Dear Capt Kay,
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
Internet Specialist
NSW 2112 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.
Regards,
Capt
Kay
Note:
This is a personal view and does not reflect that of the
Manufacturer. .
Hi Capt Kay,
Thank you very very much. Your answer as well as the FAQs
have now covered all the areas I was curious about.
I don't think I could thank you enough for your time.
Thank you and Regards,
Raid Asfour
Internet Specialist
Ryde NSW 2112 Australia
Airbus
330 suffered two engine failures
On 8th
August 2001, an Air Transat Airbus 330 en route from
Toronto to Lisbon with 293 passengers and 13 crewmembers
suffered two engines failures.
The twin-engine aircraft is certified to operate
under the ETOPS 120-minutes rule.
This means that the aircraft is permitted to
divert with one good engine to an alternate airport up
to a maximum of two hours away. (about 850 nautical
miles)
The Flight
was cruising at 39,000 feet when the flight crew
realized that there was an imbalance of fuel between the
main tanks. They
were concerned with the fast depleting fuel quantity and
decided to divert to Lajes Field Airport, located on
Terceira Island in the Azores, 850 miles west of Lisbon.
The crew then
ascertained that there was a leak somewhere that had
caused the excessive fuel loss.
They then declared an emergency.
When they were 136 miles from Lajes, the right
engine failed. As
the aircraft was drifting down on the good engine at
34,500 feet, they ran out of luck! The remaining engine
failed on them as they were about 85 miles out from
Lajes. The crew
was uncertain as to whether they could glide towards a
landing at the Airport and advised the Air Traffic
Control that ditching at sea was a possibility.
The Airbus
330 became a virtual glider when all the fuel tanks were
empty, causing both the engines to quit on them.
It was very fortunate that they were able to
glide towards the airport at night and touched down
safely on the two mile-long runway. It came to a safe
stop, not after bursting eight of its ten tires. There
were some minor fires on the main gear wheels but the
Fire Fighting Services extinguished them without any
problems.
Only nine
passengers and two crewmembers received minor injuries
during the emergency evacuation.
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