The discussion of manouvering speed in the gross weight thread got me thinking about the manouvering speed Vans publishes.
The applicable formula that I remember from early flight training and Vans has in the Builders Manual is Va = Vs x sqrt[max g load].
So I did the math for the RV-8 with the "dash 1" wing.
142 = 64 x sqrt[g load]
g load = 4.9
Knowing that normally the stall speed is published for gross weight, I wondered if 4.9g would overload the wing at 1800lbs. The wing is designed for 6g at the aerobatic weight of 1600lbs.
1600lbs x 6g = 9600lbs
so, 1800lbs x 4.9g = 8820lbs
Yes, the wing can withstand 4.9G at 1800lbs. Those numbers are close enough to me to assume Van's published manouvering speed is for the applicable G limit at 1800lbs, with a safety buffer.
So, what is the manouvering speed at 6g and the aerobatic weight of 1600lbs? We all know that weight affects stall speed, and a few mph will make a big difference at 6g. So we'll decrease the stall speed to 60mph at the 1600lb weight. (I used the formula: new stall speed = old stall speed X sqrt[new weight / old weight])
Va = 60 x sqrt[6]
Va = 147mph
Cool. But it is safer to use the published 142mph as a safety buffer.
The applicable formula that I remember from early flight training and Vans has in the Builders Manual is Va = Vs x sqrt[max g load].
So I did the math for the RV-8 with the "dash 1" wing.
142 = 64 x sqrt[g load]
g load = 4.9
Knowing that normally the stall speed is published for gross weight, I wondered if 4.9g would overload the wing at 1800lbs. The wing is designed for 6g at the aerobatic weight of 1600lbs.
1600lbs x 6g = 9600lbs
so, 1800lbs x 4.9g = 8820lbs
Yes, the wing can withstand 4.9G at 1800lbs. Those numbers are close enough to me to assume Van's published manouvering speed is for the applicable G limit at 1800lbs, with a safety buffer.
So, what is the manouvering speed at 6g and the aerobatic weight of 1600lbs? We all know that weight affects stall speed, and a few mph will make a big difference at 6g. So we'll decrease the stall speed to 60mph at the 1600lb weight. (I used the formula: new stall speed = old stall speed X sqrt[new weight / old weight])
Va = 60 x sqrt[6]
Va = 147mph
Cool. But it is safer to use the published 142mph as a safety buffer.
