Flap Limit Protection on 747 'Classic'
I am aware that the 'Fast/Slow' pointer on the ADI in the Classic is driven by the difference between the Command Airspeed Bug and the Captain's ASI.
I was wondering whether or not anyone knows where the Flap Limit Protection system gets it's airspeed information from? And while I am here, does anyone know where it is written that the overspeed warning system senses whether or not there is fuel in reserves 2 and 3? This enables it to sound the overspeed clacker at either 342KIAS or Vmo, independent of the Aux/Norm switch selection on the ASI. Thanks in advance. |
Did you just start in QF did you?
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Flap limit protection from 3 off capsules in the crawlway sensing pitot pressure, active when flap lever at 25 or 30 units.
Will retract the t/e flaps from 30 to 25 to 20 depending on the overspeed. Early a/c only had one q switch and only retracted the flaps from 30 to 25 units. Reserve fuel overspeed warning from fuel level float switches in reserve tanks 2 and 3 when either tank not empty. mm 34-14-00 |
Gas Path:
So the system senses the pitot pressure directly and doesn't take an input from the CADC? Thanks for the info. I couldn't find the reserve fuel information anywhere! |
No, just the switches in the flap lever, the 3 q pots, the flap load relief light on p2 and the load relief actuator.
The flap lever switches are to arm the system and prevent it operating unless the t/e flaps are selected to greater than 20 units. Pitot pressure comes from the aux pitot no1 (l/h side lower) |
Gas Path:
Excellent, thanks for your help. I will have to get my hands on one of the maintenance manuals and have a look now. Should be interesting trying to track one of those down! |
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