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What Makes A Jet "Fish Tail" After T/O?

Mr Spaceman From Canada, joined Mar 2001, 2777 posts, RR: 18
Posted (10 years 5 months 3 weeks 2 days 15 hours ago) and read 2321 times:

Hi guys.

An N.T.S.B. report states: On Wednesday, November 28, 2001 an American Airlines A300-600 (N7055A) reported "fish tailing" soon after takeoff from Lima, Peru. The flight returned to land at Lima without injuries. The flight recorders were pulled pending possible readout.

My questions are: What does the term "fish tailing" mean with regards to an airliner's performance after takeoff?

Also, could this have something to do with un-commanded movement of the aircraft's rudder?

Here's a pix of the A300 involved in this incident.

Click for large version

Photo © Chris Liao

Chris Smile

"Just a minute while I re-invent myself"

5 replies: All unread, jump to last

61Heavy From United States of America, joined Oct 2001, 62 posts, RR: 0
Reply 1, posted (10 years 5 months 3 weeks 2 days 14 hours ago) and read 2261 times:

"Fishtailing" would mean back and forth movement around the vertical axis. It could caused by uncommanded rudder movement but I would guess that it was more likely a failure of the yaw damper system.

http://seattletimes.nwsource.com/news/nation-world/html98/rudd16_20000416.html says:

"The rudder, a movable flat panel at the rear of a plane's vertical tail fin, is most often used to prevent fishtailing, also called a "Dutch roll," as the plane comes out of turns or enters turbulence. Most of these movements are controlled automatically by a mechanism called a "yaw damper." The rudder is also a vital control mechanism to keep a plane flying straight if one of its two engines malfunctions. "

Mr Spaceman From Canada, joined Mar 2001, 2777 posts, RR: 18
Reply 2, posted (10 years 5 months 3 weeks 2 days 13 hours ago) and read 2219 times:

Hi 61Heavy. Thank You for your reply.

Because I've never heard the term "fish tailing" used before regarding an aircraft that's flying (we've all heard this term refered to when a car's rear end starts to lose traction), I thought it might have been a more complex situation that airline pilots have to deal with on a regular basis. Perhaps they would if there wasn't the normal presense of a Yaw Damper.

Obviously, this A300 incident must have caused quite a stir if the N.T.S.B. decided to remove the FDR's for clues as to the cause. This airliner must have really been wagging it's tail after takeoff.

Chris Smile

"Just a minute while I re-invent myself"

USAFHummer From United States of America, joined May 2000, 10685 posts, RR: 57
Reply 3, posted (10 years 5 months 3 weeks 1 day 6 hours ago) and read 2114 times:

I believe fish tailing is a rudder movement along its full range of motion, it looks like a fish's tail moving back and forth, so I assume thats why its called that...

Greg

Chief A.net college football stadium self-pic guru

Twotterwrench From , joined Dec 1969, posts, RR:
Reply 4, posted (10 years 5 months 3 weeks 1 day 6 hours ago) and read 2106 times:

Fishtailing is not always rudder induced. I would say in my experience the most likely cause is a failed yaw dampner. I do remember a Twin Otter that started fishtailing very badly after the rotating beacon on top of the vert stab was changed. After several days of not being able to fix it, the crew finally refused to take the aircraft anymore. We looked back through the records and found the last thing done before the problem showed up, and lo and behold it was changing the beacon. The beacon was removed and everything was peachy after that.

Airplay From , joined Dec 1969, posts, RR:
Reply 5, posted (10 years 5 months 3 weeks 8 hours ago) and read 2075 times:

I wonder if not being familiar with the term "fishtailing" comes from living in a warm climate.

I've lived in an area where it gets cold in the winter. Fishtailing is something that cars do when traction is lost in the rear end. Like when you take a sharp turn on ice.

I'm assuming the fishtailing of the aircraft is similar to the action of a fishtailing car.

Smile

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