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Decreasing your exposure to aerodynamic risk
5. Engine failure after take-off
Rev.5 — page content was last changed 14 June 2012
Recreational light aircraft engine/propeller failures in flight are not rare and generally are not particularly stressful — if adequate route planning has preceded the flight — except if operating over water or when failure occurs in take-off or go-around modes.
The take-off and late go-around sequences in a very light aircraft are the most critical of all normal flight procedures; all the engine's available performance must be employed during the acceleration and initial climb, leaving no power in reserve. There is no potential energy of excess height or excess speed available so, during take-off, the pilot's options are very limited — even more so in high density altitude conditions.
All recreational light aircraft are low-inertia aircraft — the 'draggy' ones are low-inertia plus low-momentum aircraft — so are detrimentally affected by rough air at low levels.
If complete or partial loss of thrust occurs shortly after lift-off, the best and probably only option, is to promptly establish a safe descent attitude and speed, and land on the remaining airstrip, ground looping if necessary to avoid an obstruction. It is only if total loss of thrust occurs after achieving a 'decision height' that a safer option other than land more or less ahead MAY exist. A possibility of loss of control is introduced any time that total or partial loss of thrust is experienced in the climb or in a turn, the cardinal rule in those situations is to 'fly the aeroplane!'; i.e. maintain control of the situation.
In EFATO situations there is a strong compulsion to direct your thinking towards minimisation of airframe damage — very understandable if the aircraft has taken a long time to build or acquire — but the overriding priority has to be directed towards minimising risk to occupants, even if that means sacrificing part of the airframe.
What's meant by the term EFATO?Once airborne, naturally any engine failure is a failure after take-off even if the aircraft is 100 nm from the take-off point. However, the EFATO term is usually accepted to mean a significant loss of thrust occurring while the aircraft and pilot are still in 'take-off or go-around mode'. For example, haven't yet set course, or raised take-off flap, or haven't yet reached 1000 feet agl if intending to operate above that height, or, if doing circuits have not yet completed the crosswind turn; i.e. a 'thrust deterioration at take-off' that occurs while climbing soon after lift-off or during a go-around when the aircraft has little energy to trade.
This module presumes the reader is familiar with the contents of the earlier 'Don't stall and spin in from a turn' and 'Don't land too fast in an emergency' modules, which are pertinent to this document.
5.1 What happens when the engine or propeller fails in the initial climb?
Pilot and aircraft reaction timesA recreational light aircraft established in the climb attitude at Vy (best rate of climb speed) has an aoa perhaps around 6–8°. At such angles there is significant induced drag so when thrust is lost, for any of a multitude of reasons, the aircraft may rapidly decelerate to stall speed — worse if the airframe also has much parasitic drag. The immediate action required is to convert the potential energy of height to a safer speed. When climbing at Vx (best angle or emergency climb speed) aoa could be around 8–12°, so deceleration following power loss is a greater hazard. Of course recreational light aircraft Pilot Certificate holders are aware of this and take immediate action to lower the nose to a position consistent with their estimate of the approach or glide attitude in pitch. Or do they? Material developed by the late Mike Valentine, the former RA-Aus Operations Manager and prestigious GFA stalwart, is included in this section. Mike conducted considerable research into pilot and aircraft reaction times following cable breaks in winched glider launches and engine failure after take-off in recreational light aircraft. Some research results — which were very similar for both aircraft categories — were published in the June 2004 issue of the RA-Aus journal, and are summarised as follows.
Unloading the wings is a good practice to practiseAs mentioned in the flight envelope section of the 'Don't fly real fast' article a light aircraft can be safely held at sub-Vs speeds for several seconds by unloading the wings so that the aircraft is operating in the reduced-g band between zero g and +1g, but not in negative g. The stall speed between +1g and 0g is still proportional to the square root of the wing loading g ratio, as indicated in Table 4.1.
Note: when the wings are unloaded, ailerons and rudder can be used in ways that would be regarded as excessive at 1g loads. This unloading technique also has value as a stall recovery exercise (at a safe height) for pilots to really comprehend what is going on. It involves unloading the wings to perhaps 0.25g by pushing sufficiently forward on the control column so that you feel very light in the seat but not yet constrained in the harness as you would be if imposing negative g — or if dirt and dust start floating up from the floor. When unloaded — which takes an instant — roll the wings level (holding near zero g of course) using full aileron and whatever rudder is necessary (often quite a lot), and centre the aileron and rudder as soon as the wings are level. As drag at that minimum aoa is much reduced, speed will build more quickly and thus dive recovery is started earlier. With practice, the total height loss by taking such decisive action may be less than in a gentle reaction, and the speed will stay well within the allowable envelope in most recreational light aircraft. There will not be any fuel system problems as long as negative g is not applied. However, if forward pressure is slightly relaxed and the aircraft allowed to return to its normal 1g state while airspeed is below Vs1, the wing will promptly stall.
Planned energy management during the initial climbFollowing engine failure in the climb, the total energy available is the sum of kinetic energy and potential energy of height. As shown above, a lot of that kinetic energy is lost to drag in the 6–8 seconds following loss of power. The potential gravitational energy must be converted to kinetic energy so that the total energy level of the aircraft is maintained, albeit at a lower level than that immediately prior to the power loss.
