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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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Re: Trouble landing 777-200LR

Postby flyer » Sat Aug 29, 2020 6:20 pm

@Pancho, I am starting out with FlightGear and enjoy flying the 777-200.

Could you post a video (or share a link) for a "perfect" landing with the 777-200? The cockpit view with the HUD would be especially helpful.
I am not sure if I am landing to book, though my basic strategy is to try and land as slow as possible, without engines and just glide in.
I like to land just above the 10 line on HUD so I have a nice smooth landing. I noticed that in one of your videos you had quite a bit of nose
up on landing. My landings with almost a flat touch down after the roundout have a very nice feel.

The flaps have given me some confusion lately. What flap position is flush with the air flow? I had thought that Flaps down was the right direction,
though I am not as sure now. Flaps 30 .. 25 .. 20 .. 15 .. 5 . Flaps 30 is in the down position on the controls. Is this also flaps down on the plane?
When I clicked through the flaps, clicking up (i.e. 30--> 25 -> 15 ... ) seemed to break the air flow.

Also if possible could you have the glide path displayed? (BTW, how do you instruct FlightGear to show a glide path? Often FlightGear will
not show the glide. Is there a way to force it for a specific runway and heading?)
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Re: Trouble landing 777-200LR

Postby Johan G » Sat Aug 29, 2020 9:54 pm

Welcome to the forum, flyer! :D

A few quick questions:

  1. What is your landing airspeed?
  2. What is your reference airspeed, V_Ref, for your landing weight?
  3. Have you figured out that you control airspeed with pitch and vertical speed with the throttle, not the other way around?
Low-level flying — It's all fun and games till someone looses an engine. (Paraphrased from a YouTube video)
Improving the Dassault Mirage F1 (Wiki, Forum, GitLab. Work in slow progress)
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Re: Trouble landing 777-200LR

Postby flyer » Sun Aug 30, 2020 12:36 am

Thank you for the warm welcome Johan G!
I suppose with COVID and the near grounding of the world's inventory of aircraft there might be a few pilots on forum
polishing up on some of the finer points of flying.

FlightGear is really great!
I have had a lot of fun with it over the last few months.


1. I have preprogrammed 150 knts into the locate aircraft in space tab.
I was not sure what the real landing speed should be so I went with 150.
I have not been able to figure out what the actual 777-200 landing speed should be.
The above comments talk about a base 122 and then add in flaps.

Before when I was doing free landings (that is setting my own landing speed)
I tried to move it down as slow as I could on touch-down perhaps as low as 110.
I have noticed that rounding out and just flying level to the runway can be one
way of braking without actually landing. My feeling is that if I am flying over the runway
about 10-20 feet in the air at about 110-120, there will not be a sudden stall. A stall if it were to happen
would be more that I could not pull up. Pulling up on landing is a tactic that I have used to slow down.

Landing with the least amount of kinetic energy is what I like doing. Basically a UFO landing. No forward
momentum. Just before landing pull up and drain out the remaining speed and basically plunk down.
This can work with the Cesna, though not so much the 777.

Reducing landing speed greatly helps with fighting through the turbulence that can happen on landing.
This typically happens when runway landing speeds are still over 70. After you move below about 70,
everything is nice and smooth.

I have also discovered the reverse thrusters and they are helpful, though it would be nice if
throttling up the reverse thrusters was not so low.

I am not totally sure whether the 777 has anything else.
There are flaps, yes. Not sure about spoliers, or air brakes.


2. No idea what Vref means.
I just start up the 777-200 and takeoff.


3. Yes, I read that somewhere on the forum or the manual.
I have been mostly focused on takeoff and landing, so I have not really
seen the point of that-- pitch air speed, throttle vertical speed?

On take-off it is mostly about powering up the engines as much as possible.
The warning pops up if you try to use too much throttle on takeoff.
So there can be a struggle at the start to have enough power especially when the V1 is supposed to be
~120. I am not sure if in real life I would blow out the tires if I tried to take-off at 150+,
though more speed on take off makes things much easier. In my early attempts at takeoff
I was always have problems with stalling.

With my landings now the autopilot is controlling the throttle, so I do not even have to worry about it.
All that I have ton do now for landing is concentrate on keeping the nose at a good glide angle. The autopilot
does all the throttle control; it is very convenient.

