- And The Black Box
Pakistan International Airlines flight PK8303, an Airbus A320 carrying 91 passengers and eight crew from Lahore, crashed just short of the Karachi Airport on 22 May. Two passengers miraculously survived, while 97 perished, including the aircrew.
There have been a lot of speculation about the causes of the air crash. The government instituted an Aircraft Accident Investigation Board to look into the causes while the Airbus aircraft manufacturing company dispatched its own technical team to thoroughly investigate the causes.
Besides taking briefings from PIA and the Civil Aviation Authority and obtaining video and audio recordings of the air accident, the team took charge of the Cockpit Voice Recorder (CVR) and the Black Box, which will provide important clues to the fatal crash.
The decoding of the Black Box and the Cockpit Voice Recorder laid the blame squarely on the Cockpit Crew as well as negligence on the part of the Air Traffic Control. The Federal Minister for Aviation has already disclosed the contents of the investigation to Parliament and measures are being adopted to avoid the recurrence of such an accident in future.
Many readers may be wondering what is a “Black Box”, which has an interesting background. With the rapid development of jet fighters during the Second World War, the British began developing the first jet-powered airliner, the famous Comet, which flew in the 1950s. The Comet however, seemed to be jinxed, and in 1953 a number of the aircraft crashed inexplicably, putting doubt in the public’s mind about the safety of jets.
Aeronautical engineers and scientists all over the world were puzzled. Unless they found the cause of the crashes, the Comet would be doomed to failure. Unfortunately, no clues could be found. There were no witnesses, no survivors, and all that was left of the aircraft were massive tangles of bent metal. Dr David Warren of the Aeronautical Research Laboratories (ARL) in Melbourne, a chemist specializing in aircraft fuels, became interested in the mystery. As he listened to the frustrating discussion of possible causes, he began to conceive the idea of some sort of recording of the flight crew’s conversation, and of protecting the record so that it could survive the crash. He reasoned that while the accident analysis committees found it difficult to trace the cause of the crash, there was a good chance that the flight crew might have known, and it might well have been revealed in their conversation in trying to deal with the emergency.
The number of parameters that the FDRs can monitor will continue to increase as they continue to get even more sophisticated, and they may even store video images from the cockpit to complement the crew voice recordings. Recently a company called Flight Vu has started to produce cameras, which record the events in the cockpit and others that are mounted on the wings and tail of the aeroplane to record the condition of the plane during flight. Air travel has become safest form of transport because of extensive fault analysis, making it imperative for other forms of domestic transport to use recorders to investigate accidents and improve their safety.
Warren propagated his concept, and in 1954 outlined his ideas in a report titled “A device for Assisting Investigation into Aircraft Accidents” and put theory into practice with the support of his Superintendent, Tom Keeble, and an Instrument Engineer, T. Mirfield, designing it with steel wire as the recording medium. It was fully automatic for fit-and-forget operation with a “memory” mechanism that would store four hours of pilot voice and instrument readings at the rate of eight per second up to the moment of any accident but would automatically erase older records for the wire to be re-used. It was given the project name of “The ARL Flight Memory Unit” and the original is now displayed in the Science Museum, Melbourne.
By 1958, Flight Recorders were adopted by the US Federal Aviation Administration (FAA) for use in all commercial aircraft. The Flight Recorder comprised a Cockpit Voice Recorder (CVR) and a Flight Data Recorder (FDR). The CVR records the conversations between members of the flight crew and other sounds in the cockpit as well as radio transmissions and communication with air traffic control units. The most modern versions weigh about 7.3 kg and measure approximately 12 by 15 by 33 cm. The CVR records four audio tracks which are all taken from separate microphones, in the crew members’ headsets and a microphone placed in an overhead panel between the pilots which records sounds such as engine noise, stall warnings and landing gear extensions and retractions, and these sounds are then used to determine parameters such as engine rpm and the times at which certain events took place.
The FDR is considered the more valuable of the two recorders. Its purpose is to collect and record data from a variety of airplane sensors onto a medium designed to survive an accident. The most modern weigh about 7.7 kg and measure approximately 12 by 15 by 50 cm and can record data continuously for 25 hours. It keeps a record of the operating data of an aircraft such as airspeed, altitude and compass heading.
The FDR unit is capable of withstanding an impact with force equal to one thousand times the value of gravity and is located at the rear of the aircraft. The Black Boxes are required to be painted bright orange or bright yellow, making them easier to locate at a crash site. They have pingers and give out radio signals. After the accident the pinger locates the recorders and the orange and reflective stripes are removed from them. The information is extracted and processed using advanced computer equipment. Sometimes a computer model is created as a reconstruction of the whole flight to enable a sophisticated analysis of the flight information at any point during the flight.
The number of parameters that the FDRs can monitor will continue to increase as they continue to get even more sophisticated, and they may even store video images from the cockpit to complement the crew voice recordings. Recently a company called Flight Vu has started to produce cameras, which record the events in the cockpit and others that are mounted on the wings and tail of the aeroplane to record the condition of the plane during flight.
Air travel has become safest form of transport because of extensive fault analysis, making it imperative for other forms of domestic transport to use recorders to investigate accidents and improve their safety.
Hopefully, the Black Box and CVR report will provide closure to the families of the victims of Flight PK 8303 although a new Pandora’s Box has been opened with the issue of fake degrees but that will be discussed some other time.