Well if I get emergency in flight and need it, I land and uncage it, then takeoff and go back to my emergency

Wind doesn't affect trim or airspeed, but will change ground speed and track. The aircraft has no way of 'knowing' the airmass is moving. Someone in a hot air balloon, for example, will see the ground moving past, but won't feel any wind because they're moving with it. Replace the balloon with an aircraft, and the same thing applies, except aircraft is moving forward through the air but still drifting with it.

Jet engines don't produce a torque effect. You can put your feet on the floor and go to 100% on takeoff and it'll track straight down the runway (assuming no outside force, such as a crosswind or dragging brake, interferes).

I'm not too sure wind DOES NOT affect trim. Well, not trim directly. Imagine an aircraft, perfectly trimmed for stable level flight on no wind. Then put a 10-knot wind coming in from 30 degrees left. It will not affect TRIM but since the outside conditions have changed, I would assume that it would affect the "balance" and the pilot would have to re-trim. I say "assume" because I am not a real pilot although the example would make sense regarding trim.

As for the hot air balloon example, even if the wind were blowing the balloon, the occupants would still feel wind, I presume. Why? Well, if the wind is blowing the balloon east and the wind is going at 15 knots, I don't think the balloon will go 15 knots as well, probably slower, maybe 12-13 knots. Therefore, the difference would equal wind.

You don't trim for wind. Wind has no effect on the aircraft's trimmed state, only which way it will drift, which is corrected by changing your heading slightly in order to keep tracking in the desired direction. In your example you talk about suddenly introducing a 10 knot wind from the left. A SUDDEN change in wind velocity (gust or turbulence) will affect the aircraft, but you don't re-trim for it as gusts are short lived and you will be through it before you know it.

You won't feel steady state wind in a balloon, although you may feel the odd gust. Balloons aren't pushed by the air, they drift along within it. If you hang a flag from a balloon in flight it will hang straight down! Imagine standing waist deep in a river (a smooth flowing river, not rapids). You will feel the water flowing around your body. Now imagine lying back in the water and floating. You will be carried with the current and won't feel the water flowing at all since you are moving with it.

The baloon will go 15kt. Why would you think otherwise?

A few points. First, all airplanes experience the greatest instability in the roll axis. Pitch trim is particularly stable, and a properly cg'd airplane will hold a particular pitch trim (and thus airspeed) with viggor. Also in yaw, since all planes are designed with a large wetted surface in the rear (vertical stabilizer or "fin") around which to "weathervane". In roll however, the plane is basically force neutral, and thus holds roll trim very weakly.

Why should this be so? Mostly because the other two axes are aligned orthogonally to the airflow, and thus can leverage the forces of forward motion to affect a trim. Roll, however, is aligned *with* the airflow, and so aerodynamicists are forced to use some very subtle tricks to acheive roll stability (and trim effectiveness). Some such tricks include wing dihedral and leading edge sweep. The slightest thermal bump or weight shift can disturb roll trim.

So in short, you will either be hand flying roll corrections constantly, or let "george" fly them for you

At any cost it is always a unconscious decision for emergency landing by pilot. It sounds very odd for me, is it effect on tail rotor by this constant?

Seems strange that a multimillion dollar aircraft would not have a 'wing leveler' computer function/feature.

Well it does in fact... its called the autopilot Of course, you have to actively turn that on.

Erm, unless I remember my physics lessons incorrectly, but when you exert X amount of force in one direction (in our case, wind), the object (balloon) will move in that direction but there will be factors that will go against it. For example, pushing a box along a floor... if you exert X amount of energy does not translate directly into movement since you "lose" some energy due to friction which is affected by the box's weight and the floor surface. So in our balloon example, I believe that exerting 15 knots of wind will not give you 15 knots speed... the size of the balloon would obviously create drag and wind resistance, blah blah blah. If it did, we wouldn't be spending the last few years finding aerodynamic shapes to overcome drag in aircraft.

jocko-, I'm not saying that is an immediate and temporary gust of wind. If it were so, then I agree that you don't have to re-trim for intermidiate gusts but the point I was making was that changing outside conditions may affect the aircraft's stability. Sure, the aircraft may re-settle after the gust, but the point is it was "disturbed" from it's straight-and-level flight due to this change.

If you consider a CONSTANT wind from the left, I'm guessing a re-trim would be in order as the wind will push the aircraft towards the right. And unless the wind is coming from the same level as the aircraft, I'm guessing it'll be pushing the wing up or down a bit as well.

Again, these are just my guesses as I'm not a real pilot and just going by what I know and logic here.

The baloon is moving with the air mass. There's no significant friction. It's not being 'pushed'. If anything, the air-mass is being 'pushed' or 'pulled' or whatever you'd like to call it, but the baloon itself isn't moving withing the air-mass. It's all relative, so I'd say you missed out on a whole bunch of physics lessons.

The balloon is moving with the air mass, yes, but not at the SAME SPEED as the air mass.

Note that we are talking about a big-ass hot-air balloon here, not a child's toy balloon, so all that surface area + mass has to generate air/wind resistance of some sort.

Yes, it is. It's speed relative to the air mass is zero. There is no wind for the baloon. It is moving with the air mass.

OH MY GOD.

I literally saw this exact same argument on Prodigy 20 years ago, except it was about a plate suspended in the air and some talk about "the lee side" of the plate.

Amazing to see that nothing has changed.



The Jedi Master

But if you have an enclosed gondola under the balloon, full of chickens sitting on a conveyor belt, and suddenly all the chickens take off? Will it then be Bernoulli or Newton who's resonsible for the results?

Lol. GrayGhost and I will just have to agree to disagree about this one, unless we have an expert hot air balloon pilot here... not that it has anything to do with the original topic of trim.

If a balloon at 0m/s is suddenly subjected to a uniform velocity field of 15m/s, this velocity field will result in pressure drag on the upstream side of the balloon, and a suction side (low pressure) in the lee of the balloon. This will create a force pushing the balloon in the direction of the wind. After a long period of time to allow steady state conditions to arise, the balloon will be moving at the same velocity as the wind, i.e. both bodies are moving at 15m/s.

At this The balloon will not move slower than the wind, as this would require some *other* force to retard it. There will not be any drag in this uniform velocity field, as it is actually drag that gave rise to the balloon movement anyway. Ditto for skin friction. For the purposes of not making this any more complicated, the effect of (any) induced drag is also neglected.

Yes, this is an ideal system. In real life you wouldn't get a uniform velocity field anyway, you'd get gusts from alternate wind directions, which will slow down the balloon. However, all things constant, the balloon would eventually (asymptotically) reach the velocity of the wind.

Unless gunned down by an A-10.

ft: Neither; blame messers Navier and Stokes and whoever implements a seamless fluid structure interaction model.

Another way to view it: A cork is floating in a stream. Is it moving with the water, or is it moving slower than the water?

If you say it'd move with the water, Bob's yer uncle: The cork in the stream is the balloon in the air.

If not, how long is the wake formed downstream of a cork floating in a stream? Try moving a cork through still water. However slow you move it, it will create a wake. Thus, the cork in the stream would form a wake if it was moving slower than the water. You will find it does not, and hence, it does not.

-Ice,
you can consider me a hot air balloon expert... although a probably somewhat overqualified one.

Yup, no question. The baloon will arrive at the same ground referenced velocity as the wind. It's airmass referenced velocity will become zero.

As for wind's effect on trim, there is none. Transient "wind" (i.e. Turbulence or gusts) will upset a stable trim and require hand correction, but due to it's changing nature cannot be trimmed for. Steady state winds may require a change of heading to track a specific course over ground, but not a trim change.