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

“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”

Good for spotting that, many paradox happens when aircraft flies between 1
1×Vs and 1.3×Vs as all surface/power controls are reversed and do opposite job when moved to correct for tight mis-judgement of the ground, keeping ball/ailerons centred and fly vertical path on reverse stick with no power is a safe bet IMO the risk is a wing level symmetric stall along the runway

At 1.4×Vs all controls work as expected, especially ailerons with less than 45deg bank, but the risk of overshooting the runway on high energy impact or accelerated/assymetric stall trying to use ailerons for S-turns/Sideslip

I agree with Pilot_DAR that one should not be in any tricky situations to try fancy options (or pick a route along 3000ft runways) but one has to pick a flavour on these that suits him & his aircraft

On constant aspect ratio (my preferred technique), making 1000ft runway from anywhere in a 1000ft height circuit, has 1:1:3 aspect ratio while we have 1:9 glide ratio, so should be easy power-off? if aircraft can’t show 1:1 glide it will be tight but all I only need 500ft to walk away alive from 60kts wing level touchdown, speed is my friend to manoeuvre but there is a lot of energy to burn…

Obviously, making 3000ft runway from anywhere in 1000ft circuits has 1:1:9 aspect ratio is about best glide L/D, no one should fail at this

ESSEX, United Kingdom

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 aheadQuote

Yes, Cessna says in the POH for the 172S:

" On a short field, 10 wing flaps and an obstacle clearance speed of 56 KIAS should be used", where Vy for the 172S is 74 KIAS.

So, I notice, again, a poster expresses a deliberate intent to do the opposite to the POH specified technique!

Ibra wrote:

1×Vs and 1.3×Vs as all surface/power controls are reversed and do opposite job when moved to correct for tight mis-judgement of the ground,

Not on certified airplanes!

Sec. 23.173

Static longitudinal stability.

Under the conditions specified in Sec. 23.175 and with the airplane trimmed as indicated, the characteristics of the elevator control forces and the friction within the control system must be as follows:
(a) A pull must be required to obtain and maintain speeds below the specified trim speed and a push required to obtain and maintain speeds above the specified trim speed. This must be shown at any speed that can be obtained without excessive control force, except speeds more than the appropriate maximum allowable speed or less than the minimum speed for steady unstalled flight.
(b) The airspeed must return to within plus or minus 10 percent of the original trim speed when the control force is slowly released at any speed within the speed range specified in paragraph (a) of this section.
(c) The stick force must vary with speed so that any substantial speed change results in a stick force clearly perceptible to the pilot.Quote

Ibra wrote:

but the risk of overshooting the runway on high energy impact

Ahhh… I don’t think you can overshoot, if you’ve impacted, though I guess, you could bounce or slide – but then, you landed/crashed, not overshot…

Ibra wrote:

or accelerated/assymetric stall trying to use ailerons for S-turns/Sideslip

So just keep the speed up! If you’ve chosen to S turn, the turns should be coordinated, and thus no risk assymetric stall, If you’ve chosen to sideslip, don’t stall, and there’ll be no risk of assymetric stall.

I am genuinely worried at the prospect that a few pilots may be so eager to disavow established training techniques, and POH procedures. I cannot understand the need to speculate/opine/invent “new” things to do in our very well tested and proven fleet of GA SEP airplanes. Using the 172 as an example, it is an amply capable airplane, with a very good margin of safety to the POH. I know this, because it is part of my job to follow an approved flight test plan to test an airplane a specified percentage beyond it’s approved limits (for which I obtain a test flight permit), so that the required margins are proven to be there for everyday flying. But what I never do is to entirely ignore the procedures in the POH, and do the opposite!

If another pilot chooses to ignore the POH procedures, and well established training guidance, and go off an experiment, I suppose that’s none of my business, it’s between the pilot and the plane. But writing about it on an open pilot forum presents an enticement for other pilots to experiment, and cause unknown risk to themselves.

