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**Pearson** · 10-22-2011, 18:52

Re: Airspeed indicater reads too high

Don,

That is one pretty airplane. Of course I am partial because mine looks almost the same. It is only few numbers away from yours, N43381.

I am not a licensed mechanic, but I have would reserve bending the pitot tube to only on my mother in law's airplane. My suggestion is to have your tach checked for proper RPM. Also check your fuel burn for your engine. If you have a stock A65 and you are burning more than 4.5 gallons per hour, I would bet your tach is indicating low. That would cause you to have to add more power to bring it up to a normal RPM, which would mean your actual RPM is higher and obviously make your airspeed higher.

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**magman** · 10-22-2011, 19:04

Re: Airspeed indicater reads too high

I'll second Pearson's comment.

Tach errors always seem to to be ones that read LOW.

So you push the throttle up to get your desired RPM.

Now you are at higher than desired power & the ASI is reading HIGH.

Why not check the tach with a tester?

There are quite a few around.

Is your Static RPM in Limits per TCDS?

**M Towsley** · 10-22-2011, 20:41

Re: Airspeed indicater reads too high

It would be easy to buy an electronic tach used for modeling and see how it reads on the ground and in-flight. My ASI reads high, too. And I know my tach reads low so I compensate for that.

A trick I read about was putting an o-ring on the static tube and move it back and forth until it reads correctly. The only problem is the static line is buried in the wing of the Taylorcraft. Mine is plugged somewhere so I my static is right under the glare shield, I will have to investigate that another day. Perhaps your static line really isn't reading from the wing and it is still reading somewhere in the cabin. I found in one of my T-Crafts, (please, not a T-Cart), that when you opened the window the reading would change as opposed to when the window was closed or partially closed. If you have a window that opens try that to see if the ASI changes. Then you may discover your static line reading from cabin air.

And, welcome! Pretty plane.

**cvavon** · 10-22-2011, 21:55

Re: Airspeed indicater reads too high

First off what are you using for a comparison to come up with the 11 mph a GPS if so leave your tack alone and talk to instrument repair shop about how to calibrate it. and welcome to the tribe nice bird . looked at the photo of your panel and my plane shows about the same speed and rpm at cruse 2200 to 2250 about 100 mph with 74/43 prop and bush wheels and that is same as GPS on top of panel

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**cvavon** · 10-22-2011, 22:11

Re: Airspeed indicater reads too high

Oh i see your gps is it set to read in mph or knots . Knots would be about 11 mph different at the speed on your photo

**flyguy** · 10-22-2011, 23:11

Re: Airspeed indicater reads too high

Throws me a little that you have the same error at the bottom end, are you sure about that? I have owned 3 BC12D's. They were all off (high) about the same amount at the top end, but the lower speeds were off very little, if any.

The one I had originally on my present plane was off about 8 or 10 high at the top end when I replaced it. The new one has about the same error on the top end, that is about 8 MPH. At the bottom end it is right on the money according to my GPS. I blame it on the static source in the wing as I suspect at higher speeds there is a greater vacuum in the wing caused by the large trailing holes at the aileron actuators. What is the uncorrected stall speed you get on your indicator?

It sounds as if you have the same problem of the same magnitude as all three of my planes, but you say that it doesn't change if you pull the static line off. From your photo of RPM vs Airspeed I think your airspeed indicator and your tachometer are OK. The readings are almost Identical to mine. I'll bet it is the static pressure.

I can't imagine that the static pressure in the cabin and the wing is the same. Strange. I haven't tried disconnecting the static line.

I have been tempted to get the neat little 2 tube ram/static assembly and just tape it on the jury strut and run temporary lines out the window for some tests, I just haven't got around to it yet.
DC

**Ray36048** · 10-23-2011, 04:12

Re: Airspeed indicater reads too high

The fact nothing changed when you pulled the static line is the clue. You have a broken static line in the cabin area. The cabin is a low pressure area and without a static to the outside, the airspeed will read high and the altimeter will also read high.

**flyguy** · 10-23-2011, 17:28

Re: Airspeed indicater reads too high

Good point Ray. How about this--doesn't require going under panel to confirm. Set altimeter to field altitude on ground, but right on a marker. Make a very low pass at normal flight speed, say 10 or 20 off deck. What does altimeter read?

Would that work to confirm area of problem before diving in under the panel?

I just always blamed the problem on what I considered a poor choice for locating the factory static "port." The guy who owned the plane before me (AI) had put a static port on the left side of the fuselage between the cowl and the door. I hooked it up once. Don't remember the exact results, but it wasn't good, Chuckle.

DC

**TreeTopFlier** · 10-23-2011, 17:44

Re: Airspeed indicater reads too high

WOW....Thanks to all that responded....... I normally cruise @ 2,150 RPM and my GPS (set to MPH) shows that I average about 93 MPH. // Below 2,500 feet // on a No wind morning. Factoring in the winds aloft, the true speed seems to work out between 90 and 94 MPH. A normal stall comes at about 51 MPH indicated. cruise speed is about 104-105 indicated. So it seems to indicate 10-12 MPH fast across the board. When my Tach is showing 2,100 RPM (a thumb tach reads 2,110) so the tach is pretty close at cruise. I will try to post a couple of pictures of the plumbing (pitot and static line out on the wing strut.) I am thinking I will do a low pressure test on the pitot line and the static line....(when disconnected from the ASI) and look for leaks. I never remember to look at the outside plumbing when I see another Taylorcraft on the ground......Always remember that after I have left..(I have never seen a static tube just bent back under the wing like mine is on ANY aircraft...(is this normal on the T-craft ??)..........Thanks again everyone...........Don in SC

**M Towsley** · 10-23-2011, 19:10

Re: Airspeed indicater reads too high

Don,

Though I am no expert, I have never seen a Taylorcraft with a static line set-up like that. I believe it is usually a line that terminates inside the wing.

**Ray36048** · 10-23-2011, 19:23

Re: Airspeed indicater reads too high

Something is not right here. I don't think that is a static line. I think it is an old pitot line that someone dissconnected for some reason. This one looks like it is metal and the one that is connected to the pitot looks like plastic. Did someone pull in a new plastic line and just leave the old metal one hanging?

If your static ports on the instruments are really hooked to this bent tube, I have no idea what the instruments will do. But, it is not right.

The normal Taylorcraft static line was inside of the wing.

**TreeTopFlier** · 10-23-2011, 19:46

Re: Airspeed indicater reads too high

Thanks, I believe I will go to my local A&I and see what he recommends...............Don in SC

**barnstmr** · 10-23-2011, 19:47

Re: Airspeed indicater reads too high

Originally posted by M Towsley View Post

Don,

Though I am no expert, I have never seen a Taylorcraft with a static line set-up like that. I believe it is usually a line that terminates inside the wing.

I think Marty is right

**M Towsley** · 10-23-2011, 20:08

Re: Airspeed indicater reads too high

I think Ray is right, looks like a replacement line for the original. Do you have that silicone tubing going to the ASI?

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