The S-92: Czechoslovakia’s Me-262

The Messerschmitt Me-262 was the world’s first jet fighter to enter production, the first to enter full squadron service, the first to score an air-to-air victory, and is easily one of the WWII Luftwaffe’s most famous planes.

During WWII, Germany used the facilities of Avia in occupied Czechoslovakia to sub-contract parts for the Me-262 and planned to start full production of the fighter there. The western part of Czechoslovakia was liberated by Soviet troops in the last battle of WWII in Europe, in the conflict’s final 96 hours, and the commandeered aviation production facilities were captured intact.

(A Messerschmitt Me-262 with the Luftwaffe during WWII, and an Avia S-92 with the Czechoslovak air force after the war.)

After the end of the war, the Czechoslovak air force decided to restart production of the Me-262, designated Avia S-92.

Basic characteristics

The S-92 was an exact clone of the Me-262 and was nearly identical in all respects. The plane had a top speed of 496 kts in level flight, although 500 kts could be exceeded in a dive. It had a length of 34’9″ and a wingspan of 41’6″, and weighed 8,366 lbs empty. It’s range was relatively short, only 652 miles and even less if the pilot did a lot of climbing or high-speed flight. It’s ceiling was 37,565′ which was more than enough to intercept piston-engined bombers of the era.

The S-92 project

Although no completed plane was available, the Czechoslovaks had at their disposal complete blueprints, some completed sub-assemblies, a wide variety of parts, the technical manuals, and most importantly the production jigs and tooling needed to build the Me-262.

In late 1945, it was decided to have Avia commence production of the Me-262, to be designated S-92. The airframe and flight controls were manufactured in kit form by Avia.

The Junkers Jumo 004 turbojet engines were manufactured by Avia’s Malesice Engine Repair division, and were designated M-04.

The whole plane itself was basically hand-assembled by workers at the Letnany Research Institute. Production of the S-92 was neither easy nor fast; each individual plane took about 7,000 man-hours to make.

The S-92 fighters as completed were essentially clones of the Me-262. The underwing rocket racks were omitted. The Czechoslovaks initially painted them in Luftwaffe-standard greenish-grey, in fact some of them were painted using pails of RLM02 paint captured at the end of WWII. A few had blue lightning bolts painted on the nose. Some were later repainted in all-around OD green.

The armament was the same as the WWII planes, four MK-108 30mm guns in the nose. All of the guns used on the few completed Avia S-92s were actual German WWII-manufactured MK-108s.

The MK-108 was an exceptionally hard-hitting aircraft gun in an era when most fighters were still armed mainly with .50cal machine guns. Just a few rounds were enough to take down a four-engined bomber.

Project history

Production of the first S-92 was started at the end of 1945 and ran into early 1946. After last-minute checks, Avia transferred the first S-92 to the Czechoslovak air force in June 1946. The Avia S-92 first flew on 27 September 1946, with the company’s leading test pilot Antonin Kraus at the controls. The plane crashed three days later.

(The first Avia S-92 in 1946.)

The second S-92 first flew on 24 October 1946. It was the first to enter squadron service. All of the few S-92s built were assigned to a special all-jet subunit of the Czechoslovak air force’s 5th Fighter Squadron, which was based at Kbely airbase near the capital Prague. The planes were tasked with air defense of the capital. None had radar and all were basically daylight defensive interceptors.

(S-92 serial number V-33, the second completed example and the first to enter operational service.)

Early in the project, it was obvious that a conversion trainer would be needed. Three two-seat models were built, designated CS-92. They were essentially identical except that a second seat replaced some of the fuel. The first CS-92 (the third airframe overall) was delivered in September 1946 and first flew on 12 October 1946.

(CS-92 serial number V-35 was the second trainer and fifth overall airframe built by Avia. It is the only surviving Avia-built two-seater today. The lower photo shows the later OD green paint; it has since been repainted to the original 1946 greenish-grey.)

The second CS-92 first flew on 4 July 1948 and the third and final twin-seater first flew on 17 June 1948 (it’s unknown why the third was test-flown before the second). The three trainers remained in use the rest of the time the single-seaters were operational.

Czechoslovak experiences with the S-92

In general, the Czechoslovak air force’s findings were the same as post-WWII evaluations of the Me-262 by the USA and Great Britain. It was, of course, much faster than the WWII-design propeller fighters it served alongside in the late 1940s. For example, the La-7 “Fin”, which was the fastest Czechoslovak piston-engined fighter at the time and served alongside the S-92, was almost 150 knots slower.

The S-92 was a bit less maneuverable going into a turn than the La-7, however, as a jet it maintained it’s lift through the turn whereas a propeller-driven type tended to “bleed off” lift during the maneuver. Otherwise, once the pilot had mastered the plane, the S-92 was still, even in 1948, a very good fighter.

(Takeoff of a S-92.)

(A S-92 fighter inflight during the late 1940s.)

The type’s major problem was the engines.The M-04 (clone of the Jumo 004) was an axial-compression turbojet. It was started by a very small pull-start piston engine inside the intake spike.

