At the end i finaly found the new FAA-instructions for ski plane rigging:

Se page 39 (and forward) at

http://rgl.faa.gov/Regulatory_and_Guida ... _13-2B.pdf

Noted that the FAA now recomend installation of 5/32 DUBBLE safety and crust-cutting cables, on aircrafts with ski limit load rating more than 1500 pounds.

Thats news! ( Or have I totaly missunderstod...) Standard in Sweden is still a single safety cable...

So what are You guys doing - follow the FAA recomendations, or....

I think the 1 is a safety for when you cut the bungee. Also if you loose the bungee on take off it will only allow your ski tip to go only so far down.
GT

The picture shows just a normal installation with ONE cable, and of course a bungee. FAA asking for TWO safety cables in the front and at the back of the skies. Right?

No, the FAA is not asking for two independant limit cables front and back.

MTV

But have You read the doc? Asking or recomend, for me its the same....

But of course its not a FAA-mandatory with two separate safety cables.

I started this post just to discussing the needness of two separate safety cables. What do You do think?

Yes, I have read the document, and no the FAA is not recommending (or asking or ???) in that document that you should be doubling up on the cables in ski installations. Maybe I'm not understanding your question.

MTV

See page 41!

TABLE 5-1. RECOMMENDED MINIMUM CABLE AND SHOCK CORD SIZES

Why are FAA talkning about "single safety cable" and "double safety cable" - and no "single cables" over 3000 pounds.

What that table says is the SKI limit load of greater than 3000 pounds should have double cables. That would imply an AIRPLANE of greater than 6000 pounds GW, I believe. That is bigger than a Beaver, and I'd think that double cables on a single engine Otter would be appropriate.

MTV

mtv wrote:What that table says is the SKI limit load of greater than 3000 pounds should have double cables. That would imply an AIRPLANE of greater than 6000 pounds GW, I believe. That is bigger than a Beaver, and I'd think that double cables on a single engine Otter would be appropriate.

MTV

Trying to remember how that works... with floats, isn't EACH float supposed to be buoyant enough to float the gross weight of the ship? So is there any carryover to ski designations? (yeah, I know, everything depends on the nature of the snow)

My 170 is equipped with Aero 3000's, but I'd hate to operate it on the floatation equivalent of just one of my skis, and I can't imagine operating a 6,000 lb aircraft on them

(Now I'm confusing myself... I know my plane is fun on snow though)

-DP

I believe that the ski limit loads are considered on the individual ski, worst case scenario. The reserve bouyancy required for floats is that each float must be capable of supporting at least 85% (if I recall correctly) of the total GW of the airplane. That's a buffer in the event that you flood one or more compartments on a float. I don't think you have to worry about flooding a compartment on a ski....

MTV

MTV
I beg to differ with you!!!!
I have flooded all the compartments on the ski on one side and it sank all the way until the wingtip gently touched the snow ontop of the ice that was on top of the water(overflow) that was on top of the ice on the lake!!!!
One ski, I don't care what the buoyancy rating is, will not hold up 1/2 of the aircraft when the compartments are flooded!
GT