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wing
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Things That Make Me Go Hmmm....on A320 No:2

Fri Feb 02, 2007 6:01 pm

Yesterday I flew with a captain who was also an ex 737 veteran.We had a very nice flight together altough it was a very long 4 legged flight.As a joke we made couple of 737 callouts to each other and laughed,also remembered our "old fellow".

We compared some advantages and disadvantages of the 2 airplanes.It turned out we both loved the 737 during his 9 and my 4 years experience on the type but onthe other hand if we ever offered to go back to the old type we we both agreed that we prefer to stay on the airbus.

The airplane was A321 yesterday,filled with 186 passengers and some distant alternate and possible long holding fuel due to bad weather and heavy arrival traffic on a single runway operation day.We were heavy and the runway was wet(thats the infamous rwy 06 of IST,one of the most overrun'ed runway of the world)

At one point I remembered one of the instructors words to check the autobrake landing distance for that particular runway when approaching with the weights over 70 tons,especially when wet and as I checked it really was not sufficient enough to land with "low" autobrake setting with 75 tons on a wet day. The other autobrake setting "medium" was more than enough according to the calculation tables(and from my experience ,it makes you feel like you cought the arresting cables on an aircraft carrier).However the runways touchdown zone is covered with tyre marks and especially when wet they become slippery as ice,and as the feauture of the medium a/b it starts braking immediately as the aircraft touches down,might be a risk.I've made my famous "HMMM" then.



So we elected to land on the longer(and newer)runway but it was a tough crosswind landing.Now thats a scenerio which maynot be valid on many parts of the world but its a typical problem on rwy 06 landings at Istanbul.

The autobrake system in my opinion needs another setting between LOW and MED in my opinion. (Like the 2-3 setting on 737)As the thrust reversers are less effective on the CFM engines compared to the V2500 engines,brake temperatures go all the way up,and if you don't have brake fans on that particular aircraft on a hot day,you start your regular HMMM's again  Smile
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HAWK21M
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RE: Things That Make Me Go Hmmm....on A320 No:2

Fri Feb 02, 2007 6:26 pm

Quoting Wing (Thread starter):
infamous rwy 06 of IST,one of the most overrun'ed runway of the world

Are there any Stats Available on this.
regds
MEL
I may not win often, but I damn well never lose!!! ;)
 
speedracer1407
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RE: Things That Make Me Go Hmmm....on A320 No:2

Fri Feb 02, 2007 7:10 pm

Wing,

THis reminds me of a a 2 leg flight I had a few years ago. We took off from IND, and landed at MSP, then took another flight from MSP to SJC. We experience identical and peculiar braking on BOTH landings into MSP and SJC. After touchdown, we began to slow nice and comfortable as I"m accustomed to. THen, a few seconds before we turned off the runway, the brakes hit HARD, and I was flung forward against my seat belt, bracing myself on the seat infront of me. I pushed his seat several inches foreward, as did the passenger behind me do to mine. I had never, and haven't since experienced that sort of braking on any airliner. After learning a bit about airliner operations in the past few years on this forum, I always assumed that, for whatever reason, perhaps a quick decision to take an earlier turnoff, the PF selected MAX braking for a moment to bring the plan to safe turnoff speed. However, your description of MED braking sound more like what I experienced. If the difference between LOW and MED braking is indeed what I experienced, I might also say "hmm" because the experience was certainly one of the most memorable in my many many miles of flying over the past 10 years.

Thus, I wonder, becuase if even "MED" braking on an A320 (and family) feels like an "arrestor hook," do you ever find yourself resorting to manual braking when simple adjustments to deceleration rate are needed for whatever reason? And on the airbus, can you change the autobrake deceleration rate after touchdown? It's my understanding that Boeing autobrakes disengage if the setting is changed mid-braking.

O
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VC-10
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RE: Things That Make Me Go Hmmm....on A320 No:2

Fri Feb 02, 2007 9:05 pm

The MAX setting is only used for T.O.

A/brake is designed to decelarate the a/c at a predetermined deceleration rate. A sudden hard brake application will not be a/brake.
 
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HAWK21M
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RE: Things That Make Me Go Hmmm....on A320 No:2

Fri Feb 02, 2007 9:10 pm

Quoting Speedracer1407 (Reply 2):
It's my understanding that Boeing autobrakes disengage if the setting is changed mid-braking.

Application of Manual Braking Disengages A/B.
regds
MEL
I may not win often, but I damn well never lose!!! ;)
 
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Starlionblue
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RE: Things That Make Me Go Hmmm....on A320 No:2

Fri Feb 02, 2007 9:20 pm

Quoting Speedracer1407 (Reply 2):
I always assumed that, for whatever reason, perhaps a quick decision to take an earlier turnoff, the PF selected MAX braking for a moment to bring the plan to safe turnoff speed.

As VC-10 explains, autobraking is set before landing (or take-off). There is no on the fly adjustment.

