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Old 17th August 2003 | 13:52
  #1069 (permalink)  
NickLappos
 
Joined: Apr 2003
Posts: 3,012
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From: USA
Having done one heck of a lot of structural flying, I can assure you that if you take a helicopter and often make banked turns, even smooth ones, you will be building fatigue cycles on the machine. Depending on the assumed usage spectrum, you should expect the rotating components to need replacement/ovrhaul earlier than planned. For most Sikorsky aircraft, we strive to make it so that the components see no fatigue damage while in level flight, but virtually all accrue fatigue damage while in turns, decels and accels.

This is a fact of the physics of how the rotor experiences progressive blade stall.

Those of us who are in relatively constant maneuvering flight, even when flown smoothly and well, should expect that their components must be inspected more often, and replaced sooner than the Chapter 4 maintenance manual recommendations.

Here is a web site that describes the typical times spent in each maneuver state, according to the FAA Advisory Circular. Note that they allow only 6% of the total flight time for turns, which is 3.6 minutes per hour. I will bet dollars to donuts that mustering cattle takes a few more turns than that, unless they are wonderfully obedient cows!

http://www.s-92heliport.com/fatigue.htm

I a few days, I will try to post some data on how the rotor develops the stresses in maneuvers.

Last edited by NickLappos; 17th August 2003 at 14:41.
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