Speed estimation ?

[FrankM]

As a f'up to the discussion about SQ286 or MK1602 I'm wondering if pilots can do a rough estimate of the Vr speed for a given distance of a flight or if the speeds can differ a lot with given load factor.
Don't get me wrong, I don't want to point my finger at anybody, but is it realistic that a pilot would think "hey, Vr = 130 for a 9 hour flight, that's hard to believe." ?

[Dmmoore]

VR is calculated from aircraft gross weight and field conditions (density altitude). The information was found in aircraft specific charts in the old days. Today the APLC computer provides the data.
Any pilot familiar with the aircraft should have a general idea (+/-5 ish knots) of the expected VR for any given gross weight. The variable factors would be temperature and barometric pressure.

[FrankM]

VR is calculated from aircraft gross weight and field conditions (density altitude). The information was found in aircraft specific charts in the old days. Today the APLC computer provides the data.
Any pilot familiar with the aircraft should have a general idea (+/-5 ish knots) of the expected VR for any given gross weight. The variable factors would be temperature and barometric pressure.

Don, thanks a lot for the answer. However, my question was more pointing into the direction, if a pilot without knowing the exact gross weight can estimate the Vr speed based on the distance of the flight only ?
Like, an 2 hour flight will be around 140knots, a 10 hour flight around 160 knots, etc.