As soon as we left the apron area, we were taxing what was looking like faster than 20 kts... But even if we want to stay away from the discussion of what 20 kts looks like, I thought ACA had stated somewhere in their SOP that the planes were to be taxied in accordance to passenger comfort or something along those lines?
I don't know if we were trying to make up for time, or if the pilot was having a rough day or what ever, but the taxiing was more exciting than the take off..
I'm not intending to start an anti air canada thread, I'm just curious as to how my experience on the ACA A320 today reflects all my other experiences with ACA? Considering that not too long ago, there was a thread right here on avcanada with you boys going at it about how ACA holds you up because of their slow taxing... Interesting stuff.
Thanks
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Last edited by loopa on Mon Mar 22, 2010 6:59 pm, edited 1 time in total.
I'd like to say I'm sorry if I seem to have been harsh with my previous response. There can often be much negativity thrown against team Red in these forums and without having a clear indication of your intentions it was a defensive response. Thank you for taking the flight details down.
Glad you're interested in learning. It never stops in aviation.
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Last edited by TyrellCorp on Fri Mar 26, 2010 2:17 pm, edited 2 times in total.
"Nothing is worse than having an itch you can never scratch"
Your intentions are transparent. Identifying the airline AND flight number AND date is lowest of the low
Take your shite elsewhere.
I hope no one else responds to this post and attempt to cause a shite slinging fest.
Sorry dude, but I'm not trying to throw anything at anybody here. I'm just curious as to what might of been going on? I was totally oblivious to the fact that including the flight details might get somebody into trouble because I wasn't even thinking about it of being horrifying. I just found it to be an interesting contrast to what was being discussed here not too long ago. But as a side note, if what the pilot was doing was correct, what difference does it make if the flight and date are included? But just in case, I have edited that info as my intentions are not to get out after any body.
I have got some good friends at Air Canada who I've also addressed about this inquiry, I didn't get the same attitude you just showed me there. I just wanted your guys' insight on it as well. I suppose my intentions were misinterpreted.
My 2 cents.
Maybe somebody who understands my genuine inquiry might have something better to add... I'm trying to learn something, because I imagine there's an operational logic to what was done today that wasn't done on many of the previous ACA flights I've been on.
Wear on carbon brakes is related to the number of brake applications as opposed to the duration. Therefore we are instructed to let taxi speed build to 30 kts, then use one brake application to slow the speed to 10 kts repeating as necessary. Lightly riding the brakes as one would on steel is the opposite of good technique for carbon brakes. When the aircraft is light as one would be on a short flight to Vancouver, this technique can make for a bit of a rough ride. Combine that with a downhill taxiway like Calgary's (to RWY34) and it can appear that speed is building up quite rapidly. If there is no specific reason not to, the Captain may have let the speed build to over 30kts before slowing, to reduce brake wear.
Gee I hope that incident doesn't make the Globe and Mail!
Dockjock wrote:Wear on carbon brakes is related to the number of brake applications as opposed to the duration. Therefore we are instructed to let taxi speed build to 30 kts, then use one brake application to slow the speed to 10 kts repeating as necessary. Lightly riding the brakes as one would on steel is the opposite of good technique for carbon brakes. When the aircraft is light as one would be on a short flight to Vancouver, this technique can make for a bit of a rough ride. Combine that with a downhill taxiway like Calgary's (to RWY34) and it can appear that speed is building up quite rapidly. If there is no specific reason not to, the Captain may have let the speed build to over 30kts before slowing, to reduce brake wear.
Gee I hope that incident doesn't make the Globe and Mail!
Thanks Dock that's exactly the kind of answer I was looking for. An Operational logic that I wasn't aware of
There is yet another reason for letting the speed build and slow with one application other than wear. Less heat in the brakes. The hotter the brakes, the less braking energy you will get out of them if a reject is required. In fact most modern aircraft, if not all, have a max brake temp for takeoff. Usually only relevant in a hot climates like LAS. There the 25's are down hill and on hot days sometimes troublesome for break temps. For someone not knowing why, it must be kinda funny to see a line of aircraft do the speed up, slow down dance, all the way to the threshold.
