Aircraft Engine Failure – Why aircraft engines fail and what to do

As a pilot, it’s crucial you know how to handle aircraft engine failure. This involves knowing and understanding how your engine works, employing consciousness and skill, as well as keeping stress levels to a minimum while handling an emergency.

Introduction

The philosophy with this phase of training is to give the pilot enough knowledge and skill about potential problems that may occur during their first solo, so the instructor feels like he’s done his duty. It doesn’t make any sense to send a pilot solo before they’re fully capable of handling emergency procedures from a practical point of view, unless it’s realized that the possibility of an emergency occurring during a first solo is very remote.

So, even though the likelihood of an engine failure occurring during first solo is very unlikely, it’s still wise to apply the precautionary principle and invest a bit of time and money in this exercise – especially since the principles learned in the following exercises will stand you in good stead later in your training.

Contents hide

1 Introduction

2 Engine failure1

3 What an engine needs to start

4 Poor Ignition

5 Airflow

6 Fuel exhaustion /starvation

7 Conclusion

aircraft engine failure — One of the most likely causes of total or partial loss of power is fuel starvation or exhaustion.

Engine failure¹

Knowing how engines work will enable a pilot to prevent engine failures, or identify the cause quickly, and prevention is far better than cure, which in this case is a forced landing. It’s easy to get so carried away learning how to handle an engine failure that we don’t spend enough time getting to know engine parts and how things work, and then end up causing problems for ourselves.

The priority should always be prevention first, rather than how to deal with a failure that we have unwittingly caused through our own ignorance or lack of skill. The overall aim is to enable a safe landing following a loss of power, but this is also the best time to explain how engines work so pilots learn how they should be treated.

An engine failure/loss of power/rough running can happen at any point in the circuit, so it’s best to practice at a few different places so the pilot develops a broad appreciation of how to land safely from any point. It’s also wise to point out that engines don’t normally quit without warning, and may just start running a little rough, making a funny noise, vibrating a bit, or ‘acting funny’.

An inexperienced, poorly trained pilot will choose to ignore things they don’t understand, so it’s prudent to cover a range of possible scenarios rather than just sudden and complete loss of power, or they’re likely to carry on regardless, rather than taking action to rectify the fault or land safely if the usual remedies don’t work.

The National Transportation Safety Board outlines the details of an aircraft engine failure HERE⁷, which killed 10 people, after pilots failed to follow emergency procedures and there appeared to be a general lack of understanding of how the engine works.

“In any emergency situation the first and overriding priority of the pilot is to fly the aeroplane. Then if time permits the next two priorities can be attended to, navigate and communicate – in that order.”
aviation.govt.nz¹

What an engine needs to start

This training builds on the foundation already laid while teaching how to start an engine. Essentially, there are only four things an engine needs to start/run, – fuel, air, compression, and ignition.

Of those four, only three are likely to be deficient since if the engine’s already been running, it has demonstrated compression. That narrows the cause down to fuel starvation/exhaustion, a lack of airflow, or poor ignition. If a piston lets go or a valve gets stuck causing a loss of compression, you’ll know about it. The sound and vibration will be pretty obvious compared to an engine running intermittently because it’s short of fuel, air, or spark.

If something catastrophic like that happens, whether you have an emergency autoland system or not, the best course of action will be to reduce power and land as soon as practicable while focusing on that and nothing else. Running through trouble checks and checking all flight controls could be a distraction you can’t afford, so it’s always best to assess the bigger picture first, as part of your emergency plan, before mucking around with the detail.

Poor Ignition

Fouled plugs or a failed magneto² may cause poor ignition, but neither are likely, and the only thing a pilot can do is to check the magneto switch is on and cycle it to isolate each one. If the timing of one magneto has shifted, it will cause rough running, and isolating each mag will allow the engine to run smoother on the other. Another possibility is that the plugs have become fouled, but if the engine checked out okay during pre-flight, this isn’t likely either.

If the mixture is too rich and the engine’s run at low power, that can cause plug fouling and induction icing. Avoiding long low power descents, and using carby heat if you have to use low power should prevent any problems.

Airflow

A lack of airflow can be due to a blockage in the induction system or the throttle butterfly closing. Sometimes, the throttle cable breaks or gets disconnected from the butterfly linkage, but that’s easy to identify because moving the throttle won’t have any effect. Once that’s identified, landing is the only option. If a bird blocks the induction system, or a scat inlet hose comes lose and folds back on itself, the only thing a pilot can do in the air that might work is selecting carby heat or alternate air.

Carby icing can also restrict airflow,³ which is why carby heat/alternate air is one of the first things to try when the engine starts running roughly. Note that both access heated and unfiltered air at the same time, so any blockage or restriction may be avoided by doing this too.

Fuel exhaustion /starvation

The most likely cause of total and complete loss of power is fuel exhaustion/starvation.⁴

Fuel exhaustion means running the fuel tanks dry, and fuel starvation⁵ is being unable to draw fuel from the tanks for some reason. The most likely cause of fuel starvation is running dry on one tank, so switching tanks is the simple fix. Another cause could be that the tank air vents are blocked or the engine driven fuel pump has failed.

If the vents are blocked, fuel flow would be restricted like trying to suck water out of a bottle that has no other opening for air to enter. If the tank cap is removed and an audible sucking sound is heard shortly after landing, the vent is blocked. If the cap is removed an hour or so after landing, the pressure would have equalized by then, so if the engine does run a little rough and all other possibilities have been excluded, check the caps soon after landing.

Another possible cause of fuel exhaustion could be that the tank cap hasn’t been put on straight, or the cap seal is damaged or even missing, causing fuel to be sucked out during flight. Unless you’re flying a low wing aircraft and can see the tank caps during flight, the only way you’d suspect an in-flight fuel emergency happening is if a fuel gauge is observed to be running low quicker than planned. There’s no need to worry about it too much though, just remember to have a good look at the seal and make sure the cap is seated correctly during the pre-flight inspection and assume the fuel gauge is accurate rather than assuming the best.

“There’s no better preparation for an emergency landing than recent practice. Make it a part of your everyday flying routine to choose an appropriate location, simulate an engine failure and practise going through the recommended procedures to be in the best position so as to land you and your aircraft safely on the ground.”
outnback.casa.gov.au/episode-8/emergency-procedures⁶

Conclusion

After taking the time to explain why engines might play up, and how to avoid that happening most of the time, it’s worth mentioning that the best laid plans of mice and men occasionally don’t work as they should. That’s why both CONSCIOUSNESS & SKILL are both necessary; the first to prevent shit happening, and the second to ensure you can deal with it when it inevitably does.

Being able to handle emergencies⁶, including catastrophic engine failure, demands both consciousness and skill, and provides the best insurance policy money can’t buy. While both are important, it should also be noted that there is no need to panic and try to improve either consciousness or skill so fast that you get stressed.

Have an awareness of your emergency equipment/emergency supplies, ensure appropriate emergency planning, and that way, if an emergency occurs, your knowledge and skill, along with safety systems should keep all flight crew and passengers safe. Remember, once you land, you can always call upon emergency responders/emergency services if necessary.

Being able to manage stress is a pilot’s greatest challenge, and avoiding complacency or arrogance is second.