Anyone ever have an ASI read high?

455 Bravo Uniform

455 Bravo Uniform

Final Approach
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455 Bravo Uniform
If so, what can cause it?

I flew a few T&Gs this afternoon and had trouble keeping my approach speed down, coming in "hot" or so I thought. But not floating. And the stall horn was sounding earlier than usual. And controls were getting soft as they normally do. It visually and sound wise sure seemed like I was on speed.

Going to get it looked at Monday. Just figured ASIs would read low or zero, never high.
 
ASI can read high on takeoff in helos, in airplanes, never flown one that reads high.
 
A partial blockage in the pitot line would make it read high when slowing down, and low when speeding up.
 
I learned yesterday: to use ALL my cues and clues and don't overly focus on the ASI to be correct. Could have been bad.

-Visual (how fast things are going by)
-MP (or rpm) same as always?
-Sound of engine
-wind noise
-stall warning (duh)
-rate of descent (visual, not VSI; -am I where I usually am in the pattern)

Basically- if I'm having trouble keeping my speed up or down, and I normally don't, something else must be wrong...everything about my pattern work was jacked up...major clue. Normally I'm 70kts in the pattern, flaps 20, and 60 on final. In my normal landing configuration, I was 80kts turning final, so I went around. Next 3 approaches were ugly but landings were fine.
 
I had one that would read a higher speed as I descended. And read slower as I climbed. The copilot side ASI was just fine.
 
Capt. Geoffrey Thorpe said:
A leak in the static system under the panel can give you a few knots.
Click to expand...

Our pitot/static guy says the proper static leak check is one of the most inappropriately overlooked things on light aircraft and tons that he checks properly show massive leaks that years or signed off checks never caught. He found one in our aircraft and looking at the quality of work where it was leaking, there's NO way it'd ever been right. No tape on the connection to the condensation bottle on one end. It had to be leaking from day one after it was installed. It also had warped in heat which made it worse.

I've become a believer. Make your pitot static test person give you a written report that shows exactly what they checked and what all the numbers were.

Our guy easily does this with a spreadsheet on his laptop and a cheap portable printer, and it has a lot more data about how the system is performing than just a "good to go" sign off we got from the former mobile pitot static guy.

He also prints off all of the tech data from his "built sometime this millennium" transponder test gear.

The old guy with his 70's test gear retired and that's what drove us to find this guy via a referral and his gear and amount of things checked is easily five times what we used to get out of the old guy.
 
Whatever makes you comfortable. Did you supervise the entire job? He can put whatever he wants in the spreadsheet. Teflon tape goes on pipe threads. I've seen them installed without it and not leak. And, there's no way to know that years of signed off checks missed leaks.
 
GlennAB1 said:
Whatever makes you comfortable. Did you supervise the entire job? He can put whatever he wants in the spreadsheet. Teflon tape goes on pipe threads. I've seen them installed without it and not leak. And, there's no way to know that years of signed off checks missed leaks.
Click to expand...

Yes, I did. It's nice when folks come to your hangar. And yes, I saw the botched job the previous mechanic did on the plastic condensation bottle myself. It's not a tapered thread, it must have tape or it absolutely will leak. So yes, it is possible to know it was done flat wrong.

Looked like the last person to touch it couldn't reach the top properly, so they half-assed it.

And yes, since I was watching the work, guess when the leak quit?

And guess what the log entry said from the previous guy for years? "No leaks." Utter BS.

No, I never watched the other guy. My recent job changes mean I'm usually more available on weekdays than my co-owner so I get to watch all this stuff now.

But thanks for your unfounded skepticism.
 
I've had guys ask what my landing speeds are. I don't know that I've ever looked at my airspeed instrument after turning final. It wouldn't matter what it says so there's no reason to look.
 
Well it took 3 weeks and my appointment date came today (I need to switch jobs and help all these overloaded A&Ps).

Avionics guy was super nice and logical and methodical in his troubleshooting.

He immediately noted a static leak with his test equipment. Found the pilot side static condensate bottle to be fully cracked on one threaded end.

Next check showed there to be another leak. Found the fitting on the altitude encoder loose and he tightened the two fitting screws. He also replaced a jury-rigged too short rubber hose to the encoder with a hard plastic line with ferrules and the threaded connector.

He then found something goofy that looked like it intermittently released pressure/vacuum on his test equipment and diagnosed it to the alternate static switch.

Once that was fixed, there was very minor leakage and he tightened everything else up and we were good to go.

The last thing to check was the ASI itself (an internal leak in the ASI would have necessitated that it be shipped off to Michigan for repair and mo money). ASI checked out to be dead nuts accurate.

He replaced a few stripped out screws in the dash and pulled out a couple extraneous hoses that didn't go anywhere.

All told, less than 3 hours to take stuff apart, diagnose/test, fix, and put it back together, including answering my dumb questions. Knowing what I learned now, I am confident of the repairs, but also more knowledgeable of what can go wrong and why.
 
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