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Topic: Speedbrake
Username: Novice
Posted 2012-10-29 13:26:19 and read 4989 times.

Speedbrake
When the gear is lowered the speedbrake will be armed by the pilot in the left-hand seat. If the speedbrake is in use prior to being armed for landing the speedbrake lever must be moved to the down detent, the light checked out, and then moved to the armed position.

What does it mean by 'armed' and 'armed position'

Thanks

Topic: RE: Speedbrake
Username: tdscanuck
Posted 2012-10-29 13:46:56 and read 4977 times.

Quoting Novice (Thread starter):
What does it mean by 'armed' and 'armed position'

Most aircraft have an auto-speedbrake function that extends the spoilers on touchdown (typical signals are wheel spin-up, strut compression, or truck tilt). This gets weight onto the wheels more quickly and improves stopping performance. To allow the auto-extension function to "fire" you place the speedbrake handle in the "armed" position. This doesn't move the spoilers at all but gets the handle out of the "Down" detent and annunciates "Spoilers armed" or similar verbiage to the flight crew (this is usually part of the approach checklist).

On some aircraft the spoilers will automatically deploy even if the handle is in the down position, to guard against a flight crew error, but you're still supposed to consciously put the the speedbrakes to "armed".

Tom.

Topic: RE: Speedbrake
Username: BoeingGuy
Posted 2012-10-29 15:29:29 and read 4904 times.

Quoting tdscanuck (Reply 1):
On some aircraft the spoilers will automatically deploy even if the handle is in the down position, to guard against a flight crew error, but you're still supposed to consciously put the the speedbrakes to "armed".

I'm not aware of any Boeing airplanes that do this only with weight on wheels without having deployed the thrust reverser levers.

Topic: RE: Speedbrake
Username: Pihero
Posted 2012-10-29 16:05:11 and read 4880 times.

Quoting BoeingGuy (Reply 2):
I'm not aware of any Boeing airplanes that do this only with weight on wheels without having deployed the thrust reverser levers.

I don't know of any airplane that requires thrust reverser deployment for extending the speedbrake : I flew the 731, 2 and 5 and 741, 2, 3, and 4, and basically the requirement for auto speedbrake was weight on wheels, radAlt below 10 ft, and throttles (1 and 3 on the 747IIRC) at idle... One would add wheel spin up. The 744 would retract the speedbrakles if the throttles were pushed forward away from idle.
I would think that all Boeing airliners show this feature, or something very similar.
If you think of it, the speedbrakes should be deployed as ear(ly as possible after touch-downj as that is where they are at their maximum efficiency.

Topic: RE: Speedbrake
Username: fr8mech
Posted 2012-10-29 16:16:48 and read 4867 times.

Quoting Pihero (Reply 3):
I don't know of any airplane that requires thrust reverser deployment for extending the speedbrake : I flew the 731, 2 and 5 and 741, 2, 3, and 4, and basically the requirement for auto speedbrake was weight on wheels, radAlt below 10 ft, and throttles (1 and 3 on the 747IIRC) at idle... One would add wheel spin up.

Thrust reverser is not a pre-requisite, but pulling up on the thrust reverser (i don't recall which, but I would assume the left most) will raise the spoiler handle out of the down detent and initiate an autospoiler deployment.

I'm not aware of any Boeing uses wheel-spin up, though I could be mistaken. B727 used the pogo stick on the left gear, B741 & 2, B757 & B767 use tilt or tilt pressure. Would need to look at the B744.

Topic: RE: Speedbrake
Username: BoeingGuy
Posted 2012-10-29 16:57:48 and read 4853 times.

Quoting Pihero (Reply 3):
I don't know of any airplane that requires thrust reverser deployment for extending the speedbrake

That's not at all what I stated or meant. The previous poster said (or implied) that some airplanes will deploy the speedbrakes automatically at weight-on-wheels even if not armed. I stated that I'm not aware of any Boeing model that automatically deploys the speedbrakes if not armed. However, I stated that the speedbrakes will also deploy automatically when the thrust reverse levers are deployed. I didn't state that you must deploy reverse thrust in order to deploy the speedbrakes.

[Edited 2012-10-29 16:58:36]

Topic: RE: Speedbrake
Username: Pihero
Posted 2012-10-29 17:32:24 and read 4830 times.

Quoting fr8mech (Reply 4):
I'm not aware of any Boeing uses wheel-spin up,

If my memory still serves me ok, wheel spin-up is / was a requirement for the 731, 2and 5... A friend of mine told me the feature is still on the 8.
The 744 is like the earlier 747s : Tilt is used in lieu of wheel spin-up.

Quoting BoeingGuy (Reply 5):
I didn't state that you must deploy reverse thrust in order to deploy the speedbrakes.

Sorry, English isn't my mother tongue.

Topic: RE: Speedbrake
Username: Larshjort
Posted 2012-10-29 17:36:22 and read 4826 times.

