Anyone had problems with autopilot?

So tonight, I was coming in for landing at KLAX, when the tower told me to make a go-around due to traffic. I was already on my glideslope so I had to push up the throttle and make a pretty hefty pull up. I had a negative VS set on the AP and when I swiped up to change it do a positive, it made it to 0 VS and then when the number was positive my aircraft basically started performing a negative drop in altitude? When I turned off my AP to fix the problem manually, the plane would not let me pull up.

In synopsis: My Vertical Speed setting on Auto-Pilot won’t let me enter in positive climb rates while on my glideslope.

Any idea why this is happening? Any solutions? Is this happening to anyone else? I was using the 737-700 if that helps diagnose the problem.


By no means should you be using that setting to go around. Disable it, reconfig your flaps and TOGA.


We’re you on APPR, I think the that you would need to turn that off first if that was the case?


No my Altitude was off, but for some reason when I turned it back on to set the pattern altitude everything was fixed, this has happened multiple times, I was not using APPR either (the 737’s don’t even have it.)

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I don’t usually do that, but there was another plane on the runway so I was in a rush, and when I disabled it, it maunal didn’t work either.

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You got me it’s time for some shut eye. Either case as Tim said above you should be flying manually regardless.

@Tim_B take it from here, I’m signing off.


Ok, I’ll be sure to do it manually next time. Thanks for your help!

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This is the precice reason while killing the AP and making a manual TOGA makes the most sense.

Certainly, when pressed for time, disabling AP is gonna be a heck of a lot quicker than fiddling with VS


Ok. I’ll try doing that… still this doesn’t just happen when on glideslope, I’ve had it happen when cruising too. Any ideas?

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I’m a little confused. At cruise, you use VS but not Alt?


You did say that you tried to pull up manually too right? The reason that didn’t go up could have been calibration.

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Use manual, turn off autopilot.


You must disengage the A/P (autopilot) and then fly runway heading and manually TOGA for the instructed go-around. Fly with configurations until positive rate and go-around altitude is achieved like flying out of a wind-shear.

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This happend to me to bit only one time.
Did you check your speed because in a sudden altitude change
You speed can change very fast so maybe you where stalling

I hope this helped

Verstuurd vanaf mijn iPad

Did you change the altitude, as the VS is decided by the altitude input?

What i was experiencing latly was, that on actice APPR mode the aircraft is mostly doing what it wants. Once it flew a good glideslope but i had to take over and G/A cuz it came in way to high on appr. Or another time it turned away from the runway curse just before minimums whrer i would have taken over.( i always activate it at the moment altitute and course are approx. The same to prevent it from taking evasive actions) these are the only problems i experienced with A/P or APPR Mode.

Well I haven’t had the same kind of problem as you but sometimes when I’m on a flight in the A321 and I engage the autopilot the plane goes into severe oscillations. This happened when I was going well within the aircrafts speed limit when there wasn’t much turbulence. This hasn’t happened with any other aircraft.

I have this problem with the a319 just after takeoff it is annoying and also when when I reach 30000 feet I just drop

Perhaps practice Landings so you don’t need AP…

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Part of my final approach checklist is to set the trim (with autopilot still on) so that the little pink bar next to the trim % disappears. This is so that if I need to disconnect the autopilot, the pitch doesn’t go wild.

Other than that, in such circumstances, I am always ready at the drop of a hat to hit the “A/P” button, disconnect the autopilot and hand fly the airplane on the go around.

In the real world jets I flew (Lears, Citations), we had a “TOGA” button - which would reposition the flight director - but nothing like that exists in IF, so hand flying the airplane using a specified pitch and power setting is whats needed to successfully do a go around.

My personal suggestion for Go Arounds while on short final in IF (take it or leave it:) -

  1. Disconnect AP (ensure trim is set while AP on so no pink bar shows)
  2. Pitch first (10-12 degrees)
  3. Apply takeoff power (98% N1)
  4. Positive Rate - gear up
  5. Retract one notch of flap
  6. Accelerate to somewhere around V2+30 (180 kts maybe?), retract flaps
  7. Fly missed approach course (follow ATC instruction)