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Old 17th Sep 2017, 10:43
  #53 (permalink)  
Join Date: Jan 2009
Location: Sweden
Age: 52
Posts: 158
Friction in freewheeling unit

The story of high friction in the freewheeling unit can't be true.
Some, low friction yes of course.

Long time, but I still remember the MR continue to turn forever after engine is shut down and you walk away from the 300. It would'nt ever stop. If there was anything more than 'almost no friction' the stopped engine would effectively act as a rotorbrake, and stop the MR.

For twin engine helos with NG-oriented idle, when selecting one engine to idle( the other engine in flight) the free turbine of the idle-ing one would be driven backwards via the freewheeling unit and show a lot higher NF when MR at 100% than when both engines at idle. But it doesnt, on the types i flown. When selecting idle on one, the NF reduces for example to around 70%, when the other engine is selected to idle, and NR decays, it still show the same number until rotor is driven by both eng on idle(a small reduction of nf caused bu the load of the drive line of course).

Was you guys ever shown a freewheeling unit bu the flight engineers in basic traning? Was allowed to turn it both ways? Remember any significant amount of torque when turning it the frewheeling direction? I don't.
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