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Speed Brake Designs And Effectiveness  
User currently offline2H4 From United States of America, joined Oct 2004, 8955 posts, RR: 60
Posted (7 years 5 months 4 weeks 2 hours ago) and read 6224 times:
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It's a rainy night at the coffee shop, and my mind is wandering.  coffee   scratchchin 

Have any of you flown an aircraft type with a particularly effective or ineffective speed brake?

I find Mooney speed brakes to be less than impressive at reducing forward speed, but they do allow the pilot to increase the rate of descent pretty nicely. If I remember correctly, when you're all trimmed up with power set at cruise, deploying the speed brakes without touching anything else will result in a nice ~500 fpm descent.

At the same time, their design actually allows a pilot to leave the speed brakes extended during a go around without any significant performance penalty:


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Photo © Renato Burkhart



It would be interesting to conduct a test. The speed reduction of various aircraft types could be timed, and perhaps a particular design would prove to be more effective than the rest.


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Photo © Alexander Kueh



So, any votes for the most and/or least effective speed brake? Do any designs produce significant pitch tendencies? Are any designs so ineffective that they barely warrant the installation of the equipment?


2H4





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26 replies: All unread, showing first 25:
 
User currently offlineEssentialPowr From United States of America, joined Sep 2000, 1820 posts, RR: 2
Reply 1, posted (7 years 5 months 3 weeks 6 days 22 hours ago) and read 6177 times:

In a jet most designs are effective; I have yet to find any that don't create a pitch change, from corporate jets to airliners.

I do not like the ERJ design that is binomial, in that they are deployed or stowed with no intermediate positions. I do like the fact they retract automatically regardless of handle position when the thrust lever angle exceeds a certain value.


User currently offlineTroubleshooter From Germany, joined Feb 2005, 423 posts, RR: 5
Reply 2, posted (7 years 5 months 3 weeks 6 days 19 hours ago) and read 6156 times:

Quoting EssentialPowr (Reply 1):
I do like the fact they retract automatically regardless of handle position when the thrust lever angle exceeds a certain value.

All aircrafts I know do so. It´s not logical to move the thrust levers forward with speed brakes extended.



This job sucks!!! I love this job!!!
User currently offlineZeke From Hong Kong, joined Dec 2006, 8840 posts, RR: 75
Reply 3, posted (7 years 5 months 3 weeks 6 days 18 hours ago) and read 6138 times:

Quoting Troubleshooter (Reply 2):

All aircrafts I know do so. It´s not logical to move the thrust levers forward with speed brakes extended.

I think that was a design flaw pointed out in the 757 crash in Cali.

Jets I have flown, the speed brakes do little below 250 kt, gear and flap work better.



We are addicted to our thoughts. We cannot change anything if we cannot change our thinking – Santosh Kalwar
User currently offlineFredT From United Kingdom, joined Feb 2002, 2185 posts, RR: 26
Reply 4, posted (7 years 5 months 3 weeks 6 days 4 hours ago) and read 6053 times:

Pretty effective:

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I thought I was doing good trying to avoid those airport hotels... and look at me now.
User currently offlineMissedApproach From Canada, joined Oct 2004, 713 posts, RR: 2
Reply 5, posted (7 years 5 months 3 weeks 5 days 23 hours ago) and read 6012 times:

I've heard Hornet drivers complain that their speedbrake is not very impressive at higher airspeeds, that it doesn't deploy fully until the speed comes down.
I would think a speedbrake along the centerline would produce the least pitch change, such as F-14, F-16, BAe-146 & Fokker 70/100.

Quoting FredT (Reply 4):
Pretty effective:

No kidding! Big boards & low mass will do that  Wink



Can you hear me now?
User currently offlineEssentialPowr From United States of America, joined Sep 2000, 1820 posts, RR: 2
Reply 6, posted (7 years 5 months 3 weeks 5 days 22 hours ago) and read 5994 times:

Quoting Troubleshooter (Reply 2):
All aircrafts I know do so. It´s not logical to move the thrust levers forward with speed brakes extended.

As was mentioned by Zeke, they do not retract automatically on the 757, which accounts for a very large amount of pax capacity worldwide(!). The American 757 in Cali would have cleared the mountain if they had...


