Is this a pic of a sonic boom ?

Sent to me and I can't explain.
Know the crew here will tell.
Thanks

a reply to: donlashway

No. Its got a really technical name, that I can never remember. Its caused by high humidity and low pressure caused by the aircraft.

I've seen it happen around P-3s, B-2s, 747s, and just about every other type out there. It's commonly mistaken to mean that the aircraft went supersonic though, but it doesn't.

It's a vapour cone.

The long name is Prandtl-Gauert Singularity.

A vapor cone, also known as shock collar or shock egg, is a visible cloud of condensed water which can sometimes form around an object. A vapor cone is typically observed as an aircraft, or object, approaches transonic velocity. Atmospheric water then condenses, and thus becomes visible, as air pressure varies suddenly across shock waves associated with supersonic flow speed.

Atmospheric condensation around aircraft is also associated with low-pressure regions in subsonic flight, and can typically be observed in damp conditions; but this does not result in conical condensation clouds.

Condensation cones appear in what was described as a Prandtl-Glauert singularity.[1] In addition to making the shock waves themselves visible, water condensation can also occur in the trough between two crests of the shock waves produced by the passing of the object. However, this effect does not necessarily coincide with the acceleration of an aircraft through the speed of sound or Mach 1

a reply to: donlashway



A sonic boom is the sound associated with the shock waves created by an object traveling through the air faster than the speed of sound. Sonic booms generate enormous amounts of sound energy, sounding much like an explosion. The crack of a supersonic bullet passing overhead is an example of a sonic boom in miniature.

a reply to: Zaphod58

I used to love watching the heavies land at McChord AFB in rain or high humidity... the entire top of the wing surfaces looked as though they were enveloped in a heavy fog. Really neat to watch...

a reply to: donlashway

A sonic boom is a noise. From Scientific American:

the propagation speed of sound waves is finite, sources of sound that are moving can begin to catch up with the sound waves they emit. As the speed of the object increases to the sonic velocity (the local velocity of sound waves), these sound waves begin to pile up in front of the object. If the object has sufficient acceleration, it can burst through this barrier of sound waves and move ahead of the radiated sound. The change in pressure as the object outruns all the pressure and sound waves in front of it is heard on the ground as an explosion, or sonic boom.

What you are seeing is the pressure wave from this phenomenon causing condensation. This plane is in the process of going supersonic.

a reply to: Zaphod58
Thanks, he sent video too so cool.

It's great knowing answers are just a post away.

Prandtl-Glauert Cloud

GFDI: Cloud formation on adiabatic expansion

other images

edit on 13-6-2014 by donlashway because: (no reason given)

a reply to: madmac5150

It was always fun going engine runs in those conditions. You always got a streamer of moisture going into the engine.

a reply to: donlashway

Nice shot of an F18 though.

a reply to: donlashway

That actually caused, and still causes people to think the B-2 is supersonic, therefore has some exotic propulsion system.

Very informative and interesting. Flag & star for ye for teaching me something new.

originally posted by: Zaphod58
a reply to: madmac5150

It was always fun going engine runs in those conditions. You always got a streamer of moisture going into the engine.

Watched many an F-16 engine run with moisture vortices running into that hoover of an intake... like tiny little tornados...

a reply to: madmac5150

That one was always my favorite when conditions were right. Little beast though when it came to eating everything in sight, and quite a few things that weren't.

a reply to: donlashway

Yes.

a reply to: Staroth

Really? So a P-3 is supersonic now?

www.navlog.org...

Hey, I grew up at McChord! Born on Fort Lewis though, dad was AF. Used to love going down to the flightline to watch all the heavies, F-15s and A-10s take off. Good times. Small world huh?

originally posted by: madmac5150
a reply to: Zaphod58

I used to love watching the heavies land at McChord AFB in rain or high humidity... the entire top of the wing surfaces looked as though they were enveloped in a heavy fog. Really neat to watch...

originally posted by: Zaphod58
a reply to: madmac5150

It was always fun going engine runs in those conditions. You always got a streamer of moisture going into the engine.

Agreed, its always fun watching that little tornado. I love it when you do an engine spin after the aircraft has been idle for a while and the humidity is up a bit. The water vapor clouds that shoot out as two or three jets from the pneumatic starter can be quite spectacular, much like a smoke machine. I once watched a Styrofoam cup make a lazy entrance, propelled by the standard night time breeze across Botany Bay onto a run-bay with a 747 as we were running up on power. It made its way to the number two engine and a colleague and I knew what was about to happen and watched it pirouette then get sucked into the fan and diced into what appeared three perfectly equal longitudinal pieces. Funny how sometimes you just know its about to happen.

My favorite phenomena though is a weird cloud you sometimes see in the inlet of an engine on high power. I have seen it a few times and cant explain it. As the engine reaches power above about 80-85% and if the conditions are right, you will see a very slowly moving mist in the inlet that appears to defy both logic and the many cubic meters per second of air being pulled in. I have seen it both in the daytime and at night. It appears as a very slowly swirling mist that is best described as similar in look to a scanning laser through a smoke machine (a la, the opening scene in the movie Aliens inside Ripley's escape pod after it is found). It would appear to be some kind of strobe effect, although I cant explain how it manages to appear so still. Has anyone else here ever observed that?

LEE.

a reply to: thebozeian

Sounds like a St Elmos Fire type effect. I was on a -135 doing a power run that freaked out the ground guys because they had never seen it before.

[I should have read the whole thread before posting, no?]