FlightAware Discussions

leaking oil on wing

I was recently on a US Airways flight from DC to Kansas City and noticed a lot of streaked oil or something smeared on the wing. Is this a safety issue? Is this common? Thanks!


I don’t think it’s oil. It’s just streaks of dirt and dust I believe.

To me, it looks like dirt sticking to something wet. That’s why it would show up in streaks and only in one area. If it’s something wet, I would think fuel or oil. That’s why I wanted the experts opinions. From the area of the flaps, I was thinking hydraulic fluid, but I’m no plane mechanic. :slight_smile:

If it was dirt that stuck to something wet, it could have also happened a long time ago. Also, there’s no need to worry about losing hydraulic fluid as aircraft like this have 3 separate hydraulic systems that can perform all functions (double redundancy)

However, based where those streaks are coming from, it looks to be hinges or joints, so if there was some sort of fluid streaking down from there, I’m thinking it would be some sort of lubricant slowly oozing out of the hinge and not something under pressure coming out of a line.

It’s possible that at some point those parts were overlubricated which caused the buildup behind the flap edge.

It looks like several small leaks from hydraulic actuators. Fairly normal, the airplane obviously hasn’t been washed recently.

What John said. Looks like they’ve got leaks on one or two of the lift dump spoiler actuators and the pooled oil when the aircraft is on the ground is sucked onto the wing at speed.

Not a concern when in flight as the spoilers would NEVER be deployed as almost all aircraft so fitted have “squat” switches on the landing gear that ensure you’re in contact with the ground before the panels can be deployed.

what looks like hydraulic fluid could be grease from the flap actuator jack screws. Also spoilers can be deployed at a controlled angle in flight to increase descent rate without increasing airspeed. Spoilers are fully deployed upon landing to slow landing roll and are in the “armed” position during takeoff.

Spoilers are raised on the wing moving downwards every time the aileron on that wing moves up. I believe all modern jet planes have this feature.

Not true. Spoilerons.

Very Common. Almost everything leaks. Almost everything is allowed to leak to a small degree. You fly an airplane for many hours a day, on many legs a day, and it doesn’t get washed or cleaned up that often because it’s out making money for the airline, and presto: Very common. I see it all the time flying back and forth between Denver and Chicago on United. Not ideal for public relations to a skittish and unknowledgeable public, but gotta utilize that aircraft as much as possible. Clean it up when you can, replace an actuator when the leaks are beyond limits. It took probably hundreds of flight hours to get it that dirty.

And yes, the spoilers raise on the down wing when banking for a turn. They don’t raise much, and they are in synch with how much the aileron is moved. They move up and back down a few degrees all the time. They only raise up all the way when the speed brake handle is extended in flight as a speed brake, or on the ground as a ground spoiler.

Haven’t you ever watched “The Twilight Zone” ?!?! That’s where the gremlin sits!