63
votes
Accepted
Why does one of the Boeing 777's spoilers deploy differently from the rest?
Roll control is provided by 2 flaperons, 2 ailerons, and 14 spoilers.
Spoiler panels 4 and 11 are controlled mechanically rather than electrically. They are driven directly from control wheel ...
- 37.5k
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 ...
- 54.3k
29
votes
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 ...
- 9,599
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.
...
- 6,565
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 ...
- 20.7k
25
votes
Accepted
How frequent is the use of spoilers during descent?
Very frequent.
Modern airliners are certainly fairly slippery, but it's not so much that they're super-gliders that we can't wrestle down onto the ground.
It's more a function of busy airspace than ...
- 10.4k
21
votes
Accepted
Why do modern jetliners provide Thrust Reversers at all in their design decisions?
There are a couple of reason for the presence of thrust reversers:
To reduce wear on the brakes.
To provide a margin of safety (for example in wet conditions).
In 1995, NASA carried out a survey ...
- 100k
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 ...
- 61.3k
18
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 ...
- 49.8k
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 ...
- 126k
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, ...
- 37.5k
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 ...
- 100k
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
Accepted
Should spoilers and reverse thrust be deployed before nose gear touches down?
It depends on the aircraft (and conditions). In some aircraft like the MD-11, the deployment of ground spoilers causes a nose up pitching moment- in such a case, the spoilers should be deployed after ...
- 100k
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 ...
- 1,338
9
votes
Accepted
What are the differences between air brakes, spoilers and lift dumpers?
Air brakes increase drag with little change in lift. The following image shows the air brake being used in BAe 146
"Eurowings bae146-300 d-aewb arp" by Adrian Pingstone - Own work. Licensed under ...
- 100k
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
8
votes
Why do modern jetliners provide Thrust Reversers at all in their design decisions?
The added complexity is a valid point. However, the additional braking option provides enough benefits to offset the added cost. Also, it is not accurate that credit is never given for reverse thrust. ...
- 71.8k
8
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 ...
- 1,762
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, ...
- 126k
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 ...
- 19.4k
6
votes
Accepted
What is the purpose of proximity sensors on hydraulic systems?
A proximity sensor is any sensor that detects whether there is something in its proximity (within specified distance).
There are many kinds of proximity sensors (optical, magnetic, capacitive etc.) ...
- 56.2k
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)
- 37.5k
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 ...
- 56.2k
Only top scored, non community-wiki answers of a minimum length are eligible