User currently offline2H4 From United States of America, joined Oct 2004, 8955 posts, RR: 60
Reply 7, posted (7 years 5 months 3 weeks 5 days 22 hours ago) and read 5987 times:
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DATABASE EDITOR




Quoting EssentialPowr (Reply 6):
As was mentioned by Zeke, they do not retract automatically on the 757, which accounts for a very large amount of pax capacity worldwide(!). The American 757 in Cali would have cleared the mountain if they had...

I thought this was addressed, and that the automatic retraction function was installed in the 757 fleet after the Cali crash. Am I mistaken?


2H4





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User currently offlineBio15 From Colombia, joined Mar 2001, 1089 posts, RR: 7
Reply 8, posted (7 years 5 months 3 weeks 5 days 22 hours ago) and read 5986 times:

Quoting Troubleshooter (Reply 2):
All aircrafts I know do so. It´s not logical to move the thrust levers forward with speed brakes extended.

As I understand, during a go-around the first and most important thing is to apply power, and it's safe to do so early when you take into account the engine spool up time. Configuring the aircraft as required must be done immediately after.

Tail split speedbrakes such as those on Fokker 100 and Bae 146 aircraft are commonly extended during approach to have the engines delivering higher power, so in the event of a go-around spool-up time is less of a concern.

It doesn't seem so ilogical to me to find a situation in which power is applied with speed brakes extended.


Alfredo

[Edited 2007-01-16 06:13:47]

User currently offlinePhilSquares From , joined Dec 1969, posts, RR:
Reply 9, posted (7 years 5 months 3 weeks 5 days 21 hours ago) and read 5970 times:

Quoting 2H4 (Reply 7):

I thought this was addressed, and that the automatic retraction function was installed in the 757 fleet after the Cali crash. Am I mistaken?

Simple answer....Yes.

On any aircraft I've flown the only time you get speedbrakes to automatically retract is on the ground after they've deployed. By advancing the throttles they will automatically retract.

However, in flight there is no "auto-retract".

On most aircraft (glass) you get a EICAS message saying "speedbrakes ext" when the speedbrakes are deployed and the throttles advanced.


User currently offline2H4 From United States of America, joined Oct 2004, 8955 posts, RR: 60
Reply 10, posted (7 years 5 months 3 weeks 5 days 21 hours ago) and read 5967 times:
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Quoting PhilSquares (Reply 9):
However, in flight there is no "auto-retract".

Ah, ok. Thanks for the clarification, PhilSquares.  Smile


2H4





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User currently offlineZeke From Hong Kong, joined Dec 2006, 8840 posts, RR: 75
Reply 11, posted (7 years 5 months 3 weeks 5 days 20 hours ago) and read 5958 times:

Quoting PhilSquares (Reply 9):
On any aircraft I've flown the only time you get speedbrakes to automatically retract is on the ground after they've deployed. By advancing the throttles they will automatically retract.

Phil,

On the 320 you flew, the speed brake automatically retract if you had a SEC fault, elevator fault, full flap, TLA above MCT, alfa floor, AoA protection, and the symmetrical spoiler of the opposite wing will also auto retract if one fails on the other side.

Basically the same on the 330/340.



We are addicted to our thoughts. We cannot change anything if we cannot change our thinking – Santosh Kalwar
User currently offlineTroubleshooter From Germany, joined Feb 2005, 423 posts, RR: 5
Reply 12, posted (7 years 5 months 3 weeks 5 days 19 hours ago) and read 5950 times:

Quoting EssentialPowr (Reply 6):
As was mentioned by Zeke, they do not retract automatically on the 757, which accounts for a very large amount of pax capacity worldwide(!). The American 757 in Cali would have cleared the mountain if they had...

Ok. Then I should mention that I have never worked on the 757 and have no idea about its systems. Big grin



This job sucks!!! I love this job!!!
User currently offlinePhilSquares From , joined Dec 1969, posts, RR:
Reply 13, posted (7 years 5 months 3 weeks 5 days 19 hours ago) and read 5943 times:

Quoting Zeke (Reply 11):
Phil,

On the 320 you flew, the speed brake automatically retract if you had a SEC fault, elevator fault, full flap, TLA above MCT, alfa floor, AoA protection, and the symmetrical spoiler of the opposite wing will also auto retract if one fails on the other side.

Basically the same on the 330/340

I think we're talking about normal operations. Otherwise, this becomes a can of worms.....


