Qantas Flight QF2 from London To Sydney
via BKK (Bangkok) (a Boeing 747-400) suffered a total AC electrical loss
15 minutes before landing at BKK on 8 January 2008. The effect of the AC
loss was that all AC powered equipment in the aircraft stopped working
and the crew was forced to revert to standby battery power for
instrumentation. A number of electrically controlled sub-systems were
disabled. Some passenger cabin services were re/started including
emergency lighting. The crew landed successfully at BKK but with reduced
functionality. Power was available only to the Captains PFD, ND and
standby Attitude indicator. They also had to contend with alt gear/flap
extension, no anti-skid, no autobrakes, and no thrust reverser.
Inspection of the aircraft showed that water from the first class galley had overflowed down onto the sub-floor E racks which contained the GCU's (controllers for engine generators) and BPCU (backup PCU) All controllers were disabled resulting in total loss of AC power. The remaining power source was the inverter that generated power from the backup battery.
Luckily his was out of reach of the flood so kept working.
Extrapolation of this event to long-haul flights over sea would have seen loss of all navigation aids and communications, and reliance of the crew on basic aids - if available - such as magnetic compass and sight of stars or sun.
The incident cause was most probably a combination of factors and events that finally resulted in a major problem.
1. The fiberglass drip shield above the E rack had a crack that allowed water to drip through.
2. The last C check at Avalon depot did not discover and remedy the crack.
(QF maintenance as opposed to outsourced).
NB. As of 11 January ABC Radio News disclosed that six other QF 747's were found to have cracked drip trays.
3. Flooding of the first class cabin from the galley is a regular occurrence, usually from ice trays but also from blocked drains.
4. When the galley floods the water goes down onto the equipment bay directly below.
5. The galley drains in first class on OJM at BKK were blocked by coffee grounds.
6. Qantas has changed from 'pillow' style coffee bags to ground coffee
machines - based on cost saving. This results in the possibility of coffee grounds being dumped in the galley sinks.
7. First class in Qantas has a cappuccino machine (also producing coffee grounds).
When you look at it, there are a number of problems that in their own right are perhaps acceptable but in conjunction are a major problem.
- Fundamentally the overflow system for the galley should have been forced to flow to non critical areas.
- The rack drip tray should have been sound and if not the inspection should have picked that up and remedied it.
- The drainage system in the galley should have been immune to blockage.
- The cabin staff should have been trained to avoid provoking blockages in the drain system.
- Qantas should have avoided operational changes (coffee system) that would enable cabin staff to block the drain system.
As a final note. If seven QF 744 aircraft have cracked drip trays, how many aircraft with other operators have the same problem?
from this link