Glide approaches as standard

[KCDW]

Dear all

There seems to be a minority view by respected aviators who believe that we should carry out glide approaches as standard procedure (take, for example, Jerry Eichenberger in "Your Pilot's License"). I know of another experienced instructor (specialising in vintage tailwheel planes) who swears by it

Their main rationale is that if you do get an engine failure, you will be used to the approach picture and handling characteristics of your aeroplane. There are also side benefits such as the better view.

What do people think?

Thanks

[High Wing Drifter]

I understand this used to be standard practice.

Downside is that you complicate matters on a regular basis which is bound to end in tears more often. Also the safety angle must be marginal as properly operated idling/low power engines are not likely to fail?

My view is pracitce glides regularly, but not every approach.

[ShyTorque]

Used to be standard practice on rotary engined aircraft as they had no throttle. The only engine control was the mag switch.

I believe glider pilots do it quite regularly; not too many go-arounds.

[High Wing Drifter]

I believe glider pilots do it quite regularly; not too many go-arounds.
Ah yes, but unlike me, a glider pilot probably has skill :\

[Genghis the Engineer]

Coming from a microlight flying background, it's my personal standard practice as well - I have to remind myself from time to time to practice powered!

The benefits (in my opinion) are much as KCDW suggests, the main disadvantage is that in a crowded circuit it can confuse somebody behind you if they weren't expecting such a steep approach.

G

[dublinpilot]

And speed brakes!

[FlyingForFun]

The disadvantage, to my mind, is that you have fewer options if you don't judge it quite right (e.g. if you didn't predict the sink on short final quite right).

If you get too high, you may have to side-slip or use an S-turn at low level, which isn't a problem, but it's much easier to just reduce the power a bit. If you get too low, you may have to add power, in which case it isn't a glide approach any more. Well worth doing from time to time, for practice, but not what I would consider a "normal" approach.

Does anyone have any statistics on how many "modern" piston engines suffer engine failure on the approach? I've never heard of it happening, and I'd guess that the statistics would be very very low. And in any case, most (but admitedly not all) approaches have some reasonable forced landing sites if the engine did quit.

FFF
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[DFC]

Does anyone have any statistics on how many "modern" piston engines suffer engine failure on the approach? I've never heard of it happening, and I'd guess that the statistics would be very very low. And in any case, most (but admitedly not all) approaches have some reasonable forced landing sites if the engine did quit

There are lots of reports relating to things like - added power but engine failed to respond - carb ice suspected etc.

Also if one is gliding to a landing on the runway one does not have to considder forced landing sites.

One reason why one could be minded to complete a glide powered approach is that Mr Cessna uses that form of approach and the landing figures are based on that i.e. Power Off, Max Flap and Max Braking.

Oh, and the most efficient way to operate a jet is to remain at optimal cruise level until one can close the throttles and never open them again until on the runway. ;)

Regards,

DFC

[S-Works]

Try it in a seneca........

[Rallye Driver]

But at least you crash the right way up!


Re: glide approaches. I fly regularly from three different fields. One is full ATC, so glide approaches aren't really an option unless the circuit is clear. The second is a busy training field, where the C152s often seem to fly QXC circuits, so again only really an option if Number 1 and it isn't busy. Number three has gliders (part of the years), jets and piston warbirds - so again the circuit can be interesting, but it's possible on a quiet day in the week.

I agree that glide approaches are incredibly useful practice. Having done a few recently, I realised how out of practice I was. As someone who has also had an engine failure and forced landing a few months ago, I know from experience how a little more height could have made all the difference.

So, I would say glide approaches where possible, and more PFLs is probably the best practice to prepare you for the worst. Engines do stop when you least expect it!

RD

[KCDW]

Thanks all so far. I'm beginning to get a picture.

Bose-x: Try it in a seneca........ Having not flown one, presumably the thing just falls out of the sky. In fact it makes me wonder about all the more powerful, heavier GA types which usually recommend a "trickle" of power just prior to landing. Surely we need that trickle of power to keep open the margin of safety for regular non-scary landings.

For the lighter GA types at "Radio" stations with an empty circuit. Then I guess the answer is "by all means".

[Classic]

It's an old fashioned idea which is pushed by the taildragger types mostly, and sometimes by people who can't fly the aircraft onto the ground.

Engine failure on short finals is generally down to icing, whch is more likely to occur with the throttle closed, and also power on the approach reduces the stall speed and helps tailplane authority.

Any approach is about energy management, and the easiest/best way to manage energy is with a throttle in your hand.

If you want to land in the right place, on speed, with the optimum rate of descent, use power on the approach. That's what it's there for.

