Tuesday, 1 October 2013

Did crash pilots feel under pressure to land?

Investigators from the Irish Air Accident Unit will today be trying to understand why the pilot of the Manx2 Fairchild Metroliner tried to land after aborting two earlier attempts and circling for 20 minutes in a holding pattern hoping for conditions to improve.
There are no suggestions that the foggy conditions improved significantly. Did the pilot feel under commercial pressure to land at his destination rather than incur additional expenses for his employer? A diversion is always costly.
Apart from the cost of relocating the passengers by road or air to their original destination, the passengers due to join the flight can claim compensation if their flight is delayed too long. Some airlines require pilots to provide an explanation if they are as little as three minutes late, a situation which often places them under pressure to keep to a schedule.
Or were the pilots subject to a phenomenon colloquially known in aviation as “getthereitis,” where an overriding sense of duty to get their passengers to their destination impelled them to throw caution to the wind and risk a foggy landing? Yesterday’s fatal crash of the Manx2 airliner at Cork has chilling parallels with the crash of a Polish Air Force passenger jet carrying that country’s president Lech Kaczynski and 95 other senior officials and relatives at Smolensk last year. Both occurred in heavy fog. In the Smolensk crash there is evidence the pilot felt under pressure to land, even though air traffic controllers advised against it.
Regulations require a passenger aircraft to have sufficient fuel for both a hold and diversion to the nearest airfield so shortage of fuel is unlikely to be an issue. Fog is a capricious element and, while one moment an approach appears clear, within seconds it can swirl in and obstruct the runway. Flying through fog can give rise to a condition known as vestibular disorientation, where the pilot’s natural balance organs convince him or her the aircraft is flying level when in fact the opposite is the case.
At this early stage of the investigation there are no indications of any faults with the airplane. It was built by the Fairchild company, which has in recent years tended to specialise in continuing the production or operation of aircraft whose original manufacturer has ceased production.
It stems from a design which originated in the 1960s. The aircraft which crashed in Cork was manufactured in 1992. An aircraft of that age would be designated an “ageing” and, while perfectly safe to fly, would be subject to extra maintenance checks to ensure its reliability.
There have been about 16 serious accidents involving the Metroliner. In 2005, a New Zealand Post Metroliner crashed, and a week later another crashed in Queensland, Australia killing 15. No connections were found between the two disasters.
The aircraft carries 19 passengers, a number contrived to avoid regulations such as the need to carry cabin crew. It may also be below the size threshold for the installation of “Black Box” flight recorders, the Flight Data Recorder (FDR), which records the aircraft’s progress though the air, and the Cockpit Voice Recorder (CVR), which records conversations between pilots on the flight deck. A spokesman for the UK Civil Aviation Authority which supervised the airline said yesterday it recommended the installation of these recorders where possible, even when it was not mandatory.
At the time of writing there is no indication that any recorders have been recovered. An FDR would yield valuable information regarding the aircraft’s progress through the air, although many recorders of the aircraft’s vintage supplied limited information, especially if they were manufactured for US operators. Older FDRs could show parameters like the aircraft’s heading, altitude and speed, but might not reference issues such as what controls, ailerons, flaps and the rudder, were operated by the pilots.
But even the best FDRs have limitations. They may show what the aircraft did, but not why. And that is why the Cockpit Voice Recorder can prove invaluable. Very often the pilots have described the incidents leading up to crash, and highlighted issues which might not be recorded on the FDR. Even the rate at which they speak can tell investigators a lot about their state of mind, whether or not they were panicked, or if they were bewildered by something unusual happening to their aircraft. In the case of USAir Flight 427, which crashed on approach to Pittsburgh in 1994, investigators were able to demonstrate the rudder pedal had jammed because of the unusual laboured grunts emitted by the co-pilot who was flying the aircraft.
The lack, if any, of Black Boxes, may be compensated to some degree by the conversation between the cockpit and the air traffic controllers at Cork. These are always recorded and will be carefully listened to by the investigators. Tapes of the radar returns from the doomed aircraft will also be closely studied, although this will be less reliable close to the ground. They will reveal the aircraft’s rate of descent and its speed.
But initial probes will take place on the runway as investigators sift through the wreckage seeking clues to what happened. They will first of all try to establish where the aircraft first impacted the ground and will carefully look for scrapes on the tarmac, or furrows in the grass verge and attempt to relate them to parts of the aircraft. The aircraft was found upside-down and there will be pressure on investigators to figure out how, and why, this happened.
One reason for an inverted wreckage is that the aircraft came down heavily and at speed on its nose and that this caused it to somersault. However, pictures of the wreckage show the nose-wheel is in position: in a heavy, nose-down impact the nose-wheel would more than likely have snapped off, or be forced up into the fuselage. A more likely explanation is that there was a wing strike, where the wings were not level and one wingtip forcibly struck the ground in a manner which caused the aircraft to flip over onto its back. If there was a wing-strike, could the fog have contributed to the pilot’s inability to keep his aircraft level?
Because of vestibular disorientation, the US armed forces lose on average of between 20 and 30 aircraft annually. The US Federal Aviation Administration lists it as the leading cause in 15% of fatal small aircraft crashes and it was blamed for the crash of seven Dutch F-16 fighters.
It can occur when pilots lose visual clues to their surroundings and, either because they misread, mistrust or ignore their instruments, allow the aircraft to wander off course, develop an excessive bank and eventually spiral out of control with the pilot often not realising his or her predicament until too late. Experiments conducted more than 20 years ago by the University of Illinois showed, with the autopilot switched off, a pilot can lose control in as little as 20 seconds if denied sight of instruments.
The human body has its built-in spirit level in the inner ear which controls our balance. Also known as the vestibular system it consists of the semi-circular canals of the inner ear plus a system of small fluid filled sacs containing sensitive hairs, which respond to gravity. Pilots flying in the dark, in fog or in cloud are particularly vulnerable to a phenomenon known as the “leans”. This occurs when the vestibular system gives a false reading after a long period of being banked at an angle, or in a turn, such as a prolonged period in a holding pattern, and they imagine they are flying straight and level. When they level their aircraft according to their artificial horizon, they often mistrust the instrument because their vestibular system has fooled them. A confused pilot will often apply the wrong controls and precipitate a fatal spin. Closer to the ground it could result in a wing-strike.
Investigators will try to establish if this, or something similar happened to the Manx2 pilots. The 20 minute holding pattern they flew would have been more or less circular or racetrack shaped and a prolonged period of constant turns in the same direction could easily give rise to a case of the “leans”. It may be an issue probed by investigators.
* Gerry Byrne is an aviation journalist
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