REFLECTOR: Gliding Distance

John Abraham john at velocityaircraft.com
Wed Jun 20 05:21:00 CDT 2012


Brooke

You can practice zero thrust with different power settings. There are a couple MP setting you can use 11-15". After you have that set, begin to pull the propeller back until you feel the plane slide you off your seat forward a little and note the RPM that it happens at. It will be different RPMs for different MP. I think a 260hp XL we used around 11" and 2200-2300rpm. I learned this from Len Fox when we were working with rocket racing who has an extensive test pilot background. 



On Jun 19, 2012, at 10:50 PM, Brooke Wolf <bwolf1 at tds.net> wrote:

> Mark
> 
> I'm with you!  All I want to know is…."When my engine quits at 5000 AGL, how many no wind miles can I glide?".  I tend to think of altitude in feet and distance in miles.  Different pilots have different ways of thinking about this.  I prefer to think about it in terms of "How many miles can I go per thousand feet of altitude".  Most every airplane I have flown has been "3 to 1".  As you know that doesn't mean 3:1 glide ratio…it means I can go 3 miles for every 1000 ft altitude.  Other pilots think in terms of actual glide ratio i.e. "18:1" which is exactly 3 to 1.  Got you confused yet?  It is all in semantics.  It is important to get the semantics right so that we are all on the same page.
> 
> Lets keep this discussion going.  How far can YOU glide in your suddenly unpowered Velocity from 5000 feet (no wind of course!
> 
> Your Phantom could only glide 5NM (30,000 ft)  from 10000 feet?   Man that thing was a brick!!  The closest thing I can relate to is the T-38.  All I remember about it was that L/Dmax was 240KIAS.  Can't remember the glide ratio.  Too many dead brain cells.
> 
> Brooke
> 
>  
> 
> 
>> 
>> 
>> From: Mark Magee <edjonesbrady at gmail.com>
>> Subject: Re: REFLECTOR: Gliding Distance
>> Date: June 19, 2012 9:40:33 PM EDT
>> To: Velocity Aircraft Owners and Builders list <reflector at tvbf.org>
>> Reply-To: Velocity Aircraft Owners and Builders list <reflector at tvbf.org>
>> 
>> 
>> You boys got me all confused here? Glide ratio: Three to One (F-4 Phantom II), at Best Glide speed airplane goes three feet forward and goes down 1 foot. Three to One Glide Ratio. You guys are throwing in some trigonometry that's confusing (possibly frightening) folks? At 10,000' AGL an F4 Phantom II in flameout at best glide has a 30,000 ft 'cone' below it at which touchdown (or ejection) will occur. Turns lessen the Three to One.
>> Fairly simple: if an XLFG clean and stopped prop does a 15 to 1 glide ratio, then at 10,000' AGL, I have a 150,000'  'cone' below me inside which my wheels will touch down, turns diminishing the cone. Airplane moves 15 feet forward, and falls 1 foot. 15 to 1 glide ratio.
>> Fairly simple.
>> 
>> Mark B. Magee
>> PS (F-4 Phantom II was a template subject of my flight training: proof that with enough thrust a lead brick can fly!)
>> 
>> On Tue, Jun 19, 2012 at 7:34 PM, Brooke Wolf <bwolf1 at tds.net> wrote:
>> Tom
>> 
>> I was using the aviation standard of 6000ft/nautical mile. Admittedly, it is more like 6076 feet.  Anyway, using 6000 ft., 1.41 nautical miles is 8460 ft.  Hence, 8.4:1 glide ratio.  Man…I like this stuff.  Great discussion!  Keep it up.
>> 
>> Brooke
>> 
>>  
>>> 
>>> 
>>> From: Tom Falls <tomfalls6 at gmail.com>
>>> Subject: Re: REFLECTOR: Reflector Digest, Vol 87, Issue 104
