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Possible turn


Stephen

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On 10/30/2020 at 7:15 AM, Bob - S50 said:

Another consideration, and I cannot take credit for this, I've just read it somewhere.  If you are really worried about the engine quitting on every flight, AND you are flying out of an uncontrolled airport, THEN you might consider making a 45 degree turn once safely airborne.  That way, when the engine actually does quit you won't need a 260/80 turn to get back to the airport.  You might need as little as a single 135 225 degree turn.  Plus, by turning 45 degrees to create turning room you will also reduce your distance along the extended centerline by about 30%.

That was in a recent AOPA Pilot article (or was it their Flight Training magazine)?  I was thinking about that just now, too.  IIRC, they also suggested making the turn in the downwind direction, so that you need less turning space to get back on the runway centerline.  Obviously, that would heavily depend on any other traffic in the area and other safety considerations.  I was thinking, though, that if you could make a 45 degree turn safely, why not make a 60 or 90 degree turn anyways?  Then you'd have a more realistic option of turning back to the normal runway direction anyway.

Another point worth considering is that in the normal VFR pattern, the AIM suggests the crosswind turn should be no earlier than within 300' of pattern altitude, or typically 700' AGL.  Since that seems to be the absolute minimum to make the attempt, it suggests if your engine fails on the departure leg, you're still going to be landing straight ahead.

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2 hours ago, Stephen said:

Thanks guys, great discussion. I've thought about the offset Bob suggested after takeoff. The offset, presumably should be downwind so you can turn up-wind in the event of a failure. That said, if the offset turn is downwind, it will carry you away from the runway more quickly and you will be fighting the wind (albeit holding airspeed) to get back. Interesting thought though. If during a crosswind takeoff, if you crab a bit into the wind you are also already pre-oriented in the upwind direction and have some varying degree of turn angle reduction in the event of a turn-back. I was looking at a youtube video and he indicated that his experimentation seems to indicate that the 60 deg vs 45 degree actually results in less altitude loss. Obviously with 60 or more degrees it becomes increasingly *essential to push to maintain airspeed* and avoid loading up the airplane with excess AoA. At 5:16 in the video it gives a pretty good sense of the windshield full of terra firma effect:

The direction of turn would be wind dependent.  If there is no crosswind then either direction would work equally well, however, most of us would prefer to make the turn back in a left turn because we can see better.  That would require an offset to the right after takeoff.  If there is a significant crosswind, I would probably turn downwind.  If the engine quits at low altitude the extra offset will give me more turning room.  If I'm climbing at 100 knot ground speed, that's about 170'/sec.  At a 45 degree angle, that's building an offset at a rate of about 120'/sec.  If I'm climbing at 1000'/min, I'll reach 600' in 36 seconds and will have about 4300' of offset, or about 2/3 of a nautical mile which would be a fairly tight downwind.  Even a 20 knot crosswind will only make about a 1200' difference, so I can either be offset by 5500' or 3100'.  Call it one mile or 1/2 mile.  You choice.

As for the bank angle, here is a link to an article about the impossible turn from an analytical perspective. Impossible Turn

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1 hour ago, jaylw314 said:

That was in a recent AOPA Pilot article (or was it their Flight Training magazine)?  I was thinking about that just now, too.  IIRC, they also suggested making the turn in the downwind direction, so that you need less turning space to get back on the runway centerline.  Obviously, that would heavily depend on any other traffic in the area and other safety considerations.  I was thinking, though, that if you could make a 45 degree turn safely, why not make a 60 or 90 degree turn anyways?  Then you'd have a more realistic option of turning back to the normal runway direction anyway.

Another point worth considering is that in the normal VFR pattern, the AIM suggests the crosswind turn should be no earlier than within 300' of pattern altitude, or typically 700' AGL.  Since that seems to be the absolute minimum to make the attempt, it suggests if your engine fails on the departure leg, you're still going to be landing straight ahead.

I'm thinking 60 or 90 degrees would built too much offset by the time you get to a safe altitude.  Plus, a 45 degree offset will require a 225 degree turn back, a 60 degree offset will require 240 degrees of turn, and 90 degrees will require 270 degrees of turn.

As for when to start the offset, if I'm staying in the pattern, which I rarely do, then just fly the normal pattern.  The AIM is not regulatory, just best practice.  I would only consider the 45 degree offset if I'm at an uncontrolled field, departing the pattern, and paranoid about losing an engine at low altitude.