Those of us who can fly are so incredibly lucky to have the freedom and resource to do so. We must fly responsibly, for the sake of our passenger’s and our own safety, and the promotion of a safe pastime in the public’s eyes. We have a further responsibility to behave appropriately in the presence of our peers. That is not presenting, as apparently authoritative, speculative procedures, which are largely in conflict with the approved and established techniques.

Perhaps more than four decades of my being a pilot, lifting a couple of my dead pilot friends out of their wrecks, and nearly being killed by my student, while he was following a procedure properly, have made me jaded, and I no longer fit into the new group of adventure pilots, who would like to change everything. Perhaps I am needlessly cautious, and just want to fly safely, and practice my skills the way my training, and the POH procedures state. maybe I’m just reading posts in the wrong group of pilots…..

Home runway, in central Ontario, Canada

So you think flying a C172 at 56kts nose 12deg up high power when low at 50ft is a great idea (what if the engine quits?) while flying at 60kts nose down power off when you are at 300ft is dangerous, I really fail to see the logic ?

Vx depends on altitude and make zero buffer to gusts from winds curling over the wall you are trying to overclimb, you can’t just blindly rely on POH number for these things, besides the difference is 12% vs 15% gradients?

But it will be good to agree what is an H-V diagram for a SEP, I am sure high & slow and low & fast are inside, not a test pilot just common sense To

Last Edited by Ibra at 16 Feb 20:42
ESSEX, United Kingdom

to Peter regarding reciprocating engine cooling down
except for the warbird landing technique (we recovered close to 200 T-6 SNJ-5’s at Oshkosh for the 50 anniversary of this tranining plane and we did in about 30 minutes for the entire flight) where we are using 2000 RPM to make a lot of noise, and then cut the power, the general aviation airplanes benefit from having the airplane in landing configuration that is slow enough to come and land. On the brake I lower the gear first and second the flaps but my then the engine has been at landing power which already is cooling down the engines, in the rv-8 you have to slow down to 80 Its, in the Evo 110 but the turbines are not affected by shock cooling. But the point is that you have to slow down to be able to put it in the numbers, othwerwise you find overshooting the point of touch down which should be the numbers on the airport giving you plenty of time to round out for the landing. I always end up modifying the turn based on winds. Another benefit is that you get great visualization of the traffic since you are doing an 180 degre turn to see all traffic around you.

KHQZ, United States

/#100 The 360 Degree Overhead Approach – TailWheelersJournal.com.html

a visual description of the above

KHQZ, United States

Minimum sink is very close to Vs and in modest turbulence you will be exploring the stall regime. Minimum sink and 60 degree bank as described in the article is a contradiction in terms, at least in our current understanding of aerodynamics:)

Enstone (EGTN), Oxford (EGTK)

So I am flying along in a DA40 at 3000 ft and suddenly the engine goes pop, bang, nothing. I immediately trim for Vbg around 70knts. According to the POH my glide ratio is approx 10 to 1 therefore I can glide at Vbg for around 5nm. But I strike lucky and there is a field immediately ahead into wind of around 10knts. I am over the beginning of the field and start my stopwatch, 30 seconds later I reach the end of the field, I now know that this field is approx 1000metres long, I am now still above 2500 ft at Vbg, I turn crosswind then onto downwind I am now at 2000 ft. As the aircraft is trimmed I have the brain space to take a good look at the field surface and check for obstacles. I choose an aiming point some 100 metres into the field, to make allowance for the wind. At halfway along the downwind my brain starts questioning whether or not I can make it although I am still at around 1500ft. But despite or because of having trained at an airfield where I have started and engine off at 1500 to 2000 ft vertical the midway point, instead of continuing the downwind on the reciprocal of the QFU, I turn 30 degrees towards the runway/field.Are there any power lines, telephone lines trees to hamper my approach. If so I can adapt my aiming point . As my aiming point appears at the trailing edge of the wing I turn base I am at around 1000ft, if I am higher I will do a proper base leg, if lower I will continue the turn onto final. First stage flap might help here. My normal approach speed with full flaps is 70knt, but I will delay adding full flaps until the earliest short final as on the Da40 full flaps is like hard braking. If full flaps are not enough to lose enough height to land at my aiming point, I will S or sideslip. Which depends on how I see the situation on the day, I’m not sure myself why I choose one over the other on the day.
Basically this was the way I was trained, in both SEP taildraggers and tricycle gear. And also precautionary landings MEP, although in this case it is not power off and choose normal approach speeds.
I don’t see anything wrong with it, its the same as Pooleys and the description by Capitaine and has served me well on the 2 occasions when it was needed.
Some of the figures above may not be totally accurate they are off the top of my head I have not consulted the POH before writing.