I suspect though your experience has nothing to do with any of the above posts. It is easy to forget the impact we are having at the rear of the aircraft while in a sharp turn. It is moving side ways, (and in the opposite direction of the driver) at much greater speed than the front end. Bumps will do it too, only vertically. If the nose gear hits an unexpected bump at higher speeds, the oleo gets compressed and then extends extends making the back end move first down then up like a seesaw. The longer the aircraft the greater the effect. It is why you don't see widebodies taxiing very fast.
loopa wrote:Thanks for that awesome insight Brick Head. I'm glad you guys are realizing what my intentions were... to learn.
I imagine that you have a certain restriction on brake temps in case of rejecting a take off right?
No I was sitting 1 seat aft of the wing. Seat 24A on the A320.
Learning's good. Removing the flight details was the right thing to do. There's too much Red vs Teal on these boards as it is. One can learn without isolating the airline or crew.
loopa wrote:Thanks for that awesome insight Brick Head. I'm glad you guys are realizing what my intentions were... to learn.
I imagine that you have a certain restriction on brake temps in case of rejecting a take off right?
No I was sitting 1 seat aft of the wing. Seat 24A on the A320.
Learning's good. Removing the flight details was the right thing to do. There's too much Red vs Teal on these boards as it is. One can learn without isolating the airline or crew.
All Transport Aircraft are limited to 30 knots taxi speed. This is a certification limit on the tires. If the speed exceeds 30 knots, the sidewalls will overheat, and the tire may fail; on this flight or another. This is a limit, not discretionary. The other limit on Transport Aircraft tires is 35,000 feet of lineal roll.
This 30 knot limit is the reason for the "recommended" procedure. It is stated as a hard limit in the Airbus AOM, and a procedure in Boeing manuals. Not aware of the Embraer manual. but it is a limit on Part 25 certification. It is poorly understood by pilots in general and management/training in particular.
Help me understand and learn as well. 30 knots for taxiing is a certification/limit on the tires, but during T/O and LDG...this limit is far exceeded. It must be a timing thing there? ie. speeds above this must not exceed "x" amount of seconds/minutes?
The 30 knots is a taxi speed limit; presumably T/O and Landing are allotted a temperature rise over the longest possible T/O and landing period/speed. (The longest T/O roll I have seen was 65 seconds on a 340-300 in Delhi) There is no time limit on the taxi that I am aware of; the 35,000 feet is for one departure, or one arrival. There is presently no way for a crew to determine tire temperature, only brake temps.
Underinflated tires will overheat much more quickly; thus, newer aircraft are coming with tire pressure readouts. Also, if one tire on an axle is found underinflated by a certain percentage that tire and its mate are scrapped, becuse the underinflated tire has been overheated, and the adjacent one was overloaded.
115B wrote:The 30 knots is a taxi speed limit; presumably T/O and Landing are allotted a temperature rise over the longest possible T/O and landing period/speed. (The longest T/O roll I have seen was 65 seconds on a 340-300 in Delhi) There is no time limit on the taxi that I am aware of; the 35,000 feet is for one departure, or one arrival. There is presently no way for a crew to determine tire temperature, only brake temps.
Underinflated tires will overheat much more quickly; thus, newer aircraft are coming with tire pressure readouts. Also, if one tire on an axle is found underinflated by a certain percentage that tire and its mate are scrapped, becuse the underinflated tire has been overheated, and the adjacent one was overloaded.
So am I correct in understanding that the 35 000 will never be reached on a take off or landing? I don't know of any runway that is 35 000 feet long.
[/quote]So am I correct in understanding that the 35 000 will never be reached on a take off or landing? I don't know of any runway that is 35 000 feet long.[/quote]
Now that would be one loooong runway. Thats like 6 miles.
nice. I am stealing that one.
