speedracer1407
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RTO Procedures

Tue Oct 03, 2006 4:09 pm

I guess I'm on a braking kick tonight.

It's my understanding that, above a certain speed (80kts?), airliners equipped with autobrakes that are appropriately set to RTO before takeoff will automatically apply RTO braking power and deploy ground spoilers after throttles are pulled back to idle. I assume the RTO brake setting is pretty much maximum braking or close to it.

So, if an airliner is on its takeoff run down a runway with far more length than needed to accelerate to V1 (or even VR), then stop, and the PF elects to reject the takeoff at a relatively low 100kts or so due to engine failure, does he simply pull back the throttles and let the autobrakes slam the plane back down to taxi speed even though there's little or no need to apply heavy braking? Is he empowered to decide whether RTO braking is necessary? Might he simply switch the autobrakes to "off" and use mild manual braking BEFORE pulling the throttles and trigering RTO autobrakes if there's obviously a lot of room left to decelerate?

thanks for any replies,

O
Dassault Mercure: the plane that has Boeing and Airbus shaking in their boots.
 
BA777
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RE: RTO Procedures

Tue Oct 03, 2006 4:20 pm

I would've said that in absolutely any RTO situation the pilots should let it all hang out, you never know when you might get another failure if you already have an engine failure for example...I'd say better safe than sorry - whack all the brakes on and stop and then deal with the problem safely.

Henry
 
flymatt2bermud
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RE: RTO Procedures

Tue Oct 03, 2006 9:49 pm

Quoting Speedracer1407 (Thread starter):
Is he empowered to decide whether RTO braking is necessary? Might he simply switch the autobrakes to "off" and use mild manual braking BEFORE pulling the throttles and triggering RTO autobrakes if there's obviously a lot of room left to decelerate?

I agree with Henry, the procedure has been rehearsed time and time again in the simulator. The takeoff briefing in our cockpit usually goes something like this. "We will abort for any malfunction up to 80 knots, after the 80 knot callout we will abort in the event of an engine failure, loss of directional control, a red warning light and aural warning or anything either of us deem appropriate. Once anyone calls "Abort" we will abort using maximum braking and thrust reverse as available"

We will exercise a maximum abort and sort things out after the aircraft has been slowed and we have determined what priority items need to be accomplished first.

I can appreciate you thinking if there is plenty of runway we can relax a bit, but why take a chance of getting confused, run the RTO drill, slow the aircraft, determine what situational items must be addressed immediately, secure them and taxi clear of the runway and then pull out the checklist.
Otherwise you might overlook something and it's always better to react appropriately than to wish you had.
"When once you have tasted flight, you will forever walk the earth with your eyes turned skyward" Leonardo Da Vinci
 
onetogo
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RE: RTO Procedures

Tue Oct 03, 2006 11:53 pm

If you manually apply braking during an RTO, does that disarm the autobrakes like it does on a normal landing?
 
flymatt2bermud
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RE: RTO Procedures

Wed Oct 04, 2006 12:59 am

Quoting Onetogo (Reply 3):
If you manually apply braking during an RTO, does that disarm the autobrakes like it does on a normal landing?

Yes, after either pilot applies brakes the autobrakes are disengaged.
"When once you have tasted flight, you will forever walk the earth with your eyes turned skyward" Leonardo Da Vinci
 
EssentialPowr
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RE: RTO Procedures

Wed Oct 04, 2006 3:25 am

Love the autobrakes in an RTO...you can get bruises from the shoulder straps; they work!
 
aviopic
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RE: RTO Procedures

Wed Oct 04, 2006 3:49 am

Quoting Speedracer1407 (Thread starter):
I assume the RTO brake setting is pretty much maximum braking or close to it.

Yes and it doesn't matter because any setting is probably to much anyway.
When doing over 80kts or more when close to V1 the wings already produce lift reducing the pressure between the tyres and tarmac so some skidding is very easily introduced.
Which is why there is an Anti Skid System(the equivalent of a car's ABS) present as well.
So in a nut shell the ABS is armed by selecting RTO and engaged by retarding the thrust levers after which it will apply maximum brake power(the abs unit steers a current controlled coil which in term controls the brake valve) during which the Anti Skid Unit prevents skidding of the runway.
The ABS is disengaged by applying manual brake.
So you can't brake harder then the Anti Skid System allows you to which depends on factors like: Weight on wheels, Speed and Surface conditions(dry,rain,snow etc...)

