Controlled Flight Into Terrain, is the technical term for planes being flown into mountains in cloud by pilots who are either disoriented or careless. Of the 18 crashes in Nepal since 1992, 16 have been caused by CFIT leading to the loss of nearly 400 lives.

On Wednesday morning, a Yeti Airlines Twin Otter with 19 people on board crashed on the threshold of Lukla's sloping runway, killing everyone on board except the pilot. Fourteen of the passengers were German tourists with two Australians and two Nepalis. Two crew members also died.

This time the inquiry into how the plane fell short of the runway will be easier to ascertain because the pilot is said to be out of danger. Eye witnesses said the Twin Otter was trying to land when low clouds moved into the approach path, the pilots appeared to have decided to land anyway since two Yeti Twin Otters had just landed previously.

The November 2006 crash of a helicopter in Ghunsa in eastern Nepal killed 25 people, including Nepal's senior conservationists. Yeti itself has lost three Twin Otters in fatal crashes in Jumla, Surkhet and on Lamjura Pass near Lukla in the past five years. The Jumla crash was caused by a stall during a tight turn before landing, but the other two were CFIT.

Two Twin Otters also flew into mountains in cloud in 2000 and 2002 on flights from Jomsom to Pokhara. There have been five other Twin Otter crashes that have been classified as CFIT in the past 15 years. An UNMIN helicopter also crashed into mountains in Ramechhap in March, killing 12. An Asian Airlines MI-8 helicopter that disappeared on a flight from Makalu Base Camp to Lukla in 2002 has never been found, probably because it hit a mountain and was buried by an avalanche it triggered.

The biggest disasters in Nepal's aviation history occurred within two months of each other in 1992 when Airbus 310s operated by Thai International and PIA both flew into mountains during a bad weather approach into Kathmandu, killing a total of nearly 300 people.

The combination of high terrain and clouds makes flying dangerous during the monsoons. Says one Twin Otter captain: "The rule is that you never fly into cloud in Nepal unless you know exactly where you are and what is the minimum altitude for that position."

Aviation experts say cockpit equipment that give audio terrain warning are not very useful because they go off all the time while flying in the Himalaya, pilots find them irritating and just switch them off. A state-of-the art Enhanced Ground Proximity Warning System that combines satellite-based mountain data with onboard terrain radar could prevent CFIT, but these equipments are expensive and most Nepali domestic operators say they can't afford them.

Until EGPWS become mandatory, the only way to prevent planes from colliding with mountains in bad weather is for airlines to enforce stricter safety procedures and improve training.

Video of Lukla crash

http://blog.flightstory.net/970/video-dhc-6-twin-otter-crashed-at-lukla-nepal/

ALSO SEE

Void From Issue #317 (29 SEPT 2006 - 05 OCT 2006)
Wing and prayer From Issue #317 (29 SEPT 2006 - 05 OCT 2006)
CFIT From Issue #3 (02 AUG 2000 - 08 AUG 2000)