i'm having troubles with airspeed indicator. it reads at cruise 160 mph. when i go to full power it really doesn't read higher. gps ground speed does increase. i've changed the gauge to a new one but same results. checked the pitot tube for clogs or leaks working fine. the plane has a static port in the fusealge seems to be ok. any idea's?
Have you had a pitot static test done to standards by an FAA licensed test facility?
I bet you have a leak somehere.
A good way to do a self test on the pitot system is to take about 18" of 1/4" inside diameter flexible tube like Tygon. Attach one end to your pitot tube and sinch it tight with a tie wrap. Take a pair of vise grip pliers and clamp them on the other end of the tube to pinch it off sealling it. Now gently roll the vise grip coiling up the tube which will apply pressure to the pitot system. Coil it up enough to read about 250 mph on your airspeed indicator. Hold it there and don't move the tube coil so as to not change that pressure. The airspeed indicator should be able to hold that speed without it bleeding off speed.
It's safer to have someone else looking at the indicator if you can't see it while coiling the tube. It doesn't take to much pressure to make it indicate. This is why you do it by coiling the tube.
Of coarse if you aren't using the Vans pitot tube, which is 1/4" outside diameter stainless tubing, then this method won't work!
I'd be willing to bet you have a leak and the speed will bleed down.
When I had the airworthiness inspection for my plane my local FSDO, who was doing the inspection, requested a full pitot static test with a log book sign off. This test was pretty expensive and I felt a bit overkill. It was worth it after I watched the technician test alttitude, encoder and airspeed indicator for accuracy.
If you read the regs it is actually required any time the pitot static system is opened up. So technically you need it for a new system.
air speed indicator
Linear Mode