>>> Date: June 19, 2012 6:40:02 PM EDT
>>> To: Velocity Aircraft Owners and Builders list <reflector at tvbf.org>
>>> Reply-To: Velocity Aircraft Owners and Builders list <reflector at tvbf.org>
>>> 
>>> 
>>> Correct me if I'm wrong but I think Brooke got 7.4:1 (1.41 miles is 7445 ft/1000). And John Abraham is worse at 5.4:1 to 6:1 (2.5-2.8 nm is 15,190 to 17,000 ft. Divide that by 2800).
>>> 
>>> Tom
>>> 
>>> Sent from my iPad
>>> 
>>> On Jun 19, 2012, at 5:07 PM, Mark Magee <edjonesbrady at gmail.com> wrote:
>>> 
>>>> Hi John,
>>>> What was your speed, do you recall?
>>>> Is Glide Ratio similar for XLFG as to XLRG gear up?
>>>> 
>>>> Mark
>>>> 
>>>> On Tue, Jun 19, 2012 at 2:46 PM, John Abraham <john at velocityaircraft.com> wrote:
>>>> You should see around 15:1 +/- for building variations with a zero thrust setting and gear up.  I have done a 2.5-2.75 NM glide from 2800 feet back to the runway with a windmilling propeller on an XL before.  (yes engine was out so no additional thrust)  best glide airspeed is 85KCAS at gross.  So L/D will decrease if you are lighter slightly. We cleared the fence by about 5’ or so. 
>>>> 
>>>>  
>>>> 
>>>>                       John
>>>> 
>>>>  
>>>> 
>>>> From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On Behalf Of Mark Magee
>>>> Sent: Tuesday, June 19, 2012 2:56 PM
>>>> 
>>>> 
>>>> To: Velocity Aircraft Owners and Builders list
>>>> Subject: Re: REFLECTOR: Reflector Digest, Vol 87, Issue 104
>>>> 
>>>>  
>>>> 
>>>> I don't have the manual here at work, is the XLFG a 12 to 1 glide ratio with a stopped prop?
>>>> 
>>>> 
>>>> Old Long EZ glided 20 to1 on a stopped prop.
>>>> I told myself I'd never fly the heavies... :(
>>>> Mark Magee
>>>> 
>>>> On Tue, Jun 19, 2012 at 12:44 PM, Brooke Wolf <bwolf1 at tds.net> wrote:
>>>> 
>>>> Steve….Just to be clear, do you mean 9.5 to 1, i.e., 9500 feet forward for every 1000 ft altitude loss?  It looks like mine is nearer 8.5 to 1.  Somehow, somewhere I got the idea it would be 15 to 1!  Maybe that is with a stopped prop.  
>>>> 
>>>>  
>>>> 
>>>> Brooke
>>>> 
>>>>  
>>>> 
>>>>  
>>>> 
>>>>  
>>>> 
>>>> 
>>>> 
>>>> 
>>>> From: steve korney <s_korney at hotmail.com>
>>>> 
>>>> Subject: Re: REFLECTOR: Gliding Distance
>>>> 
>>>> Date: June 19, 2012 1:13:22 PM EDT
>>>> 
>>>> To: Reflector Reflector <reflector at tvbf.org>
>>>> 
>>>> Reply-To: Velocity Aircraft Owners and Builders list <reflector at tvbf.org>
>>>> 
>>>>  
>>>> 
>>>> 
>>>> At 85 KIAS @ 6000ft , you have about a 9.5 glide ratio.... What are you expecting to see....?
>>>> 
>>>> 
>>>> Steve 
>>>> 
>>>> > From: bwolf1 at tds.net
>>>> > Date: Tue, 19 Jun 2012 12:26:23 -0400
>>>> > To: reflector at tvbf.org
>>>> > Subject: REFLECTOR: Gliding Distance
>>>> > 
>>>> > 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
>>>> > 
>>>> > 
>>>> > _______________________________________________
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>>>> > 
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>>>> 
>>>> 
>>>> 
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>>>>  
>>>> 
>>>> 
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>>>>  
>>>> 
>>>> No virus found in this message.
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>>>> 
>>>> 
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>>>> 
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>>> 
>>> 
>>> 
>>> 
>>> From: Scott Derrick <scott at tnstaafl.net>
