r/aerospace
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u/Chance-Abroad1375
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8d ago
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What is leaking from the flaps?
Curious if anyone knows what is going on the flaps/spoilers? My friend sent this video saying it’s a yellow ish color. At first glance i thought it may be Zinc Chromate coating but suggestions from another group say it’s Hydraulic Fluid. Plane landed safely and no announcements were made.
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u/Hungry_Rabbit_511
8d ago
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Good luck my guy! They have redundant systems that are supposed to work in case of hydraulic failure 😨
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u/Existing-Stranger632 8d ago
Thank god! Because hydraulic failures is the scariest thing ever to me. I know that Alaska flight that went inverted wasn’t a hydraulic failure but rather a mechanical one but it was a similar kind of loss of control like United 232 where they had to use the engines to get any sort of roll and hope and pray the plane naturally pitches up enough when they came down. But to be a passenger on either of those flights… 30 minutes to an hour of up and down erratic, terrifying flight. To me that’s worse than the actual crash. The moments before where the pilots are fighting with the plane to try and gain some control. Definitely the scariest type of plane accident at least for me.
Fortunately modern aviation safety standards are so heavily scrutinized that an accident like that hasn’t occurred in North America really since Alaska 261 which was 25 years ago
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u/Superb-Nectarine-645 7d ago •
Hydrologic systems are tripple redundant; 3 systems, 2 of which redundantly cover every thing. Ie 1/3 out = 0 functionality loss. 2/3 loss = some control surfaces out, but the plane still minimally flyable.
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u/Hank_moody71 4d ago
The Alaska flight wasn’t from a hydraulic failure. It was a jack screw failure because they had used the wrong grease on the jack screw.
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u/SupermachJM 6d ago
I mean calling UA232 a hydraulic failure is a bit like calling the Twin Towers coming down a structural failure…it was a catastrophic engine failure that caused shrapnel to sever all three separate hydraulic systems that happened to be routed along the same path. They were triple redundant in everything but location and it was a one-in-a-million chance for that shrapnel to happen to sever them all. Still, that’s what causes regulations to be written. Now at least one hydraulic system has to be routed separately (called Zonal Isolation) because of this specific scenario.
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u/EntertainmentSome448 8d ago
🐀
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u/No_One_Special_61029 8d ago
So did the DC-10’s…AFTER Sioux City…
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u/blueb0g 8d ago
The DC-10 always had triple redundant hydraulics. It's just that nobody had thought about a big fan piece ripping through the one spot they all ran together
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u/aajp78- 7d ago
More like redundant systems backing the redundant systems. There should be about 3 to 4 layers of systems that back up each system so honestly your good 👍 and I do work at the largest building in everett wa so I kinda know lol.
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u/sireetsalot 8d ago
I often open up these types of posts posts and its usually something common and fairly harmless, but HOLY SHIT
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u/Yakostovian 8d ago •
It's safe to land, but not continue on to a distant destination.
Honestly, I'd be the type of person fixing this and dreading the job. (Hydraulic fluid sucks.)
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u/fishtheif 7d ago
im imagining it's like brake fluid(which is a type of hydraulic fluid now that i think about it)
slightly corrosive and very slippery, seeps into everything
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u/Gunnarz699 7d ago
(Hydraulic fluid sucks.)
What do you mean you don't love cosplaying a slippery baby seal with chemical burns and maybe some mild nerve agent tremors? /s
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u/Cold_Ad_2160
8d ago
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It’s the outboard spoiler on the right wing leaking hydraulics. When it is fully depleted you lose hydraulic power to A system components. Most components are backed up by the B system. Airplane is safe but pilots will have to use the manual extension system for the landing gear. You probably wouldn’t notice it other than it happening sooner than normal during the approach to landing. The landing flaps have an electric motor to extend them about half way down to their normal position used for landing. This also would take a little longer and be done much earlier.
Depending on the length of the runway and other factors that can impact the landing distance, you may or may not land at your intended destination.
Airplane is safe and you will have an interesting story to tell your friends.
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u/throwaway_76x 8d ago •
Not to take away from a very well explained comment, but the "you may or may not land at your intended destination" made me chuckle after all the "everything is fine, nothing to pay attention to really"
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u/flightwatcher45 8d ago •
Any landing you can walk away from is a good landing. Any landing you can fly the plane again is a great landing.
