Some tests regarding the "broken B77W approach speed"

[FlightGT]

So there’s a support topic discussing the B77W approach speed and pitch angle too low. But the discussion is lack of convincing comparison. I did some comparison between PC simulator and IRL operations, and I believe the approach speed is too low as well.

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1. IF VS Prepar3D - PMDG B77W

The easiest way to compare is to find a more professional simulator on PC. I choose the well-known PMDG model in this comparison. This test is based on this video: PMDG Japan Airlines 777-300ER from Tokyo to Hong Kong | VATSIM - YouTube

At 40:25 the FMC’s in the approach ref page, showing the Vref for flaps 30 is 138kt. In normal operations, the Vapp will be Vref+5, in this case 143kt, which he followed later. We can also read the gross weight when approaching: 214.7t, or 214,700kg.

At 49:39, the aircraft’s on short final, maintaining Vapp=143kt, and a pitch angle of 1.25 degrees. The PFD shows the aircraft is descending 700ft per minute.

When we put all those data together (214.7t load, Vapp=143kt, F30, pitch 1.25 degrees) in IF:

The aircraft is only descending -300ft per minute. In very short time I’m well above the glideslope.
In order to be on the glide, I have to maintain a negative pitch:

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2. IF VS IRL

Some may argue that simulators all have flaws and errors. So here’s a comparison to real life operation. This test is based on this video: TOKYO HANEDA 22 | BOEING 777 LANDING 4K - YouTube

We can read from the cockpit placard that the registration is F-GZND, a B77W of Air France.

At 2:34, The instrument shows Flaps 30 (the bar on the left, same as in IF), the Vapp around 145kt, pitching up 0.5-1 degree, and descending 750ft per minute.

Since there’s lack of weight information, I’ll use the max landing weight 251,290kg to achieve highest Vapp as possible.

They also mentioned wind information:

When these conditions are applied in IF:

The difference still exists, though not as obvious as previous one. The aircraft is able to follow glideslope at correct v-speed, but only with zero pitch. If following 0.5-1 degree pitch as in the video, the aircraft will be above GS. Considering this is the max landing weight, which won’t often be this case normally, the difference will only gets bigger.

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I’ve made several comparison with other variants of B777 as well, but the B77W differs most from IRL. I’m open to discussions and opinions, and if many agree with this, I hope the devs can investigate. After all I’ve never seen a video showing a B77W approaching with negative pitch…Unless I missed something.

[BennyBoy_Alpha]

I love topics like these…full of data comparisons (which I love)

Very interesting though…I will say that the 777 on approach does feel a little slow.

For example this morning I was landing in Dubai - I was at 5% load because I had no pax or cargo and my approach speed with Flaps 30 was 117kts IAS?!?! I’d have expected it to be around 10-15kts faster than that.

[MxP]

I agree. While I am no real pilot, is is clear that the B777 handles very different compared to other (widebody) aircraft. Other recent models such as the A220 and A330 handle better and don’t have that problem.

[NewsDude]

Gonna be completely honest, I never noticed this! I didn’t realize that the 777 had inaccurate approach speeds. Hopefully this is something which can be fixed!

[MathiasG]

Always felt that it is something wrong with the approach speed on the 777, I really hope we will get a fix to this to make the 777 a little bit better to fly, or a clear answer to why this has happened.

[adit]

@FlightGT

The easiest way to compare is to find a more professional simulator on PC. I choose the well-known PMDG model

I disagree with the logic of this. To make a comparison with such a hypothetical standard (a platform for which you can find abundant searchable criticism) as being a good substitute for unavailable real world data, is not reasonable. If you have reliable real world, that might mean something.

This is not a reliable source of data.

[FlightGT]

That’s why I also have real life comparison.

[adit]

I mean in terms of test flight numbers and/or real-world pilot’s testimony that relates specifically to all relevant conditions in the area of flight performance being considered.

I made measurements in the other topic about the range of AoA’s. So that characterizes the question in terms of data, to either be substantiated or refuted.

You’d have to have a good enough source of data that you could directly compare with something like this set of AoA data, with robust credentials for real world reliability.

As previously stated:

@schyllberg

This aircraft’s physics was developed with the feedback from no less than 2 real world 777 pilots.

[adit]

Sorry, I was re-reading your post and I realized I needed to spend more time with it. It is interesting and well put together. And I missed that you included a real approach (I thought it was a simulation). Still reading and thinking…

[FlightGT]

I’m also finding more data as well, and I’ve found this, from Qatar Airways B777 FCOM:

The pitch attitude to maintain, engine thrust and Vapp. It’s used during airspeed unreliable and turbulence penetrating. You can see the pitch is always above 1°.

The Vref data is also provided.

Doc link

[adit]

That’s a good find! I was looking for (but failed) to find something similar.

[Maxim]

@adit

I mean in terms of test flight numbers and/or real-world pilot’s testimony that relates specifically to all relevant conditions in the area of flight performance being considered.

I made measurements in the other topic about the range of AoA’s. So that characterizes the question in terms of data, to either be substantiated or refuted.

You’d have to have a good enough source of data that you could directly compare with something like this set of AoA data, with robust credentials for real world reliability.

