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Jack_Sawyer

Autoland question - A/T yellow light flickering on landing.

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Tonight I wanted to make a test flight to test Orbx's scenery to see if I would get any OOM's.  I didn't.

 

Used PFPX to create a flight from KSEA to KJAC.

 

Flight was fine the whole way, set up for autoland, on final I had LAND 3 annunciated and was very close to landing when on approach I saw the middle yellow light, A/T flickering every few seconds then it disconnected so I had to hand land it from something like 30 feet up.

 

Why did this happen?  I've done a few autolands and it always went well but I have never seen this.

 

I am using FSX Gold.

Win 7 64

Saitek yoke, pedals, & quadrant.

 

Thanks for any help.

 

Jack

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What were you using for weather? I believe this can happen in gusty conditions.

 

Dave

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I had real-time ASN running and had a HUGE wind, 50+ knots kind of headwind.

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Yep, happens to me with ASN in those kinds of conditions as well, I think it's normal.

 

Dave

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Thanks Dave! This helps.

 

I wonder why this happens? Might have to research it.

 

At least I'm not alone.

 

Best regards,

 

Jack

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I wonder why this happens? Might have to research it.
I believe a flickering yellow A/T light means you are to fast when comparing your actual speed with your target speed on the PFD and the A/T is looking for some kind of drag to slow the plane.

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That makes sense, my approach speed was supposed to be 141 but I think it was a lot higher than that. But it was an autoland and the approach was fine till just above the runway. The A/T should have been controlling it all the way down right? Maybe it was that high headwind off the left nose.

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The A/T should have been controlling it all the way down right?

Once the glideslope is intercepted the A/T will not control the speed. From G/S capture to landing you control the speed based upon what Flap settings you are selecting. Reduce your FMC speed to match the speed shown on the PFD for a particular flap setting. See page 81 of Tutorial 1.

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I don't know what the limitations chapter has to say, but I think the maximum headwind for landing and take-off is 25 knots. The maximum headwind is probably less for automatic landings.

 

The A/T probably disconnected itself.

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So it was doing what it was supposed to do. That's good. Learn something new every day. Thanks for the help.

 

Jack

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Once the glideslope is intercepted the A/T will not control the speed.

What?

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Once the glideslope is intercepted the A/T will not control the speed.

 

You are getting this confused. I think what you are trying to say is that the FMC will no longer control the speed.  At glideslope capture if you were in VNAV the MCP speed window will open and you need to set the speed bug manually.

 

The A/T will always attempt to maintain the bugged speed.


 

 


I don't know what the limitations chapter has to say, but I think the maximum headwind for landing and take-off is 25 knots. The maximum headwind is probably less for automatic landings.

 

Max headwind for a CAT II/III approach is 25 knots.  There is no headwind limitation for anything else.

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What?

My mistake. Two words were used incorrectly in post #8. Control should be set and A/T should be FMC.

 

 

You are getting this confused.

Not confused but I did use the two words incorrectly. See reply to Spin737. Thanks for the correction.

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Thanks guys, so my problem was basically I either had too strong of a headwind or didn't use the MCP speed correctly.  I had 141 dialed into the MCP.

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You are getting this confused. I think what you are trying to say is that the FMC will no longer control the speed. At glideslope capture if you were in VNAV the MCP speed window will open and you need to set the speed bug manually.

 

The A/T will always attempt to maintain the bugged speed.

 

 

Max headwind for a CAT II/III approach is 25 knots. There is no headwind limitation for anything else.

Thanks Joe. And thanks Jack, I'd never encountered such a scenario before on the ngx, so I learnt a lot from this thread.

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I think it's normal.

 

Kind of. It happens during a lot of approaches IRL. Not necessarily a bad thing per se, it could be intended. Just an indication the A/T can't keep the speed. If the setup is intended just hit the flashing light to stop it.

 

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