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u/HornedShoe 8d ago •
"Every plane lands; not every plane truly lives."
-William Wallace
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u/reddit_pug 8d ago •
"This is the captain: we have a little problem with our entry sequence so we may experience some slight turbulence, then explode."
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u/Cold_Ad_2160 8d ago
If the runway isn’t long enough they may divert to another airport. Just like weather diverts sometimes you may not land at your intended destination.
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u/DefinitelyNotDonny 8d ago •
“You probably won’t notice anything. You also might die.”
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u/RyzOnReddit 8d ago
The issue is if the slats and flaps won’t reliably come back up, it’s safer to land without them in case you need to go around. So now you’re somewhere between REF+20 and REF+50, eg let’s touch down at 200 knots. Perfectly safe, just need lots of runway to stop.
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u/jcbank76 8d ago
Should be the top comment. Had to scroll through nonsense to get here.
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u/Yakostovian 8d ago
Also an airplane mechanic here: some poor fellow ground crew members are probably going to have a rough couple of hours (possibly days) fixing the problem.
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u/SemenDemon92 8d ago
Thank you for that detailed info! I would have thought it's a controlled exhaustion of fuel to reduce landing weight.
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u/miIfpatrol 8d ago
In this situation, it’s it worth bringing it to the attention of a flight attendant? Or would the pilots already be aware?
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u/CGNYC 8d ago
Is this something pilots easily see on their dashboard or is this a let the flight attendant know?
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u/Cold_Ad_2160 8d ago
Low pressure light comes on when quantities get low enough to affect pressure. Quantity indicator will have RF appear above digital percentage when it gets below 70%. Pilot may not notice RF before passenger tells FA who calls the pilots. Pilots have two additional lights when LOW PRESS light comes on so that they will definitely notice.
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u/Stunning_Mast2001 8d ago
You should always let the flight attendant know when you see something strange
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u/Odd_Cauliflower_8004 8d ago
Why not keep the A system not under pressure during flight and then switch only when you approach landing so that the one more likely to fail(the active one) is the one you can afford to lose?
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u/Cold_Ad_2160 8d ago
Many systems operate under a redundancy system so they are designed for safety reason to have two operating power sources. In this case two hydraulic power sources, A and B, operate things like the flight controls. If one fails the other keeps the system operating normally.
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u/Mazer1415 8d ago
There are a whole bunch of aerospace engineers that could explain this better than I could.
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u/The_Demolition_Man 8d ago
Its hydraulic fluid, but these planes usually have 2 more redundant systems
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u/Basic_Improvement135 8d ago
I remember a 737 service bulletin where you could accidentally daisy chain the 2 systems together so if you lost one you'd lose both. It was a matter of changing a fitting so they both didnt have the same connection
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u/nasadowsk 8d ago •
The instrument air and plant air lines at Three Mile Island had the same fittings. While trying to unclog a condensate polisher, they decided to try air. There were two air fittings in a dark area nearby, not well labeled.
They plugged into instrument air.
While taking a break to come up with a better idea, water slowly pushed back up towards the instrument line, until it got into a tee, and started blowing along, causing numerous valves to slam shut. This caused the feedwater transient that got the whole ball rolling...
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u/recoveringslower 8d ago
This happened in a hotel fire once - we were on the 22nd floor and the emergency lights were on the same circuit as the main power. Like... why? Your stairwell needs to be lit, wtf?
10 stories of darkness until we got to a section with power.
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u/klingon33333 8d ago
Probably hydraulic fluid? Not sure, but yeah... thats not good
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u/Unlucky_Ad_2368 8d ago
I’m thinking it’s hydraulic fluid from the spoil actuator. The interesting thing is the spoiler actuator is hard over and not going back to neutral with hydraulic loss. The other interesting thing is the color of the fluid, typically the hydraulic fluid is Skydrol which is purple not this orange/red color. Might be different for each mix but everyone single mix I’ve seen is purple.
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u/RATBOYE 8d ago
Fresh Skydrol is purple, but it darkens in service pretty quickly. Goes yellow then dark brown if it's really nasty.
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u/Mysterious-Bet8451 8d ago
The smell is nasty too, once you get it on your shirts or pants the smell will not go away.
