View Full Version : B757 ADC Test
Can anyone tell me what the expected response of the VSI is when either ADC is tested.
There is no reference to these switches in the Op's manuals so I'm not clear about what should be happening.
Is this normally test only carried out ny maintenance?
R.
expedite_climb
4th Oct 2002, 07:14
Not entirely sure but I watched the engineer doing some tests the other day, one of which made all the instruments go funny. If I rember the asi went up 200 kts, and the vsi down to 2000'fpm.
The adi also indicated a roll.
The IVSI has only one indication during an ADC test - The fail flag comes into view. Climb rate is zero.
The full test is as follows - Over speed warning for 2-3 secs, ASI slews past VMO (260 kts at start of test) then back and stops at 138 kts, MACH indicates .75 at start of test and then MACH shutter blanks.
Altimeter slews, whilst slewing fail flag appears, and stops at 10000 ft
VSI indicates zero and fail flag in view.
The VSI does not indicate a rate of climb as its primary i/p is from the IRU with an ADC i/p to the IRU used to augment inertial vertical speed during constant climb conditions.
To see an IVSI output the IRU's need to be tested which will produce, among other things, a descent rate of 600 ft/min.