V Alpha prot highlevel A320
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V Alpha prot highlevel A320
Hi,
scenario: you enter a holding in 18000ft. The fmgc says: set hld speed. So you push the button and he flies managed. Reaching the turn in the holding the va prot band comes up. So what speed would the airbus fly and what would happen if he flies the speed? Protections coming on?
thanks!
sw
scenario: you enter a holding in 18000ft. The fmgc says: set hld speed. So you push the button and he flies managed. Reaching the turn in the holding the va prot band comes up. So what speed would the airbus fly and what would happen if he flies the speed? Protections coming on?
thanks!
sw
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With autopilot engaged, the aircraft will command pitch down as a last resort to remain above VLS.
Someone can correct me but this is what I have observed and read in the FCOM, but this was during descent.
Someone can correct me but this is what I have observed and read in the FCOM, but this was during descent.
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For managed speed/Mach, the lowest target is VLS, and the highest target is: ‐ VMAX in the case VMAX is equal to VFE, or ‐ VMAX - 5 kt in the case VMAX is equal to VMO/MMO.
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VLS doesn't change with G i e. in turn. It's the alpha prot moves up. If holding speed is correct for the altitude there should be no problem. AP bank has limit. If speed drop below alpha prot AP will trip and aircraft will maintain alpha prot unless stick is pushed to unlatch the speed. Beyond •63M there's no alpha floor.
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VLS doesn't change with G i e. in turn. It's the alpha prot moves up. If holding speed is correct for the altitude there should be no problem. AP bank has limit. If speed drop below alpha prot AP will trip and aircraft will maintain alpha prot unless stick is pushed to unlatch the speed. Beyond •63M there's no alpha floor.
In clean configuration Vls=1.28VS so you should be fine with up to 52° of bank, alpha prot coming in before that anyway.
Though during my type rating the instructor definitely managed (one way or another) to make us trigger alpha floor after starting a turn for an approach with speed managed at green dot.
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Autopilot should limit load factor by reducing bank angle before ending up in alpha protection. You have a surprisingly small margin at green dot and I’ve triggered a stall warning in the simulator during a level turn with 30 degrees angle of bank (alternate law obviously). “New underwear, please”.
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My bad I was wrong. After checking FCOM again if I understood correctly Vls being based on VS (actually vs1g so non g dependant) it won't change with the load factor.
In clean configuration Vls=1.28VS so you should be fine with up to 52° of bank, alpha prot coming in before that anyway.
Though during my type rating the instructor definitely managed (one way or another) to make us trigger alpha floor after starting a turn for an approach with speed managed at green dot.
In clean configuration Vls=1.28VS so you should be fine with up to 52° of bank, alpha prot coming in before that anyway.
Though during my type rating the instructor definitely managed (one way or another) to make us trigger alpha floor after starting a turn for an approach with speed managed at green dot.
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Well the AC didn’t reduce the bank angle. And managed speed was the target which was green dot. So we agree: A320 in a high alt pattern can’t fly managed speed?
Last edited by Speedwinner; 14th Jul 2023 at 04:21.