French Air Force A310 … 1496917/M/

Brake dust?

Burning tire or brake assembly IMHO.

Yes that is brake dust.

Most aircraft brakes are carbon-type brakes, these are commonly found on higher performance brakes than your standard Chevy sedan. Unlike standard car brakes (and many lighter aircraft) that the heavier you brake, the more is worn off the pads, Carbon based brake pads actually wear less the harder you hit the brakes. Most jetliner AFMs actually have a portion just dedicated on how to brake properly. Light taps on the brakes cause pieces of the pads to break off and will actually start wearing the brake pads down significantly. On higher performance carbon based brake pads, when a pilot hits the brakes harder, they heat up very, very quickly and will develop a dust layer between the pads and the rotors. This layer of dust still keeps the same amount of braking power, but causes those particles of the pads to get suspended in the dust instead of gouging out pits in the pads/rotors. As soon as an aircraft takes off, this dust is generally blown off the brakes. Next time you’re on an airliner, you’ll know why the pilots hit the brakes hard (even when taxiing) instead of a light, gradual pressure.

If you look at performance carbon brake pads for cars, you’ll read somewhere on the box that they aren’t recommended for “normal” street use because it’ll wear out the pads very quickly if hard braking isn’t used.

Really? What prevents the dust from being blown off while the aircraft is on the runway? Or a taxi way? Or just standing in the wind?

The gear appears to be retracting, at which point whoever is flying would normally depress the brakes firmly to stop the tire rotation prior to the wheels being housed. But for that to be brake dust would mean that they have an extreme problem in the making when next they attempt to apply the brakes.

Simply brake dust? I don’t think so.

Thank you for the 411 on brakes…I’ve seen a few changed over the years :wink: …and JHEM, interesting observation regarding the retraction, I never knew that the capt. was hitting the brakes before bringing up the gear, it does make sense.

Speed is simply it. It gets removed constantly, but more will be removed at 150 kts versus 20 kts.

Here’s another picture as well:—Royal/McDonnell-Douglas-MD-11/1476069/L/
There would be a lot more problems in the sky if it were anything else because it is a very common site.

You don’t have to depress the brakes that firmly. In fact, it’s just a very light tap because there is no weight on the wheels to require them to have much momentum at all. Additionally, a few modern aircraft also now include a system to apply light pressure at retraction to automatically stop tire rotation upon selecting gear retraction. In the nose wheel well, there are large pads (one for each tire) that actually make contact with the nose tire to stop it’s rotation when it retracts. Additionally, you’ll see many fixed gear pilots tap the brakes lightly after rotation because the wheels may be out of balance and they will start to vibrate extensively after the tires leave the ground and they start to slow down. One caution on this is to make sure you’ve gained some altitude because if the aircraft settles accidently on the runway and ones feet is still on the brakes, there is a large potential for the tires to blow or the nose to come crashing down and damage the nose gear and/or prop strike.

When airliners return for landing, they apply the brakes again heavily and they return right back the same way as before. Obviously not all brake pads are made the same, some will produce more overall film than others.

You forgot this

Sorry to change the subject, but I was just reminded of an incident from a flight a long time ago. I was on a puddle jumper (forget the AC type - it had a high wing, engines mounted below the wings and landing gear extended from below the engine pods), seated just above the wheels and could see them out the window if I looked down. During takeoff, I saw a fountain of sparks coming from the wheels as the plane rotated and left the ground. I sent a written message to the captain via the flight attendant, and his reply was that “it’s normal”. Is it normal, or was the captain just trying to reassure me?

:open_mouth: :open_mouth: Im not a mech, but really “Normal” for sparks?!?! :open_mouth:

I agree…I don’t know about sparks being anything normal on a plane built after 1960. Before that…all is fair game.

Sounds like the plane you were on might have been a Bombardier (De Havilland Canada) Dash 8. Definitely nothing normal about sparks on any of the Dash 8 series.

Hmmm, you can learn something new every day you’re above ground.

Got to thinking after I posted, I know it’s certainly not “normal”. :blush:
I think the captain might have mentioned new brakes or possibly some other wheel type maintenance and that it’s normal.


I’d be lying if I said I didn’t learn something new in aviation regularly, that’s what I love about aviation!