| Author | Message | ||
     Tom R. Hutchison (Tomhutch) |
Where and how are folks installing their pitot tube? The best information I have been able to find so far comes from Tony Bingelis's book. He recommends at least 5" below the wing. And on laminar flow airfoils to be under the "maximum curvature". How did you mount it? Any suggestions, opinions etc. appreciated | ||
| Bill Copeland |
Tom: We have a "Piper" type, heated "bayonet" static/pitot tube mounted under the left wing on a removable access cover which we added between the outboard rib and the end of the upper and lower wing skins. The bayonet is located approximately 16inches aft of the leading edge and is near the thickest part of the airfoil at that station. We did this to facilitate the permanent attachment of the wing tip fairing. Our wingtip fairing is not attached with screws as called for in the construction docs. The opening for the cover is about 10inches X 10inches and is placed just forward of the main spar. This allows access for maintainance on the landing light(s), the strobe and position lights, the strob power unit(s) and just enough room to R and R the aileron counter weight. It's tight, but it works. I thought I had published some pics of this procedure in the EXPRESS Link, but in a quick review of the back issues I couldn't find a reference. I can get pics for you if you like. Permanent mounting of the wing tip fairing sure makes for a clean wing tip. Bill C | ||
| Tom R. Hutchison (Tomhutch) |
I am considering bonding on the wing tips with an access door like you describe. However I wouldn't be able to remove my SkySport fuel probes if they ever fail. What did you do for a fuel quantity measure? If I could figure out how to remove the fuel probes with a permanent wing tip I would do it. Thanks for the pitot mounting information. Tom | ||
| Bowser |
Put the pitot tube in the best location with no interference from local structures, no areas where airflow turns corners, propeller flow fields, etc. Look at the locations of pitot tubes on low wing aircraft, i.e., Bonanzas, Cherokees, Mooneys, etc. Place the pitot tube below the wings outboard of the propeller flow. Use an L-shaped probe with the probe opening being located aft of the wing's leading. As Tony Bingelis says on page 245 of "The Sportplane Builder," in the 4th paragraph and in "Sportplane Construction Techniques" on page 279 in the 3rd paragraph on the right side of the page. This is to prevent from someone walking into the probe, while it is in a location which will give the most undisturbed airflow. The probe most be in a location to sense the best possible initial airflow, i.e., to sense free airflow ahead of the aircraft. | ||
| Tom R. Hutchison (Tomhutch) |
Henri Walser sent me these pictures of his pitot installation. I thought I would share them with everyone.  | ||
| Tom R. Hutchison (Tomhutch) |
After considering everyone's excellent advice I mounted my pitot tube as shown in the picture below. I had bought the RV install kit from Aircraft Spruce (DAMM expensive piece of tin, but sure looks nice!). I cut out a square of the inner wing skin and foam. Millfibered a block of 1/2" 20 lb. foam with 4 AN mounting bolts potted to hold the RV mounting tube/bracket. I'll lay 2 bid over it next for good measure. Then a little fairing on the tube/wing interface. I wanted a very strong mount for the pitot tube. It just hangs out there asking for abuse.  | ||
| Gary Markwardt |
Following is a photo of the Express pitot tube installation on my Series 2000. The tube is from Aircraft Spruce part no. AN5814-12. I believe Express fabricated the attachment support, although the RV kit shown in the AS catalog works as mentioned in Tom's posting above.  | ||
| Gary Markwardt |
After reading the directions, here is the image!  | ||
| Reinhard Metz |
My pitot tube installation is just like Gary's and works very well. Two observations: 1) I used 1/4"o.d., 1/8" i.d. urethane tubing from McMaster/Carr instead of nylon. It is softer and seals better in a wide range of climatic conditions, and the smaller inner diameter dampens any tendancy of the airspeed indicator needle to vibrate under some conditions. 2) Don't use the static port of this pitot to feed the autopilot altitude hold transducer, as this type of pitot is notorious for creating a loop instability in the dynamics of the altitude hold system. (unless you like +/- 200 ft every 10 seconds roller coaster rides!) I ran a separate nylon line out into the wingtip area, inside the wing, for the transducer feed. Here the air is calm, and the exact pressure does not matter, yet linearly tracks the altitude. Reinhard Metz |