Go Back  PPRuNe Forums > Flight Deck Forums > Rumours & News
Reload this Page >

Air Canada 767 Problems at Madrid

Rumours & News Reporting Points that may affect our jobs or lives as professional pilots. Also, items that may be of interest to professional pilots.

Air Canada 767 Problems at Madrid

Old 5th Feb 2020, 16:02
  #61 (permalink)  
 
Join Date: Sep 2019
Location: Outer ring of HEL
Posts: 1,676
Received 325 Likes on 104 Posts
Originally Posted by cats_five
And the entire tread is rotating at 100 knots around the centre. So, the very top is moving forwards at 100 knots
Very true. Not 200 knots.
Beamr is online now  
Old 5th Feb 2020, 16:22
  #62 (permalink)  
 
Join Date: Jun 2013
Location: Pittsburgh, PA
Posts: 112
Likes: 0
Received 0 Likes on 0 Posts
Originally Posted by cats_five
And the entire tread is rotating at 100 knots around the centre. So, the very top is moving forwards at 100 knots
Not true. The AXLE is moving forward at 100 knots. The top of the wheel is moving forward faster than that. (But no, not at 200 knots.)
MichaelKPIT is offline  
Old 5th Feb 2020, 16:48
  #63 (permalink)  
 
Join Date: Sep 2019
Location: Outer ring of HEL
Posts: 1,676
Received 325 Likes on 104 Posts
Originally Posted by MichaelKPIT
Not true. The AXLE is moving forward at 100 knots. The top of the wheel is moving forward faster than that. (But no, not at 200 knots.)
How come the top of the wheel moves onwards faster than the axle? To put it other way round, does the bottom of the wheel move forwards slower than 100 knots?
Beamr is online now  
Old 5th Feb 2020, 16:51
  #64 (permalink)  
 
Join Date: Mar 2002
Location: Florida
Posts: 4,569
Likes: 0
Received 1 Like on 1 Post
I love it when we get arguments like this I use to bet my wallet on being correct but I lost everything over the years

Yup the top of the tyre is going forward at the same speed that the bottom is going aft aft so it nets out as zero as long as it's attached to the aircraft,

But if a piece now leaves the aircraft it simply maintains the last vector that it was on when it was release (Forward, Aft or Up). That vector is made up of ground speed against the surface speed of the released fragment.

No bets until you work out the numbers. Of course one can always add in a moving runway like a conveyor belt or maybe an aircraft carrier to work your brain

lomapaseo is offline  
Old 5th Feb 2020, 17:10
  #65 (permalink)  
 
Join Date: Jun 2013
Location: Pittsburgh, PA
Posts: 112
Likes: 0
Received 0 Likes on 0 Posts
Originally Posted by Beamr
How come the top of the wheel moves onwards faster than the axle? To put it other way round, does the bottom of the wheel move forwards slower than 100 knots?
Yes it does. It moves forward at precisely 0 knots. Otherwise it would be skidding. In fact my previous statement about the top NOT going 200kt is actually wrong. Assuming the wheel is perfectly circular, and the axle is dead center, then yes, we have a 1:1 lever so the top IS actually going forward at 200. My apologies.
MichaelKPIT is offline  
Old 5th Feb 2020, 17:13
  #66 (permalink)  
 
Join Date: Sep 2019
Location: Outer ring of HEL
Posts: 1,676
Received 325 Likes on 104 Posts
Originally Posted by MichaelKPIT
Yes it does. It moves forward at precisely 0 knots. Otherwise it would be skidding.
so you are saying that the bottom of the tyre stands still.
yet at the same time you are saying that the top of the same tyre moves forward faster than the AC.
I really can't argue with that.
Beamr is online now  
Old 5th Feb 2020, 17:26
  #67 (permalink)  
 
