March 14, 2014 00:00 By Ravi Madavaram 5,823 Viewed
Malaysian Airlines MH370 took off from Kuala Lumpur in the early hours of Saturday, bound for Beijing. Less than two hours later, the aircraft lost contact with air-traffic control. No distress call was made by the pilots. The aircraft was flying at 35,00
Evidence from past incidents suggests there are six possible explanations for the disappearance of aircraft.
1. A combination of technical and pilot errors leading to a snowballing effect: No single factor generally leads to a plane crash, but rather a combination of technical glitches and pilot decisions. Taken individually, each of these glitches and decisions are harmless and occur frequently. It is the combination of such factors that lead to a catastrophe. This is what happened to Air France 447 in 2009. There was no distress signal from Air France 447, as the pilots did not realise that they were going to crash until seconds before they hit the Atlantic Ocean off Brazil.
2. Structural disintegration: This can refer to structural failure which causes the pilots to lose control of the aircraft. This last happened in 2002, to China Airlines Flight 611 as it cruised at 35,000 feet. Flight 611, a Boeing 747, crashed because of a faulty repair. The 747 entered service in 1975, making it 20 years older than the Boeing 777, which first flew commercially in 1995. The newer aircraft boast better materials, technology and maintenance schedules.
3. The human factor: Deliberate action by passenger or pilot to crash the aircraft. The 9/11 World Trade Centre incidents brought this explanation to the fore.
4. Bad weather: Inclement weather conditions such as snow, fog, rain and ice can affect the performance of the aircraft, which in turn can result in a crash. These weather conditions more often affect the critical flight stages, like landing and takeoff. However, MH370 had clear weather throughout the flight and disappeared during the calmest period of the flight, at cruising altitude.
5. Total electrical failure: Airliners have three types of electrical power source – two generators (each engine has one), APU (Auxiliary Power Unit) and RAT (Ram Air Turbine). For a total electrical failure, all three systems would have to fail at the same time. Such an event is rare but not unprecedented. A Qantas flight lost power coming into land at Bangkok in 2008. The aircraft landed safely after the pilot switched to backup power from APU.
6: Hijack is the sixth major possible explanation for an aircraft’s disappearance during flight. But in the case of Flight MH370, a hijack can be ruled out for the following reasons:
_ A hijacked plane the size of the 777 would have been caught on radar.
_ It would be impossible to keep the aircraft and passengers hidden for five days.
_ No group has claimed to have hijacked the plane.
What kind of distress signal is expected when a crash happens? Will electrical failure affect the distress transponders or beacons?
Regulations require commercial civil aircraft to carry Emergency Locator Transmitters (ELT). They are activated during a crash by the G (gravity) force they experience or by pilots’ input. Another distress signal, the Underwater Locator Beacon is attached to the flight recorder – more commonly known as the black box. The black box beacon is activated when it comes in contact with water.
Assuming the aircraft crashed into water, the ELT’s would have sent signals, but they are not waterproof. The ULB starts emitting signals the moment it touches water.
Important facts to note:
Although the aircraft may be emitting an automatic distress signal, these signals have a limited range and hence may not be being picked up.
Pilots may realise that a crash is imminent only 5-10 seconds before the accident. Only after 30 minutes to an hour does air traffic realise that something is wrong and start looking for the aircraft, by which time the beacons can be hundreds of metres underwater.
The signal from the Underwater Locator Beacon can travel hundreds of kilometres. But if the black box is covered with debris or falls into a trench at the bottom of the sea, then the strength and range of the signal will be weaker.
The ELT and beacons use their own batteries, so electrical failure does not affect them.
Should the beacons run out of battery, what are the options?
The batteries of the black box beacon are designed to last 28 days. If the black box beacon battery dies and the plane is not located within that time, then the only hope is to find the debris and try to work backwards from there.
Ravi Madavaram is an Aerospace & Defence Practice consultant at industry researchers Frost & Sullivan Asia Pacific.