B777 visual segment
 

Hello,

I am currently working on my 777 type rating and I am wondering about the B777 cutoff angle.
For two reasons : how to evaluate the visual segment in an LVO takeoff ? Usually, we will count the number of lights available and multiply the number of visible light intervals by its 15m length. But then we need to add the cockpit cutoff distance. What is the cockpit cutoff distance on this plane ?

Then, about the landing phase, when we follow a PAPI, the main gear is bound to hit the ground, without flare, at around 100-130m after threshold.
So the problem is more often short landing than long landing. But if you do manage to perform a doubtfully long landing, how can you evaluate ?
From the sim sessions we've done, it seems like when we see the xxxm meter marks disappear and touchdown right at this moment, the touchdown distance is approximately 100-150 (??) meters before the mark.
What is the value of the cutoff angle ? What is the cutoff distance if we have the main gear on ground, 5° of pitch ?

The formula is rather easy, take the pilot eye height on ground, add pitch angle (rad) * distance from pilot to main gear, to find the eye height.
Then complete a triangle with this height, and the cutoff angle minus the chosen pitch angle. This will give a good idea on how to evaluate landing distance.
I just lack the cutoff angle.

Thanks

I don’t have them on hand right now, but I’m almost certain the diagram you’re looking for is in the FCTM. It may also be available in the airport characteristics document (I think that’s the name), which is publicly available.

https://www.boeing.com/content/dam/b...r_3.pdf#page63
I didn't find it in the FCOM but this document indeed contained very relevant information.
Page 63, 5.9 meters.
Hence I computed 15.4 meters.
Then upon landing : (5.9+5/57.3*34.85)/tan(16/57.3) = 31.2 meters.

It's a bit disappointing. It doesn't explain why we think we landed much further than we actually did.

Take a look here (attached document)

I think your FCTM will have a bit about pilot's eye height setups.

Here is the equivalent of what I am looking for :
The eye height at threshold for different types of short final guidance (PAPI, VASI, ILS..) was relevant to this discussion but not enough.
https://scontent-cdg4-2.xx.fbcdn.net...WQ&oe=665849C0
By the way, 15/tan(20°) = 41ft

Wow, that's some serious overthinking.

Agreed. And the OP doesn’t seem to have access to the FCTM which is a major source of info for a type rating course…

I’m unable to upload a picture for some reason, but the cutoff angle for the 777 is actually 21 degrees and the obscured segment is 15.4m. It can be found in this publication:

https://www.boeing.com/content/dam/boeing/boeingdotcom/commercial/airports/acaps/777_2lr_3er_f.pdf

Having said that, I concur with what other posters said above. It’s the manufacturer’s and operator’s job to ensure the plane is capable of performing LVTO and/or aprroaches to applicable mima.

and no, you don’t need you count centerline lights to assure 90m visual segment for LVTO. It’s a common misconception. The requirement is just that the airplane geometry allows for 90m visual segment (think an LVTO in Concorde or a DC-3:8). It’s not the pilot’s job to evaluate it.

as for landing geometry, it’s all in the FCTM

Do not overthink this, you don’t have time for it in the real airplane.
You land within the specified touchdown zone.
You can be a little early and you can be a little late, no two landings are the same.

You never cross the same river twice - Confucius

You never land short in a big jet, when it looks like you’ll overshoot the designated touchdown zone then (in the sim) a go-around is warranted.
For an FAA type ride that’s a FAIL/PASS item.

When someone on pprune says you’re overthinking it, you know it’s time to relax a bit :}

I'm just very surprised at the landing distance figures that we're given. Sometimes I feel like I landed at 650-700m, and the SFI will tell I landed at 450m.
This didn't happen on my previous, medium haul, type. I was able to evaluate more precisely my landing distance.

The cuttoff angle doesn't seem to explain it.

Stop fussing over details and look at the bigger picture.
Follow the cadence of the RA 50-40-30
Looking at your posting history you have a habit of going into the minutiae.


Here’s a simple test (and a question) for you:

• Pick a number, any number small or large
• Divide this number by two and continue doing this.

