If ever a horse was reduced to molecular pulp post-mortem, that would be the runway turnback maneuver. Somewhere during this endless rehashing, it has become known as “the impossible turn.” Why this is so is somewhat baffling given that any number of authors, instructors and illustrious experts have proved that it’s anything but impossible. But sometimes it is and when it is, a smoking crater is often the result.
Now comes EAA with a new team to study the problem one more time with an eye toward possibly incorporating this training into private pilot and sport pilot training. Do we really need to rehash this one more time? Yeah, maybe, if only to produce some fresh data-driven study to once and for all stamp out the idea of the impossible turn. It was never impossible. Maybe difficult at times, ill-advised at others, but “impossible” encourages lowest common denominator thinking that, in turn, stifles development of higher piloting skills.
Just based on the initial announcement, it sounds like EAA has and will devote sufficient resources to cast some new light on this subject. In this presentation, former astronaut Charlie Precourt, EAA’s vice-chairman who will lead the study group, presented preliminary data on turnbacks. If the conclusion follows these findings, it will be that turnbacks are a bad idea. I have researched the issue several times myself, but journalistic forays into this thicket are necessarily shallow and conclusions rest on limited examination. We’ve seen a handful of demonstrations on how this maneuver can be trained, set up and executed. AOPA’s Air Safety Institute recently did this video on real world performance of turnbacks. I’ve corresponded with Brian Schiff on this topic and he’s done some excellent analysis published in this paper. In 1982, future astronaut Brent Jett did this study at the Naval Academy, under the guidance of veteran instructor David Rogers.
So perhaps we can once and for all dispense with the idea that the turnback maneuver isn’t a doable thing. It clearly is. What EAA can do, if this is done right, is to dig into the outcomes. Where and why have these attempts failed? And where and why have they succeeded? In my own research, the latter proved difficult to pin down because the success stories don’t necessarily make it into accident record, although the fatal accidents definitely do. This skews the argument against the turnback with data that’s biased in ways we don’t understand. A research project with more resources may be able to flesh this out. If so, it would be helpful.
Further, a realistic assessment of outcomes can inform training standards and recommendations. And perhaps we can dispense with the knee-jerk notion that pilots are too poorly trained or under-skilled to even attempt a turnback, landing straight ahead even if what’s ahead is the worst landing site imaginable.
From my own research on this topic, I remain agnostic. I think the turnback is viable and even superior in some circumstances, so I have never ruled out considering it or teaching it. But I’m not an acolyte of the method because if a pilot hasn’t trained it and analyzed the unique circumstances of the takeoff, we know by tragic experience that the outcome can be a fatal crash.
I hope EAA’s approach reveals enough additional crash data so we can understand the demonstrated risk in numerical terms. Heretofore, it has been colored by too much emotionalism.
Update: David Rogers contacted me with some additional updated and revised information on turnbacks. The full index page is here.
Paul,
I’d recommend the following white paper;
Single-Engine Failure after Takeoff: The Anatomy of a Turnback Maneuver
Les Glatt, PhD., ATP, CFI-AI
July 25, 2020
It can be found in an internet search. It has a lot of equations, but near the end is a set of maneuvers that can show the possibility of the ‘turn back to the runway’.
I hope they spend time considering “turning to a better option”. You don’t HAVE to get back to the runway. Sometimes just inside the fence is better than urban sprawl outside the fence. So you DON’T have to get back the runway you departed. Which involves attempting a total of 270 degrees of turns. You just need to improve the outcome. At my home airport of KUUU – NO option requires trying to return to the runway. But spirited and positive maneuvering is called for to better the outcome.
Rwy 04 – 10 degrees left (so “straight ahead”) into the safety area the airport purchased for just that purpose.
Rwy 16 – Straight ahead into the vineyard. Avoid the powerlines on the crossing road – go over or (gulp) under – but don’t stall into them.
Rwy 22 – NOT straight ahead – urban nightmare. Best bet is 100-120 degrees left into that vineyard. Not the school football field.
Rwy 34 – NOT straight ahead – another urban nightmare. 90 left into the tiny/small/postage stamp field behind the car dealership or if a bit further down the line about 80 right into the Rwy 04 safety area.
—
And looking at some of the EAA preliminary data they looked at and shared on a couple of webinars….. For people who got it wrong – the result was a stall into the ground. But the missing bit on the data was WHERE? On the turn? Or the downwind landing? Go practice a downwind landing. With the wind on your tail – you are travelling over the ground at high speed. If you attempt to “normalize” the sight picture to a “normal landing”. Your ground speed will be trending OK – but you WILL run out of airspeed and stall.
With the teaching about turning around to a better outcome must come the consequences of the unusual, and probably fast, landing picture. Fly the airspeed to stay in control – ignore the observed ground speed.
There are so many factors involved in making the turn back to the airport. The plane you are flying, winds, the pilots skill, where the engine quits and so on. The safest course is to just land either straight ahead or slightly to one side of the runway heading. If you can make a controlled crash at the slowest speed possible into things that will give way you most likely will survive. (If you have shoulder harness). Stall and dive into the ground or spin you will not live.
It’s the safest course for whom? There are some airports I have been to where straight ahead is one of the worst options due to heavily populated areas. Sometimes it may take more than 30 degrees of turn to find a landing spot that doesn’t unnecessarily put people on the ground in danger.
What pilots should be taught instead of the “only land straight ahead or just slightly left or right” is to have a feeling of the energy state of the aircraft after takeoff and to land within the safest area you can reach before exhausting the energy available.
To me it’s like any other max performance maneuver: Trying to do it for the first time in a real emergency is a really bad idea. If you’ve trained and practiced for it in your specific aircraft you should know whether or not it’s possible, and if it is you should include it in every takeoff briefing.
I have performed this maneuver numerous times at 500 AGL in MY Bonanza. My examiner for my instrument BFR, an F-16 instructor, KNOWS the individual characteristics of MY plane. Those characteristics dictate the height (minimum 500 AGL, in MY Bonanza), bank angle (50 degrees, NOT 45!, in MY Bonanza), and of course, speed (113 Kts, gear up, flaps up, neutral thrust, in MY Bonanza). These numbers WILL CHANGE and ARE CRITICAL depending on the plane, and its configuration. To borrow a phrase from Lou Holtz, I DID NOT want to apply a PERMANENT solution to a temporary problem.
Paul: I am sure you know that “the impossible turn” is a required item for a glider rating. So, it is required to practice a rope break at a low altitude or a candidate won’t get their certificate. But, virtually all gliders can do a turn back from 200 ft or so, so this is a good maneuver.
The EAA study is a waste of time–we already know that some aircraft can do the turn and some can’t. And the ones that can do the turn can’t do it all the time. The right answer is well-known (and in one of the other comments on this page)–don’t try the turn for real unless you have practiced it in the airplane you are flying (or one with the same engine/airframe combo).
But you aviation writers need to have something to write about!! 😉
Stay well and best,
Vince
“we already know that some aircraft can do the turn and some can’t”
False. ALL aircraft can. It’s just a question of how high they need to be first.
