Thai A330 accident at BKK

[J.O.]

No it wouldn't because the basic fly-by-wire architecture in the Airbus system is such that it maintains the last selected pitch attitude. So, unlike in a conventional aircraft where the reducing energy results in a decreasing pitch attitude, without the flare law, the Airbus would feel unnatural in the flare.

[nitpicker330]

Quote from my A330 FCOM relating to flight control laws---


FLARE MODE

When the aircraft passes 100 ft RA, the THS is frozen and the normal flight mode changes to flare mode as the aircraft descends to land. Flare mode is essentially a direct stick-to-elevator relationship (with some damping provided by the load factor and the pitch rate feedbacks). At 50 ft, a slight pitch down elevator order is applied. Consequently, to flare the aircraft, a gentle nose-up action by the pilot is required.

[Metro man]

Wouldn't slowly reducing the power levers to idle cause the nose to pitch down anyway?

Power gets reduced quite quickly in a jet on landing. There is still noticeable residual thrust from the engines and keeping power on results in floating past the touch down zone. Jets require longer runways than turbo props and what may be plenty for an ATR could be very limiting in a jet.

Below 2000m in an A320 requires a bit of attention and proper technique. Stopping performance is best on the ground with brakes, spoilers and reverse thrust applied. People come to grief with tail strikes and overruns by holding off too long for a smooth touchdown.

[joy16]

Below is the update news for this incident.

THAI executive vice-president of the technical department, Montree Jumrieng, said yesterday initial investigations and examination of the flight data and cockpit voice recorder found a cracked bogie beam caused the landing gear to collapse and the airplane to veer off its runway.

The finding may mean that other bogie beams of the same type will suffer from similarly impaired functioning, he said.

A bogie beam is an H-shaped steel part that links a shock strut, a wheel and its brake. The bogie beams of problematic type are equipped in 12 Airbus A330-300 aircraft that THAI imported in the first batch of its 27 Airbus A330-300 airplanes.

"Previously the life of the bogie beams was set at [the plane's] lifetime. Later there was an announcement to limit its life to 50,000 flight cycles, but the plane in the incident had been used for only 40,000 flight cycles. This is the first reported case of a bogie beam cracking from its base to its top," Flt Lt Montree said.

He said the case makes further reduction of the bogie beam's life likely. An official announcement will be made by Messier-Bugatti-Dowty Co, the landing gear producer, and Airbus.

You can read full story at Bangkok Post.

[Capn Bloggs]

40,000 cycles in an A330-300? Isn't that a real flogging?

[Capot]

If, repeat if, the average sector is 4 hours, and if, repeat if, the aircraft does 3,000 hours a year, 40,000 cycles is 53 and a bit years of life.

If it's 4000 hours/year (is that really possible?) then 40,000 cycles is 40 years of airframe life.

But those assumptions may be way out. If the average sector is well above 4 hours, as I suspect it might be across the whole fleet, then 40,000 cycles requires an even longer life.

[Brenoch]

That said, the A330 is quite widely used domestic in Thai Airways and also on a fair few high density, short haul routes in the Far East. Nonetheless, it would have been nowhere near 40000 cycles.