I was trained in the Air Force so I used the high key/low key/ base maneouvre.
The point of this manoeuvre is to get to know your own a/c performance: attain glide speed, loss of altitude per mile, etc… It gives you a framework as a pre-executed maneouvre to comply with the checkpoints during the glide. For example:
High key is 1500ft AGL above the threshold: If I’m lower than that, I’d cut the track looking for the low key checkpoint which is downwind abeam the threshold glide speed with gear down and locked and flaps full. If I get there with speed and altitude, it’s time to lower the gear and flaps. If I’m still below those reference numbers, I’d delay lowering the gear and cutting once again the base if it’s possible.
The overall maneouvre is to think as little as possible during emergency situations and to stick to you numbers thus making the inflight decissions much easy.
Peter wrote:
What would a corresponding diagram for a SE plane look like?
Similar, though obviously, the pane has a minimum speed much faster than the zero of the helicopter. But thinking about it, you could fly your plane power off at the stall speed, and with enough altitude, accelerate to a gliding speed suitable to flare and land. But, that would require altitude. If you were gliding faster that stall speed, though still not at “best glide speed” you would require less altitude to accelerate to flare and land. The closer to your “best glide speed”, the less altitude required to accelerate. If you were at top of flare at best glide speed, you could land safely.
So, one can see why climbing out at Vx, will get you over the trees, but has you at slower than Vy, which will probably be really close to best glide speed. Therefore, there will be a certain phase of a Vx climb, from which after a power failure, entering a glide to a successful landing would be difficult – you’re just not going fast enough.
A helicopter can store energy for a flare as both airspeed (which can be traded into rotor RPM), and as excess rotor RPM (usually to 100% of normal). Airplanes can only store energy for the flare as airspeed, so having a little extra in your back pocket for a forced approach may be reassuring.
speed wrote:
The overall maneouvre is to think as little as possible during emergency situations and to stick to you numbers thus making the inflight decissions much easy.
Yes, I agree high key/low key/base maneouvre is simple concept with two steps to 1/ know aircraft performance on the day and 2/ execute a circuit
Ideal that shape is better flown at “best glide” , but one can still fail 1/ & 2/ for load of reasons, so when you reach “final” you get the truth:
- If all looking good, well done !
- You are too high, then flying best glide or faster is no good when you want to land bellow (so fly slow)
- You are too low, then flying best glide or slower is no good when you want to land ahead (so fly fast)
Just pure common sense as per POH/AFM and withing wise instructors words “can’t stretch glide” and “can’t land pushing stick”
No need to understand drag curves, polars, energy, H-V…
Pilot_DAR wrote:
But, that would require altitude. If you were gliding faster that stall speed, though still not at “best glide speed” you would require less altitude to accelerate to flare and land. The closer to your “best glide speed”, the less altitude required to accelerate. If you were at top of flare at best glide speed, you could land safely.
So here you go one way to burn 300ft excess of height quickly: fly near stall then accelerate to best glide and flare 
Power off, nose down and and wings are level so not much to worry about apart from burning too much
Ibra wrote:
fly near stall then accelerate to best glide and flare
Power off, nose down and and wings are level so not much to worry about apart from burning too much
No for me – much too much to worry about! I have had friends die, and nearly so, trying this!
Can you show us anywhere in approved training material, or a flight manual, where this is a recommended procedure?
What you’re advocating is to deliberately descend more steeply than normal, at a slower than “best” gliding airspeed, build up the airspeed, and then pull to arrest the descent – correct? What if you misjudge? Remember the Hawker Hunter crash at Shoreham? That pilot was descending more steeply than normal, and failed to build up enough airspeed to enable a pull to arrest the rate of descent. I can think of dozens of crashes resulting from a pilot thinking that they could arrest the rate of descent at the bottom of a steep descent close to the ground. One of the most spectacular was the RAF Nimrod at the CNE Airshow. Both of those planes were being dived inside the undocumented H/V curve I have mentioned. They were too close to the ground to allow enough space to allow enough speed recovery to enable the build up of G required to arrest the rate of descent before they hit.
Why do pilots continue to blunder into thinking this is an acceptable idea? Lack of understanding of the implications of the H/V curve concept, I opine….
Have I missed “Sideslip” in skimming through the posts?
