Posted: Sat Feb 02, 2008 12:39 am Post subject: UH-1H
I have Q about UH-1 autorotation. Manual says in chapter 9;" Should the Eng malfuction during a left bank maneuver, right cyclic input to level the helicopter must be made simultaneously with collective pitch adjustment. If the collective pitch is decrezsed without a corresponding right cyclic input, the helicopter will pitch down and the roll rate will increase rapidly, resulting in a significant loss of altitude"
So, what is the point that aircraft will roll left and nose down unless pilot roll it to right while lowering collective in this autorotation case?
If that rule does make sense (leveling helicopter as soon as engine stops during left bank maneuver) is it valid for all counter-clockwise rotating helicopters?
Joined: Aug 23, 2005 Posts: 250 Location: On a course.... golf course
Posted: Sat Feb 02, 2008 3:59 am Post subject:
I don't recall seeing this entry in the Huey manual, but it would be due to left yaw.
In flight, you are using some left pedal, depending on cruise speed, weight etc (though sometimes you might have 1" of right, due to the fin unloading the T/R) so when the engine torque stops, this pedal input will cause the nose to yaw left. You might also have some left pedal applied as you roll into the left turn, to help things along a bit. The combination of a left turn, left yaw, and the complicating aspect of a high-set tail rotor can result in a nose-down attitude. The high-set T/R would cause adverse yaw, wanting to roll you out of it, so it is hard to say how it would affect things.
Dumping the collective would also cause a left yaw if no corrective pedal was applied, though if there was no torque this would be minimal.
Would this apply to all helicopters? Remember that the Huey design dates from the 50s, so a newer design might not be so liable to yaw and roll, particularly if it didn't have a high-set tail rotor.
Thank you Ascend_Charlie, it is a confusing autorotation case, I have not been sufficiently able to figure out Why Huey is pitching down an d rolling left ? Is this described in an aerodynamics book, have you ever seen?
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