There may not be enough time available to regain enough speed within the remaining height to have sufficient energy to arrest the rate of sink (i.e. flare) for a normal landing. A heavy or very heavy landing is then almost inevitable. For example, the low-momentum Thrusters and Drifters have thick high-lift wings that give their best climb rate [Vy] at about 50 knots. They probably need about 150 feet to build enough airspeed to enable the aircraft to be flared for a normal landing; obviously, more slippery aircraft need less height.
The solution to this potential problem is planned energy management during the initial climb. Don't use the recommended speed for best rate of climb, use a climb speed perhaps 10–20% higher until at 200–250 feet, then steepen the climb a little to maintain Vy. The loss of initial climb performance won't be particularly significant but the additional speed in hand will make a difference if you lose thrust at a critical height. Of course, you may prefer to maintain the higher speed as a cruise-climb speed, particularly if there is a reasonable headwind or a tendency to overheat.
What about using the best angle of climb speed for initial climb?Vx should not be used in normal operations — it should be regarded as an emergency climb speed. The high pitch attitude, high aoa and low speed provide a very limited safety margin if power is lost. If an airstrip is so marginal that you consider you must use Vx to clear obstructions at the end of the strip — or worse, out-climb rising terrain — then you should not be using that airstrip. If you absolutely have to use Vx for obstacle clearance then lower the nose to a safer climb speed as soon as possible.
Have a mental 'what if?" action planPilots must always be prepared for the possibility that the engine/propeller will lose thrust during the take-off and climb out (or at any other time during flight), and have simple pre-formulated mental action plans for the particular airfield/strip/runway conditions and various failure modes — remembering that, depending on height if the engine fails, there may be little time to do much else but keep your eyes outside the office, select the landing run and fly the aeroplane. One thing though — it is important to close the throttle early enough to avoid the engine suddenly regaining full power at an inopportune time; e.g. just as you are about to flare, thus driving the aircraft into the ground — which has happened on occasion.
If there is any thought that something is not quite right during taxying, run-up or the take-off ground roll, the flight should be abandoned immediately. A surprising number of pilots disregard indications/warnings that something is not as it should be and press on to an inevitably expensive reminder that engine/fuel/propeller problems cannot fix themselves. It'll be okay? Not likely!
On-field landingIf the aircraft is very low when the engine fails the only option is to keep the wings reasonably level, the slip ball centred and land more or less straight ahead. So the minimum action plan would be:
There have been occasions, even at small airfields, where a recreational light aircraft losing power at 200 feet or less had sufficient height to safely turn 60–90° and land on, or parallel with, an intersecting strip. Of course, the pilot in those reported cases has been quite familiar with the aircraft's capabilities and had commenced take-off with little or no runway behind.
Off-field landingIf some height has been gained but there is no possibility of landing on the airfield, then an off-field landing is mandatory. Look for somewhere to put it down but don't immediately fix on the first likely landing site spotted straight ahead of you — there may be a more suitable site closer. However, you have to rapidly assess your height and airspeed (i.e. your energy level), and the turn possibilities available; i.e. can you safely turn through 30° or 45°, perhaps 60°, and still make it to that much better looking site? Will the wind assist or hinder? How much height will be lost in the turn? It has to be a quick decision because at best you have just a few seconds available to plan the approach. If any doubt go for 'into wind' and remember you can't stretch the glide!
Do not choose the site at marginal distance, even if it's perfect. Close by is better because the height in hand can be used for manoeuvring the aircraft into the best approach position. Because you have no power available you must always have an adequate height margin to allow for distractions, misjudgements, additional loss of height in turns, adverse wind shifts, sinking air, turbulence and other unforeseen events — and you can dump excess height quickly using full flap or sideslipping. Remember that the rate of sink whilst sideslipping is high and the slip must be arrested before the flare.
Some major factors affecting the outcome of a forced landing are highlighted in the previous module 'Don't land too fast in an emergency' and it is not my intention to list all factors that might be assessed in the decision making process following EFATO. Suffice to say, it is impossible to assess everything in the few seconds available, hence the need for prior knowledge of the airfield environs, plus a pre-established plan B and intuitive procedures for any situation that may occur before you are established at a safer height.
Apart from being clearly within range the choice of landing site is affected by:
As height increases, the options increase for turning towards and reaching more suitable landing areas, making a short distress call and doing some quick trouble shooting.
It is important to research and develop your own safety plan, including the cockpit and radio drills, so that it is more deeply ingrained and appropriate to your capabilities and the aircraft being flown. Don't just adopt a plan published by someone else. Before moving onto the runway for take-off, do a mental rehearsal of plan B; such rehearsal is a powerful safety aid.
As height achieved before engine failure increases, the options increase for trouble-shooting, turning towards and reaching more suitable landing areas; making a distress call on a selected frequency; properly securing the fuel, ignition and electrical systems; and for an adequate cockpit check prior to touchdown — but all in accordance with the plan.
The next article in this series discusses 'The turn-back: possible or impossible — or just unwise?'.
'Decreasing your exposure to risk' articles
| Introduction and contents | Recent RA-Aus accident history | Don't fly real fast | Don't stall and spin in from a turn |
| Don't land too fast in an emergency | Engine failure after take-off | The turn back: possible or impossible — or just unwise? |
| Wind shear and turbulence |
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