ADC inputs

[VT-ASM]

Folks ,

Does the Air Data Computer take any inputs from the AOA sensors ?
Tried googling but could not find an appropriate answer.

cheers !

ASM

[Mad (Flt) Scientist]

Quite likely dependent upon the specific aircraft concerned.

Some certainly do use AOA as part of the SSEC correction process.

[westhawk]

Representative 2nd and 3rd generation EFIS digital ADC inputs/outputs:
(Various airplane types may combine functions or vary considerably.)

The Lear 60 Digital Air Data Computers utilize sensor inputs from:

-static pressure ports
-pitot pressure probes
-TAT probe

Each DADC provides the following outputs directly to it's respective DPU:

-airspeed/mach
-altitude
-vertical speed
-SAT
-TAS
-over/under speed cues

Air data is also used by FADECs, mach trim, pressurization controller, gear warning, XPDR and a number of other air data dependent systems. FMS can compute ADC inputs to calculate a number of other air data values as well.

In the 60, the AOA vanes and indicators are two completely separate systems independent of each other. An AOA indicator is installed at each pilot station. AOA inputs are used by the stall computers to generate stall warning and to display 1.3 Vs (green line) on the PFD airspeed indicators. Flap position signals are used to bias the indicated AOA, 1.3 Vs display and stall warning activation threshold. An ADC >18,100' signal triggers a 15 kt additive to account for high altitude IAS/EAS differential.

So in short no, the AOA is not an ADC input, but may be used along with air data for certain purposes such as stall warning/recognition.

Hope this info was helpful.

westhawk

[VT-ASM]

@mad(flt)scientist and westhawk

Many thanks for your replies !

ASM

[STBYRUD]

In the 737NG the AOA sensor / alpha vane IS connected to the ADIRU, but according to the schematic NOT to the air data module subsystem.

[low n' slow]

Most often connected to the ADIRS system (to provide an indication of actual flight path) but not fed directly to the AD section.

/LnS

[Denti]

The AoA vane input is used in the 737 ADC. A failure of said AoA will result in completely wrong speeds and altitudes. It even affects GS and W/V displays, all are wrong.

We had a few incidents (one causing a RWY overrun) due to stuck AoA vanes a couple years back. The above result was experienced in the real world situation, as well as being correctly simulated during simulator training.

[emoroid]

AOA

Ht = Static
Ias = Pitot - Static
Mach = Pitot - Static /Static
TAS = Mach * square root of Ti
CAS = TAS modified by AOA
Old mechanical ADC's used these inputs via log cams to produce the outputs

[NSEU]

In the 737NG the AOA sensor / alpha vane IS connected to the ADIRU, but according to the schematic NOT to the air data module subsystem.

According to the Boeing Maintenance Manual, the 737NG also uses the AOA for Static Source Error Correction and to modify pitot values

[t6 sparky]

The 747-400 also uses AoA information for SSE correction.