I was successful in fixing the indicated airspeed problem. It was indeed a static leak at the back of the gauge. The static line was barely holding together. I cut out the bad end, put a new brass ferrule on, then re-installed the compression fitting in the back of the gauge. The clear plastic static line from the altimiter was not hooked to the system, so I cut the metal line again and re-connected it with compression fittings to a brass "T" with a barb fitting. I could see an immediate difference on takeoff, and I compared the instruments with the GPS readout. I set up and did some power on and off stalls, and it went into a classic Ercoupe mush right down at 40 MPH instead of 64. I was able to fly final at 80 MPH without falling out of the sky and touched down at 60 MPH.
I called and cancelled the new ASI I ordered. THanks for all the good info and advice. Best, Dave --- In [email protected], "bigbrownpi...@..." <bigbrownpi...@...> wrote: > > Oops, calculation error. I meant to change units in the GPS from Knots to > MPH, but forgot. After converting the GPS Knots, I'm indicating 15 MPH > faster than actual at 75 MPH indicated, ane 16 MPH faster at 100 MPH > indicated. Still needs to be fixed and this is more in line with what I'm > observing when doing stalls and approaches. > > Dave > > > --- In [email protected], "bigbrownpilot@" <bigbrownpilot@> wrote: > > > > Got home from my UPS trip this morning and went up this afternoon to see > > how much my indicated airspeed was in error. First, I checked the pitot > > tube-- it was 3 1/4" from the lower surface of the wing, so I adjusted it > > gently to 3 7/8". It is not parallel to the lower surface of the wing, but > > canted slightly down after the adjustment. Next, I checked the pitot and > > static lines at the left wing joint. There is clear plastic tubing joining > > both lines secured with safety wire wrapped around the ends. I could not > > really access the tubing to check it, but it appears to be fairly new and > > in good condition. There is also a metal line coming from the center > > section that is no longer connected to anything and it is open on the end. > > After that, I went up and flew South, East and West at 75 MPH indicated and > > 100 MPH indicated and logged the groundspeeds I saw on the GPS for each > > leg. After feeding them into the web-based program linked from Ed's Coupe > > Site, I got a +23 MPH error at 75 MPH indicated and +27 MPH error at 100 > > MPH indicated. I ordered a new UMA airspeed indicator from Aircraft Spruce > > with proper range markings when I got home. Hope that fixes it! > > > > Later, > > Dave > > >
