Gear leg identification

[AWilson]

Nice info! I didn’t know Cessna responds to technical inquiries on these old birds. Do they provide drawings if it is a part they don’t make anymore? Which is most of them.
Thanks!

[AWilson]

I am now very confident these are 140 legs. But im considering just keeping them seeing as how they’re dimensionally the same except for the holes and otherwise in good condition.
What do you guys think?

No big deal, keep them on my 170. Its just 2 holes.
Or
Change them out asap and don’t fly till I do! They removed the holes for a reason.

[n2582d]

Nice info! I didn’t know Cessna responds to technical inquiries on these old birds. Do they provide drawings if it is a part they don’t make anymore? Which is most of them.
Thanks!

Yes, for a price.

I am now very confident these are 140 legs. But im considering just keeping them seeing as how they’re dimensionally the same except for the holes and otherwise in good condition.
What do you guys think?

No big deal, keep them on my 170. Its just 2 holes.

Actually, it's just one additional hole as they kept one hole to attach the brake line retaining clip.

Or
Change them out asap and don’t fly till I do! They removed the holes for a reason.

The reason one hole was removed is not for any safety concern, it was because the step for the C-170 was no longer mounted on the gear leg as it was on the C-120/140 and thus the additional hole was superfluous.

I think the answer depends on the type of flying you're doing. If you're doing a lot of off airport flying or using skis, I'd recommend changing the gear. Otherwise, I'd hang onto the gear and follow Cessna's Supplemental Inspection Document (SID) 32-13-01.

Gear Inspection.pdf

(I'm kind of surprised that in this section of the SID Cessna doesn't call for more than a visual inspection -- like MPI or eddy current). Be sure your mechanic is aware of the danger of hydrogen embrittlement associated with paint strippers. There are some strippers where this is not a factor so, if you use paint stripper, chose wisely.

Regarding the legality of flying with C-120/140 gear, on the one hand it's been safely flying on this gear for decades and has apparently been certified to be safe by IA's over all these years. But, if it were my plane, I'd try and get the gear approved with a field approval/337 form. (This is assuming your IA feels this is a major alteration. He may determine that this is a minor alteration which would only require a logbook entry). Back in 2004 AC43-210 had the following section which has been deleted in later revisions. I think it's still applicable.

105. What are the two ways that an ASI may approve an alteration or repair?
a. Examination of data only (one aircraft). ...
b. Physical inspection, demonstration, and testing (one aircraft). This field approval is typically used when:
(1) A major alteration or major repair has been made to the aircraft by a person or persons unknown and no substantiating approved data or maintenance record exists; or
NOTE: When an alteration or repair is made by person(s) unknown and without substantiating data, the mechanic or repair station may correct this discrepancy by creating a data package based on the installation and equipment already installed in the aircraft and submitting it to the ASI for approval. When it is approved, the ASI may inspect the aircraft. If the data package is acceptable, the ASI will sign in block 3 of FAA
Form 337, approving the installation or repair based on his or her inspection or testing of the alteration or repair. If an alteration or repair is made that can be approved by a physical inspection or demonstration and testing, rather than just data, or if creating a data package is not practical, the ASI will perform the inspection and then sign off in block 3 of FAA Form 337.

Include SID 32-13-01 and SLN 67 and/or SL63-14 in the Instructions for Continued Airworthiness (ICA).

As critical to the safety of your gear are the axles. Do you have hollow aluminum, solid aluminum, or steel axles? If they are hollow aluminum replace them with solid aluminum or steel axles. A lot has been written here regarding this subject as a quick search will reveal.

[Bruce Fenstermacher]

For the forum thread I wanted to document that Allen and I had a conversation over the phone. I told him I wasn't sure I'd have to remove a gear leg that had two holes as his has just because it had two holes.

Here is why.

The 170 IPC says the 170 used 0441138 gear, which happens to be the same at the 140. The 170A IPC says that the 170A used 0441138-3 from serial 18003 to 19219) and the 054414 Serial 19220 after.