I’ll correct myself. I suppose if the airplane’s rate of climb isn’t high enough and glide ratio is low enough, then it could be far away enough and not high enough to make it back to the airport.
For 30 years I’ve taught–based on numerous exercises and flight with experts, and by putting hundreds of pilots through the exercise in a type-specific Beech Bonanza simulator–that the decision isn’t between “straight ahead” and “land on the reciprocal runway.” Instead, it is a range of possibilities that depend on the runway length, the weather and the pilot’s takeoff technique…and heavily dependent on the type of airplane.
For example, my experience is that the turnback to the runway is all but impossible in Beech Bonanzas from just about any altitude, unless the runway is extremely long, the winds are just right, and the pilot has substantial recent experience with the technique and executes it perfectly. In other words, it’s highly unlikely to be repeatable in the surprise of an actual emergency. However, it may be possible to turn up to 90 degrees and line up on a good option, or even make a full 180 degree turn and end up on the flat area of the airport grounds, depending on the current circumstances when the engine failure occurs. As height increases an ever-increasing range of options becomes available.
But at least in Bonanzas, completely losing an engine immediately after takeoff, making the 240 or more degrees of descending turn in the full Glide configuration, putting down the landing gear, touching down and rolling to a stop on the runway then calling the FBO to come tow the airplane in is the very LEAST likely outcome.
AOPA’s recent video confirms this for THIS TYPE of airplane. Two months ago I did this exercise with Scott “Gunny” Perdue as part of my annual Flight Review and confirmed that either the airplane is too low to turn and make it to the runway or, if high enough to line up, too far away to make it back to the pavement. Gunny recently videoed a repeat of the exercise in his F33C aerobatic Bonanza and reached the same conclusions. Both AOPA and Gunny join me in speculating this is because of the Bonanza’s wing loading and unusually high Best Glide speed, which increases the radius of the turn and therefore requires more time (and altitude) to align with the reciprocal runway.
We all accept that different types of airplanes have different takeoff, climb, cruise, low speed and landing performance. Yet in the context of this discussion often it seems it’s assumed that all airplanes glide alike, that the A36 I fly will turn back the same as the J3 flown by Paul.
Summing up: I’m very glad EAA is apparently going to sink significant resources into studying this. I hope as they do that they take the very type-specific differences of different airplanes into account when issuing conclusions and recommendations.
Thanks. I think you nailed it!
Bogus, a Bonanza is just an airplane.
I’ve done the turn in a Yankee (which is also a higher wing loading plane and also needs to be flown fast). Learn your plane and practice airspeed management. If you don’t then either way you go means you’re still screwed.
This has become the most over thought out issue. I’ve seen thoughts about analyzing speeds to use, bank angles, graphs, and the list of aerodynamics goes on and on. This ain’t rocket science. The entire event takes place in basically a matter of seconds….that’s it, less than a minute probably. No time to get out charts, analyze and on and on. The correct answer for this very brief event is practice, practice in your plane. Determine what altitude is needed. You’ll be doing it quickly. Know the altitude needed before takeoff every time. Know what opportunities for forced landing lie ahead vs returning. And then you have the answer. No studies needed. But, one size does not fit all. Remember, you only have the answer now for that particular airplane. Another airplane, you got to do your practice and evaluation over again. Too much deep thought in this quick and simple maneuver. My opinion.
And to add in the one size does not fit all considerations, and this has been mentioned before, the surface wind. If you have departed in a strong surface headwind, say 20 knots, then landing ahead and hitting whatever at your near stall speed less 20 knots, might be preferable to trying to land at your touch down speed plus 20 knots. If I’ve done the math right, that is a 40 knot difference in ground speed or impact speed. And in my taildragger, a 20 knot tailwind landing would probably end up with a wrecked airplane anyhow. Thing to analyze before you open the throttle.
Your link, “In this presentation, … Charlie Precourt …”, doesn’t seem to work -for me it just circles back to your own post.
Did you mean to link instead to “https://www.eaa.org/videos/6193816644001”, entitled “Webinar- So You Think You Can Make a 180 Back on Takeoff? An In-Depth Look at Engine Failure Option”, from 2020/09/22?
Link fixed. Here it is again.
https://www.fsana.com/180-turnback_to_airport_is_bad.php
I have a simple formula for takeoff which I have never felt need to revise. Always use the whole runway,no intersection takeoff,rotate and clean up the plane,NEVER TOUCH THE POWER LEVERS UNTIL PATTERN ALTITUDE,climb at best angle to pattern altitude. Altitude is money in the bank. In only slightly over one minute a Bonanza will be at pattern altitude after rotation,and at 90mph will only be approximately 1.5 miles from the rotation point.
Best angle will keep you close to the airport, but it won’t gain you the most altitude in the least amount of time. It will also require a bigger push if the engine quits than climbing at best rate.
The question is, what does the math show for both your distance from the airport over time and your altitude above the ground over that same time. Sometimes you might have the altitude but not the distance, and other times you might have the distance but not the altitude. You obviously need both to make it back to the airport. But maybe making it most of the way back to the airport is good enough, even if you end up short of the runway.
The real question is: can you make the impossible turn from the altitude and airspeed that you have *after recognizing the situation and deciding to act*. If you are at 600 feet when the prop stops, how long until you’ve made the decision? Certainly you will be much lower than 600 feet.
Where my plane was based [before I moved] there were farms and soccer fields in the valley that followed the line of the prevailing runway. There were also high-tension transmission lines, and ducking under is the only save move. But options, in any case. Going the other way, a hill, with a major river before it.
As someone who has practiced this maneuver in my own plane at a safe altitude over unpopulated farm areas with nice grids for visual reference and analyzed the GPS data, like many things in life, it depends … depends on pilot skill, proficiency, whether you briefed it to yourself just before takeoff, aircraft type, wing loading, stall characteristics of your plane, AGL when the engine quits, what’s around the airport, size of the airport property, winds, etc. The Impossible Turn is clearly possible under many circumstances. I would not recommend it for most pilots because most pilots aren’t going to get trained and stay proficient in it. It is a wild maneuver flown at 30-45 deg of bank near stall with very high turn rates if you’re maximizing the maneuver (I also do flight mechanics in my day job and have looked at the physics). That will freak a lot of $100 hamburger pilots out at the worst time. But, as others have noted, in many cases you don’t need to actually do the 180-210 degree turn and actually make it back to the runway. Sometimes just making back inside the airport perimeter is good enough, and sometimes there are much better options just 90 degrees away. At some airports, there’s just no way I’m going straight ahead or even slightly off of straight ahead. No matter what I do there, it’s going to be a KNOWN bad outcome for either me, the people on the ground, or both no matter how well I fly to the air-ground interface. Staying proficient in the maneuver gives me additional good options. So bottom line … you need to develop and brief a plan for engine out on climb out for every takeoff, and sometimes that plan will be the Possible Impossible Turn and sometimes it won’t be. The people who say always go straight ahead are just looking at a broad brush stokes given all the data. They aren’t accounting for uniqueness in the variables that will allow you and your airplane to do the maneuver safely. This advice may be good for students and otherwise low-proficiency pilots, but it is frustrating for the rest of us.