Before I had quite a bit of trouble landing, though this was because I would just be out flying around and
happen upon an airport and then try and set myself for landing-- mostly I did not have enough set up room.
These landings usually did not go well; often I would have to fly over the runway because I had too much height and too
much speed.

With the locate aircraft in space tab I can have a standard setup to land at airports. It's great!
If I set a good distance and a good height, then about all that is left is to glide down. It makes landing much
easier. I am now developing a fair amount of skill with manual landings.

I have largely learned by trial and error, though now I have very nice and smooth takeoffs.
Typically, I now like to wait for a fair amount of speed (>150 knts) before liftoff.
Before when I pulled up on the V1 command I mostly wound up stalling out most of the time.
I was very unsure why I was having so much trouble: How tough can it be to launch a plane?

Now with good speed and revving the engine towards maximum there is no problems with warnings or cautions.

My landings are finally improving quite a bit now.
I am getting to the point that I am landing near the center line.
This is a great improvement for me: Until recently I was typically very pleased with myself if I even managed
to touch the runway on landing. Now it usually all runway, and all tires on pavement.

Some of my current frustrations are: 1. the autopilot.
When I set the location in air tab and then start flying, the autopilot takes over the throttle control.
I do not remember it doing this before. It can be actually quite convenient with the autopilot having my back.
The problem happens if I need to reset on landing. If I land in one smooth motion, then the autopilot does
not kick in and fight against my landing. It is just when I need to pull up and then go down again to land where there is a problem.
As soon as I pull up and lose airspeed the autopilot ups the throttle and then when I try to push down again
I have to fight the throttle. It is fairly annoying. I suppose there must be a button to disengage the autopilot.

2. hitting enter pauses flight
For some odd reason hitting enter now pauses flight. I though p paused flight? Now enter also pauses flight.
I have finally realized how helpful enter and 0 can be to help me land. If I combine enter/0 and yoke I can
get quite good lateral control on landing. Without enter it is much more difficult.

I really enjoy landing at a nice slow speed on the level with the runway without recoil. It doesn't even feel like
landing. I am not sure what all this nose up and then nose down is about. If I can land right above the 10 line
on the HUD display, then I do not need to do any of that. I suppose the big rule here is to land on the back tires
and not the front. Landing on the front tire would probably wreck it and probably give you very poor steering
control on landing.

Greatly enjoy flying the 777 with FlightGear.
Sorry that I have not paid attention to Air Traffic Control yet.
Not sure how that works either.

Anyone who wants to chime in on any of the points in this, post please do!
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Re: Trouble landing 777-200LR

Postby Pancho » Mon Aug 31, 2020 12:46 pm

Flyer

This is a landing video to a flight from MDSD (Santo Domingo) to TJSJ (Sab Juan, PR.)

I'm doing a fully AP ILS landing, just control the aircraft on the runway after landing, and set the reverse thruster for a short while.

I'm just a beginner, and the B777 is the only aircraft I can fly

Hope it helps
[url]
https://www.youtube.com/watch?v=hSI8x2fjubw[/url]
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Re: Trouble landing 777-200LR

Postby flyer » Tue Sep 01, 2020 6:44 am

Thank you very much for replying Pancho!
Sorry for invading your thread, though I am having such a great time with FlightGear.
I am surprised how realistic the program is.

Could you show that landing that you posted again this time with the HUD up and from the cockpit
view. That landing that you showed was remarkably smooth; smoother than perhaps my best landing
so far. I would like to see the hud setup that they used. They seemed to be on a nice smooth and
even descent and flight path the whole way done. With manual landing you often need to make some
adjustments along the way.
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Re: Trouble landing 777-200LR

Postby tdammers » Tue Sep 01, 2020 11:25 am

Landing speeds: with a large airliner like the 777, the landing reference speed (Vref) depends hugely on weight. Between operating empty and max landing weight, there is a 50% difference, and clearly a landing speed that works well for a 140-ton aircraft is going to have you drop out of the sky when you weigh 210 tons; and conversely, the right landing weight at 210 tons is going to make your float or nosewheel-strike when you're landing empty.

