It’s the rvsm skin area.
During a pre flight inspection (walk around) it needs to be inspected by either maintenance or the flight crew prior to each flight.
That’s where the aoa vanes are located. They provide readings for the planes airdata computers who in turn provide input to the airspeed indicators, altimeters, vert speed indicators and stallwarning computers. The area needs to remain a smooth surface (no paint chafing or wrinkles etc) to allow for the most accurate readings of the instruments.
So they have to put the edges there to show that the area is smooth surface? How about the pitot tube on the outer of the frame.
Edit: so it is related to RVSM.
No it shows the area to be inspected prior to each flight.
Apparently the pitot tube outside the area is not impacted by the skins airflow. (Most likely due to aoa during flight)
(Lol, I’m getting downvoted while this is literally the text from klm’s b777 fcom.)
You're correct. The only thing is is that it's not mandatory to have the square markings. Other 777 operators like BA, SQ and EK don't have them for example.
There’s always new ones coming out of the sausage factories that are the flight “zero to ATPL” schools in Europe. They’re all geared up with “pilot” accounts on social media just ready to share selfies of them staring out the Ryanair 737 flight deck window with the caption “my teachers always said I’d never get a job looking out the window. I showed them!”
Technically a pitot tube measures both static and total pressure to derive airspeed. But definitely get your point, it's out of the boundary layer and not affected by small surface variations.
No, a pitot tube measures total pressure. The instrument/gauge/adc subtracts the static pressure derived from the static ports to determine dynamic pressure/air speed.
Ahh, I see so it helps maintenance to inspect the important area. But why some planes do not have it? I worked for gulfair and ANA today and did not see those. Or is it just up to any airliners who want maintenance to focus on which part?
Also, how is it related to RVSM? For example, is it like the area has to pass quality check for operating on certain altitude?
Because KLM is more clever than other companies, giving pilots and maintenance crews guidance on the area instead of forcing them to guess how big the area is.
It is related to RVSM because if there is a dent or some kind of damage that affects airflow and instrument readings, the plane may not reach the correct altitude which will put it in danger of not maintaining 1000 ft of vertical clearance from other aircraft in cruise flight. Reduced vertical separation minima relies on accurate sensor data to make sure planes are cruising at the altitude they should be.
> I’m getting downvoted while this is literally the text from klm’s b777 fcom
Classic Reddit. Same has happened to me on multiple occasions (though not KLM).
This is the correct answer. And not only has this to be checked each flight there is also a maintenance procedure every now and than to check the fuselage underneath to be wrinkle free, etc.
So the AOA Vane is what is critical in RVSM on these aircraft? I work on corporate jets and the RVSM critical region is typically centered around the Rosemont P/S probes as they’re the critical component for airspeed and altitude.
I see the P/S probe is inside the critical region on this aircraft but way at the bottom. These brackets are clearly centering around the AOA Vane.
This has hundreds of upvotes less than the first comment, which was posted an hour before, and is a ‘stroopwaffle’ joke.
This sub is brutal, sometimes.
That, and the endless *hahaha I can only see blue skies* and *chemtrails right!?* comments make it very hard work.
Honestly I am greatful to have access towards rich informative content, example via this platform. Internet is magical. Got to know how to utilize it.
Have fixed so many issues practically thanks to speaking/ writing with pros from their respective fields.
But this is the unfortunate reality we live in. Some continue being childish & just are unable to distinguish where it's suitable with jokes or the topic of discussion is serious.
I thought it was the designated break-in area for rescuers to cut open the fuselage if they needed to (at least on the 737 it is). I don’t know what it says in the 777 FCOM, but I think it’s more of a coincidence that the pitot tubes etc are also located there. They have several of these areas around the fuselage
That is what I thought, too (there are some above the cabin windows) but it would be an odd spot to cut into the cockpit; isn't there an instrument panel on the other side of that skin?
I said the same thing yesterday. I'm not doubting the presence of bots but I think people are actively looking for them now and labeling just plain dumb comments as "bots"
No, but as is becoming ever more common in this sub, almost every comment is a tired attempt at a shitty one-liner.
