Bernie RV7
Member
I believe my ASI is over reading by about 8kt, is this model able to be recalibrated or do I get another one.
Cheers Bernie
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Can this RV-6 ASI be recalibrated ?
- Thread starter Bernie RV7
- Start date
I believe my ASI is over reading by about 8kt, is this model able to be recalibrated or do I get another one.
Cheers Bernie
Are you sure it's the ASI? A static leak will cause just about that amount of error in that direction in many people's experience.
Bernie RV7
Member
Thanks Paul
I was assuming that the static system was ok because the discrepancy is between my new Gemini AP airspeed and my original ASI and both use the same static system.... but I will check the static system out for leaks before I do anything else.
Cheers
I was assuming that the static system was ok because the discrepancy is between my new Gemini AP airspeed and my original ASI and both use the same static system.... but I will check the static system out for leaks before I do anything else.
Cheers
Mark Albery
Well Known Member
The easiest way to check ASI calibration is to make a water manometer connected to the pitot head.
A suitable long length of poly tubing that's a tight fit on the pitot should work.
There are several online descriptions and tables for converting head of water to airspeed such as this.
If it's a heated pitot, you may have to break into the line to connect up your manometer.
It will also detect a leak in the pitot system if you see the airspeed slowly decaying.
A suitable long length of poly tubing that's a tight fit on the pitot should work.
There are several online descriptions and tables for converting head of water to airspeed such as this.
If it's a heated pitot, you may have to break into the line to connect up your manometer.
It will also detect a leak in the pitot system if you see the airspeed slowly decaying.
catmandu
Well Known Member
Yes, it can.
Someone I may or may not resemble might have let one like that slip off the wing during a recent EFIS screen size upgrade. After getting back into the E6B books and with the help of a couple apps airborne, I confirmed the TAS of the EFIS was correct, the IAS on the EFIS matched the IAS on my Gemini AP, so I concluded the ASI (which is now a backup to a backup) was reading incorrectly.
Decided to experiment, opened it up and quickly figured out there is a toothed cam driven by pressure change that rotates a gear attached to the needle on the face display. Said cam was barely engaging said gear, and obviously could have jumped a tooth or two with a sudden deceleration. Made an educated guess as to how many teeth to move the cam on the gear, bent it ever so slightly into a better engagement position and did a test flight.
I guessed well, ASI IAS was +\- 2 kts compared to the EFIS IAS, good enough for backup for me. Sorry, did not take pictures, hope the description helps.
Someone I may or may not resemble might have let one like that slip off the wing during a recent EFIS screen size upgrade. After getting back into the E6B books and with the help of a couple apps airborne, I confirmed the TAS of the EFIS was correct, the IAS on the EFIS matched the IAS on my Gemini AP, so I concluded the ASI (which is now a backup to a backup) was reading incorrectly.
Decided to experiment, opened it up and quickly figured out there is a toothed cam driven by pressure change that rotates a gear attached to the needle on the face display. Said cam was barely engaging said gear, and obviously could have jumped a tooth or two with a sudden deceleration. Made an educated guess as to how many teeth to move the cam on the gear, bent it ever so slightly into a better engagement position and did a test flight.
I guessed well, ASI IAS was +\- 2 kts compared to the EFIS IAS, good enough for backup for me. Sorry, did not take pictures, hope the description helps.
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