Specific Braking Procedure in FCOM for A-320-236A

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3WE
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Specific Braking Procedure in FCOM for A-320-236A

Postby 3WE » Fri May 27, 2016 4:16 pm

Would you (or Dummy) share the typical braking procedures for landings?

I used to think things were done almost exclusively manually as I remember lots of variations in braking, plenty of surges and variations in intensity, etc. Thanks to MSFS and a few sentences here and there, I’m now aware of autobrakes, and thinking that they are involved in most landings- but from row 20-whatever I’m never sure what’s going on. The bold questions are probably the things I’m asking that are “new and different”

Here’s my guesses, please give us yes-es and no-s as appropriate or even a sentence or two if insight.

The plane touches down and spoilers activate automatically (except when you touch down too soft)?

After a short delay, autobrakes kick in at some healthy-but-not-excessive level (for most landings)?

Do they wait for nose gear touchdown?

Also, shortly after touchdown, you guys are switching to reverse thrust (we discussed the variations of nose gear touchdown vs reverser use in a previous thread)?

Around 80 knots on most aircraft, you throttle back to idle on reverse (and maybe even turn off reverse all together to not kick dirt/crap up to potentially be ingested).

Then you typically switch off autobrakes and brake manually in that 60 to 80 knot range?

I’m just after a little insight to have a halfway accurate guess of what’s happening if I feel a surge or reduction in braking during a landing roll out.

PS, If you include lots of cryptic acronyms I may find it sexy.
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Re: Specific Braking Procedure in FCOM for A-320-236A

Postby flyboy2548m » Fri May 27, 2016 8:17 pm

Close enough other than no, they don't wait for the nose gear.

Myself, I'm not a real big fan of autobrakes.
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Re: Specific Braking Procedure in FCOM for A-320-236A

Postby 3WE » Fri May 27, 2016 10:30 pm

...Myself, I'm not a real big fan of autobrakes.
Interesting.

I assumed you don't get too much choice in their use...that it's somewhat regimented based on runway length and condition and weight and perhaps even wind and that turning them off 'real early' might be frowned upon.

Management and Evan seems like they like their procedures for you idiot, brake-improvisation cowboys.
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Re: Specific Braking Procedure in FCOM for A-320-236A

Postby flyboy2548m » Fri May 27, 2016 11:14 pm

...Myself, I'm not a real big fan of autobrakes.
Interesting.

I assumed you don't get too much choice in their use...that it's somewhat regimented based on runway length and condition and weight and perhaps even wind and that turning them off 'real early' might be frowned upon.
You assumed wrong.
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Re: Specific Braking Procedure in FCOM for A-320-236A

Postby flyboy2548m » Fri Jun 03, 2016 3:02 am

Since this whole topic seems to refuse to die, I guess I'll elaborate.

If the A320 family has an operational weak spot, it's the brakes. They are amazingly effective, but they also get very hot very fast. We have a limitation that prohibits takeoffs at a BTMS indication of 300C or higher, and it doesn't take long for the brakes to get to that temp or higher (much higher in places like LAS and PHX in the summer), especially if the inbound crew was a little hamfisted (hamfooted?) with the pedals. Airbus offers built-in brake fans (lovingly referred to as hair dryers) as an option specifically to combat that issue, but my airline's management felt that said fans are too expensive and too heavy, hence fewer than half of our birds have that option, which means if the brakes get above 300, all there is to do is sit and wait until they chill a tad.

Now, the autobrakes on the 320 family have three settings : Low, Med, and Max. I forget the exact numbers, but Low gives something like 4.4 m/s2 decel rate, Med gives something like 8.8m/s2 while Max just applies full brake force, for which reason it is prohibited to use Max for landing, since there won't be a single intact neck on the airplane after such a maneuver. Max setting is only used for RTO and RTO is the only time autobrakes are REQUIRED to be used. All other times are a matter of technique and/or recommendation.

The other issue is that for quite a while my airline preached using only idle reverse (though this, too, was a recommendation, not a requirement) in order to save fuel, so people were put between a rock and a hard place. Either burn "too much" fuel by honking the reversers or smoke the brakes. The BSCU looks at the difference between the actual deceleration rate and the required one (see the 4.4 and 8.8 above) and with reversers at idle, it would apply more and more brake effort warming the brakes up generously even on a Low setting. I've seen brake temps well above 400C on hot days.

Thus, this is what flyboy2548m does:

I land autobrakes off and don't touch the brakes until 60kts or less. On most of our runways that technique works handsomely even with idle reverse. We get to the gate with the brakes at 100-120C which is perfect. On A321s, especially at higher weights, I almost always use max reverse. If it burns a little extra gas, so be it.

