Aviation of Word War II
Disadvantages of the P-39 "Airacobra"
Fighter Bell Airacobra Mk I from 19 GIAP, on which Major A.P. Zaitsev flew combat missions, spring 1942. The pilot died in this aircraft in a plane crash on May 30, 1942.
One should not think that "Cobra" possessed only merit. In terms of speed, rate of climb, maneuverability, it was inferior to domestic fighters at low and medium altitudes. But this was not the main drawback of the American aircraft. Due to the fact that the engine was in the center of gravity of the aircraft, the Cobra reacted strongly to the center of gravity change. After the cannon shells were used up, the centering changed sharply and the fighter often fell into a tailspin. With a delay in taking out of the spin by only half a second, the R-39 went into an even more dangerous flat spin. It was enough carelessness on a deep bend or a combat turn, and the pilot, who pressed the pedal a little harder than usual, immediately fell into serious danger. The corkscrew on the Cobra was also uneven - there was a beating of the control stick with great physical exertion.
In the report of the Air Force Research Institute on the testing of the P-39Q-10 aircraft (pilot K.I. Ovchinnikov), it is indicated: “Tug of the handle or the transfer of legs in aerobatics also leads to a spin. When centering is shifted back, the corkscrew tendency increases. " The most dangerous situation was when there was no ammunition on the plane, and the oil tank was filled under the neck. In relation to it, it was said: "It is very difficult to perform aerobatics on an airplane ... The slightest tug of the handle leads to a rapid drop in speed and a transition into a spin."
The corkscrew has been the cause of numerous accidents and disasters in combat units. For two months in 1944, because of this, only in the 1st Guards Air Division there were two disasters and four accidents. In some places, at first, there was even a panic fear of performing aerobatics on the P-39 (for example, I.M. Dzusov talks about this in his memoirs). Moreover, not only hastily trained wartime pilots crashed, but also experienced test pilots. Only at the Air Force Research Institute there were three catastrophes: on February 2, 1943, K.A. Gruzdev died on the Aerocobra I, K.A. Avtonomov died on the P-39N on January 3, 1944, and K.A. Avtonomov died on April 27 of the same year on the P-39Q-10 - K.I. Ovchinnikov.
The situation was so serious that in the fall of 1943 a special team of the Bell firm, headed by L. Rogers, who was in charge of the company for complaints, arrived in Moscow.
It was not easy to jump out of the P-39, which got into a tailspin. They jumped into the left door, which was thrown off in an emergency.
At the same time, a person often hit the stabilizer. The consequences of this could be fatal. Thus, Heroes of the Soviet Union N.M. Iskrin (in May 1943) and B.B. Glinka (in July 1944) were seriously injured. But even if the pilot was lucky and he got out of the spin, a new danger awaited him: due to large overloads, the tail unit of the R-39 was deformed, the rudders jammed. In March 1944, after a series of accidents and disasters, all Cobras were checked in the 11 Fighter Corps. On 15 machines, clear signs of deformation were revealed. The greater efficiency of the rudder could also lead to the fact that high values of g-forces could be obtained with sharp maneuvering. The result is the same, deformation of the tail and tail of the fuselage. Here are the lines from the report of the senior engineer of the 273rd division (September 1944): “Identified <…> twisting of the tail section of the fuselage in the radio hatch section during sharp evolutions in the air. There was a deformation of the skin in the lower end of the fuselage ... There was a case when in the air one of the halves of the stabilizer was bent towards the inner side.
In the USSR, a whole program of combating the main defects of the "Airacobra" was carried out. After careful tests, the pilot's actions were revealed, provoking a spin. The Air Force Research Institute conducted a training session of instructors, in part they sent experienced pilots who demonstrated safe piloting techniques for an American fighter. They even filmed the training film "Corkscrew of the Air Cobra". All this significantly reduced the accident rate at the front, although, of course, it could not completely save from losses.
By order of the Chief Engineer of the Air Force, restrictions were imposed on the alignment of the aircraft, it was forbidden to put covers and tools in the tail section when redeploying. Aerobatics without ammunition or ballast equal in weight was strictly prohibited. To shift the center of the fighter forward, it was sometimes practiced to remove the armor protection from the oil tank. They also began to strengthen the tail section of the P-39. It turned out that the safety margins of the Cobra were lower than those adopted in the USSR. In the design bureau of the Central Scientific and Operational Base (TsNEB) of the Air Force, engineer M.S. Malkov developed a technique for reinforcing the set in the tail section. The prototype aircraft was altered and tested at the Air Force Research Institute. Following this, the revision of the "Airacobr" was deployed directly in the shelves. In the air defense alone, 326 aircraft were converted in this way. In various parts, on their own initiative, other reinforcements were added to the fighter's glider. So, in the 273rd division, they put overlays on the stabilizer spars.
Other shortcomings of the Airacobra were also noted. Although the tricycle landing gear provided excellent visibility during taxiing and takeoff, and, in principle, made it possible to move around the airfield at high speed without fear of nosing, on uneven unpaved airfields the nose strut vibrated and often broke, which forced the taxiing speed to be limited.
