Nearly Silent Flying Machines

FROM THE HOME HILL- Astute and loyal readers may remember that I had a post title that mentioned night sounds. Well, this is what was being referred to.

Every once in a rare while, I will hear a very quiet machine fly over at night. By rare, I mean that it has occurred twice. It happened again tonight. Since it's fresh on my memory, I shall attempt to describe it as well as theorize as to what it could possibly be.

First, allow me to set some precedents. I am a pilot and aviation enthusiast. When I speak of flying machines, I generally know my material quite well. The other thing I'd like to say is that I tend to look for rational rather than amazing or shocking explanations to the unknown.

Tonight at approximately midnight on Friday, 7 May 2010 I heard something fly over. As I have mentioned, this is something I've been listening for for quite a while. Tonight's event was not as dramatic as the first time I heard this sound. I walked up the stairs to my room and pulled the folding chair out and sat down at the computer. All the lights were off upstairs, and my monitor was the only light source. My windows were partly opened, and I could hear the low drone of night sounds from insects as a breeze casually blew in the window. As I was opening my browser (Google Chrome!) and loading all my favorite tabs, I became aware of a slowly growing sound. Through the acoustics of the sound reflection pattern off the ground outside, I knew immediately it was a flying vehicle. I will attempt to describe the sound.

The most prominent element was a sound like rushing air. There was a hint of a turbine engine, quite successfully muffled. As far as the loudness of it, it was not any louder than a strong wind rushing through the trees on the ridge that is about 1,500 feet from my window. In fact, that's the most similar sound I have heard.

The first time I heard it (unless it was an entirely different machine) was about this time last year. That time, though, was even more odd than tonight. Rather than just sounding like a well-silenced helicopter, the sound I heard then was strange and slightly hair-raising.

I was sitting in my quiet room with the windows open as they are now. Suddenly directly overhead outside I heard a massive roar of simply...air. The sound of something massive moving at probably 150-200 knots at I'd guess less than 1,000 feet AGL was right over my upstairs room. If a Boeing 777 had lost power to both engines and had flaps and gear extended and glided over my house, that would be very close to what I heard that night. In fact, that's what I thought it might have been. I moved to the window and strained all my senses to detect anything else. I may have imagined it, but a very low bass sort of vibration seemed to trail in the wake of the first initial sound, which lasted only about 3-4 seconds.

What could it have been?

I remember reading in a back issue of an aviation magazine (Smithsonian Air & Space, I believe) about a CIA project called Operation Mainstreet to tap communication lines running between the Viet Cong and their comrades elsewhere. To accomplish the mission, the CIA had to have a very, very quiet helicopter to insert the special forces without detection. From what I recall, they ended up modifying a pair of MD-500 helicopters. It ended up so silent that one American soldier described the sound of it flying close overhead as about the same as a small propeller aircraft at 1,500 feet. They only flew these machines at night and during the day kept them in a secret hangar. It was known as MD-500P and nicknamed The Quiet One. With a little Googling you can find it on Wikipedia(don't believe everything on that site, please).

That could be what I heard tonight- a very quiet helicopter. I'm inclined to believe that's what it was. Perhaps it was an AH-64 Apache, which uses technology such as the scissor rotor blades first used on The Quiet One.

That first one a year ago is a different story. I have never heard anything that strange in my life. For now, it remains in the category of unexplained phenomena.