The impossible turn

by | 2021-12-04
Single engine aircraft hard landing

Good risk management requires good planing

For a while now, a recurrent subject emerges on various discussion platforms, social media and publications: « the impossible turn ». This being a turn back to the runway maneuver following a total denial of service from the engine(s). The best part is where we all imagine being capable of executing the said maneuver safely.

Frankly, I get an uneasy feeling watching the slew of Youtube stars joyously displaying their abilities in accomplishing the maneuver while promoting the ease of execution: « Hey, just watch how easy it is ! ».

It is worth noting that this emergency procedure, and it is, is not officially thaught or trained in Canada and probably nowhere else in the world. Indeed, one must recognize, that this emergency is not statistically the biggest cause of accidents such as inadvertently flying in IMC while on a VFR flight plan. 

The debate if it existed resides in the fact that everyone imagines being absolutely capable in succeeding the maneuver without any issue.

Reality is located somewhere between total failure (ie crater digging) and careful preparation for this « eventual » condition.

NTSB video: C-172 during a total power loss and the failed return to the runway maneuver. No casualties. Please note the aircraft attitude.


While on ab initio training, the regulator requires the pilot to demonstrate an engine failure (single engine aircraft) on departure. The only option to land is straight ahead with the reasonable 30˚ left/right window for a shallow turn.

No requirements exist for a total power loss on multi engined aircraft !

Training cost being what they are and the fact of training a complex, high risk and rarely experienced maneuver does not thrill many, including the regulators. For this very reason since the dawn of time, it is an « accepted » fact that during pre-solo flight training, it is taught that the « 180 » return must not be entertained prior reaching 1000 feet AGL.

Thus, civil liabilities and legal requirements are sufficiently covered.

With a minimum of good airmanship perspective we know that there exists nowadays quite a few aircraft being capable while properly being flown to execute the return maneuver below the symbolic 1000 feet AGL and without incurring absurd limits crossing.

Little judgement is required to evaluate the difference in performance between a Piper J3 and a Beechcraft Bonanza for example. Clearly, the global 1000 feet AGL coverage protection is rather subject for discussion.

Engine constraints

Mechanically speaking, even when completing the pre take-off procedure by the book, one requires that all engine(s) develop the maximum certified power right at the start. It is not during the take-off run on a marginal conditions runway that one must ask oneself questions on how smooth and easy ones engine operation may have been in the previous days. Never mind philosophizing on certain maintenance « differed » issues.

Personally, I consider engines like quasi living units with sensitivities that deserve white glove treatment. Yes, it is said that I feverishly pamper them. Alas, it is publicly embarrassing, however totally assumed.

180 degrees? No way!

First, supposing sufficient altitude and without getting into elaborate geometrics, an engine failure on departure, calm wind, followed by a 180˚ turn will get the aircraft somewhere left or right of the reciprocal runway centre line. Of course if there exists an acceptable surface at this moment, one has just won the lottery. I have never bought that ticket…

During many edifying hangar talks, most of us agree that more than 180˚ are required for the return. Turning may require something more in the order of 270˚.

A simple turn, we all know this, will produce an increase in load factor and the consequent increase in stall speed depending on the amount of bank. For example:

  • 30˚: the load factor increases by 18% and the Vso increases by 8%
  • 45˚: 40% and 18%
  • 60˚: 100% and 40%

The 60˚ bank turn, think about it, is bewildering, particularly at low altitude and low airspeed. If your aircraft stalls 65 KIAS, you are now flying an aircraft that will stall at 91 KIAS. A spin doctor is standing by to take your call ! Even a 45˚ bank turn at 500 feet AGL resembles like a form of incontinent dementia.

During the turn back, an understandable sense of pressured emergency exists mucking up the decision process. All the while a vital airspeed increase must be processed by pushing on the nose. The sink rate increases to an abnormal measure. At 3000 feet, frankly who cares? No one can feel the effect. At 800 feet, the perspective is way different. Solid coordinated flying will be required and adding the adequate memory items execution to hopefully restart or secure the engine will not make that short lived experience any easier.

Finally, the conventionally accepted 1000 feet AGL does not appear so conservative after all.

Cockpit resource management  

Since the early 80’s, the industry has acquired vast amount of knowledge on human factors. One of them is that pilots are not the best for self evaluation of their own flying skills.

This does not mean by any sense that pilots are incapable to execute a complex maneuver. It merely means limited evaluation capacity in relation to recency.

What is more simple than executing a « 180 » and land? What is more simple than digging a crater short of a runway threshold.

