Aero-engine is the power device of aircraft, which provides flight thrust and is called the heart of the aircraft.
During service, the components are subjected to complex cyclic loads due to constant startup, shutdown, and various flight requirements.
Although the reliability of the engine is increasing with the improvement of manufacturing technology and maintenance level, the air stop still happens occasionally.
But sometimes engine failure is hard to see on the surface, which makes flight work difficult.
Let’s take a look at how to determine whether the engine failure.
Engine fire can occur at any stage of flight, including air and ground.
Engine fire usually occurs in the short cabin, but outside the engine core and airway, so it is called external fire.
It is usually caused by the following reasons: 1. Leakage.
Flammable liquid meets high temperature and engine parts ignite.
Flammable liquid includes: fuel oil (automatic ignition point 230¡æ);
Lubricating oil (automatic ignition point 260¡æ;
Hydraulic fluid (automatic ignition point 450¡æ).
2. Pipe cracking (e.g., engine rotating parts cracking).
3. Combustion chamber cracking (will lead to tongue flame).
Such faults are easily identified due to special detection loops and ringtone warnings.
But unfortunately, the crew won’t be able to see, hear or smell an engine fire.
This leaves pilots with no other reference points and sometimes difficult to make the best decisions.
Sometimes when the throttle is in a slow position, the fire alarm will disappear.
That means it could have been caused by hot gas blowing on the fire detection loop.
For example, heat causes pipe cracking.
When the engine works at low power, the air intake decreases and the fire alarm signal disappears.
That means the engine didn’t catch fire.
Engine fire detection is based on temperature sensors (loops) placed in sensitive areas of the engine and hanger.
As shown in figure 2.
Different types of engines have different characteristics and are placed in different positions.
A single – sided loop failure can also cause a fire alarm.
This often happens to engines that have just finished maintenance.
Accurate judgment of fire warning instructions can avoid unnecessary engine shutdown in the air.
Generally, if it is determined that there is a fire alarm, it is necessary to shut down the engine and pull out the fire extinguishing handle in the first time, which can quickly cut off the oil supply, air intake and ignition of the engine.
Whenever there is a fire, it is most important to control the condition of the aircraft.
It turned out that even if a fire broke out immediately after leaving the ground, there would have been enough time for the aircraft to climb to a safe altitude (the company’s policy is 400 feet or more).
The destruction of fire will be enhanced by the loss of time. A long time of combustion may lead to the increase of the time to extinguish the fire, or even the fire can not be extinguished (such as the fire extinguisher circuit burned out), the consequences are devastating.
Putting out a fire is a race against time, and it needs to be put out as quickly as possible while keeping flight conditions under control.
Do not attempt to restart the engine after extinguishing the fire, as this may lead to reignition.
This is due to a backlog of fuel inside the engine, which is ejected from the tail nozzle when the car is started or shut down and then ignited.
The rear end of the engine will form a ten – meter long flame, the scene is very spectacular.
Because it occurs in the part of the design temperature is very high (1000-1200¡æ), so it has little impact on the engine.
But it can have effects on the aircraft itself (such as damaging flaps).
Because the area of occurrence is located inside the airway, it is usually called an internal fire alarm.
This special situation cannot be expressed in the simulator training, so the crew may be less exposed.
The tailpipe fire is only activated during ground engine start and fire shutdown.
Since there was no warning from the cockpit, the determination of this particular situation depends on reports from the flight attendant, flight attendant or ATC.
They may report an engine fire due to the large amount of flame associated with the tailpipe fire.
If there is no fire alarm in the cockpit, do not follow the fire alarm checklist.
Moreover, the fire extinguishing agent injection area is located between the engine cowling and the core, and performing the fire checklist and releasing the fire extinguisher has no effect on this fault.
As shown in figure 3.
Many procedures in the liner fire checklist do not exist in other engine failure checklist, accurate judgment will help the engine cold switch fire as soon as possible.
When the compressor speed is fixed, the air flow of the compressor decreases for some reason, which leads to the decrease of the absolute velocity at the inlet of the working impeller in the direction of the engine axis, and the air flow is separated at the back of the blade.
This phenomenon on the back of the leaf is called stalling.
If there are too many stall blades, it will cause compressor surge.
Generally speaking, engine surge is referred to as compressor surge.
Surge is a phenomenon of low frequency and high amplitude oscillation of air flow along the axis of compressor.
The fundamental cause of compressor surge is air flow separation.
This separation is caused by the compressor operating state deviating from the designed working state seriously.
The following conditions can cause engine surge: 1. Reduced engine performance (e.g., compressor blade cracking or high wear) 2.
