Has anybody converted to C180 gear legs? Was it by STC, form 337, or one time field approval? Any comments on good or bad effects of conversion? Any other comments?
Thanks,
Jake Boyd
C170A Gear conversion to C180 Gear
Moderators: GAHorn, Karl Towle, Bruce Fenstermacher
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N170BP
- Posts: 552
- Joined: Mon Jul 22, 2002 7:24 pm
With apologies to those who have done so (or own an airplane
which already has the conversion), why would you want to
do so?
Cessna designed the stock 170 gear to perform with the stock
weight of the airframe and associated loads. I've flown early
C-180s with 185 gear legs, and I found I didn't like them (I
prefer the stock gear legs). The thickness (and arch, stiffness,
etc.) of various Cessna gear legs were modified over the years
(increased thickness, etc.) to allow for the higher gross weights of
the later aircraft. Putting these "stiffer" gear legs on an earlier
(lighter) airframe is, in my opinion, a waste of time, weight & money.
(flame retardent suit donned!).
Bela P. Havasreti
'54 C-170B N170BP
which already has the conversion), why would you want to
do so?
Cessna designed the stock 170 gear to perform with the stock
weight of the airframe and associated loads. I've flown early
C-180s with 185 gear legs, and I found I didn't like them (I
prefer the stock gear legs). The thickness (and arch, stiffness,
etc.) of various Cessna gear legs were modified over the years
(increased thickness, etc.) to allow for the higher gross weights of
the later aircraft. Putting these "stiffer" gear legs on an earlier
(lighter) airframe is, in my opinion, a waste of time, weight & money.
(flame retardent suit donned!).
Bela P. Havasreti
'54 C-170B N170BP
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Bill Rusk
- Posts: 62
- Joined: Fri May 17, 2002 11:19 pm
To all
Bela certainly makes some valid points, but I would also add that airplanes are also, or were also, designed within certain cost constraints. If they could not be produced for X dollars then they would not compete with the Stinson, Cherokee 140 etc. If the gear could be made better but it cost too much then the gear was made adequate within whatever cost constraints existed at that time. It might only be a little more money but when multiplied by 100's of other items that only cost a little more it would put the aircraft out of the competition. Also, the legal climate was less stringent in 1950, so I don't think that entered into design criteria as much as it currently does. In a nutshell, it is possible to improve on the airplanes, and beauty is in the eye of the beholder. Bela did not prefer the stiff gear and I tend to agree personally but for your application you may find it to be a good match. I would guess it will cost you a min of 3000 dollars.
Good luck
Bill, with a flame tourch, ha, ha.
Bela certainly makes some valid points, but I would also add that airplanes are also, or were also, designed within certain cost constraints. If they could not be produced for X dollars then they would not compete with the Stinson, Cherokee 140 etc. If the gear could be made better but it cost too much then the gear was made adequate within whatever cost constraints existed at that time. It might only be a little more money but when multiplied by 100's of other items that only cost a little more it would put the aircraft out of the competition. Also, the legal climate was less stringent in 1950, so I don't think that entered into design criteria as much as it currently does. In a nutshell, it is possible to improve on the airplanes, and beauty is in the eye of the beholder. Bela did not prefer the stiff gear and I tend to agree personally but for your application you may find it to be a good match. I would guess it will cost you a min of 3000 dollars.
Good luck
Bill, with a flame tourch, ha, ha.
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jake boyd
- Posts: 9
- Joined: Mon Jun 17, 2002 4:03 am
Thanks gentlemen for you input. What generated the question is that during take off, just before lift-off at about 55mph the airplane quite often starts to spring up and down on the gear making it difficult to transition to a smooth lift off. I keep the tail just high enough to avoid premature liftoff. Maybe it is technique or maybe airspeed indicator is off a bit. I thought that maybe stiffer gear would be an answer. Possibly the gear on my aircraft is worn as it seems to sit with the spring legs slightly arched out. Possibly the axle shims need adjustment, any ideas where to get a set of various shims? Open to all comments and thanks.