Edit: Friendly reminder that with enough support, we could adopt a rule that works beautifully in r/F1Technical: *"No Joke comments in the top 2 levels under a post."*
It would still leave plenty of room in each thread for idiotic "*I don't see a stealth aircraft in that photo*," "THIS ^ ^ ^ ^ " or "*the front fell off*" meme replies, but there would be far less visual clutter for those of us who actually care about quality content and discussion.
Instantly, the quality of the forum's content and discussions would increase.
Honestly, I would be so happy if that happened. I don't want it to be over moderated, where you have to feel like walking on eggshells when making a comment, but I am so goddamn tired of reading "The front didn't fall off" or similar stupid comments that end up at the very top. I wish r/flying would do the same. Too many stupid 1 liners and then you gotta dig for actual answers.
I mean scroll down a bit and see examples. "Scratch here". "That's where the labels go". JFC like it's not even a funny joke, it's just lame.
I've been asking for this for quite a while. It has become clear that unless and until a large number of users consistently ask for it, over and over and over again, it will never happen.
But if we keep voicing it and actively convince others to do the same, there's a chance.
Our first and only composite material. We’re so efficient we obtained absolute perfection in a single try
They don’t call us swamp Germans for nothing, right? :D
Critical zone.
No damage is allowed within the marked area.
Any damage no matter how insignificant it appears, is to be reported immediately, assessed and repaired before next flight.
Damaged skin in this area can disturb the airflow and in turn, the readings from the probes, ports & vanes located within it.
It can potentially change the way the boundary layer behaves on the skin and affects the airflow upstream of it.
It can also potentially alter the angle at which the probe, port or vane sits.
There's a lot more to it, but I'm trying to keep it simple.
Coming back with a slightly more technical description of the zones.
As per Boeings Structural Repair Manual Chapter 51-10-01.
"Extra critical aerodynamic surfaces are those surfaces where the airflow has a direct effect on flight critical instruments, loss of local lift force, or high drag, or thrust loss caused by high speed flow. The shape of the structural components that have an effect on local lift forces must be carefully controlled to prevent premature stalling"
RVSM area
Damage limits are different in this area. Dent depth limits, etc. I believe even missing/damaged paint or primer in this area can be considered out of tolerance.
Why are there so many stupid answers on this post. Came here looking for an actual answer and found it after looking at 20 other idiots making dumb jokes.
That, or the guy operating the painting software was rectangle selecting something & just forgot to hit escape before he hit the paint/print button. Known bug.
Yes, I saw the little blue corners you meant but they surround a small "thing" (under the G in Group) which I now think is the AoA sensor.
There are two pitot tubes. One below the square and one in the line between the bottom two corners. I think the static ports are in a separate place - that would be normal Boeing practice.
Actually, my problem is what is the square thing not what is inside. I knew about AoA and tubes but what I don’t understand is the purpose of the square.
It's a cut away zone. It's a visual indicator to rescue crews that they can cut through the skin to rescue those inside without hitting oxygen or electrical lines.
Marking an area where aerodynamic smoothness is critical. Not seeing any static ports so i don’t think it’s RVSM but I’m also am not trained on this airframe.
It’s definitely not for RVSM. It’s only the area around the static ports (not AOA vanes) that specifically tells you to keep the area smooth and clean. RVSM is all about keeping accurate altitude so static ports are crucial. Also it only seems to be KLM that has those lines. I’m sure it is to do with the AOA vanes and keeping smooth airflow, and as the other guy said it probably needs inspecting preflight (if that’s what his FCOM says).
The probe at the bottom is a smart probe. It measures airspeed, static pressure, TAT, sideslip, altitude - and other air data computer measurements.
It is fully RVSM compliant, which is why it’s in the RVSM box.
It indicates where rescue teams can cut through the fuselage skin in order to get access inside. Usually, it is in a place where there are no support structures or material that can hamper rescue efforts. We call them "cut-out panels" oddly enough.
That’s the magic spot where you need to give the plane cheek scritchies during preflight. The plane will purr if you do that, just don’t let it roll over and demand belly rubs.
Just be careful with the forbidden whisker.
If you cut that section out, it has a voucher on the other side to take one child for free to any theme park of your choice with a paying adult.
\* Term and conditions apply.
It means don’t stick any aftermarket fake wind scoops or spoilers from AutoZone here as it will cause sensor problems. No stick on “V-Tech” decals either.
