Altimeter issue

This took me by surprise!

During the latter stage of a 1 hour flight, the pointer indicating 100s of ft suddenly fluctuated wildly and then settled back on the correct altitude.

Correct indication on ground with local QNH set.

Any ideas??

You were flying a drifter in turbulence?

Swamp gas from a weather balloon, trapped in a thermal pocket and refracted by the light from Venus?

I didnt think there was any such thing as a stupid question!

Whilst i appreciate the humour conveyed in the last responses, I thought that someone who had the same issue may be able to shed some light on why this happened.

No further posts from me!

Possible water in static line??

Did you wash the plane recently? Any of the other static air instruments have an issue (VSI ASI??) Thermals can cause it as well I guess so could a side slip if it introduced turbulent air into the static port? Did you just open a window? Crack or water in the static line?

Possible water in static line??

Clear

If your panel is not rubber mounted you might have got a harmonic vibration from the engine/prop. Such things will play havoc with instrument life. Your altimeter mechanism multiplies a very small movement to something you can detect on a pointer. Nev

Possible water in static line??

checked and clear thanks

If your panel is not rubber mounted you might have got a harmonic vibration from the engine/prop. Such things will play havoc with instrument life. Your altimeter mechanism multiplies a very small movement to something you can detect on a pointer. Nev

Thanks Nev, this was a sudden and erratic dial pointer movement lasting about 30 seconds which has never happened before.

First thought that the pointers may have rubbed together. Flight conditions was light chop on descent when it occurred.