The lands modes: low, medium or high work the same but the coil is steered with a different(less) fixed current and therefor reducing the brake pressure although on the F70/100 I am familiar with the land mode "High" and take off mode "RTO" are identical in terms of the current applied to the coil.

Quoting Speedracer1407 (Thread starter):
Might he simply switch the autobrakes to "off" and use mild manual braking BEFORE pulling the throttles and trigering RTO autobrakes if there's obviously a lot of room left to decelerate?

Stopping an aircraft which is traveling around V1 can be a tricky business and you don't want the crew to hassle with the brakes.
They need their full attention to keep the thingy on the black stuff and probably have other things on their mind anyway, after all they did not initiate the RTO for no reason(smoke, engine fire..... to name a few).
This is why the ABS RTO mode was invented in the first place.
The truth lives in one’s mind, it doesn’t really exist
 
EssentialPowr
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RE: RTO Procedures

Wed Oct 04, 2006 4:51 am

Quoting Aviopic (Reply 6):
Yes and it doesn't matter because any setting is probably to much anyway

Don't agree...Look at any of the braking distance performance charts (use the 737 as an example) and there are big differences b/t the settings, which is why RTO is the absolute max braking effort. The is no such thing as "way too much" when the a/c needs to get stopped.

Quoting Aviopic (Reply 6):
When doing over 80kts or more when close to V1 the wings already produce lift reducing the pressure between the tyres and tarmac so some skidding is very easily introduced.

Again, no, as the spoilers should kill the lift, and the antiskid ensures max Coef friction....ie, no skid.

Quoting Aviopic (Reply 6):
The ABS is disengaged by applying manual brake.

3 strikes, you're out! Anti skid still works with auto brakes off...you are confusing autobrakes with antiskid...

[Edited 2006-10-03 21:52:57]
 
aviopic
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RE: RTO Procedures

Wed Oct 04, 2006 5:42 am

Quoting Essentialpowr (Reply 7):
which is why RTO is the absolute max braking effort.

Yes, that is what i said.

Quoting Essentialpowr (Reply 7):
The is no such thing as "way too much" when the a/c needs to get stopped.

Which is why I never said there was.

Quoting Essentialpowr (Reply 7):
Again, no, as the spoilers should kill the lift, and the antiskid ensures max Coef friction....ie, no skid.

I just explained that although ABS(Auto Brake System) applies max presure you still can't brake harder then Anti Skid allows you to.

Quoting Essentialpowr (Reply 7):
3 strikes, you're out! Anti skid still works with auto brakes off...you are confusing autobrakes with antiskid...

No, you are out due to "bad reading".
It didn't mix up anything: ABS(Auto Brake System) is disengaged by applying Manual Brake.
As explained Anti Skid works apart from the ABS(Auto Brake System) which is why it controls it own valves......... as explained.

It just takes a bit of proper reading..... that's all  Smile
The truth lives in one’s mind, it doesn’t really exist
 
EssentialPowr
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RE: RTO Procedures

Wed Oct 04, 2006 5:53 am

2 quotes:

Quoting Aviopic (Reply 6):
Yes and it doesn't matter because any setting is probably to much anyway.

followed by

Quoting Aviopic (Reply 6):
Which is why I never said there was.

Uhh...I think you did say that any setting is too much!
 
EssentialPowr
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RE: RTO Procedures

Wed Oct 04, 2006 6:01 am

Quoting Aviopic (Reply 8):
No, you are out due to "bad reading".

Regarding your description of how the auto brakes and anti skid work, I did misread that part and agree with your statements. My apologies for that.
 
aviopic
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RE: RTO Procedures

Wed Oct 04, 2006 6:32 am

Quoting EssentialPowr (Reply 10):
Regarding your description of how the auto brakes and anti skid work, I did misread that part and agree with your statements. My apologies for that.

No problem English is not my native nor first language and sometimes it is a bit difficult to explain these things in proper English, I'll do my best though  Smile

Quoting EssentialPowr (Reply 9):
Quoting Aviopic (Reply 6):
Yes and it doesn't matter because any setting is probably to much anyway.
followed by
Quoting Aviopic (Reply 6):
Which is why I never said there was.
Uhh...I think you did say that any setting is too much!

