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Reverse Thrust/Brakes  
User currently offlineFuture_Pilot From , joined Dec 1969, posts, RR:
Posted (13 years 7 months 1 week 5 days 5 hours ago) and read 3319 times:

Can any pilot tell me when the brakes and/or reverse thrust is used after touching down at 140 knots. Does the aircraft need to slow slow down to a certain speed using only the spoilers and reverse thrust before the brakes are used or are all three used simoteniously after the wheels touch the runway?

Thanks in advance.

21 replies: All unread, jump to last
 
User currently offlineAAR90 From United States of America, joined Jan 2000, 3465 posts, RR: 47
Reply 1, posted (13 years 7 months 1 week 5 days 4 hours ago) and read 3241 times:

I know of no airplane with a limitation on when wheel brakes can be applied. Most airliners have automatic wheel brake systems that will apply the brakes at a pre-programmed rate (normally decelleration force) upon main wheel spinup. MD90 is an exception as the large carbon brakes are far too powerful and will cause anti-skid to activate constantly causing excessively long stopping distances [a situation where human being performance is better than computers -- yeah!].

On MD90, my personal preference is to use idle reverse thrust and light application of wheel brakes [warms up the carbon pads for better traction without anti-skid activation]. Manual spoiler deployment was preferred, but automatic spoiler deployment is now mandatory at AA on this aircraft.

On 757/767 (5000hrs), my preference was for idle reverse thrust with minimum wheel brakes near end of roll (manually applied, not automatically) and automatic spoilers. In practice this meant that after main gear on ground the spoilers would begin decelleration followed shortly thereafter by reverse thrust and eventually wheel brakes. Using all three simultaneously caused excessive decelleration forces making for uncomfortable passengers (many worry easily). Besides, smoother is better -- right? Not sure if automatic brakes and automatic spoilers are required on these aircraft since I haven't flown one in a year.



*NO CARRIER* -- A Naval Aviator's worst nightmare!
User currently offlineFeret From , joined Dec 1969, posts, RR:
Reply 2, posted (13 years 7 months 1 week 4 days 22 hours ago) and read 3203 times:

On the B767 with auto brakes armed a pre-determined rate of deceleration is provided on touchdown when the trucks untilt. both thrust levers are at idle and wheel spinup occurs. This deceleration rate is maintained regardless of the amount of reverse thrust used. #1 position is quite gentle and the rate can be increased simply by rotating the switch to 2,3,4 or Max. Ground spoilers should always be used and are usually deployed automatically (even if forgotten, when reverse is used they deploy).
In our company arming of the speed brakes and wheel brakes, while not mandatory, is strongly recommended. Imagine the paperwork if it all turned to s**t and they weren't armed!


User currently offlineDc10hound From United States of America, joined Dec 2000, 463 posts, RR: 5
Reply 3, posted (13 years 7 months 1 week 4 days 21 hours ago) and read 3204 times:

OK people, you're getting into my area, here. The previous reponses were from "drivers". And I don't use the word "drivers" disparangily.
You guys stop'em every day with no problem.
You Fly'em. I'll figure how they work (and fix'em well).

But the points we need to remember are:

1. The energy dissipated by an airliner upon landing, and attempting to stop,
is distributed in the following percentages:

a. Spoilers: 2% They hold you down to the runway.

b. Thrust Reverse: 4% It helps stop the ship. But it only helps. There is no airliner that has ever been certified to stop with out T/R. That's why we can placard them inopertive.

c. Brakes: 94% : They are really the business end of what halts that monster.

2. I would have to look up the MM on a 767, but there is no "spin-up" on the
757. As Feret said, the Autobrakes activate when the trucks un-tilt (touchdown), part of the air-ground logic in the Proximity Electronics Unit (PSEU) but does not use wheel speed. After much research I myself was surprised to find this. Wheel speed is used for Anti-Skid. Douglas was famous for using wheel spin-up for spoilers. Airbus still uses it for Autobrake.

