REFLECTOR: Reflector Digest, Vol 87, Issue 110

[Brooke Wolf]

Scott,

Great idea.  I will try it and let you know.  I do have a couple of questions.  

1.  In flat pitch at idle power, it seems that the prop would be driving the engine.  If I pull the prop all the way back to a more coarse pitch, the engine may drive the prop.  Am I right in these assumptions?

2.  Is there anything I need to be cautious of in pulling the prop all the way back during inflight idle operation?  Any undue stress on the engine?  How about return to normal operation?

3.  I would be interested in finding out how to determine the "zero thrust" prop pitch setting.  This setting would better define glide performance. Any ideas?

Thanks

Brooke (neophyte piston pilot)

> 
> 
> Brooke,
> I encourage you to do some more power off glide tests, this time however bringing the propeller control all the way back to low RPM. The difference in glide performance is amazing. It's like an automobile going into overdrive! Do this at an altitude where you can bring the propeller back to normal RPM slooooowly during the transition back to normal flight operations. A lightly loaded XL should give a 14:1 (or better!) power off glide ratio. Looking forward to you next report!
> Scott B.
> 
> On 6/19/2012 12:26 PM, Brooke Wolf wrote:
>> I am planning some overwater trips in the near future and the subject of gliding distance naturally comes to mind.  I have done some limited test flying with my airplane (XLRG w/Aerocomposite variable pitch prop).  The results of my gliding performance are not too good.  All tests were done around 6000ft with throttle at idle and wheels up.  Here are the results:
>> 
>> 80 KIAS - 900fpm…….. yields a glide performance of 1.38 miles/1000 ft altitude
>> 85 KIAS - 1000fpm……..yeilds a glide performance of 1.41 miles/1000 ft altitude
>> 100 KIAS - 1250fpm …..yields a glide performance of  1.34 miles/1000 ft altitude
>> 
>> As you can see, 85 KIAS appears to be the best glide speed.
>> 
>> I know there may be a big difference in what I tested and what happens in the real world with a windmilling or stopped prop.  Have any of you brave test pilots done any testing with a windmilling or stopped prop?  What were the results?  What kind of glide performance did others get with throttle at idle?  Is there anyway to correlate throttle idle glide performance with windmilling or prop stopped performance?  What is the best way to stretch a wheels up glide on a Velocity?
>> 
>> I would like to get a discussion going on this and find what others have experienced.  Thanks.
>> 
>> Brooke, N108BG, XLRG-5, 145 hours
>> 
>> 
>> _______________________________________________