The startling factor

During flight testing in order to construct accelerate/stop distances, the V1 (go / no go) decision is established adding 2 seconds for human reaction time. This « surprise factor » is well documented. It has been enhanced by the well publicized « Sully factor » (Captain Chesly Sullenberger, US1549).

No measurement exists from any manufacturer for total power loss on departure. Never the startling factor at such a critical time. Worst no authority required demonstration or training. Over at the major carriers, two reasons exist for this absence: firstly, the very high reliability of turbojet engines. Secondly and for not so noble reasons, is the general lack of financial resources allocated to flight crew advanced training. Training cost does not produce financial dividends.

This last element of course applies to any aircraft owner. Who wants to hire a flight instructor to go out and practice a maneuver that is not even required for the concerned licence?

All aircraft are not created equal!

A DA-40 will not glide in the same fashion as an Antonov 2. A Metroliner will not behave as joyously as an A-320. Wings are of the essence here and of course drag.

Many single engine aircraft manufacturers will produce a glide ratio graph. This is seldom the case for the multi engine world.

Multiple factors

Other than the standard flight mechanics involved in a turn as such, many factors all intertwined, will influence the success of a total power loss and return to runway maneuver, if required.

  • Decision altitude: Knowing this altitude in order to allow for a safe return with some margin is a key factor. Flying near limits is never a good thing.
  • Best glide attitude: It is imperative to proceed from a nose up to a nose down attitude quickly. Speed will decay rapidly, once nose down, final adjustment to the glide attitude will be easier.
  • Runway length: A short runway could mean an eventual high and unstable approach if an optimized climb was accomplished. For the same runway, on a standard climb out, it may not be possible to make the threshold.
  • Wind conditions: a strong headwind will reverse its benefit by getting you back to the runway perhaps too quickly and the increase in groundspeed and the energy required to stop before the « far end ». Further, the loss of flight control effectiveness at low speed may cause serious ground control issues.
  • Crosswind condition: Evidently to avoid flying astray, the turn should be accomplished into the wind. Also, it is worth mentioning the effect of the wind veering at low level during the climb. Crosswinds most of the time equates to turbulence, affecting an approach already in rock and roll mode.
  • Air density: Take-off performance will be largely affected.
  • Aircraft weight: While gliding, a heavier aircraft will cover more ground distance than the lighter one. Time wise, it will however, glide a little less longer.
  • Coordinated flying: Slip or slides produce drag. When reaching for a « distant » threshold drag is to be obviously avoided yet it may become quite handy should you have the luxury of extra margins. Hard control inputs create drag, remain smooth all the time.
  • Active components: Flaps, retractable landing gear, windmilling (or feathered) propeller(s) bring their own very measurable amount of drag control.
  • Speed, speed, speed: Gliding speed is essential, increasing it during the turn is vital.
  • Immediate traffic: Picture yourself superbly turning back with good margins only to wind up head on with the next traffic departing behind you. The shot has to be called ahead of time. This is where an acute sense of situational awareness becomes capital. Viewing the traffic picture and remembering it will help trigger an efficient radio call (Communication) in uncontrolled airspace. Within a control zone, generally, another runway may be available as an option. The controller will bring vital support from the fact that he or she observes traffic movement from a privileged vantage point.

The capacity, within that short amount of time, to execute the power failure procedure proficiently, needless to say, must be practised. One is dreaming in « Technicolor » if one expects to fly coordinated, make a coherent radio call and complete a cockpit procedure without prior and recurrent practice.

Practising at altitude with an instructor will provide approximate yet excellent idea on the specific aircraft « decision altitude ». This in itself will help in building confidence in procedure execution.

Before take-off briefing

A well structured briefing with the total loss of power consideration is the basis of success.

Personally, having practised at safe altitude or in a simulator, I have acquired the knowledge that a high performance glider will take 200 feet to return, the power loss coming from a cable brake during the take-off tow. A PA-20: 800 feet, a PA-30: 1100 feet (windmilling props and landing gear extended when runway is assured), an A-320: 3600 feet and an A-330: 2600 feet, yes, wings are great!

Of course there comes a time when all good things come with a warning. The previous information is presented as nothing more than a qualitative indication. By no means do they pretend to substitute the absolute necessity to follow precisely the aircraft AFM. The adherence to procedures required by the manufacturer and the regulatory instances are a pre requisite. The total power loss return to the runway maneuver is perilous, involving a largely unstable condition at low altitude with a short amount of time available. It demands superior abilities that can be acquired with practice.  

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