Original Posted By: John Greenlee
> Subject: trim> > > >> > >understand> >why adding engine thrust offset is standard practice as opposed tomaking> >trim adjustments with the control surfaces or trim tabs. I'm looking fora> >general answer and any special considerations applicable to the Piet.> >Thanks.> >> >Mark Boynton> >Phoenix, Arizona>>>>> >> >Simple answer- The Piet does not have adjustable trim tabs.> >> >Mike B ( Piet N 687 MB )> >> ________________________________________________________________________________
Pietenpol-List: trim
> Pietenpol-List: trim
Original Posted By: DonanClara(at)aol.com
> > > thanks for the input, but the point was missed> altogether. I read all of the previous posts on trim,> so I know how others are doing it. And I know you> don't need it. the point is, what do you think of the> method of doing it that I described. It seems like a> clean easy way of adding trim. A trim tab adds another> bump to the airfoil whereas tilting the entire tail> section leaves cleaner lines. And also it seems easier> to do than building a trim tab. I have an Idea in my> head on how it could be done. If I get some positive> input I will go ahead and lay it out on paper.> By the way Bernie P. put a trim system on "The last> Original" hangered in River Falls Wi. Which is now> owned by Andrew Pietenpol. I've been there and seen> it.> del> > Thousands of Stores. Millions of Products. All in one place.> Yahoo! Shopping: http://shopping.yahoo.com> > > > > > > ________________________________________________________________________________
> > > thanks for the input, but the point was missed> altogether. I read all of the previous posts on trim,> so I know how others are doing it. And I know you> don't need it. the point is, what do you think of the> method of doing it that I described. It seems like a> clean easy way of adding trim. A trim tab adds another> bump to the airfoil whereas tilting the entire tail> section leaves cleaner lines. And also it seems easier> to do than building a trim tab. I have an Idea in my> head on how it could be done. If I get some positive> input I will go ahead and lay it out on paper.> By the way Bernie P. put a trim system on "The last> Original" hangered in River Falls Wi. Which is now> owned by Andrew Pietenpol. I've been there and seen> it.> del> > Thousands of Stores. Millions of Products. All in one place.> Yahoo! Shopping: http://shopping.yahoo.com> > > > > > > ________________________________________________________________________________
> Re: Pietenpol-List: trim
Original Posted By: "Gene Rambo"
> > > Gene,> > I agree with you that the Mooney style elevator trim, where the whole > empennage moves is impractical for a Piet. It would be real hard to > engineer, and heavy. Using the jackscrew setup would be the way to go,ala > J-3. Again there is some engineering to do, but it would be much simpler.> > I also agree with Ken B., that elevator trim is a desirable option toput > on a plane (if you want to). I have definitely heard of elevator cable > breaks, cables jumping off pulleys, (although not a prob on a Piet). Ihave > by the way, landed a plane using just the trim wheel, and throttle, it'snot > only doable, it usually resulted in a very nice, soft squeaker! Del, drawit > up, and try it out!> > Like Ken, my 2 cents.> Gary Meadows> 14 Ribs and building> > > > > > > > > ________________________________________________________________________________
> > > Gene,> > I agree with you that the Mooney style elevator trim, where the whole > empennage moves is impractical for a Piet. It would be real hard to > engineer, and heavy. Using the jackscrew setup would be the way to go,ala > J-3. Again there is some engineering to do, but it would be much simpler.> > I also agree with Ken B., that elevator trim is a desirable option toput > on a plane (if you want to). I have definitely heard of elevator cable > breaks, cables jumping off pulleys, (although not a prob on a Piet). Ihave > by the way, landed a plane using just the trim wheel, and throttle, it'snot > only doable, it usually resulted in a very nice, soft squeaker! Del, drawit > up, and try it out!> > Like Ken, my 2 cents.> Gary Meadows> 14 Ribs and building> > > > > > > > > ________________________________________________________________________________
> Re: Pietenpol-List: trim
Original Posted By: "Gene Rambo"
