Airspeed Indicator Issues
Posted: Fri Sep 07, 2018 1:53 pm
Had a rough annual this year and still feeling the effects from it. Had to replace a cylinder, which I doubt added a lot of horsepower AND a STOL kit. I'm now taking off and climbing at 1000 fpm while indicating ~60 mph.
The 91.411 and 91.413 tests were due this year at annual time, so I had the avionics guy do them. He noted that there were several leaks in the pitot/static system that had to be fixed. First flight after the annual the airspeed indicator was barely off the peg when I raised the tail. I rotated barely indicating 40 mph. My AOA was showing a full green donut as it usually does and 1349D was climbing normally. At 2400-2500 rpm level at 3000’ I was only showing ~90 mph when I’m usually closer to 110 mph.
Had the avionics guy take a look at it. He checked the angle of the pitot tube against the template. Said the angle was off a small amount. I still got the same results, about 20 mph low regardless of attitude and phase of flight.
Then at the beginning of August on takeoff the indicator face filled with moisture and the needle never came off the peg. After giving it a tap it stuck at just above 60. Had the indicator removed, avionics guy said there was evidence of a puddle of water at the bottom of the indicator. It was repaired, reinstalled, and flown a couple days ago. A sump bottle was also added. Same result, about 20 mph low.
I attached a picture from the flight. Calm winds were reported at the field, windsock agreed. Winds aloft forecast was interpolated for 3 kts of wind at 3000’.
The previous Part 91 tests 4 years ago were completed without issue, no leaks reported. The aircraft is hangered in Central Virginia. Prior to the annual it hadn’t been flown in visible moisture for a long time, quite possibly over a year even two. I couldn’t remember. In July, a month after the annual, it did sit outside for a couple days where a shower may have passed by. I don’t know how that much moisture could’ve been introduced into the system.
Does the brain trust know of any intricacies of the 1951 170A pitot/static system? What questions and troubleshooting should I be asking and doing at this point? Planning on taking it to the shop that did the previous tests 4 years ago. Potentially another if they’re booked up.
The 91.411 and 91.413 tests were due this year at annual time, so I had the avionics guy do them. He noted that there were several leaks in the pitot/static system that had to be fixed. First flight after the annual the airspeed indicator was barely off the peg when I raised the tail. I rotated barely indicating 40 mph. My AOA was showing a full green donut as it usually does and 1349D was climbing normally. At 2400-2500 rpm level at 3000’ I was only showing ~90 mph when I’m usually closer to 110 mph.
Had the avionics guy take a look at it. He checked the angle of the pitot tube against the template. Said the angle was off a small amount. I still got the same results, about 20 mph low regardless of attitude and phase of flight.
Then at the beginning of August on takeoff the indicator face filled with moisture and the needle never came off the peg. After giving it a tap it stuck at just above 60. Had the indicator removed, avionics guy said there was evidence of a puddle of water at the bottom of the indicator. It was repaired, reinstalled, and flown a couple days ago. A sump bottle was also added. Same result, about 20 mph low.
I attached a picture from the flight. Calm winds were reported at the field, windsock agreed. Winds aloft forecast was interpolated for 3 kts of wind at 3000’.
The previous Part 91 tests 4 years ago were completed without issue, no leaks reported. The aircraft is hangered in Central Virginia. Prior to the annual it hadn’t been flown in visible moisture for a long time, quite possibly over a year even two. I couldn’t remember. In July, a month after the annual, it did sit outside for a couple days where a shower may have passed by. I don’t know how that much moisture could’ve been introduced into the system.
Does the brain trust know of any intricacies of the 1951 170A pitot/static system? What questions and troubleshooting should I be asking and doing at this point? Planning on taking it to the shop that did the previous tests 4 years ago. Potentially another if they’re booked up.