MiG 21PFM / MiG-21PFS / Ye-7SPS / Tip 34

The MiG-21 silhouette was again retouched. The tail fin chord was increased to improve the yaw stability margin total area rose to 5.35 m2 (57.26 square feet) without increasing the size of the rudder. The tail chute container found itself back—for good—at the base of the tail fin, and the chute canopy was given a cruciform shape. But the most significant modification was the addition of the SPS system (Sduv Pogranichnogo Sloya. boundary layer blowing) Air bled from the turbo­jet HP compressor was blown over the flaps’ upper surface, accelerat­ing the boundary layer speed and thereby delaying its separation. The overall wing lift was thus increased when the aircraft landed (pilots used SPS by choice). The MiG-21s equipped with this system were eas­ily recognizable by their bulky flap-actuator fairings located at flap midspan. The area of the flaps was slightly reduced to 0.92 m2 (9.9 square feet) per unit from the 0.935 m2 (10.06 square feet) of previous versions. Their deflection was 25 degrees at takeoff and a maximum of 45 degrees at landing. The engine was the same as that of the MiG – 21 PF, but the letter s (for Sduv) was added to its official name. It thus became the R-11F2S-300 (or 37F2S in some documents). It was rated at 6,050 daN (6,175 kg st) with afterburner

The cockpit canopy was thoroughly modified. Instead of opening upward with hinges to the front, it was divided in two elements: a fixed windshield and a canopy hinged to starboard. This change was linked to the installation of the new KM-1 third-generation ejection seat (the canopy was no longer needed to protect the pilot during the initial ejec­tion sequence). The KM-1 was not yet a true zero-zero ejection seat because its operating range was, with the exception of altitude (0-25,000 m [0-82,000 feet]), limited by speed (130-1,200 km/h [70-648 kt]). This cockpit rearrangement led to a slight reduction of the fuel tanks’ capacity: 2,650 1 (700 US gallons) versus 2,750 1 (726 US gallons) in the PF.

So that it could be used from unprepared strips, the MiG-21PFM could be fitted with two SPRD-99 solid rocket boosters each rated at 2,450 daN (2,500 kg st). The aircraft thus possessed a complete package

of systems to improve takeoff performance (afterburner, boosters) as well as landing performance (flaps, SPS, airbrakes, PT-21UK tail chute, wheel brakes).

Armament included two air-to-air RS-2US (K-5M) semiactive radar homing missiles (leading to the installation of the RP-21M radar and a modification of the aircraft’s wiring diagram) as well as Kh-66 air-to-sur – face missiles. This weaponry could be supplemented by the GP-9 gun pod (a twin-barrel 23-mm GSh-23 cannon) under the center part of the fuselage and the ASP-PF-21 gunsight in the cockpit. The radar warning receiver was a Sirena-3M, and the new IFF interrogator had the rather curious appellation of Khrom-Nikyel ("chromium-nickel”) Before the MiG-21 PFM was ready, a small batch of MiG-21 PFSs were allotted to a fighter regiment This version differed from the PFM only in its engine which featured an additional mode of throttleable afterburning to improve significantly the aircraft’s acceleration time.

The MiG-21 PFM was mass-produced in the Gorki factory between 1964 and 1965 for the WS and in the MMZ Znamya Truda factory in Moscow between 1966 and 1968 for export.

Specifications

Span, 7.154 m (23 ft 5.7 in); fuselage length (except cone), 12 285 m (40 ft 3.7 in) height, 4.125 m (13 ft 6 4 in); wheel track, 2 787 m (9 ft 1.7 in); wheel base, 4.71 m (15 ft 5 4 in); wing area, 23 m2 (247 6 sq ft), takeoff weight, 7,820 kg (17,235 lb); max takeoff weight, 9,080 kg (20,010 lb); max takeoff weight on rough strip or metal-plank strip, 8,800 kg (19,395 lb); fuel, 2,200 kg (4,850 lb); wing loading, 340-394.8 kg/m2 (69.7-80.9 lb/sq ft); max operating limit load factor, 8.5.

Performance

Max speed, 2,230 km/h at 13,000 m (1,204 kt at 42,640 ft); max speed at sea level, 1,300 km/h (702 kt), climb rate at sea level (half internal fuel, full thrust) with two R-3S missiles, 125 m/sec (24,600 ft/ mm); climb to 18,500 m (60,680 ft) in 8 min; service ceiling, 19,000 m (62,320 ft); landing speed, 250 km/h (135 kt); range, 1,300 km (810 mi); with 800-1 (211-US gal) drop tank, 1,670 km (1,035 mi); takeoff roll, 850 m (2,790 ft); landing roll with SPS and tail chute, 550 m (1,800 ft).