Quoting BoeingGuy (Reply 2):
Quoting tdscanuck (Reply 1):On some aircraft the spoilers will automatically deploy even if the handle is in the down position, to guard against a flight crew error, but you're still supposed to consciously put the the speedbrakes to "armed".
I'm not aware of any Boeing airplanes that do this only with weight on wheels without having deployed the thrust reverser levers.

On the CRJ-100/200 you have a 3-way ground lift dump switch

Man ARM
Auto
Man DISARM

In auto position the system become armed when you have >45kt wheelspeed and any throttle or N1 fan speed >79%.

When system is armed it requires left+right engine idle and 2 of the following 3 conditions:

WOW 2 left and 2 right or 1 left and 1 right
RAD alt 16kt

Topic: RE: Speedbrake
Username: tdscanuck
Posted 2012-10-29 18:19:21 and read 4810 times.

Quoting BoeingGuy (Reply 5):
The previous poster said (or implied) that some airplanes will deploy the speedbrakes automatically at weight-on-wheels even if not armed. I stated that I'm not aware of any Boeing model that automatically deploys the speedbrakes if not armed.

I think you're mixing up two different things I said. Autospeedbrakes will fire from the armed position at one of the triggers (varies by aircraft). Separately, they can fire from down position even if not armed when other criteria are met.

I did not mean to imply that they will always fire from the down position with no other action.

Tom.

Topic: RE: Speedbrake
Username: CCA
Posted 2012-10-29 18:55:04 and read 4784 times.

Just to add some info, when lifting the 747 reverse thrust levers (#2 or #4 from memory) they mechanically lift the speedbrake lever out of the down detent (if not armed) and into the armed detent, if the conditions for auto deployment are satisfied then the speed brake actuator will push the lever to the extend position.

What I'm trying to add is reverse thrust is not a auto speedbrake condition but a fail safe for forgetting to arm them.

I'm not sure what other Boeings do or other aircraft types.

Topic: RE: Speedbrake
Username: musang
Posted 2012-10-30 07:11:31 and read 4569 times.

I'm not aware of any Boeing uses wheel-spin up, though I could be mistaken.[/quote]

From our 737 Classic ops manual:

Landing - AUTO speedbrake system requires

a) Speedbrake lever in ARMED position,

b) SPEEDBRAKE ARMED light lit,

c) both thrust levers idle,

then -----

1) at main gear spin up more than 60 knots the speedbrake lever moves to UP and the FLIGHT spoilers (2 panels each side) deploy,

2) at right main leg compression, the GROUND spoilers (3 panels each side) deploy.

So its a two stage process unless the wheel spin signal is missed, in which case the strut compression triggers the speedbrake lever to UP and all 10 spoilers deploy.

Quoting Pihero (Reply 3):
requires thrust reverser deployment for extending the speedbrake

For a rejected take-off, speedbrake is triggered by:

a) main wheels spun up to 60 knots

b) thrust levers to idle AND "reverse levers positioned for reverse thrust" (quote).

The speedbrake lever moves to UP and all 10 spoilers deploy.


[quote=fr8mech,reply=4]Thrust reverser is not a pre-requisite, but pulling up on the thrust reverser (i don't recall which, but I would assume the left most) will raise the spoiler handle out of the down detent and initiate an autospoiler deployment.

So if the speedbrake lever is unarmed, it will deploy automatically on a rejected take-off, but not on landing.

Regards - musang

Topic: RE: Speedbrake
Username: Jetlagged
Posted 2012-10-30 08:01:54 and read 4542 times.

Quoting CCA (Reply 9):
Just to add some info, when lifting the 747 reverse thrust levers (#2 or #4 from memory) they mechanically lift the speedbrake lever out of the down detent (if not armed) and into the armed detent, if the conditions for auto deployment are satisfied then the speed brake actuator will push the lever to the extend position.

The reverse levers lift the speedbrake lever mechanically but they don't move it back into the normal ARM position (which requires a small movement aft). The actuator is instead activated by microswitches operated by the reverse levers and as the lever has been lifted out of its detent the actuator can now move it.

Topic: RE: Speedbrake
Username: 71Zulu
Posted 2012-10-31 12:25:35 and read 4193 times.

The ERJ family of regional jets will raise the spoilers automatically regardless of armed position or not, as long as the wheel speed is above about 25 knots, and thrust lever position below 50 degrees.

A fast taxi out for departure on an ERJ will raise the spoilers, like this one:

http://youtu.be/J-C5leIxSos

Topic: RE: Speedbrake
Username: bueb0g
Posted 2012-10-31 12:36:38 and read 4185 times.

Quoting 71Zulu (Reply 12):

The ERJ family of regional jets will raise the spoilers automatically regardless of armed position or not, as long as the wheel speed is above about 25 knots, and thrust lever position below 50 degrees.

Can this be turned off for touch and go's?

Topic: RE: Speedbrake
Username: BoeingGuy
Posted 2012-10-31 15:25:40 and read 4118 times.

Quoting bueb0g (Reply 13):
Quoting 71Zulu (Reply 12):

The ERJ family of regional jets will raise the spoilers automatically regardless of armed position or not, as long as the wheel speed is above about 25 knots, and thrust lever position below 50 degrees.