Hmm but the A model serial numbers where 18730 and 20266. Why would the A model IPC list include serials for the 170? Was this a mistake? Or is the 170 IPC missing a -3 in that part number listing a mistake? It is clear at some point the A model had the -3 gear but not clear when. Did the 170 have gear with two holes? We will never know but we might get a good idea if we start taking a pole of 170 owners asking how many have gear with two holes. Cessna's letter to Gary says the -3 gear is the same as the original minus the unused hole. I wouldn't be surprise to find more than one 170 running gear with 2 holes. Just something else I have to remember to look for when I look over 170s I come across.

Allen say's 140 gear have been known to break. Hmm do we really know them to break and if they did break, did they break at a drilled hole? What was the cause of the break if they break?

I told Allen I don't know that 140 gear are prone to break. I do know that some 15-20 years ago there was some Cessna gear that broke but that investigation seem to indicate those gear that broke, broke on a stress line caused by corrosion due to a step being clamped to the gear. At that time there was thought an AD might be looming but nothing has come of it.

I told Allen I wouldn't fault him if he changed the gear out or if he kept them with the information we have at the moment.

[brianm]

Data point: N2669V, serial 18179, has two-hole gear legs. Unfortunately I can't say for certain that they are original. The logbooks are... hazy for certain periods of its life.

[Bruce Fenstermacher]

Thanks Brian, that is exactly what we need. If Brians '48 came from with these gear legs, we could be pretty certain the 173 170s produced befor his also had them.

Anyone with 2 holes , not little indents, drilled in their gear legs please check in with model and serial. Maybe we can get some idea how many are out there.

[n2582d]

... Or is the 170 IPC missing a -3 in that part number listing a mistake? ...

I don't think an illustration carries much weight but, for what it's worth, the C-170 IPC illustration only shows the one hole for the brake line clip. If this drawing is correct, then it would make sense that Cessna inadvertently omitted the -3.

Bill writes that he has two holes in one gear and one hole in the other:

Not sure about this but isnt the early 170 gear and the 120 140 gear the same except for the step holes. My 170 has two holes in one gear just like a 140 and one hole in the other gear. when I removed my gear for testing the two gear legs matched perfectly except that the one leg had an extra hole for a step like was used on the 140. Dont know if Cessna installed the gear with two holes or not as there are no log book entries indicating otherwise and no entries that would indicate any gearbox repairs. Seems to me that hard landings and landings on rough fields would be the primary reason for cracking of otherwise sound gear legs. Bill K

Here's another data point: BAS 0441138 legs for sale One hole yet labeled (or mislabeled?) as 0441138. From a 1948 C-170, s/n 18399.

...Allen say's 140 gear have been known to break. Hmm do we really know them to break and if they did break, did they break at a drilled hole? What was the cause of the break if they break?

I told Allen I don't know that 140 gear are prone to break. ...

The Service Bulletin calls for replacing the original rivet with a steel bolt so my thought was that maybe it was dissimilar metal corrosion that was causing the cracking issue. But here's some other ideas for why these cracks are forming. From the Summer 2016 issue of the 120/140 Association's periodical:

399-2016-Summer-Newsletter.pdf

[Bruce Fenstermacher]

From the 120/140 newsletter, it seems they've seen them crack/break at the bottom hole. That of course is the single hole the 044138-3 has. My 170A had a set of single hole 044138-3 gear. It was ground looped twice ripping the gear box out. It was repaired twice when gear boxs where available and there were more people doing such things. It's still flying with those gear best I know. And those gear spent 71 years flying with Goodyear crosswind gear on them. Maybe that's what saved them.

N3958V is serial 18277 so the number of possible '48 with 044138 gear from the factory has risen to at least 275.

[n2582d]

Here are some more data points. The ‘48 Owners Manual has this photo. Could be my imagination but it looks like two holes on the leg.

IMG_1282.jpeg

N4165V, s/n 18498, shows two holes in each leg.

IMG_1281.jpeg

Here’s an interesting NTSB report that shows a gear leg on a ‘48 which broke half way up the leg. No mention of whether the fracture occurred at a hole in the leg. Left gear looks like it has a convex arch — could be lady leg or 180 gear.

IMG_1283.png

[AWilson]

I located a set of straight legs from a forum member. No holes, 2 dimples. So they’re definitely 170 legs. Me and my mechanic are putting them in tomorrow. I appreciate all the comments especially my conversation with Bruce.
I will post pictures when finished.

[AWilson]

Got them in. Here are some pictures.