I was in Slough yesterday, which is 5 or so miles to the west of Heathrow, and looked up as a Virgin Atlantic 747-400 passed over. It was clear that the 27s were in use, so this aircraft was departing, but the landing gear was still in the down position, which surprised me.
Is this any reason why the landing gear would not be retracted shortly after departure, as normally seems to be the case?
By: GAZGLA - 1st June 2010 at 17:49
Almost certainly cooling. The gear-compartment has no fire-fighting capability and that place is chokka-block with flammable things. I think i’m right in saying a 707 or DC-8 (something along those lines) crashed somewhere a good while back due to a fire starting in the gear bay after take-off. The aircraft was quickly in flames and they couldn’t even complete the circuit to get back to the airport.
Gaz
By: Juan Tugoh - 30th May 2010 at 15:49
BA’s A320-100 series had no brake cooling fans and on short turn-rounds in the summer, with light return loads, brake cooling was often an issue. Sometimes leaving the gear down for a while after take off would sort this out, but as Fournier Boy states an inop brake pack would be more likely to cause the gear to be deliberately down after takeoff.
Incidently, it is very difficult to leave the gear down accidently as most airlines have an SOP for the non handling pilot to call “Positive climb” or some similar phrase as soon as they see a climb rate on the baro altimeter, rad alt and VSI. The response to this is always “Gear Up”. Indeed this becomes an almost Pavlovian response, so much so that leaving the gear down deliberately can be quite difficult to remember, once someone says the magic words the other pilot will always call for “Gear Up”
By: KabirT - 30th May 2010 at 11:28
yes the 300s nearly always seemed to have the landing gears down for a longer period of time than other aircraft. I have no idea why though.
By: MSR777 - 30th May 2010 at 10:40
Actually guys – its rare that the gear is left down after take off for cooling purposes (7 years as an airline line engineer and I’ve never heard of it) – yes they get hot on the taxi – but normally holding lets these cool.
The most common reason for leaving the gear down is if one or more brake packs is inoperable – a spinning wheel weighing 230lbs would twist the main gear beam if retracted whilst spinning (gyroscpoic principle from your school days!). If a brake pack is locked out – speed is generally reduced below norm after climb out and the gear held out for an extended period to alow the wheel to stop spinning. There are no wheel speed sensors on the B747 – only a rate of change of speed pick up that is used as part of the brake anti lock function. This is not indicated on the flight deck.
Hope this helps
FB
I remember that when the Air France A300s first started ops through LHR they seemed to do this every single take off.
By: SOFTLAD - 29th May 2010 at 13:15
Or mabye they had just forgot ?
By: Fournier Boy - 29th May 2010 at 00:12
Actually guys – its rare that the gear is left down after take off for cooling purposes (7 years as an airline line engineer and I’ve never heard of it) – yes they get hot on the taxi – but normally holding lets these cool.
The most common reason for leaving the gear down is if one or more brake packs is inoperable – a spinning wheel weighing 230lbs would twist the main gear beam if retracted whilst spinning (gyroscpoic principle from your school days!). If a brake pack is locked out – speed is generally reduced below norm after climb out and the gear held out for an extended period to alow the wheel to stop spinning. There are no wheel speed sensors on the B747 – only a rate of change of speed pick up that is used as part of the brake anti lock function. This is not indicated on the flight deck.
Hope this helps
FB
By: lucas - 28th May 2010 at 23:33
I saw the same thing, when I was in Windsor I saw an Air Canada A330-300 that had just departed Heathrow and its landing gear were out as you had described! Must be the cooling theory. Glad to clear that up, I stared at it for a while thinking ‘perhaps their landing gear retractor has failed!’ :rolleyes:
By: ThreeSpool - 28th May 2010 at 20:33
As mentioned by Arthur, the brakes and tires get hot from taxiing. But afterrotation the brakes are also used to stop the tires from spinning in their wheelwells.
Either that or someone forgot the gear-pins. :diablo:
By: tenthije - 28th May 2010 at 19:48
Why would the brakes be hot after a takeoff? :confused:
As mentioned by Arthur, the brakes and tires get hot from taxiing. But afterrotation the brakes are also used to stop the tires from spinning in their wheelwells.
By: Arabella-Cox - 28th May 2010 at 18:44
Brake cooling schedule. If they landed above a certain weight within a certain time before the takeoff. I forget the figures.:) Or they forgot:diablo:
By: Arthur Pewtey - 28th May 2010 at 18:42
Aircraft brakes and especially tyres get hot even taxying; especially at heavy all-up weights.
By: bloodnok - 28th May 2010 at 18:39
Why would the brakes be hot after a takeoff? :confused:
By: KabirT - 28th May 2010 at 17:54
allowing the breaks to cool perhaps?
I know the A300s of Indian Airlines in India’s summer times always were required to keep the gear down for sometime to let the breaks cool down.
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May 28, 2010 at 5:50 pm