[cguarino]

I have a question for you aero majors out there. If I have a known data point for a RV-4, like gross weight, 65 degrees, SL, no wind takeoff distance. Can I extrapolate the required takeoff distance for different temps and headwinds/tailwinds? Are there formulas for this or is the only way to get this data is through flight test? I don't think I can just add or subtract 17% for each 10 knots of tailwind/headwind. I'm guessing it is more complicated than that. Also, how about temp changes? The point of all this is that I have a runway with a perfered takeoff direction. I can use it in both directions but much rather taking off toward an open field vs obstructions. I want to be able to figure out how much tailwind I can accept before I need to use the opposite direction. Also, how does this apply to landing distances and 50 ft obstacle distances. I understand that turf vs asphalt will be different. I will only compare apples and apples. Thanks.

 

[n5lp]

I have a question for you aero majors out there. If I have a known data point for a RV-4, like gross weight, 65 degrees, SL, no wind takeoff distance. Can I extrapolate the required takeoff distance for different temps and headwinds/tailwinds? Are there formulas for this or is the only way to get this data is through flight test? ...

The Koch Chart is the basic place to start.

This one came from http://www.wind-drifter.com/technical/KochChart.gif

 

[John Clark]

A few more things to consider

Larry is right, the Koch chart is the place to start as density altitude will be the biggest factor. Here are a couple of more considerations. First, tailwinds. Rule of thumb, a 5 knot tailwind (tailwind component, not 5 knots of wind) on takeoff will add 25% to the takeoff roll. 10 knots will add 55%. Remember too, the tailwind will reduce the effective climb angle. The next consideration is runway slope. a 2% up slope will add 15% to the takeoff roll and a 2% downslope will decrease the roll by 10%.

John Clark ATP, CFI
RV8 N18U "Sunshine"
KSBA