Dash 8-100
 

has anyone any explanation for when calculating TO speeds, minimum weight from speed schedule is 14.5 tons. I understand rudder authority to be limited at zero flap but 0 is not a TO configuration. Also why is yaw damper on or off for 5 and 15 flap . There is no rudder limiter associated with yaw damper to my knowledge . Rudder pressure is regulated by speed

The Dash8-100 (depending upon mod status) has a statement in the AFM that take-off's should be with Yaw Damper OFF (unless take-off is Flap 5 at a weight greater than 14,400 kg). I did once know the reason for this but cant recall. I think it has something to do with V1/Controllability etc. Much like V1 min is higher when operating on narrow runways. Why is a good question!!!

Not sure what "speed schedule" you are referring to for calculating take-off speeds, unless it is a company document. In which case could be basing the data on weights above 14,400kg to permit Yaw Damper ON take-offs??

It has to do with Vmcg below 14,400kg. Supposedly there is a remote chance that should you have an engine failure below this weight and you have the yaw damper on it may and I repeat may- remote chance of course, on a narrow strip ie less than 30meters cause you to run off the strip. Of course all other limitations such as X/wind of 36 knots max still are ok.
A classic case of ass covering by a big manufacturer.