Join Date: Jun 2013
Location: Pittsburgh, PA
Posts: 112
Likes: 0
Received 0 Likes on 0 Posts
Relative to the runway that's precisely what I'm saying. The very bottom of the tyre tread is moving at 0kt relative to the runway with which it is in contact. If not it would be skidding. The axle, x feet up from the runway is moving forward, relative to the runway, at 100kt (in this example.) The top of the wheel, 2x feet up from the runway, is moving forward, relative to the runway, at 200kt. The whole complete wheel, as a component piece, is obviously traveling forward at 100kt, however it is rotating, so the top has a forward velocity (speed in a given direction) greater than the axle or the bottom, and while the bottom is in contact with the runway, and is not skidding, it has the same forward velocity as the runway, which is obviously 0kt.
MichaelKPIT is offline  
Old 5th Feb 2020, 17:30
  #68 (permalink)  
 
Join Date: Feb 2001
Location: The Winchester
Posts: 6,548
Received 5 Likes on 5 Posts
Originally Posted by Beamr
so you are saying that the bottom of the tyre stands still.
yet at the same time you are saying that the top of the same tyre moves forward faster than the AC.
I really can't argue with that.
What ground speed do you think the bottom of a tyre of a moving vehicle is doing (any tyre, any vehicle....aircraft, car, bicycle ) when it is in contact with the ground ?





wiggy is offline  
Old 5th Feb 2020, 17:32
  #69 (permalink)  
 
Join Date: Jun 2013
Location: Pittsburgh, PA
Posts: 112
Likes: 0
Received 0 Likes on 0 Posts

A picture is worth a thousand words.
MichaelKPIT is offline  
Old 5th Feb 2020, 17:37
  #70 (permalink)  
 
Join Date: Jun 2001
Location: Rockytop, Tennessee, USA
Posts: 5,898
Likes: 0
Received 1 Like on 1 Post
Originally Posted by MichaelKPIT

A picture is worth a thousand words.
And the curve plotted by Point P is known as a cycloid. But all I know as a pilot is that a tire burst can sure FOD an engine on takeoff (or landing).
Airbubba is offline  
Old 5th Feb 2020, 17:54
  #71 (permalink)  
 
Join Date: Sep 2019
Location: Outer ring of HEL
Posts: 1,676
Received 325 Likes on 104 Posts
Originally Posted by wiggy
What ground speed do you think the bottom of a tyre of a moving vehicle is doing (any tyre, any vehicle....aircraft, car, bicycle ) when it is in contact with the ground ?
there is a difference in horizontal speed and rotational speed.
take any car, a drag car for instance: the wheels are warmed up before run, and the rotational speed is significant, but the wheel isn't going nowhere.
on the other hand, an airplane, after take off, the wheels stop spinning, but the wheels are moving just as fast as the AC.

so, regarding the circumferential speed: it is constant at every location on every spot with identical distance from the center, neverminding the speed or direction of the wheel.

What I understood from the message above is that a vehicle moving at constant speed N would have a rotating tyre of which the top section is moving onwards with the rate of N*1,1 and bottom section with the rate of N*0.

What I am trying to explain is that the wheel it self is really moving onwards at the horizontal speed N, and the rotational speed is a different factor that really does not affect the actual horizontal speed of the wheel.

Beamr is online now  
Old 5th Feb 2020, 18:00
  #72 (permalink)  
 
Join Date: Jun 2013
Location: Pittsburgh, PA
Posts: 112
Likes: 0
Received 0 Likes on 0 Posts
Originally Posted by Beamr
there is a difference in horizontal speed and rotational speed.
take any car, a drag car for instance: the wheels are warmed up before run, and the rotational speed is significant, but the wheel isn't going nowhere.
on the other hand, an airplane, after take off, the wheels stop spinning, but the wheels are moving just as fast as the AC.

so, regarding the circumferential speed: it is constant at every location on every spot with identical distance from the center, neverminding the speed or direction of the wheel.

What I understood from the message above is that a vehicle moving at constant speed N would have a rotating tyre of which the top section is moving onwards with the rate of N*1,1 and bottom section with the rate of N*0.

