YE-4 | MiG-21's true predeccessor

Fact for 3/6/2021



Mikulin AM-11 turbojet, including addition of a second hydraulic system

Design and Features

It was a lightweight fighter, achieving Mach 2 with a relatively low-powered afterburning turbojet, The fuselage is semi-monocoque with an elliptical profile. The air flow to the engine is regulated by an inlet cone in the air intake.
For speeds up to Mach 1.5, the cone is fully retracted to the maximum aft position. For speeds between Mach 1.5 and Mach 1.9 the cone moves to the middle position. For speeds higher than Mach 1.9 the cone moves to the maximum forward position ,When ejecting, the SK-1 ejection seat connects with the canopy to make a capsule that encloses the pilot. The capsule protects the pilot from the high-speed airflow encountered during high-speed ejections. After ejection, the capsule opens to allow the pilot to parachute to the ground, On both sides of the nose, there are gills to supply the engine with more air while on the ground and during takeoff , The YE-3 uses a tricycle type undercarriage
In 1953 the Soviet authorities issued a requirement for a Mach 2 clear-weather interceptor with limited ground-attack capability. At this time the USSR’s Central Aerodynamics and Hydrodynamics Institute had arrived at two basic configurations for aircraft of the required performance level. Both were based on a cylindrical fuselage with a swept all-moving tailplane and a wing in the low mid-set position, but the difference came in the wing itself. One was a conventional type with a leading-edge sweep of between 580 and 620, and other a delta with 570 or 580 leading-edge sweep. The MiG bureau produced prototypes in both configurations. The Ye-50 and Ye-4.

An RD-9Ye turbojet was used in the Ye-4 with a delta wing, which first flew in December 1955. The Ye-4 was the true progenitor of the MiG-21, becoming the Ye-4/2 with airflow fences.