Message-ID: <00d801c349a6$b419e2e0$1702a8c0@WorkGroup>
From: "Ed Anderson" <eanderson@carolina.rr.com>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
References: <list-2473818@logan.com>
Subject: Re: [FlyRotary] Re: Engine Failure Report from Chuck Dunlap
Date: Sun, 13 Jul 2003 21:24:42 -0400
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> > First inflight engine failure of a
> > rotary engine I am aware of.  Sounds like apex seal went or foreign
object
> > was injested.
>
> I thought the engine was supposed to run on one rotor. Rought, but enough
to
> keep you airborne was what I'd read somewhere.
> John Slade
>
>
That probably depends on several factors, John.  One is the failure mode, if
only one apex seal fails (and fails completely) you would lose the power (or
most of it) from two of the three faces of the rotor.  More drastic failure
than that may take out all the apex seals thereby reducing you to power of
only one rotor will really cause some pretty heavy shaking of the aircraft
and of course power lost.  Some folks assume that losing one rotor means
losing 1/2 power, but that is not necessarily the case.  If you lost one
rotor and could maintain the airflow through the engine with the same prop
load that the two rotor provided then you would have 1/2 power available.
But, once you lose one rotor (and assuming you don't have a variable pitch
prop the load remains unchanged), the rpm, and therefore the airflow drops
off to less than 1/2 the airflow of two rotors, so the remaining rotor can
not maintain even 1/2 the power.  My best guess is that you might retain
approx 1/3 the power of two functioning rotor with a single rotor running.

I must admit I was somewhat surprised at first to hear that even with 3900
rpm (assuming it stayed at that), Chuck was not able to maintain altitude.
But, then at 12000 MSL power would have been way down with two good rotors
and I don't know - but I assume that the airport he was aiming for was at
least 5000 MSL in that region around Grandcanyon and it is summertime there
so the density altitude was probably considerably higher than that.  Since
Chuck was flying north to the Arlington flyin, I would assume he had his
usual camping gear and in other words the aircraft was probably fairly
heavily loaded.  So given all those factors, it sounds like his flight
required more power than the damaged engine could deliver under those
conditions..

Another way to look at it, is that the engine did produce sufficient power
long enough to get him almost the 21 miles toward an airport.  Had this
happend in many parts of the country (such as back here in North Carolina
(and he at 12000 msl) he would have probably easily had made an airport.  It
did apparently get him to a suitable emergency landing spot on the highway.
Most reciprocating engines that lost 1/2 of its cylinders to engine damage
would have most like quit running immediately.

I can maintain level flight in the pattern with 3200 rpm, but that is near
sea level (1600 MSL)  which is of course not the same conditions that Chuck
was faced with.  So even though the single rotor was not able to maintain
flight, you might consider that it kept him airborn long enough for other
alternatives.

Just my opinion of course.

Best Regards

Ed Anderson