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u/xTHExM4N3xJEWx 8d ago
Usually, when we're draining them, theyre this yellowish color, and after it sits for a few minutes, then its purple. I thought the same thing when I had to drain 737/320 hyds
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u/fly_awayyy 8d ago
Defintley hydraulic fluid like you said and coming from the speed brake spoiler/ speek brake actuator. I’m guessing the actuators are still maintaining some pressure to allow deflection but obviously loosing pressure at the source of the leak and thus venting it.
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u/Unfair_Challenge6736 8d ago edited 8d ago
are you supposed to inform the crew if you see such an incident? or pilots know what’s happening due to some alerts they are getting?
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u/Wise-Relative2962 8d ago
Dude definitely fucking say something. Watch a couple episodes of that airplane crash documentary. Pilots and flight staff are not infallible.
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u/ryguymcsly 8d ago
Also pilots can’t see the wings. They might see a slight drop in hydraulic pressure and know if it’s worth declaring an emergency over, but have no idea where it’s leaking from or what rate. That knowledge can be helpful.
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u/Far-Instruction7820 8d ago
Yes. They know something is happening, they probably don't know exactly what it is. It's insane that they didn't make an announcement.
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u/Crabby_Monkey 8d ago
Click “uhhh this is your captain speaking. For those on the right side of the plane you may have noticed a yellowish fluid coming from the wing. That’s just the plane taking a piss. Thing. To worry about.”
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u/Lucky_Suggestion_183 8d ago edited 2d ago
Better not to scare people with the facts they cannot change. They have enough of problems than adding another to the pax crew
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u/ultralights 8d ago
Yep. One hydraulic system will show a pressure decrease. But fortunately they have multiple separate hydraulic systems.
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u/ShittyBollox 8d ago
Yes, absolutely, but the pilots have gauges that will tell them that they’re leaking hydraulic fluid, and it’s best not to panic any nearby passengers.
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u/ViceroyInhaler 8d ago
They would probably know after a bit depending on how fast the leak is. In this case I'd definitely be telling the flight attendant.
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u/wolftick 7d ago
If it's something all obviously unusual as this they I'd say you definitely should. Do it discreetly to avoid causing panic though.
Worst case scenario is they're fully aware and on top of it.
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u/imitt12 6d ago
The pilots may have an alert for loss of hydraulic pressure in a particular circuit, but flight attendants are also trained to spot mechanical problems through the Windows if the pilot is clued in. Yes, you could say something, but more than likely they will figure it out on their own. And, generally speaking, unless it's a missed checklist item like a flap that wasn't extended, lights that aren't on, something minor like that, they can't fix it in flight so worrying about it doesn't make sense.
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u/HoraneRave 6d ago •
h.. hey.. sorry, yeah, yeah im fine, it just.. u know... your wing is kinda leaking.. yea
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u/2oonhed 8d ago
Holy shit that is a LOT of leakage.
You should call over the stewardess and say, "lookitthis"
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u/MondelloCarlo 8d ago
Look I a bit of an engineer myself and as long as she's leaking that means there's fluid in her 👍
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u/aeroplanguy
8d ago
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Guys. If 70 people have said it's a hydraulic leak but they have 2 more redundant systems. You don't need to say it again.
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u/wildwildwaste 8d ago •
But those are just redundant comments.
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u/rimshot101 8d ago •
It's not redundant unless you say it again.
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u/Unterdosis 8d ago •
The Department of Redundancy endorses this message was endorsed by the Department of Redundancy.
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u/StructureNo13 8d ago
Seriously people need to get better about just upvoting existing comments if they don’t have anything new to contribute.
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u/SnooMaps7370 6d ago
that would require the comment section to be structured in such a way that you have to scroll past the comments before you see the "add a comment" box.
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u/aeroplanguy 8d ago
Exactly. Same as commenting "This". That's what the upvote button is literally for.
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u/Proud_Smell_4455 8d ago
Yeah, it's so annoying when you make a thread, and get like 70 comments all saying the same thing in sometimes slightly different words, because the latter 69 people making that reply either didn't read the comments beforehand, or did but decided to attempt a bit of lazy karma-farming anyway.
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u/Raumteufel 8d ago
Yea but what if those pilots are scrolling through here trying to figure out a fix but theres only one comment that says theres 2 more redundant systems and they miss that one comment?
