Can TAS at different altitudes be calculated if only one performance point is given?

If the POH only gives TAS at only one altitude, can we calculate the TAS at other altitudes?

Here is a snippet from the POH of Remos GX. If we set the RPM to 5,200 then at 3,000 feet MSL ISA we get 107 knots. Can we calculate the TAS at 6,000 feet?

• No, you can't. You sit on a quadratic function (actually, a sum of several) and don't know how far you are from the optimum, so you don't know the local gradient (which changes all the time as you move up or down the curve, of course). May 19 '20 at 17:55