3. Ground Spoilers on a 757 do not deploy until the T/R levers are actuated.
Be aware of that if a T/R is placarded inop. The MEL is specific on letting you
know. I think that is the reason we can only have one inop? But what if the
"good" one doesn't work either?





"Eagles soar. But weasels never get sucked into jet intakes.."
User currently offlineFeret From , joined Dec 1969, posts, RR:
Reply 4, posted (13 years 7 months 1 week 3 days 18 hours ago) and read 3169 times:

Re autobrakes - I always thought and my books tell me that "spin-up" is a requirement for the 767, just went and had a look. I have no access to the MM at present to confirm though. Other types of aircraft I have also flown on require wheel spin-up to prevent landings with the brakes applied, ties with the anti-skid systems.

BTW, I'm not a "driver" but you are close.  


User currently offlineAAR90 From United States of America, joined Jan 2000, 3465 posts, RR: 47
Reply 5, posted (13 years 7 months 1 week 3 days 12 hours ago) and read 3162 times:

DC10hound writes:

>You Fly'em. I'll figure how they work (and fix'em well).

Dear sir, would you please update your bio information. I'm having trouble understanding how a 13-15 year old is fixing airliners.

>a. Spoilers: 2%
>b. Thrust Reverse: 4%
>c. Brakes: 94%

What is the reference source for these figures? Just wondering since all aircraft are of different designs.

>There is no airliner that has ever been certified to
>stop with out T/R. That's why we can placard them inopertive.

Contradictory statement. In the USA, FAA certification is based upon no reverse thrust. That means ALL airliners ARE certified without T/R.

>Ground Spoilers on a 757 do not deploy until the
>T/R levers are actuated.

On landings, if armed the 757/767 ground spoilers deploy upon touchdown. They are not dependent upon T/R levers in the "armed" mode. If unarmed, they will deploy automatically with T/R lever activation (if not deployed previously).




*NO CARRIER* -- A Naval Aviator's worst nightmare!
User currently offlineRed Panda From Hong Kong, joined Jun 2000, 1521 posts, RR: 0
Reply 6, posted (13 years 7 months 1 week 3 days 11 hours ago) and read 3158 times:

the spoilers are crusual to keep the a/c down on the rwy. Also they are used for slowing the a/c down at hi speed. The spoilers are not effective to slow down the a/c as the a/c slow down to certain speed.
The reverse thrust is to kill the forward thrust and slow down the a/c at hi speed only just like the spoilers.
The automatic brakes are the only tools to slowdown the whole a/c after the a/c slow down to certain speed.

R Panda


User currently offlineFeret From , joined Dec 1969, posts, RR:
Reply 7, posted (13 years 7 months 1 week 3 days 5 hours ago) and read 3138 times:

Sorry Red Panda but your last sentence is absolute rubbish. In fact the whole posting is incorrect.

User currently offlineDc10hound From United States of America, joined Dec 2000, 463 posts, RR: 5
Reply 8, posted (13 years 7 months 1 week 3 days 3 hours ago) and read 3135 times:

OK, lighten up dude!

We're just tryin to get things straight here.... (If you think I'm screwed up, go look at Red Panda's post. Me thinks he was in the bar a wee bit too long...)

Try this: Enter (AAL) B757 Flight Deck. Turn on L&R hydraulics. Actuate either T/R lever. What is the result?

The spoilers will deploy.

This option is installed for RTO.

You are once again correct (And I was wrong, for the first time ever,ever, in Never, Never land) in stating that Ground Spoiler deployment is independent of T/R lever actuation upon landing.

I will, with your permission, back up, regroup, and give you the full Skivvy....

As far as the 13-15 year old cracks go, return to first sentence of this post.
Pfffffffffffft!



"Eagles soar. But weasels never get sucked into jet intakes.."
User currently offlineDc10hound From United States of America, joined Dec 2000, 463 posts, RR: 5
Reply 9, posted (13 years 7 months 1 week 3 days 2 hours ago) and read 3126 times:

I STILL SAY: Untilt throws them damn Spoilers! Hmmm....