In addition to many useful and relevant remarks made by esteemed colleagues I wonder whether some part of the ‘lore’ was born from very, very old types on which the gyroscopic precession afforded by the rotating engine added additional dimension to the already narrow margin of lift on a very draggy and low speed aircraft. Albeit I accept it wouldn’t be rotating much if it had failed, although it might be windmilling.
“If ever a horse was reduced to molecular pulp post-mortem, that would be the runway turnback maneuver.” I knew from the outset “that’s Paul Bertorelli!” Reminds me of the scene in Blazing Saddles–where Taggert remarks, “Goll-ee, Mr. Lamar, if you don’t use your tongue…………” (laugh)
Back to the subject at hand–preflight planning. Most people in these discussions assume the worst–a sudden and catastrophic engine failure at the worst possible time–and considering the consequences, well they should. Multi-engine drivers do the same thing in their takeoff planning–but there have been pilots that attempted to cage an engine that was still producing power–and lost it.
Single-engine pilots should be wary of the “one size fits all” solution. In most engine failures, there are early warning signs, and more often than not, it is a PARTIAL engine failure–not total. Don’t be like the multi-engine pilot, and take inappropriate action.
Most of the discussion has centered around the sudden and catastrophic failure, and the decision to land straight ahead or turn back. In most engine problems, there ARE other solutions–IF you have considered them in your planning. “Use all the runway–know what is off the end of the runway you are using–climb at Vx”–all are good planning. What’s needed are DECISION POINTS–most people agree that at 1000′ AGL using the aforementioned good practices, options abound. Very few mention the option of landing on a cross runway–at our airport, I know that if I have a total engine failure below 300′ with my LSA, I can land on the remaining runway. Above 300′ AGL, I have the cross runway. At 600′, I can turn downwind for a close-in into-the-wind pattern. A PARTIAL failure gives even more options.
It varies by airplane–there is no “hard and fast rule.” With a Cherokee 6, I’ll want at least 500′ to turn to the crosswind, and 800′ to turn downwind. With a Cessna Caravan or Mooney (both with glide ratios over 10:1–I can do even better. With the glider, as mentioned, 200′ is enough for a 180 degree turnback–but you may run off the end of the runway if it is less than 2500′ long. With the helicopter–there IS no appreciable glide, but then, you don’t need a runway, either–but you DO need to consider obstacles in takeoff planning, and you DON’T want to land downwind.
In short, there IS no “hard and fast” rule–“it depends”–on the airport–the surroundings–the wind–full or partial engine power–and the pilot. I would hope that the EAA (and the FAA) don’t adopt “hard and fast rules”–give pilots the facts, and let THEM sort it out. That’s why they are PILOTS, not “Airplane drivers.”
Jim…not Vx…. the climb should be “Best Rate”…Vy…in order to gain the most altitude over TIME. (wink)
I have had any engine failure at 400 ft in a 1980 Mooney M20J. The outcome was no injuries and a little damaged to the left wing outer leading edge panel. Paul interviewed me about the incident for one of Avweb’s most popular videos. I’m hoping the EAA investigation addresses 1) training, 2) initial response 3) pre takeoff situational awareness 4) follow though. 5) time. Here are the key learnings from my experience.
1) Training: months before the incident, Paul and I went flying on windy day with significant cross winds. I was paying most attention to keeping the aircraft lined up with the runway and upright. We were bouncing all over the place and yes, I was sweating. During a climb out, Paul says, ” watch out for that aircraft” and points to the left. While I’m looking, he pulls the power back then he yells”, put the F**king nose down.”
2) Initial Response: When the engine quit in real life, I heard Paul yelling in my headphones “get the f**king nose down”. I don’t know why but I responded quickly and instinctively establishing best glide. This gave me time to assess, check fuel and ignition, think and come up with a simple plan.
3) Situational Awareness: Due to my pre takeoff situational assessment, I knew there was a mobile home park straight ahead, an industrial park to my left and an open saltwater marsh to my right. The only option was a 180 turn to the right land in the marsh.
4) Follow through: My plan was to maintain best glide speed above all else, execute a shallow 180 turn, aim for the middle of the flattest part of the marsh, touch town at stall and keep flying until the crunching stops. The last step is very important because when the aircraft touched down, the nose wheel started dragging in the mud and the aircraft started to come up on the nose. I pulled the elevator full aft and that prevented the aircraft from flipping.
Lastly, 5) time. I have run through what happened many times and I estimate that it was 7 seconds from the time the engine quit to the time I was landing in the marsh. Think about that. Just 7 seconds. Engine stops. 1000, 2000, 3000, 4000, 5000, 6000, 7000, Landing!
By the way, I should have also mentioned that if I followed the the conventional wisdom of the impossible turn, I would have land straight ahead. As the insurance agent said when he surveyed the situation. “You picked the least expensive option. A straight ahead landing or landing to the left would have resulted in loss of life and at least $10M payout. We are happy to payout on the hull insurance.”
Please take a look at the glider training practices that teach and demonstrate 180 degree turn backs from rope breaks during aero tow launches. (usually safe at 200 ft or more). Glider pilots train and practice this, we still have decision points before takeoff for straight ahead landings, slight left or right turns, or the return to the runway. Glider type, airfield, winds, etc still make the decision points unique for each launch.
There’s Absolutely no landing with a broken aircraft that has a guaranteed good outcome. No matter how many ‘Impossible Turn-Backs’ or ‘Power-Off Landings’ you practice.
“FUEL, IGNITION & LUBRICATION” The three most common non-weather reasons why Pilots don’t land at their intended destination. Just sumping the fuel tanks is not always adequate. If the aircraft hasn’t flown for a while shake the fuel tanks, wait a while and sump again. Warm up the engine and run it at a higher power setting for four – five minutes. Use Carb-Heat and Fuel Pump if so equipped before T/O.
If the Magnetos have an Impulse Coupling, the spring can be broken. A broken Impulse Coupling Spring can cause a random change in timing that can reduce the power or back fire and shut the engine down. Check the Mags several times at different power settings before T/O.
Most aircraft engines are based on engineering that’s over a hundred years old. The manufactures have written one publication or another that covers anything that can go wrong. “FAR 91.403 a. The owner or operator of an aircraft is primarily responsible for maintaining that aircraft in an airworthy condition, including compliance with part 39 of this chapter.” The cheapest and most effective thing you can do that prevents Emergency Landings of any kind from any altitude… KNOWLEDGE and time/money spent on Preventative Maintenance.
My intention is in each new airplane I fly, to go to altitude on a calm day with an instructor and gather the data to plug into Brian Schiff’s worksheet. If doable, I’ll incorporate that minimum turnback altitude into my pre-takeoff briefing. I’ll also practice the maneuver (at altitude) to stay proficient in case the day comes when a turnback is my only option.
