mon330
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Virgin A346 Video: Why Is Gear Retracted So Late?

Fri Nov 12, 2010 11:26 pm

Hi folks

In the video below, the heavy Virgin Atlantic A340-600 rotates after a lengthy takeoff roll on its flight from Japan to England, but landing gear is not retracted for quite some time. Anyone have any ideas why this may be?

I would have thought it would be retracted straight away to reduce drag, especially given how heavy it is. I wonder if there could have been a problem, or indeed a simple explanation?

I look forward to your theories and/or explanations!

Mark

http://www.youtube.com/watch?v=AMWxqq0W1yI
 
Speedbird741
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RE: Virgin A346 Video: Why Is Gear Retracted So Late?

Fri Nov 12, 2010 11:40 pm

Most probably for the brakes to cool down. Happens often if brakes are heavily used when taxiing.


Speedbird741
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estorilm
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RE: Virgin A346 Video: Why Is Gear Retracted So Late?

Sat Nov 13, 2010 3:33 am

Interesting!!!!!!

I was driving home the other day and was rather alarmed to see an A340 climbing out with gear still extended (this was out of IAD, and since I'm stuck in traffic every day I'm very aware of what looks "normal" and such, and I never see gear down at that altitude / distance from the airport).

I was tempted to call ops and see what happened out of curiosity, or to pull over and see if he was going to come back in (though obviously he'd be dumping fuel) - this was months ago and I stopped thinking about it, but now I'm really curious!
 
Fly2HMO
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RE: Virgin A346 Video: Why Is Gear Retracted So Late?

Sat Nov 13, 2010 4:42 am

Quoting Speedbird741 (Reply 1):
Most probably for the brakes to cool down. Happens often if brakes are heavily used when taxiing.


Speedbird741

  

That would be my guess too. Flight was probably fully loaded, all that weight means more effort on the brakes of course.
 
Soxfan
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RE: Virgin A346 Video: Why Is Gear Retracted So Late?

Sat Nov 13, 2010 4:14 pm

Quoting Speedbird741 (Reply 1):
Most probably for the brakes to cool down. Happens often if brakes are heavily used when taxiing.

Is there a mechanism that tells the pilots about the temperature of the brakes/whether they are hot, or is it simply pilot decision/discretion?
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Speedbird741
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RE: Virgin A346 Video: Why Is Gear Retracted So Late?

Sat Nov 13, 2010 5:14 pm

Quoting Soxfan (Reply 4):
Is there a mechanism that tells the pilots about the temperature of the brakes/whether they are hot, or is it simply pilot decision/discretion?

They have brake temp indications in the ECAM display. Also, when brake temp exceeds 300 degrees (Celsius) the ECAM will display a brake hot warning.

Speedbird741
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b78710
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RE: Virgin A346 Video: Why Is Gear Retracted So Late?

Sat Nov 13, 2010 8:10 pm

most probably a long taxi heavy aircraft, lots of braking. leave the gear down to cool down.

other possible explanation, if he had a brake de activated. leave the gear down longer for that wheel to slow down before retraction.

Quoting Soxfan (Reply 4):
Is there a mechanism that tells the pilots about the temperature of the brakes/whether they are hot, or is it simply pilot decision/discretion?

each brake unit has a temp probe in it. brake temps are displayed on the wheels page of the lower ECAM. the temperature goes orange above 300 degree's C and a warning will display on the upper ECAM to delay take off until brakes have cooled.

the hottest brake will be displayed on the lower ECAM with an orange curved bar above it.
 
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DocLightning
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RE: Virgin A346 Video: Why Is Gear Retracted So Late?

Sat Nov 13, 2010 9:37 pm

Quoting b78710 (Reply 6):
most probably a long taxi heavy aircraft, lots of braking. leave the gear down to cool down.

So given that in another 20 minutes the aircraft is going to be flying through -50° air for the next ~10 hours, why not just retract them? Is the max temp that the brakes can tolerate different than the max temp that the gear bay can tolerate?
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b78710
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RE: Virgin A346 Video: Why Is Gear Retracted So Late?

Sat Nov 13, 2010 10:24 pm

Quoting DocLightning (Reply 7):
So given that in another 20 minutes the aircraft is going to be flying through -50° air for the next ~10 hours, why not just retract them? Is the max temp that the brakes can tolerate different than the max temp that the gear bay can tolerate?

pretty much.

always run the risk of a wheel well fire if you retract whilst the brakes are too hot. those wheels are literally inches away form hydraulic lines, bleed air ducts, fuel lines etc, when retracted, best not get that kind of stuff too hot
 
zanl188
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RE: Virgin A346 Video: Why Is Gear Retracted So Late?

Sat Nov 13, 2010 10:31 pm

Quoting DocLightning (Reply 7):
So given that in another 20 minutes the aircraft is going to be flying through -50° air for the next ~10 hours, why not just retract them?

Hot brakes can cause the wheels and tires to explode. If that happens best they not be in the wheel well where they can take out other systems. Best thing to do is let them hang out in the breeze for a bit to cool down.
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tdscanuck
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RE: Virgin A346 Video: Why Is Gear Retracted So Late?

