Originally Posted by
27/09
Landing roll will increase with altitude. This is because TAS increases relative to IAS with altitude. Even though you are touching down at the same IAS your TAS hence Ground Speed will be higher and it will take longer to stop.
Thanks, you're right. The initial kinetic energy will be higher at higher altitudes/temperatures at the touchdown and beginning of the landing roll. But unlike during the flare, at least the deceleration will be based on the friction of the brakes, tires and the pavement, not the rarified air.
It looks as if Diamond uses a higher figure than 1.3 Vs.
Yes, they do, I believe because of the very light construction of their planes, they want to keep at least 20 kts between Vso and recommended final approach speeds. Looking at their aircraft family, the higher the weight of their plane, the closer they get to 1.3 x Vso.
DV20 Diamon Katana (MTOW 730 kg)
Vso= 38 kts
Approach speed = 59 kts (
1.57 x Vso)
DA40 Diamond Star: (MTOW 1200 kg)
Vso = 52 kts
Approach speed = 73 kts (
1.40 x Vso)
DA42 Diamond TwinStar ( MTOM 1999 kg)
Vso = 64 kts
Approach speed = 86 kts (
1.34 x Vso)