Sounds good to a point, but IMO your chances of performing the maneuver as efficiently at low altitude when you have the ground and obstacles staring you in the face will not be as likely. And, how often is a turnback your “only option”? Maybe if the airport is surrounded by jagged granite rocks? How often is the situation so extreme? That would mean that prior to reaching a turn back altitude, there would be a significant period where you have NO option, not even a slight one. I don’t think I would operate out of such an airport. I think areas surrounding most airports offer at least some options, even if they are not great, and a turn back isn’t necessarily the only option. Above all, I want myself and my passenger to survive, and I’m sure you agree. Airplanes have landed in trees and people have survived. If an airport genuinely offers only the turnback option to survival, I’d probably avoid going there.
Almost never said, if the takeoff runway is shorter than a given length (or the airport is not “large”), by the time the aircraft climbs to an altitude high enough to execute a turn back, the airplane will be too far away from that runway, or even the entire airport, to get back to it. In such a case, trying the turn would be a futile risk because the airplane will not land on the airport no matter what you do. Every plane will be different. For mine, the shortest runway to even consider a turn back would be roughly 4000 feet, and that’s with virtually no error margin. I would also need about 800 feet AGL to start with, again absolute minimum. How much steel/ice is in your nerves? For myself, if the takeoff runway is shorter than 4000 feet, the idea of turning back to the same runway does not even enter my mind. Knowing this before the takeoff begins will prevent hesitation from limiting your chances of succeeding with an alternative option. If I am not familiar with the surrounding geography of a given airport, I will study satellite photos or whatever else I can obtain to formulate at least some sort of a plan for a least risk off field landing before the situation presents itself.
There’s a lot of talk and hand-waving about this topic, including claims that there are no rules of thumb. So, here are some rules of thumb.
1. For an early engine failure, it’s mostly about your airplane’s best glide speed, and pilot skill. If it’s a slow airplane (best glide speed less than 65 kt, say), it may make the turnback in an early engine failure, and may even do it easily – if the pilot can nail a 40-45 degree banked turn at the proper speed, which requires a lot of skill and practice. It’s called the Impossible Turn because they were teaching pilots for WWII, and the airplanes were relatively fast: it wasn’t possible with any amount of pilot skill. By the way, you should NOT try to fly the turn too slow: you need your minimum sink speed multiplied by 1.4, not less. (Explanation: minimum altitude loss in the turn itself – which is what matters in an early failure – is a function of glide angle in a 45-degree bank, and the square of the airspeed. Glide angles of light aircraft are in a fairly narrow range between 7:1 and 10:1 or so – so, some planes will take ~50% more altitude than others. But best-glide airspeeds differ by a ratio of 1.5 or more, giving a factor of 2.25+ in altitude loss, which is the bigger consideration. A Piper Cub or anything with LSA-like performance has a really good chance of getting back after an early failure, assuming a highly skilled pilot; a Bonanza or a Malibu has little to none; a Harvard or P51 has none at all, regardless of pilot skills.)
2. For a LATE engine failure, it’s all about glide ratio vs climb ratio, and pilot skill is secondary. If you’ve climbed to more than, say, 5 to 10 times the altitude you lose in a 180-degree turn, then if your glide ratio is flatter than your climb angle you may be able to make it back as long as your turnback is competently executed (35 degrees of bank should likely be fine). The Cub, which has a good shot at the turnback after an early engine failure, can’t make it back after a late engine failure, period. The Bonanza, which can’t make the turnback after an early failure, might well be able to make it back from a late failure. The Bonanza should climb at about 1,200 fpm at 100kt, an angle of roughly 8.5:1, and should glide at about 10:1. If we allow 1,000′ for the turnback itself (illustrating the point – a Bonanza may need more) then we have that so if it’s high enough it may make it back. In fact, it could do it from a starting point of 6,700′ (!), so it would need to keep climbing at Vy for at least 6 minutes. The general formula here is [Alt Required] = ([Glide Ratio] x [Altitude Lost in a Turnback]) / ([Glide Ratio] – [Climb Ratio]). If you get a negative answer, you can’t make it back from a late engine failure at all. Here, [Glide Ratio] and [Climb Ratio] are expressed as a number, like 8.5 for a ratio of 8.5:1. Plug the numbers in for the Bonanza, with our 1,000′ turnback assumption: (10 x 1,000) / (10 – 8.5) = 6,667′. That’s with no wind, of course. But, you can adjust your climb and glide ratios for wind and compute a late turnback table for your airplane, if you like – just measure its actual performance at that density altitude first!
P.S. VERY rough guide for altitude lost in the early-failure turnback (in feet) is in the vicinity of [Straight-line glide speed in knots]^2 / 7. So, if your plane’s best glide is at 50 knots, you’d need roughly 360′ (and you’d make the turn at roughly 60 kt, which is 1.4 x minimum sink speed, and minimum sink speed is less than best glide speed). If best glide in straight fligtht is 60 knots, roughly 515′. If it’s 70 knots, roughly 700′. If it’s 80 knots, roughly 915′. If it’s 90 knots, roughly 1,200′ (!). I’m ignoring the effect of glide ratio here: a sailplane can turn back in substantially less than 360′, and a Pitts will not do as well as this rule of thumb suggests.
For the late-failure turnback you need only about 60% of these values.
I’ve done it from 400′. But not just a turn back, but a full 360 back to the runway. But in my last engine failure (out of four previous ones in 61 years of flying) I wasn’t so lucky. It occurred at 200′. Straight ahead wasn’t an option. Turned 90 degrees and put it into some shrubs. I walked away without a scratch, but the airplane wasn’t so lucky.
Already this year, three Wisconsin flight instructors with advanced flight certificates including one pilot with an ATP rating have perished attempting to return to the airport after experiencing an engine failure during the takeoff phase of flight. Feel free to analyze the aerodynamics relevant to your particular aircraft yet be aware that you might add yourself to the list of pilots who killed themselves and passengers with failed attempts to return to the airport. After power loss on takeoff, I choose to lower the nose to preserve airspeed, to land into the wind, and to not come back to the airfield.
At my airport, “land approximately straight ahead” is a death sentence – it’s industrial space out there, with steel, powerlines and buildings everywhere. So you start to think about these things: you might as well.
A lot of good stuff from everyone. Straight ahead though is too limiting. It is common here in the UK to teach: 1. nose down best glide speed, 2. select the best available landing sight anywhere ahead between the wing tips, 3. “Mayday” if time permits, 4. shut down actions (isolate fuel): 5. Open doors/hatch, 6. Passengers adopt crash position. 7. select final flap as required 8. Master switch off. This is a lot to do in less than a minute from only 500ft agl. Remember the checks will take a lot longer to complete than the touch controls practiced during training.