The only exception is some place like LGA, especially when taking A321s there. Then I use autobrakes Med but only until I hear the reversers rev up. Then I kick them off and don't touch the brakes again until the aforementioned 60kts. That keeps the brakes in the 200-220 range which means by the time we deplane and reboard 200+ people, they cool back down nicely.
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Re: Specific Braking Procedure in FCOM for A-320-236A

Postby 3WE » Fri Jun 03, 2016 12:15 pm

...I'll elaborate...this is what flyboy2548m does...
Thank you.

Aviation stuff is cool.

Your comments provide insight into the thinking behind all of this and a number of nuances and intangibles not_found in Evan's out-dated FCOMs nor on the internet.

I am always impressed at how airplane brakes retain heat.

Evan's feelings for your tendency to use your cowboy idiot toes instead of automated-anything will have to remain a mystery.
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Re: Specific Braking Procedure in FCOM for A-320-236A

Postby Not_Karl » Fri Jun 03, 2016 8:32 pm

which means if the brakes get above 300, all there is to do is sit and wait until they chill a tad.
You could always send rampies to blow them cool... :mrgreen:
Max just applies full brake force, for which reason it is prohibited to use Max for landing, since there won't be a single intact neck on the airplane after such a maneuver.
Sounds like fun! :twisted:
Thus, this is what flyboy2548m does:
(genius brakemanship)
:clap: :clap:

Thank you, interesting reading :D .
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Re: Specific Braking Procedure in FCOM for A-320-236A

Postby flyboy2548m » Tue Jun 21, 2016 11:26 pm

which means if the brakes get above 300, all there is to do is sit and wait until they chill a tad.
You could always send rampies to blow them cool... :mrgreen:
Funny you should mention that. We have EXternal AC-powered fans for just that reason, but only at LAS.
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Re: Specific Braking Procedure in FCOM for A-320-236A

Postby Not_Karl » Tue Jun 28, 2016 12:27 am

which means if the brakes get above 300, all there is to do is sit and wait until they chill a tad.
You could always send rampies to blow them cool... :mrgreen:
Funny you should mention that. We have EXternal AC-powered fans for just that reason, but only at LAS.
Airbus should consider adding USB ports to the gear bays to enable the use o these:

Image
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Re: Specific Braking Procedure in FCOM for A-320-236A

Postby ocelot » Fri Jul 29, 2016 4:59 am

Close enough other than no, they don't wait for the nose gear.

Myself, I'm not a real big fan of autobrakes.
I would have thought that letting the brakes engage before the nose is down would tend to slam the nose down and bend the nose gear...
Since this whole topic seems to refuse to die, I guess I'll elaborate.
thanks! :)

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Re: Specific Braking Procedure in FCOM for A-320-236A

Postby elaw » Fri Jul 29, 2016 12:38 pm

I would have thought that letting the brakes engage before the nose is down would tend to slam the nose down and bend the nose gear...
It's possible they're modulated somehow... light braking until the nose gear is down, then heavier braking.

And/or the ratio of strength to the amount of mass they see may allow the nose gear to take a hard touchdown without ill effect.
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Re: Specific Braking Procedure in FCOM for A-320-236A

Postby flyboy2548m » Fri Jul 29, 2016 3:11 pm

[
I would have thought that letting the brakes engage before the nose is down would tend to slam the nose down and bend the nose gear...
Your thoughts are hereby noted. I'll pass them to EADS engineers, so they might look into that.
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Re: Specific Braking Procedure in FCOM for A-320-236A

Postby flyboy2548m » Fri Jul 29, 2016 3:12 pm

It's possible they're modulated somehow...
Not just somehow I fear.
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Re: Specific Braking Procedure in FCOM for A-320-236A

Postby 3WE » Sat Jul 30, 2016 12:56 pm

[
I would have thought that letting the brakes engage before the nose is down would tend to slam the nose down and bend the nose gear...
Your thoughts are hereby noted. I'll pass them to EADS engineers, so they might look into that.
...as long as we are thinking, I would also think that having no braking until nose gear touch down might lengthen the landing roll out. Please also inform EADS about this as it may also bear some consideration.

See Flyboy, we find this stuff interesting and relish your knowledge infusions.
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Re: Specific Braking Procedure in FCOM for A-320-236A

Postby flyboy2548m » Sat Jul 30, 2016 5:04 pm


See Flyboy, we find this stuff interesting and relish your knowledge infusions.
I rather doubt it (the relish part, anyway), but you're welcome.
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