Coming out of Shanghai recently I called for gear up. The other guy moved the lever up but nothing happenned. The A340 undercarriage is controlled by something called an LGCIU (landing gear control and interface unit) which is essentially just one of the many computers. There are in fact 2 LGCIU’s which take it in turns to do their job, swapping over on each gear extension. When the gear failed to retract we recycled the lever in order to utilise the other LGCIU but still nothing happened. The next option was to reset both LGCIU’s in the hope that one would come back online. This is done by pulling out what looks like a circuit breaker on the overhead panel and interupts the power supply to that computer. Pushing it back in restores power and ‘reboots’ it. In our case this did the job and up came the wheels.
Hope that was simple enough!