Final App mode strangeness

[b3lt3r]

Multiple times now I have had severe issues on approach after manually selecting final approach on TO/APPR slightly early to get speed down to green dot early. Basically it initially behaves as expected and then suddenly all my speed bleeds off, shaker goes mad and I fight to get it into a controlled regime again. 

Yesterday I managed to get a video of the events and I believe it should show all the settings immediately prior to the event as I made sure to look at all the panels. I need to edit the video down to the relevant stage, once I have do you want to see it? If you do then let me know where to post it and any limits.

This at least the 3rd consecutive approach where this happened after engaging FA. Immediately after that flight I did another into EGNT without selecting FA and it flew exactly as all my other flights had before I started selecting it.

Cheers

[b3lt3r]

Edited down to c. 54mb.

Having re-watched several times I see that as the turn to final is happening with slats 15, the speed window *briefly* opens and the bug is set at 127 (vapp) - the window then shuts again and that speed is targeted but we're still slats only hence the stall.

You can also see, when I disengage autothrottle I have a blinking "thrust L" on the fma and the levers are jerking back and forth when I try to get the thrust off. The levers are calibrated normally and work correctly in the usual regime. I think I recovered by cycling auto-thrust a couple of times. Eventually got back to stable manual flight and completed the approach by hand.

[AlexArt75]

Same problem. Several times already. And when AT is turned off, it turns on itself again and does not allow manual thrust operation.

[JoshF]

Hi, a video would be very useful, if you can upload it to a hosting service (dropbox, Google Drive etc) so we can take a look. THRUST L is somewhat equivalent to the modern Airbus "A.FLOOR" mode, whereby the AT will forcefully engage to prevent a stall event

[b3lt3r]

I will upload early tomorrow when I'm back at my PC with it. 

Rgds

[AlexArt75]

3 hours ago, lowpolybutt said:

THRUST L is somewhat equivalent to the modern Airbus "A.FLOOR" mode, whereby the AT will forcefully engage to prevent a stall event

Thanks, that's what I thought. But the documentation for the model is completely insufficient to understand much. There are real documents, but not all of them have been read yet

[SeanDarren]

Glad I found this thread as I have been having the exact same issue. I posted this on the inibuilds discord as well. This also has happened on my last 2 flights. In both scenarios I was at flaps 15/15 flying at about 160kts on Localizer and ready to intercept the G/S. When I select flaps 20/20  in order to prepare to select my Approach speed, all of a sudden the nose pitches up violently and I immediately enter a stall as a result of speed plummeting. What is causing this? Because last time I checked I can have flaps 30/40 as fast as 180kts. At the the time I had 160kts and was well out of the red zone. I have a strong feeling this is because I manually selected Final Approach in the MCDU. I am very sure this is a bug despite what the admins on discord are saying. I was not close to stalling and there is no logical reason for the plane to pitch up so violently while bleeding speed at that rate. 

[b3lt3r]

Edited down to c. 54mb.

Having re-watched several times I see that as the turn to final is happening with slats 15, the speed window *briefly* opens and the bug is set at 127 (vapp) - the window then shuts again and that speed is targeted but we're still slats only hence the stall.

You can also see, when I disengage autothrottle I have a blinking "thrust L" on the fma and the levers are jerking back and forth when I try to get the thrust off. The levers are calibrated normally and work correctly in the usual regime. I think I recovered by cycling auto-thrust a couple of times. Eventually got back to stable manual flight and completed the approach by hand.

I haven't used my Gdrive in years but here's a link I believe should work. https://drive.google.com/drive/folders/17wUCBy6jePKxNRcp-3Mmkrm19pNTISvY?usp=sharing

It starts downwind for EGKK26L shortly after I have confirmed Final Approach Mode and it has slowed for green dot.

[Deleted Account]

The video shows exactly the behaviour i outlined in a similar situation on discord. You were too slow for your flap/slat configuration and due to the turn the stall speed got even higher, which lead to a stall / the stall protection kicking in.

THRUST L activates (comparable with A. FLOOR on A32x aircraft), so TOGA power is set and because of the incoming thrust the aircraft pitches up.

If you´re on Discord as well, here is the link to that post 🙂https://discord.com/channels/535246634448191499/1043300012114853889

 

 

To solve this, just give the aircraft some more flaps and it shouldn´t happen 🙂

[b3lt3r]

Hi.

I can't access the Discord, it keeps telling me I'm in a strange place with no text channels?

Regarding the slowness - the thing is that I did not command the slow speed (127) - I was at green dot and then set slats 15 when you can see the S appear on the tape with the speed window shut. I glance to the left and when I turn my head back, the window is open at 127 - slats are still 15/0.  (I missed the open window because I thought it should happen at 15/15 - my bad).

It then decelerates to the S and the instant it gets there, the window closes again and it continues to decelerate till the point the shaker goes off. 

I should have paid attention more but I don't understand why the window opens itself - both at all and if it is going to why at VAPP rather than the current speed?

 

[b3lt3r]

[Deleted Account]

The 127kt got commanded by final app mode engaging I´d assume 🙂

 

To see all channels on the discord, you´ll have to react to the message in #welcome 🙂

[b3lt3r]

Lol. I'd love to react to a welcome message but I see nothing - literally can't get past that message 🙂

Re -127kt - when FA mode is engaged it appears to do what I have read it does and target green dot at around 190kts which is way higher. At slats only the S appears and the window is still closed. What I don't get is the uncommanded window open to show 127 and then close up again but still set at 127 which doesn't match what I've seen on any streams or heard mentioned. Thing is with the window closed I don't have access so I can't move the bug up to S?

I dug out a PIA FCOM and attached the parts which looked relevant - doesn't explain the open/close of the window (to my brain) 🙂

I guess see what happens with the fix and I'll just make sure the window is held open manually if needed.