Glide approaches as standard

[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 etc

Sorry, 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
-----------------

[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?

[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.