>>> Subject: Re: REFLECTOR: Reflector Digest, Vol 87, Issue 104
>>> Date: June 19, 2012 6:50:49 PM EDT
>>> To: Velocity Aircraft Owners and Builders list <reflector at tvbf.org>
>>> Reply-To: Velocity Aircraft Owners and Builders list <reflector at tvbf.org>
>>> 
>>> 
>>> That sounds way to exciting John!
>>> 
>>> -------- Original Message --------
>>> Subject: Re: REFLECTOR: Reflector Digest, Vol 87, Issue 104
>>> From: John Abraham <john at velocityaircraft.com>
>>> To: 'Velocity Aircraft Owners and Builders list' <reflector at tvbf.org>
>>> Date: 06/19/2012 01:46 PM
>>>> You should see around 15:1 +/- for building variations with a zero thrust setting and gear up.  I have done a 2.5-2.75 NM glide from 2800 feet back to the runway with a windmilling propeller on an XL before.  (yes engine was out so no additional thrust)  best glide airspeed is 85KCAS at gross.  So L/D will decrease if you are lighter slightly. We cleared the fence by about 5’ or so. 
>>>> 
>>>>  
>>>> 
>>>>                       John
>>>> 
>>>>  
>>>> 
>>>> From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On Behalf Of Mark Magee
>>>> Sent: Tuesday, June 19, 2012 2:56 PM
>>>> To: Velocity Aircraft Owners and Builders list
>>>> Subject: Re: REFLECTOR: Reflector Digest, Vol 87, Issue 104
>>>> 
>>>>  
>>>> 
>>>> I don't have the manual here at work, is the XLFG a 12 to 1 glide ratio with a stopped prop?
>>>> Old Long EZ glided 20 to1 on a stopped prop.
>>>> I told myself I'd never fly the heavies... :(
>>>> Mark Magee
>>>> 
>>>> On Tue, Jun 19, 2012 at 12:44 PM, Brooke Wolf <bwolf1 at tds.net> wrote:
>>>> 
>>>> Steve….Just to be clear, do you mean 9.5 to 1, i.e., 9500 feet forward for every 1000 ft altitude loss?  It looks like mine is nearer 8.5 to 1.  Somehow, somewhere I got the idea it would be 15 to 1!  Maybe that is with a stopped prop.  
>>>> 
>>>>  
>>>> 
>>>> Brooke
>>>> 
>>>>  
>>>> 
>>>>  
>>>> 
>>>>  
>>>> 
>>>> 
>>>> 
>>>> 
>>>> From: steve korney <s_korney at hotmail.com>
>>>> 
>>>> Subject: Re: REFLECTOR: Gliding Distance
>>>> 
>>>> Date: June 19, 2012 1:13:22 PM EDT
>>>> 
>>>> To: Reflector Reflector <reflector at tvbf.org>
>>>> 
>>>> Reply-To: Velocity Aircraft Owners and Builders list <reflector at tvbf.org>
>>>> 
>>>>  
>>>> 
>>>> 
>>>> At 85 KIAS @ 6000ft , you have about a 9.5 glide ratio.... What are you expecting to see....?
>>>> 
>>>> 
>>>> Steve 
>>>> 
>>>> > From: bwolf1 at tds.net
>>>> > Date: Tue, 19 Jun 2012 12:26:23 -0400
>>>> > To: reflector at tvbf.org
>>>> > Subject: REFLECTOR: Gliding Distance
>>>> > 
>>>> > 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
>>>> > 
>>>> > 
>>>> 
>> 
>> 
>> _______________________________________________
>> To change your email address, visit http://www.tvbf.org/mailman/listinfo/reflector
>> 
>> Visit the gallery!  www.tvbf.org/gallery
>> user:pw = tvbf:jamaicangoose
>> Check new archives: www.tvbf.org/pipermail
>> Check old archives: http://www.tvbf.org/archives/velocity/maillist.html
>> 
>> 
>> 
>> _______________________________________________
>> Visit the gallery!  tvbf:jamaicangoose
> 
> _______________________________________________
> To change your email address, visit http://www.tvbf.org/mailman/listinfo/reflector
> 
> Visit the gallery!  www.tvbf.org/gallery
> user:pw = tvbf:jamaicangoose
> Check new archives: www.tvbf.org/pipermail
> Check old archives: http://www.tvbf.org/archives/velocity/maillist.html
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