So what you need to do is find a resource for those landing speeds. Real-life pilots get a preliminary calculation from their dispatchers, who use dedicated software to calculate all the landing parameters; but it can also be done using tables from the FCOM, and in most modern airliners, the FMS can do the calculation as well.

The same goes for the takeoff. Here, the crucial speeds are V1, Vr, and V2. V1 is the "safe rejection speed": until V1 is reached, the aircraft can be brought to a full stop safely within the available remaining takeoff distance; once you're faster than V1, rejecting the takeoff may lead to an accident, and you are committed to the takeoff except for very severe problems (like losing both engines, loss of control, or a fire). Vr is the "rotation speed": this is the ideal speed to pull up the nose to initiate the liftoff. V2 is the "safe single-engine climb speed": after liftoff, your goal is to attain this speed ASAP, so that loss of one engine does not compromise the aircraft's ability to meet the minimum climb requirements for this takeoff.

In the FG 777, all these speeds are calculated automatically, and displayed on the PFD speed tape; Vref is shown as REF.

Then, procedures.

For the takeoff: Configure autobrake (RTO, "rejected takeoff"), flaps and trim, line up, arm A/T (the flip switches next to the speed selection on the glareshield panel), and rotate the speed selector to a suitable departure speed - at least V2, but typically something like 200-250 knots. This is to make sure that when the autothrottle kicks in, it keeps setting takeoff thrust at least until you have achieved V2. Set a suitable lateral mode on the autopilot: LNAV if you're flying an FMS flight plan, otherwise probably HDG. Revv up the engines to 40%, wait until they stabilize, then set takeoff thrust. At the "rotate" callout, pitch up; watch the vertical speed, as soon as it's consistently positive for 1 second, gear up. Maintain centerline and an attitude that keeps you speeding up to V2. Engage autopilot a couple hundred feet AGL, or later if you prefer hand-flying the aircraft a bit longer.

For the landing: Use the initial approach segment to slow down to your initial approach speed; typically, this would be your "minimum clean" speed (the slowest speed you can safely fly with no flaps deployed), something around 200-220 knots usually. The approach procedure will have you descend to a suitable ILS intercept altitude, typically about 2000-3000 ft AGL. Make sure you have the correct ILS frequency set, that the ground spoilers are armed, and that you have selected a suitable autobrake setting. As you turn onto your intercept heading, slow down to your initial approach speed (160-180 knots should work fine), and set flaps accordingly, and arm APP on the autopilot. Watch the aircraft intercept first the localizer, and then the glideslope. Once established on the glideslope, deploy landing gear. As you approach the outer marker (5 miles out), slow down to final approach speed (usually Vref + 10 knots), and deploy landing flaps.

Now you have the choice between autoland and landing manually.

For autoland, I believe all you have to do is watch the aircraft fly itself down to minimums, flare, align, retard, and touch down. Once on the ground, select reversers and set reverse thrust, verify that the ground spoilers and brakes are deploying, and use rudder to maintain centerline. At 60 knots, retard the throttles to reverse idle, and take over manual braking (the autobrakes should automatically disengage as soon as you touch the brakes). At 40 knots ground speed, disable thrust reversers; you may now take a high-speed exit while slowing down to taxi speed, or slow down further on the runway before taking a sharp exit. While vacating the runway, retract flaps, and switch off landing lights.

For a manual landing, the procedure is the same, except you disengage autopilot and autothrottle at some point during the approach - 1000 ft AGL is a good moment, but you can do it earlier if you want. Use pitch to control speed, throttle to control descent rate; keep airspeed at Vref + 10, and sink rate such that you stay on the ILS glideslope. Once you have a good visual of the runway, transition to a visual approach, using PAPI lights as your descent reference (two red, two white means you're on the glideslope). You should cross the runway threshold some 100-200 ft AGL, with some residual thrust on the engines (say 40-60% or so), a slight nose-up attitude, and a sink rate around 1000 fpm or so. At a suitable altitude (typically 50-100 ft AGL), retard the throttles; use pitch to arrest the descent - down to zero if you want a "butter" landing, or keep a little bit of sink rate if you want a safer, firmer landing. The aircraft should now just sink into the runway, main landing gear first. From here, the procedure is the same as above.
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