C5 Engine Noise

Sorry Paddy , allow me just 1 guess .. I couldn't resist.

I leave you to the capable advice of the many experts on the real subject.

Ive heard that, too.

I believe that its something about the ducted fan that produces the note,

not unlike that of prop planes.

Most fan jets have had a lot of attention paid to their design to minimize this,

perhaps at the cost of efficiency / cost?

A mil transport wouldnt be as concerned re. noise, so

they could relax this requirement.

Ive also heard similar sounds coming from the fans of the 767,

although a bit softer.

Remember the L-1011? What a buzz monster. Then when they throttled back the buzz would go into a lope. I was always waiting for the engines to fall off. Might be the gear type fuel pumps as they turn at 10,000 RPM or something ridiculous like that. I know a designer of aircraft fuel pumps and the 'noise' is a significant factor of super special design.

PetroPower just read your catch phraze. About 15 years ago a friend went on a shopping trip to another city. As she didn't want to buy another bag at the other end after a successful trip, so she decided to take a empty suitcase on the flight. When she got to the other airport she was detained by security for several hours as they thought she was a drug mule ( empty suitcase). Especially as she had several thousand dollars in cash. He he. After the initial shock, she thought it was a great joke and she had'nt had that much fun in ages.

They are turbo fans. turbine driven ducted fans.