MiG-21 evaluation in the USA

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  1. tomo pauk

    tomo pauk Creator of Interesting Threads

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  2. Timppa

    Timppa Active Member

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    #2 Timppa, Jun 20, 2016
    Last edited: Jun 20, 2016
    Some excerpts from the book "MiG-21 in Finnish Air Force" (bilingual Finnish/English)
    by Jyrki Laukkanen


    The MiG's aerodynamics are pretty straightforward; the tailed delta configuration with a thin 5% airfoil section gives good wave drag qualities at supersonic speeds.
    A good looking aircraft normally has good flying qualities. And so does the MiG-21F. Both static and dynamic stability are aerodynamically so good that no damping systems are required for any axis. This is unusual for Mach 2 fighters.

    Cockpit ergonomics are a far cry from today's pilot friendly environment. Over one hundred switches and knobs are spread all over the cockpit in an untidy manner.
    ...
    Even as we carefully studied the cockpit, some pilots still managed to arm the 30mm gun with the drag chute button and then drop the missile launch rails during landing when trying to deploy the drag chute.

    Take-off with a clean aircraft can normally be undertaken on military power only, without the afterburner. The aircraft becomes airborne after a 4,000 feet ground run. Using full reheat the MiG-21F-13 leaps into the air in less than 3,000 feet. Take-off is easy to fly as the aircraft maintains the heading almost by itself. The nose wheel is lifted off the runway at 135 knots IAS and the rotation is initiated at 175 knots. The pitch control is pleasant in rotation, and the aircraft lifts off almost by itself after rotation to 10 degrees nose up attitude.
    There is hardly any pitch trim change while retracting. If you are in a hurry to get to the stratosphere, with full afterburner the MiG accelerates very nicely in almost level flight to its best intial climb speed of 540 knots TAS. Once you have got that indicated, pull the nose up and maintain that speed. You will be climbing thru Flight Level 350 in less than two minutes. You still have the nose up so much that for leveling off it is more convenient to roll inverted and pull the nose to the horizon the half roll again instead of pushing negative G and hanging against the canopy.

    This type of climb sure gets you altitude in a hurry. But for more conservative flying 93% of N1 (low pressure compressor rpm) is recommended to save engine and fuel for climbing to the practise area. Climb initially at 390 KIAS until reaching 500KTAS. This will give you the most economic climb. The airspeed indicator has needles for both Indicated Air Speed (IAS) and True Air Speed (TAS).

    If there is a need to climb above 35,000 feet, you'd better use your basic knowledge of supersonic fighter performance. The MiG-21F-13 has a movable cone engine air intake system and variable area jet nozzle that gives you more thrust the faster you go. So if you want to go to altitudes in the region of 60,000 feet, you'd better accelerate to something like Mach 1,8 at 33,000 feet and then begin to climb. With the afterburner the kerosene is going too fast for getting much flying time. But you go to the altitude at a speed that you can not experience anything other than a supersonic jet. After this spectacular climb be prepared to return to the base because you just have burned most of your fuel.

    The MiG-21F-13 handles nicely at high supersonic speeds. Going thru the sound barrier is noticeable only by checking your pitot-static instruments as the shock wave passes thru the head of the nose mounted pitot-static tube. However, there is considerable noise at high speeds, like Mach 2.

    While descending from altitude you will be surprised to find how easy it is to maintain supersonic speed even with idle power, keeping the nose down only 10 degrees. This is due to good aerodynamics and partly to high idle rpm at altitude. Coming down from altitude with idle power burns almost no fuel at all. You will get rid of more fuel in a single go-around than you need during a descent from a distance of 100 nautical miles. So plan your approach carefully. Coming down clean is almost free ride. Going up dirty will cost you a great deal in terms of endurance.

    There is no sense in maintaining an IAS below 270 knots at any time as the induced drag begins to punish you. You begin to feel like hanging in the sky nose up and going nowhere ! Good overall speed for any flying is some 400 knots IAS. There is no angle of attack indicator in the early MiGs, so you have to hang on the IAS.

    To further reduce you airspeed requires more and more pull on the stick as the MiG is statically very stable in pitch. The aircraft handles exceptionally well at low speeds. There is enough aerodynamic control to the point where the stick is almost all the way back. There is an ample warning at slow speeds. However, sink rate near stall is spectacular and at idle power. Do you'd better practise this kind of slow flying in excess of 20 000 feet. You can safely slow down to some 110 knots IAS with the stick all the way back and still have lateral control of the aircraft, though it slowly rolls to both sides. Your landing speed will be 175 knots IAS over the threshold, so there is a lot of margin in slow speed handling on final approach and landing. Recovery from a stall is simple. Put the nose down and let it get the airspeed back to good numbers like 270 knots and you will be flying again.

    The aircraft is very spin resistant and it is hardly possible to get into any post stall gyrations without positively applying full rudder and full aft stick at high angle of attack; this makes no sense anyway. We never spun the aircraft accidentally or intentionally either. There is no need for this kind of maneuver and so no need to practise it.
    The engine spool-up time is longer than your patience. As I said, don't practise these things at circuit height. On occasion pulling the throttle back and then trying to get back to higher setting has made me feel like engine has failed. So don't do that at low altitude, because it may increase your heart rate significantly !

    The MiG-21F-13's static stability is good in any axis. The dihedral effect, or roll due to sideslip, of the swept wing delta is especially effective. Release the stick, kick half rudder and you will roll the aircraft 360 degrees very nicely in few seconds.
    Flight controls are nice and effective but not oversensitive. The pitch control operates the all-moving tailplane with a double hydraulic system with no mechanical back-up. There is a q-feel system called ARU, that changes the pitch control gearing ratio proportionally with speed and altitude. At low altitudes and high IAS the stabilizer moves less. At low IAS and high altitude it moves more with the total stick movement being the same. This prevents overcontrolling at high IAS and still gives you enough elevator power at high altitudes and slow airspeeds.

    The aileron control is very effective at normal flying speeds. Before you've got the stick to either side, the aircraft has rolled 360 degrees with you head almost hitting the other side of the canopy. The ailerons can be operated manually in case of booster system failure. With the manual control, however, the stick force is really heavy and it is for emergency use only. A better way to control the aircraft in roll in this case is to use rudder and the very positive dihedral effect. The manual rudder control forces are light at slow airspeeds but become pretty heavy at high speeds.

    The MiG-21F-13 is a straightforward aircraft to fly with pretty good performance. With adequate training and experience pilots should have no difficulty in operating it. Its systems are simple, but need the technical know-how. With proper maintenance it is also a reliable aircraft. The modern fighter technology has made the MiG-21F-13 obsolete as an effective fighting machine. But it will be one of those famous fighters in world's aviation history and has earned its place as "the Real Fighter" for the pilots who flew it in their fighter pilot's days.

    Jyrki Laukkanen
    (1285 flying hours in various MiG-21 versions.)
     
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