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The most reliable way to do a forced landing? High Key / Low Key

Ibra wrote:

Yes, agree there is a minimum height where you can’t do that safely but I am sure 300ft is enough

I am not sure, and the value you state does not allow for error or variability. .

Ibra wrote:

Height loss accelerating from VS0 to Vbg can’t be higher than the POH stall loss?

We’ve been discussing forced approaches. Does the POH altitude loss value consider adding power during the recovery? The design requirement to which the altitude loss value is demonstrated states “level flight”, which can be presumed to include power for level flight. I expect that a stall recovery to level flight may take more than the POH stated altitude, it is flown entirely power off.

Ibra wrote:

The last thing I have in mind in SEP engine-off bellow 500ft is doing loops/aerobatics

“Power off, nose down and and wings are level so not much to worry about apart from burning too much” from 300 feet is what you proposed. In Canada, power off, and nose far enough down to accelerate would be considered an entry to an aerobatic maneuver (pitch attitude not incidental to normal flying). A loop recovery from 45 degrees nose down really might not be that different, other than you already have some speed built up.

Ibra wrote:

POH/AFM manuals are clear on this

Every SEP POH I have read allows for sideslips, though a few contain cautions about that maneuver – but not prohibited. Compliance with FAR 23.177 (3) is required (slipping). No POH I have read specifies an approach to stall and recovery entered at 300 feet under any circumstances.

Why abide by the terms of a POH for sideslips, which are approved, yet seem to disregard it and advocate a home made maneuver for low altitude approach to stall to attempt to correct a botched forced approach?

Ibra wrote:

Do you have an H/V curve for a typical SEP?

No. I’ve done enough formal flight testing, up to and including a Cessna Grand Caravan to understand that adherence to the POH procedures will keep you out of the danger zone. The concept is wise to understand, to prevent carelessly blundering into this unsafe area of non performance. The actual values of non performance do not help make it any less dangerous.

172driver wrote:

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.

Exactly. And Vbg + a bit won’t ruin the approach, if managed well on short final.

Home runway, in central Ontario, Canada

I visualised your procedure, magyarflyer, and I reckon it would work in the TB20 also. From 2500ft to do a 360 degree idle-power turn is probably fine, and you adjust the radius to suit.

I find that from late downwind, at 1000ft AAL, I lose the required 1000ft more or less exactly, with full flap and gear down. But that’s quite a tight circuit.

Doing this stuff with a working engine, thermal management comes into it. One needs to fly at low power for a bit to get the CHTs down, before going to idle.

Shoreham EGKA, United Kingdom

Surely the initial discussion from Peter is not about how to make 6000ft tarmac runway from overhead at 2500ft?

I am talking about short-field power-off landing in a 1000ft patch in middle of trees from 1500ft (or any height for that matter), all I am saying is that does not fit well with 90kts and 1.5T aircraft, whatever you do with the stick it will be crash or stall not a text book fully held off landing? above 600ft I can do whatever I wish at 90kts speeds and 45deg bank angle but bellow 600ft it will be done wing level at 65kts-120kts, with just enough extra energy to flare on the right spot

Vbg+ is not always good when you overshoot as some would think, you don’t land in 1000ft runwsy by pushing the stick ?

Last Edited by Ibra at 15 Feb 08:30
ESSEX, United Kingdom

My vote is for the constant aspect technique, with regular practice. If the circuit is not busy why not request a PFL?

One of the main threats is an undershoot – you are in effect crashing at a higher speed. Hence using the middle of the selected forced landing site as the aiming point. Once your landing is assured the aiming point can be moved towards you with flaps, or side slip if the aircraft is no flaps.

The other threat is fire, so secure the engine and get emergency services on their way.

Being on PFL glide speed, typically 70-75 KIAS on your 4 place SEP, plus 5 KIAS if there is a strong headwind – is a key control performance. If you are at 100 KIAS (ie plus 20-30 KIAS target) unfortunately you are likely to run off the end of your selected site at around 70 KIAS so in effect you have replicated the threat of an undershoot but on the overshoot.

If you are slow you risk both undershoot and loss of control.

The aim is to manage a worst case overshoot at relatively safe speed, of below 30 KIAS, hence not looking for a perfect field but one that you can reach safely on profile. Your insurance company owns the hull at this point, and want to minimise damage claims – allow Mr Cessna or Mr Piper to absorb the kinetic energy rather than try and stretch the glide to ‘save’ the hull.

The FAA has a good practical standard of touching down on correct speed within 200 feet of the aiming point.

