Why a plane engine catching fire isn't as disastrous as you'd think

Few sights are more unsettling from a plane window seat than licks of orange and yellow curling around the wing and engine, illuminating the night sky.

The latest passengers to endure such a view were members of the Saudi national football team, whose players watched a fire take hold in the engine of their plane approaching Rostov-on-Don on Monday.

The aircraft landed safely, with a statement from Saudi Arabia announcing that all players were safe ahead of their game against Uruguay on Wednesday: “The fire was merely an accident.”

Pictures posted on social media appeared to show the engine on the right wing on fire as the plane landed. Osama Hawasawi, the Saudi captain, said the fire was the result of a “simple technical fault in the airplane”, but a spokesperson for Rossiya airline, operating the Airbus A319, denied there was a fire and said a bird strike was to blame.

How dangerous is an engine fire?

First of all, engine fires are very rare, with aviation technology so far advanced that such incidents can be prevented in the factory. The fact that flames in and around an engine make the news is indicative of how infrequent they are.

“Because airplane engines are so rigorously tested, engine fires are very rare,” says Saj Ahmad, chief analyst at StrategicAero Research.

“That’s not to say they are flawless, however. Excess oil spillage igniting or fuel leaks or pressurisation within the engines’ numerous piping could lead to a situation where combustion/igniting occurs - but engines are also equipped with fire suppression and containment systems as well as the pilots being able to spool down/switch off fuel to any such engine.”

According to a Civil Aviation Authority (CAA) study of all fatal plane accidents between 2002 and 2011, engine fire was a “primary” factor in just two of 250 crashes, and a casual factor in only six more.

Not only are they rare, but once an engine catches fire, the flight crew has a number of responses at their disposal.

The first thing pilots will do is to shut down the engine, which cuts off the fuel supply, starving the blaze. The crew can then employ fire extinguishers on the engine. If the fire was contained within the cowling, that could be the end of it.

Crew will then seek to land the plane as quickly as possible, making an emergency diversion to the nearest and most suitable airport to assess any damage and ensure the aircraft’s ability to fly safely has not been impacted.

“Bear in mind that an engine fire, while scary-sounding, is by no means a one-way ticket to disaster,” said Tom Farrier, a retired US Air Force pilot and aviation safety contractor.

“In fact, an aircraft is not even considered to have suffered ‘substantial damage’ for accident-reporting purposes if fire-related damage is limited to the engine itself. However, if for some reason such damage goes beyond the engine, perhaps affecting the wing it’s mounted on as proposed by the questioner, there’s definitely potential for trouble to follow.

“Engine fires rarely cause really serious trouble if they remain confined to the engine itself.”

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What damage can an engine fire cause?

Farrier highlights three potential consequences from an uncontained engine fire. First, that a part of the engine damaged in the fire can come loose and be thrown into the fuselage, such was the case with the Southwest aircraft in April when a woman was killed after debris smashed the window next to her seat.

Secondly, the fire might catch some of the aircraft fuel held in the wing, making it harder to extinguish. And thirdly, the fire could damage some of the mechanics required to fly the plane - flaps, hydraulics, etc.

“It’s not an engine fire alone that’s the real concern so much as the possibility that damage might be suffered in conjunction with either whatever started the fire in the first place or an inability to put it out quickly,” he said.

Why you should stay calm

Author and pilot Patrick Smith in his book, Cockpit Confidential, tells a story of how a self-initiated evacuation of a plane at a gate after a passenger spotted a flame coming out of the engine injured two people.

“Miscellaneous engine peculiarities can sometimes put on a show,” he writes. “Aside from a bang, you might see a long tongue of flame shooting from the back, or even the front, of the cowling.

“Tough as it might be to accept, the engine is neither exploding nor on fire. This is the nature of a jet. Any time the engine is running, fuel is combusting, and certain anomalies will unleash combustion rather boldly.

“And when this sort of thing happens at the gate or during taxi, passengers have been known to initiate their own evacuations. One such panic took place aboard a Delta plane in Tampa, Florida. A stampede of frightened passengers made for the exits, refusing to heed flight attendant commands. Two people were seriously hurt.”

At a glance | What is ETOPS?

How far can a plane fly with one engine?

Pretty far.

Given that a plane can fly without any engine power, it goes without saying that if just one engine cuts out during a flight there is very little risk.

Indeed, airliners are designed so that should an engine cut out during take-off, a sole motor will be enough to get the plane off the ground - a phase that requires more thrust than simply cruising.

Due to rules governing airlines, called Etops, planes are required to fly within certain distances (according to aircraft model) of emergency airports so they can divert to land should an engine fail.

Graphic: The distance a plane can fly if both engines fail

Aircraft are, however, capable of gliding with neither engine, but only for a limited distance. Different aircraft have different glide ratios, meaning they will lose altitude at different rates, affecting how far they can fly without engine thrust. For example, if a plane has a lift to drag ratio of 10:1 then that means for every 10 miles of flight it loses one mile in altitude. Flying at a typical altitude of 36,000 feet (about seven miles), an aircraft that loses both engines will be able to travel for another 70 miles before reaching the ground.