If you could figure out that, you could easily figure out how far away they are from you.
I never checked that way before, but will make a point of it from here on, because I don't have to have anything with me (and haven't carried my little scope in years). Thanks for pointing it out.
My estimate for maximum arc observed being about 45° was a pretty safe assumption, since if an aircraft were flying at Mach 1 (the speed of sound), it's sound cone would sweep out at 45° from its direction of travel, so the aircraft would appear displaced 45° away from the apparent source of the "boom". Taking that as the yardstick, it should be obvious that an aircraft flying at Mach 0.5 (something less than 375 mph - it varies, so it's less at higher altitudes) would appear displaced from the apparent source of the sound by about 26°.
My "best guess" was about 30°, so let's go with that. It works out to about 430 mph. The distance away from me would be hard to calculate accurately by the sound. The angular differential between the plane's position and the apparent source of its sound will be a constant with respect to its velocity. By that I mean you would actually have to measure the elapsed time between a plane's passing a point and the apparent source of the sound reaching the same point. Then the calculations become pretty easy. I'd say they are still less accurate than timing the plane's transit across the field of view of my little scope, after "measuring" the wingspan with the reticle. (I haven't done that in years, and barely know if I could even find the damn thing! - This discussion is kinda getting my juices flowing, so maybe I should dig it out & start seriously studying this crap again.)
As far as the planes getting quieter, that is exactly what is happening.
I know. In fact I knew one of the designers of the quieter ducts (as I mentioned previously on this thread). HOWEVER there is a distinct difference between the commercial jets and the (presumably) military ones, which forces me to ask if the military 767s (for instance) use different engines than the commercial ones. I'm not kidding...The ones I see are barely audible!
One more thing, contrails can ONLY emenate from the jet engine. No conspiracy there, either. Sorry, again.
I SAID as much, and only commented that only when a jet is at high altitude does it LOOK LIKE they could come from the wingtips (which they do not). At that, it is only without binoculars that one might be subject to the illusion, because one can barely see the plane at that altitude. For the record, vortices are only visible at low altitudes under the right conditions and are distinctly different than contrails....GEEZE!!
Home
login