What i meant was that the Auto Brake System does not feature any brake pressure regulation in RTO, it's just max on.
In the given situation this might be to much brake pressure to prevent skidding(think about a slippery runway for example) in which situation the Anti Skid System takes care of releasing some of the pressure thru it's own dedicated valve.
So both systems do not work against each other but with each other.

Quoting Essentialpowr (Reply 7):
you are confusing autobrakes with antiskid

Agree, both systems are mixed up quite a lot.
Just because ABS in our aviation world means something different then the for many people more familiar car world.
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EssentialPowr
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RE: RTO Procedures

Wed Oct 04, 2006 6:41 am

Thanks for the clarification; nice thread.
 
wilco737
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RE: RTO Procedures

Wed Oct 04, 2006 3:06 pm

Quoting Aviopic (Reply 11):
What i meant was that the Auto Brake System does not feature any brake pressure regulation in RTO, it's just max on.
In the given situation this might be to much brake pressure to prevent skidding(think about a slippery runway for example) in which situation the Anti Skid System takes care of releasing some of the pressure thru it's own dedicated valve.
So both systems do not work against each other but with each other.

Cars have this system as well, I mean the anti skid... Ever done an emergency breaking and felt the pedal vibrating? Thats the anti skid releasing the brake pressure for a VERY short time to give you the chance to keep control over your car...
The aircraft anti skid does the same! Avoid that the tires block and then might burst...

During RTO let the autobrake hit the full brakes and when you are at a safe slow speed and you can judge that the remaining runway is sufficient, then you can override the autobrake by applying the brakes on the pedals and then it disengages (or simply switch it off) Big grin
But initially let the ABS do its job! Max brake pressure applied to the brakes (3400psi on the 737) which is a lot...
The speedbrakes are not automatically deployd (on 737) you have to do it manually... and then full reverse thrust...


WILCO737
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ThrottleHold
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RE: RTO Procedures

Wed Oct 04, 2006 7:12 pm

Quoting WILCO737 (Reply 13):
The speedbrakes are not automatically deployd (on 737) you have to do it manually

They will auto deploy as soon as the reversers are activated, even if they are not in the "armed" position.
 
aviopic
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RE: RTO Procedures

Wed Oct 04, 2006 10:54 pm

Quoting WILCO737 (Reply 13):
Cars have this system as well, I mean the anti skid...

Did I say they don't ?
I just said that what is known as ABS(Anti Blocking System ???) in a car is something different then in a Aircraft where it stands for Auto Brake System.

Quoting WILCO737 (Reply 13):
Ever done an emergency breaking and felt the pedal vibrating?

Nope...... my 1980 car does not feature this thingy  Big grin

Quoting WILCO737 (Reply 13):
The aircraft anti skid does the same! Avoid that the tires block and then might burst...

Yes, that is what I tried to explain.

Have Fun,
Willem
The truth lives in one’s mind, it doesn’t really exist
 
curlyheadboy
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RE: RTO Procedures

Wed Oct 04, 2006 11:17 pm

May I ask a question?  Wink

It's not uncommon to see flat tires after a rejected T/O. Now, since the anti-skid should prevent the wheels from blocking, I assume it's not friction damage that bursts the tires. So what's the actual cause?
If God had wanted men to fly he would have given them more money...
 
aviopic
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RE: RTO Procedures

Thu Oct 05, 2006 1:22 am

Quoting CURLYHEADBOY (Reply 16):
I assume it's not friction damage that bursts the tires. So what's the actual cause

The heat build up inside the tyre does and it is designed that way.
It's like an pressure protection to prevent a tyre from explosion.
The truth lives in one’s mind, it doesn’t really exist
 
speedracer1407
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RE: RTO Procedures

Thu Oct 05, 2006 4:28 am

Quoting Aviopic (Reply 17):
The heat build up inside the tyre does and it is designed that way.
It's like an pressure protection to prevent a tyre from explosion.

If I may briefly expand on that. Etreme heat generated by the brakes during heavy braking heats up the tires beyond temperatures caused by weight and friction. Fuse plugs allow the tire to safely deflate once it has reached a certain demperature, rather than burst uncontrolably.
Dassault Mercure: the plane that has Boeing and Airbus shaking in their boots.
 
aviopic
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RE: RTO Procedures

Thu Oct 05, 2006 5:03 am

Quoting Speedracer1407 (Reply 18):
Fuse plugs allow the tire to safely deflate once it has reached a certain demperature, rather than burst uncontrolably.

