Monday, 11 December 2006 07:17
Hi Captain Lim,
I hope you have a chance to answer this one: What if the ailerons ceased to function?
The function of ailerons is to enable a plane to turn left or right in flight. The word ?aileron? means "little wing" in French. They are hinged control surfaces attached to the back of the wings so that when one goes up, the other one goes down; the up going aileron reduces the lift whilst the down going one increases the lift. This produces a rolling moment that enables the plane to turn when the pilot in the cockpit moves the control column (steering wheel).
So, is it critical if the ailerons ceased to function? Depending on the type of plane involved (light single engine aircraft or large commercial jets), it does pose a problem but it is not entirely a life and death issue. Some form of control is still possible.
Yes, in the event of loss of the ailerons, some degree of roll control is available by using the secondary effect of rudder. While not an efficient way to turn the aircraft, a pilot has at least some directional control. Short or rapid bursts of power may increase the effectiveness of the rudder to some degree. It can act as a form of torque and slipstream effect. So, an aircraft with a jammed aileron can indeed be landed in a slip, preferably against a crosswind.
Well, the scenario above is just about the ailerons. What if the pilot also loses the most important flight controls ? the elevators that enable a plane to climb and descend?
Wow! It would be a nightmare! That was what happened to a DC-10 in Sioux City, Iowa in July 1989. The plane lost all flight controls (elevators, rudder and ailerons) due to total loss of hydraulics in the three systems.
In such a situation, the only available method of controlling the aircraft was by adjusting the throttles of the remaining two engines; running one engine faster than the other to turn the plane, and accelerating or decelerating in order to gain or lose altitude.
With no controls working except the power levers for the two remaining engines, the DC-10 broke up during the emergency landing on the runway. Owing to the skill of the crew and an instructor pilot, 184 passengers and 10 crewmembers out of the 296 people on board survived.
On the Boeing 777s or the Airbus A320s - when all the main flight controls are lost due to either hydraulics or total electrical problems, we still have the mechanical back-up to steer the plane and provide a degraded form of control for the planes.
With a better flight control and refuse-to-crash technology, I can see that the airplanes of the future will definitely be a marvel - with no worries of controls failures!