Best glide speed
Joined: Sep 2004
Posts: 43
Likes: 0
From: UK
Hi Tinstaafl,
I daren't speak for everybody but personally I would find it harder maintaining alt with the speed bleeding off than sticking it 10 deg nose up until Vmd.
Regarding the options, again I beg to differ. If you are higher you are higher - even 5' is the difference between clearing a hedge and not. Unless you have the sea or a mountain range behind you or you are completely alert as to the best place to put down before it goes "phut" (virtually never in my case) then, in my book higher is better.
I'm doing PFLs next week on my CPL so I'm keen to see how that is taught.
I guess we can beat this subject to death without getting anywhere. I hope that we haven't muddied the waters too much for Vee One!
I daren't speak for everybody but personally I would find it harder maintaining alt with the speed bleeding off than sticking it 10 deg nose up until Vmd.
Regarding the options, again I beg to differ. If you are higher you are higher - even 5' is the difference between clearing a hedge and not. Unless you have the sea or a mountain range behind you or you are completely alert as to the best place to put down before it goes "phut" (virtually never in my case) then, in my book higher is better.
I'm doing PFLs next week on my CPL so I'm keen to see how that is taught.
I guess we can beat this subject to death without getting anywhere. I hope that we haven't muddied the waters too much for Vee One!
Thread Starter
Super-Friendly Aviator
Joined: Jun 2004
Posts: 424
Likes: 0
From: Reigate, UK
No, not muddied. Very useful discussion - it means I (and others) can make up their mind what is best in a certain situation with more fact/informed opinion to go on...can't be bad.
Had my second lesson of the PPL on Saturday and I'm loving it so far
V1R
Had my second lesson of the PPL on Saturday and I'm loving it so far
V1R
Joined: Dec 2000
Posts: 294
Likes: 0
From: London, UK
Whipping Boy's SATCO said:
That's a very good point.
The only times I can think of when it might not be better to keep the speed up are:
On the other hand, if you are IMC at the time (God forbid!) it may be better to keep the speed (ie energy) such that when you break cloud you can then trade speed for maintaining hgt.
The only times I can think of when it might not be better to keep the speed up are:
- when you're unsure whether you really will be breaking cloud before you hit something,
- if you're over water or inhospitable terrain and an extended glide could take you clear; or
- when there's an advantage to staying up as long as possible, eg if there's a chance of a restart given enough time.
Joined: Dec 1998
Posts: 4,282
Likes: 6
From: Escapee from Ultima Thule
CK, why not have a go at doing it each way? Try the zoom method, then try the S&L method. Do both ways while also trying to do your checks and look for a field.
I know which method I - and my students - find easier.
WRT to your comment about additional height & clearing obstacles etc, I think you've misunderstood something: using speed to maintain altitude until at Vg, or changing speed into height first then maintaining Vg is largely irrelevent to glide range. It's all about potential & kinetic energy. Zooming & diving changes one to the other. If anything, the additional 'g' required to initiate the climb has an adverse effect in terms of wasting some of that precious energy because it adds drag. Mind you, at the typical 'g' levels used to initiate the climb I think the difference is negligible, making the decision to zoom or not being based on practicality ie does it do anything for visibility?
I know which method I - and my students - find easier.
WRT to your comment about additional height & clearing obstacles etc, I think you've misunderstood something: using speed to maintain altitude until at Vg, or changing speed into height first then maintaining Vg is largely irrelevent to glide range. It's all about potential & kinetic energy. Zooming & diving changes one to the other. If anything, the additional 'g' required to initiate the climb has an adverse effect in terms of wasting some of that precious energy because it adds drag. Mind you, at the typical 'g' levels used to initiate the climb I think the difference is negligible, making the decision to zoom or not being based on practicality ie does it do anything for visibility?
Joined: Sep 2004
Posts: 43
Likes: 0
From: UK
I'm pretty sure I understand 
My point is that if you maintain height and let the speed bleed off, then unless you are heading in the right direction at the moment of failure and taking into account thinking time, then your effective range to the field to the side or behind you that you can land in is reduce by virtue of the fact that you have maintained your height and travelled futher away or maintained your distance.
My point is that if you maintain height and let the speed bleed off, then unless you are heading in the right direction at the moment of failure and taking into account thinking time, then your effective range to the field to the side or behind you that you can land in is reduce by virtue of the fact that you have maintained your height and travelled futher away or maintained your distance.
Joined: Aug 2003
Posts: 23
Likes: 0
From: UK
An intersting topic - I had a purely gliding background before taking up aviation as a career, so my personal preference is the pull up to wash off speed. In a glider I would use a 2-2.5G pullup and a 0G pushover, obviously that's a bit dramatic in a light a/c for passenger comfort and the maps etc bound to be strewn around the cockpit.
My reasoning is this - a light a/c drag curve is quite steep, that is to say that if you are not very very close to your best glide speed the aircraft will be performing poorly. For a normal single engine piston you will probably be a good 40-50kts over your best glide in the cruise which will absolubtly destroy your glide ratio.
The pullup method therefore gives the benefit of extra height and time over the straight and level method. Of course like many things in aviation this is just my preference and there is not a single correct and accepted method.
My reasoning is this - a light a/c drag curve is quite steep, that is to say that if you are not very very close to your best glide speed the aircraft will be performing poorly. For a normal single engine piston you will probably be a good 40-50kts over your best glide in the cruise which will absolubtly destroy your glide ratio.
The pullup method therefore gives the benefit of extra height and time over the straight and level method. Of course like many things in aviation this is just my preference and there is not a single correct and accepted method.
Jet Blast Rat
Joined: Jan 2001
Posts: 2,081
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From: Sarfend-on-Sea
The only time I have been taught to trade speed for height after engine failure is at low level. Then the speed needs to be back to glide as quickly as possible to stabilise the approach for judging landing position. However most civvies should not be flying at low level (stand fast commercial helicopter pilots on the wire inspection or police flights) unless forced down by weather, and if it really isn't your day and you lose the engine during a weather diversion then you shouldn't climb as you may enter cloud.
I would therefore agree with those here that staying approximately level until best-glide speed is reached is what I have been taught and told to teach.
I would therefore agree with those here that staying approximately level until best-glide speed is reached is what I have been taught and told to teach.