Jake Boyd
Jake Boyd
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GAHorn
- Posts: 21290
- Joined: Fri Apr 12, 2002 8:45 pm
Well, I wrote one of my standard "how to build a clock" replies to this "what time is it" question, and after I finished, the Trojan Horse virus authored by Joe Harris, I'm sure, caught me and locked my computer up. Me 
Joe 
Anyway, here's the jist of the message (shortened believe it or not.)
As Parts/Mx coordinator one of my torments is the number of emails I get about this subject. I get all kinds of inquiries about the measurements of different 180/185 gear vs 170 gears, etc. and I just want to unplug the computer when I get them. It's my cross to bear, I guess. (Ok, Horn. Quit b----ing!)
Bill, your comments are certainly valid also, but I'll point out a weakness in your position. When Cessna designed/built the 170 they were fully aware of production cost risks and they frankly came up with a home-run. They bought the licensed production rights to famed racer Steve Witman's spring gear. By so doing, not only did they come up with a more cost effective landing gear than either Stinson or Piper ever could, ...they also had a more robust, trouble-free design than the complex mechanical/oleo gears of the "competition". Stinson was already a dying dinosaur of a rag airplane in a brave new world of all-metal designs. Stinson was no competition for the new Cessna's. Piper was also falling behind with their rag Tri-Pacer with it's bungee-sprung gear. Your point is incorrect regarding the Cherokee as it was not yet invented, so Cessna's 170 was not yet competing with it. When the Cherokee came out, it still never had the rugged simplicity of the Witman gear, and it never overtook the Cessna 170/172 series which went on to become the all-time production king of the light plane industry...with it's spring gear. (The much-later tube gear was not a condemnation of the spring, but an improvement in weight.) So, I believe the comment that the spring-gear was a design-deficiency to accomodate cost savings is not valid. It's cost savings was a bonus to a great design, and Stinson couldn't change their type certificate and Piper couldn't buy the production license. (In fact, Piper actually bought out Stinson and basically shut them down after converting the Twin-Stinson to all metal covering and naming it the Apache.)
Anyway, I've found that the conversion-to-180-gear folks fall into two basic camps.
Camp One are the folks who don't like/haven't adjusted to the spring rates of the Witman gear. I'm intrigued by this group because the first 170 I flew was an A-model owned by a highly experienced co-worker who'd owned it for over 22 years and he complained about the gear as he checked me out in it preparatory to my picking up N146YS. He really didn't like the "bounciness" of the gear. After our check out flight, he remarked how I didn't seem to fight it like he did. I attribute that to having learned taildraggers in C-120's and 140's in my youth while flying pipeline patrols. (You might not be able to teach an old dog new tricks....but you'll have hell breaking him of old ones!)
I believe that, just like my buddy, after some competent flight instruction from someone who teaches a "light touch" technique, most folks will find the original gear to be a great landing gear. (I've got to admit tho', like a drop-dead-gorgeous girlfriend, ...I never really trust her. And also like that DDG girlfriend, I find a light, easy touch works better at encouraging desired behaviour than a heavy hand of "control.")
Camp Two is made up of the folks who use their 170's as work horses in rough terrain. Their desire is to have a gear that isn't so obviously under-equipped to handle heavy loads in unimproved areas, and to get more prop-clearance from the rocks and gravel. Personally, I think this is a better reason for conversion.
In fairness I should mention that there were three different spring gears on the various 170's. The first rag-wing airplane had PN 0441138. That spring-rate was changed with the 170A's to PN 0441138-3, which continued all the way thru SN 19218. Starting at SN 19219 thru the rest of A-model production, and up to B-model SN 25611, PN 0541114 was used. All those were interchangeable left/right, and they were considerably more "springy" than the next landing gear, which started at B-model SN25612 and is also called the "lady legs" because of a narrower "ankle" just above the axle. They also were no longer interchangeable left/right. This last spring-gear is definitely more predictable than any of the earlier ones, but that is not to say the earlier ones are unmanageable. They are just different. Try to think of them all as the raison de entre' for getting a taildragger instead of one of those "Land-O'Matic's"
that came later on.
