Uncommanded Spoilers deployment at touchdown

[KirMi]

I thought that this was all long (some hotfixes ago) gone:

http://forums.x-pilot.com/forums/topic/9716-uncommanded-spoilers-deployment-at-touchdown/

But on last flight all spoilers poping out on touchdown again, without arming them before.
They will come out each time I pull the reversers.

???

-Michael

 

[jimbim]

As far as I know, the spoiler will deploy automatically if reverse thrust is toggled. Maybe I am wrong... I'm sure someone will know it :-)

 

Sebastian

[mgeiss]

That's right:

 

[frumpy]

Handbook says:

"All spoiler panels will extend automatically if takeoff is rejected and the thrust
reverse levers are positioned for reverse thrust. Wheel spin-up (60 kts.) must
have occurred on any two main wheels in order for the automatic extension to
take place."

As I understand, it does not specify what will happen if you land without arming

the speedbrake. But why would you want to do that anyway?

[KirMi]

I think that is true, but not right ;-)
We should call it: MSS (Mad Spoiler Syndrom)
-Michael

[KirMi]

21 minutes ago, frumpy said:

Handbook says:

"All spoiler panels will extend automatically if takeoff is rejected and the thrust
reverse levers are positioned for reverse thrust. Wheel spin-up (60 kts.) must
have occurred on any two main wheels in order for the automatic extension to
take place."

As I understand, it does not specify what will happen if you land without arming

the speedbrake. But why would you want to do that anyway?

Hi frumpy,

last time I really want the spoilers to stay in was for practicing some Touch and Go's.
This time I only forgot to arm spoilers and set the autobrakes, probably because I've got drunk by LH's famous "Bordeaux" ;-)
You cannot overestimate the importance of checklists especially for drunken pilots!
-Michael

[frumpy]

Real men don't need no checklist!

[Tchou]

You pull out reversers when practising touch&go ?

[tkyler]

If you go into reverse and wheelspin is > 60 (on the ground), the spoilers will deploy (a few other caveats for RTO though), the plane thinks you are wanting to stop...and if you're going over 60knots and have the reversers actuated (not necessarily fully deployed), then its a good bet a pilot wants to stop.  The whole concept of "arming" for landing is simply a way to get the spoilers out as quickly as possible as it takes precious runway real estate before you can get the spoilers out from reverser actuation alone.
 

If you are wanting to do touch and gos, then simply advancing the throttles past 40% of travel for the "go takeoff" will cause the spoilers to to retract automatically...again, because the plane now thinks you are wanting to takeoff (lots of throttle and increasing wheelspin)

-tkyler

Edited June 6, 2016 by tkyler

[KirMi]

13 minutes ago, Tchou said:

You pull out reversers when practising touch&go ?

Not for Touch and Go!
No reversers, no brakes, no alcohol!

[KirMi]

14 minutes ago, tkyler said:

If you go into reverse and wheelspin is > 60 (on the ground), the spoilers will deploy (a few other caveats for RTO though), the plane thinks you are wanting to stop...and if you're going over 60knots and have the reversers actuated (not necessarily fully deployed), then its a good bet a pilot wants to stop.  The whole concept of "arming" for landing is simply a way to get the spoilers out as quickly as possible as it takes precious runway real estate before you can get the spoilers out from reverser actuation alone.
 

If you are wanting to do touch and gos, then simply advancing the throttles past 40% of travel for the "go takeoff" will cause the spoilers to to retract automatically...again, because the plane now thinks you are wanting to takeoff (lots of throttle and increasing wheelspin)

-tkyler

...why do the plane have to "think" to find out what the pilot wants, when it can "look" at the autobrake switch?

[tkyler]

58 minutes ago, KirMi said:

why do the plane have to "think" to find out what the pilot wants, when it can "look" at the autobrake switch

This is simply a difference of perception in using words A over words B

Look is the "input",  "think" is the logic that drives the output.  It does no good to take in some knowledge if you don't act on that knowledge.  The system may very well be engineered to "look" at the autobrake switch (I'd have to look at the schematics).....at which point it then deployes the spoilers with additional conditions...but the engineer who designed it......he has to ask, 'IF autobrake switch on landing, THEN deploy the spoilers"....well he is the one "thinking" and decided what to do....its just a convenient choice for me to use the word 'think'

-tkyler

Edited June 6, 2016 by tkyler

[Morten]

1 hour ago, KirMi said:

...why do the plane have to "think" to find out what the pilot wants, when it can "look" at the autobrake switch?

