Airspeed indicator always reads low

[Merlinspop]

It's hard to see in the photo where the airspeed indicator is.
Good luck.

I believe it's in the white box between to two frame members approximately above the occupants' knees.

[3Dreaming]

Mike, being behind the pod might create a small low pressure area. The low pressure might increase as speed increases. Likely the readings will be close a slow speed and will indicate a higher than actual speed the faster you go. The good thing is once installed the readings will not change, so you can come up with some good numbers to fly by.

Just curious, was the static tube open on the front end like the pitot? If it was that was the problem if not you likely had it located in an area of high pressure. Tom

[NJMike]

I have about an 8" long tube connected to and terminated downward so nothing falls in it. But I guess a bug find it's way in. I'll try blocking the end like you said.

[3Dreaming]

Mike, I was asking obout your original installation when I ask about the tube being forward.

[NJMike]

Ha. Okay, I missed that.

Yes, it was in front of the windshield with the pitot tube. Why would that make a difference?

[3Dreaming]

If it was open to the front or in an area of positive pressure your ram air would be pushing against pressure and would not work correctly.

[NJMike]

Oh, sorry.

The static tube is not open on the front end. It looks like a legitimate static tube - 8 tiny holes around the outside. It looks like it came as part of a pitot static installation kit. The tubes match in design, color, etc.

Now, picture the big bubble windshield in the picture in this thread. The bottom of the windshield is in front of your feet and below them, extending upward and backward to the steel cross tube above and forward of where your head would be.

The ASI is mounted between my feet, about 12-18" behind the windshield.

Below 50mph, it read the same as the Hall ASI.

Above 50mph, the difference increased...with the Hall ASI reading higher. That makes sense to me, because after I started using the Hall ASI, I could no longer maintain a cruise power setting...at 65% power I was exceeding the Vma. I had to reduce to below cruise setting to keep that from happening.

At 65% power, the new ASI read about 7mph lower than the Hall, which puts it pretty close to published numbers. If the static port was in an area of lower pressure, because of being behind the windshield, wouldn't that cause the ASI to read higher than the Hall ASI, which is mounted out on the strut, totally separate from the new ASI?

I'll get a better feel for it after another flight.