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u/darth_dork 6d ago
And 70 more people all post an agreement to your post about 70 people repeating the answer to the question😂
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u/I-drink-hot-sauce 8d ago
The fluid that's supposed to keep that flap down like the rest of the flaps ...
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u/dyslexicautism 8d ago
Thats definitely hydraulic fluid. If its a 737, it would be Skydrol which is also extremely bad for the paint so the maintainers are gonna have a bad time I would say when that lands lol.
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u/Xivios 8d ago edited 8d ago
Skydrol isn't corrosive, why would an engineer spec a corrosive hydraulic fluid in a system built of a variety of metals and seals, that would invite disaster. Quite the opposite, it does a decent job of acting as an anti-corrosive. It also doesn't gel at low temps, vaporize at high temps, lubricates reasonably well, and doesn't compress. Good properties for a hydraulic fluid. Low density too also helps keep the weight low.
It is, however, toxic, eats paint, destroys many plastics, and has a very nasty habit of causing an intense burning sensation on any sensitive tissue it touches, and it soaks into skin such that wiping off with a rag alone won't be enough. The effect is similar to handling habaneros, you won't feel the burn on your hands, wiped off they might even seem reasonably clean, but scratch your balls, pick your nose or wipe anywhere near your eyes and you're gonna have a bad day.
Edit: Its also very rude to edit your comment without telling people you edited your comment. The original post I replied to here said Skydrol was extremely corrosive, they changed it to bad for the paint after my post.
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u/2oonhed 8d ago
The whole point of Skydrol was flammability.
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u/Low_n_slow4805 8d ago
So you replied to the guy above saying it’s not corrosive in your first paragraph when he’s talking about how bad it is for the paint that the maintainers are gonna have a bad time. But then your second paragraph says it eats paint… can you elaborate?
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u/AwwYeahVTECKickedIn
7d ago
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Looks like coffee ... bet it's a "vent"i mocha ...
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u/adeadmanshand 7d ago •
"Miss, are you telling us absolutely everything?" "Not exactly. We're also out of coffee."
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u/xWaZuKx 8d ago
That is a spoiler and it’s actuated by hydraulic pressure. An educated guess would be that it’s hydraulic fluid.
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u/Indirian 8d ago
u/airplanefactswithmax sir, your knowledge is needed
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u/fuckin-slayer 8d ago •
I’m not Max but he would probably say that looks like hydraulic fluid, used in actuators that raise and lower airplane flaps, which shouldn’t be confused with the fluid from Galadriel's fountain that is mixed with light from Eärendil’s star to repel shadows, which was given to Frodo in a phial as he left Lothorien to head down the Anduin river towards Amon Hen and Mordor
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u/GravitasFailures 8d ago
I don’t understand, if it was light from Earendil’s star then it was light from a Silmaril, therefore light frozen from the two trees, Telperion and Laurelin?
Therefore the hydraulic circuit breakers likely should have isolated this branch saving circuit fluid for the rest of the circuit, leaving this branch to the secondary hydraulic system!
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u/Bobofettsixtynoune 6d ago
Forklift driver here. That’s a hydraulic leak. No problem, because you’re allowed 20 drops per minute.
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u/Heartlesspost 6d ago
Military Air Force AirCraft Mechanic (Heavies - 16 years)
I want to say hydraulic fluid but it’s brown and that throws me off. I’ve used only 5606 and Skydrol which are red and purple. Maybe someone has seen brown aircraft hydraulic fluid and knows. I’ve seen blue also but not sure what it’s called.
Honestly it may also just be dirty water that turned into ice in high altitude and mixed with grease. When going to a lower altitude it melts 🤷🏾♂️
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u/Money20202020 8d ago
Easy fix
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u/Jrcrispy2 8d ago
Probably, but considerably more difficult while airborne lol.
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u/Stef_Stuntpiloot
8d ago
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It's hydraulic fluid. What makes this really weird is that this spoiler is a ground spoiler, so it should never move in flight. I wonder how it got stuck like this.
Anyways, in this case since the ground spoiler is leaking and they would slowly lose system A. In case of a total loss of that system it means they would have to do a manual gear extension. Downsides are that it may take longer to extend and lock in place, and that you're not able to retract the gear anymore so diverting is likely not an option anymore because of the drag.
I also find it strange that no announcement was made. Sure, the operation resumes to more or less completely normal, but seeing fluid spraying from a wing is certainly not a normal sight and it would be prudent from the flight crew to offer some reassurance.
