Warbird Information Exchange

I have seen photos of a zig-zag ,symmetrical, metal looking pattern in the top inside surface of certain jet fighters . What is it's use?
I was at the Topeka Airshow and went to the Combat Air Museum and a jet fighter on display in the museum had the pattern. I asked people in the hanger , who worked there, and nobody had a real good idea what it's used for. One said it could be an antenna and another said possibly for defogging the canopy. So what is it for? Lightning protection? I can't remember which aircraft was on display.

I believe it is an explosive cord to cut the canopy and create a clear path for the ejection seat to pass through.

If it has a zig zag pattern, then it's usually a type of det cord for shattering the canopy as has been mentioned, however there are some aircraft, usually older, that do have an antenna, but it's usually symmetrical and not zigzag.

That would be correct. Aircraft designed with thru-canopy ejection (mostly those equipped with Martin Baker seats) use a pattern of detonation chord to sever the canopy in a planned manner to allow the seat and occupant to safely leave the aircraft.

There are two methods primarily in use - canopy ejection and thru-canopy.

Canopy ejection is the primary method used by most US aircraft and is pretty self explanatory, but here's a really nice slo-mo of the ejection sequence of the T-38.

http://www.youtube.com/watch?v=oI4iPp-aUvc

Thru-canopy uses det-cord or other explosive to pre-shatter the canopy and allow the seat to eject directly out of the aircraft without harming the pilot. Martin-Baker is best known for this style

Here's a nice video of the original det-cord seat in operation -

http://www.youtube.com/watch?v=L0m6UEFaWvE

Unfortunately, video of the F-35 or Hawk system doesn't seem to be readily available online.\

The second youtube link has the pattern I was referring to at the 2:50 , 4;00 and 4;50 min. mark. I was a little hesitant to think it was detcord but it must be made in varying power to an application. Better to have a little bang close than auger in. Thanks for the info.

The term "det-cord" applies to the type of explosive. However, it comes with a lot of different fills and speeds, making it infinitely versatile. The type of det-cord used in thru-canopy ejection seats appears to either use a setup that directs the shockwave outward (when installed between the canopy frame and plexi) or in a shock-tube style application when overhead that uses the stress of the plexi itself and the sharp shockwave produced by a small amount of explosive inside a tube that will withstand the shock itself but will transmit the shock to the plexi, allowing it to be used in close proximity to the head of the pilot without causing any harm to them.

My T-28D had the rocket extraction system fitted and det-cord [sic] in the front canopy glass.

The rocket closely followed by the pilot went through the canopy...wild ride!