Can this be turned off for touch and go's?

Presumably during the takeoff roll portion of the touch and go (or a very late go-around due to a runway incursion, say) the thrust lever position will be well above 50 degrees.

Topic: RE: Speedbrake
Username: bueb0g
Posted 2012-11-02 05:27:49 and read 3775 times.

Quoting BoeingGuy (Reply 14):
Presumably during the takeoff roll portion of the touch and go (or a very late go-around due to a runway incursion, say) the thrust lever position will be well above 50 degrees.

Yep, but I thought during the whole T & G, even the touchdown part, you don't want spoilers deploying at all?

Topic: RE: Speedbrake
Username: tdscanuck
Posted 2012-11-02 17:48:59 and read 3648 times.

Quoting bueb0g (Reply 15):
Yep, but I thought during the whole T & G, even the touchdown part, you don't want spoilers deploying at all?

When we do touch-and-goes, the PF just usually holds the speedbrake handle down. There's a slipper clutch in the auto-extend mechanism so you can hold it down against the motor.

Tom.

Topic: RE: Speedbrake
Username: Novice
Posted 2012-11-13 14:00:58 and read 3323 times.

Quoting tdscanuck (Reply 1):
"Down" detent and annunciates "Spoilers armed" or similar verbiage to the flight crew

What the difference between down detent and armed?

Quoting Pihero (Reply 3):
One would add wheel spin up

What is wheel spin up? I presume it means the actual speed of your wheels on the ground

Quoting Pihero (Reply 6):
Tilt is used in lieu of wheel spin-up.

What does tilt mean?

Topic: RE: Speedbrake
Username: rwessel
Posted 2012-11-13 14:16:50 and read 3323 times.

Quoting Novice (Reply 17):
What is wheel spin up? I presume it means the actual speed of your wheels on the ground

Exactly - when the wheel contacts the ground, it will go from approximately zero RPM, to a much higher value. That's used to detect that the aircraft is really on the ground.

Quoting Novice (Reply 17):
What does tilt mean?

For an aircraft with a multi-axle bogie, you can use the tilt of the bogie to determine that the aircraft is touching the ground. In the air the bogie usually hangs with one end or the other down, that angle changes when it hits the ground.

Other mechanisms are used to detect being one the ground as - for example measuring the compression of the strut.

Topic: RE: Speedbrake
Username: Fabo
Posted 2012-11-13 14:17:27 and read 3323 times.

Quoting Novice (Reply 17):
What is wheel spin up? I presume it means the actual speed of your wheels on the ground

Basically, that there is some gadget that tells the computer if the wheels are turning or not. Wheels are stationary when on approach, they only start to spin after touchdown.

Quoting Novice (Reply 17):
What does tilt mean?

The wheen bogies, having a cart of more wheels, are naturally tilted - they "hang" at an angle, forward or backward. In this case, there is a thingamajig, that detects when the bogies are no longer tilted, but horizontal - when the plane lands on them, it presses them into position.

Topic: RE: Speedbrake
Username: tb727
Posted 2012-11-13 14:33:46 and read 3323 times.

Quoting Novice (Reply 17):
What the difference between down detent and armed?

In the detent, it's exactly that, it's pushed all the way forward and a little metal tooth on the handle slides into a little spot for it. Armed, at least on what I have flown, is the handle is pulled up out of the detent and slightly back into the "ARM" band on the speedbrake position band. An amber light saying "Speedbrake Armed" light annunciates letting the pilot know they are armed.

Topic: RE: Speedbrake
Username: tdscanuck
Posted 2012-11-13 17:50:50 and read 3323 times.

Quoting Fabo (Reply 19):
Basically, that there is some gadget that tells the computer if the wheels are turning or not. Wheels are stationary when on approach, they only start to spin after touchdown.

One of the cool things about using wheel spin-up is that it's a "free" measurement...you already had to sense it for the anti-skid system to work so you don't need any extra sensors.

Tom.

Topic: RE: Speedbrake
Username: Max Q
Posted 2012-11-14 21:58:13 and read 3322 times.

Quoting tdscanuck (Reply 16):

When we do touch-and-goes, the PF just usually holds the speedbrake handle down. There's a slipper clutch in the auto-extend mechanism so you can hold it down against the motor.

Not sure what kind of Aircraft you are using as an example here Tom but that would not be necessary while doing touch and goes on the 75/67.


Unless you arm the speedbrake the spoilers will not extend on touchdown, they would of course if you deployed reverse but you wouldn't be doing that on a touch and go anyway.

Quoting BoeingGuy (Reply 5):

That's not at all what I stated or meant. The previous poster said (or implied) that some airplanes will deploy the speedbrakes automatically at weight-on-wheels even if not armed. I stated that I'm not aware of any Boeing model that automatically deploys the speedbrakes if not armed. However, I stated that the speedbrakes will also deploy automatically when the thrust reverse levers are deployed. I didn't state that you must deploy reverse thrust in order to deploy the speedbrakes.

Exactly.


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