User currently offlineZeke From Hong Kong, joined Dec 2006, 8840 posts, RR: 75
Reply 14, posted (7 years 5 months 3 weeks 5 days 16 hours ago) and read 5928 times:

Quoting PhilSquares (Reply 13):

I think we're talking about normal operations. Otherwise, this becomes a can of worms.....

Fair enough, a CFIT response like the 757 at Cali would have an auto retract on an Airbus.



We are addicted to our thoughts. We cannot change anything if we cannot change our thinking – Santosh Kalwar
User currently offlineIAHFLYR From United States of America, joined Jun 2005, 4790 posts, RR: 22
Reply 15, posted (7 years 5 months 3 weeks 5 days 14 hours ago) and read 5891 times:

Lots of B73 drivers complain about the speed brake saying it is just an annoying rumble maker, only giving about 500' per minute more in a descent, anyone comment on the things that wake me up on the way into LAX all the time?  Smile


Any views shared are strictly my own and do not a represent those of any former employer.
User currently offlineCurmudgeon From Australia, joined Oct 2006, 695 posts, RR: 22
Reply 16, posted (7 years 5 months 3 weeks 5 days 14 hours ago) and read 5878 times:

The 737 speed brakes are not all that effective, yielding a small incremental increase in vertical speed or deceleration rate. Below 250 they are useless...above 300 they are less so, but they do create a lot of buffeting and noise. There is a noticeable pitch 'bump' if they are stowed quickly-one more area where smooth handling is rewarded.


Jets are for kids
User currently offlineJetstar From United States of America, joined May 2003, 1636 posts, RR: 10
Reply 17, posted (7 years 5 months 3 weeks 5 days 4 hours ago) and read 5801 times:
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The Lockheed JetStar had a excellent speed brake system and we used it almost all the time on descent. In the picture below you can see the speed brake extended while on the ground, it is located on the lower fuselage aft of the landing gear.


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Extending it on the ground also allows entry to the aft compartment commonly known amongst JetStar operators as the boiler room or hell hole for maintenance and preflights.

On the P&W powered JetStar’s to prevent compressor stalling below 80 percent RPM air is automatically bled off the 4th stage of compression by opening a bleed strap, so basically the engine does not produce much power under 80%. By bleeding this air off there is not enough bleed air that can be taken off at the 9th stage, which is used for pressurization. So on descent in order to maintain cabin pressurization one engine, usually #2 engine must be kept above 80 percent and this one engine will provide enough forward thrust that it inhibits speed reduction, especially when slowing down to meet the 250 knots under 10,000 feet rule. If we had to stop at some altitudes on the way down, we would just bring another engine, #3 up just above 80 % and leave the speed brake extended.

We usually extended the speed brake in the mid to upper 20’s on descent to start slowing the airplane down. There is hardly any pitch adjustment needed and while there is a slight noise, there is no rumbling like wing mounted speed brakes. We usually kept the speed brake out until we reached 200 knots, the maximum speed for approach flaps and retracted the speed brake while the approach flaps were coming out. There are only 2 positions, extend and retract, but the switch had a center position that just removed the hydraulic pressure and it allowed to speed brake to be pushed up somewhat by the airflow, but it still added some drag.

If the speed brake is not retracted when full flaps is extended, then we would get an aural warning and a warning light, both not cancelable. If for some reason the speed brake did not retract because of a mechanical problem there would be a lot of metal left on the runway on landing, and it has happened.

JETSTAR TRIVIA.

To prevent accidental speed brake retraction on the ground in case there is someone standing on the brake, which had built in steps while accessing the boiler room, there is a ground safety valve in the retract hydraulic line that prevents hydraulic pressure from retracting the speed brake, it does retract fairly fast. On the real early JetStars this valve was located in a small panel on the fuselage just inboard of the number 2 engine. When extended on the ground the bottom of the speed brake was only inches from the ground and had to be raised for towing so all JetStar operators had a support cable that lifted the speed brake high enough to allow towing. In one case I heard, someone pushed the door up by hand and into the door lock while the safety valve was closed for towing out to the ramp, the airplane then took off and when the speed brake was extended, it operated properly but would not retract and they had to land with the speed brake extended. (lots of metal on the runway), I think is was a military JetStar.

Lockheed on later models and issued a service bulletin to modify the earlier ones, relocated the valve to the sill of the speed brake housing and if this way if someone pushed the speed brake up it would trip the safety valve back to its normal position.


