Finding Ways to Control Flight

Issue: 06-2012By Air Marshal (Retd) V.K. Bhatia

CFIT is a leading cause of airplane accidents, as the pilots are generally unaware of the danger until it is too late. But whether modern technologies can take on the challenges of eliminating the scourge of CFIT from aviation in its entirety, is yet to be seen.

Even though it may appear somewhat premature, the possibility is so strong that some open sources have already listed the May 9 SSJ-100 accident in Indonesia in the category of CFIT. But what exactly is this devil called, ‘CFIT’? For the uninitiated, CFIT or ‘controlled flight into terrain’ describes an accident in which an airworthy aircraft, under pilot control, is unintentionally flown into the ground, a mountain, water, or an obstacle. CFIT is a curse which has continued to cloud the flight safety records of every nation on earth in their respective histories of aviation. The term was however coined only in late 1970 by the engineers working at Boeing. According to Boeing, CFIT is a leading cause of airplane accidents, resulting in maximum loss of life as the pilots are generally unaware of the danger until it is too late.

While there are many reasons why a plane might crash into terrain, including bad weather and navigation equipment problems, it is claimed that pilot error is the single biggest factor leading to a CFIT incident. Even highly experienced professionals may commit CFIT due to fatigue, loss of situational awareness, or disorientation. CFIT is considered a form of spatial disorientation, where the pilot(s) do not correctly perceive their position and orientation with respect to the surrounding terrain.

The incidents often involve a collision with terrain such as hills or mountains and may occur in conditions of clouds or otherwise reduced visibility. CFIT often occurs during aircraft descent to landing near an airport. CFIT may be associated with subtle equipment malfunctions. If the malfunction occurs in a piece of navigational equipment and it is not detected by the crew, it may mislead the crew into improperly guiding the aircraft, despite other information received from all properly functioning equipment, or despite clear sky visibility that should have allowed the crew to easily notice ground proximity (compare tunnel vision).

Some pilots, convinced that advanced electronic navigation systems coupled with flight management system computers or over-reliance on them, are partially responsible for these accidents, call CFIT accidents “computerised flight into terrain”, but that is just a manner of speaking.

There have been innumerable instances of CFIT both in military as well as civil aviation fields. The in-built hazards of military aviation make it more prone to the dangers of CFIT. On the other hand, more lives are lost due to instances of CFIT in civil aviation as these include large passenger airliners and even a single accident can result in much greater number of fatalities. On the civil side, a list of CFIT available through open sources includes airlines from all over the world which have experienced such accidents sometime or the other in the past. In India alone, the oldest state-run airline, Air India, has had as many as three major crashes in the last six decades due to CFIT. The first one occurred on November 3, 1950, when Air India Flight 245 Malabar Princess, a Lockheed L-749 Constellation carrying 48 people (40 passengers and eight crew), flying on the Bombay-Cairo-Geneva-London route, crashed on Mont Blanc, France, killing all on board. Ironically, the second incident occurred under similar circumstances. On January 24, 1966, Air India Flight 101 Kanchenjunga, a Boeing 707-420 carrying 117 people (106 passengers and 11 crew) once again crashed on Mont Blanc, France, on the border between France and Italy, killing all on board. Among the dead was the noted Indian nuclear scientist, Homi J. Bhabha. But the one which involved greatest loss of lives occurred on January 1, 1978, when Air India Flight 855 Emperor Ashoka, a Boeing 747-237B crashed into the Arabian Sea after takeoff from Sahar International Airport (now Chhatrapati Shivaji International Airport) in Mumbai, killing all on board (213 persons; 190 passengers, 23 crew). In all these cases, the main cause of the accident was lack of situational (terrain) awareness on the part of the crew due to flying in poor visibility conditions.

The Indian Air Force (IAF) too—the largest practitioner of military aviation in India—has had its share of CFIT accidents, three of these occurring in quick succession involving a transport aircraft (An-32), a helicopter (Mi-17) and a jet fighter (MiG-29). Once again, all these were attributable to lack of situational or terrain awareness while flying in weather/poor visibility conditions. Globally, who can forget the 1995 tragic CFIT accident when three Su-27 jets of the famous Russian Knights aerobatic team flew in formation into a mountainside near Cam Ranh, Vietnam during approach while en route home from a Malaysian air show, in adverse weather conditions.

The fact that CFIT poses real peril to aviation of all forms and categories have been appreciated for a long time with major efforts having been dedicated to evolve systems and methods to curb the menace. Traditionally, adequate procedures and crew coordination and communication (CRM) as well as control or surveillance by air traffic services may reduce the likelihood of CFIT (But was it missing in the case of SSJ-100 accident?).

On the technology front, in order to prevent the occurrence of CFIT accidents, manufacturers and safety regulators developed various terrain awareness and warning systems (TAWS). The first generation of these TAWS systems was known as a ground proximity warning system (GPWS), which used a radar altimeter to assist in calculating terrain closure rates. This system was further improved with the addition of a GPS terrain database and is known as an enhanced ground proximity warning system (EGPWS). This and the older system have mandatory pilot procedures and actions following any caution or warning event.