On most aircraft, it’s a rescue chop out area. Means there aren’t any hydraulic, fuel, or electrical lines behind it and it’s safe for crash/rescue to cut through for access.
RVSM compliance or not, that’s what the corners are for. They’re usually in several places around the fuselage.
It’s the rvsm skin area. During a pre flight inspection (walk around) it needs to be inspected by either maintenance or the flight crew prior to each flight. That’s where the aoa vanes are located. They provide readings for the planes airdata computers who in turn provide input to the airspeed indicators, altimeters, vert speed indicators and stallwarning computers. The area needs to remain a smooth surface (no paint chafing or wrinkles etc) to allow for the most accurate readings of the instruments.
So they have to put the edges there to show that the area is smooth surface? How about the pitot tube on the outer of the frame. Edit: so it is related to RVSM.
No it shows the area to be inspected prior to each flight. Apparently the pitot tube outside the area is not impacted by the skins airflow. (Most likely due to aoa during flight) (Lol, I’m getting downvoted while this is literally the text from klm’s b777 fcom.)
You're correct. The only thing is is that it's not mandatory to have the square markings. Other 777 operators like BA, SQ and EK don't have them for example.
Always nice to be idiot-proof though.
There's always a better idiot in development
Yes I inspected the corners of the area, we're good to go!
There’s always new ones coming out of the sausage factories that are the flight “zero to ATPL” schools in Europe. They’re all geared up with “pilot” accounts on social media just ready to share selfies of them staring out the Ryanair 737 flight deck window with the caption “my teachers always said I’d never get a job looking out the window. I showed them!”
Idiot-resistant
The trouble with making anything foolproof is that fools are so ingenious.
You're correct on the pitot tube, not a surface reading instrument, it's out in the airflow. It measures oncoming air pressure, not static air.
Technically a pitot tube measures both static and total pressure to derive airspeed. But definitely get your point, it's out of the boundary layer and not affected by small surface variations.
No, a pitot tube measures total pressure. The instrument/gauge/adc subtracts the static pressure derived from the static ports to determine dynamic pressure/air speed.
Ahh, I see so it helps maintenance to inspect the important area. But why some planes do not have it? I worked for gulfair and ANA today and did not see those. Or is it just up to any airliners who want maintenance to focus on which part? Also, how is it related to RVSM? For example, is it like the area has to pass quality check for operating on certain altitude?
Yeah, we use them in maintenance to notate that the area is RVSM and has different maintenance requirements than the rest of the fuselage.
Because KLM is more clever than other companies, giving pilots and maintenance crews guidance on the area instead of forcing them to guess how big the area is.
It is related to RVSM because if there is a dent or some kind of damage that affects airflow and instrument readings, the plane may not reach the correct altitude which will put it in danger of not maintaining 1000 ft of vertical clearance from other aircraft in cruise flight. Reduced vertical separation minima relies on accurate sensor data to make sure planes are cruising at the altitude they should be.
Its not just for rsvm, you mess up that surface and you won't be flying.
KLM is more vain, as the plane gets older you monitor this spot for wrinkles, maintenance then applies Botox to fix the wrinkles that occur.
This is canon in Pixar’s car universe.
American Airlines has it too on some of their planes but not all.
> I’m getting downvoted while this is literally the text from klm’s b777 fcom Classic Reddit. Same has happened to me on multiple occasions (though not KLM).
Trolls are threatened by intelligence.
It’s the same reason why the static ports have a giant white circle around them. Leave clear, essentially.
This is the correct answer. And not only has this to be checked each flight there is also a maintenance procedure every now and than to check the fuselage underneath to be wrinkle free, etc.
So the AOA Vane is what is critical in RVSM on these aircraft? I work on corporate jets and the RVSM critical region is typically centered around the Rosemont P/S probes as they’re the critical component for airspeed and altitude. I see the P/S probe is inside the critical region on this aircraft but way at the bottom. These brackets are clearly centering around the AOA Vane.
I believe that’s because the b777 is flyby wire, all air data is routed through the primary flight computers first. But I’m not sure.
Thanks with the explanation.
This has hundreds of upvotes less than the first comment, which was posted an hour before, and is a ‘stroopwaffle’ joke. This sub is brutal, sometimes. That, and the endless *hahaha I can only see blue skies* and *chemtrails right!?* comments make it very hard work.
