Landing gear raising question
 

Spending many a Sunday watching aircraft comming and going at fajs I noticed a SAA Airbus A319 take approximateley 3 minutes before he raised his gear after take off.He must have climbed at least 3 thousand feet before he decided to raise his gear.This is not normal,did he forget I wonder as I doubt there was a problem as he seemed to proceed toward his destination as I know the standard routes traveled.Any Comments?

Brakes must have been very hot so left out to cool.

Must be true as it was about 33 degrees C oat that day

Can be a MEL restriction if one of the brake caps is missing and the brake temp indications are not present. The MEL calls for the gear to be left down to assist in the cooling of the brakes.

There is a take off restriction of 300 degrees or 150 degrees with brake fans fitted. Take off must be delayed if the temp is over this.

Been discussed here before, possible brake deactivation, must be left extended until spin down.

With a combination of combined conditions, such as high altitude airports, of South America and the western part of the US, high temperatures, and heavy take off gross weights can cause the aircraft to approach its tire limit speeds. Not all aircraft back then were equipped with the 225mph tires. Its far safer to allow the wheels to slow their spinning effect prior to retracting the gear. This is also true if there is a wheel slightly out of balance. This also allows the wheels to cool down too. Some aircraft have inportant components in the main wheel well that could be damaged in the event of a tire burst that could effect the safety of flight if a tire were to burst after gear retraction.

This procedure is briefed before blocking out. It was understood that the gear would be retracted if performance requirements dictated.

Very hot day, short "on ground" times, a bit of braking action when taxiing to the runway, and you get a hot brake. Action for the crew is to let it all hang out in the wind to cool before retracting it in the well.

Hot brakes, he just left em out to cool for some time.
On our busses we wait until ecam warning to start the fans, it happens that
things getting a bit hot on departure, but just leave em out to cool, no drama!

None of this makes sense. If the brakes were "hot" to begin with, then they should not have started the takeoff roll (due to the possibility of a rejected takeoff.) If they are cool enough for a takeoff, then they should definitely be cool enough to just retract normally.

JNB.
L1011-500.
Flaps 4 takeoff.
After rolling 13,000 feet on the takeoff run, the wheels are left extended for possible tire/wheel heat problems, unless the performance dictated otherwise.
A standard procedure, even with 225 MPH tires, which are a standard fit on the aeroplane.
It is called...Captains decision.
That is what we are paid the big bucks for....:D

formulaben
'If the brakes were "hot" to begin with, then they should not have started the takeoff roll..'
Depends on what you mean by hot :uhoh:
If the brakes are 'warm' but below the 300 limit then you are safe to depart. On a short sector and with short turn around times the brakes will not cool very quickly. Therefore it is good practise, bearing in mind performance, to cool them down when you can.
We often taxy the 340 on 2 engines to reduce the brake use after landing.
Regards,
HD :ok:

Early deployment
 

Once at TOD for Urumqi (Xinghiang) the IL 86 extended the gear prior decending . Guess for an extra help for drag regardless icing fears or speeds limits (wich I m not aware )
another occasion it was clear to me that our Singapore Ailine 747 has been called to loose altitude very quicky so they lowered the gear much early than ususal (10 miles in stable aproach are like 5 minutes from contact) the vibration was amazing and just when we were floating in gound effect I head the next flap setting!!! followed by a change of CG (nose down) and the expected suddern big BUM! of the landing gear to the tarmac. we stopped without events but you could smell the brakes when we disimbarked the ship
cheers!

Somehow I am reminded of the tube journo, during one of the Apollo moonshots, who could not get "Max G" and "Max Q" sorted out in his head. :}

I can only speak for the small bus, leaving the wheels down for cooling is ridiculous, if you don't have brake fans and your brakes are hot, you simply delay your departure.:ugh: As mentioned earlier, the MEL calls for the landing gear to remain extended, two minutes when deactivated.

Some of you guys need to stop pontificating about stuff you don't know. Managing gear temperature for larger and longhaul aeroplanes is essential If you have hot brakes on a turnaround and have to taxi out, they get even hotter. Then doing a take-off heats them up more, and can mean in the event of a reject that you will lose all the tyres anyway. Rather than retract hot brakes, leaving the gear dangling for4 or 5 minutes can be worth 40+ minutes cooling on the ground. A 747 on a couple of short flights will quickly run into problems. If you think you have the luxury of waiting for brakes to cool before every take-off, you are going to ground half the aeroplanes out there, so Cessna experience doesn't really apply here!

Zagorfly- that is a glowing example of how you can get the totally wrong impression of what is going on on an aeroplane from sitting in the cabin. It's touching and funny, but you are so wrong it's not even worth correcting you!

And then there are those who skip the first post. :}

BTW, I've been 3000' plus by the departure end of the runway in a light BUS before :eek:
All this is nice and well but the brake issue calls up a large number of things. The MAX autobrake will stop the aircraft damn quickly upto V1. The problem at this stage is then brake heat dissapation due to the fusable plugs in the gear blowing at around 800-850 degrees and giving you the added bonus of flat tyres. Brake fans, hubs and tachometers don't stop the brakes being applied upon retraction to stop wheel rotation, this is supplied from the hydraulics (through the yellow system I believe i.e. the parking brake system). A defective tachometer or missing brake hub will not supply wheel rotational velocities to the autobrake system due to the fact that the anti-skid believes the wheel to be stationary and therefore would not apply any braking to it anyway.
Carbon brake discs work better at high temperatures but have peak brake wear between 200-300 degrees therefore the brake fan policies of many companies.
The case here of the gear left dangling is purely for cooling reasons and is called for in the minimum equipment list (MEL) for specific dispatch with missing or failed components. Bizzarely the wheels keep very warm even during a long transit and dispatch with high brake temps will give you possible problems when operating to a performance restricted runway (short!).
Hope that helps.

This requirement is only there for the cases where the brake temperatures are not visible on ECAM and the brake temperatures have been calculated from the performance manual graphs. Belt AND braces :ooh:
:E

quote: "None of this makes sense. If the brakes were "hot" to begin with, then they should not have started the takeoff roll"

It makes sense, do you really think a captain would delay a flight because of hot brakes? I'm not talking about fuse plugs that are gone and warning lights that went off, that's indeed another story. You don't need OVERheated brakes to decide to let them hang in the air a few moments more.
There are even aircraft where a "hot" switch is installed that acts on the retract solenoid in the gear lever, to prevent gear retraction. Some kind of automatic system, the pilot selects up, but the aircraft negotiates when to do the gear up by itself.

IMO, yes, that's why they call it a takeoff limitation :}

Piper 19,

Yes the flight would be delayed if the brake temps are above 300 degrees with fans off or not fitted and 150 degrees if the fans are on (This is due to the brilliant design of the brake fans blowing directly onto the thermocouples! Designed by Porsche, built by Renault!)

This is a pre takeoff requirement and has bitten me a couple of times whilst on short turnrounds with short runways and a c**p old airbus with no brake fans.