The International Cessna^® 170 Association

Hello all. I’ve been busy getting my newly purchased 170A airworthy again. One issue we noticed is the ASI reads about 10MPH. Both the mechanic and I thought this was “just another item we needed to fix/address”. ...but then I saw another 170 ASI with the needle pointing in the EXACT same location/speed…which got me wondering. Is this normal? Does the ASI on the 170 normally read “10”?

Any direction on this would be helpful and appreciated.

Mine old AS indicator sitting on the shelf seems to indicate about 8MPH. I like mine better it does not have a red line!!!!!!

What color is your airplane, Jack?

Thanks John. When the ASI was installed and working normally, did it read 8 (or so) MPH on the ground?

What about other owners. Does anyone have what they would say is a normal, working ASI, but indicates 8-to-10 MPH on the ground?

White and maroon Ryan!
(with the question being asked...I somehow feel like I'm being setup for a joke)

Jack,
I have to admit I have no idea what the AS indicator displayed at rest while it was installed in the airplane, it must have been unremarkable (8 - 10 MPH) or my annul retentiveness would have kick in.

Pretty airplane!

Thanks for the help John. My daughter (a pilot also) and I both can't wait to get the airplane flying again. We're about two weeks out at this point (which means another four weeks). Small stuff at this point; oil leak from the generator, this ASI indication issue and a few other small issues.

jackh wrote:White and maroon Ryan!
(with the question being asked...I somehow feel like I'm being setup for a joke)

That answers the question.

There is a long standing joke on here about red vs. green airplanes with each side being convinced that their airplane is the "faster" color. Being in the red camp, it pleases me to see that your airplane is fast sitting still.

Beautiful airplane!!

Go team RED!

Yeah and the Red ones Airspeed indicators read 10mph standing still and the Green ones read 0mph standing still!!!!!

jackh wrote:Thanks for the help John. My daughter (a pilot also) and I both can't wait to get the airplane flying again. We're about two weeks out at this point (which means another four weeks). Small stuff at this point; oil leak from the generator, this ASI indication issue and a few other small issues.

Jack have you read the strings here about leaking generators? The two big generator leak culprits are the shaft seal being installed backward and the requirement to replace the entire to accessory case to Generator/tach drive gasket as there is a hole in the accessory case between the Generator and the tach drive that can only be sealed properly by replacing the entire generator/tach drive gasket.

Hey John. I'll search the threads right now. I just thought the oil leak on the generator was somewhat "normal" (my Cirrus had a oil leak on the alternator last month). The generator looks to be having issues itself, and so I plan to order a overhauled-unit from Aerotech this morning.

There is a possibility that at some time in the past the A/C ASI had a stoppage because of an insect lodging in the Pitot tube.


Technician would blow out with compressed "shop Air" Put air to the wrong end and you warp the ASI. Very common. Very Very.


Years ago my A/c was signed off "read to Fly' and when I went to airport to fly it . It was indicating 40 knots indicated air speed and still tied down.

Your ASI may still work correctly. Check it out at rotation , don;\'t like, abort. You really want to feel secure about indicated AS at landing !! If it does not work at landing you are forced to use your sensory feelings, carry a little RPM.
Think it out before you launch!

The answer to your original question is "No"... it's not correct, in the strictest sense.
It appears your 9 (and the other also) airspeed indicators have suffered from "hysteresis" which is a stretched condition of the aneroid capsule/diaphragm in the unit. You could have the unit overhauled or exchanged with a reputable instrument shop. The instrument should read "zero" at rest.
Of course, the most important factor is if the instrument reads correctly at flying speeds, and the shop can confirm or fix yours to do that.

All you need to test your air speed indicator is a water manometer made with some clear vinyl tubing and a yard stick.