Originally Posted by Scoop

We had a MD-90 that Captains used to call "Flipper" all the way back in 2005/2006 when I was flying the 90's out of SLC. It would very mildly, yet constantly porpoise up and down when at cruise with the AP on, thus the "Flipper" moniker.

Also, this was before we got the 90s from China, so unless there is another Flipper I'm not sure the "China" part is deserved.

Scoop