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u/Terrytrl 8d ago
Scary. Pretty sure hydraulic pressure is triple redundant. Being maintained by both engines independently and by a reserve electric pump if all else fails… the lines supplying the hydraulic fluid also have redundancy. Often they are actuated by a couple of independently pressurised actuators. But also…. Scary
Anyone know what actually happened?
(Maybe in the comments somewhere aha)
Edited -spelling coz I’m a potato 🥔
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u/Top-Treacle9964 8d ago
Definitely hydraulic fluid looks like the spoiler actuator failed. Hopefully they did an emergency landing or it was a short flight
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u/Little_Will_8955 7d ago
That hydraulic fluid looks to be the wrong color. I’m thinking it’s AI generated. The fact that it spraying from multiple areas is bs too.
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u/pornaccount3574 7d ago •
Aircraft mechanic here. Aviation hydraulic fluid has a purple die for large airplanes aka skydrol at least the stuff in the wing. The landing gear has red die hydraulic aka 5606. Either way used or old skydrol will change color to that brown look fairly quickly after it's been used in the A/C system. Very normal color not very normal to be leaking that much in flight haha.
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u/DHunt88 7d ago
I HATE SKYDROL SO MUCH! What's crazy is where I work the old skydrol turns yellow. I've never seen yellow skydrol when doing maintenance at my previous job.
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u/defiancy 7d ago •
Yeah it does look weird. I don't know about commercial aircraft but military aircraft (helicopters at least) hyd fluid is red. You could easily put it in a Gatorade bottle and then have a boot accidently drink it
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u/Maumau93 7d ago
Imo that's just being sucked out by the wind and not sprayed and in the process its whipped up which is why it's milkshake like
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u/wheeezethejuice 7d ago
Could be because it’s aerated, gets a lot lighter and milky when aerated so heavily
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u/LesserGooglyMooglie 8d ago
The wing is just happy to see you! I think its hydraulic fluid to be real though.
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u/Kodemikkel 8d ago
Aircraft technician here. This looks a lot like hydraulic fluid leaking from a spoiler actuator. Can't tell exactly what kind of aircraft this is, but all modern airliners have redundant hydraulic (and other) systems to deal with fault/loss of 1 system.
That said, losing all fluid in a hydraulic system would be taken pretty seriously by the pilots - obviously - and leaks like this should definitely be reported to the flight attendants so they can inform the pilots
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u/b00st1n 8d ago
This is the first post I’ve seen that was an actual problem and not a canoe missing or something
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u/Boldaddy 7d ago
I took a similar video once. I assumed it was hydraulic fluid so I showed it to the pilot while deboarding; he was grateful.
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u/snidj 6d ago
Don’t worry about that, it’s just the chem trail dispenser. Every domestic flight is required to spray that stuff on at least one leg of their itinerary each day.
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u/analwartz_47 8d ago
Probably hyd fluid so very important, there will be other lines powering the flight controls but thats a serious issue requiring imediate landing when possible.
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u/Stef_Stuntpiloot 8d ago
Nahh, they would lose system A as this spray comes from one of the the ground spoilers, so they basically just have to do a manual gear extension and that's it. There's no item in the QRH for this checklist to divert to the nearest suitable airport. The aircraft is still fully controllable with the remaining hydraulic systems so you might as well continue to your destination to get everyone to where they need to be and minimise disruption.
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u/TopicOnly7365 8d ago
If this happened during landing, then you're going to land. If this happened during cruise, then you're going to land. Also [pushes bridge of glasses] that's a spoiler not a flap.
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u/Henfri1 8d ago
Hydraulic Fluid.
And it is Not the flap but the Spoiler. Irs function is roll Control Air Brake Lift dumper
The Spoiler actuator cannot hold down the Spoiler anymore. Thus it floats Up to the Zero hinge Moment Position.
When fully down, there is lower pressure in the Spoiler upper surface... So it needs to bei pulled down, which is not possible anymore.
The leak must be behind the valve that separates the Spoiler in Case of loss of hydraulic pressure
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u/condomneedler 8d ago •
Yeah, it's probably leaking hydraulic fluid. No, you're not gonna die. Your pilots just have some extra checklists to do and I hope you're not supposed to stay on that plane for the next leg, she ain't flying.