The place for technical discussions about GA and flying.
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By foxmoth
#1768950
Doing some formation the other day (ok, some time ago, before lockdown) and asked lead to start a loop at 140kts, as he was going through 160 asked him to ease out the dive - he reported not yet having reached 140 but felt faster, ASI seemed to be reading OK at 90-100 but in error above 120 or so. Ground tested OK to within 3 kts - thoughts?
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By Flyin'Dutch'
#1768969
Static leak/blockage?
By riverrock
#1768988
So it's going to be pitot pressure too low ( a leak of some sort), static too high (increasing pressure with speed, so getting reading from wrong place or again a leak) or a gauge issue.
Should be able to get to the bottom of it with the right calibrated kit.
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By Flyin'Dutch'
#1769062
foxmoth wrote:Thanks, but checked both pitot and static for leaks.


Has the 'thang' itself been checked and calibrated recently. How about the other machina?
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By foxmoth
#1769397
All ok with the check machine, may have suspected the other aircraft if the pilot in this one had not been wondering a) why it was taking so long to accelerate, and b) why the aircraft felt like it was a LOT faster than indicated.
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By Rob L
#1769595
RichJordan wrote:I've got the opposite problem, ASIs all over read by approx 10%. Keep meaning to blow static line through.

If you do, disconnect all instruments first! :D

To be fair, for a PtF type, any CAA approved shop will undertake a pitot/static check for you for a few hundred quid; good assurance of your instruments, in my opinion. (It's part of the Annual for EASA-CAA-types).
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By Rob L
#1769596
Rob L wrote:
RichJordan wrote:I've got the opposite problem, ASIs all over read by approx 10%. Keep meaning to blow static line through.

If you do, disconnect all instruments first! :D

To be fair, for a PtF type, any CAA approved shop will undertake a pitot/static check for you for a few hundred quid; good assurance of your instruments, in my opinion..and you'll get an approval for the airframe logbook. (It's a standard part of the Annual for EASA-types, of course).
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By Charliesixtysix
#1772537
foxmoth wrote:Doing some formation the other day (ok, some time ago, before lockdown) and asked lead to start a loop at 140kts, as he was going through 160 asked him to ease out the dive - he reported not yet having reached 140 but felt faster, ASI seemed to be reading OK at 90-100 but in error above 120 or so. Ground tested OK to within 3 kts - thoughts?



Problem resolved?
If so, what was the cause of the discrepancy ?
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By foxmoth
#1772918
Looks like position error - the pitot had moved down possibly due to a missing bolt, doing the permit renewal flight I also found we had a higher than expected stall speed so over reading at the low end.