> > > On Fri, 26 Nov 1999, Gene Rambo wrote:> > > > > I cannot imagine anything more difficult, from a structural standpoint,> > than making the entire aft 1/3 of the fuselage hinge. Think of thestress> > on the longerons at the hinge point (not to mention the hinges) . . .think> > of the weight added . .. where would you put the tailskid (wheel)? How> > would you keep the control cables tight as the tail moved? I do notthink> > I have ever heard of an elevator cable failure in any type aircraft(unless> > shot away in wartime). Flying by trim is not going to save you if sucha> > thing ever happened. Ever tried it?> > > > Sure, the Cessna 180 is often refered to as a plane you fly with thetrim. > The trim is very powerful as it uses a jack screw to change the angle of> incidence of the horizontal stab by about 7 degrees. > > If you've never heard of an elevator control failure, you haven't looked> very hard. I've read no less than a dozen reports of in-flight elevator> control failure where the trim was used in conjunction with throttle to> control the plane to a survivable landing. In fact, I seem to remember> reading in FAR Part 23 that the installation of a trim system is required> as a backup to the primary elevator control systems. > > The most famous of these was the United Airlines DC-10-10 that crashed in> Sioux City, IA. After the catastrophic destruction of one of the fan> rotors, all of the elevator primary control systems were severed. The> aircraft was controllled to a crash landing utilizing trim and throttle.> Although there were 111 fatalities, 185 survived. It would have been alot> worse had the trim been unavailable. > > Using full trim deflection to work against the remaining good elevator> control cable was a trick told to me by an old Newfoundland bush pilotwho> had the "down" elevator cable on his C-180 floatplane fail. The plane had> been in and out of salt water for most of it's life and the cable had> corroded from the inside out. The cable broke after take-off as the pilot> pushed the nose down to build speed (common practice on float equipped> 180's). The plane started to nose up into a stall. The pilot realized> what had happened and threw in full nose down trim. Cutting the powerwith> rising terrain in front and low airspeed really wasn't an option. He flew> an acceptable circuit and had a relatively uneventful landing. The> maintenance guys replaced the cable and nothing more was done. > > In Canada, we, as pilots, recieve a quarterly publication called the> "Aviation Safety Letter" which generally describes a number of accidents> and provides a commentary as to what went wrong. THe AME's also get a> similar newsletter (the name escapes me right now) that coversmaintenance> related accidents with a similatr commentary. My AME buddy forwards allof> his newsletters to me after he reads them as he knows that I will be> maintaining my plane. These newsletters reveal some shocking maintenance> problems that have also lead to control system failures. > > Fortunately, my plane calls for a trim system and one is being installed.> Boy, have I ever rambled on. > > Later, > > Ken Beanlands B.Eng (Aerospace)> Calgary, Alberta, Canada> Christavia MK 1 C-GREN> > > > > > > > > > ________________________________________________________________________________
> > > On Fri, 26 Nov 1999, Gene Rambo wrote:> > > > > I cannot imagine anything more difficult, from a structural standpoint,> > than making the entire aft 1/3 of the fuselage hinge. Think of thestress> > on the longerons at the hinge point (not to mention the hinges) . . .think> > of the weight added . .. where would you put the tailskid (wheel)? How> > would you keep the control cables tight as the tail moved? I do notthink> > I have ever heard of an elevator cable failure in any type aircraft(unless> > shot away in wartime). Flying by trim is not going to save you if sucha> > thing ever happened. Ever tried it?> > > > Sure, the Cessna 180 is often refered to as a plane you fly with thetrim. > The trim is very powerful as it uses a jack screw to change the angle of> incidence of the horizontal stab by about 7 degrees. > > If you've never heard of an elevator control failure, you haven't looked> very hard. I've read no less than a dozen reports of in-flight elevator> control failure where the trim was used in conjunction with throttle to> control the plane to a survivable landing. In fact, I seem to remember> reading in FAR Part 23 that the installation of a trim system is required> as a backup to the primary elevator control systems. > > The most famous of these was the United Airlines DC-10-10 that crashed in> Sioux City, IA. After the catastrophic destruction of one of the fan> rotors, all of the elevator primary control systems were severed. The> aircraft was controllled to a crash landing utilizing trim and throttle.