Any which way the wind blows (physics brainteaser)

[ThinAirDesigns]

...deciding that my internal clock and superior knowledge of my aircraft's normal performance would be enough to judge things like that even without external references).

A good pilot or even just a smart pilot, could do just that (except that pilot always needs horizon or some sort of artifical horizon just to stay in the air, but it could be completely featureless).

The pilot only need to use some crude counting/timing method. It the corrections are repeatedly needed at somewhat regular and fixed intervals, then you have usable information regarding which direction the wind is blowing.

Anyway, just thought I'd mention this in case you pose this puzzle again somewhere else later on. A little more detail about that area might save your next victims from tying themselves in knots trying to get around additional difficulties that you didn't intend to put in there!

While acknowledging that better wording is always better, I will say this -- an important part of solving a brainteaser is not eliminating information that is not excluded. A good example of that would be your "bland and featureless ground" comment. If someone chooses to take that as an implication that there are no clouds and no sun -- well, that's again part of what brainteasers are about.

JB

 

[Michael C]

Very interesting: I've learnt a lot here. At first I couldn't see any way for the pilot to tell the direction of the wind because I didn't realise that the thermal would be skewed.

I'm now wondering about the problem as originally defined, if taken strictly:

Can a pilot of an uninstrumented and unpowered soaring aircraft make any useful determination regarding which direction the wind is blowing at flight level *without* using clues seen outside the cockpit?
JB

If I take the phrase "*without* using clues seen outside the cockpit" literally, this means that I can see neither sun nor horizon, since these things are outside the cockpit. If the aircraft really has no instruments at all, and I am practically flying blindfold, since I'm not allowed to use anything I see outside the cockpit, can I work out the wind direction by the sensations of acceleration/deceleration, the feedback I'm getting through the controls and my internal clock?

 

[rwguinn]

How do you fly in a circle without using clues outside of the cockpit?

That was my question, too
You need to be able to see something, to maintain constant attitude.
The original question was essentially phrased as having NO instruments (not even a compass), and blind outside the cockpit--as in flying in fog.
Under those circumstances, the is no way to do it.

 

[ThinAirDesigns]

UncaYimmy:

How do you fly in a circle without using clues outside of the cockpit?

And once again, there's nothing in the problem stating that you can't use "clues outside the cockpit" to fly the plane.

That was my question, too
You need to be able to see something, to maintain constant attitude.

And that access isn't denied in the original problem nor in any following post.

I have described how one can use a totally featureless horizon from which no directional information can be derived. No sun, no clouds, no instruments whatsoever. Still solvable.

The original question was essentially phrased as having NO instruments (not even a compass), and blind outside the cockpit--as in flying in fog.

That may be the way you took it, but it's not the way it's worded. Again ... brainteasers don't answer all the questions, but give you enough information to solve the problem anyway.

Under those circumstances, the is no way to do it.

That's correct ... If you are not allowed to fly the plane, you cannot do it -- but that's a strawman. The problem does not exclude information used to keep the plane safely in the air.

JB

 

[ThinAirDesigns]

Oh, BTW rwguinn. Given the stipulations that you asked for (2 of 3 basic instruments), did you have another solution in mind for the problem?

Is so, would love to hear it.

JB

 

[rwguinn]

Oh, BTW rwguinn. Given the stipulations that you asked for (2 of 3 basic instruments), did you have another solution in mind for the problem?

Is so, would love to hear it.

JB

Sure.
In any air, maintaining constant attitude, airspeed, and bank angle, you are going to drift downwind.
Maintaining constant groundspeed (ground reference), your airspeed will change upwind vs downwind
As for the vario--it's better than the seat of my pants anyway

 

[ThinAirDesigns]

Sure.
In any air, maintaining constant attitude, airspeed, and bank angle, you are going to drift downwind.

Agreed.

Maintaining constant groundspeed (ground reference), your airspeed will change upwind vs downwind

For me to understand your solution, we'll have to stipulate some term definitions:

"constant groundspeed": If I'm circling in a breeze, my groundspeed will not be constant -- slower upwind and faster downwind. You may however be speaking of the speed of the point about which you are flying ... the center point of your circle. Could you confirm if it is this point to which you refer?

Thanks

JB

 

[Dilb]

As the pilot makes perfect circles in the thermal they are moving *up* relative to the airmass, but *down* relative to the thermal. One can easily see that it's impossible to hold perfect circles while descending through a tilting column and remained centered. Each circle (or thereabouts) one must correct to the upwind side to remain centered in the column. If one does not do this, you fall out the low side (downwind side) of the tilting column more and more with each circle.

But you're flying what feels like a circle in a uniform wind, i.e. not a circle, but something like a cycloid (or a Spirograph pattern, if you like). Unless you can look at the ground to see "yeah, I'm above the same spot", what feels like a circle will trace out a spiral along the thermal column. Clouds or whatever can only get you pointed in the same direction, not return you to the same spot.

 

[ThinAirDesigns]

Clouds or whatever can only get you pointed in the same direction, not return you to the same spot.

That's correct ... I don't wish to return to the same spot. I'm only need to know if the correction needed to stay centered in the thermal is happening with some sort of pattern or just randomly.

JB

 

[rwguinn]

Agreed.



For me to understand your solution, we'll have to stipulate some term definitions:

"constant groundspeed": If I'm circling in a breeze, my groundspeed will not be constant -- slower upwind and faster downwind. You may however be speaking of the speed of the point about which you are flying ... the center point of your circle. Could you confirm if it is this point to which you refer?