According to accounts, MAX braking means that if you aren't wearing trousers, your testicles and head will impact the seat in front of you. It's apparently quite something.
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troubleshooter
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RE: Things That Make Me Go Hmmm....on A320 No:2

Fri Feb 02, 2007 11:12 pm

Quoting Wing (Thread starter):
as the feauture of the medium a/b it starts braking immediately as the aircraft touches down

Some informations from my A320 training notes:

LO: pressure to the brakes four seconds after ground spoiler extension. Deceleration rate 1,7 m/s²

MED: pressure to the brakes two seconds after ground spoiler extension. Deceleration rate 3 m/s²

MAX: used for T/O - pressure to the brakes imediately at ground spoiler extension. Deceleration rate 6 m/s² (higher than the aircaft is actually able to reach!!!)

For LO and MED settings: brake pressure starts progressively on ground spoiler extension (after the delay time stated above) to the full required pressure in t=3 secs. Ground spoiler extension needs wheel speed > 72 kts.

Quoting Speedracer1407 (Reply 2):
And on the airbus, can you change the autobrake deceleration rate after touchdown? It's my understanding that Boeing autobrakes disengage if the setting is changed mid-braking.

Yes you can. As long as there is a ground spoiler extend signal you can select a new deceleration by cancelling the previous setting and selecting a new one.
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AirframeAS
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RE: Things That Make Me Go Hmmm....on A320 No:2

Fri Feb 02, 2007 11:30 pm

Quoting Wing (Thread starter):
Things That Make Me Go Hmmm

That quote makes me think of C+C Music Factory!  rotfl  You must love that group, huh? LOL!
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wing
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RE: Things That Make Me Go Hmmm....on A320 No:2

Fri Feb 02, 2007 11:44 pm

Just to clear some stuff;

MAX setting on A320 is used for a rejected take off only and its effective after 72 knots,RTO is the setting for reject in 737 series,


Use of reversers effect the braking amount.

On 737400 the change of a setting in AB after the braking starts causes the AB to disangage,on the -800 it does not.
On the A320 series a change from LOW to MED during the braking will not cause an AB disengagement,the airplane will starts braking harder but not as hard as you can do with manual braking,a manual braking is always harder then all AB settings.

You can disengage the AB by pressing on the rudder pedals,or pressing the a/b pb.

One can learn pressing the brake pedals by the hard way,when taxying a little hard pressure on the brakes may make you feel like literally hitting to a wall   

Quoting HAWK21M (Reply 1):
Are there any Stats Available on this.
regds

http://i33.photobucket.com/albums/d52/WING321/Haziran2006e351me021.jpg

You can see the marks of the 2 of at least 3 over runs happened only during the last winter,there may be some statistical reports in the safety network or somewhere.

[Edited 2007-02-02 15:47:00]
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wing
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RE: Things That Make Me Go Hmmm....on A320 No:2

Fri Feb 02, 2007 11:57 pm

Quoting AirframeAS (Reply 7):
You must love that group, huh? LOL!

That song is lovely isnt it?  Smile
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Starlionblue
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RE: Things That Make Me Go Hmmm....on A320 No:2

Sat Feb 03, 2007 6:59 am

Quoting Wing (Reply 9):
Quoting AirframeAS (Reply 7):
You must love that group, huh? LOL!

That song is lovely isnt it? Smile

Let's not forget the video with that great chick. http://www.youtube.com/watch?v=hu0sWf-PXCE
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
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HAWK21M
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RE: Things That Make Me Go Hmmm....on A320 No:2

Mon Feb 05, 2007 5:42 pm

Quoting Wing (Reply 8):
You can see the marks of the 2 of at least 3 over runs happened only during the last winter

Was that contributed by the Snow.
regds
MEL
I may not win often, but I damn well never lose!!! ;)
 
AirframeAS
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RE: Things That Make Me Go Hmmm....on A320 No:2

Mon Feb 05, 2007 11:42 pm

Quoting Wing (Reply 9):
That song is lovely isnt it?

For its time in the early 1990's yeah. But now, no. LOL!

As to the thread, A320's are nice, expecially in the new US livery.
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NKP S2
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RE: Things That Make Me Go Hmmm....on A320 No:2

Tue Feb 06, 2007 2:55 am

Quoting Wing (Thread starter):
)As the thrust reversers are less effective on the CFM engines compared to the V2500 engines

I'm surmising you're making an A32X/737 comparison. The CFM56 equipped A320 family has a completely different thrust reverser setup than the T/Rs on the 737.
 
AirframeAS
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RE: Things That Make Me Go Hmmm....on A320 No:2

Tue Feb 06, 2007 3:24 am

Quoting NKP S2 (Reply 13):
The CFM56 equipped A320 family has a completely different thrust reverser setup than the T/Rs on the 737.

That is correct  checkmark 
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wing
Topic Author
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RE: Things That Make Me Go Hmmm....on A320 No:2

Tue Feb 06, 2007 6:52 am

Quoting AirframeAS (Reply 14):
The CFM56 equipped A320 family has a completely different thrust reverser setup than the T/Rs on the 737.

That is correct

Thats is both correct.

We have both CFM equipped and V2500 equipped A320's in the fleet.My comparison was actually between these two.V2500's are more powerful than the CFM 56's.Therefore more effective TR's two.
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