question about "ground spoilers"

[aibiria]

Hi again!!

Okay, here is the question. Before landing ( with a320 ) on the airbus checklist you must make sure that you swich the spoilers to ground
position. Okay, fine , I've been checking this link about the ground spoilers and I don't really get it.
Why is that? What exactly the spoilers do? Do they work as speed brakes so they actually work speeding down the aircraft during roll
down after landing, but how about the "autobrakes" positions?, which in Airbus are three. LOW, MED, MAX, I don't actually remember
Boeing but it's actually very similar.
So what the hell do they do?.

The autobrakes work on the weels right?
fine

so the ground spoilers work on the speed brakes during landing.
Is that right?
So basically, if you don't swich them on ground position they won't deploy. Am I right?


Will you please help me here?

[Dutch64]

Not sure about 'ground position' but you have to arm them indeed so they will deploy automatically after touchdown. This way the aircraft will slow
down (together with reverse thrust). You cannot just use your wheel brakes immediately after landing because the speed is still to high then (anyone,
correct me if 'm wrong please)

[silo]

I never flew an Airbus but Dutch64 is definetly right in saying that you need to arm them so that they deploy as soon as you touch down.
And probably the "arm" in the boeing is the "ground" in an airbus.
What the spoilers do is not so much to act as airbrakes once on the ground, but more as a lift breaker. They disrupt the regular flow of air on the wing and reduce lift so that more weight is shifted to the wheels, which in turn gives more braking power.
Regarding autobrakes, it really depends on how long the rwy is, what conditions (wet, dry, etc..), but I remember reading on another post
that usually you would use the low setting. Here we need SWAFO....



Post Edited ( 09-22-05 18:27 )

[SWAFO]

Unfortunately I can't help with autobrake questions. At SWA, we simply don't use them. I know HOW they work, I just don't know how TO
work them.



I don't know about Airbus' and arming ground spoilers or whatever. With my 737, I know I have flight spoilers, and ground spoilers. All of
them deploy on landing when I place the lever to the "ARMED" position. That's all I know... lol.

[AeroJim]

auto brakes and spoilers kind of work together as far as i understand, i mean these last 2 posts say it all I'll try and put it together, when
you land the spoilers automatically deploy and help shift weight to the wheels, than the autobrake begins to kick in (not sure what KIAS)
and helps slow down the plane, i believe auto brakes are there to kind of help i know a lot of airliners dont use them, and in others that
do the FO usually tries to beat the auto brakes to the punch and apply them manually.

[aibiria]

Thanks guys for your help. I was just wondering about it!

[DanSteph]

SWAFO wrote:
Unfortunately I can't help with autobrake questions. At SWA, we simply don't use them.

that's strange.. any reason for that ? (avoid uncomanded deploying near ground for example ?)

I thought that as said Silo it can breake lift and thus avoid bouncing ?

I personnaly always use them as I love to see them automatically deploying when I replay my landings.

Dan



Post Edited ( 09-23-05 04:19 )

[olseric]

Ah yes, the Airbus questions...I guess I'll field this one...

Okay, here is the question. Before landing ( with a320 ) on the airbus checklist you must make sure that you swich the spoilers to
ground position. Okay, fine , I've been checking this link about the ground spoilers and I don't really get it.

Ground position simply means retracted, un-armed. If you set the spoilers to auto-arm, they will deploy when you're on the ground. In
reality, as discussed several times, it's detected by the sudden "stop" when impacting the runway, however, FS doesn't work that way.

Why is that? What exactly the spoilers do? Do they work as speed brakes so they actually work speeding down the aircraft during
roll down after landing,

As stated already, they are merely "lift dumpers." They are situated (in MOST aircraft) on top of the wing and deploy vertically to disrupt the
flow of air over the top of the wing. In flight, they can be used incrementally as well to slow the aircraft.

but how about the "autobrakes" positions?, which in Airbus are three. LOW, MED, MAX, I don't actually remember
Boeing but it's actually very similar. So what the hell do they do?.

Well, there's reality, and then there's FS. In reality, the autobrakes on the A320 are supposed to engage below 60-80 kts. They provide a
constant, controlled amount of braking pressue on the tires after the reverse thrust has been disengaged. The three, actually four,
settings on the bus are as follows: RTO is rejected take off. You set that on take off and if for some reason you abort take-off, they will
engage to help stop the aircraft. Min is for most normal landing conditions. Med is for reduced braking action because of wet runways,
etc. Max should normally not be used.

so the ground spoilers work on the speed brakes during landing. Is that right? So basically, if you don't swich them on ground
position they won't deploy. Am I right?

The bus has one set of spoilers attached to the top of each wing. They are an airbrake if you will, not a wheel brake. There are no "air
spoilers" vs "ground spoilers." You're referring to postions of arming basically.

As for your question regarding "ground position," as I previously stated, retracted, un-armed. That simple.