User currently offlineN231YE From , joined Dec 1969, posts, RR:
Reply 18, posted (7 years 5 months 3 weeks 5 days 4 hours ago) and read 5792 times:

Nobody mentioned the Douglas SBD Dauntless:


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Very interesting design, considering the aircraft's primary role was dive bombing in WWII. The speed-brakes look more like "perforated flaps."

Good thread too, I often wondered the same thing.

[Edited 2007-01-16 23:59:51]

User currently offlineTroubleshooter From Germany, joined Feb 2005, 423 posts, RR: 5
Reply 19, posted (7 years 5 months 3 weeks 4 days 21 hours ago) and read 5732 times:

Quoting Bio15 (Reply 8):
Tail split speedbrakes such as those on Fokker 100 and Bae 146 aircraft are commonly extended during approach to have the engines delivering higher power, so in the event of a go-around spool-up time is less of a concern.

It doesn't seem so ilogical to me to find a situation in which power is applied with speed brakes extended.

In this case you might be correct. But this type of speed brakes does not destroy lift! They just increase drag.



This job sucks!!! I love this job!!!
User currently offline2H4 From United States of America, joined Oct 2004, 8955 posts, RR: 60
Reply 20, posted (7 years 5 months 3 weeks 4 days 20 hours ago) and read 5728 times:
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Quoting Jetstar (Reply 17):

Thanks for the great info, Jetstar. Your posts are always enjoyable to read.  Smile




I forgot about this shot. The Bristol 188 had some unique speed brakes:




2H4





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User currently offline411A From United States of America, joined Nov 2001, 1826 posts, RR: 8
Reply 21, posted (7 years 5 months 3 weeks 3 days 14 hours ago) and read 5624 times:

Upper wing surface mounted spoilers in swept wing jet transports can indeed cause pitch difficulties, if not designed properly.

Example, B707.

Generally little pitch problems encountered when spoilers initially applied, however severe tail buffeting was the result.
This could be avoided by 'spliting' the spoilers, IE: using the outboards only (by switching OFF the inboards), however then the pitch problems started (nose up) which required nose down elevator and nose down pitch trim applied at the same time, and if not balanced together properly, stab jackscrew stalling resulted, which was NOT good.
Retracting spoilers resulted in a reverse process.
Gave new guys the fits until learned properly.

Whereas, the L1011.

No pitch changes noted, at any IAS, and very minor buffeting, due mainly to number one spoiler panel being deactivated with speed brake deployment.
#1 panel was thus used for AGS and DLC...the latter a TriStar specialty.
Clearly, a superior design, which works flawlessly.

Lockheed TriStar...a true 'pilots' airplane.


User currently offlineZeke From Hong Kong, joined Dec 2006, 8840 posts, RR: 75
Reply 22, posted (7 years 5 months 3 weeks 3 days 12 hours ago) and read 5610 times:

Quoting 411A (Reply 21):
Lockheed TriStar...a true 'pilots' airplane.

Sounds like you worked at CX before !



We are addicted to our thoughts. We cannot change anything if we cannot change our thinking – Santosh Kalwar
User currently offlineImperialEagle From United States of America, joined Jan 2006, 2395 posts, RR: 23
Reply 23, posted (7 years 5 months 3 weeks 3 days 1 hour ago) and read 5520 times:
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Selecting reverse-thrust on the inboard engines of the old DC-8's was very effective----but you did have to be ready for that "tuck"!


"If everything seems under control, you're just not going fast enough!"
User currently offlineCosmicCruiser From United States of America, joined Feb 2005, 2255 posts, RR: 15
Reply 24, posted (7 years 5 months 3 weeks 2 days 13 hours ago) and read 5447 times:

Quoting Jetstar (Reply 17):
The Lockheed JetStar had a excellent speed brake system and we used it almost all the time on descent.

Your picture brought back lots of memories from the 70s. I flew a jetstar with almost the identical paint scheme and color. They were both -8 jetstars modded to the jetstar II specs. 731 fans, underslung tanks. The first jet I flew to have INS.


25 411A : No, Zeke, not CX. A very long time at SV and UL, amoung others. Just finished two months of Hajj flying in the 'ole Lockheed tri-motor. The specific a
26 Post contains links Aviopic : They seem to be very effective on the F70/100 for speed reduction and an increase of the rate of decent. As far as I know it is not used for landing w
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