During WWII, the Jumo 004 needed to be maintained before and after every flight, and had an overall lifespan of only about 30 flight hours. In Czechoslovak service, this was doubled on the M-04 to about 60 flight hours (although maintenance was still needed after every flight). This is not to imply that the Czechoslovak pilots were better than their German counterparts, rather, in peacetime the Czechoslovaks could gingerly work the throttles while taxiing and during the initial climb, whereas the Luftwaffe pilots needed to get the plane in the air as fast as possible.

Of course this did not “guarantee” a certain number of hours and the M-04 engines might have problems on the first flight. A cause of breakdowns was found to be opening or slowing the throttle too fast. Another problem was the engine flaming out during a sharp maneuver. Another problem (not directly caused by the engine design itself) was asymmetrical thrust in the event of one engine failure. The S-92 could safely fly on a single engine however in a jet, this was different to the twin engine propeller planes the pilots were used to. A dead engine on a piston-powered plane can be shut down and have it’s propeller feathered. On the S-92, a dead M-04 was simply drag off the plane’s axis. It took certain skill to use the rudder and wings to keep the S-92 in the air with one engine out.

Once the engine hit it’s lifespan limit, it could be factory-rebuilt. However, the Czechoslovaks found that the M-04 suffered from a type of metal fatigue called creep, and this was inherent to the Junkers design with no fix. After 300 hours or so of total flight time, it was not possible to refurbish the engine again and it had to be scrapped.

The three twin-engine conversion trainers were a good help and were most definitely needed to switch pilots from propeller-driven fighters to jets.

Foreign interest

Yugoslavia was interested in possibly buying the S-92 and in 1947 a Yugoslav air force pilot was trained in Czechoslovakia on the type. The Yugoslavs were interested in having a small number of jets to back up their mixed bag (P-47 Thunderbolts, Yak-9s, and Ikarus S-49s) of propeller-driven fighters. After reconsideration, it was decided to stick with piston-engined designs only for a few more years with the goal of getting a new top-line American-made jet later (the F-84 Thunderjet eventually entered Yugoslav service in 1953). The Yugoslavs were also concerned that, as Czechoslovak interest in the S-92 waned, that Avia might find it economical to simply cancel any Yugoslav buy. Yugoslavia therefore never operated the S-92.

Israeli interest in the S-92 is perhaps most intriguing. In 1948-1949, there was at least some interest by Israel in either placing a production order with Avia, or, simply buying all of the few completed planes immediately for cash. In 1950, Egyptian intelligence reported that a jet fighter had crashed at Ekron airbase inside Israel (the Israeli air force was still all-piston powered at the time) and that most likely it was a S-92. Some time later an Egyptian transport plane reported that it was being harassed by what appeared to be “a Me-262”.

In actuality, the IDF never flew the S-92. A deal to import the type was never finalized. Part of the myth may have been fed by intentional British “leaks” to Egyptian intelligence. The IDF “officially” began receiving Meteor F.8 jet fighters in 1953, but, reportedly, had been flying at least one or two earlier-version Meteors since 1950. This would have of course aggravated the Egyptians who were paying top-dollar for their British-made Vampire jet fighters in a bid to one-up the Israelis. It’s possible that the jet which crashed in 1950 was a Meteor and the British allowed the Egyptians to run with their S-92 theory. It’s also possible that the crash never happened at all. In any case, Israel has repeatedly (most recently in 2005) stated that it never flew the S-92 and there doesn’t appear to be any reason now for them to lie about it.

End of the S-92

Only twelve (nine single-seaters and the three two-seaters) S-92s were built. The main reason for the short production run was that they were essentially being handmade, and Avia viewed the project as an annoying distraction from it’s production license for the Soviet Yak-23 “Flora” jet fighter, which began building in Czechoslovakia in 1949. Avia was also eager to demonstrate readiness for a license to build MiG-15s (at the time, possibly the best fighter in the world) and they reasoned that hand-assembling old Luftwaffe designs would not impress the Soviets.

There were other reasons as well. While the MK-108 was a good gun, it’s 30mm ammunition was unique to itself. By 1949, the Czechoslovak arms industry was making ammunition for ex-German weapons from WWII, Soviet guns being supplied by the USSR, and of course Czechoslovak guns. At some point, the country needed to rein in the number of different ammunition types in production and the MK-108 seemed like an expendable item. Finally, although there were no more crashes after the first plane, the S-92 pilots were terrified of the constant engine problems and most thought it was just a matter of time before another went down.

(An Avia S-92 and it’s replacement, the MiG-15, a legend of the Cold War era. It is unusual to think that, for a few months anyways, these two types were flying at the same time over Czechoslovakia.)

In 1950, the S-92 was pulled from squadron service and reassigned as ground training planes. The three CS-92 trainers continued in use until 1951.

Several were retained as museum pieces and the rest scrapped. In all, the S-92 was probably more trouble than it was worth to Czechoslovakia. None the less, it made an interesting end to the Me-262 story.