- Jul 22, 2021
Hello. I have a small ultralight and in flight, VSI shows 1700-2000ft/min descend. I took the instruments off, one by one and tested on a vacuum system. ASI has no leaks, in fact is the only one working properly, VSI works normal: increase the vacuum, it climbs, decrease it, it descends. Altimeter has leaks, so it is not good. I blocked the altimeter line and I am using GPS altitude for now. Still in flight, actually once the ASI starts to increase, VSI starts to show descent. Other than buying a new one and retrying, don’t know what else. Don’t understand why the ASI is working normal. I checked it with the gps over the field at low altitude where the wind doesn’t shift or varies much from ground and it shows ok.