AOA signals

[ArthurR]

Can anybody help, I need to find an non corrected AOA signal on the A330, Having looked through the manual I see the signals are direct to the ADIRUs, and then in ARINC form to the various inputs, as far as I can tell this is a corrected signal, which in the ADIRU goes through the Resolver convertor, then the Air data processor, with other signals, and finally to the ARINC outputs, can anyone enlighten me. Preferablly a ARINC 429 signal

Many thanks before hand

ArthurR

[ICT_SLB]

My guess is that you won't find that parameter anywhere outside of a special flight test version - certainly that's the case with all our digital Stall Protection Computers - unless it's on a specialized maintenance or set-up bus (unlikely as most modern vanes have alignment fixtures so swapping is straight forward).

If you need it for the FDR, you're already recording Lateral Acceleration (or should be) so it ought to be possible to reconstruct the raw uncompensated AoA - may not meet the original requirement of the FARs/ED-55 but, given the Level A software in the ADIRU, probably defendable as meeting the intent.

[Matthew Parsons]

It might be the difficult way around, but you can record raw ARINC 429 data. Of course, you'd have to turn that data into something useful which could easily take the majority of effort.

[ArthurR]

Many thanks for the replies, it just confirms what I have tried to tell people, we are recording raw data, so the signal will be there

[ICT_SLB]

"It might be the difficult way around, but you can record raw ARINC 429 data. Of course, you'd have to turn that data into something useful which could easily take the majority of effort."

Matthew,
Normally there is no such thing as "raw ARINC 429 data" for AoA. Typically the output from the vane position sensor (usually an RVDT) will be wired directly to the A/D converter within the SPC (or ADIRU in this case). It has a turbulence filter applied to smooth out the slight "buzz" you often get on a vane and is then converted from Vane (the angle sensed) to Body (offset+ratio function) and an Alpha Dot term added. It is this compensated Body Vane Angle that is output to or used by the Stall Protection or Envelope Protection system. [Please note that nomenclature and sequences can vary a lot.] Each step, except probably the Turbulence Filter, can be reverse engineered (post-processed) to arrive at the original value but a the majority of Cert Agencies still require "AoA Vane Angle" - something the reliability numbers don't really allow.

[Matthew Parsons]

ICT, that may very well be. I have no knowledge of the Airbus nor of AOA sensors. I based my comments on ArthurR's original post, "...the signals are direct to the ADIRUs, and then in ARINC form to the various inputs...".

Of course, it can be quite difficult to use whether it has been processed or not, unless you happen to have a "secret decoder ring".

[ArthurR]

Mathew, the signal from the AOA is received by the ADRIU as a cos & sin signal this then goes through a resolver, and then through the processor and on into the ARINC output. Sorry to have missled you.