Mr Spaceman
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Use Of Speed Brakes In Icing Conditions?

Sat Jan 31, 2004 7:20 am

Hi guys.

I've been wondering ..........

If pilots of an airliner were picking up ice during their descent for arrival & approach to their destination, and they were a little faster than ATC liked, would they still use their speed brakes (spoilers) to slow down?

I'm wondering about the buildup of ice that could occur on the spoiler panels themselves and the internal parts of the wing & the spoiler actuators, etc, when flying through icing conditions such as "mixed moderate" icing.

Can ice build up to the point where the spoilers won't be able to fully retract into the upper surface of the wing - thus reducing lift - or are the hydraulic actuators powerful enough to smash away any ice that's forming on the spoiler panels while they're deflected into the airstream?

I guess what I'm asking is ....... is it Standard Operating Procedure (SOP) for some airliner flight crews to NOT use speed brakes during known icing conditions, or is this not a concern?


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Chris  Smile
"Just a minute while I re-invent myself"
 
Guest

RE: Use Of Speed Brakes In Icing Conditions?

Sat Jan 31, 2004 8:12 am

I can't speak for the "big boys", but on the bizjets that I've flown there are no restrictions on the use of "the boards" in icing conditions. Just a side note, we don't use the boards nearly as often in bizjets as they are used in larger aircraft, but they really do come in handy on occasion.

Jetguy

 
XFSUgimpLB41X
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RE: Use Of Speed Brakes In Icing Conditions?

Sat Jan 31, 2004 8:19 am

No restrictions liek that on the CRJ... the ice is going to form onthe leading edge of things... not farther back on the wing.
Chicks dig winglets.
 
Mr Spaceman
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RE: Use Of Speed Brakes In Icing Conditions?

Sat Jan 31, 2004 8:28 am

Hello Jetguy.

Thanks for your reply.

OK, so there's been no speed brake restrictions on the bizjets that you've flown. That's good to know.

My mind's been thinking about (and visualizing) ..... freezing rain, ice pellets, supercooled water droplets, etc, smashing all over extended spoiler panels (the boards Big grin), and the turbulent airflow wraping around in behind the spoilers causing a problem with the spoilers sealing down tight to the upper wing surface because of ice buildups.

Perhaps it's not a problem for the big guys either.

Chris  Smile
"Just a minute while I re-invent myself"
 
Guest

RE: Use Of Speed Brakes In Icing Conditions?

Sat Jan 31, 2004 8:37 am

Actually, I've wondered the same things myself. However, there never seems to be a problem. I sure that it probably has to do with the aerodynamics involved. Remember, everything is realitive. I would guess that the aerodynamics are the same because we are flying at the same (or faster) speeds, at the same (or higher) altitudes, and have the same (or higher) wing loading as any of the larger transport category jets.

 
Mr Spaceman
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RE: Use Of Speed Brakes In Icing Conditions?

Sat Jan 31, 2004 9:00 am

Hi guys.

>> XFSUgimpLB41X, Thanks for your info about the CRJ.

I understand that the leading edges of the wings, vertical & horizontal stabilizers on aircraft are going to get coated when flying through icing conditions. That's normal.

It seems to me, however, that if you extend a flat panel of metal or carbon composite material (a spoiler) into a high speed relative airflow that's saturated with super cooled water droplets, those panels are going to also get coated with ice.

In my mind's eye, visually it seems to make sense that ice could cause a problem, however, as Jetguy mentioned, there never seems to be a problem.So perhaps aerodynamics do keep air brakes clean in icing conditions.


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Chris  Smile
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CX Flyboy
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RE: Use Of Speed Brakes In Icing Conditions?

Sat Jan 31, 2004 4:50 pm

No operating restrictions at all during ANY phase of the flight on the 777, icing or no icing. We can even use it with full gear and flaps down, although this would be highly unusual.
 
AJ
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RE: Use Of Speed Brakes In Icing Conditions?