Thanks

JB

Yeah--Found the reference:
"720 about a point"
Rate of climb (descent) will also vary in that circle...

 

[ThinAirDesigns]

Yeah--Found the reference:
"720 about a point"
Rate of climb (descent) will also vary in that circle...

I'm sorry rwguinn -- I wish I could say that the above helps me with my definitional question from #67, but it doesn't.

Would you mind trying again?

Thanks

JB

 

[Dilb]

That's correct ... I don't wish to return to the same spot. I'm only need to know if the correction needed to stay centered in the thermal is happening with some sort of pattern or just randomly.

JB

Ah, I get it now. As I'm not a pilot, here's how I can visualize it:

The thermal, at any constant elevation stays over the same spot relative to the ground, even when the wind is blowing. We can trace out the thermal by noticing where we find lift (let's say it's a circle). By measuring the air pressure, we can determine altitude. Going around the thermal, we find that we have to go faster for one side of the circle (relative to the air), and slower on the other. This difference is twice the wind speed.

We could even do it blind, with just some clocks and accelerometers to measure height and orientation if we wanted to, though I don't think you could determine the wind speed that way, only the direction.

 

[I Ratant]

As instrument flight was explained to me, with needle, ball, airspeed, one can determine if one is turning, with the needle, slipping/yawing with the ball, and climbing/descending with airspeed. (JFK Jr. could have used this information.)
But there is no obvious way to detect wind, either force or direction, without an outside reference, as the plane is -in- the air mass, which adds or subtracts to the ground speed and direction of flight, but not the airspeed.

 

[ThinAirDesigns]

As instrument flight was explained to me, with needle, ball, airspeed, one can determine if one is turning, with the needle, slipping/yawing with the ball, and climbing/descending with airspeed. (JFK Jr. could have used this information.)
But there is no obvious way to detect wind, either force or direction, without an outside reference, as the plane is -in- the air mass, which adds or subtracts to the ground speed and direction of flight, but not the airspeed.

This is a very common explanation -- and depending on semantics and definitions can even be considered correct.

The above bit of conventional wisdom is what makes the brainteaser a bit tough for some to accept. But the method I (and others here) described can be clearly graphed theoretically and can also be easily demonstrated to work in the real world -- soaring pilots use the method regularly.

JB

 

[I Ratant]

Given no instruments, and no outside reference, I think a glider would be in dire straits!
The only physical cues would be g on the body, which is totally unreliable, and wind noise as the airspeed changes.
Is the noise variation due to climbing/diving or due to the speed build up in a wind-up turn?
Overstressing the airframe is pretty common in these situations.
Death spirals are probably the inevitable result, with the wings long gone!
One of our U-2 test pilots reported being over the field at flight level 600 one time. 40 minutes later, he was still there!
Flying into a strong headwind, he'd matched the wind speed with power and trim, until he was making no groundspeed at all!

 

[ThinAirDesigns]

Given no instruments, and no outside reference, I think a glider would be in dire straits!

Correct, and no one has said otherwise.

JB

 

[rwguinn]

I'm sorry rwguinn -- I wish I could say that the above helps me with my definitional question from #67, but it doesn't.

Would you mind trying again?

Thanks

JB

720's about a point are constant (ground) radius turns about a point. You point the wing tip at a point on the ground and keep it nailed there through 2 complete circles. Ususally done in powered flight as a demonstration of airmanship?
And yes, I have time in both sailplanes and power. Just short of licensing, both cases. I was young and broke...

 

[Michael C]

If you are not allowed to fly the plane, you cannot do it -- but that's a strawman. The problem does not exclude information used to keep the plane safely in the air.

It may be obvious to pilots what "information used to keep the plane safely in the air" consists of, but to me, with no specialised knowledge of flying, I have no idea what is essential and what isn't.

In the original statement of the brainteaser, you ask if the pilot can make any deductions about wind direction "*without* using clues seen outside the cockpit". But from reading though the posts I understand that the pilot cannot fly the aircraft if he has no instruments and cannot see anything outside the cockpit. Is this correct?

 

[ThinAirDesigns]

It may be obvious to pilots what "information used to keep the plane safely in the air" consists of, but to me, with no specialised knowledge of flying, I have no idea what is essential and what isn't.

-
And that's why I included in the introduction to the problem, these words:

Here's a related one that may involve a little specific knowledge related to soaring flight but may be fun for others anyway.

-
Michael C:

In the original statement of the brainteaser, you ask if the pilot can make any deductions about wind direction "*without* using clues seen outside the cockpit". But from reading though the posts I understand that the pilot cannot fly the aircraft if he has no instruments and cannot see anything outside the cockpit. Is this correct?

Correct -- with no instruments and a closed cockpit, controlled flight just isn't possible. Anyone who thinks differently should go up with another pilot and get blindfolded and see how well it doesn't work.

It is quite possible however to find (or place) oneself in a situation where there are plenty of "outside the cockpit" references allowing safe flight, but as the problem states, just none that are immediately productive to determining wind direction.

JB

 

[Michael C]

Fine. Now two more questions:

1. If the pilot cannot see out of the cockpit, what is the bare minimum of instruments necessary in order to be able to control the aircraft?

2. If the pilot has no instruments at all, what is the bare minimum of visual clues necessary in order to be able to control the aircraft?