REFLECTOR: Gliding Distance

Terrence Miles terrence_miles at hotmail.com
Tue Jun 19 23:40:44 CDT 2012


I have an XL with a 300 hp Lycoming.  I presume the worse case is complete
engine stoppage at low altitude after take off while in a climb pitch-angle.
Before I push the power up at the tkof point, know what 1500 AGL is.  I use
110 kias to get to that altitude in as short a ground distance as possible
as an SOP. Otherwise I am landing within 45 degrees to current heading.
During every initial climb out, I say to myself: "push push push"  so when
if the engine up and quits I am a second or two faster lowering your nose
the big chunk it will take to establish a power off glide while I scramble
for brain power.  For serious changes in heading after 1500 AGL consider
using 45 degrees of bank and don't let your IAS increase as you feed the
bank and the rudder in.   

 

Like someone else said, pull the prop lever full out.  That's big.  Have in
your head about immediate re-start options and how.  For example, if the
prop is turning there is no need for a strarter button.   There is a good
chapter in a book by John Eckalbar entitled "Flying High Performance Singles
and Twins" that covers a lot of these related topics and all the swap offs
you would want to consider, given particulars of the event and where you are
relative to terra firma and a good set down point.  I would use 90 kts  (or
130% of stall)  for a target and work hard to stay 88 to 92.  That will get
you in the ball park of 3 DME per 1000 feet of altitude.   Get trimmed up or
you will have double the airspeed / glide distance vacillations and further
muddle any attempt of trying to multiple/divide beyond the basic 3 to 1.
Besides even that takes away attention on more important matters.   Look out
the window.  When on speed, the aim point on the windscreen is where you are
headed.   (Just my two cents)  I did all that glide testing in my first 40
hours and never came up with the same thing twice, since every day there was
a wind of some kind, and I was at idle power not engine out.  

Just my two cents,

Terry

 

From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of Brooke Wolf
Sent: Tuesday, June 19, 2012 9:51 PM
To: reflector at tvbf.org
Subject: REFLECTOR: Gliding Distance

 

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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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  <mailto:john at velocityaircraft.com>
<john at velocityaircraft.com>
To: 'Velocity Aircraft Owners and Builders list'
<mailto:reflector at tvbf.org> <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
> 
> 

 


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