Backcountry Pilot • Help on rigging for Aero 3000 skis

Help on rigging for Aero 3000 skis

Two of the best inventions ever, skis and airplanes, together.
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Tue Nov 21, 2017 6:29 am

Re: Help on rigging for Aero 3000 skis

If you review the Aero installation drawings associated with the STC(Dwg. No. 3-105) you will see that the hollow steel axles (all of the steel axles are hollow) are listed as required by specific part number, number 1441003-1, there are sources other than Cessna. That part number is the 180/185 axle but not what Cessna calls a "ski" axle for the 180/185. Cessna "ski" axles for the 180/185 have a clamp which fits around the axle mounting bolts on the gear leg and uses a total of eight bolts. The collar that you see is where the seal rides and also what the wheel bearing or ski goes against so that you can tighten the nut. The installation drawing clearly shows the collar in place on the axle with the ski up against it. If you don't have the installation drawings you should get them from Aero Ski.

Tim

for what it is worth the solid aluminum axles that you have are the Cessna "ski" axle for the 170, just not approved for the Aero Ski installation per the STC.

edited for note about collar
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Tue Nov 21, 2017 12:06 pm

Re: Help on rigging for Aero 3000 skis

I’d prefer the steel axles in any case.

MTV
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Tue Nov 21, 2017 2:02 pm

Re: Help on rigging for Aero 3000 skis

Close example of wheel axle strength vs. skis axle strength....

C3000A, STC up 3000 LBS gross weight approximately:

On retractable hydraulic skis, the wheel axle is hollow steel. And the "Ski" axle is SOLID forged and machined steel. Strong enough to lift a battleship.. This was not on accident, skis axles required much more strength than a normal aircraft wheel axle. Be careful on selecting hardware. Wheel vs. ski flying required much different engineering.
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Tue Nov 21, 2017 4:21 pm

Re: Help on rigging for Aero 3000 skis

8GCBC wrote:Close example of wheel axle strength vs. skis axle strength....

C3000A, STC up 3000 LBS gross weight approximately:

On retractable hydraulic skis, the wheel axle is hollow steel. And the "Ski" axle is SOLID forged and machined steel. Strong enough to lift a battleship.. This was not on accident, skis axles required much more strength than a normal aircraft wheel axle. Be careful on selecting hardware. Wheel vs. ski flying required much different engineering.
Image


This is a very different setup than he’s dealing with on straight skis. His skis mount in place of the main wheels, and the standard axles on these Cessnas are hollow steel, not solid steel.

Those axles you’ve circled actually experience fewer loads than the main gear axles do. Main gear mounted skis support the entire weight of the plane, including landing and takeoff loads, side loads, twisting loads, etc.

The axles you illustrate do not experience landing and takeoff loads, only side loads and twisting loads. A very different problem.

Anyway, you’re comparing apples to oranges.

MTV
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Tue Nov 21, 2017 6:25 pm

Re: Help on rigging for Aero 3000 skis

mtv wrote:
8GCBC wrote:Close example of wheel axle strength vs. skis axle strength....

C3000A, STC up 3000 LBS gross weight approximately:

On retractable hydraulic skis, the wheel axle is hollow steel. And the "Ski" axle is SOLID forged and machined steel. Strong enough to lift a battleship.. This was not on accident, skis axles required much more strength than a normal aircraft wheel axle. Be careful on selecting hardware. Wheel vs. ski flying required much different engineering.
Image


This is a very different setup than he’s dealing with on straight skis. His skis mount in place of the main wheels, and the standard axles on these Cessnas are hollow steel, not solid steel.

Those axles you’ve circled actually experience fewer loads than the main gear axles do. Main gear mounted skis support the entire weight of the plane, including landing and takeoff loads, side loads, twisting loads, etc.

The axles you illustrate do not experience landing and takeoff loads, only side loads and twisting loads. A very different problem.

Anyway, you’re comparing apples to oranges.

MTV


Read "Example" not "Comparison". Anyway, I simply don't agree that the loads are much different. Just an example of mine, that's all.
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Tue Nov 21, 2017 6:56 pm

Re: Help on rigging for Aero 3000 skis

MTV has it right, with Wipline (Fluidyne Airglide skis) the weight of the aircraft including landing loads are supported by the tire setting on the ski. The axle supports the ski in flight.

Tim
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Tue Nov 21, 2017 7:15 pm

Re: Help on rigging for Aero 3000 skis

bat443 wrote:MTV has it right, with Wipline (Fluidyne Airglide skis) the weight of the aircraft including landing loads are supported by the tire setting on the ski. The axle supports the ski in flight.

Tim


Agreed. Completely different set up. Again, "example" was to show the axles on skis are a high stress point and do have a proven tendency to fail more so than wheel (only) axles. Manufacturers have upgraded in several instances.

Theoretically speaking: My MLG will completely shear at the cantilevered/fuselage mount before the axle.
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Tue Nov 21, 2017 7:52 pm

Re: Help on rigging for Aero 3000 skis

Yup understand that there are a lot of forces at play when it comes to skis. Also wondering/figure out if I’m going to have to modify the axles. I’m probably getting ahead of myself as I have yet to sit down with my IA, we’ve just casually chatted about the process in general. Just trying to wrap my head around it all.

