58
votes
Accepted
Do airplanes need brakes in the air?
What you saw is called a speed brake, which is one of the functions of the spoilers. From the Boeing 737 NG FCOMv2 (9.20.5 Flight Controls - System Description):
Flight Spoilers
Four flight ...
- 58.3k
28
votes
Accepted
For large commercial jets is it possible to land and slow sufficiently to leave the runway without using reverse thrust or brakes
it's possible for jetliners under typical loading scenarios... to come to a slow enough speed to exit the runway just by using spoilers, full flaps and normal friction (air and tyres) i.e. no brakes ...
- 16k
26
votes
Why can't wing-mounted spoilers be used to steepen approaches?
They can. The Airbus A318 and Embraer E190 both do this in steep approach mode. You can see spoilers extended in this video of a A318 landing and a similar approach in an E190 at London City Airport.
...
- 8,293
26
votes
How can you move the thrust reverser to another part of the airplane?
It sounds like your professor doesn't know much about the mechanics of thrust reversers. They are attached to the exhaust end or to a fan shroud extension of an engine because that's where the air ...
- 22.2k
20
votes
Accepted
Is the location of an aircraft spoiler really that vital?
Surfaces sticking out ahead of the Centre of Gravity act in an unstabilising manner: any dissymmetry will want to amplify itself. A dart thrown with the feathers first is in an unstable equilibrium ...
- 63k
17
votes
For large commercial jets is it possible to land and slow sufficiently to leave the runway without using reverse thrust or brakes
No, in the general case it isn't even close to possible.
You land a 60-ton aircraft at 120 mph, and it has to slow to (let's say) 30 mph in the space of (being generous) 2 miles, with no braking? No ...
- 53.8k
16
votes
Why can't wing-mounted spoilers be used to steepen approaches?
The main issue is the need to manage the vertical sink rate of your 100000+ lb aluminum trash can and the risks of hard landings.
Although they are often called speed brakes, the main effect of ...
- 136k
16
votes
Accepted
Do all 767-200s have speedbrakes that deploy automatically upon touchdown?
All B757 and B767 aircraft have speedbrakes that can be deployed automatically. But you need to manually arm them first. You also need weight on wheels(truck tilt) and both thrust levers at idle, ...
- 38k
13
votes
Accepted
Why would the Speedbrake be required for such a long time on approach?
There are two reasons I can think of off the bat:
Its possible the controller asked them to hold a slow speed due to increased traffic ahead. The brakes may have been deployed to match the speed ...
- 102k
12
votes
Do airplanes need brakes in the air?
Though your photos refer to a specific commercial airliner, your question is general, so I will describe a more specialized use case for speed brakes. A glider (also known as a sailplane) has no ...
- 221
11
votes
Why would the Speedbrake be required for such a long time on approach?
Those are spoilers...not speed brakes. They do increase drag, but their primary function is that they kill lift. They allow the aircraft to lose altitude rapidly without pointing the nose downhill ...
- 1,388
9
votes
Accepted
Why is the speedbrakes rate of retraction 25 seconds when used at speeds greater than 315 knots/.75 Mach on the A320?
Please read the entire answer to understand the matter even if the answer goes a bit beyond the question.
On the A320 wings you have panels that may open upward and that could be used to fulfill 3 ...
- 1,807
9
votes
Accepted
Is a plane stalled during landing rollout?
Stall for a wing is defined as:
a reduction in the lift coefficient generated by a foil as angle of
attack increases. This occurs when the critical angle of attack of
the foil is exceeded. (Wikipedia,...
- 467
7
votes
Could flaps be raised upward to serve as spoilers / lift dumpers?
One reason is that any device you want to use as a lift dumper needs to be able to be instantly retracted and this is really difficult to do with a flap. On an airliner when the lift dumpers come up, ...
- 136k
7
votes
How can you move the thrust reverser to another part of the airplane?
You can't really move the thrust reversers to another part of the airplane (they have to be in the airstream of the engine in order to have any thrust to reverse,) but you certainly can have their ...
- 19.6k
6
votes
Accepted
Why can't wing-mounted spoilers be used to steepen approaches?
Spoilers are called spoilers, because they work by spoiling lift.
To slow the aircraft, or make it descend faster, it needs to dissipate the energy and that means increase drag. Disrupting the ...
- 56.6k
6
votes
Could flaps replace spoilers by deflecting more than 90°?
The BAe Jetstream 31 is one of a few aircraft that had a "lift dump" flap position after touchdown. It is not "more than 90°", but it is quite effective.
(Jetstream 31 Lift Dump in action; YouTube)
- 38k
6
votes
Accepted
Why are the spoilers used as the backup controls instead of ailerons on the Boeing 777?
The B777 is a high subsonic aeroplane, and at high airspeeds the ailerons remain stationary because wing twist may cause aileron reversal.
By using inboard spoilers as mechanical backup roll control ...
- 63k
6
votes
Do airplanes need brakes in the air?
As you can see on the photo, the flaps are slightly extended, allowing the aircraft to fly at a lower airspeed. This is common for aircraft to do during an approach, to keep a constant distant between ...
- 5,552
5
votes
Accepted
On the 737NG, after deployment of spoilers automatically after landing, do the spoilers automatically go back down?
The spoilers on the 737 after auto deploy will re-stow automatically based on TLP (thrust lever position). This is a function for a rejected landing which will automatically lower the boards & ...
- 66
5
votes
Why would the Speedbrake be required for such a long time on approach?
Speed brakes are often used on aircraft that are very clean (i.e., have very low drag), and, as a result cannot descend at a steep enough glide angle even with power at idle to satisfy minimum descent ...
- 6,175
5
votes
Why do some aircraft (e.g. Avro RJ85) have rear-mounted air brakes?
They have them mounted at the rear fuselage because they work better, and because there isn't a set of stabilisers mounted there: the stabilisers are mounted on top of the vertical tail, in a T-tail ...
- 63k
5
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Why do some aircraft (e.g. Avro RJ85) have rear-mounted air brakes?
The Avro RJ100 does have something on its wings- three spoilers on each, though these act exclusively as lift dumpers after touchdown (and another two for roll control).
It is perfectly possible to ...
- 101k
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