Stunning Aerial Photo of a USAF C-17 Globemaster III Parting Clouds, Leaves Corridor-in-the-Clouds

http://ChamorroBible.org/gpw/gpw-20041010.htm ^

[beelzepug]

The purpose of the winglets is, in part, to help reduce these wake vortices. I wonder what that wake would look like without them?

[muffaletaman]

The existence of the curls at the edges of the corridor are indeed caused by the wingtip vortices.

However, the central depressed area is due to what makes a wing fly. The vortices are a side-effect of this process but not the principal component.

The common misnomer in what "makes" a wing fly is lift. And indeed "lift" is the net effect of the process.

But more accurately, wings fly by accelerating air downward.

The equation F=MA applys. The upward force acting against the wing (i.e.lift) is a result of the mass of the air which is accelerated downward by the wing.

This is easily understood by anyone when one considers how a propeller works, or a helicopter rotor. It is easy to both visualize and experience the motion of air involved. But is less well understood when applied to a wing.

Essentially, a wing is a "linear propeller".

Each second of level flight, as the plane moves forward, it accelerates the mass of air it passes through downward.

Some of the air which passes below the wing is compressed by the wing and thus thrust downward. The air directly above the wing is rarified due to the wings shape and orientation relative to the direction of motion, and thus a volume of air above the wing is also accelerated downward.

That is also why symmetric wings on aerobatic planes still work - they are oriented by the aircraft's attitude such that the accelerate the air downward - and why "normal" wings with a flat bottom and curved top will still make the plane fly when it is upside down.

The total mass of all the air moved by the wing - multiplied by the acceleration of that air (which yields the speed to which the air is propelled downward) exactly equals the weight of the aircraft in level flight.

The vortices are a side-effect of the difference in air pressure between the top and bottom surfaces. So the explanation that there is high pressure below the wing and low pressure above it are indeed correct.

But the common description - which is that the air on the bottom of the wing lifts it, and the air above of the wings "sucks it upward" (no pun intended) - doesn't accurately describe the process.

The accurate physical description is the acceleration of the mass of air downward. That is the net effect of what has happened to the atmosphere after the aircraft has passed.

Short Version - An aircraft flys by pushing air downward.

[norton]

YC-14 or 15 were C-130 replacements.
C-17 takes some points from the 15 but is different class....except that it'll land on a dime and take off from your driveway.

[UCANSEE2]

bttt

[7.62 x 51mm]

Thank you for your service, and welcome home.

[JRandomFreeper]

You "didn't mean anything," but with your callous and thoughtless remark you've left a USAF photographer and an entire C-17 aircrew lying, distraught, in fetal positions under the O-club bar.

They're not as think as you drunk we are.....

/john

[LSU Engineer]

Even with the winglets, the C17's wake vortex is apparently strong enough to limit it's airdrop capabilities, particularly when flying in formation.

Imagine hanging from a parachute in that wake!

www.globalsecurity.org/military/library/report/gao/ns97038.pdf

[Thinkin' Gal]

I was thinking about the verves in posts 28 and 33, and those who had the moon under their feet (twelve, all Americans). I know it's off topic, but not really when you consider what the image may represent. It is a military aircraft, after all.

Anyway, I considered the verses and got an hunch about those moon landings, so I went to Google and found a link with the information I needed. That is, how many days were there between the first moon landing, and the last?

Apollo Program 1968 - 1972

Apollo 11

Moonlanding Date: 20th July 1969. Armstrong set foot at 10:56 EDT

Apollo 17

Moonlanding Date: 11th Dec 1972

http://www.moonpeople.com/html/themoon/walkers.html

That link didn't have a time for the last landing; another site listed the Apollo 17 landing at 19:54:57 UT

So, 10:56 EDT = UT -4 = 14:56 UT

Therefore, the time between 1st and last landings was 1240 days, plus ~5 hours.

If someone can verify the math, please do (I do not have my calendar programs on this computer).

What I did was go from July 20, 1969, to July 20 1972 (365 + 365 + 365 + 1 leap year day), then to Dec 11th [11 (7/20 - 7/31) + 31 (Aug) + 30 (Sept) + 31 (Oct) + 30 (Nov) + 11 (to 12/11)]

So far so good? 1240 days, and ~ 5 hours.