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2 hours ago, Bob - S50 said:

I'm thinking 60 or 90 degrees would built too much offset by the time you get to a safe altitude.  Plus, a 45 degree offset will require a 225 degree turn back, a 60 degree offset will require 240 degrees of turn, and 90 degrees will require 270 degrees of turn.

As for when to start the offset, if I'm staying in the pattern, which I rarely do, then just fly the normal pattern.  The AIM is not regulatory, just best practice.  I would only consider the 45 degree offset if I'm at an uncontrolled field, departing the pattern, and paranoid about losing an engine at low altitude.

Ah, I see what you're saying, no I meant if you depart on Runway 09, just turn 90 degrees to the left as soon as you think it's safe.  Then if the engine quits, you turn left again and land back on Runway 09 (instead of 27), with the advantage of landing upwind instead of landing downwind after the impossible turn.

Heck, now that I say that, if you're going to make an early turn and aren't worried about pattern traffic, just keep the turn coming and make another left turn onto the left downwind leg of the pattern.   From there, if the engine quits, it's a normal approach to 09

Obviously, if you are worried enough about something to not make an early turn, this whole discussion is moot anyway.

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This is what happens when you come up short.

This happened at KCHD on Friday. The pilot had an engine failure after takeoff. He tried to return to the airport. He came up a little short. 22R has about an 8 inch edge at the end of the runway. It took off his nose gear and flipped the plane. I believe everybody is OK.

73CF38D1-4276-45D6-A836-17FF86FF8AA6.jpeg

https://www.azfamily.com/news/two-people-ok-after-plane-crash-at-chandler-municipal-airport/article_7654ffea-2047-11eb-a669-aff97878644b.html

 

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29 minutes ago, N201MKTurbo said:

This is what happens when you come up short.

This happened at KCHD on Friday. The pilot had an engine failure after takeoff. He tried to return to the airport. He came up a little short. 22R has about an 8 inch edge at the end of the runway. It took off his nose gear and flipped the plane. I believe everybody is OK.

73CF38D1-4276-45D6-A836-17FF86FF8AA6.jpeg

Well if they’re ok, success?  Depends on what was straight in front of them when it failed... wheat field?  Maybe I’d rather have continued.  My home airport has a train yard (bridges, power lines, and towers) and industrial buildings.  I think I’d take upside down but alive.

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3 hours ago, Ragsf15e said:

Well if they’re ok, success?  Depends on what was straight in front of them when it failed... wheat field?  Maybe I’d rather have continued.  My home airport has a train yard (bridges, power lines, and towers) and industrial buildings.  I think I’d take upside down but alive.

Oh, there are a lot of choices. If they would have aimed for the dirt between the runways, or the ramp, or the taxiway, they wouldn’t have flipped. Hindsight is a wonderful thing. I just knock on wood and I’m glad it wasn’t me. All we can do is learn from others and hopefully end up better ourselves if we have to deal with it.
 

I think they did just fine.

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Around DVT the choices can be very limited depending on the way you happen to be pointing.   I've reasoned that the airport is big enough that even if I can make it 90-degrees to the runways it may be the best choice, depending, but it's certainly an option when the others are worse.

 

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On 10/29/2020 at 5:58 PM, Ragsf15e said:

Definitely.  It depends.  Each airport/runway has its own best option/altitude.  

This is the more relevant thing to practice.  The decision of what you will do in an emergency is more important then how well you preform the maneuver.  
 

Far too much time in aviation is spent on practicing a maneuver and not on practicing what maneuver you should use and when you should use it. 

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My e model used up almost 600 feet. T/o  flaps in the turn. Just stand it up one the wing and pull her around. Had to do it in anger below 500 ft taking off out of west palm in a 152 last year. Worked out well. Scared the shit out of the student:) Not sure its for everyone. Takes a very aggressive mindset. I'm a full time cfi, fly 5 hours a day, 7 days a week. Not sure how comfortable most pilots would be doing it. I always know what field Im going into before take off. 

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Pete,

Can you estimate the bank angle and degrees of attitude you used with the C152 during the turn...

I have an aggressive mindset... it’s the right vs. wrong I want to learn more about... :)

I think the scary part of the engine out... is the silence... that’s scary enough...

Steep bank while pointing at the ground is icing on the cake...

Best regards,

-a-

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I think I've just rethought this with me, and I'd try and make the turn pretty darned low, unless I saw something really benign right in from of me.  My thinking is I should be able to keep the aircraft reasonably coordinated and flying.  Thinking about my home airport, wherever I wind up in the turn isn't going to be any worse than what I"m going to land in if I go straight ahead, and there's the possibility of making it to the airport or the airport environment.  Key to all this is to keep the speed up and keep the airplane flying straight.  So longs I level off before I hit terra firma this should be a sound strategy.  

