How Big Is the Airplane That Matches the Width of an 8-Lane Roadway?

[FredGarvin]

That looks really cool Wolram. I would love to fly in any of those. I think the Buccanneer would be my first choice. I love that era of aircraft.

 

[Cyrus]

I believe September is the end...sigh.

http://usmilitary.about.com/od/navyweapons/a/f14lastflight.htm
http://www.military.com/features/0,15240,94327,00.html
http://www.military.com/NewsContent/0,13319,90808,00.html

This ones for you fred,

http://photos.airliners.net/photos/photos/0/0/6/1016600.jpg

:!)

 

[3trQN]

Talk about mixed messages, that singapore airlines picture, the road markings read:

ZOOM
AHEAD
STOP
BUS
SLOW

Maybe that's what confused the driver...

 

[3trQN]

http://www.raf.mod.uk/downloads/wallpaper/typhoon_06_0800.jpg

Sex in the air

And this is a great shot:

 

[FredGarvin]

Cyrus,
That formation pic is pretty damned sweet. I can't imagine having that fly overhead.

 

[DaveC426913]

I have often seen and wondered about this shot. It is always listed as an amazingly-timed shot of a plane just as it's breaking the sound barrier.

Is that what we're seeing? Or is it merely a vapour effect from the shock wave (which still occurs at < Mach 1).

Anyone know for sure?

 

[Cyrus]

It is water vapor condensing in the shock wave.

 

[berkeman]

There was a video at one of the sites posted early in this thread where you see that shock wave hanging around for several seconds on the pass of the plane. Probably you just have to stick around Mach 1 in the right kind of humid air...

 

[DaveC426913]

That's what I'm getting at. I know that wave sticks around. It flits in and out.

What I don't know is if it only occurs AT the sound barrier, or whether it merely requires the right conditions at subsonic speeds.

 

[Cyrus]

The clouds formed by the Prandtl-Glauert singularity are due to the near-sonic amplification of the pressure and temperature perturbations which naturally occur whenever air passes over any bump or object. Thus, an aircraft can fly at one-half or twice the speed of sound and generate no clouds. However, if the same aircraft flies at 0.95 or 1.05 times the speed of sound, the amplification implicit in (Pg2) may be enough to cause condensation in the low-pressure, low-temperature portions of the flow.

the source:
http://www.fluidmech.net/tutorials/sonic/prandtl-glauert-clouds.htm

 

[FredGarvin]

Yeah. We've talked about that one before. Clausius pointed that out a while back. The aircraft doesn't need to be supersonic, but it does have to have established trans sonic speeds.

 

[Danger]

Great pictures, guys. I loved that Tomcat routine. Thanks, all.
This is slightly off topic, but just in case anyone out there still doubts the ability of a camera to register a plane in flight:




http://img196.imageshack.us/img196/1954/b15wp.jpg

That, if anyone doesn't recognize it, is a high-velocity rifle bullet making it's escape from the back-side of a balloon.

 

[berkeman]

Looks like a .22 at around 500fps. That still implies a shutter speed of about 10us (1/100,000th of a second), and/or a fast flash.

 

[3trQN]

I was going to suggest the http://ocw.mit.edu/OcwWeb/Physics/8-02Electricity-and-MagnetismSpring2002/VideoLectures/index.htm #22 has bullet shattering a bulb.

 

[heartless]

nice website 3trQN, there are some pretty good lectures. Now watching, "What holds our world together?", thanks.

//edit

I found something similar to Danger's picture, a movie
Here: http://www.metacafe.com/watch/109587/bullets_path/

I love it.

 

[DaveC426913]

Yeah. We've talked about that one before. Clausius pointed that out a while back. The aircraft doesn't need to be supersonic ...

So, in terms of dispelling this myth, is it safe to say that this is NOT necessarily a pic of plane breaking the sound barrier?

it does have to have established trans sonic speeds..."

What do you mean by this? You mean that, even if the plane is doing less than Mach 1.0, that the shock wave must still be transsonic to get that effect?


This leads me to believe that I'm just splitting hairs - that, give or take .05 Mach, this IS, for all intents and purposes, a pic of a plane breaking the sound barrier. That this could NOT be a pic of a plane doing, say Mach .9 or .8.

 

[Cyrus]

So, in terms of dispelling this myth, is it safe to say that this is NOT necessarily a pic of plane breaking the sound barrier?

Yes, it is in the transonic region, that's all. Meaning the airplane is between mach 0.95-1.01 (ish) roughly. (It may or may not be breaking the sound barrier with the cloud formation)

This leads me to believe that I'm just splitting hairs - that, give or take .05 Mach, this IS, for all intents and purposes, a pic of a plane breaking the sound barrier.

Well, not really. This cloud does not visualize the shock wave of the flow. All it does is indicate the airplane is in the transonic region. If its flying below the speed of sound, it is not breaking the sound barrier.

As a final note:

Finally, it should be clear that Prandtl-Glauert condensation has nothing to do with "breaking the sound barrier" and is not a Star Trek-like "burst" through Mach one. An aircraft can generate a Prandtl-Glauert condensation cloud without ever exceeding the speed of sound.

Did you go through the link I provided you? It explains all this better than I or fred. (well, me at least)

 

[russ_watters]

Yes, it is in the transonic region, that's all. Meaning the airplane is between mach 0.95-1.01 (ish) roughly. (It may or may not be breaking the sound barrier with the cloud formation)

Somewhere there is a video of that - an F-14, I think, flying past a carrier at just under Mach 1, and as it flies through regions of slightly higher or lower humidity (remember, over the ocean, the air is always near saturation), the cloud comes and goes.

edit: found 'em: http://home.pacbell.net/ok3/

The F-14 video doesn't have sound, but the F-18 video does: no sonic boom, so the plane is just below the speed of sound, in the transonic region. The explanation on the website isn't very good, but on the F-4 pic, you can actually see where the shock waves come off the wing: near the area of maximum thickness on the top, and slightly further back on the bottom - the F-4 wing is not symetrical like many newer aircraft. The shock wave starts at the point of maximum thickness (where the air is moving the fastest and moves forward on the wing as the plane accelerates. If the plane doesn't accelerate, past the transonic region, the shock wave will just sit there on the wing and never move to the tip - making for an extremely bumpy ride.

 

[DaveC426913]

Wow, that F-14 video is incredible!

 

[russ_watters]

Not sure if my explanation was quite right about what moves where, but http://www.centennialofflight.gov/essay/Theories_of_Flight/Transonic_Flow/TH19G6.htm" is an illustration of it. The F-4 pic I mentioned above looks a lot like M=.9 sketch, with the supersonic (and therefore, lower pressure - causing condensation) region further forward above the wing than below).

 

[Danger]

Looks like a .22 at around 500fps.

While I can't vouch for the speed, I can say that I've never seen a .22 rimfire bullet that looked like that. The closest that I've run across were Hornets or Yellowjackets, both of which are definitely supersonic. And I've seen very similar pictures where the bullet is clearly identifiable as a spire-point boattail hunting round.

 

[AtomBeam]

Prandtl-Glauert Clouds

U.S. Navy F/A-18F Super Hornet fighter flight demo that includes a spectacular transonic, high-speed pass (vapor cone included): http://video.google.com/videoplay?docid=6017342022780502321

Photos of transonic F/A-18 Hornet fighters with the Prandtl-Glauert Cloud: http://ChamorroBible.org/gpw/gpw-20061112.htm (via http://ChamorroBible.org/gpw/gpw-The-Spectacular-Clouds-of-the-Transonic-Flight-Regime.htm )