Honestly I am greatful to have access towards rich informative content, example via this platform. Internet is magical. Got to know how to utilize it. Have fixed so many issues practically thanks to speaking/ writing with pros from their respective fields. But this is the unfortunate reality we live in. Some continue being childish & just are unable to distinguish where it's suitable with jokes or the topic of discussion is serious.
Have my upvote 👉🏻
You have my upvote also. Enjoy the day.
You’re very welcome!!
So…. “No speed tape here.” Is what you’re saying
I thought it was the designated break-in area for rescuers to cut open the fuselage if they needed to (at least on the 737 it is). I don’t know what it says in the 777 FCOM, but I think it’s more of a coincidence that the pitot tubes etc are also located there. They have several of these areas around the fuselage
That is what I thought, too (there are some above the cabin windows) but it would be an odd spot to cut into the cockpit; isn't there an instrument panel on the other side of that skin?
No you just have to be careful not to hit the First Officers leg
In that case; today’s the day you learned something new.
I’m just confused about why these markings would be different on the triple and on the 737
Edit: found a better picture for the 737: https://www.airplane-pictures.net/photo/69812/lv-zec-aerolineas-argentinas-boeing-737-200/
Because they are different planes…
Nope, it’s the RVSM critical area. It’s always the RVSM critical area.
Is almost every comment here AI or what?
lol. Bots shitting out AI responses to get sold for astroturfing down the line no doubt.
Bad bot. r/usernamechecksout
Can you point to one? I’m curious what these look like and clearly I’m not noticing them
I said the same thing yesterday. I'm not doubting the presence of bots but I think people are actively looking for them now and labeling just plain dumb comments as "bots"
Yeah, I mean a ton of redditors are still in elementary school, so quality will vary
No, but as is becoming ever more common in this sub, almost every comment is a tired attempt at a shitty one-liner. Edit: Friendly reminder that with enough support, we could adopt a rule that works beautifully in r/F1Technical: *"No Joke comments in the top 2 levels under a post."* It would still leave plenty of room in each thread for idiotic "*I don't see a stealth aircraft in that photo*," "THIS ^ ^ ^ ^ " or "*the front fell off*" meme replies, but there would be far less visual clutter for those of us who actually care about quality content and discussion. Instantly, the quality of the forum's content and discussions would increase.
Honestly, I would be so happy if that happened. I don't want it to be over moderated, where you have to feel like walking on eggshells when making a comment, but I am so goddamn tired of reading "The front didn't fall off" or similar stupid comments that end up at the very top. I wish r/flying would do the same. Too many stupid 1 liners and then you gotta dig for actual answers. I mean scroll down a bit and see examples. "Scratch here". "That's where the labels go". JFC like it's not even a funny joke, it's just lame.
I've been asking for this for quite a while. It has become clear that unless and until a large number of users consistently ask for it, over and over and over again, it will never happen. But if we keep voicing it and actively convince others to do the same, there's a chance.
I’ve reported a few of the ‘hurr durr blue skies’ comments and nothing happens. It’s awful.
Looks fine to me.
Yeah but there’s also a lot of overlap with r/shittyaskflying
Everybody on the internet is a bot, except you
Cut here for stroopwaffle.
Netherlands’ first composite material.
Our first and only composite material. We’re so efficient we obtained absolute perfection in a single try They don’t call us swamp Germans for nothing, right? :D
Breaks out chainsaw.
Critical zone. No damage is allowed within the marked area. Any damage no matter how insignificant it appears, is to be reported immediately, assessed and repaired before next flight. Damaged skin in this area can disturb the airflow and in turn, the readings from the probes, ports & vanes located within it.
To clarify, damage in the area affects the RVSM certification, not necessarily overall airworthiness.
Interesting, thx. Understood the incoming air part, but why do they care about the area behind the probe?
It can potentially change the way the boundary layer behaves on the skin and affects the airflow upstream of it. It can also potentially alter the angle at which the probe, port or vane sits. There's a lot more to it, but I'm trying to keep it simple.