"Eagles soar. But weasels never get sucked into jet intakes.."
User currently offlineAAR90 From United States of America, joined Jan 2000, 3465 posts, RR: 47
Reply 10, posted (13 years 7 months 1 week 3 days 1 hour ago) and read 3126 times:

>OK, lighten up dude!

When in non-serious mode, please utilize "smilies". That's what they are there for.

>We're just tryin to get things straight here....

That is why I disagreed with some of your answers. They were incorrect.

>(If you think I'm screwed up, go look at Red Panda's post.
>Me thinks he was in the bar a wee bit too long...)

Reread it numerous times and it becomes obvious English is not his native language. I think I understand what he was trying to say and basically he was correct.

>This option is installed for RTO.

Not an option on either 767 or 757. An airline can opt to have the feature deactivated if it so chooses, but the standard airplanes come with the feature installed.

>I STILL SAY: Untilt throws them damn Spoilers!

Not by itself. If what you say is true, then a landing gear truck(s) stuck in level condition after takeoff would cause ground spoilers to deploy in flight! Highly doubtful a system with a single failure mode that will cause a crash would ever be certified by FAA.

BTW, in my 5000 hours of flying AA's B757/767 aircraft, I have had this exact event occur twice. Once on takeoff, once prior to landing. On both occasions no spoiler deployed at anytime.



*NO CARRIER* -- A Naval Aviator's worst nightmare!
User currently offlineFeret From , joined Dec 1969, posts, RR:
Reply 11, posted (13 years 7 months 1 week 2 days 19 hours ago) and read 3108 times:

AAR90 - I wasn't going to reply as we are sort of straying from the topic, but, what the heck! I just can't help myself.  
I presume you don't take-off with the speedbrake ARMED, too noisy that audible warning!
From recall (and remember I have killed quite a few braincells on layovers over the last 36 years), moving the speedbrake lever to the ARMED position signals the spoiler panels to extend automatically after landing. The speedbrake lever moves to the UP position and the spoiler panels (flight and ground) extend when all of the following conditions occur:
-there is hydraulic pressure to both landing gear truck tilt actuators
-both truck tilt sensors detect a no-tilt condition (aircraft on ground)
-both thrust levers are at idle.
Perhaps this explains why you did not experience uncommanded spoiler deployment when you had truck tilt problems?
I am very interested in the reasons for the truck tilt problems you experienced. I can only remember one problem in this area with our 767s in their 17 year history and that was due to the non-fitment of a safety bolt after a wheel brake unit change.
As I said before, things mechanical on the 767 are a little hazy as I left it over 2 years ago when they were converted from 3 to 2 crew. I did manage 10 years and over 6600 hours though, so a few things have stuck and perhaps can be filed under "Useless Information".  
Cheers,
Feret.




User currently offlineVC-10 From United Kingdom, joined Oct 1999, 3697 posts, RR: 34
Reply 12, posted (13 years 7 months 1 week 2 days 19 hours ago) and read 3106 times:
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Well it makes a change foe someone pretending to be an engineer !

On the 757 Ground Spoiler will deploy when the following conditions apply :-

1. Thrust levers in the idle position

2. Speedbrake lever in the armed detent position

3. Both MLG on ground

4. Left hyd system pressurised.

T/rev spoiler deployment is just a fall back. If the Speedbrake lever has not been armed.

"No airliner has ever been certified to stop without t/revs ", well Dc10hound, it may interest you to know that with the advent of Carbon Brakes operators are now changing procedures whereby they are requesting crews not to use the T/revs on landing (unless they really have to) beacuse the brakes are more efficient on their own & they last longer than if they are used in conjunction with T/revs.


User currently offlineAAR90 From United States of America, joined Jan 2000, 3465 posts, RR: 47
Reply 13, posted (13 years 7 months 1 week 2 days 14 hours ago) and read 3100 times:

One was mechanical link breakage, the other I don't recall... about 10 years ago. Sorry.