Bela, there were no "higher gross weights" later on. There were some changes in empty weights, however, that did cause Cessna to look into spring-rate changes. The airplane definitely lands better when it's heavier than it does when light on an early gear.
Jake, maybe it is your technique. The book (Owner's Manual) recommends a "tail low" takeoff. Here's how I teach the technique for takeoff.
During preflight, place the trim wheel in a position that will streamline the trim tab with the elevator. Note that position of your trim wheel for the future. (And by the way, it should be in the middle of the takeoff position placard. If it's not, then have your mechanic calibrate it by repositioning it within the trim wheel cover on it's positon with the wheel's indexing grooves. Then make certain that full travel of the tab is in accordance with the specs.)
Line up with the runway, hold the yoke fully back and smoothly apply full power, taking note that correct static rpm is achieved. (approx 2230). Use brakes early on, and then rudder-only as it becomes effective, to maintain runway alignment.
As the airplane accelerates and the rudder becomes effective, the elevator is also becoming effective, so nuetralize the yoke in pitch to it's elevator-nuetral position. (This roughly places your hand even with the doorpost. Check this out on the ground. Look back at your elevator counterweights, and position them faired in alignment with the leading edge of the horizontal stabilizer. Then look at your yoke position and memorize that position for future takeoffs.) During the takeoff roll, maintain that position until the relative wind no longer requires you to hold the yoke in that position (In other words, pay attention to the effort you make to hold the elevator nuetral. In a moment you'll realize as the relative wind has increased due to acceleration, that you have relaxed the pressure on the yoke and the relative wind is what is holding the elevator nuetral.) This "free-flying" nuetral elevator will now allow the relative wind to lift the tailwheel off the ground. (The actual weight of the elevator falling against the relative wind, will cause sufficient lift of the horizontal to bring the tail up, and the nose down, so that the airplane is now running along on it's main wheels only.)
As the airplane further accelerates you'll notice the nose will begin to descend lower relative to the horizon. At this point apply light back-pressure to the yoke, and the airplane will gently lift itself off the ground very nicely, thank you.
And when it come back to doing a wheel-landing,...that tail-low position is also the exact same position you want to achieve just as your wheels roll onto the runway. Then all that's necessary is to push the yoke forward to increase weight upon the mains, and ....voila! A wheel landing!
Back to the tail low position, ...if you continue to hold the yoke back against ever-increasing pressure (against gravity due to decreasing relative wind) eventually the tailwheel will touch the ground and ...voila! A three-point. (Little secret: When light, the B-model will land with 30-degrees flaps better than it will with full flaps.)
Joe Anyway, here's the jist of the message (shortened believe it or not.)
As Parts/Mx coordinator one of my torments is the number of emails I get about this subject. I get all kinds of inquiries about the measurements of different 180/185 gear vs 170 gears, etc. and I just want to unplug the computer when I get them. It's my cross to bear, I guess. (Ok, Horn. Quit b----ing!)
