Under-rotation and FDM (FOQA) events
We all know about over-rotation and the risks associated. Well, what about under-rotation? I fly for a 737 operator that has become increasingly interested in rotation rates as part of its FDM analysis. Recently, they have been pushing low rotation rates as a risk factor. The argument is that low rotation rates mean that the aircraft is not able to meet calculated performance figures and that is a risk. The airline safety magazine tells us that a good rotation rate is 3 degrees per second and that if this is achieved we will be V2+20 by climb out attitude.
I do have my doubts about some of what they are saying and the extent to which this is considered a threat. While the FCTM states under-rotation will cause problems, it states 2-3 degrees as the rotation rate. 2-2.5 degrees is quite slow and (I suspect) would trigger an FDM event. But would, it truly prevent the aircraft from meeting the performance calculations? As for meeting V2+20, by climbout attitude; well a lot seems to depend on aircraft weight. We often fly very light, and rotating at a normal pitch rate results in speeds in excess of V2+20. Yet the aircraft climb rate is rocket like.
So, when do you consider under-rotation to be a problem and when will it truly cause problems in meeting performance calculations?
Last edited by Fair_Weather_Flyer; 13th March 2018 at 11:54.