how the National Socialist German Workers’ Party gave a big boost to industry.<\/p>\n\n\n\n

It’s an interesting book for folks interested in the history of technology. It seems so obvious to us today that the jet fighter is better than the piston-powered fighter. But throwing major resources into the jet fighter wasn’t obvious to a lot of Germans, even though they saw the Me 262<\/a> flying with turbojet engines in July 1942.<\/p>\n\n\n\n

More: Read Hitler’s Jet Plane: The ME 262 Story<\/a><\/em>.<\/p>\n\n\n\n

Related:<\/p>\n\n\n\n