737 Taxy Crabbing
Joined: Nov 2003
Posts: 496
Likes: 12
From: UK
This has come up every other year since PPRuNe began.
Click "Search" at the top of this page, then type in 737+taxi+crab and you will find half a dozen threads on this subject.
If you cant be bothered, I can tell you it is due to the torque reaction of the over-powerful anti-collision lights fitted to this type. They considered a mod which mounted the upper & lower anti-colls so that they rotated in the opposite direction but binned it due to the cost so we live with the crab.
Click "Search" at the top of this page, then type in 737+taxi+crab and you will find half a dozen threads on this subject.
If you cant be bothered, I can tell you it is due to the torque reaction of the over-powerful anti-collision lights fitted to this type. They considered a mod which mounted the upper & lower anti-colls so that they rotated in the opposite direction but binned it due to the cost so we live with the crab.
Joined: Feb 2001
Posts: 461
Likes: 0
From: UK
play in the torque links........
The real reason is that the torque links have a shimmy damper between them (which can often be seen extended on a tight turn onto stand).
This can cause the whole axle to turn, relative to the leg, by a few degrees.
The real reason is that the torque links have a shimmy damper between them (which can often be seen extended on a tight turn onto stand).
This can cause the whole axle to turn, relative to the leg, by a few degrees.
Joined: Apr 2008
Aviation Qualifications: ATPL
Posts: 836
Likes: 101
From: uk
The rotating beacon theory is nonsense. The lower rotating beacon is mounted upside down, it rotates in the opposite direction to the top one, and the torques would cancel out.
I believe it is the fact that the nav lights are on different frequencies, (i.e. red is a lower frequency than green).
I believe it is the fact that the nav lights are on different frequencies, (i.e. red is a lower frequency than green).
Joined: Nov 2003
Posts: 496
Likes: 12
From: UK
Oxenos, nice try but the torques dont exactly cancel out because the upper anti-coll is at a larger radius (6.38x10~6m +10m) than the lower one (6.38x10~6m +2m) so the angular velocity (w=v sin(theta)/r) is greater.
The differing nav light frequencies merely exacerbate the above effect
The differing nav light frequencies merely exacerbate the above effect
Joined: May 2008
Posts: 258
Likes: 0
From: Tin Shed corner Bourke and Swanston
I have this uncle, who knows a guy, who said his brother worked in dispatch for this airline, one day he was talking to one of the el' capitan's who gave him this long story about this weird thing called P-Factor, supposedly it hurts the airframe so much in these boeings that they crab along as a sign to say that they are almost about to roll over and beg for mercy. 
Psychophysiological entity
Joined: Jun 2001
Aviation Qualifications: ATPL
Posts: 3,383
Likes: 169
From: Walton on the Naze Essex.
Then there was the crab that couldn't marry the lobster princess cos he walked sideways. One day he turned up in front of the lobster king, walking as straight as a die. The King was amazed and the princess delighted.
Why? etc., etc.
I always walk like this when I'm pi$$ed.
He never became a prince.
Then again, you blokes don't know y'er born.
Can't you use differential power, or does that burn the brakes too much?
Why? etc., etc.
I always walk like this when I'm pi$$ed.
He never became a prince.
Then again, you blokes don't know y'er born.
This thread has just brought back a horrible memory of my first command days on a Dak.
Taxiing at Amsterdam, Highway on the right - down below a steep bank; cars whizzing by. Strong X-wind. Left brake fading, more right engine. Going faster. Both of us standing on the left brake. Swinging right, more right engine...even better view of cars. More engine - more speed. Considered Mayday and taking off on taxiway. Considered throwing some of the bricks that I was sitting on, out and under the left wheel. Ug! Bag brakes.
Taxiing at Amsterdam, Highway on the right - down below a steep bank; cars whizzing by. Strong X-wind. Left brake fading, more right engine. Going faster. Both of us standing on the left brake. Swinging right, more right engine...even better view of cars. More engine - more speed. Considered Mayday and taking off on taxiway. Considered throwing some of the bricks that I was sitting on, out and under the left wheel. Ug! Bag brakes.
Can't you use differential power, or does that burn the brakes too much?
Per Ardua ad Astraeus
Joined: Mar 2000
Posts: 18,575
Likes: 4
From: UK
Originally Posted by CaptainSandL
the torques dont exactly cancel out because