I like the idea of positioning the aeroplane to landing anywhere on the airfield if not on a runway, this should be possible, in my opinion, if the height at failure is well above 500ft. To save life than to save an aeroplane must be the priority though. The best glide speed is too low if angles of bank are required over 20 degrees; the nose should always be lowered and speed increased before any increase in bank – I mean lowered! The pilot will experience a rapid drift sideways during the crosswind turn and with large angles of bank, being close to the ground, this will be disorientating and can be overwhelming. The descent path will be much steeper and much more rapid than the normal approach. Add the increased downwind ground speed, together with a changing drift then a loss of control should not be unexpected. During all this the pilot is likely to be in a state of shock. This, ladies and gentleman, is the reason for teaching the landing ahead and is little to do with calculating the aircraft’s performance. I’ve never heard of the term: ‘The impossible turn’. It is pointless to me to prove it can be done.
Many things are possible with perfect conditions and no shortage or practice. But, conditions are not constant and very few non-professional, general aviation pilots remain all that proficient in normal procedures, let alone with emergency procedures.
I won’t even get into the multitudes who have no understanding of the dynamics in a turn and the effect on stall speed. And, that includes many supposedly professional pilots.
By this account I’m betting Paul is not an active instructor who teaches nor frequently gives flight reviews and sees the average pilot out there.
Except stalling is not about aispeed, it’s about angle of attack. And we’re not talking about maintaining altitude while turning. As long as you keep the nose pointed down sufficiently during an engine-out glide so that you keep the angle of attack low enough, you can bank rather steeply to convert the lifting force to a turning force and get turned around rather quickly. The trick remaining is to have enough altitude (potential energy) to get back to the best glide speed (and thus a more normal descent rate) once you roll out from the turn to make it back to the runway.
You learn a lot about how aerodynamics work in a descending turn by flying either an airplane with a poor sink-to-glide ratio, or a helicopter (an aircraft with a poor sink-to-glide ratio). These aircraft also help you learn to resist the temptation to pull back on the controls when you see a lot of ground in front of you so you can properly time the round-out.
What does bank angle do to the direction of lift? It angles it away from vertical while the angle of gravity remains constant. So, you first have less lift countering gravity.
Next, the load factor increases in a bank. In a 30º bank, the load increase only by about 1.15 times. At 40º, it increases by about 1.25 times. But, in the “Impossible turn” scenario, there is this tendency to bank much steeper. When you get to 60º, the load doubles to twice that of zero-G flight.
This is another issue the average general aviation pilot is not going to be all that cognizant of, if at all. And, when the stall horn starts sounding in that steep bank will they drop the nose?
Yes, I know speed has nothing to do with the stall. It’s all about angle-of-attack. And, while the subject pilot may not be trying to maintain altitude, they will be trying to stretch it and most often beyond what is possible.
Lastly, which way will they turn? Which wing has the stall sensor? If it’s to the direction of the wing with the sensor (often the left wing), they may not have that warning. The inside wing will have the least AoA.
Again, it’s all about how skilled and proficient the pilot is. Very few are.
“In a 30º bank, the load increase only by about 1.15 times. At 40º, it increases by about 1.25 times. But, in the “Impossible turn” scenario, there is this tendency to bank much steeper. When you get to 60º, the load doubles to twice that of zero-G flight.”
That math is true only while in a level turn. Once you start climbing or descending, that math is no longer accurate. If I simply let the nose drop to maintain the trimmed airspeed (AoA), the bank angle will control the rate of turn and rate of descent but not affect the load factor appreciably. It’s just that we have been conditioned to maintain a constant rate of altitude change (i.e. constant rate of climb/descent or constant altitude) while turning, so the natural tendency is to increase the AoA and load factor to keep a constant rate of descent when what we actually want to do is the exact opposite.
The skill is in controlling the bank angle precisely, not the AoA. If the aircraft is trimmed properly, it doesn’t take much skill to maintain a constant AoA. But it does take a good degree of discipline to let the aircraft do its thing while the lizard brain is focusing on the ground filling up the windscreen. And I have found that helicopter training (specifically, autorotations and especially turning autorotations) helps with learning that discipline. I suppose an aircraft that has “flying brick” qualities would provide the same training effect.
Yes, the load decreases when descending. But, what caveat did I add that always gets thrown in there by the lesser-proficient pilot?
An attempt to extend the glide by pulling back on the yoke.
If you’ve not figured it by now, I’m entirely opposed to encouraging this kind of maneuver because I saw far too many pilots who acted like currency and proficiency are the same thing. I won’t even get into the number of the school’s renters who would come in just to fly three approaches every three months.
“you can bank rather steeply to convert the lifting force to a turning force and get turned around rather quickly”. Yes. The timeframe of the turn is a critical factor I think generally not appreciated sufficiently. While we know that a 60 degree bank reduces the vertical component of lift compared to 30 or 45, it significantly reduces the amount of time the airplane is in the bank. My best results have been when I banked at 60 degrees with ball centered and pitched to maintain best glide (65 in a Skyhawk), which keeps a safe cushion above stall. I’ve lost as little as 200 ft in the turn and it kept me remarkably close to the centerline (in crosswinds turn into the wind). But caution – the most important factor is pilot ability. Technique normally has to be good and that comes from training and practice. In 2002 at my airport, a pilot attempted a turnback and he lost control. The report said “About 400 feet, a nose-high, left turn was initiated back towards the airport”. He and his wife perished.
https://www.inflightmetrics.com/takeoff-advisor/
The EAA Take Off Advisor Project covers this issue very well. Consider participating. Everyone has their opinion and experience. But the key point made above is the need for proper training using a structured method that is aircraft and weather specific. Looks like the Take Off Advisor approach is on the right track.
Just for giggles – during one of the EAA webinars – it was mentioned (possibly tongue in cheek) that a Split-S might be the fastest and least altitude loss return method for some aircraft………..
So I can report after practicing at a safe altitude – it is possible to get my little EXPERIMENTAL pointing back the other way with only a 200ft altitude loss. It requires a very precise slow airspeed and pitch angle – both of which are likely to be met in an engine out on take off. But if you think I’m going to try that in the heat of the moment – think again – at my home airport I’ll go for one of the options I enumerated back up the comments section. 🙂
Lately I’ve read and seen several articles/videos recommending a review of the old-advice to avoid turn backs to the airport if an engine failure occurs after takeoff. This was brought to my attention most-recently during my bi-ennial CFI renewal course and I was MOST surprised to see FAA even reconsidering this manuever.
All promotions of this manuever aside…. Two things come to mind that frankly, I’m shocked no one seems to have thought-of …or at least have not mentioned in their mostly-favorable recommendations to reconsider… So I would like to bring it up for discussion:
Number One: AFTER takeoff….. if one suffers an engine failure (meaning loss of sufficient power to maintain altitude)…. the scenarios depicted which I’ve seen always make the engine fail AFTER the departure end of the runway has passed. No consideration seems to have been given that the majority of takeoffs involve runways sufficiently-long to result in available runway remaining straight-ahead. Also, no consideration/discussion is offered in the event SOME runway remains…even if INsufficient to come to a complete stop.
(Seems to me that it’s far better to depart the end of the runway decelerating with the brakes-applied… than to smack something in a dive or while attempting a near-aerobatic manuever.)
