The International Cessna^® 170 Association

Flying back from the paint shop, with a brand spanking new paint job, I noticed my airspeed indicator was reading less than my actual airspeed. The pitot static port is clear but noticed the pitot tube seems to be bent down.

Can this cause the AI to be off?

Just how should the pitot tube be aligned relative to the leading edge?

Thanks- Jim layman

james_layman wrote:Flying back from the paint shop, with a brand spanking new paint job, I noticed my airspeed indicator was reading less than my actual airspeed. The pitot static port is clear but noticed the pitot tube seems to be bent down.

Can this cause the AI to be off?

Just how should the pitot tube be aligned relative to the leading edge?

Thanks- Jim layman

Yes, misalignment will cause the airspeed reading to be off.
So will a partially plugged line (paint chip, sanding dust, stripper, etc.).
A bad hose connection in the system, a cracked hose or hard line, will, too.
Some careless mechanic's helper may have tried to blow the line out with an air blast, and damaged something.
This happened on my brother's 170 at the paint shop.
Your system needs to be thoroughly inspected.
According to the Cessna 100 Series Service Manual, Pre-1962, the 150, 172, 175, pitot tube open end should be perpendicular to the vertical axis and parallel to the longitudinal axis of the aircraft.
The 170 should be equal to the 172 spec.
Other opinions are welcomed.

I believe it is the 100 series service manual that has a template the can be duplicated cut out and used to line up the stock curved standard pitot tube.

Of course for those with the heated pitot or and none standard (like mine) installation it won't work.

Afew years ago a fella in this area picked up his plane ( piper low wing )at a paint shop and
crashed in a field on his way home. Fuel vents were plugged with tape or paint.(can't remember which)
pays to check real closely after fresh paint .

Thanks for the ideas. Checked fuel vent, pitot static and pitot tube opening before leaving. Since it seemed OK before the paint and after noticing the tube was now pointing somewhat downward I hope it is an alignment issue. Plan to get hold of the template and see if I can move it back up.

james_layman wrote:Thanks for the ideas. Checked fuel vent, pitot static and pitot tube opening before leaving. Since it seemed OK before the paint and after noticing the tube was now pointing somewhat downward I hope it is an alignment issue. Plan to get hold of the template and see if I can move it back up.

If you can't get a template, this description is from the manual:

According to the Cessna 100 Series Service Manual, Pre-1962, the 150, 172, 175, pitot tube open end should be perpendicular to the vertical axis and parallel to the longitudinal axis of the aircraft.

Simple translation: The open end of the tube faces directly and squarely forward. (Eyeball is just fine. Minor misalignment is not going to influence impact air pressure.)