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A320 - when does ac activate app mode ?

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A320 - when does ac activate app mode ?

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Old 8th Dec 2015, 07:35
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Default speed is 250kts below 10 000 and that's what it will shoot for with the speed managed and approach phase not activated. Flap limits mean nothing.
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Old 9th Dec 2015, 07:57
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Systems Manual section 22-30 (Managed Speed/Mach Target)

If the managed speed/Mach target is set above VMAX (VFE, VMO, MMO), the FMGS automatically limits the speed to VMAX
Unless I'm misreading that completely, if APP Phase is not activated, and you push for managed speed, the AT should limit the speed to Vfe if flaps are extended.

I'm new on type. Am I missing something?
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Old 9th Dec 2015, 11:49
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CA: Almost correct I think. The FMGS will limit the speed to Vmax, but the AT will agressively chase the cca 30kt faster target and will eventually overshoot. Never had the chance to test the feature properly myself, on the several occurences so far as a crew we were fast enough with the corrective actions (touch wood).

In a similar fashion should a flap/slat overspeed be imminent after takeoff / GA, selecting flaps/slats lever up one step will remove the barber pole from the speedtape at once, however the overspeed may still occur while devices are in transit. FDM/FOQA will have a record of the exceedance so PIC better make sure the techlog entry is there as it should.

Last edited by FlightDetent; 9th Dec 2015 at 19:45. Reason: Improved clarity, hopefully. :)
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Old 9th Dec 2015, 12:26
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I managed the speed on final one day without having the approach phase activated, the engines instantly powered up and we started accelerating. The Master Warning went off as flap limiting was exceeded before the head of the training department who was in the left hand seat pulled the speed knob. I was rewarded with a large number of extra sectors added to my program.

Also worth noting that if you are on an arrival and a speed constraint has activated below 10 000', say 220kts, if you go into heading mode the speed will increase to the default of 250/10 000. Worth keeping a look out for.
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Old 9th Dec 2015, 15:15
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That makes sense now. Appreciate it. Thanks for the tip as well!
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Old 11th Dec 2015, 14:59
  #26 (permalink)  
 
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That doesn't work if ATC have given you a speed(s) for sequencing. Happens on almost every approach to my base.

In fact, as soon as London TMA starts giving us speeds, we go selected speed and then activate the approach.
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