The International Cessna^® 170 Association

Just curious. Why do I see braces/struts above the dash board/behind the windshield in some 170 videos? Is this a modification, and for what purpose?

This is a fuselage strengthening modification for aircraft that are used on floats and skies.

Ed is right.

The struts are known as V-Braces and are used to stiffen up the fuselage in the cockpit area to deal with the added stress of rough field, floats, and ski operations.

Thanks for the answer. Is this modification precautionary, or is there slight inherent weakness in the 170 cabin design?

I don't think its precautionary or indicative of a design weakness, I think it just reflects a modification for extra heavy duty service.

Everything has a weak spot somewhere and when that is strengthened you move it somewhere else. Although over all might be stronger. Another example on a Cessna, is p-ponk.

Just remember that the goal of aeronautical engineers is to make every part as weak as possible.

If planes were built like locomotives, they would never fly.

The pounding of waves/water really stresses (downward) the engine and it's mount, which transfers to the firewall/cabin area/windshield. The V-Brace stiffens that area up to avoid cracks. (not something the ordinary 170 will suffer even tho' 60-plus years of operations.)

V-braces are still available as a special order from F. Atlee Dodge. They require a field approval to be installed in a 170. There are other good forum threads on the topic.

Personally, I was surprised at how much a V-brace stiffened the fuselage solely from the evidence of eliminating the windshield squeak. The difference was amazing.

I run floats, skis, and bush gear (but seldom all at the same time). If my bird was an airport-to-airport flier, the V-brace would not be necessary.

-S