Bill, your comments are certainly valid also, but I'll point out a weakness in your position. When Cessna designed/built the 170 they were fully aware of production cost risks and they frankly came up with a home-run. They bought the licensed production rights to famed racer Steve Witman's spring gear. By so doing, not only did they come up with a more cost effective landing gear than either Stinson or Piper ever could, ...they also had a more robust, trouble-free design than the complex mechanical/oleo gears of the "competition". Stinson was already a dying dinosaur of a rag airplane in a brave new world of all-metal designs. Stinson was no competition for the new Cessna's. Piper was also falling behind with their rag Tri-Pacer with it's bungee-sprung gear. Your point is incorrect regarding the Cherokee as it was not yet invented, so Cessna's 170 was not yet competing with it. When the Cherokee came out, it still never had the rugged simplicity of the Witman gear, and it never overtook the Cessna 170/172 series which went on to become the all-time production king of the light plane industry...with it's spring gear. (The much-later tube gear was not a condemnation of the spring, but an improvement in weight.) So, I believe the comment that the spring-gear was a design-deficiency to accomodate cost savings is not valid. It's cost savings was a bonus to a great design, and Stinson couldn't change their type certificate and Piper couldn't buy the production license. (In fact, Piper actually bought out Stinson and basically shut them down after converting the Twin-Stinson to all metal covering and naming it the Apache.)
Anyway, I've found that the conversion-to-180-gear folks fall into two basic camps.
Camp One are the folks who don't like/haven't adjusted to the spring rates of the Witman gear. I'm intrigued by this group because the first 170 I flew was an A-model owned by a highly experienced co-worker who'd owned it for over 22 years and he complained about the gear as he checked me out in it preparatory to my picking up N146YS. He really didn't like the "bounciness" of the gear. After our check out flight, he remarked how I didn't seem to fight it like he did. I attribute that to having learned taildraggers in C-120's and 140's in my youth while flying pipeline patrols. (You might not be able to teach an old dog new tricks....but you'll have hell breaking him of old ones!)
I believe that, just like my buddy, after some competent flight instruction from someone who teaches a "light touch" technique, most folks will find the original gear to be a great landing gear. (I've got to admit tho', like a drop-dead-gorgeous girlfriend, ...I never really trust her. And also like that DDG girlfriend, I find a light, easy touch works better at encouraging desired behaviour than a heavy hand of "control.")
Camp Two is made up of the folks who use their 170's as work horses in rough terrain. Their desire is to have a gear that isn't so obviously under-equipped to handle heavy loads in unimproved areas, and to get more prop-clearance from the rocks and gravel. Personally, I think this is a better reason for conversion.
In fairness I should mention that there were three different spring gears on the various 170's. The first rag-wing airplane had PN 0441138. That spring-rate was changed with the 170A's to PN 0441138-3, which continued all the way thru SN 19218. Starting at SN 19219 thru the rest of A-model production, and up to B-model SN 25611, PN 0541114 was used. All those were interchangeable left/right, and they were considerably more "springy" than the next landing gear, which started at B-model SN25612 and is also called the "lady legs" because of a narrower "ankle" just above the axle. They also were no longer interchangeable left/right. This last spring-gear is definitely more predictable than any of the earlier ones, but that is not to say the earlier ones are unmanageable. They are just different. Try to think of them all as the raison de entre' for getting a taildragger instead of one of those "Land-O'Matic's"
that came later on.Bela, there were no "higher gross weights" later on. There were some changes in empty weights, however, that did cause Cessna to look into spring-rate changes. The airplane definitely lands better when it's heavier than it does when light on an early gear.
Jake, maybe it is your technique. The book (Owner's Manual) recommends a "tail low" takeoff. Here's how I teach the technique for takeoff.
During preflight, place the trim wheel in a position that will streamline the trim tab with the elevator. Note that position of your trim wheel for the future. (And by the way, it should be in the middle of the takeoff position placard. If it's not, then have your mechanic calibrate it by repositioning it within the trim wheel cover on it's positon with the wheel's indexing grooves. Then make certain that full travel of the tab is in accordance with the specs.)
Line up with the runway, hold the yoke fully back and smoothly apply full power, taking note that correct static rpm is achieved. (approx 2230). Use brakes early on, and then rudder-only as it becomes effective, to maintain runway alignment.