Maoraigh wrote:
Have I missed “Sideslip” in skimming through the posts?
I offered a while back:
If it had actually quit, and I was planning to squeeze it into a tiny spot, yes, I’d sideslip, and it would be more dramatic. But when I’m planning power off from downwind, I should not need to slip it to achieve the approach and touchdown I desire.
I quite like sideslips, as those who are familiar know, you can apply and recover near instantly, while otherwise maintaining good control, on speed.
Pilot_DAR wrote:
What you’re advocating is to deliberately descend more steeply than normal, at a slower than “best” gliding airspeed, build up the airspeed, and then pull to arrest the descent – correct? What if you misjudge?
Yes, agree there is a minimum height where you can’t do that safely but I am sure 300ft is enough
Height loss accelerating from VS0 to Vbg can’t be higher than the POH stall loss?
Do you have an H/V curve for a typical SEP?
Pilot_DAR wrote:
Remember the Hawker Hunter crash at Shoreham?
The last thing I have in mind in SEP engine-off bellow 500ft is doing loops/aerobatics (even turns bellow 500ft is big NO for me, so I only care about going forward/back on the stick while the wings are level)
I think this is the wrong example, the last thing he had in mind is “burning energy wing level” he was full power and G-locked AFAIK? not sure about how Hawker Hunter fly power-off but on T37 Tweet (similar under-power jet junk) if the 2 engines quit while doing 1200ft circuits you are guaranteed: 100% death if go for stick and 50% death if go for ejection seats…
Pilot_DAR wrote:
I quite like sideslips, as those who are familiar know, you can apply and recover near instantly, while otherwise maintaining good control, on speed.
I like that too but also dependent on type, on Piper Cubs with no flaps: sideslip it is the way to go, on long body Mooneys: maybe? but want to avoid venting fuel (well engine is off) and avoid stalling the tail (not my lucky day), POH/AFM manuals are clear on this
The power-off 180 precision landing is part of the FAA CPL checkride. The required performance is landing minus zero / plus 200ft from a pre-defined point on the runway. What worked best for me was to trim to Vbg and come in relatively high gradually adding flaps, sideslip and dissipate the (little) remaining energy in ground effect.
my 5 cents probably no one will agree with me but here it is
because I fly multiple different airplanes i use the same landing technique in all of them
unless there is traffic in the pattern (rarely at my airport or at many places that I fly) I ALWAYS use the high/low technique
that is every landing is in reality an overhead approach learned from the military and my 800 hrs on my SNJ-5
I can confirm that any airplane can be landed that way from the high high performance turbines to the little biplanes as a bucker to a common rV-8
approach requires to access the airport at 2500-3000 feet from wherever you are. If it is an emergency I hopefully will have extra altitude and that is high key, over the select field with at least some excess altitude, that means circling if needed over the airport to reach low key. Low key is ideally entered via an initial approach towards the field called initial, say you are landing on runway 18 so you enter at 2500 feet heading 180 degrees aligned with the runway, that is how I approach low key, which is a point mid centered on the runway at midfield. Then power off completely and from there full overhead approach meaning 30-40 degree bank to a landing over the numbers without touching the power setting, if needed I will feather the prop but I dont that in general (I will in an emergency to get get a better gliding distance)
what that does is force you to be high over the field so you won’t be pulling on the stick or yoke and you are forced to lower the nose. The risk on the high bank required for the overhead approach is to turn too late (I turn as soon as I see the threshold) then you will need to increase the angle of attack and I have seen a buddy get killed when on the break with a quarterly tailwind do the brake and stall the plane (he killed himself) . I can do that with my PT-6 engined evolution to the SNJ-5 to the rv-8. You can land on the numbers and with the overhead technique you have great visualization. At my local airport now we have an active tower and they know me, so all they ask is if I want to do a left or a right brake for the overhead. If you practice this on every landing you will never have a problem once you reach any airport . Use the high/low technique in every landing unless traffic forces you to extend downwind and drag the airplane for 2-3 miles on final and if you have an engine out you are out of luck.
It does take practice. I never pay much attention to speeds except to make sure that I am not exceeding the minimal gear down speed I use full flaps mostly. Again when you do it right you won’t need to touch the throttle at all and it remains on idle. If you have an engine failure you will be landing safely from there on.
