How far can an aircraft glide with no power?
Is it 10 kilometres or perhaps 20? What about 121 kilometres - because that's the distance an Airbus A330 travelled in 2001 after both its engines failed. The Air Transat aircraft was en route from Toronto's Pearson International Airport to Lisbon in Portugal, when the pilots received a warning of a fuel imbalance. Following procedure, they transferred fuel from the port wing tank to the starboard tank, but unbeknownst to them there was a leak in a fractured fuel line on that side.
With the fuel supply depleting rapidly the crew initiated a diversion to Lajes Air Base in the Azores but as the aircraft descended both engines died as the fuel ran out. The ram air turbine, a small airstream-driven turbine, provided sufficient power for the pilots to control the aircraft's heading as well as powering critical sensors and flight instruments. The aircraft was descending at around 600 metres per minute and a sea ditching was flagged as a possibility when the crew sighted the air base at Lajes.
In darkness the captain flew the aircraft in a 360° turn followed by a series of swooping left-right turns to scrub altitude before the aircraft landed at 200 knots, about 60 knots above standard. With maximum emergency braking applied the captain brought the aircraft to a halt. The crew was hailed as heroes, and their feat went down in aviation history as the longest ever glide by a commercial twin jet aircraft.
What happens to the aircraft when an engine dies?
The aircraft becomes unstable. Powered by a single engine, thrust is delivered from one side instead of two, and that thrust must now be increased to maintain airspeed. Under that condition the aircraft will yaw, move sideways into a turn in the direction of the dead engine, which must be corrected with the rudder. Also, with less power available, the aircraft will no longer be able to fly at cruise altitude. The aircraft will descend to the One Engine Inoperative ceiling, an altitude that it can maintain, most likely in the 20,000-25,000 foot range.
That's what happened to Qantas flight QF144, which suffered an engine failure en route from Auckland to Sydney on January 18, 2023. The aircraft descended from its cruise altitude of 36,000 feet to 20,000 feet, but apart from a jolt when it happened, passengers were unaware of the gravity of the situation. Flaps must be configured differently for a single engine landing, resulting in an increase in the distance required to bring the aircraft to a complete stop, and that could sometimes mean a change of airport.
Source: External
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