Is it normal for a pilot to use the air brakes at high altitude on an airliner?

Question

Last week I was flying from California to Colorado in a commercial airliner (A320), when high above the rockies the pilot suddenly lifted the air brakes. The plane immediately started losing altitude and was shaking violently, making loud noises. I could clearly see the air brakes up above the wings. The pilot then asked everyone on the plane to stay in our seats. A few minutes later, after we dropped below the cloud cover, he retracted the air brakes, and the plane resumed flying normally as if nothing had happened. This is first time I've ever seen a pilot do that. Is this a normal procedure for an Airbus? What could have caused him to do that? Thanks.

Answer 1

I have never seen that.  I would imagine that he had some information about turbulence that led him to want to drop like a rock. That's just a guess.

Answer 2

Those are not air brakes exactly, but rather spoilers. They simply reduce the lift of the wing by reducing the area of smooth air flow over the wing surface. In essence, he made the wing area smaller, which is why you started to fall like a stone. I've seen this a few times, mostly in places with high turbulence and shear conditions. Hong Kong is especially bad because of surrounding hills and steep glide slope and need to descend rapidly without gaining air speed. The idea is to use the spoilers to perform a relatively rapid descent on a level plane at constant speed under controlled conditions. Without using the spoilers, the craft would dive and accelerate even if he throttled back. Flaps have the opposite effect of spoilers, effectively making the wing area larger.

Answer 3

Could have been anything that the pilot felt he needed to lose height fast for. You could have asked! He may have had severe turbulence report, thunderstorm, traffic (either advised or TCAS warning), or maybe he made an error working out his required rate of descent approaching a landing. Lotsa things.

The air brakes would only be deployed to avoid the aircraft exceeding its VNE (Velocity never exceed) rating. Otherwise rapid descent could exceed this speed, the result can be airframe breakup. So let him use the brakes.

Answer 4

Well that's a new one.

Um, maybe I'm thinking something was wrong with the de-ice system and the pilot had to take care of built up ice and drop altitude at the same time.

I doubt it but that's what comes to my mind.

Answer 5

It's possible he needed to descend quickly to avoid clouds or overshooting his airport.

You mentioned he was flying over the Rockies, possibly he needed to drop the airport after getting over the mountains so he can get at the right descend rate to land at the airport.

Answer 6

When you see speed breaks deploy at high altitude one of two things happened. Either there is an emergency and the crew has to  get down NOW or, as is probably the case on your flight, somebody fvcked up, the controller or the crew. If I'm flying, the speed breaks are for my mistakes, not the controllers. If its his do do, he can work something else out because I won't put my executive passengers that pay me all that money for a smooth ride through what you went through.

Answer 7

i've had to do it from time to time when they change the runway on me and then suddenly i'm more than 10,000ft high. otherwise the best way is to just speed up to increase the descent rate because it's nicer/more comfortable etc etc. it's called 'managing the energy' of the aircraft.

Answer 8

well it could have been a few things:

1. It was an order from atc to drop alltitude immediatley or to slow down very quickly (or in flying lingo expidite). this could be an order to keep the plane from breaching the 1 mile buffer zone around aircraft or to stay out of the wake disturbance.

2. Pilot had a mechanical error while in flight which required hi to drastically slow down. I dunno why he would use the air brakes when cutting the throttle does the trick 99.9% if the time.

My guess is that an unexperieced or disoriented pilot of another plane lost his bearings and drifited into your flight path at the first, higher altitude. Your pilot was immediately ordered to drop down to matian the buffer zone.

the least likely, yet still plauseable answer was it was a military action of some sort that your pilo had to comply to as the airspace from from colorado to cali is filled with restricted air corridors .

but then again he could of been farting arround and hit the lever with his knee. haha

Answer 9

Commercial liners do not have air brakes. The pilot used what are known as 'spoilers'. These destroy the lift on the wings and are used for bringing down the aircraft rapidly for any reason the pilot may have.

Answer 10

I would guess that he was at an altitude where he was on an intercept course with another aircraft.  Air traffic control must have comanded him to drop altitude quickly for some reason.

Astrobuf

Answer 11

It hard to say without knowing more. They may have have mechanical problems.  Those panels that pop up after landing are spoilers.  They are used to disturb the air above the wings thereby "dumping lift".  They function something like an air brake but their main function is to dump lift after landing and to plant to the aircraft firmly on the tarmac during the landing run.  You sometimes see them deploy long before landing to help with the decent but only briefly.  I've notice some large military aircraft like the C-17 use them in a turn to dump lift on one side to help drop the wing.

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Answer 12

Uncommon, but not unusual. There was probably good reason; significant turbulence, traffic, missed decent point...

Answer 13

Its normal, yes. Most heavy aircraft (777+, 330+ type) use it because they need it to be able to slow down when descending. It also enables them to descend at a quicker rate. As for you a320 experience (I assume you were on United going into Denver) it may have been because you needed to evade cumulus cloud cover, and the air breaks enabled them to descend quicker.

Answer 14

Without knowing how high you really were, it could be several things.  It's difficult to make jets descend and slow down at the same time without using spoilers/speed brakes.  Many times it's necessary to meet Air Traffic Control restrictions for procedures or traffic.

One detail that I noticed is that the spoilers were retracted after you dropped below the cloud cover.  It's possible that you were in icing conditions in the clouds, meaning that the temperature and moisture content was such that without having anti-ice equipment turned on, the moisture would freeze on the leading edge of the wings and engine inlets.  To prevent this from happening, the pilots open valves to allow hot air from the engines to be ducted through the wings and engine inlets to keep them hot.  But in order for this equipment to work effectively, the engines have to be at a fairly high power setting.  The only way to keep a lot of power on the engines for anti-ice equipment and to descend at the same time is to use spoilers.  Once below the clouds, it's possible to turn off the anti-ice equipment, reduce the power, and retract the spoilers.

Spoilers do make quite a bit of noise and make the plane shake, especially at higher speeds.  That is normal.  Many pilots try to avoid using spoilers at high speeds for passenger comfort, but in the examples I gave above, operational considerations take priority over passenger comfort.