contrail

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This compresses the sense of depth and makes it look like the contrail starts right behind the jet when it doesn't.

Its just a very unusual angle and with the sun setting.

.... Phil

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This compresses the sense of depth and makes it look like the contrail starts right behind the jet when it doesn't.

Its just a very unusual angle and with the sun setting.

.... Phil

Drat. Beat me to it :)

Most people think the engines control an aircraft's velocity, but they don't. The velocity is determined by the attitude, which is controlled by the stick and elevators.

The engines determine the (change in) altitude.

If you keep the attitude and speed constant, and increase the engine power, you will go up; reduce the power and you go down.

Not in that location.

For contrails, yes. But; sometimes condensation/clouds form on the wings - and rarely in front of the wings :)

In this case, if you look closely, it appears that at least some of the condensation/clouds are forming on/near the wings.

That's why it's so windy inside airplane hangars?

Contrails from the wing and other surfaces usually require the plane to be developing significant G forces, or the air is insanely wet. Those trails usually are very short-lived, too.

jon

snipped-for-privacy@downunder.com wrote on 6/30/2017 7:31 AM:

The big difference between water vapor and CO2 is that water vapor reaches a steady state increased level while we have not found that level for CO2. Both water vapor and CO2 leave the atmosphere at some rate. For water vapor that rate is pretty high, so an increase in H2O is quickly absorbed and a steady state water vapor generator will only produce a small increase in vapor levels. CO2 has a much longer lifetime in the atmosphere so even a small increase in production levels give rise to larger levels in the atmosphere that continue to rise for a longer period.

You can have the same VIP experience if you go on a rainy afternoon or after a thunderstorm; there are a fair amount of days like that in southern Florida during the summer

Sometimes, not very often, you get really spectacularly massive trails that just persist and expand in the sky. I've noticed when this does happen - which as I say is not often - there are sometimes one or more little white dots moving among them that don't appear to be part of the trails themselves and move independently of them. Next time you see a grotesquely fat trail, take a closer look at it and you might spot them.

That's why airplane hangars have floors.

Next you'll be saying you need to get a lighter desk, because you get tired watching the floor holding it up.

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A plane's "attitude" or more correctly "angle of attack" controls the amount of lift generated by the wings.

To gain any benefit however, airspeed must be maintained above the stall and this requires engine thrust.

Climbing requires engine power, energy from which is stored as altitude is gained - then recovered during descent.

.... Phil

it is all interrelated, can't just look at one thing

I was visiting one of our VME module users, in a place near SFO. He said, let me show you my workshop. He had a partially assembled 747 on the floor. It looked like some kid's broken toy.

They can also test full-bore engines and APUs. That can get windy.

You can separate the concerns as I described. Usually you don't keep them completely separated, but that is a different issue.

FFI see chapter 9 of the classic "Stick and Rudder" by Langewiesche. Written in 1944, it is still in print and available from Amazon.

APUs not so much, though.

Exactly. The way an airplane feels to the pilot is neither physics nor aerodynamics. The only dependably simple principle of flight is conservation of energy, which suggests that engines burning fuel are needed to move air.

APUs are (low bypass) turbines.

Wasn't there some finding a while back that said that our existing understanding of how wings function is flawed? ISTR some bunch of scientists saying there wasn't enough lift generated by the pressure differential between upper and lower surfaces to account for the real- world performance we see. Anyone else hear that?:-/

That isn't how wings work! The traditional explanations taught in school physics are /very/ deeply flawed.

Wings are complex and there are many effects. Not being an aeronautical engineer, I certainly don't understand them all. However, a significant mechanism is that the wings deflect the air mass downwards; the equal-and-opposite reaction is the lift.

For a better understanding, see