Inhalation of foreign matter (e.g. birds) or ice 3. Cause system failure 4. Engine control failure (fuel control or surge protection).
If a compressor surge occurs at high-horsepower takeoff power, the pounding we hear during simulator training is not enough to justify the sound.
The crew, who had experienced this before, reported that it sounded like a shot had been fired next to him.
This is easy to cause the crew panic, mistaken for a tire explosion or bomb explosion.
Such incidents on flights show that crews are prone to misjudge engine surge, leading to interrupted takeoff above V1, overshooting the runway and damaging the aircraft, injuring or even killing passengers.
In fact, it was just a loud bang.
According to different compressor faults, the engine surge can be divided into the following situations: 1. Single self-recovery.
The crew may hear a loud noise or two and the engine parameters fluctuate rapidly.
Usually within a fraction of a second, the indicator will return to normal, it is difficult to tell by looking at the indicator.
2. It can recover itself several times.
Depending on the cause and conditions, the surge will occur several times, each two to three seconds apart, and then indicate a return to normal.
During this period, EGT increases.
3. Surge stop after unit disposal.
The crew will observe several successive fluctuations in engine parameters.
The throttle lever retracted and the parameter indicated matches the throttle position.
Only if the throttle is repushed forward to high power, surge occurs again.
In this case, if the unit is not dealt with in time, surge will continue until the engine failure.
4. The unit cannot be restored after treatment.
There will be a single burst.
With a loud noise, the engine slows to zero power, as if it were not pumping oil.
This usually means serious engine damage.
After the throttle is retracted, the EGT will rise at a speed of 15¡æ/ second for about 8 seconds, and then fall back.
N1, N2 indication and throttle position consistent;
Fuel flow drops to 25% of pre-surge levels within 2 seconds and continues to drop to 10% over the next 6 seconds.
A single recoverable surge is unlikely to cause engine damage.
Multiple sustained surges can damage compressor blades.
This results in reduced compressor efficiency and increased volume of gas entering the combustion chamber, which will lead to excess fuel supply.
The combustor cooling zone cannot ensure that the air is sufficiently cooled before reaching the turbine, resulting in EGT exceeding the limit and turbine blades working in the overtemperature state.
A single unrecoverable surge indicates that the compressor blade may be broken and needs to be shut off as soon as possible to avoid further deterioration.
Flameout means that the combustion process in the combustion chamber stops as the engine speed and EGT decrease.
There are various causes of engine stalling.
Such as lack of fuel, encounter volcanic ash, heavy rain/hail/ice, engine surge stall etc.
Engine flameout can cause multiple cockpit instructions to malfunction, such as electrical and hydraulic systems.
In a period of time after engine flameout, because the failure engine is still in the wind, the speed will not be lower than the slow car, the hydraulic low-pressure light will not be bright;
If the throttle is in the slow position and the roll is not obvious, the crew may misjudge an electrical system failure rather than an engine failure.
It is recommended to pay attention to engine parameters when there is an indication of electrical system failure, after all, aircraft power is the most important.
About 10 percent of stalling starts occur during takeoff.
Stalling occurs most frequently at low and medium power Settings, such as cruise and descent.
You’re probably flying on autopilot.
Autopilot will be disconnected (assuming a working autopilot is switched on) after maximum compensating for the thrust asymmetry.
This means that the crew needs a lot of rod force to keep the plane under control.
If there is no visual reference, such as transoceanic, night, cloud flight, the possibility of losing control of the aircraft increases.
There have been several cases of engine flameout at low power and accidents due to improper unit operation.
A badly damaged engine means that the hardware has been damaged and the engine cannot function properly.
For example, bearing failure, foreign body inhalation damage fan blades, rotor disk failure and so on.
The limit for judging serious engine damage is difficult to define.
In the opinion of the engine manufacturer, significant damage (such as a large hole or part missing) and no response to moving the throttle can be judged as serious engine damage.
Serious engine damage can be accompanied by other conditions.
Such as fire (hot bleed air leakage) or surge.
There may be a loud noise, N1, N2, fuel flow drops, EGT briefly rises, and the engine rapidly loses thrust.
Its characteristics are similar to the unrecoverable surge described in the third part.
Engine separation is extremely rare.
It usually occurs during takeoff climb or landing run.
All primary and secondary engine parameter indications on the affected side have disappeared.
In the case of high power, the aircraft roll significantly.
Reach the rudder pressure plate as soon as possible to control the aircraft condition and level the slope.
Pull out the fire handle of the affected engine. This will quickly close the SPAR fuel valve to prevent a large fuel leak.
The latest market dynamics at any time to see, please pay attention to.