The question is do you ever reach zero?

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What’s a SFI?

Simulator Flight Instructor?

Synthetic Flight Instructor ;)

Simple Flight Instructor?

Amen to that!

I wonder what happened to JammedStab. He, of course, is the most experienced 777 CA ever, he'd help the OP, no doubt.

Sorry. Unfamiliar with that terminology on this side of the ocean.

OP, don’t worry too much about landing the simulator. The airplane doesn’t handle like the simulator. On top of that, your depth perception etc will be off. Just aim for somewhere roughly in the touchdown zone, and that’ll be good enough for the simulator.

Thanks for admitting that ! Nobody will say it very openly, as it could question the zero flight time training policy.

In the end my only problem lies with the simulator figures. My instructors, including the higher ranked ones that will supervise us just before and during the test, will rely on that figure and won't be happy if my figures are outside the TDZ (given the 200m problem, it's more likely that I will fall short of the 300m figure rather than the opposite).

So having some concrete figures in mind may prove useful in the future.

If I touchdown as the 600m mark disappear under the nose, the touchdown will have occured at 535m. That's a geometric fact.
However, sometimes the 600 mark disappear under the nose just after I touchdown, and the instructor comes up with a touchdown distance of 290m. That figure comes from who-knows-where.

Landings are like NPAs: there is a tolerance built in and I agree with other posters that this can be overthought. If you and/or instructors are looking at distances using 2 or 3 significant figures, it is bordering on unhealthy fixation on trivia. Really, if you can demonstrate a stable approach to flare height (25-30ft), check back a bit (2-3degs) and make it onto the ground without excessive float then it’s job done. The FCTM suggests that you should be touching down with ~150fpm ideally.

To be brutally honest, I’d rather see a “Boeing Standard” landing (firm-ish) than a failed attempt at a greaser. The 777 is a LH aircraft and on LH or ULH routes, on many occasions you have been on duty for some considerable time and may be landing somewhere unfamiliar in the dark in crap weather, or, more insidiously, in bright sunshine at 3am on your body clock. Finesse may be surprisingly lacking the first time you’re exposed to this so having a standard technique helps a lot.

The same has applied to every sim in every type I've flown (not that there are that many of them). It's not really a secret.

Don't worry, we're not trying to grease anything ! :D
I'm just a bit worried about this gap. I hope it will be resolved in other sims. We have 4 different 777 FFS.

When I converted onto the Triple, we used two sims, one of which produced what felt like a crash every time, no matter what the method used, and the other was impossible to get anything other than a smooth touchdown, even if you didn’t flare at all. Both ZFT / Level D. The instructors knew this and were looking at technique and application, rather than the actual result...

I’m not sure what training program you’re doing, but the sim is a training aid. It’s quite good, but it’s not a 777.

IMO the sim is there to give you an idea of what to expect when you show up to the aircraft, and give you the tools you need to learn how to land while you’re doing your line training.

Re simulation accuracy, assessment, etc.

Cautiously ask the instructors what the landing performance is based, their perception of touchdown point vs that assumed in performance data.

Also, query the use of 'touchdown zone'; this is an old term without meaning in commercial operations, particularly with the introduction of TALPA calculations.

These aspects are referenced in the updated version of AC 91-79B FAA Aircraft Landing Performance and Runway Excursion Mitigation, https://www.faa.gov/documentLibrary/...91-79B_FAA.pdf

3.9 Touchdown Point. The touchdown point used in the landing distance assessment reflects the assumed air distance. Operational landing data usually includes an allowance for 1,500 ft or 7 seconds of air distance from the threshold to touchdown.

5.2.4 Landing Beyond the Intended Touchdown Point. AFM/POH distances are based on a touchdown point determined through flight testing procedures outlined in AC 23-8, AC 25-7, and AC 25-32. If the airplane does not touch down within the air distance included in the AFM/POH landing distance, it may not be possible to achieve the calculated landing distance.

"Use the force, Luke!" or use the tried and tested method of TLAR. (That Looks About Right)

Doesn't that entirely fall apart unless you flare to exactly the same pitch each time?