Enstone (EGTN), Oxford (EGTK)

Can I remind thse more “experienced” on here of 2 things. Firstly there are a number of student PPL’s and secondly as this a successful international forum there will be a number of pilots who are by now totally confused about whether the discussion is about an emergency landing without power, a forced landing with power or a precautionary landing.
I am going to assume we are discussing training for or carrying out a power off landing ie an emergency landing.
Peter originally brought up high key/ low key which IMO is just certain military groups having to find a name for a simple training manoeuvre, which @ Vic perfectly described as the part of the PPL training set out in Pooleys.
In France it has a different name and as @Capitaine described it is a manouver which has developed here, from the square/rectangle into a 30 degree towards runway heading at the end of the downwind leg or cutting the corner by 45 degrees.
@Pilot-Dar is essentially saying the same thing but wisely advising us to practice it regularly.
@Ibra has chosen a different route if I understand him correctly,if he finds himself very high above the threshold he will pull the stick back to slow the aircraft until it is nearly stalling and then push the stick forward to pick up speed dive at the threshold and then flare. I have doubts about whether that would work as one runs the risk of not having enough runway available to stop or the risk of going nose first into the ground, but if it works for Ibra then okay, but I certainly wouldn’t teach that method.
The same goes for the 30 to 40 degree turn onto the threshold although I did see this work once. Here at LFFK once or twice a year pilots from all over Europe bring their Extras to take part in aerobatic workshops from current and past world champions in the discipline. One day I watched in horror as a Swiss pilot in his Extra made a tight turn onto the threshold, so tight that his wings were vertical with the outer edge of the left wing being no more than 20ft above the threshold.He landed the aircraft perfectly within 300 metres and taxied in. As he got out of the plane he smiled as if it was the most normal thing in the world. That might be but it is not something I will be trying anytime soon.
BTW I am old enough to remember instructors telling me that the only reason we talk about stall speed is that most GA aircraft don’t carry angle of attack indicators so the ASI is the best guide we have but not totally to be relied on.


Ibra wrote:

Vbg+ is not always good when you overshoot as some would think

Overshoot bad, undershoot likely much worse:

RobertL18C wrote:

One of the main threats is an undershoot – you are in effect crashing at a higher speed.

When yo selected your landing site, you defined the beginning as the last thing in your path which you really don’t want to hit, so be very sure you make it over. You can sideslip right to the point of touchdown if you need to dump the excess speed – at least you had it to dump!

Ibra wrote:

you don’t land in 1000ft runwsy by pushing the stick ?

I don’t land on any runway by pushing the stick!

RobertL18C wrote:

regular practice. If the circuit is not busy why not request a PFL?


Home runway, in central Ontario, Canada

Just my two cents on the “just above stall speed” idea:

If you are high on the last, fairly straight, part of an engine-off landing:

Flying down just above stall: your controls are mushy, you are not speed-stable, and your view of the target is much worse than usual.

If you slip it down: you have good control, your are speed-stable, and your view of the target is probably better than usual.

IMHO the ability to see where you are going, and the ability to change it, should not be under-estimated :-)

Booker EGTB, White Waltham EGLM

The risk is the same as doing short field landing or takeoff, both are flown slowly while scrifying visibility? are they sensible choices all times I have no idea but my options are:

I would fly slow toward VS0+5kts (or 10kts) wing level when high on landing rather than going fast on high speed sideslip landing (or trying something fancy) with a wall ahead in many fast aircraft types

I would fly fast at Vy+ on short field takeoff (or not do it), I simply don’t fly at Vx on low takeoff with a wall ahead

Everybody is well knowledgeable to make his own GO/NOGO choices on these but on forced landing you simply don’t and I think high speed side slips (or last minute turns) are not good choice in calm winds with trees ahead, remember G force is speed*speed/stop distance…

Also, when doing PFLs pick a 1000ft field in a touring 150kts machine for practice, it makes a bit of personal challenge but you may end up thinking about parachutes

I teach PFLs and field selection/landing on standard POH technique, it is far easier than in C172 at 70kts or Gliders at 55kts, and my teaching stops with truth at 600ft, but doing it at Vbg=90kts on Bonanza/Mooney outcomes seems bit debatable with 1000ft runway, so I have few ideas for my own comsumption…

Last Edited by Ibra at 16 Feb 12:18
ESSEX, United Kingdom

going fast on high speed sideslip

Common mis-conception-a forward slip should not increase speed. In fact arguably can be close to 1.1x Vs as any incipient departure is away from the lower wing towards the rudder, so easy to restore by forward movement of control column and neutralising rudder. Unlike a skidding turn incipient departure, there would be minimal height loss.

A true barnstormer of course would use the falling leaf technique in a PFL :)

Enstone (EGTN), Oxford (EGTK)

Looked at this picture in a previous post here, and it kept me wondering. While this may (or may not) work when you have a perfectly visible airfield in well known terrain, I would say out in the unknown (to you) countryside, this is a recipe for disaster. I have been doing a fair amount of instructing now, and power off emergency landings are trained often (until the student manage to enter a chosen field in a survivable fashion, or what looks like to me to be survivable).

A field has to be chosen, if it isn’t already. Then, never let it out of your visible field of view. If you do, more often than not, you will not find it again, or use valuable time trying to find it. If you are high, it’s better to do wide circles around it, planning to get at 1000 feet AGL at desired key point. This gives you lots of time also, maybe there are better fields etc. Then do a “normal” base and final. If you are lower, make s-turns or whatever until you get at desired key point at 1000 feet AGL. Only keep that field within view. There is only one thing to master; get to that key point at 1000 ft AGL.

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