Air brakes

[Boslandew]

I'm a retired helicopter pilot. Can anyone tell me, during a normal flight in a jet aircraft when everything has gone according to plan and ATC hasn't required anything extra, would use of the airbrakes be a normal part of the descent or would the aircraft decelerate sufficiently just by reducing thrust and eventually with flaps?

[extreme P]

Even with ATC intervention speed brakes are not often required.

[Lord Spandex Masher]

Yet, even without ATC intervention, speed brakes are often required.

[Denti]

Depends on descent planning, proper descent planning with a recent wind profile and speed brakes are not used usually. With the extremely low cost indices we use they're usually not needed until ATC keeps us more than 5000ft high.

[Intruder]

Ideally, the FMS will set the Top of Descent such that all restrictions can be met with idle thrust and no air brakes. Unforecast tailwind or need for engine or wing anti-ice on the descent may eventually require use of air brakes.

Some pilots mitigate the use of air brakes by extending flaps earlier. That often works well when a little extra drag for an extended time will meet the restrictions.

[Piltdown Man]

I'm normally in total agreement with LSM, but this is an exception. I consider that I have "failed" if I have total flexibility in planning my descent and then have to use the brakes. I also try not to use the flaps as brakes and instead let the aircraft bleed off speed in level flight or a gentle descent until I get to the manufacturer's recommended flap deployment speed of Green Dot (or GD+10 in ice).

To put in some numbers, in level flight at low altitudes with a reasonable landing weight the aircraft I fly will decelerate at approx. one knot per second.

[Lord Spandex Masher]

PM, I was only thinking of occasions when there might be an unexpected tail wind (our OFP wind data only goes down to 5000') or you choose to change runways last minute.

I do quite a lot of air tests with the aircraft at light weights and if I didn't use the boards I'd be up there all day

Like you I won't use flaps as brakes, in fact it's prohibited here anyway.

[TypeIV]

The speedbrakes on the 737 aren't very efficient compared to many other transport category jet aircraft, it's mostly used to increase the decent path angle by a degree or two.

If there isn't much traffic, terrain, unexpected route shortenings the speedbrakes are seldomly used unless you're late/bored/competing with a company traffic and descend very fast until a speed restriction to give them the grin at the personnel exit

[con-pilot]

There is an old joke/story about using air/speed/spoilers for descent.

An airliner was given a descent that would require a more than standard rate of descent under normal conditions, because the controller gave the descent later than he should.

The airliner replied that they could not make the descent as quickly and the controller requested.

The controller replied; "Well you have speed brakes, use them."

The captain of the aircraft replied; "I use the speed brakes when I make a mistake, not when you do."


Hope that helps you understand the use of speed/air/spoilers by a pilot.

Now in truth, I used them all the time for all sorts of various reasons.

[DooblerChina]

Most in my airline will use high speeds (greater drag) if high. Our planned descent speed is 250 knots usually so if kept high by ATC, one can dial in 349 knots and the beast drops out of the sky at 6000' down.

Obviously this isn't always possible due to traffic or speed limits so speed brakes are the only option. I'd estimate 1 in 5 approaches use brakes. There's no shame in that what so ever. Using flaps as s brakes is a bit if a no no. Although I have been known to drop the gear at 20000!! After being held vv high into Larnaca by the Turks. That was an interesting one it's not very often I see 9999 high!!

[de facto]

Although I have been known to drop the gear at 20000!! After being held vv high into Larnaca by the Turks. That was an interesting one it's not very often I see 9999 high!!

There is also the :"sorry Sir,no can do" option....few turns in a hold or present position then standard descent...

[JeroenC]

Talking about this, speedbrakes can be used either to decel faster or to increase the descent rate. As can the flaps. As mentioned, flaps are not to be used as brakes. However, do you prefer to decel to flap manouvre speed, pull flaps, and have the increased rate, or do you pull the speedbrake? Personally i use both, depending on the situation with a preference for the former as it is smoother for pax.

[Intruder]

IMO, flaps vs brakes comes down to permanent vs temporary. Since we seldom retract the flaps after extending them, I use them if I believe I'll need at least that much drag all the way to landing. If I think the drag need will be temporary or transient, I use the speedbrakes.