[S-Works]

Its horses for courses I think. I fly a 152 and a Seneca for quite a few hours per month on each aircraft. I regularily practice glide approaches in the 152 but my normal landing is power to the ground.

The Seneca which has the flying characteristics of a brick would be unlikely to achieve a glide approach from 5000ft in the overhead! Its probably the reason for the second engine!!

Like all things flying, use the tool for the job and don't get tied up in dogma.

[Flyin'Dutch']

If you want to land in the right place, on speed, with the optimum rate of descent, use power on the approach. That's what it's there for.

So how will you manage that on a forced landing?

[S-Works]

Frank, See comment on horses for courses and give us less Dutch dogma!

:p

[Flyin'Dutch']

Steve,

No dogma. It may be useful to be able to plant the thing on the numbers when you have not engine to smooth things out.

Would you not agree?

[JonWhitehouse]

Went up on a check ride with an instructor in Wales who demonstrated the accuracy you can get from glide approaches. he cut the power late downwind, asked me to nominate one of the runway numbers, and without touching the throttle again, planted it directly on that number. I tried, but i think some more practice is needed on my part! I reckon practising any kind of emergency drill on a regular basis is essential, as it has already been said, things never scew up when its most convenient for you, so the whole boy scout thing is prudent i think.
JW

[bar shaker]

Every argument here for not doing glide approaches, is a perfect arguement for doing them.

The point about busy circuits is valid, but simply call "Short final for glide approach". It matters not if the field is ATC or A/G from a handheld.

As for some aircraft being unsuitable for glide approaches. This does not sit well with the fact that all aircraft are suitable for an engine failure.

[FREDAcheck]

Trouble is, everybody's right here. Yes, all aircraft are suitable for engine failure. And yes, some airfields are not suitable for glide approach, and you will not be thanked if you insist on doing them all the time.

Yes, engines fail, so good idea if your approach doesn't need one. And yes, engines are most likely to fail after running at idle, such as after a glide approach.

I compare the risk of an engine failure on a powered approach, with the risk that I might not make a perfect glide approach and need power at the end of it. No contest: the engine is probably more reliable than me, so I use power. Better pilots might decide otherwise. But I do practice glide approaches (and PFLs) regularly.

[bookworm]

A downside that no one has mentioned is the possibility that repeated glide approaches, particularly in the full-power-climb/very-short-cruise/glide, do more harm to the engine than progressive power reduction. It's likely to be more of a factor for larger engines.

Whether that effect is big enough to swing the balance towards preferring powered approaches is, like everything else in engine-management-technique, difficult to provide quantitative evidence for.

[Classic]

So how will you manage that on a forced landing?

Same argument can be applied to a flapless approach. How would you manage then?

Flying glide approaches is rather like coasting the last quarter mile in your car, it can be done but it's not condidered good technique and deprives you of one vital energy management device. I often see glide approaches flown by people who are not confident that they can coordinate the power/speed/RoD/drift all in the last few feet. So the easiest thing to do is to habitually get high, close the throttle and that's one less control input to worry about.... until they see the hedge at the end of the feild rapidly approaching.

I appreciate that there are a few old ac types where there is little alternative to the glide approach - these comments are directed at the vast majority of training/touring GA aircraft.

[bar shaker]

Classic, you are, of course, spot on. There really is no point doing glide approaches at all.

If the donkey ever dies, getting it all safely into that 400m field will be just like coasting a car the last 400m home.

[CKnopfell]

Nobody seems to have mentioned the noise aspect.

If I am coming into a noise sensitive airfied I will generally, traffice and ATC, permitting, remain high until I am on base or final and then glide in.

Far less likely to annoy the neighbours than extending full flap and powering your way over the hedgerows.

But, watch for carb icing and engine shock. My chariot is fuel injected so that is not a problem and on a cold day I will leave a trickle of power on to keep the engine warm.

[Classic]

Barshaker, did I say that there's no point in doing glide approaches? Of course they should be practised.

I may practise flapless approaches in case of flap/electrical failure, but it doesn't mean ALL my approaches have to be like that. ;)

My point is that if I'm examining someone and they always glide it in the last few hundred feet, I ask them to do a powered approach to the flare, and guess what, most can't achieve an accurate, on-speed touchdown in the right place. And that worries me!

