Here is a little safety trick for all you guys with
GPS.  This is particularly important for all of us
doing non aircraft engine installations.

Climb up to about 5000 feet AGL over your air port
and kill the engine. Note how far you can glide

from the GPS

data for a 1000 foot decent at best glide speed

in a straight

line.

Then do the same for two 90 degree turns. This

will give you a

feel for altitude loss as a function of distance

when making

dead stick landings. It would help if you have

your landing

field lat longs in a way point in your GPS just

in case. this

will give you a glide ratio for your particular airplane
rather than assuming it is the standard for light

planes of

around 7:1.

It would be great if Greg Richter allowed

specific glide ratio

data to be entered into his moving map program.

If your engine

quit your moving map program could then tell you

if you could

make it to a particular emergency landing field.

Assuming of

course the lat longs are in his moving map program for all
possible landing fields.

Paul Lamar

Good idea.   I was surprised at how much the glide ratio
deteriorated with the engine stopped.   I had

assumed the prop

was generating about the same drag at engine idle as engine
stopped.  Had 600 - 700 fpm sink rate at idle and

900 fpm with

engine dead.  My Anywhere Map GPS (running on Ipaq)

shows cone

of safety around airports when you plug in your glide ratio.

Tracy Crook
tcrook@rotaryaviation.com
www.rotaryaviation.com

Could this be a result of having a fairly high pitch prop
which is still producing some thrust at idle? The CAFE test
guys go to extreme lengths to zero out thrust by measuring
fore/aft position of the crankshaft (centering it within its
possible end-play) while actually adding power above idle
rpm when they do their glide ratio measurements. If the
engine is not running at all, then a stopped prop should
have less drag than a windmilling prop. For an analogy,
consider a gyroplane with rotating vs. stopped rotor.

Windmilling might be a moot point with wood props &
reduction drives, but if you fly a conventional a/c engine,
it's good to remember how to get max glide if it quits.

Charlie England

The problem with high pitch props extending the landing

task has been pointed out

by others.  This is the reason that a low idle speed is

important with a fixed pitch

prop.  The high pitch that we are dealing with will still

produce measurable amounts

of thrust.  Note that the 2.85 ratio redrive is an

advantage here because of the

slower prop speed when the engine is at idle.  This has

caused me some concern

since PP motors are not known for their smooth idling

characteristics.  However, it

appears that if the throttles are located next to the rotor

housing on a PP motor that

the idle will be acceptable.  It is completely unknown if

the redrive will have any

objections to the low RPM - seems likely that there will be

a idle speed limit due to

harmonics with the engine/redrive combination (This

probably isn't stated exactly

right from an engineering view, but this seems to describe

what most people have

described).  I should have answers to these questions before I fly.

Ken Powell
RV-4
(Hope to fly in this lifetime!!!)
Flying in this Life Time (Ihope!!!)

I am not sure but I would not be a bit surprised if the prop just
stops. Kind of hard to rotate the engine 2.17 times as fast as the
prop from air pressure alone. Perhaps in a dive.
The 2.85:1 might be even more difficult.

In any event if it does not stop you could pull up and you
may be able
to stop the prop if there is no possibility of restarting the
engine.
To reduce drag and extend your glide.
If the engine idles only and does not respond to the throttle I would
say that is a rather rare failure mode. These should be things you
should find out about in early testing with plenty of altitude.
Perhaps Tracy or someone else flying can do these tests for us.

Paul Lamar

 I shut off my engine one time (at altitude over the airport) and reduced
speed to best glide speed and the engine kept turning. I had to slow it down
almost to stall speed to make it stop. Once stopped, I had to increase speed
to maybe 130 MPH to restart the engine without the starter. I agree everyone
should try this under safe, controlled conditions one time, just to reduce
the unknowns if the unthinkable happens.

Chuck Dunlap
Wood prop, 13B engine, RV-6

 
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