Can an airplane fly with one engine? An aviation expert explains
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You may have seen the news that Qantas Flight 144 from Auckland landed safely in Sydney in January after the pilot was forced to shut down an engine and make a distress call while he was flying over the Pacific Ocean.
The aircraft would have been a 10-year-old twin-engine Boeing 737 and was carrying 145 passengers, all of whom disembarked normally after landing.
Unfortunately, these occurrences occur occasionally in aviation – I myself lost an engine in flight – but the good news is that it is extremely rare. This makes aviation the safest mode of transportation in the world.
They are highly trained pilots who spend a lot of time in full motion simulators going through events exactly like this.
When you’re out of engine and have a lot of water under you, you have a process to follow.
It becomes by heart; you don’t freak out, you don’t freak out, you remember your training, and that’s what happened here.
Absolutely. This is what they are designed for.
By law, airplanes must be able to fly from point A to point B, over water, with one engine. Guidelines set by safety regulators in Australia require that any aircraft taking off with the intention of flying to a certain destination must be able to fly there on one engine, based on starting loads determined before takeoff.
This rule ensures that even if one engine fails – as seems to have happened here – the plane can still arrive safely. It can fly until it runs out of fuel. Basically, these planes are built to fly just as well on one engine as on two.
Having only one engine running means you won’t have the maximum thrust power for takeoff, but you’ll be able to fly and land just fine.
But while an airplane can fly with just one engine, it’s very rare for an engine to fail in the middle of a flight.
Airline maintenance procedures are meticulous and technicians are licensed to the same standard and quality as pilots. Typically, you have someone doing maintenance on an airplane on the ground, but someone comes after them, inspects it, and tests it to make sure it’s running at 100% performance.
There are ground tests and flight tests and certification processes that must be completed before an aircraft can pick up passengers. This is why these events are so unusual.
Passengers said they heard a bang on the Qantas flight last month.
It is certainly possible for an engine failure to produce sound. It depends on the type of failure. If it was a section of the engine that was breaking, it could make a noise loud enough for passengers to hear.
But normally, if the pilot needed to isolate the motor and could see pressure fluctuations or motor temperature exceeding normal levels, then the pilot could choose to shut it down before he even heard a bang.
Initial reports that the aircraft’s air conditioning subsequently stopped working suggest to me that the crew likely had to turn off some systems to achieve their goal of landing successfully in Sydney.
When an event like this occurs, pilots have a process to scan their instrumentation to isolate and understand what is happening.
Once they do, we have what’s called a quick reference manual to consult. It lists all potential emergency situations that could occur on an aircraft. Pilots then follow this manual to analyze each step and every possibility, isolating and fixing the problem.
In this case, it seems that the solution was to stop this engine.
As a precaution, Airmen announce a distress call when we have a situation that we believe means we need priority assistance. The Mayday call frees airspace to allow this aircraft to be number one in the queue for priority; all other aircraft must clear.
Air traffic controllers put everyone in the air in a holding pattern or give them a big turn to get them out of the area.
However, some time after the pilot of QF144 made a distress call, he was downgraded to what is called a PAN – which stands for Possible Assistance Needed.
A NAP is a less extreme event; it still signals that it is an emergency, and meant in Qantas’ case that there were emergency vehicles on the runway and the aircraft retained priority status in the queue. But it’s not as bad as a mayday.
From there, a very thorough examination will help shed some light on what happened. Pilots usually undergo drug and alcohol tests and a thorough investigation will be carried out to ensure nothing has been missed and to help Qantas return to normal operations.
I was not there on the flight deck and can only infer from what I have heard and read that the pilots of this aircraft did exactly what they are trained to do.
Airlines spend a lot of money on training so pilots and crew can handle events like this.
As we begin the conversation about single-pilot aircraft and autonomous aircraft, it’s worth asking how AI and autonomous systems might respond to circumstances that aren’t normal events.
Top image: Qantas flight QF144 docks at a gate at Sydney Airport on January 18, 2023 in Sydney, Australia. (Brendon Thorne/Getty Images)