Despite the title, I’m asking about any type of rigid, semi-rigid, or non-rigid aircraft. Just take blimp as shorthand.
From what I’ve read, blimps normally fly at about 1500 feet. At that height how loud would they be to people on the ground? Could you hear one approaching before you saw it? Would it be loud enough to make people look up to see what was coming?
It seems like lighter-than-air craft today mostly use gasoline engines originally designed for other purposes. Are they the source of most of the noise? Would it make a difference if an electric engine were used so that the only sound would come from the propeller? How loud would that be? How noiseless could you make a blimp if you tried?
I’ve seen one of the Met Life blimps stop over at the Jennings, LA airport a couple of times and have watched it circle and maneuver for extended periods. In the cruise, it’s pretty quiet; maybe only clearly audible within a quarter mile or so. For this and any other blimp I’ve ever seen, I’ve pretty much always seen it before I heard it.
In the ascent, on the other hand, the engines are at a fairly high throttle setting, so they are quite audible.
I saw (heard, first) the Goodyear Blimp fly over my house when I was a kid. This was in Memphis, TN in the late 1960’s. The blimp was there for the Liberty Bowl, so it was mid to late December. I heard the engines a few minutes, wondering what the noise was, when I saw the blimp overhead. I have no idea how high the blimp was, but 1500 feet sounds a bit high. I would have guessed five hundred or so. There was a 22 story building in the area and I would have guessed it was higher than that, but not five times as high.
The Goodyear blimps fly around NE Ohio all the time. They are not very loud. They do kind of have a distinctive sound, I guess because, compared to an airplane, they are going so slowly, so the noise persists much longer than it would if it were a plane.
I’ve never heard a blimp before I’ve seen it. On the contrary, I’ve heard it and scanned the horizons to see it because I knew it had to be in visual range.
Actually, it seems like you often hear a blimp before you see it.
What I’m getting from this is that a blimp isn’t as loud as, say, a helicopter but that if one were to pass overhead you couldn’t help hear the sound of it going past.
I live between Cleveland (where the sports are) and Akron (where the blimps are) so I get 3-4 blimps fly directly over my house each year.
I agree that if you hear a blimp you can see it. But I also think it’s quite loud when it’s over the house. And it moves hella slow so it feels louder than a helicopter. My dog used to bark non-stop until they went away.
There has been work going on near my house on the high-tension wires, and they are using loach helicopters. So I have a lot of helicopters low over the house lately. the loaches rattle the windows while a blimp sort of drones on. I don’t think the blimps are less loud, they just don’t disturb the air as much.
Without looking it up I don’t think there are currently any rigid or even semi-rigid blimps (i.e. actual airships or zeppelins) in existence today. They are all gondola-suspending balloons. Although some may have multiple, separate gas bags inside the main bag for safety, efficiency etc. none have any structural elements (including the engines) mounted anywhere but on the gondola itself.
As far as noise, yes, the vast majority comes from the propeller (more than from the engine). Propellers are incredibly noisy. If a blimp were to shut its engines down for some reason and just float or coast it would be pretty much silent. However, given the danger of them being at the mercy of strong winds this isn’t something they normally do.
Wow! Finally a new semi-rigid airship! Given advances in technology (carbon fiber, compact & lightweight engines, global communications, long range weather prediction etc.) I think the return of the true airship is long overdue!
If it was 30 years ago I could have asked my high school physics teacher. She one a national contest and got a ride. She came back with cool stuff and did a great presentation.
I think of her whenever I see one. One of those great teachers you never forget.
Sorry had to share, the couple of times I saw one, it wasn’t loud enough to be memorable.
This. The Goodyear base at Pompano Airpark is a few miles from my place. I see the thing flying around most days.
Going overhead they are irritatingly noisy. It’s an angry buzzy noise like a modern helo. It’s a little quieter but lasts a lot longer. I suspect most of the noise is the prop blades putting out a pulse at each passage near the hull which then thrums against the fabric hull acting like a gigantic sound board.
As an aviator I always enjoy the sight & sound of any aircraft. These are real easy on the eyes, but a bit less happy on the ears.
I have ridden the Goodyear several times and lived right in its flight path most all of my life. I only hear the noise when it is flyig lower than usual. Sitting inside is very loud and we wear headsets for ear protection.
Mid-fifties to early sixties, the Navy was still flying blimps out of Lakehurst. They flew low enough over the Jersey shore that we kids would wave to the crews, and they would wave back. I don’t remember hearing much of anything.
the engines used on the majority of Goodyear blimps has been the same engine that several Cessnas and Pipers have used. By themselves, they are noisy enough, but not terribly irritating. (It would have helped, for comparison, if Cessna had sold a lot more Skymasters so that more posters would be able to think back to the sound of two such engines running together.)
The main issue, (as noted previously), is that with a fifty m.p.h. maximum speed, they stay over the one hearing them for much longer. Even with two engines, they are not nearly as loud as the larger Bell and Sikorsky helicopters routinely used as ambulances. However, if they are within hearing distance, they tend to stay within hearing distance for several minutes while your typical similarly equipped airplane passes over in about one third the time.
I think the giant transport helicopters that fly over are the loudest and most aggravating. I can no longer even hear the jets from LAx which fly over me all day long.
I’m about a mile and a half from Heinz Field/PNC Part. When they really put the throttle to it, I can hear it (barely) inside my home. During normal cruising flight, I can see it but its pretty much silent.
