Airspeed Indicator Tubing

[Grant S. Bailey]

I think I might replace the airspeed indicator tubing in my left wing before I close things up. When I blow through it, seems like a lot of resistance?? Looks like 3/16" OD aluminum tubing. Does anyone know what type of aluminum tubing should be used? Would this resistance be normal for a six foot length of this tubing with a few 90 bends in it?

[Len Petterson]

Re: Airspeed Indicator Tubing

In mine there is 1/4" tubing in the wing root and to the Airspeed indicator.
Remember there is no flow in this tubing as the airspeed indicator is a pressure gauge.
Len

[VictorBravo]

Re: Airspeed Indicator Tubing

The ASI does have flow, just not much. Air goes in through the pitot tube and if there are line losses or restrictions then the ASI response time will have a lag.There may not be flow completely through the instrument, but the instrument response time is affected by the line losses on the pitot side. IMHO, use large tubing and keep it clear. Instant airspeed indication can be important when flying through low wind shear and turbulence. The speed and magnitude of the swings in ASI readings give you information about how muchthe turbulence is affecting you.

[flyguy]

Re: Airspeed Indicator Tubing

Anyone else ever fly with a bug nest (or whatever it was) in the pitot tube. I did it with a C150, and talk about a weird experience. Rotate when it feels right and then glance over at the airspeed (I know, I know) and it's showing about 35 knots and you're already flying. Really wakes you up.
Airspeed creeps up to correct value, creeps down to correct value. I just kept all the other numbers normal and took it around the pattern and landed, but it was a good education. Technically, if not tactfully, there is bi-directional flow.
Darryl

[selje]

Re: Airspeed Indicator Tubing

I once washed a plane and then flew it. Had the same problems from water in the tubing, the airspeed indicator was bouncing all over the place -- just fly by feel and orientation with the ground and it evaporates in about 12 to 15 minutes. Best to watch and prevent during washing.

[Dano"T"]

Re: Airspeed Indicator Tubing

I waxed my plane and got a glob on the pitot flipper hinge. The flipper wouldn't flip open....so....no airspeed indication. You can just feel if your at the right speed in your "cheeks"...once you flare you got er made...unless your cheeks tell you your going to darn fast and you float all the way to the end of the 1000' strip your trying to land at. Then your cheeks clinch together and say push right hand forward please. Anyways make sure the flipper works on pre flight (if you have one).

[birdlegs]

Re: Airspeed Indicator Tubing

I once had a flight instructor who would grab the tube and unplug the air flow to the asi on the taylorcraft we flew and make me shoot landings with the "feel"and "sound"of it.....good lessons.
Brad

[Victor Gisclair]

Re: Airspeed Indicator Tubing

I had the pitot flipper hinge stuck on my PA22/20 Pacer. I took off and as i gain speed the gage went to -20 or so mph. I slow down and landed and fixed the problem. It Has not happen since.

[flyguy]

Re: Airspeed Indicator Tubing

Sounds like everyone did better than the Trans international Airline guys did with their B727 a few years ago. Cross-switched the pitot heat with something else and the last thing on the recorder was, "Man this thing is really going upstairs good tonight." Spun that sucker in. If your gauges tell you it's doing something that you know it can't do--THEN SOMETHING IS WRONG. Right?
Darryl