Cowlings are now composite (ie plastic) instead of aluminum. They are limited to 5 minutes of use in dry air to prevent the cowling from melting, flying apart, or getting into the engine and causing it to fly apart.
> Cowlings are now composite (ie plastic) instead of aluminum.
Um, no. Absolutely not “ie plastic”. Composite material in the case of aircraft means it’s made of two or more materials. In the case of modern aircraft, it often is carbon fiber, but can also mean fiberglass and Kevlar (aka aramid fibers).
A larger part is the epoxy, e.g., plastic. It being a composite would actually make it worse than just plastic under cyclic heating, because the epoxy and carbon fiber have different coefficients of thermal expansion.
Very likely no money was saved by Boeing, composites are almost always more expensive.
Maybe someone with aviation industry knowledge can reply, but my guess is adding a trivial timed shutoff would have triggered an elaborate FAA approval and certification process. That’s probably where the savings were.
The “savings” is entirely due to weight. More weight requires more fuel. The single biggest cost by a large margin in the life of a commercial airline jet is fuel. Increase fuel efficiency by even 1% and you save the airline industry billions.
I was thinking about weight, but the cowlings are pretty small compared to other parts of the plane where composite materials are used. So i'm not sure a single digit saving in pounds of fuel per hour or flight was a good tradeoff considering the risks associated with the alternative they went with.
But, like someone else said this here, I would love someone with knowledge about this to chime in.
Um, no. Absolutely not “ie plastic”. Composite material in the case of aircraft means it’s made of two or more materials. In the case of modern aircraft, it often is carbon fiber, but can also mean fiberglass and Kevlar (aka aramid fibers).