Challenger 604 querie

[floatjockey01]

Am wondering if anyone can help me out. On our Challenger 604 on the ground, with only APU running, all avionics up (Collins Proline 4) the TAS indication on both MFDs fluctuate between 7-10kts. Initially we thought that, with the overeading value it may affect the computed fuel burn airborne but Bombardier seems to think that it does not affect it and couldnt give any clear reason apart from saying that there is no guaranteed ADC acurracy below 100kts

Any input or similar experience would be much appreciated.

FJ01

[smallfry]

is it the wind blowing into the pitots?.... anyway, is it steady in flight or is it fluctuating? if it is steady it is accurate...

[macjet]

Can't be the wind, the IAS starts @ 40 kts (unless it's very windy :-))

sorry didn't read the small printed - it is the TAS that fluctuates?

which interval?

is left and right in sync with the fluctuating values or are they different?

regards

MJ

[floatjockey01]

Inflight it's steady. On the ground, both sides seem to be almost in sync as far as that, say, one side may be reading 7 when at that moment the other says 9. They both however, fluctuate between 7 or say 12.

[Arnold Grayson]

You most likely have already done this but if not flip the switch behind the pilots seat lower left corner to maint. Its a guarded switch. You can then review any faults in the ADC on the MFD. Be sure to review all the faults. We recently had and ADC fail and had indications on the ground similar to the ones you decribe.