As the airplane accelerates and the rudder becomes effective, the elevator is also becoming effective, so nuetralize the yoke in pitch to it's elevator-nuetral position. (This roughly places your hand even with the doorpost. Check this out on the ground. Look back at your elevator counterweights, and position them faired in alignment with the leading edge of the horizontal stabilizer. Then look at your yoke position and memorize that position for future takeoffs.) During the takeoff roll, maintain that position until the relative wind no longer requires you to hold the yoke in that position (In other words, pay attention to the effort you make to hold the elevator nuetral. In a moment you'll realize as the relative wind has increased due to acceleration, that you have relaxed the pressure on the yoke and the relative wind is what is holding the elevator nuetral.) This "free-flying" nuetral elevator will now allow the relative wind to lift the tailwheel off the ground. (The actual weight of the elevator falling against the relative wind, will cause sufficient lift of the horizontal to bring the tail up, and the nose down, so that the airplane is now running along on it's main wheels only.)
As the airplane further accelerates you'll notice the nose will begin to descend lower relative to the horizon. At this point apply light back-pressure to the yoke, and the airplane will gently lift itself off the ground very nicely, thank you.
And when it come back to doing a wheel-landing,...that tail-low position is also the exact same position you want to achieve just as your wheels roll onto the runway. Then all that's necessary is to push the yoke forward to increase weight upon the mains, and ....voila! A wheel landing!
Back to the tail low position, ...if you continue to hold the yoke back against ever-increasing pressure (against gravity due to decreasing relative wind) eventually the tailwheel will touch the ground and ...voila! A three-point. (Little secret: When light, the B-model will land with 30-degrees flaps better than it will with full flaps.)
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N170BP
- Posts: 552
- Joined: Mon Jul 22, 2002 7:24 pm
>Bela, there were no "higher gross weights" later on. There were some >changes in empty weights, however, that did cause Cessna to look into >spring-rate changes. The airplane definitely lands better when it's >heavier than it does when light on an early gear.
Sorry, should have specified I was talking about the 180/185 series,
which did get gross weight increases in the later years.
Bela P. Havasreti
'54 C-170B N170BP
Sorry, should have specified I was talking about the 180/185 series,
which did get gross weight increases in the later years.
Bela P. Havasreti
'54 C-170B N170BP
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GAHorn
- Posts: 21290
- Joined: Fri Apr 12, 2002 8:45 pm
Quite right, Bela!
Here's an example of how despondent I get with these landing gear conversion questions. I've presently got an email I've not yet answered. It is from a member (who may actually be reading this and will thereby find out why he's not yet been provided an answer) who wrote to me a month or so ago, when I was out of town with my father's medical condition. (After I returned home, I started getting caught up on emails rec'd during that period.) He has an airplane that's already been converted to a different gear, and he's unhappy with it. It lands too stiff now, in his opinion. He's become suspicious that the "180" gear he's got might be a different part number than what his A&P thinks should be a 180 gear. (But his A&P doesn't know how to properly identify a 180 gear...he just doesn't think the one installed is one.) He wrote me asking me the differences between the gear that came off his airplane (without telling me which sn airplane he's got, or whether it's removed gear was original) and the presently installed gear (which he has no part numbers for, or any accurate measurements for.)
This sort of request can take days if not weeks of time researching and calling in favors from suppliers and mfr's to get the measurements in length, width, thickness at various points, of all the 170 gears AND all the 180 and 185 gears that might possibly have been installed on his airplane, (and done so without proper documentation I might add. There are several different thicknesses of several different 180 gears, and there are at least two "heavy duty" landing gears which can be used on 180s and 185's. (See how challenging this can become?) I'm not sure how researching 180/185 landing gear legs, in order to document an illegal or improper installation, pertains to 170's as a type. Anyway, just thought I'd pass along how this subject gets to be a bit of a "challenge" for me.) (Please don't ask me to be fully informed about 180/185's. One might better ask their group if you want to know details about their model, please.)
Now I don't want to discourage anyone from contacting me and asking me to perform my volunteer-job duty in helping them maintain their 170. But somehow it just seems to stretch my imagination a bit to ask me to do the homework and legwork for an owner and an A&P who didn't do their own,...on a mod that's unapproved by the type certificate holder.... and that was never intended on our type-club airplanes.