Some landings are done without autobrake as well..manual braking... so "looking" at the AB switch is not a good idea..

[KirMi]

OK...let me clarify that. I talk about the following (abnormal) landing setup:

autobakes = 0,
speedbrake = down detent,
flaps = 30

On touchdown the spoilers staying in (as I expect).
After touchdown (rollout), applying reverse thrust, all spoilers will come up (automation surprise).

In 2014 I had the chance to fly a couple of approaches (incl. Touch and Goes) in a 737NG full-flight sim at LH/Berlin, but I can't remember such an behavior?

-Michael
 

[poodster]

8 minutes ago, KirMi said:

OK...let me clarify that. I talk about the following (abnormal) landing setup:

autobakes = 0,
speedbrake = down detent,
flaps = 30

On touchdown the spoilers staying in (as I expect).
After touchdown (rollout), applying reverse thrust, all spoilers will come up (automation surprise).

In 2014 I had the chance to fly a couple of approaches (incl. Touch and Goes) in a 737NG full-flight sim at LH/Berlin, but I can't remember such an behavior?

-Michael
 

Spoilers are Coming up because you applied reverse thrust. 

"Flight spoilers (2 -1/2/3/4/500; 4 -NG's) augment the ailerons and are powered by hydraulic system A (inboard) & B (outboard). Spoilers will continue to operate with speedbrake deployed.

Ground spoilers are also from hydraulic system A.

Only the outboard flight spoilers are powered by hydraulic sys B

On landing, if armed, all spoilers will deploy when the thrust levers are at idle and any two wheels have spun up or right gear is compressed. If not armed, the speedbrakes will deploy when reverse thrust is selected."

http://www.b737.org.uk/flightcontrols.htm

This website explains it. 

[daombre]

Michael,

I really don't understand your problem.

If you fly touch and go's you will not go into reverse thrust. As soon as you touch down you will set flaps 15 and advance the throttles again for takeoff. So there will be no spoiler deployment.

You will only use reversers if you really want to stop and then speedbrakes make a lot of sence. The NG behaves just like that as far as I know.

And btw, I think this is a pretty clever automatism from Boeing because in 99,9 % of all cases the plane will do what the pilot actually would like it to do. 

So you are referring to a "normal" landing where you use:

- reverse thrust

- no autobrake

and you want the spoilers to stay in? If I understood you right (I doubt that )  then I really can't understand why someone wants to do that.

Julian

[KirMi]

1 hour ago, poodster said:

Spoilers are Coming up because you applied reverse thrust. 

"Flight spoilers (2 -1/2/3/4/500; 4 -NG's) augment the ailerons and are powered by hydraulic system A (inboard) & B (outboard). Spoilers will continue to operate with speedbrake deployed.

Ground spoilers are also from hydraulic system A.

Only the outboard flight spoilers are powered by hydraulic sys B

On landing, if armed, all spoilers will deploy when the thrust levers are at idle and any two wheels have spun up or right gear is compressed. If not armed, the speedbrakes will deploy when reverse thrust is selected."

http://www.b737.org.uk/flightcontrols.htm

This website explains it. 

Thanks poodster, that gave me the/one missing link. From looking onto drawing schematics, I,ve always end up in a black box named "spoiler mixer".
-Michael

[Tchou]

I think that was what we where all trying to tell you, the spoilers deploy with reversers thats all... You seemed to think it was not normal... 

[ert11`]

I suppose the 737 spoiler handle works the same as the classic 747 does? If so, reverse will not deploy spoilers but will arm the spoiler handle. Since all requerements for spoiler deployment are allready met, they will deploy.

A mechanism coupled with the reverser handles will place the spoiler handle a bit up and aft, in the arm position. The auto spoiler actuator then moves the spoiler handle all the way aft. This was very tricky when testing reversers at the (overwing) gates because motering engines gave edp hyd press and rev handle pulled spoilers in arm, result: spoiler panels damaged by overwing gate!