Hydraulic loss/damage aboard an aeroplane
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Hydraulic loss/damage aboard an aeroplane is a phenomenon which may occur in one or more areas of an aircraft.
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[edit] Effects
Whilst a plane can be controlled if just one, maybe even two, steering systems are inoperative, to lose all of them, (usually three or four), makes the plane uncontrollable. The pilots lose the use of flaps, and all of the control surfaces which make the plane turn.
The plane will also enter a phugoid, wild gyrations in which the plane's nose will drop. The drop will generate speed and lift, and the nose will then lift up again. This cycle repeats itself over and over.
[edit] Solutions
By manually closing one throttle and pushing the other one up, the plane will turn towards the engine which is running slower. This was first known to be used by the pilots of Japan Airlines Flight 123.
PCA, or Propulsion Controlled Aircraft, is a technology which is able to control the engines automatically in order to ascend, descend or turn. It was invented by NASA after United Airlines Flight 232. One of the only recorded experiments with PCA was with an MD-11 aircraft. They found that not only was the aircraft's landing survivable, but very similar to a normal landing. However, NASA soon abandoned the idea of PCA. After the Airbus A300 missile strike in Baghdad, which was the first ever incident where a plane had landed with no hydraulics (see DHL Flight on 22 November, 2003), interest in PCA has been revived.
[edit] List of aircraft with hydraulic loss and/or damage
- American Airlines Flight 96 (12 June 1972): One of the first incidents involving DC-10 hydraulic damage was this incident. The situation was similar to the late bombing of Flight 434. After taking off, a cargo door blew out, and hydraulic systems were severely damaged. Using engine thrust, the captain managed to line the plane up with the runway, and, with the elevators still responding, the plane was landing manually. There was a fault in the cargo doors, but Flight 96 would be blamed on an Douglas employee, who recklessly, almost violently, slammed the door shut just before takeoff.
- American Airlines Flight 191 (May 25, 1979): A DC-10 passenger plane lost control after its left wing engine fell off during takeoff. The plane then rolled over into a very steep bank and crashed. It was the worst aviation accident on American soil until 9/11.
- Japan Airlines Flight 123 (August 12, 1985): The worst single airliner crash in aviation history. The bulkhead of this Boeing 747 blew out, causing decompression, and blowing part of the tail off. The pilots managed to keep the plane in the air for thirty minutes, before it crashed into a mountain. 4 of the 524 people onboard survived.
- United Airlines Flight 232 (July 19, 1989): Another DC-10 that found itself in trouble was UA232. The number two engine on the tail blew out, shredding the hydraulic lines on the tail fin. Originally bound for Chicago, the plane, carrying 296 passengers, was flown to Sioux City by Denny Fitch and Al Haynes. Seconds before landing, however, the nose and right wing dropped. At 04:00:16PM, the plane hit the runway and disintegrated. Fuel was spilled, sparking a fire. Of the 296 people onboard, 111 were killed.
- El Al Flight 1862 (October 4, 1992): A Boeing 747 that spiralled out of control and slammed into an Amsterdam apartment block became Holland's worst air disaster. Whilst not all of the hydraulics were lost, the engines that detached caused hydraulic damage on the right wing.
- Philippine Airlines Flight 434 11 December 1994): A bomb exploded on board, planted by terrorist Ramzi Yousef. Whilst complete hydraulic loss was never confirmed, an aileron and control of the stabilizer was damaged, and use of throttles as a means of steering had to be employed. The pilots did successfully land the plane, and only one passenger was killed by the bomb blast.
- DHL shootdown incident in Baghdad (22 November 2003): The first time in aviation history in which a plane was landed without any hydraulics. It was hit by an insurgent's surface to air missile, and the left wing was damaged. It landed at Baghdad airport.
