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Spoilers armed after take-off?

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Spoilers armed after take-off?

Old 22nd Aug 2009, 22:47
  #1 (permalink)  
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Join Date: Sep 2007
Location: Paris, France
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Spoilers armed after take-off?

Is there a reason why you might want spoilers armed after take-off (as opposed to disarming them as soon as you leave the ground)? The aircraft in question is an A320. I've seen comments in different forums by pilots to the effect that some disarm the spoilers when they raise the gear, others disarm them as they retract flaps. Is there an advantage to having spoilers armed during the initial climb after take-off?

I always thought spoilers were just for slowing down, so you'd use them after landing or maybe during a descent to slow down and descend more quickly. If you're trying to climb, though, you wouldn't want any risk of spoilers deploying—right? Or are there emergencies that could come up that would require you to have the spoilers armed and ready?

Then I started wondering why the spoilers would be armed in the first place, but perhaps you'd arm them to stop faster for an aborted take-off (?). And wouldn't the spoilers disarm themselves when not needed on some aircraft (especially Airbus)?

I guess I'm confused as to why you would want the spoilers armed at any time after take-off. If they were armed and suddenly deployed, you'd be in quite a predicament … or wouldn't you?
AnthonyGA is offline  
Old 22nd Aug 2009, 23:13
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Join Date: Mar 2009
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Ground spoilers are armed before TO for automatic extension in case of an RTO. It is important to dump any lift for the wheel brakes to function optimally. Once airborne, it matters little when they are disarmed. It is down to specific airline SOPs as to when they are to be disarmed.

However, in order to use spoilers in flight they need to be disarmed. But then that is not a concern untill you need to reduce speed faster than the drag of the aircraft is capable of. That is usually during the descend and/or approach.

Auto extension will only happen when a certain logic is satisfied. Usually all throttles at idle and main gear wheel speed above a certain speed. Spoilers will therefore not extend automatically in flight.
One Outsider is offline  
Old 23rd Aug 2009, 01:00
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Okay, thanks!
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Old 23rd Aug 2009, 01:49
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some disarm the spoilers when they raise the gear, others disarm them as they retract flaps
Some operators follow the Airbus SOP of: after raising gear, the spoiler lever is pushed back down to the disarmed position.
This then allows the spoilers to be deployed manually at any time.
(As you are probably aware, with the spoiler lever raised/armed, the lever will not physically move rearwards to deploy spoilers manually).

IIRC, some operators found that when pilots were ordering gear up, the natural follow on was for the other pilot to select gear up, then the hand would go down to the spoiler lever and variously push/lower/bonk/thump the top of said lever, and on ocassions, an over exuberant thump continued into a partial spoiler deployment. Clearly not ideal at 300' climbing out on a dark night max weight TO.

Consequently, some operators decided that as there is no rush to disarm the spoilers, and there is no downside to leaving them armed, that they would do it at a safer height once the flaps were retracted.

Hope that explains the minor difference between operators.
mephisto88 is offline  
Old 23rd Aug 2009, 04:28
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Join Date: Mar 2000
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Disarming...arming...spoilers?
One would have thought that it would be done completely automatically on new(er) types.

Of course, it is done on one older type, in fact, the first truly 'automatic' airplane...designed over thirty seven years ago.

TriStar.
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