The International Cessna^® 170 Association

For all that have never seen a wheel axle break on a 170, it is not pretty. I had the left axle break while taxing in to the tie down area at Smiley Creek Idaho on Thursday. No harm to any person, but it took out a new hartzell prop, engine tear down in store, and broken tail spring from the follow up impact from the prop strike. Unsure about the gearbox at this time. Just be aware they can and do break. And the old saying that it's not over until it's tied down is entirely true. Many thanks to the Smiley Creek residents for their assistance in getting the airplane off the runway and helping us get things sorted out.

Which style axles? How did they fail?

Sorry to hear that.

It was the "improved" aluminum axle. Needless to say, it will be getting steel soon enough. My guess is fatigue, there was no indication that the axle had a crack in it. The break was very clean. But, you can fix airplanes, people are much harder to fix. I'm just glad we weren't landing when it happened.

The solid axle broke? This is the first I have heard of a solid one breaking, not that I am an autority on the subject. Has anyone else run into this?

He didn't say it was a "solid" axle. He said it was an "improved" axle. There were two hollow axles: The original, and the "improved". Both are at risk of breaking.

The solid aluminum axle (also known as the "ski" axle) is the minimum recommended for the 170. I haven't actually seen one that has broken but like anything, I suppose it can be damaged/cracked and subsequently will break.
The hollow steel axle is also good.... according to most, it is the strongest of all, but it is also subject to rust/corrosion, especially at the mainspring interface and they are known to develop cracks at the bolt holes.
In other words, all axles should be regularly disassembled and inspected along with their attaching hardware. Ten years is probably good in most environments, and annually in ski, seacoast, and floatplane operations. The bolt holes in the lower mainsprings should also be inspected for cracks.

AN hardware is standard, and NAS is best, for attachment.

Well said George. I would recommend inspecting at every annual. And pulling for replacement at some point no matter what axle you are riding. It's a much cheaper route than filing an insurance claim, and munching a 25 hr prop. Not to mention being without your toy for a long period of time. I learned the hard way. I'll be going to the hollow steel axle and watching carefully over the years.

Is there the possibility that this unfortunate airplane was ever equipped with and flown on skis?

gahorn wrote:He didn't say it was a "solid" axle. He said it was an "improved" axle. There were two hollow axles: The original, and the "improved". Both are at risk of breaking.

The solid aluminum axle (also known as the "ski" axle) is the minimum recommended for the 170. I haven't actually seen one that has broken but like anything, I suppose it can be damaged/cracked and subsequently will break.
The hollow steel axle is also good.... according to most, it is the strongest of all, but it is also subject to rust/corrosion, especially at the mainspring interface and they are known to develop cracks at the bolt holes.
In other words, all axles should be regularly disassembled and inspected along with their attaching hardware. Ten years is probably good in most environments, and annually in ski, seacoast, and floatplane operations. The bolt holes in the lower mainsprings should also be inspected for cracks.

AN hardware is standard, and NAS is best, for attachment.

I don't think floats would be hard on Axels at all........

Only when the airplane is taken back and forth between the two types of gear. (heh-heh)
Thanks.

gahorn wrote:Only when the airplane is taken back and forth between the two types of gear. (heh-heh)
Thanks.

I guess you could use the gear leg and axle as an anchor that ought to get the corrosion going