Sat Jan 31, 2004 5:12 pm

Same for the 767, except they have to be stowed by 800' or when thrust is added to prevent a master caution!

(BTW CX, 'full gear', is that as opposed to partial gear...you have that setting?  Big grin)
 
Mr Spaceman
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RE: Use Of Speed Brakes In Icing Conditions?

Tue Feb 03, 2004 4:42 am

Hi guys.

>> Cx flyboy & AJ, Thank You for your replies. Big grin

I thought that it might be SOP to not use speed brakes while flying through icing conditions, but I've learned from you guys that the use of speed brakes while flying through ice is not a problem. That's good to learn & fun to know.

Thanks for your info.

Chris  Smile
"Just a minute while I re-invent myself"
 
CX Flyboy
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RE: Use Of Speed Brakes In Icing Conditions?

Tue Feb 03, 2004 10:02 am

AJ,

To elaborate, if we use speeadbrakes up to gear down flaps 20, as long as the thrust is at idle, there will be no warning. Using speedbrakes when flaps are at 25 or 30 will cause the "SPEEDBRAKES EXT" caution, although as long as we acknowledge it and are expecting it, there is no restriction to us using the speedbrakes at that stage of flight!
As for the partial gear, we only us it if we are doing a partial landing....like a touch and go! Big grin
 
AJ
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RE: Use Of Speed Brakes In Icing Conditions?

Tue Feb 03, 2004 10:28 am

Partial landing...mate, there is only one 767 style landing and that's a FULL ON LANDING! We don't have those gorgeous six wheeled eagle talons that cushion your every move!
 
411A
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RE: Use Of Speed Brakes In Icing Conditions?

Tue Feb 03, 2004 11:57 am

B707 and Lockheed L1011--
It is sometimes required to use spoilers in icing conditions so that the engine power can be increased so that sufficient bleed air is available for engine and airframe anti-icing, while at the same time keeping the airspeed within reason in the TMA. This is also true while descending from higher altitudes, thru icing conditions, that would otherwise be normally done with idle thrust...ie: thrust required to generate bleed air/spoilers extended to descend.

However, unlike on newer types, on the B707, using spoilers with flaps extended is not allowed...on the L1011, not recommended.
 
musang
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RE: Use Of Speed Brakes In Icing Conditions?

Tue Feb 03, 2004 10:39 pm

All very interesting, but has anyone seen ice accrete on spoilers/airbrakes?

The smaller the surface presented to the airflow, the greater the accretion potential, thats why antennas and windscreen wipers ice up quickly, and tailplanes/fins before mainplanes (smaller radius leading edges).

I don't remember any limitations on using spoilers/airbrakes on any transports I've operated.

Regards - Musang
 
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RE: Use Of Speed Brakes In Icing Conditions?

Wed Feb 04, 2004 12:17 am

Musang...
I've never seen it happen, but then I wasn't really looking for it either.
 
411A
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RE: Use Of Speed Brakes In Icing Conditions?

Wed Feb 04, 2004 12:25 am

Tailplane icing.

It might surprise some to learn that a few transport jets do not have any tailplane anti-icing, the Lockheed TriStar, for example. Extensive flight tests concluded that tailplane icing was not a problem with this particular design.
Older design first generation jets had tailplane anti-icing systems installed, but I suspect this was only by customary design, as large piston/turbopropeller aircraft needed same.
In over thirty years of flying HEAVY jet transports, have yet to really have a need for airframe anti-icing, altho it was switched on when conditions were favorable for airframe icing to occur.

ENGINE anti-icing is, of course, an entirely different matter.

Musang,

Can't even see the wing from the TriStar flight deck, let alone the spoilers.
As for the B707, never noticed any ice on the spoilers when in use.
 
musang
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RE: Use Of Speed Brakes In Icing Conditions?

Thu Feb 05, 2004 7:46 am

411A - I appreciate that. I was hoping someone knowledgeable had observed from the cabin!

Regards - Musang

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