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I have a drifter with an airspeed indicator to 100 knots, I know the drifter will get no way near that in one piece so would an 80 knot indicator be better as you are using more of the indicator in the instrument.

 

 

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I have a drifter with an airspeed indicator to 100 knots, I know the drifter will get no way near that in one piece so would an 80 knot indicator be better as you are using more of the indicator in the instrument.

In general:

 

All Air Speed Indicators (ASI) have an error factor that can usually be found in the Pilots Operatoing Handbook (POH). It is common for the ASI to under read at slow speed, move up to be reasonably accurate in the vicinity of your cruise and over read at your high speed cruise. Other factors like aircraft attitude (climb out) may also effect accuracy of readings.

 

The larger the instrument scale/face (small faced instruments are notoriously inaccurate - indicators only) and

 

The larger the increments the more accurate the instrument. ( I may have expressed this badly - if the scale is spread over 50 knots it is likely that the instrument is more accurate in this range, than one that is up to 200 knots etc etc).

 

Most instruments are calibrated to be at their most accurate in their mid range. (So if your aircraft cruises at 70 knots, an ASI that measures up to 80-100 knots should give you a reasonable level of repeatability)

 

 

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  • 4 weeks later...
I have a drifter with an airspeed indicator to 100 knots, I know the drifter will get no way near that in one piece so would an 80 knot indicator be better as you are using more of the indicator in the instrument.

Hi Yen, mate I'm pretty sure I have a 80 knot asi here in the hangar somewhere if you're looking for one. Cheers Davo

 

 

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Hi Yen, mate I'm pretty sure I have a 80 knot asi here in the hangar somewhere if you're looking for one. Cheers Davo

If Yen doesn't need it, I'm in the market for one Dave. P.M. me please.

FWIW, latest state of my Thruster panel

 

1141301317_DSCF5032(Copy).JPG.dad2e07b0e96b7afb3ffe5ed29b7e36b.JPG

 

 

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  • 3 months later...

Sorry fellows, I’ve been out of action on and off for a while. I did have a look around and found it, but it’s not 80kts it’s 100kts, sorry for a bum steer

 

 

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