The best answer I can offer in such cases is,...don't convert. Find the correct gear and put it back on. Cessna usually knew what they were doing. My 2 cents.
Here's an example of how despondent I get with these landing gear conversion questions. I've presently got an email I've not yet answered. It is from a member (who may actually be reading this and will thereby find out why he's not yet been provided an answer) who wrote to me a month or so ago, when I was out of town with my father's medical condition. (After I returned home, I started getting caught up on emails rec'd during that period.) He has an airplane that's already been converted to a different gear, and he's unhappy with it. It lands too stiff now, in his opinion. He's become suspicious that the "180" gear he's got might be a different part number than what his A&P thinks should be a 180 gear. (But his A&P doesn't know how to properly identify a 180 gear...he just doesn't think the one installed is one.)
He wrote me asking me the differences between the gear that came off his airplane (without telling me which sn airplane he's got, or whether it's removed gear was original) and the presently installed gear (which he has no part numbers for, or any accurate measurements for.)This sort of request can take days if not weeks of time researching and calling in favors from suppliers and mfr's to get the measurements in length, width, thickness at various points, of all the 170 gears AND all the 180 and 185 gears that might possibly have been installed on his airplane, (and done so without proper documentation I might add. There are several different thicknesses of several different 180 gears, and there are at least two "heavy duty" landing gears which can be used on 180s and 185's. (See how challenging this can become?) I'm not sure how researching 180/185 landing gear legs, in order to document an illegal or improper installation, pertains to 170's as a type. Anyway, just thought I'd pass along how this subject gets to be a bit of a "challenge" for me.) (Please don't ask me to be fully informed about 180/185's. One might better ask their group if you want to know details about their model, please.)
Now I don't want to discourage anyone from contacting me and asking me to perform my volunteer-job duty in helping them maintain their 170. But somehow it just seems to stretch my imagination a bit to ask me to do the homework and legwork for an owner and an A&P who didn't do their own,...on a mod that's unapproved by the type certificate holder.... and that was never intended on our type-club airplanes.
The best answer I can offer in such cases is,...don't convert. Find the correct gear and put it back on. Cessna usually knew what they were doing. My 2 cents.
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R COLLINS
- Posts: 113
- Joined: Mon Nov 04, 2002 9:23 pm
Some thing else you might check is tire pressure. An over-inflated tire will have less sidewall flex than desired causing the gear to feel stiffer and an under-inflated tire will make it feel mushier. That may be part of the reason the the guys flying with 180 gear and 600x6 tires complain about the stiffness as opposed to those with 180 gear and 850x6 tires. Personally I have only flown with stock gear, tires and wheels so I'm learning alot just reading what others have written too! Randal
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jake boyd
- Posts: 9
- Joined: Mon Jun 17, 2002 4:03 am
Thanks Eric for the directions to Concrete. I'll try to get there.
Thanks gahorn for the tips on the stabilizer and trim and take off lesson. It turns out that my trim was off about 1/2 of the takeoff range and I was taking off with it set a bit nose down. Fixed that and used your other techniques and it helped a bunch. Thanks again. Not quite like flying an L1011 but the houses still get smaller and bigger. I have had my 170 since 1995 but most of my flying was off grass and now it is mostly off pavement and my errors were showing. Grass is so forgiving!!
Jake
Thanks gahorn for the tips on the stabilizer and trim and take off lesson. It turns out that my trim was off about 1/2 of the takeoff range and I was taking off with it set a bit nose down. Fixed that and used your other techniques and it helped a bunch. Thanks again. Not quite like flying an L1011 but the houses still get smaller and bigger. I have had my 170 since 1995 but most of my flying was off grass and now it is mostly off pavement and my errors were showing. Grass is so forgiving!!
Jake
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