*NO CARRIER* -- A Naval Aviator's worst nightmare!
User currently offlineDc10hound From United States of America, joined Dec 2000, 463 posts, RR: 5
Reply 14, posted (13 years 7 months 1 week 1 day 22 hours ago) and read 3081 times:

Air/Ground logic keeps the spoilers down when airborne, if a truck un-tilts.
Both trucks probably must un-tilt to deploy the spoilers. Nose gear should be involved too.




"Eagles soar. But weasels never get sucked into jet intakes.."
User currently offlineDc10hound From United States of America, joined Dec 2000, 463 posts, RR: 5
Reply 15, posted (13 years 7 months 1 week 22 hours ago) and read 3068 times:

After reviewing the original post that started this thread, and also reviewing several of the posts I made, I would like to submit the following text from the B757 MM (If anybody cares to look at this subject anymore).

Remember, to MX [Maintenance] the Aircraft Maintenance Manual [AMM, or MM] is THE FINAL AUTHORITY (Caps in this sentence were added for emphasis only, caps in the following text are Boeing). This information is for Boeing Model 757 aircraft only. And for that matter AAL B757s only. [Info in brackets added by myself for clarity, or my opinion]

ATA [Air Transport Association] Chapter 27-62-00-0

"Auto Speedbrake Control System - Description and Operation"

"A. Functional Description

(1) General

(a) The Auto Speedbrake system raises all spoiler panels when commanded by
the SCMs [Spoiler Control Modules - computers]. the SCMs process input from the auto speedbrake switches, engine reverse switch[reverse thrust levers], forward thust lever [throttle] position switches, and air/ground logic. Air/ground logic originates with the truck tilt proximity switches (Ref 32-09-03, Description and Operation)[And we do not want to go there tonight]. The system will also retract the spoiler panels during a go-around after touchdown.

(2) Normal Operation

(a) During a normal landing, [definitely not at takeoff, as a DC-10 does] the flight crew arms the auto speedbrake system by moving the speedbrake lever out of the down and locked detent to the ARMED position. When the following conditions are met, the auto speedbrake actuator [located in the pedestal] moves the speedbrake lever to the UP position.

1) Both engine forward thrust levers are set at less than 50 percent total lever
travel.
2) Both truck tilt [hydraulic] pressure switches signal high pressure [3,000 PSI].
3) All truck tilt proximity switches signal that the landing gear is not tilted.


(3) Refused Takeoff [RTO] or Emergency Landing [???]

(a) During a refused takeoff or an emergency landing with the system unarmed,
the spoiler panels will extend when the reverse thrust levers are moved into the reverse idle range. The [reverse thrust] levers mechanically release the speedbrake lever from the down and locked detent to the ARMED position and close the engine reverse thrust switch. When the following conditions are met, the auto speedbrake actuator moves the speedbrake lever to the UP position.

1) Both truck pressure switches signal high [hydraulic] pressure.
2) All [note all] truck tilt proximity switches signal that the landing gear is not tilted.

(4) Go-Around After Touchdown

(a) After a normal landing sequence, the auto speedbrake system retracts the spoiler panels during a go- around after touchdown. Moving either of the forward thrust levers to greater than 50 percent total travel will fully retract the auto speedbrake actuator, moving the speedbrake lever to the down and locked detent."


[The next one is shorter, and more to the point:]

ATA Chapter [and Verse] 32-42-00-02

"ANTISKID/AUTOBRAKE SYSTEM DESCRIPTION AND OPERATION"

"D. Autobrake system

(1) The system applies brakes automatically at touchdown when the average wheel speed reaches 60 knots [so wheel spin-up at touchdown certainly is involved]. it maintains a constant pilot-selected deccelaration level throughout the landing roll. The only pilot effort required is to select the desired level prior to each landing. there is no interference with normal antiskid system operation. Full manual braking is always avaiable."

