Saturday, 30 September 2017
SINGLE-ENGINE AIRCRAFT ENGINE FAILURE IN FLIGHT
Acknowledgements: Thomas P. Turner, Mastery Flight Training, Inc.
This most commonly results from fuel mismanagement as the result of either fuel starvation (failure to switch tanks in time) or total fuel exhaustion. In other words, a great many engine-related crashes result from pilot-induced engine failures, which are easy to explain. However, there is a need to look at the remaining engine failures that are not the result of fuel starvation or exhaustion.
Surviving an engine failure
This involves meeting three objectives:
1. Maintaining control of the aircraft during the engine-failure in flight
2. Restarting the engine if possible
3. Landing under control at the slowest safe speed
There’s an axiom in flying:
ATTITUDE + POWER + CONFIGURATION = PERFORMANCE
The pitch attitude determines the airspeed the airplane will fly at for a given amount of power and a given airplane configuration (flap position; gear position in retractable gear airplanes; propeller position in propeller aircraft with controllable pitch propellers).
If a given level of PERFORMANCE results from a POWER setting at a given ATTITUDE and CONFIGURATION, then it stands to reason that a given level of PERFORMANCE is the result of ATTITUDE and CONFIGURATION even when the POWER setting is zero. So, if an engine quits, there is a specific ATTITUDE that will result in best glide PERFORMANCE.
You can test this with a simple experiment in flight.
In clear, traffic-free skies at a safe altitude, gradually reduce power to simulate an engine failure from cruise flight:
· As the airplane decelerates, ensure the flaps and landing gear (as applicable) are up.
· When the airplane reaches its published best glide speed, adjust the attitude to maintain that speed in a descent.
· Look at the attitude that results in best glide performance - both by reference to the attitude indicator and by visual reference outside.
· Adjust attitude up and down to vary the indicated airspeed by five knots. Compare the vertical speed which results. Remember the “best” attitude: it is the primary reference for attaining the first objective of surviving an engine failure, maintaining control of the aircraft. At speeds below maximum gross weight, the best glide speed may be slower than published, but the best attitude will be about the same regardless of weight.
· If your aircraft has controllable pitch and/or a featherable propeller, during your descent pull the propeller control fully aft. If you actually feather, do so over an airport in case you can’t get a restart later! Adjust the pitch attitude to remain at best glide speed. Remember this attitude also: this is the primary reference for obtaining maximum engine- out performance in the airplane, that is to say the least rate of descent depending on airplane weight and environmental factors.
Best available performance comes with the wings level in rudder-coordinated flight, so during your exercise:
· Establish best glide speed and note the vertical speed.
· Then begin a standard-rate turn (about 15 degrees of bank at typical glide speed).
· Note the change in vertical speed.
· Increase the bank angle to 30 degrees and note the even greater vertical speed.
· Try a 45-degree bank and note the result.
This exercise shows you the detrimental performance effect of turns in an engine-out scenario, even at the “best” performance airspeed. It will reinforce the need to maintain straight- ahead, wings-level and coordinated flight in order to obtain best glide performance in the event of an engine failure, with turns only as altitude permits to get to a suitable landing site. This is a great exercise to cover in your next Flight Review, flown with an instructor. A Flight Review is supposed to be instruction, not a check-ride, and doesn’t this sound like an interesting, fun and important thing to learn?
Now that you have established control, the next objective is to restart the engine if possible. An engine needs three things to develop power: fuel, air, and a source of ignition. But is there anything else you can do to affect the fuel flow to an engine?
· Ensure the fuel selector is ON!
There are documented cases of pilots and passengers who have inadvertently moved fuel selectors to the OFF position by bumping them or pulling a flight bag or purse strap across the selector in flight.
· Turn the auxiliary fuel pump or boost pump ON (if one is installed)
The proper use of auxiliary or boost pumps varies from one airplane type to the next. Even among different versions of the same make and model of airplane the design and use can differ - what works in a Piper doesn’t necessarily work in a Cessna, so read your POH, study its Limitations, the Emergency Procedures and Normal Procedures checklists, and the Systems Description section, and review the corresponding information in the POH Supplement for any engine or fuel system modifications to that airframe. Seek out expert instruction in your airplane type and for its modifications, through the airplane owners’ group that supports the model you fly or instructors or programs you’ll find advertising in type club communications.
· How about air flow? Replacement sources of induction air flow range from carburettor heat, to automatic induction air, to manually activated air filter bypass systems. Again, review the POH and any Supplements, and seek out the advice of experts in the type.
· Ignition, too, may be confirmed or altered by the pilot - confirming the ignition switch is ON (or BOTH, in magneto-driven systems that apply to most piston airplanes), and individually selecting magneto positions as applicable to see if smooth, albeit less-than-optimal, power may result by shutting off one of the redundant systems.
The final objective to surviving an engine failure is to “land like a WUSS!”:
Wings level, Under control, at the Slowest safe Speed.
Common engine-out crash scenarios after the pilot has maintained control to near a landing zone include:
· A stall resulting from trying to “stretch” the glide to a landing spot, after selecting a runway or field too far from the aircraft, or by not manoeuvring the airplane correctly to arrive at the selected zone.
· Otherwise getting too slow on the approach, entering a high sink rate with descent into obstacles.
· Failing to maintain wings-level flight through the touchdown and for as long as possible during the roll-out or impact slide, resulting in impact forces injurious or fatal to the airplane’s occupants.
Common to off-airport landings and runway excursions or overruns:
· Serious head injuries and head-trauma deaths from otherwise survivable impacts, often with surprisingly little damage to the airframe, when the pilot and other front-seat occupants do not have or choose not to use shoulder harnesses. Shoulder harnesses are not required to be installed in most general aviation airplanes, but if they are they must be worn by all airplane occupants at least for ground movement, take-off and landing. And since it would be unlikely the pilot or passengers would have time to fasten a shoulder harness after an engine failure but before impact, there really is no reason to avoid wearing them in all phases of flight. And if you have a say in the airplane’s installed equipment, put shoulder harnesses at the very top of your updates list.