PHOTO: Skunk Works reveals composite cargo X-plane

The most important thing about Skunk Works' latest X-plane -- the Advanced Composite Cargo Aircraft (ACCA) -- is its raw material. The fact that ACCA is a cargo aircraft is secondary. The modified Fairchild Dornier 328Jet is really a flying laboratory for a new type of out-of-autoclave composite material, which is specifically called MTM45-1. 

Unlike other composites resins, MTM45-1 is not cured in an autoclave. Such hulking, nitrogen-fueled chambers roast and pressurize lesser composite resins into material with the strength of hardened steel. MTM45-1, by contrast, can be cured at temperatures around 150-degrees F.

But there is an important catch. Even the strongest of today's out-of-autoclave composites  remain too weak to pass a key modern standard for aircraft certification called compression after impact strength. New out-of-autoclave resins that match the compression properties of autoclave-cured composites are still at least a decade away.

But that's all right with the ACCA program. The aircraft is, after all, an X-plane, or experimental aircraft. It should be a decade ahead of its time.

For more about ACCA, I am writing a full-length feature with the details about the program and related technologies. It will be published in Flight International's special preview issue for the Paris Air Show.