Ye 4 Ye-5 / Kh 5 /1500 / MiG-21

The Ye-4 and Ye-5 frontline single-seat fighters were built in 1955 and 1956. Unlike the Ye-2 and Ye-2A, built at the same time, the Ye-4 and Ye-5 had a delta wing with a sweepback of 57 degrees at the leading edge. But the fuselages were identical; so because the wheel wells for the main gear were at the same place, the legs had to be modified to retract into the delta wing. That modification gave the Ye-4 and Ye-5 a slightly larger wheel track. A high degree of commonality between the two competing aircraft was to have allowed engineers to choose the wing shape for the future frontline fighter with full knowledge of the implications of their choice.

The wing profile was a TsAGl-S9s, the ailerons were axially trimmed, and the single-slotted Fowler flaps were rectangular. The air­brakes were placed beneath the fuselage—two of them near the wing root, the third hinged farther back on frame no. 28. The three sets of fuselage fuel tanks had a total capacity of 1,570 1 (414 US gallons), and the aircraft could store an additional 400 1 (106 US gallons) under the fuselage in a "supersonic" drop tank. The two NR-30 cannons (at sixty rounds per gun) flanked the lower part of the forward fuselage The shell cases were ejected, but the ammunition belts and links were col­lected in the empty part of the shell sleeves that ran across three fuse­lage sections. A pylon under the fuselage could carry either an auto­matic rocket pod (16 ARS-57) or one FAB 500 bomb. The ASP-5N gun – sight was linked to the SRD-1M Konus ranging radar. The slab tailplane was actuated by a BU-44 servo-control unit and the aileron controls were boosted by a BU-45 servo-control unit, both of the irreversible variety. The slab tailplane was fitted with the ARU-3V feel computer to modify the gear ratio between the stick and the stabilator and to con­trol the stick load according to flight speed and altitude. The ejection seat was identical to that of the MiG-19S (the curtain type). Main equip­ment included the RSIU-4V VHF, the ARK-5 automatic direction finder, and a radar warning receiver.

The last stage of the long development process that was to lead to the MiG-21, the Ye-4 was powered by the AM-9 turbojet rated at 3,185 daN (3,250 kg st with reheat). This was virtually the only thing differen­tiating this aircraft from the Ye-5. The Ye-4 arrived at the flight test cen­ter in June 1955. After the usual proceedings (weight determinations, ground roll tests, and a few “leapfrog" takeoffs) the Ye-4 was first pilot­ed by G. A Sedov on 16 June. Factory tests ended on 20 September 1956.

During these fifteen months, several methods were tested to straighten the airflow on the wing—either six fences over the upper surface (four of which protruded ahead of the leading edge) or two

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Ye-4 second from top side view of the Ye 5 (MiG СЖВ four-view drawing)

The pros and cons of the delta wing approach were assessed on the Ye-4. The wing had two fences on the lower surface, but the Ye-4 has also flown with a clean wing.

On the Ye-4 with fences on the lower surface of the wing, the wing tips were markedly pointed.

On the same Ye-4, fitted this time with six fences on the wing’s upper surface, the square wing tips reduced the span by 600 millimeters (23.6 inches).

The Ye-5 retained the delta wing and upper-surface fences of the Ye-4, but the wing tips are again markedly pointed.

fences over the lower surface and an increase in wingspan (sharp wing tips). Finally a third solution was found: a chord extension on about one-third of the leading edge that formed a vortex-generating "tooth." After this modification the Ye-4 was transferred to the LI1, where it was tested a number of times at great angles of attack.

The Ye-5 was powered by the AM-ll turbojet with 3,725 daN (3,800 kg st) of dry thrust and 5,000 daN (5,100 kg st) of maximum thrust with afterburner. Its wing had six fences (four of which protruded ahead of the leading edge). It was moved to the flight test center on 10 Decem­ber 1955 and was first piloted on 9 January 1956 by V. A. Nefyedov. During a ground run-up on 20 February the engine caught fire, and the turbine was destroyed. After being repaired at the factory the Ye-5 made eight flights between 26 March and 19 May. Tests were suspend­ed once more when the turbine broke and the engine had to be removed. On 18 October the aircraft was grounded. On 27 October the AM-11 was returned to the factory to increase the volume of the after­burner, and on 24 November the nose of the fuselage was returned to the workshop to be lengthened by 400 millimeters in order to move the aircraft’s center of mass forward and increase the fuel capacity to 1,810 1 (478 US gallons). Those modifications had a strong influence on the final choice between the Ye-5’s delta wing and the Ye-2A’s sweepback wing.

The Ye-5 resumed its test schedule on 1 April 1957 and went up thirteen times before 26 May for reassessments of the aircraft’s flight envelope after the modifications to its engine and fuselage. No fewer than ten AM-11 test models and one production engine were used to complete the aircraft’s factory tests. According to the test pilot, the Ye-5 cockpit was roomier than that of the MiG-19, and the approach and landing procedures of both aircraft were quite similar. Extension of the gear had no effect on the aircraft’s trim characteristics. There was no change in the longitudinal trim anywhere in its flight envelope, and it was easier to fly than the MiG-19 at supersonic speeds. The forward movement of the cone ahead of the air intake plane was automatic from Mach 1.4 upward.

The factory tests of the Ye-5 or MiG-21 came to a close without major problems. All of its design parameters were met except for the range, which fell short because of the excessive specific fuel consump­tion of the engine that was renamed the R-l 1. Altogether seven Ye-5s were built, two prototypes and five preproduction machines.

The following details refer to the Ye-4

Specifications

Span, 7.749 m (25 ft 5 in); fuselage length (except cone), 11.737 m (38 ft 6.1 in); wheel track, 2.692 m (8 ft 10 in); wheel base, 4.48 m (14 ft 8.4 in); wing area, 23.13 m2 (248.9 sq ft); takeoff weight, 5,200 kg (11,465 lb), fuel, 1,300 kg (2,865 lb); wing loading, 224.8 kg/m2 (46.03 lb/sq ft).

Performance

Max speed, 1,970 km/h (1,064 kt); climb to 5,000 m (16,400 ft) in 1.6 min; service ceiling, 16,400 m (53,800 ft); range in clean configuration, 1,120 km (695 mi).

The following details refer to the Ye-5.

Specifications

Span, 7.749 m (25 ft 5 in); fuselage length (except cone), 11.93 m (37 ft 2 in); wheel track, 2.692 m (8 ft 10 in); wheel base, 4.48 m (14 ft 8.4 in); wing area, 23.13 m2 (248.9 sq ft); takeoff weight, 5,700 kg (12,565 lb); fuel, 1,500 kg (3,305 lb); wing loading, 246.4 kg/m2 (50.47 lb/sq ft).

Performance

Max speed, 1,970 km/h (1,064 kt); climb to 5,000 m (16,400 ft) in 0.6 min; service ceiling, 17,650 m (57,900 ft); range, 1,330 km (825 mi), takeoff roll, 730 m (2,395 ft); landing roll, 890 m (2,920 ft).