Kinda reminds me of the Woody Hayes saying about passing the football.  There are only three possible outcomes, and two of them are bad.

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Climb gradient and runway length are key here. If my engine fails at 500' departing LAX, I'll land on the remaining runway ahead (joke).
For fun, I computed the minimum turn-back altitude for several combinations of runway length and headwind components (negative = tailwind). Rounded up to nearest 100', and a minimum of 500' enforced to mitigate 0 lateral movement assumption. Approximate parameters were used, here (don't use these results), but I intend to complete this table for several takeoff altitudes and make it part of my pre-flight. If you are curious about how I got these numbers and the assumptions made, I uploaded a file called ImpossibleTurn2DComputation to Safety & Techniques that outlines the theory. Please forgive the table formatting, web excel has limited functionality.
Sensitivity analysis is interesting. I found that, perhaps not too surprisingly, the results are very sensitive to the rate of climb, beyond headwind and runway length whose effects are obvious in the table below.
image.thumb.png.794abc8995ec1b7ad496e9848741ac48.png

Edited by VinceCB
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When runway is short climb/glide gradient is really important for the types, in my airfield which is 2000ft runway I only saw PC12 or PA18 practice it, the former they do that to show to regulators they can always make runways back for some special single engine operations and a powerful PA18 could make it work like in many YT videos, as you do +15% to +25% climb gradients on full power and -10% glide gradients on zero power, good luck with a heavy school trainers doing +500fpm at 70kts climb and -800fpm at 70kts glide, it will not got back to whatever it come from to whatever left from that 2000ft runway even if you are lucky with 0ft height loss in the impossible 270deg turn and without counting xwind drift :lol:

If the runway is long 10000ft yes that is when absolute height is the sole driver but as much as landing ahead on whatever remain of the runway ;)

in gliders, I was taught if you have to turn back then turn initially left or right with the wind as the goal was to make the turn quickly into wind and well positioned as you drift rather than ending in awkward position, also the idea is simple if you land into 20kts headwind it does not matter what you land on, you will always walk away, if you land with 20kts tailwind it does not matter what you land on, you will surely die ! 

I am a fan of landing into wind wing level at stall speed, that is what matters in my opinion, you only need some 60ft stopping distance? the rest of accessories (runway/off-field, houses, surface, crops, trees) is just nice to have...

Also the turn back fails the “single engine philosophy”, my cross-country is not done on paved runways, it’s only in twins where making a runway back falls under “past VMC, you have to do it or at least die hard trying”...

 

Edited by Ibra
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On 11/9/2020 at 9:44 PM, N201MKTurbo said:

This is what happens when you come up short.

This happened at KCHD on Friday. The pilot had an engine failure after takeoff. He tried to return to the airport. He came up a little short. 22R has about an 8 inch edge at the end of the runway. It took off his nose gear and flipped the plane. I believe everybody is OK.

73CF38D1-4276-45D6-A836-17FF86FF8AA6.jpeg

https://www.azfamily.com/news/two-people-ok-after-plane-crash-at-chandler-municipal-airport/article_7654ffea-2047-11eb-a669-aff97878644b.html

 

Making the airport vs. making the runway.   I think making across the fence should be the focus.   If you make it to the runway that is a bonus.   This is assuming that the airport is surrounded by more hostile terrain vs. the nice grassy areas surrounding the runways.   There has been alot of discussion about lining up for runways.   F it.  just get to the airport fence.  If there is a runway there and you still have flight left in the wings then go for that.   I was close to a runway so I was able to get it on the runway but I was 25 feet away from putting it into the dirt.  Gear is a speedbrake.   it should be optional also.   

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The antidote here is there was this couple trying to make the airport.  Probably a fuel issue.   They then went for a street in a town nearby.   Made the street, but put it down so hard that the whole plane was wrinkled, and killed them both from G force.  But straight approach and straight landing on the street.  Bad delivery.

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1.  As Bob Hoover is quoted, "Fly the airplane as far into the crash as possible"

2. All of these decision points (altitudes) should be made long before the throttle is advanced for takeoff.  Airborne decisions take time ... and are often incorrect.  Make the decision and stay with it all the way.

3.  And the biggest one.  Don't stall.  Odds of survival go way, way up.

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2 hours ago, Blue on Top said:

2. All of these decision points (altitudes) should be made long before the throttle is advanced for takeoff.  Airborne decisions take time ... and are often incorrect.  Make the decision and stay with it all the way.

