OK, so here's a question for anyone with knowledge of AC Airbus A340 SOP's....
I have noticed several times recently that departing YVR (everytime I have seen this its been off the 8's) Air Canada A340's seem to leave their gear hanging out for an abnormally long time before raising it? And I mean a long time - like until east of the Knight Street bridge, easily above 1500ft agl and sailing off in the distance towards the Alex Fraser and the valley...
Any ideas? Seems pretty odd to me. I mean those things climb like sh*t anyway...
The 340's gear is raised at the same time every other aircraft's is, when there is positive rate of climb. There are at least two reasons why it might be delayed.
1. To blow slush off the gear if the runway was contaminated before raising it.
2. If one brake is deactivated, the gear is usually left down to give the tire time to spin down before retracting it into the well. The wheels are normally automatically braked on gear retraction except if the brake is deactivated.
I don't know what the cause could have been in the planes you witnessed.
I wouldn't think they would use brakes as there would be a chance of tires spinning on the rim. They tend to have a buffer pad installed in the wheelwell to stop the spinning. that said, I don't fly either of those birds
The main wheels are braked by the normal brake system when the gear handle is placed up. The nosewheel is in fact stopped by a scrubber in the nose well.
rigpiggy wrote:I wouldn't think they would use brakes as there would be a chance of tires spinning on the rim. They tend to have a buffer pad installed in the wheelwell to stop the spinning. that said, I don't fly either of those birds
The tire wouldn't spin on the rim with no weight on it... or with weight on it for that matter, it would simply disintegrate...and as mentioned before the brakes are actuated by a shuttle valve that is hooked up in tandum with the gear select handle (or system in the case of the Airbus).
most know why the wheels are stopped first before the gear is raised but for those who don't I will try and explain...gyroscopic precession (definition: http://www.howstuffworks.com/gyroscope1.htm ) is the main reason we want them stopped and almost as important we don't what a shredded tire flapping around in our wheel well breaking stuff.
They likely have one of the brakes de-activated, which gives no temperature indication. Sounds like they're trying to cool the brake before bringing it up. The normal braking system stops the tires when in the wheel well, and a scrubber for the nose gear.
once you get on the 340 at air canada you are to lazy (and in retierment mode) to even bother with the gear. "oh no a handle instead of a button. I don't want to get it you get it"
You have four freakin engines, who cares when the f-ing gear comes up. If you lose 1 fan, no biggie, & at least the gears down if you're coming back. Do the flow, if you don't get it there, the checklist will take care of it!
Then why do we put a BIG RED ARROW ON THE RIM and TIRE when we put them together
Troubleshot wrote:
The tire wouldn't spin on the rim with no weight on it... or with weight on it for that matter, it would simply disintegrate...and as mentioned before the brakes are actuated by a shuttle valve that is hooked up in tandum with the gear select handle (or system in the case of the Airbus).
most know why the wheels are stopped first before the gear is raised but for those who don't I will try and explain...gyroscopic precession (definition: http://www.howstuffworks.com/gyroscope1.htm ) is the main reason we want them stopped and almost as important we don't what a shredded tire flapping around in our wheel well breaking stuff.
I'm not an engineer Rigpiggy, but I'll bet that going from zero to 150 knots instantly at 200 feet per minute down with 140 metric tonnes behind it puts a lot more shear force on the tire and rim than a gradual deceleration with no weight behind it.
I really think the shear markers on the tires are for landing and not takeoff. The mains are braked automatically when the gear selector is placed up, and since the nosewheel doesn't have brakes it has the scrubber fitted in the nose well.
rigpiggy wrote:Then why do we put a BIG RED ARROW ON THE RIM and TIRE when we put them together
Troubleshot wrote:
The tire wouldn't spin on the rim with no weight on it... or with weight on it for that matter, it would simply disintegrate...and as mentioned before the brakes are actuated by a shuttle valve that is hooked up in tandum with the gear select handle (or system in the case of the Airbus).
most know why the wheels are stopped first before the gear is raised but for those who don't I will try and explain...gyroscopic precession (definition: http://www.howstuffworks.com/gyroscope1.htm ) is the main reason we want them stopped and almost as important we don't what a shredded tire flapping around in our wheel well breaking stuff.
CAP LOCK IS FUN....now to answer...the red dots or arrows as you so quantly pointed out are for smaller aircraft and tires with tubes, now they still put the red dots on large transport aircraft tires but I assure you my friend if a tire started to spin on the rim of a A340 there would be no red dot or arrow to look at, the shear energy it would take to move tire would destroy the tire instantly .
Gentlemen;
That would have been fin #983 that you saw. It has been operating for several days with the #5 mainwheel brake removed as it was damaged.
Normally, when the gear is selected up, the brakes are automatically applied to ensure the wheels are not spinning when they get into the wells.
When the brake has been removed from a wheel, there is a modififed procedure for flightcrew to follow in the MEL that directs leaving the gear down for two minutes after liftoff to give that wheel time to spin down to a stop.
If an engine failure is experienced during that delay, the gear is raised immediately.
