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Trouble landing 777-200LR

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Trouble landing 777-200LR

Postby Pancho » Tue Jul 14, 2020 11:56 pm

I've tried about everything possible landing the B777 using ILS. Every single time, when it gets down to about 20-10 fts. from landing, it decides to bank to the right, like a tip stall.
I've tried multiple IAS settings from 130 to 170 with same results.
The total weight is around 354,000 lbs
The runway is an ILS cat. III (KEWR 04R)
Thank you
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Re: Trouble landing 777-200LR

Postby tdammers » Wed Jul 15, 2020 2:43 pm

Sounds like it's stalling indeed. If you're coming in too slow, you'll be flying in a nose-high attitude, and then when the autoland initiates the flare, it'll pull up even further, and that would create a stall. And because the 777 uses YASim, that stall is modelled as a rather harsh and unrecoverable one-sided wing drop.

At 354,000 lbs, your Vref for flaps 30 should be around 122 KIAS or so; add 5 knots for the final approach speed to get a little headroom for corrections. For lower flap settings, add 10 knots for flaps 25, 20 knots for flaps 20 and 15, 40 knots for flaps 10, 60 knots for flaps 5, and 80 knots for flaps up. So if you're trying to land with flaps up, that would be 202 KIAS; for flaps 5, Vref would be 182 - still way above your 130-170 range. Realistically, when you're this light, you don't need to use full flaps, but you still want to land with flaps 20 or so, which should put you around 142 KIAS for the final approach and landing.

If you're already using enough flaps, then I'm out of ideas...
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Re: Trouble landing 777-200LR

Postby tdammers » Wed Jul 15, 2020 3:12 pm

Just to check, I did a quick flight with the 777-200LR at EHAM. Takeoff from 18C, short round around the airport at 210 KIAS, then ILS approach and landing on 18R. Landing weight around 354,000 lbs, flaps 30, final approach speed 120 KIAS (so even slower than I said earlier), autoland, autobrakes 3. Absolute butter. I recommend keeping a close watch on the airspeed tape on the PFD, and setting flaps such that you stay outside the stick shaker markers and barber poles.
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Re: Trouble landing 777-200LR

Postby Pancho » Wed Jul 15, 2020 7:51 pm

Thank you, I'll try your suggestions.
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Re: Trouble landing 777-200LR

Postby Pancho » Thu Jul 16, 2020 7:07 pm

Well, I was able to replicate your EHAM flight with great success, then I tried the same parameters on a different runway, and the problem shows up again.
Here's the links to the two flights.

EHAM
https://www.youtube.com/watch?v=84HUSAyzWIE

KEWR
https://www.youtube.com/watch?v=iy8jGU45i7o
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Re: Trouble landing 777-200LR

Postby Pancho » Fri Jul 17, 2020 12:11 am

I don't give up, but it's interesting, so far it works fine in three airports, EHAM, KATL and KDFW, and it fails in KEWR and KLAX, I'll continue looking at videos to see if I find a clue.
Thank you to those that follow this thread.
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Re: Trouble landing 777-200LR

Postby Pancho » Fri Jul 17, 2020 12:58 am

I've found something on one of the failed landings, perhaps someone could take a look and let me know, your opinion.
Towards the middle of the video, I circled what doesn't look right to me on the right flap, but at the end, after a brief stall, it corrects itself
https://www.youtube.com/watch?v=gXGlEhTvMoU
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Re: Trouble landing 777-200LR

Postby WoodSTokk » Fri Jul 17, 2020 1:10 am

We can see in the second movie, that the aileron on the right side (supported from the spoilers) react.
I assume you try autoland and this feature use the ILS.
Maybe the LOC beam isnt fully correct.
It looks like a autopilot follow a radial on a VOR, but the aircraft is not fully on the radial and the VOR comes closer and closer.
Many autopilots in FG starts with erratic inputs if they come very close to the VOR, because the angular change become greater if you come closer.

EDIT:
In case of KLAX the ILS for rwy 07R has the same frequency as rwy 25L.
FG simulate the ILS beam in this case down to the threshold.
You can see this on the map. If you pass the threshold, the ILS beam turns from cyan to blue.
This means no reception. Without reception, the autopilot have no meaning where the rwy is and what altitude you are flying.
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Re: Trouble landing 777-200LR

Postby Pancho » Fri Jul 17, 2020 1:36 pm

Thank you for your valuable information. Every bit helps people like me that just got into FlightGear sim.
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