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Bill, having made 3 engine out landings, I can tell you
that it depends on your airspeed. In my case, with the both the 2.17 and
2.85 my prop continued to windmill with the airspeed above 110 mph - however,
that was not my best glide speed. So when I slowed it down to 87 mph for
best glide, the prop in both cases was no longer windmilling - which was good as
that reduced drag.
Regarding hand prop of the rotary - at least using Tracy
Crooks EC - you simply can't do it. The computer expects to see at least 2
revolutions of the prop at or above 150 rpm (value last time I talked to Tracy
about it-it might be slightly lower limit now) before it will activate the
ignition. I just don't think you're going to able to spin it at that rate
for two prop revs by hand.
Ed
Sent: Sunday, August 22, 2010 1:23 PM
Subject: [FlyRotary] Re: Prop orientation with TDC
Can some of you more
“experienced” folks tell me..does the prop windmill after the engine quits, or
does it stop rotating?
Bill
B
From:
Rotary motors in aircraft
[mailto:flyrotary@lancaironline.net] On
Behalf Of Lehanover@aol.com
Sent: Sunday, August 22, 2010 11:29
AM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: Prop orientation
with TDC
In a message dated
8/22/2010 10:28:20 A.M. Eastern Standard Time, blake.lewis@gmail.com
writes:
On Sat, Aug 21, 2010
at 7:34 AM, Jeff Whaley <jwhaley@datacast.com> wrote:
> What is
the Rotaries best prop orientation at the prop flange relative to TDC?
>
The Lycomings are typically entering the compression stroke at 11-10 o'clock
and 5-4 o'clock.
> The 13B goes through 3 compression strokes per
e-shaft revolution - does this predicate a 3-bladed prop is the ideal
match?
> Jeff
The orientation idea
comes from the older 4 cylinder airplane engines that had to be hand started. So
the position of the blade made a difference in that the person starting the
engine needed a good body position to start out. It was also a good idea,
because in the event of an engine stoppage, that very same position had the prop
near horizontal, and that kept a blade from digging in on landing.
In the rotary powered
craft, the engine will be at TDC twice per crank shaft rotation (for a two
rotor) so, 2 times the reduction ratio tells you how many times it gets to TDC
per propeller revolution. 3 times for a 3 rotor, and 4 times for a 4 rotor.
A 2 rotor with a
2.78:1 reduction unit will see TDC 2 X 2.78 = 5.56 or about every 65 degrees of
prop rotation.
This suggests that
hand propping might be more difficult because of the mechanical disadvantage of
the reduction unit, and should the engine fire, the length of time available to
remove your hand might be very short, should the very next rotor face fire as
well.
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