Thanks Speedracer, that's exactly what I meant to say.
Forgot the name Fuse plugs Big grin
The truth lives in one’s mind, it doesn’t really exist
 
CosmicCruiser
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RE: RTO Procedures

Thu Oct 05, 2006 10:23 pm

Quoting Aviopic (Reply 6):
Yes and it doesn't matter because any setting is probably to much anyway.

That's irrelevant. An event such as an RTO is NOT the time to try to decide whether you need max, med, or min brakes. The Auto Brake System will apply Max and as our chklist directs, if you happen to be using manual brakes (ABS deffered or a/c not equipped, some MD-10s) then MAX brakes are still applied. Any RTO in a heavy jet anywhere close to V1 is a BIG deal.Try slacking up because you have plenty of runway on a chk ride and it's a bust. If you have a situation dire enough to make a RTO you need to get the jet stopped ASAP.

Looks like there was a lot of confusion and misunderstanding of some people's post because some flipped back and forth with the automobile vs. a/c nomenclature. Stick with the aviation terms.
JET CAR
ABS, Auto Brake System N/A
Antiskid System ABS Anti-lock Brake System
 
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Starlionblue
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RE: RTO Procedures

Thu Oct 05, 2006 11:13 pm

Quoting WILCO737 (Reply 13):
Cars have this system as well, I mean the anti skid

Indeed. The system migrated from planes to cars. Of course, cars have now taken it further with spin control, stability control and so forth. My car (a SAAB) will differentially apply brakes in corners to keep it "on rails" if it senses loss of grip. I have tried "breaking" the system on a parking lot and it's amazing how the car simply goes where I point it even at very high cornering speeds. I chickened out well before I felt any inkling of control loss with the yellow "stability" warning light giving me a suntan. Should probably try it on snow.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
aviopic
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RE: RTO Procedures

Fri Oct 06, 2006 12:25 am

Quoting CosmicCruiser (Reply 20):
An event such as an RTO is NOT the time to try to decide whether you need max, med, or min brakes. The Auto Brake System will apply Max and as our chklist directs

Yes that's exactly what I said all the time Big grin
With one addtion extra though:
You still can't brake harder then the Anti Skid allows you too even though the ABS applies max braking pressure.
Anti Skid works independent from the ABS and will always redirect hydraulic pressure if needed to prevent skidding.
That's all.

Quoting CosmicCruiser (Reply 20):
Any RTO in a heavy jet anywhere close to V1 is a BIG deal

And this as well.

Quoting CosmicCruiser (Reply 20):
Looks like there was a lot of confusion and misunderstanding of some people's post because some flipped back and forth with the automobile vs. a/c nomenclature.

I didn't flip back and forth just explained the differences as you tried yourself.

Quoting CosmicCruiser (Reply 20):
ABS, Auto Brake System N/A

Incorrect, several new cars(expensive Merc's and BMW) have an ABS(Auto Brake System..... don't know the cars name for it) which will become active when you are to close to the car in front.
The system will even smack the brakes on(just like your RTO) in case the system detects a rapid decrease of distance between you and the car in front(due to an accident or traffic jam)
In one way the car system is even better then the equivalent A/C system because it also works in dense fog which is why it was developed in the first place.

It would be nice if posting were read before answered, my English isn't that bad........ is it ?  Wink
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Starlionblue
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RE: RTO Procedures

Fri Oct 06, 2006 4:54 am

Quoting Aviopic (Reply 22):
In one way the car system is even better then the equivalent A/C system because it also works in dense fog which is why it was developed in the first place.

Well if there's another plane on the runway you have more serious problems  Wink
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
CosmicCruiser
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RE: RTO Procedures

Fri Oct 06, 2006 9:54 am

Quoting Aviopic (Reply 22):
It would be nice if posting were read before answered, my English isn't that bad........ is it ?

No your english is not bad and they were read but other posts went back and forth on the subject.

Quoting Aviopic (Reply 22):
You still can't brake harder then the Anti Skid allows you too even though the ABS applies max braking pressure.
Anti Skid works independent from the ABS and will always redirect hydraulic pressure if needed to prevent skidding.
That's all.

Yes I'm quite "up to speed" on how anti skid works and it is just that that ALLOWS max braking. Max is as good as it gets because you approach a lock (skid) but never get there. Without antiskid you would blow the tires long before max braking. I know you understand this..CC

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