What I am trying to explain is that the wheel it self is really moving onwards at the horizontal speed N, and the rotational speed is a different factor that really does not affect the actual horizontal speed of the wheel.
I think you may be confusing angular velocity with linear velocity. You are absolutely right that every part of the wheel is ROTATING at the same angular velocity. The wheel as a component part of the aircraft is also moving forward, relative to the runway, at the same speed as the aircraft. However it is also rotating. The bottom of the wheel, in contact with the runway, and not moving relative to said runway, therefore has a LINEAR velocity of zero. Take another look at the image I posted above. It shows the linear velocity of a point element of the wheel as 0 when it's touching the runway and 160 km/h when it's at the top.
MichaelKPIT is offline  
Old 5th Feb 2020, 18:29
  #73 (permalink)  
 
Join Date: Sep 2019
Location: Outer ring of HEL
Posts: 1,676
Received 325 Likes on 104 Posts
Originally Posted by MichaelKPIT
I think you may be confusing angular velocity with linear velocity. You are absolutely right that every part of the wheel is ROTATING at the same angular velocity. The wheel as a component part of the aircraft is also moving forward, relative to the runway, at the same speed as the aircraft. However it is also rotating. The bottom of the wheel, in contact with the runway, and not moving relative to said runway, therefore has a LINEAR velocity of zero. Take another look at the image I posted above. It shows the linear velocity of a point element of the wheel as 0 when it's touching the runway and 160 km/h when it's at the top.
true, I got fixated with the term forward speed.
Beamr is online now  
Old 5th Feb 2020, 18:36
  #74 (permalink)  
 
Join Date: Apr 2014
Location: Wet Coast, Canuckland
Posts: 55
Likes: 0
Received 0 Likes on 0 Posts
ATC audio:
(Sorry if this is posted elsewhere in this thread)

hr2pilot is offline  
Old 5th Feb 2020, 18:42
  #75 (permalink)  
 
Join Date: Nov 2009
Location: Innisfil Ontario Canada
Posts: 17
Likes: 0
Received 0 Likes on 0 Posts
https://scontent.fybz2-1.fna.fbcdn.n...7a&oe=5ED5DA9C

Looks like a pic taken from the F-18 surveying the damage.

Last edited by ACA856; 5th Feb 2020 at 18:51. Reason: Pic detail
ACA856 is offline  
Old 5th Feb 2020, 19:14
  #76 (permalink)  
 
Join Date: Jun 2001
Location: Rockytop, Tennessee, USA
Posts: 5,898
Likes: 0
Received 1 Like on 1 Post
Originally Posted by hr2pilot
ATC audio:
(Sorry if this is posted elsewhere in this thread)
Thanks for the link, good job as usual by VASAviation.

I'm wondering why Air Canada chose to retract the gear with the fighter observing? They had known tire damage and needed to burn off fuel.

They said the left side brake temps were 8's after landing, hopefully the junior ground engineer was able to place those fans in time to prevent the fuse plugs from blowing.

I thought all B-763's had brake temp indications. Tower Dog and others set me straight that this was an option that some carriers like American did not order.

Seems like Air Canada disabled all 767 fuel dump systems years ago to save maintenance costs.
Airbubba is offline  
Old 5th Feb 2020, 19:21
  #77 (permalink)  
 
Join Date: Jun 2001
Location: Rockytop, Tennessee, USA
Posts: 5,898
Likes: 0
Received 1 Like on 1 Post
Originally Posted by ACA856
Looks like a pic taken from the F-18 surveying the damage.
Sure does. Is this flaps 5?



Airbubba is offline  
Old 5th Feb 2020, 20:07
  #78 (permalink)  
 
Join Date: Nov 2009
Location: Innisfil Ontario Canada
Posts: 17
Likes: 0
Received 0 Likes on 0 Posts
Airbubba - Appears to be Flap 5, and not all AC 767's had the brake temp indication IIRC. I was not aware of the fuel dump disabling on the AC 767's but I am old and memory is the second thing to go.
ACA856 is offline  
Old 6th Feb 2020, 00:16
  #79 (permalink)  
 
Join Date: Feb 2009
Location: Virginia
Posts: 2,078
Received 29 Likes on 23 Posts
Anyone still doubtful about wheels throwing debris forward should ride a bicycle through a mud puddle and then look at the back of their shirt. Fenders ruin the effect, of course.
Chu Chu is offline  
Old 6th Feb 2020, 00:32
  #80 (permalink)  
YRP
 
Join Date: May 2005
Location: Ontario, Canada
Posts: 163
Likes: 0
Received 0 Likes on 0 Posts
I love the use of YouTube for transferring serious aviation safety info.
YRP is offline  

Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

Copyright © 2024 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.