It appears, then, that this time frame is almost exactly 42 lunar months, a time, times, and half as it were. Using the lunar month value 29.53, 42 months = 1240.26, or 1240 days and 6.25 hours. For a 3.5 year period, those 5 hours may be even closer to the actual lunar years than 6.25. I also noticed that the calculation above (using solar months) is marked on each side by an 11 day period, which is also the difference between a lunar year (~354 days) and a solar year (~365 days)

That the landings would be at the same time [as calculated astronomically] is no surprise, but the 42 lunar month total is very interesting indeed.

I tried to Google various keywords to see if I could find such a study, but no luck. I do try to find this stuff from other sources.

"The Eagle has landed", FWIW.

Here's some more trivia:

Apollo 11

Command Module Nickname: Columbia
Lunar Module Nickname: Eagle

Apollo 17

Command Module Nickname: America
Lunar Module Nickname: Challenger

Revelation 12:14 And to the woman were given two wings of a great eagle, that she might fly into the wilderness, into her place, where she is nourished for a time, and times, and half a time, from the face of the serpent.

I can't explain it, I just do the math.

[Thinkin' Gal]

is it female?

Yes. BTW, you might find post 49 of interest also.

[JRandomFreeper]

For one thing, it can use the smallest and roughest of airfields, including; aircraft carriers, dirt roads, assault strips, and on the ice and snow strips at polar research stations

Roof of my Toyota.... Oh, sorry, the pilot only did a touch and go at the east end near the over-run. It just sounded like he came through the cab. I hate bases with a road near the end of the runway. 1983. T-38. Motorcycle. New pants.

C-130s are cool aircraft, and sneaky and quieter than I imagined.

/john

[Ranxerox]

Ouch - you must be a physicist. That explanation, while technically correct, it is utterly useless for anyone wishing to use it in an applied manner.

[Bloody Sam Roberts]

The pattern in the clouds formed by the vortices looks almost like a Bald Eagle with wings spread.

[PushinTin]

For all you pilots out there, ever wondered if there was much wake turbulence behind a C-17. Question answered....

[Thinkin' Gal]

Sorry, I should have pinged you to posts 28, 33, and 49.

It's Columbus Day! Go figure...

[Nova]

"C-17s have set 33 world records – more than any other airlifter in history -- including payload to altitude, time-to-climb, and short-takeoff-and-landing marks in which the C-17 took off in less than 1,400 feet, carried a payload of 44,000 pounds to altitude, and landed in less than 1,400 feet. These records were set during flight-testing at Edwards Air Force Base, Calif. , in 2001."

Info from www.boeing.com/defense-space/military/c17/sitemap.html

I was mistaken about the abilities and mission potential of this aircraft (I've been out of the military for three decades).

[LeGrande]

Some of the air which passes below the wing is compressed by the wing and thus thrust downward. The air directly above the wing is rarefied due to the wings shape and orientation relative to the direction of motion, and thus a volume of air above the wing is also accelerated downward.

To nit pick a little, the air above the wing is accelerated downward and behind the wing. That is the major component of the lifting force. The vortices's are caused by the air from the sides coming in and filling the void.

[Palmetto]

I have to wonder: if the turbulence is so bad, doesn't it mean this thing is working awful hard to push itself through the air (i.e. it's not an efficient design)?

To create lift, a wing must have a lower pressure on the top surface versus the botttom surface. Where the top and bottom surfaces meet on the wing tip, this difference in pressure is reconciled and creates vortices.

It is simply the consequence of a great wing design creating a LOT of lift for this very heavy plane.

[billorites]

"Short Version - An aircraft flys by pushing air downward."

Well, the downwash that results from a finite wing produces both the wingtip vortices and the pretty pictures.

BTW, I thought an airplane flew because Bernoulli said so.

Now you're telling me Dr. Newton had something to do with it?

[Turk82_1]

Thank you, but for heaven's sake, I got out in, what 1989? The Wall was still up, and I never got close to action. Hence, the tag line.

As for all those pointing out what a doofus I am for thinking the C-17 was the 130 replacement....jeez, I'm sorry, but that's what I had been fed when I was in, and I didn';'t keep up on the subject when I got out.

Still, the C-17 will alway remind me of that dim litle office in Ft. Bragg, and the Major who stared at the back of my head all day...and how I bamboozled him - but that is another story.