737 Taxy Crabbing

[UNC]

Why do B737 taxy in a crabbing fashion notable when viewed from infront and behind?

[STBYRUD]

Because of play in the torque links of the main gear struts... Others blaim the coriolis force ;)

[BOAC]

Others reckon it is purely due to the PPRune search function:)

[CaptainSandL]

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.

[Golden Rivet]

play in the torque links........:rolleyes:

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.

[RAT 5]

And I always thought it was to give a higher cross wind limit from the right (capt landings) than from the left.

[Biggles78]

So that will be why a right turn taxiway has a larger radius than a left turn taxiway. :eek: :hmm:

[BOAC]

Only in the southern hemisphere.

[411A]

On cloudy days.

[Romeo E.T.]

on the "classic" 732 it was to allow for the torque of the rotating beacon

[Capt Claret]

You mean it's not because of the thronmeisters? :eek:

[oxenos]

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).

[CaptainSandL]

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 ;)

[startingout]

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. :}

[PLovett]

There you go UNC. That'll teach you to post on PPRuNe.:}:ok:

[Loose rivets]

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.

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.


Can't you use differential power, or does that burn the brakes too much?

[Oakape]

Loose rivets,

Don't the words "more right engine", used on two occasions, indicate the use of differential power? :hmm:

[BOAC]

the torques dont exactly cancel out because - you have of course omitted to take into account the fact that the upper beacon has a higher groundspeed than the lower as per the 'ATCast' thread..

[nitpicker330]

Not this again ..................:mad:

:{:{:{