> Although there were 111 fatalities, 185 survived. It would have been alot> worse had the trim been unavailable. > > Using full trim deflection to work against the remaining good elevator> control cable was a trick told to me by an old Newfoundland bush pilotwho> had the "down" elevator cable on his C-180 floatplane fail. The plane had> been in and out of salt water for most of it's life and the cable had> corroded from the inside out. The cable broke after take-off as the pilot> pushed the nose down to build speed (common practice on float equipped> 180's). The plane started to nose up into a stall. The pilot realized> what had happened and threw in full nose down trim. Cutting the powerwith> rising terrain in front and low airspeed really wasn't an option. He flew> an acceptable circuit and had a relatively uneventful landing. The> maintenance guys replaced the cable and nothing more was done. > > In Canada, we, as pilots, recieve a quarterly publication called the> "Aviation Safety Letter" which generally describes a number of accidents> and provides a commentary as to what went wrong. THe AME's also get a> similar newsletter (the name escapes me right now) that coversmaintenance> related accidents with a similatr commentary. My AME buddy forwards allof> his newsletters to me after he reads them as he knows that I will be> maintaining my plane. These newsletters reveal some shocking maintenance> problems that have also lead to control system failures. > > Fortunately, my plane calls for a trim system and one is being installed.> Boy, have I ever rambled on. > > Later, > > Ken Beanlands B.Eng (Aerospace)> Calgary, Alberta, Canada> Christavia MK 1 C-GREN> > > > > > > > > > ________________________________________________________________________________
> Re: Pietenpol-List: trim
Original Posted By: "Gene Rambo"
> > > Del,> The Mooney trim system has the empennage hinged at the top withto> forged aluminum fittings and a geared transmission at the bottom. The> transmission is operated by a torque tube which runs from the trim wheel> all the way back to the tail and the whole thing moves more than an inch.> I can't remember now just how much it moves, but I think it's more like> four or five inches. A consistant problem we had with this is that the> two bolts and a bushing in what we called the "saddle block link" would> wear out and often had to be replaced. The limit was to grab the> elevator a lift; there should be no more than a tenth of an inch play.> As far as installing this on a Pietenpol, it would take a lot ofwork. > The hinged portion on a Mooney is also bushed and occassionally these> would wear out causing sideways play in the horizontal stabilizer. As a> Mooney is wider than a Piet at the tail, there might be problems in> stabilizer stability due to the hinges being too close together. Also,> the entire tail would have to be redesigned and beefed up because the> entire section that the complete tail, the whole after fuselage under the> empennage moves with the actuator, not just the horizontal stabilizer. > Someone wrote and said that the aft third of the fuselage moves. This> is not true. The part that moves begins with the leading edge of the> stabilizer spar. The idea is the same, but the system of operation is> completely different than what Piper used on his Cub, Vagabond, and Pacer> series.> Another complication is this area is also where the tail wheelattaches.> Weight would certainly be another factor to contend with,although the> Mooney parts aren't particularly heavy. The last time I bought an> actuator (Mooney calls it a trim screw), it cost $600 and there has been> a big price increase since. If this trim screw fails, there is no> control of the tail trim at all, and as it is extremely effective, I> don't know that the elevator could keep maintain control. > There was an incident years ago that a Mooney was repaired atwhat was> then called "The Mod Center" in the factory. The trim screw was removed> to replace the tail and upon reinstallation, the installing mechanic> missed the hole in the trim screw, installing the bolt through the> attaching brackets only and pinching the trim screw in place. A> successful test flight was taken and the airplane delivered to the owner.> On his flight to San Antonio (sixty miles away) the trim screw came out> and the pilot made a very hard landing on the runway at International. > He broke his back, successfully sued Mooney, and the Manager of the Mod> Center lost his A.I. > A trim system that works would certainly be appreciated in aPiet,> although those who have installed a trim system using bungee cords say> they don't use it for local flights, just for long cross-country flights.