Pit Stop

[230RN]

[K Frame]

Heh...

But... the hell is that? Is that starting up the engine creating a mini vortex?

[Jim147]

I want to see them get the racing jack under there and change the tires.

[230RN]

Vortices forming around jet intakes are fairly common due to the pressure reduction. (You remember the story about the mechanic getting sucked into the engine's intake.)

If conditions are right, you can see the cloudlike formation of "fog" over the tops of the wings from that same kind of pressure reduction.

https://youtu.be/s1c-O0qWQBQ (3:49)

One could look at it as if there's a certain amount of heat in a volume of air.  If you let that air expand, the heat gets "diluted" so the air gets cooler.

If you compress that air into a smaller volume (as in a diesel engine), the heat gets "concentrated" so the air gets hotter.

This "dieseling" effect is the principle behind the "fire piston" emergency fire starter.

[RocketMan]

Somebody turned the chemtrail generator on too soon.      

[Devonai]

I loved kicking around the C-17s at Charleston.  Closest thing to a spaceship I've ever been in.

My unit has C-130Hs from my generation, all built between 1976-1980.  Closest thing to a C-47 I've ever seen, and I've been in a C-47.

[230RN]

Early model contrail generator Mark 0.9

[Fly320s]

Heh...

But... the hell is that? Is that starting up the engine creating a mini vortex?

It looks like the reversers are deployed, so maybe it is backing up.  Power is higher than idle in any case.

[WLJ]

Video of an F-16 doing it

https://www.youtube.com/watch?v=0_4Y_Luf4zg

[MechAg94]

Early model contrail generator Mark 0.9

Mind blown!  (or maybe they just sprayed fresh chems in my area.  why do I have a desire to vote democrat? .....)

[230RN]

...

[Fly320s]

...

What happened?  Thread merge?

[BobR]

Props can do it also. Saw it quite a few times with the P3 in high humidity conditions.

bob

[Hawkmoon]

My unit has C-130Hs from my generation, all built between 1976-1980.  Closest thing to a C-47 I've ever seen, and I've been in a C-47.

The C-130 is not even remotely like a C-47.

[WLJ]

You kids and your newfangled C-47s   

[TommyGunn]

Vortices forming around jet intakes are fairly common due to the pressure reduction. (You remember the story about the mechanic getting sucked into the engine's intake.)

If conditions are right, you can see the cloudlike formation of "fog" over the tops of the wings from that same kind of pressure reduction.

https://youtu.be/s1c-O0qWQBQ (3:49)

One could look at it as if there's a certain amount of heat in a volume of air.  If you let that air expand, the heat gets "diluted" so the air gets cooler.

If you compress that air into a smaller volume (as in a diesel engine), the heat gets "concentrated" so the air gets hotter.

This "dieseling" effect is the principle behind the "fire piston" emergency fire starter.

Adiabatic Gas Effect.

You can do it at home:  get a can of compressed air at a office supply store used to blow dust off things.  Keep spraying it and as the air empties,  the can gets colder.  

In my father's Navy frogman days,  scuba tanks were steel,  and had to be dumped in a tank of water when being compressed (charged)  or you'd burn your hand picking it up when done.

[Devonai]

The C-130 is not even remotely like a C-47.

I was making a joke about the age of our aircraft.

[230RN]

What happened?  Thread merge?

 

No, I had a good one going there, but I lost the URL and didn't have the time to re-locate it, so I just "...ed" it.  Water under the bridge at this point.

[Lennyjoe]

The C-17 is a great ride!  The plastic seats in the cargo bay aren’t the most comfortable, but neither were the the ones in a C-130 with the damn bar across your lower thigh.  Only the C-5 or the 141 with the commercial seat pallets were comfy.

[mgdavis]

Former C-17 mechanic (part-timer)
It is a common thing. It happens when the thrust reversers are deployed. The blockers and cascades direct air up and forward, which upsets the flow of air entering the inlet and causes it to do this fun vacuuming of the flightline.
One of the coolest things I have ever seen was one annual tour graveyard shift standing ground for an engine run at 2 AM. The thrust reversers were deployed during the run, which I think was done so as not to blast the jet parked behind us, and a vortex formed at the number 3 engine. At the same time, the fan blades started to glow an eerie blue and St. Elmo's fire spread across the inlet. I said something into my headphones to the effect of "the engine is glowing blue" and the guy at the controls chopped power, disrupting the otherworldly scene. It was one of those moments that make me wish I had a camera hardwired into my optic nerve. Once everyone decided I had not been experimenting with recreational pharmaceuticals the run resumed, but the lightshow did not reappear.

Another fun fact: The C-17 can back up a 4% grade while fully loaded.

[BobR]

Another fun fact: The C-17 can back up a 4% grade while fully loaded.

Another fun fact. The C 17 can deploy the thrust reversers on the inboard engines in flight. That's gotta be an E ticket ride from altitude! Best we could do on the P3 was flight idle on the engines, drop the flaps and drop the gear and point the nose where you want to go.

bob

[230RN]

Stop me if I'm wrong, but I don't think you need the thrust reversers to see that intake vortex.

I suppose it may be possible that they make it more likely for the general intake fog to form since they could  add some exhaust humidity to the air around the intake, but I've seen vids of the vortex forming well into the takeoff run.  A wet or damp pavement under the engine seems to be the prime requisite for the vortex effect.

Just to be clear,

INTAKE VORTEX:


INTAKE FOG:


Terry, Landlubber, but I like examining the idea that air can support a couple of hundred tons of metal up there way high in the sky, 230RN