I appreciate all that have commented and reached out to educate me.

Thank you.


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Tue Nov 21, 2017 9:16 pm

Re: Help on rigging for Aero 3000 skis

I will cut to the chase for you. To be in compliance with the Aero Ski STC for the M3000 skis you have you have to change to the approved axle part number. Per the installation drawing for the skis you DO NOT modify the listed part number axle. I reviewed the installation drawing before making my prior post.

Tim A&P IA, Cessna 170B, 180H, and Aero Ski M3000 owner
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Tue Nov 21, 2017 9:43 pm

Re: Help on rigging for Aero 3000 skis

A couple of things you will probably run into during the installation are getting all the right type and length bolts if you end up replacing the axels. Since you are replacing the axels you might want to consider checking the gear alignment which is a nice project in it's self. Save putting in the new bolts until you are completely satisfied with the Axel and shim arrangement because once you torque down the bolts they are sightly bent if any shims were needed and aren't suppose to be reused although I'm sure many guys do. The number of shims needed will affect the length of the new bolts so I would hold off buying the new ones until you sure about the length as they are kind of expensive. NAS bolts are recommended for ski application and Glacier Aircraft Parts in Palmer has a pretty good selection in stock.

I replaced the the bottoms on my Landis Skis and they overhang the sides an inch or so and I think I am going to trim the outsides of each ski to the original width and chamfer the edge because the 170 gear has a lot of camber with no weight on it and I had the edge catch pretty good once when landing in a cross wind. It sounded like I ripped the landing gear out but my buddy said all Cessnas sound like than when landing on skis! :D

I debated back and forth on bungees vs springs and mine already had the Atlee Dodge springs but they are technically not approved for the Landis skis although Atlee is waiting for approval for the 170. They did say to pay close attention to the end of the springs where they hook to the cables or brackets as any wear to the spring in that area can and has caused spring failure. I personally think the springs are a little better but nothing wrong with the bugles either.
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Tue Nov 21, 2017 10:09 pm

Re: Help on rigging for Aero 3000 skis

...NAS bolts are recommended for ski application and Glacier Aircraft Parts in Palmer has a pretty good selection in stock...
+1
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Wed Nov 22, 2017 4:43 am

Re: Help on rigging for Aero 3000 skis

Reading all this is giving me ski envy!

Are you going to be flying out of PABV or are you moving to a nearby lake?


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Wed Nov 22, 2017 4:16 pm

Help on rigging for Aero 3000 skis

Probably keep at PABV for now until I can safely assess distance and performance. I keep eyeing Fire Lake, but don’t like the wires or hills in the north end.

You got skis?


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Last edited by Wldlndfirefghtr on Wed Nov 22, 2017 11:27 pm, edited 1 time in total.
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Wed Nov 22, 2017 5:25 pm

Re: Help on rigging for Aero 3000 skis

I don’t have skis on my 170 and would need to sink some cash into it to get it ready. (Ski kit, 180 gear, solid axles)

Last year I flew my Dad’s Maule on skis out of Lake Hood and enjoyed it. Not sure if we’ll put it on skis again this year.


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Wed Nov 22, 2017 6:36 pm

Re: Help on rigging for Aero 3000 skis

Mark,

I picked up a set from a coworker for a really good price and I am learning lots, and they aren’t even on yet! Lots of great info from knowledgeable folks! Hoping to give it a go this year.


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Sun Nov 26, 2017 12:14 am

Re: Help on rigging for Aero 3000 skis

Well got the skis put together with the help (he did most of the work [emoji3]) from my buddy. I think they turned out fantastic! Can’t wait to try them.

Next step rigging and installation.



ImageImageImageImage


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Sun Nov 26, 2017 12:32 am

Re: Help on rigging for Aero 3000 skis

Very well done. Go fly and have some ski fun.

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Sun Nov 26, 2017 7:58 am

Re: Help on rigging for Aero 3000 skis

Yup, nicely done. I think you’ll find that a good Alaska IA will know all the issues and get them installed nicely.

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Sun Nov 26, 2017 3:43 pm

Re: Help on rigging for Aero 3000 skis

Looking good! There is one practical limitation I have found for the extra plastic width: if you ever perform your own wheel/ski changeovers by jacking on the gear leg, the plastic can potentially be wide enough on the inside of the ski to rake the jack/ cribbing/ whatnot as the gear goes in the air and the camber relaxes. The other time this matters is if you or your mechanic use the Aero ski dollies, which are made to go in that lower [typo fixed] hole on the pedestal and let you wheel the plane around when on skis. My plastic is at the limit for these things. I’d gladly measure it for you, but I’m stranded on Adak until Alaska Airlines resumes service. Off the top of my head I think my plastic overhang is either 2” or 1.75”. Yours looks like it may be just a tad more?
-DP
Last edited by denalipilot on Mon Nov 27, 2017 12:21 am, edited 1 time in total.
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Sun Nov 26, 2017 7:59 pm

Re: Help on rigging for Aero 3000 skis

denalipilot wrote:. I’d gladly measure it for you, but I’m stranded on Adak until Alaska Airlines resumes service. DP


Oh, man, who’d you piss off to wind up in Adak? :shock: :lol:

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