> I talked to one guy at Brodhead this summer who had a small spring> attached to his seat with a hardware store turnbuckle to correct for nose> heaviness and this looked great. He had a air-cooled engine up front and> as we are using a Model A and I and my two partners don't weigh the same,> we're going to have tail heaviness problems unless one in particular goes> on a diet! Anyway, we plan on doing using the spring and turnbuckle> somehow; haven't really gotten that far yet.> To put a Mooney type trim on a Piet sounds like an interestingproject,> but it would be very complecated and add a lot of weight. The parts> would have to be virtually indestructable and foolproof as a run away> trim is extremely serious. I like the spring and turnbuckle method> because it follows the KISS principle -- Keep It Simple, Stupid.> If you would like to continue with this, I can give you moreinformation> on it. I stall have contacts at Mooney engineering.> > John Langston > > > > > > > ________________________________________________________________________________
> > > Del,> The Mooney trim system has the empennage hinged at the top withto> forged aluminum fittings and a geared transmission at the bottom. The> transmission is operated by a torque tube which runs from the trim wheel> all the way back to the tail and the whole thing moves more than an inch.> I can't remember now just how much it moves, but I think it's more like> four or five inches. A consistant problem we had with this is that the> two bolts and a bushing in what we called the "saddle block link" would> wear out and often had to be replaced. The limit was to grab the> elevator a lift; there should be no more than a tenth of an inch play.> As far as installing this on a Pietenpol, it would take a lot ofwork. > The hinged portion on a Mooney is also bushed and occassionally these> would wear out causing sideways play in the horizontal stabilizer. As a> Mooney is wider than a Piet at the tail, there might be problems in> stabilizer stability due to the hinges being too close together. Also,> the entire tail would have to be redesigned and beefed up because the> entire section that the complete tail, the whole after fuselage under the> empennage moves with the actuator, not just the horizontal stabilizer. > Someone wrote and said that the aft third of the fuselage moves. This> is not true. The part that moves begins with the leading edge of the> stabilizer spar. The idea is the same, but the system of operation is> completely different than what Piper used on his Cub, Vagabond, and Pacer> series.> Another complication is this area is also where the tail wheelattaches.> Weight would certainly be another factor to contend with,although the> Mooney parts aren't particularly heavy. The last time I bought an> actuator (Mooney calls it a trim screw), it cost $600 and there has been> a big price increase since. If this trim screw fails, there is no> control of the tail trim at all, and as it is extremely effective, I> don't know that the elevator could keep maintain control. > There was an incident years ago that a Mooney was repaired atwhat was> then called "The Mod Center" in the factory. The trim screw was removed> to replace the tail and upon reinstallation, the installing mechanic> missed the hole in the trim screw, installing the bolt through the> attaching brackets only and pinching the trim screw in place. A> successful test flight was taken and the airplane delivered to the owner.> On his flight to San Antonio (sixty miles away) the trim screw came out> and the pilot made a very hard landing on the runway at International. > He broke his back, successfully sued Mooney, and the Manager of the Mod> Center lost his A.I. > A trim system that works would certainly be appreciated in aPiet,> although those who have installed a trim system using bungee cords say> they don't use it for local flights, just for long cross-country flights.> I talked to one guy at Brodhead this summer who had a small spring> attached to his seat with a hardware store turnbuckle to correct for nose> heaviness and this looked great. He had a air-cooled engine up front and> as we are using a Model A and I and my two partners don't weigh the same,> we're going to have tail heaviness problems unless one in particular goes> on a diet! Anyway, we plan on doing using the spring and turnbuckle> somehow; haven't really gotten that far yet.> To put a Mooney type trim on a Piet sounds like an interestingproject,> but it would be very complecated and add a lot of weight. The parts> would have to be virtually indestructable and foolproof as a run away> trim is extremely serious. I like the spring and turnbuckle method> because it follows the KISS principle -- Keep It Simple, Stupid.> If you would like to continue with this, I can give you moreinformation> on it. I stall have contacts at Mooney engineering.> > John Langston > > > > > > > ________________________________________________________________________________
