Korolyev S.K.4
 
Korolev-SK4-01
 
After attending the Kiev Polytechnic Institute, Korolev went on to the Moscow Higher Technical University (MVTU). There he was involved in design and construction of an increasingly ambitious series of gliders, culminating in the powered SK-4, designed for record duration flights in the stratosphere.
 
The student of the graduate course of the Bauman Moscow Technical University Korolev passed the production practice at the Central Aerohydrodynamic Institute (TsAGI), at the Tupolev Design Bureau. At this time, he was already working at the aircraft factory in Fili. At the same time, in 1929, he was preparing a thesis project, deciding to design a light-engine twin aircraft SK-4 (his advisor was Andrei Tupolev).
 
The design of the SK-4 aircraft, designed for a record range of flight, turned out to be original, detailed and well designed. The project manager was Tupolev himself, signing it with the first presentation. This is not the case in the practice of students. The Tupolev approved single-engine two-seater SK-4 project was then built and tested.
 
The aircraft was designed for a 100-hp Shvetsov M-11, but it had just came to production and Korolev couldn’t obtain one. As an alternative one Walter NZ-60 engine, 5-cylinder radial, of 60 hp was used.
 
The SK-4 could be used as liaison and trainer aircraft, but Korolev planned to use it also for long-range air raids. He wanted to surpass the achievement of the Yakovlev AIR-3 in which pilot Filin, with journalist Koval’kov onboard, performed a non-stop flight from Minvody to Moscow on September 6, 1929 (during 10 hours 23 minutes they covered 1750 km – a world record for this category of aircraft, unregistered officially because USSR wasn’t FAI member that time).
 
The SK-4 was tested in late 1930 – early 1931 by Korolev’s good friend Dmitry Koshitz, and Korolev himself also participated in the tests. During one of test flights, the engine failed and the SK-4 crashed (Koshitz wasn’t seriously injured, and Korolev wasn’t onboard that time). The record flight was never attempted.

Engine: one Walter NZ-60, 60 hp
Wingspan: 12,2m
Wing area: 15.36 sq.m
Length: 7,15m
Height: 1,88m
Empty weight: 500 kg
Takeoff weight: 690 kg
Maximum speed: 160 km/h
Landing speed: 68 km/h
Service ceiling: 4000 m
Ceiling: 4000m
Seats: 2
Flight endurance: 2 hours