Number Two: None of the scenarios seem to recognize that most runways are open to other aircraft…and that any departure at any ordiary field may involve multiple aircraft waiting for departure. I can imagine a mass-exodus from the Fly-In Pancake breakfast and someone decides to turn back immediately after departure …Fully Expecting an Open and Vacant runway surface.
The numbers of times I’ve witnessed several aircraft lining up at the Hold Short line awaiting their turn for departure…and as soon as the airplane ahead rolls down the runway the next guy …lines up and waits…. then observing the departing aircraft leave the departure-end begins his own takeoff-roll….
when just about ready to get the tail up off the runway…. … the guy ahead suddenly Reverses Course in a high-speed turning manuever to return and …LAND HEAD-ON.…!!..?? WHAAaaa. ?
Number Three: None of the scenarios mention the fact that most takeoffs are decided to proceed AGAINST the wind….and that a Return to Landing involving a 180-degree turn onto the same runway will involve a DOWNWIND LANDING! …and that a panic-sticken pilot will likely be so concerned about the return that a nose-down rush-to-the-surface will likely result in an OVER-speed condition…. with a lot of opportunity for a LOONG-landing…. one what has suddenly become a short runway…….and facing that oncoming/departing traffic
I feel these are major oversights in the Brave New World of “turnback” promoters….and worth some thoughtful discussions in the community.
Those are all very good observations. All of your points would (should) be thoroughly covered in training. The trained pilot would consider exactly what options are available before the takeoff. Leaving an event as you say would probably eliminate turning back to the runway so that one would be off the list of options. But there may be a good option on another part of the airport property. Dealing with a tailwind landing would (should) also be part of the training and I agree is critical. But to that point, anyone who hasn’t already received some training on landing with a tailwind should question why. From day one in an emergency, you may be left with a downwind landing as the only option.
“What EAA can do, if this is done right, is to dig into the outcomes. Where and why have these attempts failed? And where and why have they succeeded? In my own research, the latter proved difficult to pin down because the success stories don’t necessarily make it into accident record, although the fatal accidents definitely do. I hope EAA’s approach reveals enough additional crash data so we can understand the demonstrated risk in numerical terms. Heretofore, it has been colored by too much emotionalism.”
Exactly. While the crashes make the news, the success stories do not. As a result, emotionalism results in arm chair quarterbacking based on experiences that do not replicate the circumstances that killed someone.
Zero thrust practice does not replicate a wind-milling prop, especially a constant speed prop at takeoff settings. Zero thrust does not replicate how an airplane behaves when it is now a glider flying through air changed considerably from its design tested performance with a properly operating, running engine at various power settings. Having suffered a total engine failure in a first generation Bonanza and currently owning a first generation Bonanza, I can attest to the flying qualities or the lack of them between an idling engine at “zero thrust” vs one that is producing no power combined with the drag of a wind-milling prop. The aerodynamics caused by a wind-milling prop are so far from the aerodynamics of an idling engine at so-called “zero thrust” as the east is from the west. As a result, the handling characteristics in a real emergency such as not only a loss of thrust but the completely foreign aircraft behavior when you are well behind zero thrust into the negative numbers of minus thrust…if that makes any sense. The whole airplane behaves far different. Pushing the nose over in all of that dirty air, that for many airplanes if not all airplanes, have never been tested during certification is the wrong wording. One has to virtually slam the stick/yoke into the panel and pronto with elevator/stab effectiveness totally different than when in the air of an idling engine. Rudder control is more vague forcing large displacement compared to that of an idling engine. Yaw stability is poor at best. Flaring takes on a whole new meaning more akin to a fixed wing version of a one shot emergency auto-rotation.
Counting ” 5 potatos” does not replicate the shock closely followed by denial of a real world emergency. 7-10:1 glide ratios are more like half that as Dana Nickerson well described of his Mooney loss of thrust experience. He testifies maybe seven seconds from start to finish of his emergency from 400 feet agl.
I would agree that many emergencies result in partial power being available. But rarely is it smooth. Having an engine shaking itself loose from the mounts still making some power is far from an idling engine at “zero thrust”. Adding the distinct possibility of the windshield obscured, cowlings coming loose, and the noise/smells of a failing engine adds further to the confusion including changes in aircraft behavior from the norm experienced in our practice of engine out emergency procedures.
Yet, some aviators manage to survive more or less intact under a takeoff loss of thrust, or cruise flight engine failures that we most likely never hear of. Yet those successes could shed enormous light statistically
Is there was a way of accessing the successes? Is there a way to replicate a wind-milling propeller? Is there a way to replicate the drastically different aerodynamics an airframe design must endure behind a wind-milling engine? Can the EAA replicate the changes of the propeller gyroscopically as it moves about in the mounts during a cylinder failure, for example? Can the EAA replicate the real time involved with recognizing and responding to a loss of take off thrust? These questions have to be answered for properly determining a safe course of action. All of these situations figure heavily into the “depends” answer beyond the academics of wing loading, bank angle, and lift vectors.
How to replicate these scenarios is the obvious challenge. However, without an effort probing into the outer fringes of the flying envelope under these emergency circumstances will result in another “depends” conclusion with continued great disparity among the flying community regarding training for these emergencies. Doing what has been done in the past will result in the same variety of conclusions we now have. Do what others do…gets what other have already gotten.
Personally this issue is a very good example of the aviation conundrum of “what pilots should do” vs “what pilots actually do”
What pilots should do with an EFATO: Within 3 seconds quickly pitch down to the glide attitude and then smoothly roll into a coordinated 45 deg bank maintaining best glide speed, turn 225 deg and then reverse the turn to line up with the runway
What pilots (way too often) actually do: They freeze in disbelief for 7 to 10 seconds and do nothing. By the time they pitch to the glide attitude the airspeed is well below optimum and may be close to stall. They then crank in a bunch of bank without enough rudder so the aircraft is not in balance. As the they get part way around the turn they see a windshield full of dirt and the runway at the outer edge of the windshield and unconsciously pull back. The airplane then stalls, starts to spin and impacts with thr steep nose down and banked attitude that greatly increases the probability of fatalities.
The accident record clearly shows that a turn back is much more likely to have a fatal outcome over a straight ahead arrival.
The good news is twofold.
1) The actual window of vulnerability is pretty small and,
2) An aircraft that crashes under control with wings level, and a level or better still, slight nose attitude is almost certainly going to be survivable regardless of what the airplane hits.
To survive an EFATO you have to do only one thing. IMMEDIATELY LOWER THE NOSE. This will ensure you maintain enough airspeed to keep full control of the aircraft flight path.
To make things easy I tell students if they are below 1000 ft AGL they should only turn to something that is within the view out the windshield and only turn enough to avoid major obstacles.
To emphasize the importance of getting the nose down as part of my mandatory takeoff brief I get them to physically push the wheel forward as they verbally announce the EFATO critical actions
I realize that I can, and probably will be accused of “dumbing down” flight training but I think we have to be realistic. Most recreational pilots fly less than 50 hours per year. There are IMO more valuable things they should practice, than perfecting a manoeuvre that requires a high degree of flying skill and is relevant to a very small part of every flight.