Sat Nov 13, 2010 10:39 pm

Quoting DocLightning (Reply 7):
So given that in another 20 minutes the aircraft is going to be flying through -50° air for the next ~10 hours, why not just retract them?

Because the wheel well is nowhere close to ambient...especially if you suck several hundred pounds of metal and carbon-carbon heated to several hundred degrees up in there. The airflow in the wheel well, and hence the cooling capability, is very poor.

Quoting DocLightning (Reply 7):
Is the max temp that the brakes can tolerate different than the max temp that the gear bay can tolerate?

Yes, by well over 1000 degF.

Tom.
 
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TS-IOR
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RE: Virgin A346 Video: Why Is Gear Retracted So Late?

Tue Nov 16, 2010 3:12 pm

It could be to keep a relative low speed at a certain configuration and shallow rate of climb, confirm ?!
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mon330
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RE: Virgin A346 Video: Why Is Gear Retracted So Late?

Tue Nov 16, 2010 11:15 pm

Thanks for your comments so far, guys.

I think cooling down of the brakes is a very likely explanation. I didn't think of that myself, though!

Mark
 
delawareusa
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RE: Virgin A346 Video: Why Is Gear Retracted So Late?

Wed Nov 17, 2010 3:39 am

Also possible they blew on the take off roll, and left the gear down to cool.
 
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airportugal310
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RE: Virgin A346 Video: Why Is Gear Retracted So Late?

Wed Nov 17, 2010 4:22 am

Any pictures out there of a break temp warning? Google images search brought nothing good up
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tdscanuck
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RE: Virgin A346 Video: Why Is Gear Retracted So Late?

Thu Nov 18, 2010 4:54 am

Quoting TS-IOR (Reply 11):

It could be to keep a relative low speed at a certain configuration and shallow rate of climb, confirm ?!

Possible, but almost certainly easier and more economical to achieve the same thing by reducing thrust.

Quoting airportugal310 (Reply 14):

Any pictures out there of a break temp warning?

P. 35 (PDF pages) show what it looks like on an A340:
http://www.smartcockpit.com/pdf/plane/airbus/A340/systems/0016/

P. 9 & 14 here show what it looks like on a 757:
http://www.smartcockpit.com/pdf/plane/boeing/B757/systems/0008/

You can hunt around the site for equivalent documents for other aircraft.

Tom.
 
b78710
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RE: Virgin A346 Video: Why Is Gear Retracted So Late?

Thu Nov 18, 2010 4:59 pm

Heres a pic i took today.

Upper ECAM: Shows the caution message in orange "BRAKES HOT" followed underneath by corrective action in blue "PARK BRK: PREFER CHOCKS" "DELAY T.O FOR COOLG"

Lower ECAM: shows all wheels with their respective temps and pressures.

The 2 hot brakes are with the temps in orange, wheels 2 and 6 in this case, 6 being the hottest brake of them all, denoted by the curved orange bar above it.

hope that helps.

 
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akiss20
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RE: Virgin A346 Video: Why Is Gear Retracted So Late?

Thu Nov 18, 2010 6:21 pm

I take it different wheels have different temperature thresholds to trigger the ECAM? It seems there are several other tires with 295 readings that aren't triggering
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bonusonus
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RE: Virgin A346 Video: Why Is Gear Retracted So Late?

Fri Nov 19, 2010 12:41 am

Any reason why they open the MLG doors and leave them open for a while before retracting the gear?
 
b78710
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RE: Virgin A346 Video: Why Is Gear Retracted So Late?

Fri Nov 19, 2010 8:19 am

Quoting AKiss20 (Reply 17):
I take it different wheels have different temperature thresholds to trigger the ECAM? It seems there are several other tires with 295 readings that aren't triggering

i can only see the 2 amber ones reading 295, its not the clearest of pics though

Quoting bonusonus (Reply 18):
Any reason why they open the MLG doors and leave them open for a while before retracting the gear?

thats just the sequence of gear retraction. its not a decision by the flight crew or anyone, thats just how long it takes.

the doors will open, the gear will tilt, retraction wont begin until the tilt has finished.
 
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akiss20
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RE: Virgin A346 Video: Why Is Gear Retracted So Late?

Fri Nov 19, 2010 1:24 pm

Quoting b78710 (Reply 19):
Quoting AKiss20 (Reply 17):
I take it different wheels have different temperature thresholds to trigger the ECAM? It seems there are several other tires with 295 readings that aren't triggering

i can only see the 2 amber ones reading 295, its not the clearest of pics though

To me number 3 looks like 295 or 299, but yup not the clearest of pics so entirely possible I am seeing things
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b78710
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RE: Virgin A346 Video: Why Is Gear Retracted So Late?

Fri Nov 19, 2010 3:56 pm

think its 265.

they only go up in increments of 5, so if the temp was 299 it would read 300
 
estorilm
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RE: Virgin A346 Video: Why Is Gear Retracted So Late?

Sun Nov 21, 2010 3:47 am

Oh wow the Airbus ECAM layouts are so freaking nice! Tremendous situational awareness; I'd love having that kind of information available whenever I wanted (same with the undercarriage cameras they've got now too).

Hard to believe that the Qantas A380 got up to ~900 deg. Add it to the list of ECAM warnings  

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