[Pitts2112]

Have to disagree with many of the posts here. Almost every approach I do is a glide approach in both the Taylorcraft and Pitts. I can manage my energy quite well with elevator and use the power when I need to extend (misjudged the headwind, for instance, and current glide angle won't get me to the runway). I don't do it necessarily for the engine failure on approach reason, though that's part of it. I do it because I started out wanting to be able to glide accurately in case I had to put her down after an engine failure in the cruise. After that it just became habit. I don't see a reason to extend my approach with power - it just seems to be wasting time and fuel. But, unlike others here who say it shouldn't be common practice, I think each of us does what he thinks is best or enjoys most. I can put my airplane down on a dime in most conditions without power, which is a worst case scenario. Once I can do that, adding power just makes every scenario easier. That's a skill I want to have in the bag in case the old donk decides it's done before I'm done with it.

Pitts2112

[FlyingForFun]

DFC said, in response to my earlier post:Does anyone have any statistics on how many "modern" piston engines suffer engine failure on the approach? I've never heard of it happening, and I'd guess that the statistics would be very very low. And in any case, most (but admitedly not all) approaches have some reasonable forced landing sites if the engine did quit

There are lots of reports relating to things like - added power but engine failed to respond - carb ice suspected etcSorry, DFC, but that is not an engine failure on the approach. That's an engine failure on the go-around, and as Classic said, it is more likely with a glide approach, because of the increased chance of both carb icing and shock cooling.

I still maintain, after reading all the posts on this thread, that pracitcing glide approaches is important, and in some classic aircraft where visibility is very limited or the engine is particularly unreliable it may be useful to do a glide approach on most occassions, but in today's aircraft, including "spamcans", I do not consider a glide approach to be "normal".

The one thing which has become clear after reading the thread, though, is that this is yet another subject with two distinct camps, and that it is very difficult to persuade someone to change camp in either direction!

FFF
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[Son of the Bottle]

I think you're right FFF. Two very distinct camps. My own 2 cents worth is this: I like to practice glide approaches as often as I can. Apart from the safety aspects, it also helps to build confidence in the aeroplane and your own abilities.

However, I am also of the opinion that doing so is pretty hard on the engine. Just think: you go on a longish cross-country at 75/80% power for one or two hours, and then close the throttle fully as soon as you start your approach. I think that the resultant shock cooling shortens your TBO considerably.

However this is just my opinion - can anyone give us any relevant facts?

[Lowtimer]

No-one's suggesting maintaining max continuous power until you suddenly chop the power. That would be stupid, and completely unnecessary for practicing a glide approach. Even if you habitually cruise at such a high power setting, do you not start making progressive small power reductions as you near your destination to prevent shock-cooling as you descend and / or decelerate? If I'm intending a glide approach I will have already gently slowed to the appropriate speed and descended from cruise altitude. At that point I'm using something like 35% power, tops, whether I'm in a Cub, an Archer, or a Yak. I don't know anyone who makes a habit of driving round the circuit at max cruise or full power, whether they are planning a powered or a glide approach.

[justinmg]

I have recently been speeking to some owners of some very nice aircraft with temerature on all 6 cylinder heads etc. I am lead to believe, that the engine sustains much more abuse from shock cooling than most people realise. Progressive stepwise reductions in power and airspeed are much better.
Is a glide approach a different way of saying shock cooling, or is there more to it?

[ShyTorque]

Surely a glide approach from 800 ft at circuit power is not shock cooling.

Mind you, there are those flying relatively high performance aircraft at my local airfield who make a habit of rorting into the circuit at max chat and dump it on the ground asap. That probably IS shock cooling but who cares, when it's them paying for the overhaul on their own engine? :E

[Son of the Bottle]

Well, I don't really know, that's why I asked for more factual evidence from anyone who has it.

I accept that I gave an extreme example, but I would say that closing the throttle slightly from circuit power settings for a powered approach is kinder to the engine than throttling back completely.

[cubflyer]

Glide approaches are a good idea to be practised often and can of course be considered a "normal" approach, just as dragging it in under power can also be called a "normal" approach. Both are appropriate in different situations. Shock cooling is a problem, but as said, you should be gradually bringing the power back when approaching the field and thus the engine should be cooled from its cruise temperature by the time you pull the power off for a glide approach- or even before you start a powered approach.
Im very surprised at Classic's comments regarding people doing glide approaches because they cant do power on approaches. Ive never heard that one before, by heard and seen the opposite many times. You need to be much more precise to fly a glide approach and it improves your flying skills. Anyone can power on in and then cut the throttle over the runway and you see some pretty awful examples of this!
Someone said that the most efficient way of flying a jet is to stay as high as possible for as long as possible, then glide down to land without having to put power on. This may be true in theory, but even if ATC would allow you to do it, is never done. The reason being is that jet engines are slow to respond particularly from idle and you need to be able to add power quickly incase of a go around- or hit by a gust etc. Thus most airline procedures have you being up at 40% power or so by 1000ft on the approach at the latest.