The best way to avoid an EFATO is to not have the engine fail in the first place. Far too many engine failures are directly caused by the actions or inactions of the pilot. The last real EFATO I am personally aware of resulted in a straight ahead arrival with a totalled airplane but no injuries. Almost a litre of water was drained from the selected tank……..
Having been flying since 1962 … I have had … more than my share of engine failures and other power or flight dynamics issues on takeoff .. probably due to my flying antique, unmaintained, overworked… and plain ancient junk …all over the planet .. and as a result of my hating to swim, hike jungles, or try to climb down from mountains … preferred yo.land back at airports … since in most cases … little help would have arrived to rescue me outside the airport anyhow … while the right decision ….and method of turn-back …if appropriate… is clearly dependent on aircraft, loading. Altitude, etc etc etc …. I have turned back many times …. enough that I have lost count …surely more than a dozen times …. andcwalked away from each incident unharmed … though twice …not wanting to add additional drag … I landed gear up and pretty well totalled the birds … from the beginning of learning to fly … I never bought the …never turn back … or the …no steep truns in landing pattern… and decided that competence and practice and understanding flight dynamics trumped daft simple minded rules … want to end turnbuckle accidents ? … require aerobatics training as part of every private pilot certification … that simple …
There are pros and cons of executing a turnback maneuver and many pilots have strong feelings on which side of the line they fall. Many of the decisions on which side of the line they reside are based on incorrect information presented to the pilot community by the pundits. The Pilot community always asks the question: “How much altitude over the runway do I need for a successful turnback maneuver. If you continue to ask this question you will never arrive at the correct answer. As both an Aerodynamicist and a CFI for many decades, the key to a potentially successful turnback maneuver is about four key parameters. They are (a) Glide angle, (b) Climb angle, (c) Height above the runway, and (d) Distance from the departure end of the runway (DER). All these four parameters converge on what is required for a potentially successful turnback maneuver, i.e., the Required Minimum Runway Length (RMRL).
To understand why this is the correct answer, one needs to put the cart before the horse. What I mean is that we need to fly the turnback maneuver in reverse. The first question that we should ask is: “If the turnback maneuver is initiated at some distance D from the departure end of the runway (DER), how much altitude will be lost in gliding back to the runway. We define this altitude loss as the EAL (expected altitude loss). The answer to this question depends on the geometry of the turnback maneuver being flown. When discussing this maneuver, many CFI’s and Pilots focus on the teardrop geometry for the turnback maneuver. However, no matter what geometry is flown, this phase of the turnback maneuver is all about steady gliding flight. It involves both gliding turns and wings level glides. The Aerodynamics of gliding turns and wings level glides is well established and can be found in the Pilot’s Handbook of Aeronautical Knowledge (8083-25B). One can then make a plot of EAL versus distance from the DER. The second question that we ask is the following: If the aircraft was climbing out at a specified climb angle, what would be the required height over the DER that would allow the aircraft to reach an altitude equal to the EAL at the distance D from the DER? This phase of flight is all about steady climbing flight. One can then plot the required height over the DER as a function of distance from the DER.The final question one asks is: For a particular takeoff and departure profile used by the Pilot, how much runway would be required for the aircraft to reach this altitude over the DER?. The answer to these 3 questions allows the Pilot to generate a simple plot of the Required Minimum Runway Length (RMRL) versus distance from the DER. This chart can be viewed before takeoff to determine when “never to attempt a turnback maneuver”. The importance of this chart is that for the given runway length at the airport, it shows what ranges of distances from the DER a potentially successful turnback maneuver can be achieved. In addition, if the Pilot has decided there was enough runway for a potentially successful turnback maneuver, there is still a final go/no-go decision while climbing out, since if the aircraft does not have at least the required altitude over the DER, the Pilot can choose not to execute a turnback maneuver. So in reality, it’s all about runway length.
So why are some aircraft able to execute a successful turnback maneuver and others not? To answer the question one must have a level playing field, in that all aircraft are flown in the same manner. Consider the Schiff rule-of-thumb for when to execute a turnback maneuver. The turnback is not executed until reaching a specified altitude. But here’s the problem. Each different type of aircraft in the experiment will reach that specified altitude at a different distance from the DER. What is required for a valid experiment is that each aircraft initiate the turnback from the same altitude and the same distance from the DER. The Aerodynamics of gliding flight tells us how to fly the maneuver to minimize the altitude loss during the turnback. In a wings level glide, the key parameter is the requirement that the angle-of-attack should correspond to the maximum L/D ratio, which is independent of altitude and weight. So in the wings-level glide segment, to achieve the correct maximum L/D, the best-glide speed in the POH must be corrected for any reduction in gross weight. Now all aircraft are on a level playing field regarding the wings-level glide. It is in the Aerodynamics of the gliding turns that the adage “The Devil is in the Details” raises its ugly head. Here one finds four variables that control the altitude loss per degree of turn. These are (1) Wing loading, W/S, (2) Air density, (3) Bank angle, and (4) Angle-of-attack. Items (3) and (4) are controlled by the Pilot. If you want to minimize the altitude loss per degree of turn, you need to fly between 45 and 46 degrees angle of bank (depends on the L/D flown in the turn), and fly an angle-of-attack that maximizes the quantity CL*(L/D). Here CL is the lift coefficient in the turn and L/D is the lift to drag ratio in the turn. This product will always maximize as we approach the stall angle of attack. Now it becomes clear that each aircraft must be flown using a 45-degree bank in the initial turn with a speed that is 5-10% (i.e. a margin of safety) above the accelerated stall speed for the given aircraft weight and bank angle used in the initial turn. Regarding the air density, if all aircraft are being flight tested at the same field elevation, the playing field is level. If this is not the case, the altitude loss per degree of turn should be corrected to sea level density so the playing field is level.
Last year, when I retired from SpaceX, I wrote a White paper on the Turnback Maneuver. One can find it on the EAA website or just Google it on the Internet. The title of the paper is “Single-Engine Failure after Takeoff: The Anatomy of a Turnback Maneuver”. This paper compares the aerodynamic model of the teardrop turnback maneuver with the Schiff rule of thumb (ROT) for when to execute a turnback. It shows why the Schiff ROT is not very good in predicting when to turn back since: (1) It tosses out any information on the wings level gliding portion of the turnback maneuver, and (2) It tosses out information on the scaling effect of aircraft weight and density altitude on the altitude loss in gliding turns. It also discusses the third segment (realignment segment), wind effects on the turnback maneuver, and some of the gotchas in executing the turnback maneuver.
