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Date: Mon, 15 Oct 2007 19:41:27 -0400
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From: Tom Thibault <tthibaultsprint@earthlink.net>
Reply-To: Tom Thibault <tthibaultsprint@earthlink.net>
Subject: RE: prop drag
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Another data point (perhaps not relevant to Lancairs).

A friend flying an RV-7 just recently had a total engine seizure while in flight and, thank God, dead sticked to a nearby runway without airframe damage or any injury.  Well, maybe he and wife Pam needed new shorts!

His description of the incident lists a descent rate of ~1,400 FPM during the glide.  That RV has a 180 HP Lyc IO-360 with Hartzell CS prop.  By comparison, my LNC2, with the same engine prop combination, obtains an idle power ~500 FPM descent rate in full coarse pitch and ~1,500 FPM in fine pitch.

Is it surprising to anyone that a stopped, coarse pitch prop in an RV would result in such a large descent rate?  I would have expected that the RVs stopped prop descent rate would be much closer to an LNC2 with a windmilling coarse pitch prop.  If his experience is normal for an RV, does that mean a windmilling fine pitch descent would be 3,000 FPM or more in an RV?

Any thoughts?

Tom Thibault