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FLIGHT SAFETY FOUNDATION HELICOPTER SAFETY Preventing Dynamic Rollover(2)

时间:2012-02-24 21:03来源:蓝天飞行翻译 作者:直升机

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Lateral cyclic during takeoff has been the cause of

Occurrence of a Dynamic Rollover
numerous dynamic rollovers (or pivots about the

Depends on Four Conditions ground contact point). Taking off with tiedowns at-
tached provides a pivot at the ground attachment Four general conditions must exist for a pilot to get into point. dynamic rollover.
The most common occurrence is ground contact in

. The helicopter must be on or restrained to the deck. lateral translation. A classic case is the instructor who A wheel or skid could be in contact with the ground was demonstrating a night hover with the position
lights on flashing dim. He developed just a bit of a  point.  For rolls about some point other than the center of 
drift. The aircraft caught a skid 650 feet from the  gravity, the moment of inertia changes to become I=mr2 + 
initial hover point. The helicopter then flipped  md2, where d is the distance between the center of gravity and 
smartly onto its back.  the point of rotation. 
. The helicopter must have some angular velocity  Clearly, the moment of inertia must be greater for rolls not 
about the pivot point. That is to say, you must have  about the CG.  The helicopter still has the same maximum 
some roll rate about the pivot point.  control moment. Therefore, with a greater moment of inertia, 
full opposite stick displacement will not produce as large a roll 
. The helicopter is usually at liftoff thrust or light on  rate.  More important, the helicopter cannot arrest as large a 
the skids.  roll rate. That is the insidious part of dynamic rollover. What 
is a normal roll rate about the center of gravity may well be an 
Examine the Cause of Rollover  excessive roll rate when pivoting about a wheel or skid. The 
bottom line remains: The basic cause of dynamic rollover is 
 
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