The PMDG B777 is the most comprehensive replication of the B777 available on any flight simulator platform at the moment (short of a Level D simulator, obviously). I think using its data and performance to compare to Infinite Flight’s B77W, as @FlightGT has done, is quite fair (even if no real-world data was included in the post). If Infinite Flight can replicate even a tenth of PMDG’s behaviour (in terms of aircraft performance), it would be a huge achievement.

The best way, of course, to check the handling and performance of the B77W in Infinite Flight is to fly the same route, under the same conditions in real life. This is practically impossible. The next best thing in terms of accessibility (including cost) is the PMDG 77W.

Also, for what it’s worth, real-world pilot testimony is highly subjective and not as objective as one might think. Sure - it’s better than John Doe commenting on the performance of an A320 during a stall in alternate law (whereby John Doe’s source is his ‘feelings’), but real-world pilots constantly disagree about aircraft handling in the flight simulation community (see Fenix Airbus A320/Flight Sim Labs A320).

To be quite blunt (and a bit off-topic) - the vast majority (I would assume in the 99th percentile) of Infinite Flight users would not notice anything even if the performance of the B77W was changed to perfectly replicate the real aircraft (this is not the case for more ‘serious’ flight simulation enthusiasts (who are all exclusively on desktop)). I think the return on investment (time, effort, money) for Infinite Flight spending countless hours tweaking the performance to perfect it is very very low (if not zero). Mobile flight simulation enthusiasts are simply not as sensitive to such inaccuracies compared to desktop simulator users - the curve of diminishing returns on such inaccuracies on a mobile platform is much steeper. My personal take is at the moment, it’s ‘good enough’ - after all, this is the first serious discussion about the B77W’s performance and handling in two years.

[TheGlobalAviator]

@Maxim

To be quite blunt (and a bit off-topic) - the vast majority (I would assume in the 99th percentile) of Infinite Flight users would not notice anything even if the performance of the B77W was changed to perfectly replicate the real aircraft

To be completely fair, nothing, including PC simulators that require addons which can vary in terms of realism, can perfectly reproduce and replicate the exact handling characteristics of an aircraft in real life. The most we can do is tweak the physics that it is as close to real life as possible.

Moreover, I believe that, even to regular IF users or those who frequently fly the B77W, the hypothetical fix would in fact be noticeable; we’re talking maybe a 7-10-knot difference with the same weather conditions, flaps and landing weight to maintain the same pitch (as in real life) between the -300ER in IF and the actual aircraft.
While I said it’s impossible for IF to be 100% realistic, a simple comparison with a simulator that is closer (not completely) to the real world indicates that some work can indeed be done to improve the situation, even if it is not of a high priority - for now.

[adit]

@Maxim

The PMDG B777 is the most comprehensive replication of the B777 available on any flight simulator platform at the moment

Even assuming that’s the popular consensus of opinion, it still doesn’t relax the need to separately verify against real world data (assuming one wants to safeguard against potential sources of doubt whether due to exuberance, marketing or other biases).

As one of several different references of insight, it’s fine. But there is a risk of bias error in using another product as a standard, without checking that standard against more fundamental information. Manufacturer’s data removes (most of the) potential bias risk.

@Maxim

real-world pilot testimony is highly subjective and not as objective as one might think

Yes, but such testimony forms an unavoidably necessary reference, to integrate and cross checked against other sources of information.

@Maxim

real-world pilots constantly disagree about aircraft handling in the flight simulation community

That makes sense. And usually there is insightful info revealed in disagreement.

@Maxim

this is not the case for more ‘serious’ flight simulation enthusiasts

I consider myself a serious flight simulation enthusiast. And I only use IF.

For sure there is a trap of diminishing returns of usefulness in attempting to capture increasingly precise detail from the real world.

So while I often try to be precise in the inquiry to understand the question thoroughly, my conclusions usually go to what’s the best fit, all things considered.

I learned from the OP’s presentation. My biggest takeaway is to be happy the pitch is indeed very flat on approach with the 77W. And of course the AoA numbers are behaving properly in terms of response to load, speed and flap settings.

[adit]

@TheGlobalAviator

nothing, including PC simulators that require addons which can vary in terms of realism, can perfectly reproduce and replicate the exact handling characteristics of an aircraft in real life

It’s too easy to lose the significance of that.

[Boeing797]

do the other variants have this issue?

[FlightGT]

They do, but not as severe as the 77W.

I feel that 77F is the most accurate, can maintain 145kt approach with positive pitch.

[BurritoLeo]

Definitely agree the B77F for sure has the best handling of them.

[IFVN-TaiXipo]

Will they work on this? Since this could effect to our experience when flying the 77W. I feel the same when flying the 77W, it’s too powerful or it’s too light. Even with takeoff, you only need 70% thrust and you can rotate easily. I really don’t think that 77W can be lighter than 77F since 77W is bigger and heavier. Other variants of 777 are good, but 77W is hard to say (mostly we are complaining about the speed of this aircraft)

[sfahyaviation]

Historically, probably not. I doubt anything will be done about this to be honest.