Phugoid?

[hevansrv7a]

As I understand it, you are experiencing a phugoid when the airplane continues to speed up and slow down on its own. Here's how I "discovered" it.

In level flight, trimmed for level flight, twist the trim knob a bit - 90 degress for example. The airplane should pitch up or down and the speed should change accordingly if the power is not adjusted. When I do this, the rate of sink/climb cycles up and down with no obvious trend toward becoming steady. It goes in the right direction, but not steadily.

Does this happen to you? If so, what model? Do you have an explanation or a "fix"?

I should mention that I adjusted my HS angle of incidence to be slightly nose-up from Van's plans. I checked first with the factory to get assurance that it would not make the plane dangerous. The desired effect, which I got, was to reduce trim drag by reducing the need for off-neutral trim tab. The airplane climbs at 110 kts with zero trim tab deflection and then levels off up to around 130 KIAS still without deflection. I don't know if the airplane is doing its phugoid as a result of the change or would have done it before.

[scsmith]

What you describe is completely normal. I don't think your tail incidence change could have any bearing on phugoid damping. A fixed pitch prop will add slightly more phugoid damping I think, compared to C/S.