Image: 123RF
An upside-down plane?
Can an airliner fly upside down?
This is an interesting question from Lisa Anderson. Perhaps she may have seen the movie Flight where Academy Award winner Denzel Washington ‘skillfully’ maneuvered his plane during an uncontrolled dive. Miraculously he put it upside down before rolling the wings to right-side up for a successful crash landing.
He acted in the lead role in the movie and his superb performance earned him an Oscar nomination.
Yes, it is possible to fly inverted momentarily but definitely not on a sustained flight in a modern airliner. There are mechanisms that protect it against such an action. Additionally, there are other adverse consequences too.
On the modern Airbus, it’s not feasible to bank (raise the wings) beyond 67 degrees left or right. Hence, a pilot cannot roll (turn) the plane upside down. However, when the plane is not in the ‘normal law’ (an Airbus jargon meaning when all the flight control systems are running fine), this bank protection is lost.
Even though it is possible to fly as such, prolonged inverted flight would not be a good idea as the wing load protection may be reduced. If the wings loading exceeds minus 1 ‘g’ during the inverted flight, structural integrity to the wings cannot be assured – see my previous posting under, ‘Why a plane wings don’t break?”
During the process of going into the upside-down position, the pilot must carefully maneuver his plane with a constant 1 ‘g’ force such that ‘a glass of water placed level on top of the dashboard in the cockpit would not spill’.
To date, no pilot has ever done so intentionally in an actual commercial flight except once during a demonstration flight on a Boeing 707 by the Chief Test Pilot Tex Johnson, unauthorized, in 1955. His maneuver in aviation is known as a positive barrel roll.
What he did was not really an inverted flight as he had to hold a positive 1 ‘g’ force on his flight controls. Even then, it was only for a very short while because the pipe to suck the fuel from the tank to the engine are at the bottom of those tanks. In just a few seconds, they would suck plain air only and the engines would soon shut down.
The small aerobatic plane and combat aircraft you see flying upside down at air displays have special tanks to cater for such negative loading flights.
Any further negative ‘g’ will cause the passengers to fly onto the roof and toilet water would splash all over the cabin!
Hence, negative wing loading should never be allowed in passenger-carrying airliners because of the further screams and sick passengers the pilot`s would have to deal with.
Officially, FAA (Federal Aviation Administration) regulations also prohibit inverted flights on all airliners for safety reasons.
Yes, upside down as a stunt flight is okay but no on airliners even though it is a doable feat.
Note: The attached image of an inverted airliner is a photo-shopped illustration only.
See video on Boeing 707 roll by Test Pilot Tex Johnson here