> Pietenpol-List: Piet trim ala Mooney
Original Posted By: del magsam
> > > "Piet-List Engineering Group",> > Ref: "I cannot imagine anything more difficult, from a structural> standpoint, than making the entire aft 1/3 of the fuselage hinge..."> > Actually, the Mooney system is simplicity in it's self. Two large > plates, one on the fuselage, the other on the flying tail, with a hinge> at the top and the trim screw at the lower portion connecting them. To> look at it all, one would think it to be rather not up to the job, > structurally, BUT, it works rather well. I don't recall ever hearing of> one ever falling off in all the eleven years or so that I worked at> Mooney. I did hear of one man who picked up a brand new Mooney at the> factory and flew it back to the gulf coast somewhere and just around> Beaumont Tx, got sucked up into a thunderstorm. Up up he went in the> clouds, and then down down he came, and when he exited the base of the> clouds he was inverted in a spin so he recovered and landed at the > nearest field and noted that there was extra diheidral in the wings and> some of the rivets were missing. He called the factory and said he had> a problem and described it to them. Not sure how Mooney got the plane> back to Kerrville, but, did hear that the engineering guys said that> due to the extra amount of bend in the wings and the missing rivits> that he must have gone to maximum loading plus some. However, the tail> did stay on, but Bill Wheat, one of the engineers, (keeper of the Mooney> flame), said that the wing is hell-for-stout, but... (pause) not the > tail, he was lucky.> > It could be done, it would be heavy, it would be unique. But to> compensate, the wing would have to move backward again... all told, an> engineering triumph! A piece of cake. Sort of a Piet and a half.> > Mooney makes it look simple, and I guess that's the way it is with lots> of good engineering, but it could be a nightmare for a Piet.> > Rodger> > > > > > > ________________________________________________________________________________Date: Fri, 26 Nov 1999 19:58:11 -0800 (PST)
> > > "Piet-List Engineering Group",> > Ref: "I cannot imagine anything more difficult, from a structural> standpoint, than making the entire aft 1/3 of the fuselage hinge..."> > Actually, the Mooney system is simplicity in it's self. Two large > plates, one on the fuselage, the other on the flying tail, with a hinge> at the top and the trim screw at the lower portion connecting them. To> look at it all, one would think it to be rather not up to the job, > structurally, BUT, it works rather well. I don't recall ever hearing of> one ever falling off in all the eleven years or so that I worked at> Mooney. I did hear of one man who picked up a brand new Mooney at the> factory and flew it back to the gulf coast somewhere and just around> Beaumont Tx, got sucked up into a thunderstorm. Up up he went in the> clouds, and then down down he came, and when he exited the base of the> clouds he was inverted in a spin so he recovered and landed at the > nearest field and noted that there was extra diheidral in the wings and> some of the rivets were missing. He called the factory and said he had> a problem and described it to them. Not sure how Mooney got the plane> back to Kerrville, but, did hear that the engineering guys said that> due to the extra amount of bend in the wings and the missing rivits> that he must have gone to maximum loading plus some. However, the tail> did stay on, but Bill Wheat, one of the engineers, (keeper of the Mooney> flame), said that the wing is hell-for-stout, but... (pause) not the > tail, he was lucky.> > It could be done, it would be heavy, it would be unique. But to> compensate, the wing would have to move backward again... all told, an> engineering triumph! A piece of cake. Sort of a Piet and a half.> > Mooney makes it look simple, and I guess that's the way it is with lots> of good engineering, but it could be a nightmare for a Piet.> > Rodger> > > > > > > ________________________________________________________________________________Date: Fri, 26 Nov 1999 19:58:11 -0800 (PST)