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AOA on ground


Rabb

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This had happened several times.

 

 

The mission is set with moderate wind and turbulence, MiG-21 performing cold start. AOA indicator wildly goes from minimum to maximum position and during startup, engine starts producing loud banging noise (compressor stall, probably) and flames out.

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What direction is the wind coming from and how does the aircraft detect AoA? If the wind is high enough and from the rear of the aircraft it MIGHT be causing these issues. Significant airflow from behind could mess with the AoA vanes (if that’s what the MiG has) but as for engine start, I don’t know, I would’ve thought it’d take a hell of a tailwind to cause start issues beyond a high temperature start.

 

Can you try changing wind direction to a headwind and let me know if it helps, I’m interested to find out.

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There are not three rectifiers, just two No. 1 and No. 2. The emergency switch on the right console forces an emergency use of them (I think taking No. 1 offline and forcing No. 2 to do a subset of the normal tasks for No. 1.) In any case the emergency inverter switch should not be used except for actual emergencies or ground testing.

 

 

The latest OB version (and I think the Release too) starts with only the following:

1. Battery

2. Starter motor "APU"

3. Throttle unlatched

 

4. Starter button

 

 

Previously the No. 1 inverter was needed for the ignitors if my memory is right. I'm not sure why the change.

 

 

In any case I couldn't have this rough engine activity even with highly variable winds. Maybe a switch like cone or exhaust nozzle was set wrong or there was some other problem? A reproducible situation would help check.

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