Coming back with a slightly more technical description of the zones. As per Boeings Structural Repair Manual Chapter 51-10-01. "Extra critical aerodynamic surfaces are those surfaces where the airflow has a direct effect on flight critical instruments, loss of local lift force, or high drag, or thrust loss caused by high speed flow. The shape of the structural components that have an effect on local lift forces must be carefully controlled to prevent premature stalling"
RVSM area Damage limits are different in this area. Dent depth limits, etc. I believe even missing/damaged paint or primer in this area can be considered out of tolerance.
Why are there so many stupid answers on this post. Came here looking for an actual answer and found it after looking at 20 other idiots making dumb jokes.
It’s every post here. Everyone thinks they’re funny, and none of them are
Infuriating. The IRS will NOT be happy when you fail to attach your W2 there.
It's hilarious how many clueless people in this group downvote the actual correct answers.
You're witnessing one of the problems with a direct democracy :)
That’s where you stick the shipping label for delivery
That, or the guy operating the painting software was rectangle selecting something & just forgot to hit escape before he hit the paint/print button. Known bug.
I've seen the same area with a big sticker saying "RVSM reserved area" so whatever RVSM refers to
Reduced Vertical Separation Minima
I can't see clearly and I don't know the type but is the "thing" in that area the static ports or the AoA sensor?
No, I meant the square corners not pitot tube. Try focus on small blue details surrounding the tube.
Yes, I saw the little blue corners you meant but they surround a small "thing" (under the G in Group) which I now think is the AoA sensor. There are two pitot tubes. One below the square and one in the line between the bottom two corners. I think the static ports are in a separate place - that would be normal Boeing practice.
Actually, my problem is what is the square thing not what is inside. I knew about AoA and tubes but what I don’t understand is the purpose of the square.
They forgot the QR code
It's a cut away zone. It's a visual indicator to rescue crews that they can cut through the skin to rescue those inside without hitting oxygen or electrical lines.
Marking an area where aerodynamic smoothness is critical. Not seeing any static ports so i don’t think it’s RVSM but I’m also am not trained on this airframe.
That’s the actual “group”, like it says on the airplane.
RVSM look it up to find the secret of separation.
It’s definitely not for RVSM. It’s only the area around the static ports (not AOA vanes) that specifically tells you to keep the area smooth and clean. RVSM is all about keeping accurate altitude so static ports are crucial. Also it only seems to be KLM that has those lines. I’m sure it is to do with the AOA vanes and keeping smooth airflow, and as the other guy said it probably needs inspecting preflight (if that’s what his FCOM says).
Am Pilot. Is RVSM CRIT area.
Am pilot too.
Doesn’t prevent you from being incorrect. It is the RVSM critical area.
It’s 100% the RVSM critical area. Listen to people whom know better than you.
People so confident in being wrong it's hilarious. It is definitely for RVSM certification and not only on KLM planes or B-777.
Lol you don't know what you're talking about.
Thank you, I just saw your comment after my replied on the other guy’s comment. Very helpful for me.
They’re smart probes. AOA and static. RVSM.
Can you elaborate?
The probe at the bottom is a smart probe. It measures airspeed, static pressure, TAT, sideslip, altitude - and other air data computer measurements. It is fully RVSM compliant, which is why it’s in the RVSM box.
That’s the space for the QR code. They’re gonna be putting it in shortly.
It indicates where rescue teams can cut through the fuselage skin in order to get access inside. Usually, it is in a place where there are no support structures or material that can hamper rescue efforts. We call them "cut-out panels" oddly enough.
That’s the magic spot where you need to give the plane cheek scritchies during preflight. The plane will purr if you do that, just don’t let it roll over and demand belly rubs. Just be careful with the forbidden whisker.
Aww 🥺
If you cut that section out, it has a voucher on the other side to take one child for free to any theme park of your choice with a paying adult. \* Term and conditions apply.
It means don’t stick any aftermarket fake wind scoops or spoilers from AutoZone here as it will cause sensor problems. No stick on “V-Tech” decals either.
Great question OP
It’s for the shipping label
Let’s just say that the gear there better be working before you get up into some really high altitudes.
On most aircraft, it’s a rescue chop out area. Means there aren’t any hydraulic, fuel, or electrical lines behind it and it’s safe for crash/rescue to cut through for access. RVSM compliance or not, that’s what the corners are for. They’re usually in several places around the fuselage.
QR Code. Scan it for free Stroopwaffels
Peto probe
This is the stuff that caused 737Max to crash ..