The International Cessna 170 Association

I was just looking at P.Ponk's website. Some pretty good information there regarding landing gear and gearbox construction,failures,& improvements. Check it out.

http://www.pponk.com

Eric

Speaking of other websites,how do we go about adding to the "links" page of this 170 Association site? Webmaster and/or moderator,are you in charge of that?
I'd like to add a link to the 180/185 site (http://www.skywagon.org),as well as to the 120/140 Club site (http://www.cessna120-140.org). These airplanes are our 170's big and little brothers,and these sites have some good information on them about both flying and maintaining Cessna taildraggers. If there's a Skyhawk site,as much as I hate to admit it, that should probably be included too.
I don't especially want to promote any commercial sites,but there are some (like the Ponk site I mentioned in the above post) that have some good,relevant information on them.

Eric

I think the P.Ponk website should be required reading. Learn a lot about the gear attachment. It didn't take me long to order the kit.
It seems like a bargin at $225.00
I am working on my boss's sons aircraft. He is learning to fly in the 170. It seemed like a pretty good insurance policy to beef up the gear attachments for a student pilot application. Plus after reading up on the various gear box ailments on the P.Ponk site, it seemed like a good place to take a look around on an unknown aircraft. I know I'll sleep better knowing that I was in there looking at it and installing the kit.
There are my thoughts. probly worth every cent you paid for it.(not even 2 cents!)

I was told that the Ponk kits are for flopping in short landings and don't help side loads.

From what Ponk sez on ths site,as the drawings of the gearbox and beefup kit installation,I think it IS designed for side loads,those that want to fold the gearleg under the airplane. Check out the information on Pon's site for yourself.

Eric

Having just installed the kit, I can't imagine where somebody came up with the idea that it doesn't take care of the sideloads. The kit is VERY stout. Adding 6 bolts in shear, to the original ONE bolt in tension is a great idea. That gear leg ain't going nowhere, nohow, notime.
There are my thoughts. Probly worth what you paid for it!

You are correct about the PeePonk mod being strong, too strong in my opinion. If you do pull a gear leg out with the ponk mod instaled you will scrap your fuselage.

Without the mod, YES, they do break out easier. but most can be repaired. Remember the gear box is also a part of the door post, there are no door post replacement parts.
When the gear is overstressed to failure with the mod installed, it vertually rips the flap handle out thru the bottom of the aircraft.
Omak aircraft salvage had 7, 170 fuselages before they went out of business, 5 of the 7 were scraped due to gear failures with the ponk mod installed.

One easy way to strengthen the gear attachment is to replace the original AN365-720 nut with the heavy version of AN363 all metal locknut.
The heavy AN363 takes an 11/16 wrench. It has an axial strength of 18,300 pounds and is 25% stronger than a AN365. You end up somewhere between the origional and P Ponk and the nut costs less than a buck.

n4517c wrote:One easy way to strengthen the gear attachment is to replace the original AN365-720 nut with the heavy version of AN363 all metal locknut.
The heavy AN363 takes an 11/16 wrench. It has an axial strength of 18,300 pounds and is 25% stronger than a AN365. You end up somewhere between the origional and P Ponk and the nut costs less than a buck.

How does a heavy version lock nut prevent the bolt that it is attached to from breaking? Koop

If you shear the bolt the gear is history. However, the common failure mode is to strip the thinner, weaker AN365 nut. The AN363 is threaded all the way to the top of the locking fingers, making it stronger.

4517C,that's a pretty good idea,beefs up the gear and only costs a buck! I Like it! After looking at Ponk's website information,it's a very logical improvement. I don't know enough about the different AN hardware available,I guess,I never would have thought of that. Was that your idea or did someone else pas it along to you? I wonder why Cessna didn't use the stronger nut to begin with? I'm sure gear-leg fold-under accidents occurred back in the old days,too.

Eric

I can't take credit for the idea. Maine Fish and Game has made that change on their 185 skiplanes. No failures since the switch.

n4517c wrote:If you shear the bolt the gear is history. However, the common failure mode is to strip the thinner, weaker AN365 nut. The AN363 is threaded all the way to the top of the locking fingers, making it stronger.

Thanks for the tip. I have purchased the P-Ponk kit and will be installing it soon. Wonder why they didn't supply me with the An363 nuts? Koop

I think I'll pass on the Ponk mod and just check my nuts I don't like the idea of destroying the fuse if I were to mess up. Plus my chances of loosing it on a side load are slight and slighter now with the Lyc that can get me off the ground quicker in a crosswind takeoff.

I had read somewhere that it was not uncommon, in a bad groundloop for the gearleg to come up thru the floor and pin the pilot in the wreckage. That was the basis for my decision to install the P.Ponk kit.
I gueess if it comes down to sacrificing the airframe for the safety of the pilot, the airframe has to go. Time to file an insurance claim and get another airplane.
I have not seen the results of a groudloop in a 170, can anyone confirm the chances of the gearleg actually entering the cockpit and doing damage to the pilot?
Also if you decide to install the larger nut, why not go with the NAS bolt.
It has a strength of 160,000 PSI vs 125,000 for the AN bolt.