[Groundspeed]

Interesting, I was taught high key, low key when gliding but I'd not come across it in power flying. I was totaly unaware of the military usage, every day you learn a bit more.

[PaulSS]

All the posts that basically say, "well that's military speak and has no place at a civilian airfield" might well ask themselves why the military use the phrases. I can tell you that it takes a lot less time on the radio to say "high key" than "high, dead side, abeam the threshold" (or similar). Likewise "low key" is easier than "late downwind, high" (often with "glide approach" added). I don't use the military vernacular at civilian fields because I know it would cause confusion but I wish the standard phrases could be moved from the military part of CAP 314 to the rest of it.

For bug smashers and the like, high key is ideally around 2500' and low key 1100'. But that is the beauty of the system; if you're higher or lower you just elongate or cut short the next leg of the pattern and keep a constant aspect from low key. It works and it works well but I do admit that the phrases need better promulgation and standardising (in civilian books) before they are used at civilian airfields.

As a 'turning-into-an-old-fart' addendum, I seem to recall low key on the Harrier was 7000' (with high key around 12000'). It had the gliding qualities of a bunch of car keys AND you had to keep the engine windmilling sufficiently to provide hydraulic power for the steering; which meant maintaining 300kts. Of course, IF you did land you then had to stop and the average bicycle is equipped with better brakes than the Harrier, which meant that there was almost no airfield in the UK where you might actually be able to carry out a forced landing (maybe Boscombe Down). All of these numbers were crunched when they were mucking around in the early years at Edwards AFB and the whole of a desert available to land on. The Sea Harrier did not have this procedure included in the manual. Engine stops and you can't get it going; you're getting a Martin Baker tie

[Flyin'Dutch']

I've never encountered the use of H/L key in GA RT but know it well from my gliding experience.

Understanding the concept is useful and a goo tool in the (P)FL box it is too, dismissing what other say/do isn't particularly smart.

Can you ever know too much?

[flybymike]

If you are flying over high or undulating ground on the QNH and do not (and indeed cannot) know the ground elevation beneath you, then how can you know the high and low key altitudes?

[chevvron]

If you are flying over high or undulating ground on the QNH and do not (and indeed cannot) know the ground elevation beneath you, then how can you know the high and low key altitudes?

Glider pilots manage it when 'landing out'.

[kanga]

Key calls are made only in the vicinity of the landing aerodrome, I guess

[ChrisRowland]

If you are flying over high or undulating ground on the QNH and do not (and indeed cannot) know the ground elevation beneath you, then how can you know the high and low key altitudes?

Using a process known as judgement. You look at your landing area and judge your height and the angle you are above it.

Then fly a circuit round it, adjusting your distance to keep the angle above your landing area about the same as you will need for the approach. This gets you to finals at a position where you can make an approach using half to two thirds airbrake.

Two things:
You do NOT use your altimeter. They are very unreliable in gliders because the lack of vibration means that they can stick. And also you don't know the height of the terrain.
You plan your circuit relative to your landing area because that's the only thing that you can rely on having. You don't use secondary references because they won't be there.

If you don't have a landing area you have a problem, but it's not a circuit planning problem.

Gliders tend not to make radio calls in the circuit but where we do, such as at Aboyne, all we call is downwind. All we're saying is "coming ready or not". Going around is not usually an option. I don't recall anyone calling high/low key.

[flybymike]

Yes, I realise that ultimately planning the glide will be a matter of judgment “on the hoof.”

I’m really just remarking on all the academic discussions revolving around specific actual altitudes (or heights or whatever) at specific positions which will probably all turn out to be completely irrelevant in practice.

[Flyin'Dutch']

Yes, I realise that ultimately planning the glide will be a matter of judgment “on the hoof.”

I’m really just remarking on all the academic discussions revolving around specific actual altitudes (or heights or whatever) at specific positions which will probably all turn out to be completely irrelevant in practice.

When flying something with an engine you would fly a normal circuit of course, in a glider you would know how more or less your height from reading the map and reading your altimeter.

I don't concur with the previous poster about unreliable altimeters. They are calibrated to the same standard as the ones in your PA28. There can be some lag but a tap on the instrument panel sorts that out.

Beyond that is down to your ability to judge the picture and make it work by adjusting your circuit and using your flaps/airbrakes.

[MichaelP]

There are two methods of forced landing in the Canadian FTM.
One is the circuit, the other is High Key/Low Key.

The emergency procedure for the Malibu Jetprop recommends the High Key/Low Key method, and this worked very well when we did a practice forced landing into Phitsanulok... It needed careful EFL speak to get permission to do it...

Different for me, I have no turboprop experience, but not different because it's just an aeroplane in the glide.

Regardless of knowing altitude, and height above touchdown, this method works well.
I teach both methods, and I tend to like this High Key/Low Key more as I do it more often.