5
$\begingroup$

I notice on some commercial flights that the aircraft can begin to swerve left-to-right during takeoff before we leave the ground. Sometimes this can become very exaggerated, very hard left-to-right swerving. This is typically from around mid-way through the takeoff run, becoming most severe immediately before takeoff.

My first thought was perhaps it is an inconsistency in the runway from the airport I frequent but have noticed it once or twice at other airports as well, and across different carriers. However, it feels more like when driving a car and you swerve, then overcompensate the other direction and it becomes a vicious cycle.

Other factors may include wind - but I've been in high-wind takeoffs before and it didn't have the same jerking motion.

Any explanation to this, or am I just paranoid?


*Apologies for lack of knowledge re: terminology

$\endgroup$
  • $\begingroup$ turbulence from the previous flight perhaps? $\endgroup$ – ratchet freak Jul 24 '14 at 17:26
  • $\begingroup$ It is probably nothing. But, a few questions. What size plane are your usually flying on? (Smaller planes move easier.) Is it common for the airport your usually fly from have crosswinds? (Crosswind means as soon as you lift off some control input is required to get the nose of the plane turned into the wind.) Do you sit in the back of the plane. (Center of rotation is further away in the wings. Any rotation is more pronounced further away). $\endgroup$ – JerryKur Jul 24 '14 at 20:43
  • $\begingroup$ I most often fly Jetblue (A320) from PBI to JFK and have experienced it on Southwest (737-800) from FLL->LAS. I don't think I've ever experienced crosswinds at PBI or JFK; I think I'd remember it! $\endgroup$ – philwinkle Jul 24 '14 at 20:47
7
$\begingroup$

I know you said that you don't think it's a crosswind, but honestly it most likely is. As the plane speeds up and the wings start to generate more and more lift the plane is more easily affected by cross wind. So, as you speed up, it gets harder and harder to keep the plane straight. Throw in some gusts, and you're going to get some jerking motions as well. Especially if that gust decreases the lift of the aircraft, the wheels suddenly catch the ground more and the craft is suddenly tugged harder than the pilot anticipated...

Here's a video of a Boeing 777 taking off in a heavy crosswind that should illustrate the point more.

$\endgroup$
4
$\begingroup$

Crosswind can cause it, especially if there are gusts involved. It would be more common on turboprops as well since they have more left turning tendencies from the engines, such as torque, p-factor, etc. In these airplanes the pilot has to compensate by holding right rudder, and sometimes they end up swerving a little bit as they try to find the right balance.

In any case, the swerving is not nearly as bad as it feels, the farther to the back you are the more you're going to feel it as well.

$\endgroup$
1
$\begingroup$

I am not an expert, but it could be because the main Yaw control moves from the nose wheel to the rudder. During slow flight, you need to be more forceful on the rudder as there is not much control.

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.