Pietenpol-List: Pietenpol building practices
Posted: Sun Sep 05, 2004 11:59 am
Original Posted By: "Gordon Bowen"
Hello fellow Pieters,I am sitting here in SW Florida, hunkered down while Frances circles us(thankfully), catching up on my tardy reading of email from the last month.ATIS said the airport just closed until the winds die down. I am listeningto my neighbor's sailboat with its self-UNfurling jib self destruct in thewind. You might wonder at this point what this has to do with a Pietenpol.I was going to fly up to Brodhead and OSH this year until I got grounded bythe family since my oldest twin daughter was going to have here own twins.I had 3 weeks of vacation time to spend locally so I volunteered to be atest pilot for two new Pietenpol GN-1s. I flew over 55 hours during thistime. The biggest thing I learned is what we already know. We are totallygoverned by Murphy's Law.What does this have to do with a Piet? Anything that can go wrong will. Ifyou look at a part and say to yourself, "Self, as long as no one bumps it,or pushes too hard, or stands on it (you fill in the blank - there are lotsof them)," I can guarantee that you/someone will. What you have to do isbuild everything to counter anything that can go wrong. That doesn't meanadd 50 pounds in the form of armour. Bernie did an awful lot of thinkingfor us. He has covered most things. Make sure you don't change the plansand end up weakening something. This is especially true in the importantareas. Some of the obvious important areas are motor mounts, landing gearand wing attachments. Some of the less obvious areas, that are soooimportant, are the controls. Make sure the aileron, rudder and elevatorcontrols are free and bullet proof.Enough generalities and to the point. I was flying along in my normal mode,fat dumb and happy, when the rear aileron of the right wing started flappingat me (now you finally know why the hurricane reminded me to write this).The rear spar was flipping up and down about 6" and my first thought was itbroke. Then I noticed the left wing was doing the same thing and the F workcame out. I immediately reduced power and the Flutter quit. I then noticedthat I had NO ailerons. Complete side to side stick movement did nothing.Fortunately, I usually fly with using the rudders to lift the wing and thecrosswind landing was not an issue.What was the cause and how could this have been prevented? On a GN-1 theaileron cables sneak out along the floor from the bottom of the passengercontrol stick to the fuselage side and then turn around a pulley 90 degreesupward to the wing. The pulley bracket in this case was held to thefuselage side with one bolt. The bolt allowed the pulley to pivot upwardscausing a loss of all tension. The owner had also mentioned that he foundthe pulley bracket bent and he supposed that someone had gotten into thepassenger compartment while parked at a Memorial Day event. I now suspectthat a thunderstorm blew through while it was parked outside and the windforce on the ailerons bent the bracket. I designed, and the ownerinstalled, a simple metal gusset to secure the other end of the pulley boltand that eliminated the possibility of both the bending and pivoting of thepulley bracket.My purpose for writing this is to tell you that finding out about thesethings in the air is not the place to learn. Try to anticipate the hugeforces that will be put on some of these parts and prepare ahead of time.You can rest assured that the Pietenpol I am now building will have all ofthese things reviewed in a different light because of my experience learnedtesting these two planes. Remember, experience is something you get rightafter you need it.Ted BrousseauNaples, Florida________________________________________________________________________________
Hello fellow Pieters,I am sitting here in SW Florida, hunkered down while Frances circles us(thankfully), catching up on my tardy reading of email from the last month.ATIS said the airport just closed until the winds die down. I am listeningto my neighbor's sailboat with its self-UNfurling jib self destruct in thewind. You might wonder at this point what this has to do with a Pietenpol.I was going to fly up to Brodhead and OSH this year until I got grounded bythe family since my oldest twin daughter was going to have here own twins.I had 3 weeks of vacation time to spend locally so I volunteered to be atest pilot for two new Pietenpol GN-1s. I flew over 55 hours during thistime. The biggest thing I learned is what we already know. We are totallygoverned by Murphy's Law.What does this have to do with a Piet? Anything that can go wrong will. Ifyou look at a part and say to yourself, "Self, as long as no one bumps it,or pushes too hard, or stands on it (you fill in the blank - there are lotsof them)," I can guarantee that you/someone will. What you have to do isbuild everything to counter anything that can go wrong. That doesn't meanadd 50 pounds in the form of armour. Bernie did an awful lot of thinkingfor us. He has covered most things. Make sure you don't change the plansand end up weakening something. This is especially true in the importantareas. Some of the obvious important areas are motor mounts, landing gearand wing attachments. Some of the less obvious areas, that are soooimportant, are the controls. Make sure the aileron, rudder and elevatorcontrols are free and bullet proof.Enough generalities and to the point. I was flying along in my normal mode,fat dumb and happy, when the rear aileron of the right wing started flappingat me (now you finally know why the hurricane reminded me to write this).The rear spar was flipping up and down about 6" and my first thought was itbroke. Then I noticed the left wing was doing the same thing and the F workcame out. I immediately reduced power and the Flutter quit. I then noticedthat I had NO ailerons. Complete side to side stick movement did nothing.Fortunately, I usually fly with using the rudders to lift the wing and thecrosswind landing was not an issue.What was the cause and how could this have been prevented? On a GN-1 theaileron cables sneak out along the floor from the bottom of the passengercontrol stick to the fuselage side and then turn around a pulley 90 degreesupward to the wing. The pulley bracket in this case was held to thefuselage side with one bolt. The bolt allowed the pulley to pivot upwardscausing a loss of all tension. The owner had also mentioned that he foundthe pulley bracket bent and he supposed that someone had gotten into thepassenger compartment while parked at a Memorial Day event. I now suspectthat a thunderstorm blew through while it was parked outside and the windforce on the ailerons bent the bracket. I designed, and the ownerinstalled, a simple metal gusset to secure the other end of the pulley boltand that eliminated the possibility of both the bending and pivoting of thepulley bracket.My purpose for writing this is to tell you that finding out about thesethings in the air is not the place to learn. Try to anticipate the hugeforces that will be put on some of these parts and prepare ahead of time.You can rest assured that the Pietenpol I am now building will have all ofthese things reviewed in a different light because of my experience learnedtesting these two planes. Remember, experience is something you get rightafter you need it.Ted BrousseauNaples, Florida________________________________________________________________________________