TM 1-1520-240-109-1-6 9-1-10. Dual Engine Failure.CAUTIONJettison external cargo as soon as possibleafter engine failure. This will help to preventdamage to the helicopter during touchdownand will reduce weight and drag, therebyimproving autorotational performance.a. Low Altitude / Low Airspeed. When both enginesfail at low altitude and low airspeed, sufficient altitude isnot available to increase RRPM. Establish the bestautorotational airspeed, jettison external cargo (ifapplicable), and decelerate effectively prior totouchdown. Initial thrust reduction will vary from noreduction at zero airspeed below 20 feet to full reductionat higher airspeeds and altitudes. Attempt to maintain atleast 96 percent.b. Cruise. c. In cruise flights up to Vne, reducethrust immediately to full down position to regain RRPM.Adjust cyclic pressure as necessary to maintain the re-quired airspeed. The Autorotation Approach Corridor,figure 9-1-8, presents those combinations of airspeedsand wheel heights from which a safe autorotatiive landingmay be made following a second engine failure. Autorotativeapproaches are recommended in the caution area. At highgross weights, the rotor may tend to overspeed and mayrequire thrust application to maintain RPM below the upperlimit. Thrust should never be applied to reduce RPM forextending glide distance because this reduces RPM avail-able for use during touchdown. When both engines fail atcruise, proceed as follows:CAUTIONThe helicopter must be maneuvered intothe autorotation approach corridor priorto landing to assure a safe outcome of themaneuver.1. AUTOROTATE.2. Externalcargo—Jettison.3. ALTswitch—Disengage.9-1-11. Single Engine Failure.The action taken after one engine fails will depend onaltitude, airspeed, phase of flight, areas available forlanding, and S/E capability of the helicopter. Immediatelyafter any engine malfunction, the flight engineer shouldcheck the engine for the possibility of fire. If required,external cargo should be jettisoned as soon as possibleafter engine failure. This will help to prevent damage tothe helicopter during touchdown and will reduce weightand drag, thereby improving S/E performance.Thrust control adjustments will depend on altitude at thetime of engine failure. For example, at (HIGE) below 20feet, maintain thrust control position as the operativeengine beep trim is increased. At a hover above 20 feet,thrust should be lowered slightly to maintain at least 96percent RRPM. If altitude permits, thrust may be loweredsufficiently to maintain normal RRPM.Cyclic inputs will depend on altitude and airspeed. At a(HIGE), the helicopter should be maintained in a hover-ing attitude. in forward flight, at low altitude (below 50feet), when S/E flight is not possible a decelerating atti-tude should be assumed to dissipate airspeed and aid incushioning the helicopter. If airspeed is slow and altitudepermits, the helicopter should be placed in an accelerat-ing attitude of up to 30_ nose-low to gain airspeed as theoperative engine beep trim is increased. This nose-lowattitude should not be used at extremely low alttiudebecause of reduced reaction time, R/D, and the responseof the helicopter. Any time the helicopter assumes a de-celerating attitude in close proximity to the ground, avoidrotating the aft gear into the ground at touchdown.
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