Originally Posted by PJ2
If I recall correctly, the Quito accident appears to have been caused by damage to the oleo position sensors which prevented the ground spoilers from deploying which in turn prevented the availability of reverse.
Just a minor correction.
According to early Accident Information Telex by Airbus, the A340-600 in Quito did get spoiler deployment, but did not get autobrake or reverse thrust.
The sequence was as follows:
- Very hard touchdown (~1100ft/min)
- On-ground-Condition initially fulfilled -> Spoiler deployment. With the thrust levers in idle or reverse, spoilers remain deployed, even if WoW-signal is subsequently lost, e. g. during a bounce.)
- A wiring loom at both main landing gear bogies failed, severing the wires that transmit WoW signals
- Abrupt bogie derotation caused all four main gear front tyres to burst
- loss of WoW signals prevented reverse thrust activation.
- I'm not 100% certain what caused the autobrake failure. Autobrake is initially triggered by the same signal that is used for spoiler deployment, but, unlike spoilers, autobrake operation may depend on a continuous WoW signal. It may also turn off if tyre pressure is too low, although this is not mentioned as an arming condition in the FCOM.
Bernd