There are pros and cons of executing a turnback maneuver and many pilots have strong feelings on which side of the line they fall. Many of the decisions on which side of the line they reside are based on incorrect information presented to the pilot community by the pundits. The Pilot community always asks the question: “How much altitude over the runway do I need for a successful turnback maneuver?”. If you continue to ask this question you will never arrive at the correct answer. As both an Aerodynamicist and a CFI for many decades, the key to a potentially successful turnback maneuver is about four key parameters. They are (a) Glide angle, (b) Climb angle, (c) Height above the runway, and (d) Distance from the departure end of the runway (DER). All these four parameters converge on what is required for a potentially successful turnback maneuver, i.e., the Required Minimum Runway Length (RMRL).
To understand why this is the correct answer, one needs to put the cart before the horse. What I mean is that we need to fly the turnback maneuver in reverse. The first question that we should ask is: “If the turnback maneuver is initiated at some distance D from the departure end of the runway (DER), how much altitude will be lost in gliding back to the runway. We define this altitude loss as the EAL (expected altitude loss). The answer to this question depends on the geometry of the turnback maneuver being flown. When discussing this maneuver, many CFI’s and Pilots focus on the teardrop geometry for the turnback maneuver. However, no matter what geometry is flown, this phase of the turnback maneuver is all about steady gliding flight. It involves both gliding turns and wings level glides. The Aerodynamics of gliding turns and wings level glides is well established and can be found in the Pilot’s Handbook of Aeronautical Knowledge (8083-25B). One can then make a plot of EAL versus distance from the DER. The second question that we ask is the following: If the aircraft was climbing out at a specified climb angle, what would be the required height over the DER that would allow the aircraft to reach an altitude equal to the EAL at the distance D from the DER? This phase of flight is all about steady climbing flight. One can then plot the required height over the DER as a function of distance from the DER. The final question one asks is: For a particular takeoff and departure profile used by the Pilot, how much runway would be required for the aircraft to reach this altitude over the DER?. The answer to these 3 questions allows the Pilot to generate a simple plot of the Required Minimum Runway Length (RMRL) versus distance from the DER. This chart can be viewed before takeoff to determine when “never to attempt a turnback maneuver”. The importance of this chart is that for the given runway length at the airport, it shows what ranges of distances from the DER a potentially successful turnback maneuver can be achieved. In addition, if the Pilot has decided there was enough runway for a potentially successful turnback maneuver, there is still a final go/no-go decision while climbing out, since if the aircraft does not have at least the required altitude over the DER, the Pilot can choose not to execute a turnback maneuver. So in reality, it’s all about runway length.
So why are some aircraft able to execute a successful turnback maneuver and others not? To answer the question one must have a level playing field, in that all aircraft are flown in the same manner. Consider the Schiff rule-of-thumb for when to execute a turnback maneuver. The turnback is not executed until reaching a specified altitude. But here’s the problem. Each different type of aircraft in the experiment will reach that specified altitude at a different distance from the DER. What is required for a valid experiment is that each aircraft initiate the turnback from the same altitude and the same distance from the DER.
The Aerodynamics of gliding flight tells us how to fly the maneuver to minimize the altitude loss during the turnback. In a wings level glide, the key parameter is the requirement that the angle-of-attack should correspond to the maximum L/D ratio, which is independent of altitude and weight. So in the wings-level glide segment, to achieve the correct maximum L/D, the best-glide speed in the POH must be corrected for any reduction in gross weight. Now all aircraft are on a level playing field regarding the wings-level glide. It is in the Aerodynamics of the gliding turns that the adage “The Devil is in the Details” raises its ugly head. Here one finds four variables that control the altitude loss per degree of turn. These are (1) Wing loading, W/S, (2) Air density, (3) Bank angle, and (4) Angle-of-attack. Items (3) and (4) are controlled by the Pilot. If you want to minimize the altitude loss per degree of turn, you need to fly between 45 and 46 degrees angle of bank (depends on the L/D flown in the turn), and fly an angle-of-attack that maximizes the quantity CL*(L/D). Here CL is the lift coefficient in the turn and L/D is the lift to drag ratio in the turn. This product will always maximize as we approach the stall angle of attack. Now it becomes clear that each aircraft must be flown using a 45-degree bank in the initial turn with a speed that is 5-10% (i.e. a margin of safety) above the accelerated stall speed for the given aircraft weight and bank angle used in the initial turn. Regarding the air density, if all aircraft are being flight tested at the same field elevation, the playing field is level. If this is not the case, the altitude loss per degree of turn should be corrected to sea level density so the playing field is level for all the aircraft.
Last year, when I retired from SpaceX, I wrote a White paper on the Turnback Maneuver. One can find it on the EAA website or just Google it on the Internet. The title of the paper is “Single-Engine Failure after Takeoff: The Anatomy of a Turnback Maneuver”. This paper compares the aerodynamic model of the teardrop turnback maneuver with the Schiff rule of thumb (ROT) for when to execute a turnback. It shows why the Schiff ROT is not very good in predicting when to turn back since: (1) It tosses out any information on the wings level gliding portion of the turnback maneuver, and (2) It tosses out information on the scaling effect of aircraft weight and density altitude on the altitude loss in gliding turns. It also discusses the third segment (realignment segment), wind effects on the turnback maneuver, and some of the gotchas in executing the turnback maneuver.
Les Glatt
What about the effects of wind speed and direction ?
Hi Dave,
The effect of the wind speed and direction is incorporated in the aerodynamic and is completely analytic.
In the original paper I wanted to provide the Pilot community with the results for no wind, since in terms of getting back to the runway, it would require the longest runway. However, I have put together a PowerPoint presentation showing the effect of the wind speed and direction on the turnback maneuver. If you can provide me with your email I would be happy to email it to you.
I admit that I am not an Aerodynamicist and do not disagree with the +1000 words shared by Les Glatt. It is important to recognize that the vast majority of pilots react to emergency situations instinctively. For this reason, after power loss on takeoff, I choose to lower the nose to preserve airspeed, to land into the wind, and to not come back to the airfield.
Hi Peter,
You make a good observation.
That is why any thought of performing a turnback maneuver will require proper training.
I have been interacting with the FAA over the last two years on developing a standardized turnback maneuver training program for those Pilots interested in the training required for executing a turnback. This training should include at a minimum, (a) Basic aerodynamics of the turnback maneuver, (b) Stick and rudder skills in performing the turnback maneuver, and (3) ADM and risk reduction in performing the maneuver.
The fact that the GAJSC has put together a so-called team of experts from the EAA, flight training community, academia, and industry, is a good first start. I should point out that (a), (b) and (c) are all equally important in preparing for a potentially successful turnback maneuver. Without a standardized training program, the outcome will be an accumulation of body bags at the departure end of the runway.
Les
My problem with what you described is that the training has to include the actual turn back which requires a deliberate instructor initiated power loss ( ie throttle to idle) and then the actual steep turn back to the runway.
I see this as the GA equivalent of actual V1 cuts in transport category airplanes. This practice was stopped after it became that way more airplanes became smoking holes next to the runway after training V1 cuts over
Dave,
The FAA will have to approve the standardized training program first. The issue you discussed above will need to be hashed out between the FAA and the Stakeholders. At this time, this is no training syllabus developed yet. The discussions have just started.
Les