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Home > Air Safety > What happens when all engines failed in the air?
What happens when all engines failed in the air?
Aviation - Air Safety
Wednesday, 12 December 2007 22:12

Dear Captain Lim,

If an airplane encounters all engines failures during the flight, what will happen? Does the plane start flipping and crash, or it continues to fly while losing height, and how long does it last and how safe is to land?

Raid Asfour,
Australia

Hi Raid,

This is a very interesting question and I am sure many other non-aviators would be interested.

When all engines are failed during flight, not all hopes are lost my friend ! Have you ever heard of gliders flying ? Well, gliders fly without any engines! Okay, I am being too simplistic. Nevertheless, all aircraft can glide to a safe landing but the degree of distance flown varies. Gliders can stay in the air for a long time. Single engine aircraft encountering an engine failure can also glide a fair distance to execute a safe landing provided it has the height.

I am sure your question concern commercial aircraft. Firstly, I must say that all commercial aircraft engines are very reliable and to have all the two, three or four engines failed totally on them are very, very remote. (See my article on How Safe is Flying?). Of course, I am not going to argue with the Murphy's Law that, anything that can go wrong will go wrong.

Okay, I will tell you a true story or two. In 1983, a Boeing 767 belonging to a major Airline in Canada actually lost all their (only two!) engines in flight. The cause of the failure was not because the engines were technically faulty. It was due to human error ! You see, apparently the engineer in charge of refueling the aircraft interpreted the fuel request incorrectly. The pilot requested fuel uplift in kilograms, which is normal (rather than in gallons or liters) but the refueler read it as in pounds. Remember, one kilogram of fuel equals to about 2.2 pounds. So the aircraft had about half the fuel required to fly the distance. Consequently, the Boeing 767 ran out of fuel halfway and both the engines quitted on them !

Of course, the pilots should have realized the mistake but it was unfortunate that they missed the second chain of events which could have prevented the accident. What was fortunate was that, the pilot concerned used to fly gliders as a hobby. He happened to recognize a disused airfield nearby that he used to land before. He then executed a perfect forced landing without any loss of lives or aircraft.

The second story concern another major Airline from the United Kingdom. Its Boeing 747 was enroute from London to somewhere in Australia when it lost 4 engines due to volcanic ash spewing over the sky near Jakarta in Indonesia. Fortunately, the crew were able to restart (or relight in aviation term for jet engines) at least 2 engines when they were cleared of the volcanic ash at a very low level.

Your question was, when an airplane encounters all engines failure, does the plane start flipping and crash, or continue to fly while losing height? If it continues to fly, how long does it last and how safe it is to land the aircraft ?

As I have described earlier, the aircraft does not flip or crash. It continues to fly at an optimum gliding speed, a speed much lower than its cruising speed.

However, it may not be able to maintain its cruising altitude but continues to lose height at a rate of about 3500 to 4500 feet per minute. This will give an aircraft, cruising at 35,000 feet about 10 minutes to fly a distance of about 40 to 50 nautical miles. Remember, pilots have been trained to restart/relight the engines whenever they encounter total engine failures. If restarting the engines were unsuccessful, they would have no choice but to carry out a prepared forced landing - just like what the Canadian pilot did to the crippled Boeing 767.

If you were a passenger on board this ill-fated aircraft, how would it feel like ? Although I have never encounter such an experience as a passenger, I have practiced this exercise many times and have been tested thoroughly in the aircraft simulator.

This is what will likely happen if you are in the passenger cabin. Firstly, if both engines failed simultaneously (very, very unlikely, but normally one after another), the noise level will drop very rapidly. The cabin lights will flicker and may be a bit dimmer. If the aircraft auxiliary power unit (something like a standby generator-cum compressor) fail to start automatically, you will feel the slow depressurization in your ears. Oxygen masks will drop from the ceiling and an automatic emergency announcement will be made through the Public Address System shortly. The cabin crew will then brief you the emergency procedures for a possible Forced Landing or Ditching.

How safe is it to land ? In a Boeing 777, with both engines failed, it is still controllable even though most of the normal hydraulic system pressures would be lost. However, there is the emergency hydraulic pressures generated by the Ram Air Turbine system (RAT). The RAT will automatically extend when it senses both engines had failed. There are fan blades on the RAT which will turn to generate hydraulic and electric power as the aircraft glide forward at a speed of about 180 to 280 mph. The landing gears would be extended by the emergency alternate system and the aircraft has sufficient brake pressure to bring the aircraft to a complete stop using the emergency accumulator pressure.

In a nutshell, if an airplane encounter all engines failures, it is capable of gliding to a safe landing provided there is a suitable landing area. The landing gears would extend and the brake would still function to stop the aircraft safely. So all hopes are not lost !

Hope that answers your question.

Both Engines of a Boeing 737-300 flamed out.

On the 16th of January 2002, a Boeing 737-300 belonging to an Indonesian Airline had both its engines flamed out - a term to describe that the jet engines had failed. It happened as it commenced its descend to 9000 feet through thunderous clouds that were filled with rain.

The crew then tried to relight the engines but it failed to revive. Compared to a Boeing 777 where the relighting process is automatic, the Boeing 737 did not appear to have this more advanced facility. In addition to this, on a Boeing 777, the APU will automatically light up as well when it senses both engine failures. The APU or the auxiliary power unit is a small jet engine that is located in the tail section and powers the electricity and air-conditioning of the airplane.

When the engine failed, the Captain maneuvered the airplane so that it could glide at an optimum speed of around 240 knots. This would cause the airplane to lose height rapidly at about 3000 feet per minute. He then attempted to make a forced landing, but preferred to ditch into water if only he could locate the sea. As the sea was out of reach, he decided to ditch on a river instead.

During the forced landing process, the Captain tried to decelerate from 240 to 150 knots by use of the flaps, but the hydraulics were not available to power the action. (In a Boeing 777, there is an emergency device known as a RAT or Ram Air Turbine, which is powered by free airflow as the airplane glide down with dead engines. The RAT will provide some hydraulics as well as electrical power during this very critical phase of the emergency.) Luckily, the ditching was very well flown and the Boeing 737 came to a stop, floating near the side of the river.

This was one of the very rare situations where a commercial airplane lost both engines and was able to ditch successfully. So Murphy Law is right! Engineers were unable to determine the exact cause of the failure yet but it was speculated that engine icing was one of the possible cause of the flame out. (In this accident, 23 people were injured in the plane carrying 54 passengers and a crew of 6. One stewardess died when she was drowned in the river.

US Airways emergency landing at Hudson River

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Comments (4)

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Aircraft engine failure in flight
Dear Captain Lee,

I am totally satisfied with the answer you have given to a question raised by Mr Raid Asfour-Australia "what happens if all engine fails while an aircraft is in flight." You seem to be an experience pilot. May I know if you are still in service and how many flying years you have. I admire Pilots cause that was my dream when I was a school going boy of 12 years.
Vijay S , 07 Jun, 2012
...
In light of the current problems with batteries being experienced with the Boeing 787 Dreamliner - which has no hydraulics - I am wondering if you know whether the Dreamliner is equipped with an electrical generator equivalent to the Ram Air Turbine system (RAT) you described for getting emergency hydraulics when the engines fail in flight.
RH , 18 Jan, 2013
Whether the B787 has a RAT deployment capability?
Please see answer here http://tinyurl.com/a2next5
Captain Lim , 19 Jan, 2013
...
This makes total sense. Thanks! But I am still wondering: if planes can essentially land with no engines, then why are there plane crashes altogether?
Nadia , 17 Jan, 2014

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