Dan Kent Posted October 3, 2014 Report Share Posted October 3, 2014 I posted in the calibrated airspeed revisited forum that I suspected my IAS was low, causing low TAS. I came to this conclusion by comparing ground speed VS TAS for multiple 180 degree runs. I took my plane to the local avionics shop yesterday morning for a pitot test. They said I did have a leak, and after trouble shooting for an hour and a half they concluded that I had 2 leaks and they were only able to fix one as one was between the pitot and the fuselage. After my plane was back in my hangar I looked up the pitot system in the maintenance manual and learned how to remove the pitot, so I called the distributor to discuss. My plan was to remove the pitot this morning to check the connections there. On my way to the airport I had an inspiration and below are some pictures of what I did. The balloon is an 11" latex purchases in a pack of 15 from Kroger. When I took the photo, it had be on the pitot for about 15 minutes, so I'm pretty sure the system is tight. Initially the airspeed was around 115 kts, but dropped a couple over the 15 minutes. Link to comment Share on other sites More sharing options...
FlyingMonkey Posted October 3, 2014 Report Share Posted October 3, 2014 If it takes 15min to show a loss, I'm not sure you'd see an error in flight as the system is continuously pressurized by incoming air. Obviously stopping leaks is good, but this must be a *tiny* leak. You might even lose some air through the skin of the balloon...that does happen over time. Link to comment Share on other sites More sharing options...
Anticept Posted October 3, 2014 Report Share Posted October 3, 2014 The connectors can leak in the wing root (you have to pull the wing). Check those and the pitot connection before continuing. The pitot line from the tube can sometimes be pulled out. Disconnect it from the tube, tie string and tape it to make sure it doesn't pull off. Go to the wing root, and pull. Also, the balloon was a clever idea, but did you clamp it to make sure the balloon isn't leaking? I know you said the shop said there is a leak, I am just making a recommendation. For the future Link to comment Share on other sites More sharing options...
Tom Baker Posted October 3, 2014 Report Share Posted October 3, 2014 Corey, he is not flying a CT, so the fittings in the wing root may not be an issue. Link to comment Share on other sites More sharing options...
GravityKnight Posted October 3, 2014 Report Share Posted October 3, 2014 good idea Link to comment Share on other sites More sharing options...
Dan Kent Posted October 3, 2014 Author Report Share Posted October 3, 2014 This was after the repair, although the shop thought there was still a leak between the pitot and fuselage. I tried this before I tried to disassemble the pitot, so I was very pleases when it held pressure. Of course the pitot could still be misaligned. I did not clamp the balloon, but it was quite a tight fit and I had pulled it quite far onto the pitot. The specs in my maintenance manual was @ 120 kts, no more drop than 3 kts in 3 minutes. Link to comment Share on other sites More sharing options...
S3flyer Posted October 3, 2014 Report Share Posted October 3, 2014 Clever! Link to comment Share on other sites More sharing options...
Dan Kent Posted October 3, 2014 Author Report Share Posted October 3, 2014 Clever! I have 14 more certified and calibrated pitot system testers that I thought I would list on eBay for $29.95 each :-). Link to comment Share on other sites More sharing options...
Anticept Posted October 3, 2014 Report Share Posted October 3, 2014 Corey, he is not flying a CT, so the fittings in the wing root may not be an issue. That's what I get for using the mobile browser on iphone! I couldn't tell! Link to comment Share on other sites More sharing options...
FastEddieB Posted October 3, 2014 Report Share Posted October 3, 2014 I have 14 more certified and calibrated pitot system testers that I thought I would list on eBay for $29.95 each :-). Cool! Do they come inflated? Link to comment Share on other sites More sharing options...
Anticept Posted October 3, 2014 Report Share Posted October 3, 2014 Cool! Do they come inflated? You are full of hot air, what do you need already inflated testers for? Link to comment Share on other sites More sharing options...
Rich Posted October 4, 2014 Report Share Posted October 4, 2014 Nice idea Dan. Thanks for posting Link to comment Share on other sites More sharing options...
Dan Kent Posted October 15, 2014 Author Report Share Posted October 15, 2014 I have been unable to fly for 10 weeks as I ruptured my achilles playing tennis, and had the repair surgery 10 weeks ago today. I was able to go flying this morning and got to do a little testing on my repaired pitot system. It seems much more accurate, but may still be 4-5 kts off at WOT (I'll have to do more testing). At lower speeds it seemed to track much closer to GS on an almost windless day. Sure was nice to get back in the air, on a beautiful day. Link to comment Share on other sites More sharing options...
Jim Meade Posted October 16, 2014 Report Share Posted October 16, 2014 Glad you're feeling better and hope you heal completely. Keep us posted as you develop more conclusions on your pitot system. Link to comment Share on other sites More sharing options...
Dan Kent Posted October 16, 2014 Author Report Share Posted October 16, 2014 Thanks Jim. I went out again this morning and did 2 lower RPM 180 degree runs, 4000 and 4200 rpm. On one it was 6.5 kts low and the other 5.5 kts. What's interesting (at least to me) is my Dynon SV system is about 3 kts slower that the analog airspeed indicator. The 6.5 and the 5.5 were between average GS and the Dynon. DA was 4000'. So the error VS the analog gauge was 3.5 and 2.5 kts. About as good as I'm going to get it, I suspect. Link to comment Share on other sites More sharing options...
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