[Interesting, the last sentence tells you that max autobrake is not full brake application at it's upper limit. You can apply them yourself and get more brake action]

As you can see from the above text, Auto Spoiler [ATA 27- Flight Controls] and
Autobrake [ATA - 32 Landing Gear] are two separate systems that happen to operate at the same time - at touchdown.

The system seems quite redundant against inadvertant spoiler extentsion.

If you read the electrical schematic, bring a bottle of bufferin. It gave me a headache.

I humbly retract any statements that I made that were at tilt (pardon the pun, I could'nt resist) with the above info.

The above info has been reproduced as acurrately as possible from the applicable AMM.

Once again, this is all for a B757 only. Anybody wanna talk about a 'Bus?

(or a 10?)




"Eagles soar. But weasels never get sucked into jet intakes.."
User currently offlineVC-10 From United Kingdom, joined Oct 1999, 3697 posts, RR: 34
Reply 16, posted (13 years 7 months 1 week 20 hours ago) and read 3059 times:
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It is interesting to note that you say that the above MM is only applcable to the AAL fleet. In your post on 767/757 Ailerons the you said the MM was applicable to all a/c of thay type i.e not operator specific.

User currently offlineFeret From , joined Dec 1969, posts, RR:
Reply 17, posted (13 years 7 months 1 week 19 hours ago) and read 3056 times:

Thank God I was correct about some things! Of course never once did I doubt myself      
I have to agree about the RTO selection and the braking applied. I've only had a couple rejects (obviously above 85KIAS) and each time the aircraft has almost stopped before reverse
spooled-up because the equivalent of max manual (not auto) brakes is applied. Now that sure grabs everybody's attention down the back.


User currently offlineDc10hound From United States of America, joined Dec 2000, 463 posts, RR: 5
Reply 18, posted (13 years 7 months 1 week 1 hour ago) and read 3041 times:

The reference to AAL MM only is a disclaimer. Sure as heck, somebody from some other operator will hammer me because their Boeing MM says something different, i.e. different configurations between operators. Although it's a pretty good bet that Spoilers/Autobrakes operate the same on the worldwide fleet of 757s.

I will (try) not (to) hang myself in the wind again when it comes to technical issues.  

On another note, where did you find the info on flight crews being told not use T/R on A/C with carbon brakes? I've never heard that one. I find that interesting...



"Eagles soar. But weasels never get sucked into jet intakes.."
User currently offlineDc10hound From United States of America, joined Dec 2000, 463 posts, RR: 5
Reply 19, posted (13 years 7 months 1 week ago) and read 3040 times:

What I meant to say is "ALL Airliners have been certified to stop without T/R".
(The % numbers I gave bear this out)
Sorry. It was a long night.



"Eagles soar. But weasels never get sucked into jet intakes.."
User currently offlineVC-10 From United Kingdom, joined Oct 1999, 3697 posts, RR: 34
Reply 20, posted (13 years 7 months 6 days 19 hours ago) and read 3035 times:
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It is the operating procedure of my company. T/rev's can be used if necessary, but it is more economic on engines & brakes if they are not used.

As you are probably aware Carbon Brakes are more effective and wear less if they operate in a specific temperature range. Useing T/rev keeps them out of that range for longer


User currently offlineDc10hound From United States of America, joined Dec 2000, 463 posts, RR: 5
Reply 21, posted (13 years 7 months 6 days 3 hours ago) and read 3027 times:

Just as a general story:

Went on FCF on an MD-11 today for #1 Auto Pilot pitch trim.

Result: Number 1 A/P still AFU.

Newest PIREPs: Number 1,2 and 3 Engines would not go into reverse after touchdown.

Corrective Action for T/R: Closed number 1,2 and 3 Engine T/R circuit breakers.

Still working the A/P problem.

It was NOT a good day.
(The only bright side is, we get to go flying again!    )




"Eagles soar. But weasels never get sucked into jet intakes.."
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