France

Ibra wrote:

So you think flying a C172 at 56kts nose 12deg up high power when low at 50ft is a great idea (what if the engine quits?) while flying at 60kts nose down power off when you are at 300ft is dangerous, I really fail to see the logic ?

If you are taking off in a SEP towards a wall — as you put it — and the engine quits it doesn’t really matter if you’re flying at Vx or Vy. It’s going to end badly either way.

But if you’re making a deadstick landing your expectation is to do a normal touchdown. In that situation you need enough energy to flare and with 60 kt nose down at 300 ft you may not have that.

ESKC (Uppsala/Sundbro), Sweden

Airborne_Again wrote:

If you are taking off in a SEP towards a wall — as you put it — and the engine quits it doesn’t really matter if you’re flying at Vx or Vy. It’s going to end badly either way.

In engine failure scenario, yes it does not matter which one you fly but I think I am better staying in between, the initial point was on excess of speed to flare or recover from a stall, I really don’t think Vx = 56kts on a C172 does give any of that

Airborne_Again wrote:

But if you’re making a deadstick landing your expectation is to do a normal touchdown. In that situation you need enough energy to flare and with 60 kt nose down at 300 ft you may not have that.

Yes maybe 300ft is not enough to break 1200fpm rate of decent at 60kts power-off but then I was not that high enough to slow down that much?
Short field approach speed for 40deg flaps on a C172 is done at 60kts but obviously breaking the rate of decent with the power not extra height or flaring

magyarflyer wrote:

On the brake I lower the gear first and second the flaps but my then the engine has been at landing power which already is cooling down the engines, in the rv-8 you have to slow down to 80 Its, in the Evo 110 but the turbines are not affected by shock cooling

(Joke) I was told to warm up engine in PFLs anytime there are serious doubts we are not making the selected field, it helps keeping engine temps and pilot moral up

On PFL techniques, my guess all of them should reasonably work when you have sufficient height/runway, say 3000ft agl/3000ft runway in hands of an average pilot, but all of them will miserably fail with no exception when you don’t have that even in experts hands, I would be impressed if someone can show consistency for 500ft agl/500ft runway even in STOL Super Cubs (anything bellow 500ft is dead ahead for me with same chances as CAPS), any pilot should just find his technique limits on his aircraft, I am personally not happy about less than 1500ft agl/1500ft runway on touring machines on any “prescribed technique”, engine failure 500ft-1500ft with 1500ft length patch does keep me awake during the night, mostly excess of energy when high on final and stall under tight maneuvering to get there, but it still not worth buying CAPS for me

I found it difficult to make 2500ft HK from a downwind engine failure at 1000ft

Last Edited by Ibra at 17 Feb 13:23
ESSEX, United Kingdom

Some aircraft Vx is such a steep climb attitude that recovery from an EFATO is unlikely. At best you might push the nose over bringing the stall speed to below Vs due to approaching zero G, only to stall/lose control as gravity re establishes itself.

The Super Cub Vx is 45 mph IAS, 5 mph above Vs on a nice day.

Enstone (EGTN), Oxford (EGTK)
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