Allison U-1710 motors were the same. as on the P-40. but tied up with an elongated shaft that went through the entire plane to the propeller. Accordingly, the problems remained the same. Here is what was reported from the 67th Guards Regiment in August 1944: “The engine does not work out the 250 hours it was supposed to have for its resource ... put ". Here only "shooting with rods" here turned out to be much more dangerous, since they could easily interrupt the rudder cables passing nearby.
Of course, part of the responsibility for this lay with the flight and technical personnel of our Air Force. Inspections in the units showed that the pilots used the afterburner excessively and did not monitor the condition of the oil system. And they did not always use the necessary brands of oils and gasoline. Our Cobras were usually filled with B-78 gasoline, which, of course, was worse than the American one. And in blockaded Leningrad and B-78 were replaced with a homemade mixture "compote". There is even a known case when a B-70 was poured into an American fighter and it took off safely!
Some alterations were associated with operating experience in winter: insulation of highways, installation of drain valves in the oil system and cooling circuits. To work with these cranes, small hatches were cut in the lower hood of the radiator. With the onset of cold weather, the lubrication of components and assemblies was partially replaced with a more frost-resistant Soviet one. For example, the main bearing of an elongated shaft was lubricated with NK-30 oil in winter. We tried to operate the engines on more frost-resistant Soviet antifreezes, but this forced the cooling system to be altered.
Just like on the Kittyhawks, on the P-39 there were cases of destruction of the tubes of the petrol system from vibrations, which led to a fire in the air. So during the ferrying of aircraft near Gudermes, Hero of the Soviet Union N.E. Lavitsky died. In this regard, American duralumin pipes were sometimes replaced with annealed copper pipes.
The Northern Fleet and the Baltic have tried to install a retractable ski landing gear on the Cobra. But this innovation did not take root - the P-39s continued to fly on wheels all year round.
The disadvantage of the "Airacobra" is the inconvenient trigger of the gun. Here is how A.I. Pokryshkin:
"... One very important issue was resolved positively. Another one had to be resolved. Ammunition of cartridges and shells was calculated taking into account the rate of fire of each type of aircraft weapon for eight seconds of continuous firing. An experienced pilot, a good shooter, shooting from close range, simultaneously using all weapons - machine guns and a cannon, could shoot down up to three or four enemy aircraft in one sortie.
However, the very first battles showed that we used a powerful cannon (37 mm caliber) poorly. They often returned even after a long battle with unused cannon ammunition. The reason is the inconvenient location of the cannon release button. It was on top of the plane's control stick. To press it, it was necessary to turn the palm of the hand a little, which interfered with aiming. This inconvenience was especially affected when firing on piloting with overloads. The control of all weapons had to be redone for one trigger, for the trigger of machine guns. The conversation on this issue took place with the engineer Zhmud.
- Comrade engineer, are you going to stockpile shells?
- How to store? I don’t understand you.
- Do you wonder why the pilots after the battle bring all or almost all of the shells, and the machine-gun containers are empty?
- I still cannot understand why pilots use a cannon poorly in battle.
I said that it is inconvenient to press the cannon button when firing. And he asked:
- By the morning, change the descent of all weapons to the machine gun trigger.
- But according to the instructions, this cannot be done without the permission of the constructor.
- My dear engineer, we pilots are fighting, not a designer. Redo immediately on my plane and on the planes of my squadron. In general, it is necessary to redo the entire regiment. The pilots will thank you for this.
- Let's do it. Nothing complicated. "
To speed up the process of retraining pilots, they created a training aircraft with a second cockpit in front of the main one, very similar to the American TR-39. They were made according to the drawings of the TsNEB Air Force in different parts and formations. V.P. Voronov, who flew on such a machine after the war in the 6th Guards Regiment, wrote: “The 'hybrid' performed its task, but in the front cockpit it was very uncomfortable: the propeller rotated about forty centimeters before my eyes. And if, in case of something unforeseen, you have to leave the plane with a parachute, then you will certainly get on the propeller. " With the exception of the reinforcement of the tail section, "Cobras" have not undergone any major significant structural changes. One can only mention the alteration of several dozen R-39s for M-105P engines due to the lack of spare Allison engines. Some minor changes were made directly to the parts. For example. Pokryshkin redesigned the control handle, combining the trigger of the cannon and machine guns.
In the 1st ferry division, a Soviet RPK-10 radio semi-compass was installed on one P-39 and used this machine as a leader when ferrying groups of single-engine aircraft. Radio half-compasses on some "Cobras" were also installed in the USA. Such machines also entered our country, but, apparently, in very small quantities, since they were not enough even in air defense units.
Production of the P-39 at the Bell plant in Niagara Falls ceased in 1944. The last five vehicles of the P-39Q type passed through to ALSIB at the very beginning of 1945. In total, according to various sources, from the United States delivered from 4,719 to 4,746 "Aerocobras" of various modifications. Another 212 aircraft were re-exported from Great Britain, 158 of them reached their destination. According to our data, 4952 aircraft were accepted in the USSR. We, however, also took into account faulty fighters sent by the British instead of group sets of spare parts. The breakdown by modification is only known from US military aid reports. According to them, 108 P-39D, 40 P-39K, 137 P-39L, 157 P-39M, 1113 P-39N and 3291 P-39Q were sent.