The main thing is to stick to your ground decision, there is no new data or new information up there...

The last time I did the maths, the wind matters more to where you set that height decision, if it’s windy, the last thing you want is to crash badly at the start (now end) of the runway which is guaranteed if you “turn back quickly”* and you had more height than you should to make a low energy tailwind glide & landing...

In no wind things are way easier, assuming climb gradient is roughly you glide back gradient, then you only care about the turn radius & the height loss as usually the takeoff distance is bigger than the landing distance and how that compares to runway length (without even thinking about height loss and gradients and winds the turn diameter in nil wind at +80kts and 45deg is 1000ft, I hope I still have lot of runway behind more than what I have remaining ahead)

When it’s windy, the takeoff distance into wind is way less than the landing roll with tailwind, and you have to think about your steep climb gradient and shallow descent gradient as well as the turn radius & the height loss and how things compares to the overall runway length, otherwise turn back past some bigger height may still put you in a situation where you have lot of energy to burn, then it’s time to think about the whole 360 into wind, just like before !

I think the ultimate criteria is to reverse the thinking via some “energy symmetry”, you can only turn back safely on active runway if you can takeoff with tailwind on the opposite runway, which is still a convincing answer for someone who says what if you have no landing options ahead with takeoff into wind on 27? (e.g. dragons, trees, houses...), well you takeoff on 09 with tailwind and turn back and land ahead 27 into wind if the engine quits :lol:

*Of course one does not need to “turn back quickly” but I was lucky gliders had airbreaks to help with the few cases when too much 180 action did kicks in ;)

One thing I wonder about and I did not figure out if you have to press the foot breaks tight on (high speed) touchdown? Or does it even matter?

Edited by Ibra
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I think we've bounded it.

Many have noted success in simulations from 1000'

Don Maxwell proved by actual experience that a 180 is impossible at 600' (He made a 45 deg turn to another runway, caused the controllers in the tower hit the floor and extended the gear at the very last instant). 

Skip

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The decision altitude(s) for the flight should not be hard numbers ... until the pilot advances the throttles.  They vary with WAT conditions (Weight, Altitude Temperature), runway length, wind, available runways, airport surroundings (buildings, roads, open fields), etc.  Every takeoff is different.  We should also be thinking about this while we're cruising, too.  Sailplanes have "rings" on their GPS maps of where it is possible to land ... and they are always "engine out". 

Plan the flight (including takeoff).  Fly the Plan.  Oh crap, my Flight Test background is showing its ugly head..

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Looking at M20J POH data, it seems impossible to do the impossible 180 back turn with 25kts headwind from literally any EFATO height, even with perfect tight height loss and zero turn radius (say you are magically back to 50ft above the runway on opposite direction :D), there will be barely any runway left to land on safely with 85kts touchdown ground speed, but one is far more lucky landing ahead with 35kts touchdown ground speed, even if that means into some trees 

Landing back on the cross-runways is completely different to 180back to active runway, say 15kts crosswind is from right and you have a “medium height engine failure”, you turn left 270 deg and land well established into that 15kts now headwind while beneath you is a full length cross-runway not just 1/2 of it as you you have drifted left

The 270 back to the cross-runway, does sound like an efficient way to maximise your vertical/lateral manoeuvring with respect to runways plus it maximises your runway landing distance while minimises your ground speed, about all what you need for a good win-win, the impossible 180 (actually 270) turn back to the active runway does none of those and leave everything as bet on exceptional piloting skills and luck

I understand the survivability of any landing or crash relates to square of ground speed, stopping distance which defines overall “G hit” then energy transmission & dissipation (metal/obstacles getting bent or breaks/fuselage heat) which decides how much is passed through to the pilot (for stopping distance the type of the landing surface does matter for aircraft re-use but those who landed gear up in airports or off-fields could argue that it’s less relevant for pilot survival if it’s done in a controllable way at slow ground speeds, it does not have to be a paved & painted runway, a taxiway or farm field would do)

Edited by Ibra
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On 11/11/2020 at 10:35 PM, carusoam said:

Pete,

Can you estimate the bank angle and degrees of attitude you used with the C152 during the turn...

I have an aggressive mindset... it’s the right vs. wrong I want to learn more about... :)

I think the scary part of the engine out... is the silence... that’s scary enough...

Steep bank while pointing at the ground is icing on the cake...

Best regards,

-a-

60 to 80 dg. Its a rapid turn. Descent is a function of time. Ice?! No bueno:)

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