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sunstar
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Posts: 46
Joined: Thu Jan 24, 2008 3:07 am

737NG SFP spoiler question

Fri Jul 28, 2017 2:10 am

On landing I see the spoilers deploy normally on wheel spin up. I know the deployment is greater than the norm because it's a 800 with the SFP. Why do the spoilers move again to what would seem the normal deployment angle for a 700 or a 737 without the SFP. It happens after the aircraft has slowed down significantly. I've also seen this happen on the 900's which I've heard the sfp is standard.
 
Dardania
Posts: 110
Joined: Tue Jun 07, 2016 11:05 am

Re: 737NG SFP spoiler question

Fri Jul 28, 2017 8:57 am

In anticipation of a go around, so that they're not spoiling so much?
 
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sunstar
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Posts: 46
Joined: Thu Jan 24, 2008 3:07 am

Re: 737NG SFP spoiler question

Fri Jul 28, 2017 10:27 am

Dardania, Thanks for your response but this happens only on the ground.
 
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sunstar
Topic Author
Posts: 46
Joined: Thu Jan 24, 2008 3:07 am

Re: 737NG SFP spoiler question

Fri Jul 28, 2017 5:18 pm

I've posted a clip to better describe what I'm asking. Fast forward to 6min mark

https://m.youtube.com/watch?v=WMkxoCrselY
 
aeropix
Posts: 268
Joined: Mon Jun 06, 2005 2:08 pm

Re: 737NG SFP spoiler question

Fri Jul 28, 2017 8:07 pm

I don't know why exactly but it appears the partial retraction is associated with stowing the thrust reversers? Maybe this will be a clue in your research. Perhaps there is some aerodynamic reason to do so given the chance of airflow or some structural reason or even perhaps it reduces the hydraulic system strain in anticipation of high demand item like flaps retraction.
 
yeelep
Posts: 766
Joined: Mon Apr 04, 2011 7:53 pm

Re: 737NG SFP spoiler question

Sat Jul 29, 2017 2:35 am

The spoilers are mechanically controlled, hydraulically actuated on all NG's. The SFP package adds a electrical control input to solenoid operated valves on the flight spoiler actuators that allows supplemental spoiler travel. After auto speedbrake deployment and as the aircraft decelerates through 60 knots, the power to the solenoid operated valves is removed and the spoilers return to a normal deflection.
 
Dogbreath
Posts: 207
Joined: Fri Mar 28, 2008 8:49 am

Re: 737NG SFP spoiler question

Sun Jul 30, 2017 8:31 am

I absolutely agree 100% with yeelep.

This information straight from the 737-800 AMM:

"On the ground during auto speedbrake operation, a solenoid valve in the flight spoiler PCU activates to allow supplemental spoiler travel. Flight
spoilers 2, 3, 10, and 11 move up a maximum of 56 degrees. Flight spoilers 4, 5, 8, and 9 move up a maximum of 65 degrees.

After auto speedbrake deployment and as aircraft decelerates, the solenoid valve command is removed once speed drops below 60 knots causing
spoilers to move to a normal deflection."
Truth, Honour, Loyalty
 
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767333ER
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Re: 737NG SFP spoiler question

Sun Jul 30, 2017 7:30 pm

This is something I have always wondered too, but it's an interesting way to make such a feature work. The max obviously functions differently with its FBW spoilers.
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