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E'Rechlin
Eval. No. 90014
Evaluation of the Russian fighter aircraft La 5 with double-row radial, fuel-injected engine M 82 FNW
Final Report
Page 3
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2.) P r o p e r t i e s

Pilot's seat:

The pilot's seat is convenient. The view to the front is adequate, though heavily obscured by the twin-row radial engine at take-off, when landing and during taxying. On the ground and during flight exhaust fumes are very troublesome. The oxygen equipment apparently had never been used. It exhibited excessive leaking. It's patterned after the German oxygen equipment. Actuators and controls for propeller pitch, radiator, gills, trim etc. mostly consist of Bowden cables and control cables, creating much lost motion and weak, soft control.

Take-off:

A tendency to swing is existent as normal for the engine power, but can be controlled. One has to raise the tail wheel only slowly and not too early. The small ground clearance of the propeller has to be taken into account for that. Acceleration is good, the take-off run is relatively short (flaps 15 to 20 degrees). Elevator and rudder trim have to be set to their correct positions with care, as there's no trim indicator available.

Stability, control forces and effectiveness:

In the normal angle-of-attack range, with gear and flaps "up" as well as "down", directional stability is surprisingly good even in a full power climb, the elevator forces are normal. In steep turns, elevator forces are clearly positive and fairly high, so that for longer durations trim changes are advisable.

Directional static stability is present at normal rudder forces, which rapidly decrease in slow flight. At the same time, rudder effectiveness decreases, too. Directional dynamic stability is slight, with poor damping. Oscillations cease only slowly. However, the oscillation period (at 450 km/h IAS at H=2000 m about 3 s) is not so short that it would be impossible to immediately stop the oscillation by control inputs. Gunnery runs are well possible. [Original sentence above my head, translation attempt follows: "Rudder-induced roll is slight. Rudder-induced yaw is present, but not particularly troublesome."] Aileron-induced yaw is slight and negative, but not troublesome due to the good directional stability, and it can be compensated by small rudder deflections.

Aileron effectiveness is excellent. At 450 km/h IAS the time for a roll is hardly 4 s. At 600 km/h IAS the aileron forces just allow high control deflection speeds. In yaw the stick neutral position moves noticably.

Stalling:

At rated power, flaps and gear "up": At 210 to 200 km/h IAS, the slats deploy, the aileron forces decrease to the point of reversal. At 180 km/h IAS, roll damping appears to vanish. In yawed flight or at lower airspeed the aircraft rolls onto one wing. Without power, with gear and flaps "down" the same symptoms are encountered at similar airspeed indications. Pulling back the stick further, the elevator becomes forceless or even reversed immediately, its effectiveness almost vanishes. At the resulting very high angles of attack, the aircraft rolls onto one wing.

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E'Rechlin
Eval. No. 90014
Evaluation of the Russian fighter aircraft La 5 with double-row radial, fuel-injected engine M 82 FNW
Final Report
Page 4
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The accelerated stall from a banked turn with power applied results in similar symptoms, but the aileron reversal is much more noticeable, and occurs at relatively high speeds. For example, at H=2400 m [text missing in original ...] and 2.6 G equivalent to 67 degrees bank and 30-s-circle [...] force reversal present at and a slightly lower airspeed, respectively [...] the slats already extend. This flight status is hardly convenient.

[...] so one is forced to apply aileron inputs. When this happens, the stick displays the tendency to move to the cockpit wall. At least [...] is dangerous, since even after extension [...] still an angle-of-attack margin before stall present [...] troublesome aileron reversal can the shortest times for circling be achieved [...] performance at this altitude at about 28 to 30 s for the stationary full circle without altitude change. This is equivalent to a shortest time for a full circle at emergency power and 1000 m of about 25 s.

Landing:

Apprach at 200 km/h IAS and only with throttle applied. It's advisable to trim out the aircraft since the elevator control forces have to be reckoned with in the flare. It is possible to flare the aircraft to a three-point attitude and touch down perfectly. If that fails however, or if the ground is uneven, the poor stalling characteristics come into play, helped by the poor gear oleo damping. The aircraft quickly rises above three-point attitude, elevator control forces vanish and reversal occurs, and the effectiveness of the elevator that is blanketed by the wing afterwards hardly suffices to influence the "galloping" that follows. Due to the small ground clearance, the propeller is especially endangered. If during galloping greater angles-of-attack occur, the aircraft banks away, which due to the wide-track landing gear isn't tragic. In crosswind, the rudder effectiveness is insufficient to prevent a swing, so one has to rely on the help of the pneumatic hand brake.

Tactical conclusions and suggestions:

The La 5 is according to its engine power especially designed for combat at low altitude. Its top speed at ground level is very close to that of the 8-190 and the 8-109 (each at emergency power). The 8-109 with MW 50 is in the entire range superior in top speed and best climb. The relative acceleration should be similar. The aileron effectiveness is better than that of the 8-109. The times for a full circle are better than those of the 8-190 at ground level and worse than those of the 8-109. Even at the best climb, the 8-190 is inferior at up to about 3 km altitude. Due to its higher weight, the 8-190 accelerates slower, but is superior in all descending and diving situations and in shallow high-speed climbs. Except for sudden jinks to evade, diving attacks (comparison to Thunderbolt) followed by shallow high-speed climbs to get into a new position to attack (at IAS of best climb, the La 5 climbs at a steeper angle) are appropriate for the higher weight and higher wing loading of the 8-190, as well as not giving up airspeed and avoiding protracted turning fights, since one shouldn't assume that the Russians who are used to worse handling characteristics will be impressed by the aforementioned [troublesome] turning characteristics of the La 5. The short endurance of about 40 min at rated power, that decreases further if supercharger high gear is engaged, deserves special mention.