Mind your heading

Jaybird180

Jaybird180

Final Approach
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Jaybird180
Question:
An aircraft in straight and level, unaccelerated, coordinated flight

Can an outside force (ie wind) change it's heading? How?

Similar question: An aircraft pitching up, maneuvering into a stall with the pilot maintaining perfect coordination, is there any condition that could alter the aircraft heading?
 
If you were traveling a river in a canoe, and the water direction/flow changed…would the canoe change heading?

In the stall scenario, assuming single engine prop plane, outside forces would be P-factor, torque, gyroscopic, spiraling slipstream, the wind, earth’s rotation, how many burritos you had last night, etc
 
Jaybird180 said:
Question:
An aircraft in straight and level, unaccelerated, coordinated flight

Can an outside force (ie wind) change it's heading? How?

Similar question: An aircraft pitching up, maneuvering into a stall with the pilot maintaining perfect coordination, is there any condition that could alter the aircraft heading?
Click to expand...

what happens to a rotating object (e.g., prop) when rotated (e.g., the plane pitches up or down)?
 
texasclouds said:
If you were traveling a river in a canoe, and the water direction/flow changed…would the canoe change heading?
Click to expand...

I'd agree that course would change. Heading, I dunno.

texasclouds said:
In the stall scenario, assuming single engine prop plane, outside forces would be P-factor, torque, gyroscopic, spiraling slipstream, the wind, earth’s rotation, how many burritos you had last night, etc
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Which direction would the heading tend to change? All except the burritos could even out assuming the wing halves pitched up at the same rate.
 
Jaybird180 said:
Question:
An aircraft in straight and level, unaccelerated, coordinated flight

Can an outside force (ie wind) change it's heading? How?

Similar question: An aircraft pitching up, maneuvering into a stall with the pilot maintaining perfect coordination, is there any condition that could alter the aircraft heading?
Click to expand...
Yeah. A big ol' gust of wind right upside the vertical stabilizer is going to change it. You'd probably correct for it pretty quick to get on and hold the heading you need to hold the course you want. That would be you choosing the heading in response to the wind.
 
luvflyin said:
Yeah. A big ol' gust of wind right upside the vertical stabilizer is going to change it. You'd probably correct for it pretty quick to get on and hold the heading you need to hold the course you want. That would be you choosing the heading in response to the wind.
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Are you saying that wind can hit just the vertical stab and nothing else?
 
luvflyin said:
No. Of course not. But it's going to have more effect on the vertical stab. It's why weather vanes work.
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Weather vanes have an anchor
 
Salty said:
Weather vanes have an anchor
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Weathervaning is the wrong term to use when the airplane is not in contact with the ground, but gusts/wind shear can still act on the vertical stab and yaw the airplane around. Any gust/shear that yaws the airplane and quickly passes will have caused the airplane to have turned ever so slightly to a different heading if uncorrected - similar to if you just mashed a rudder pedal and returned it. The airplane doesn't have to have any bank angle to turn, it's just a very inefficient way of turning.
 
Salty said:
Weather vanes have an anchor
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For an aircraft in flight, the center of gravity is the "anchor" it yaws around, but only in a variable crosswind.

A steady crosswind will not cause the aircraft to yaw, unless a sloppy pilot is trying to counteract the drift with rudder and cross controlled aileron (i.e. in a skid). But a side gust will cause transient effects.
 
If you have an airplane with an autopilot with a "Wing leveler" or "roll" mode, engage it and see how long you stay on that heading. It's not long. Turbulence will gradually knock you off the heading, a little one way, a little the other maybe, but you're not going to stay dead-on.

Glider pilots can tell which side of a thermal they are on by which wing goes up more. If they didn't want to stay in the thermal, they'd be on a new heading as a result anyway. That in itself shows that thermals are localized enough to not affect the whole plane the same at the same time.

Anybody who has flown in turbulence knows it's hard to maintain heading sometimes. Really the most obvious answer to your question is simply "turbulence".
 
RoscoeT said:
Weathervaning is the wrong term to use when the airplane is not in contact with the ground, but gusts/wind shear can still act on the vertical stab and yaw the airplane around. Any gust/shear that yaws the airplane and quickly passes will have caused the airplane to have turned ever so slightly to a different heading if uncorrected - similar to if you just mashed a rudder pedal and returned it. The airplane doesn't have to have any bank angle to turn, it's just a very inefficient way of turning.
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All that kind of goes out the window when the poster made the premise that the airplane is flying "coordinated." The "so-called" weathervaning is the plane's natural tendency (based on the vertical stab, etc...) to want to fly coordinated. It changes heading because the pilot removed the control input holding it uncoordinated.
 
Rgbeard said:
I'm waiting for an explanation involving p-factor used in a fashion for the purpose.
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P-factor is the tiniest mouse fart of a force for 99% of the airplanes that people here fly, but it always gets elevated to a grand magnitude for those wanting to sound learned.
 
flyingron said:
All that kind of goes out the window when the poster made the premise that the airplane is flying "coordinated." The "so-called" weathervaning is the plane's natural tendency (based on the vertical stab, etc...) to want to fly coordinated. It changes heading because the pilot removed the control input holding it uncoordinated.
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No, you can go off heading in turbulence while sitting there flying coordinated. You can correct it, but you can't totally preempt it.
 
Bob Noel said:
what happens to a rotating object (e.g., prop) when rotated (e.g., the plane pitches up or down)?
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Are you implying that a SE propeller driven aircraft naturally wants to yaw based on a mysterious force that acts at 90 degrees to the prop arc and does so in small imperceptible amounts? And this changes its heading?
 
Jaybird180 said:
Question:
An aircraft in straight and level, unaccelerated, coordinated flight

Can an outside force (ie wind) change it's heading? How?
Click to expand...
Depends on what "coordinated" means. If "aerodynamically coordinated" in a nose-high, slow flight regime — it would appear to be in a ""skidding" turn due to (wait for it) P-factor. Applying opposite rudder would change the heading to less of a turn or possibly to straight flight resulting with the ball re-centered. But then it would be in an uncoordinated aerodynamic side-slip.
 
Salty said:
Weather vanes have an anchor
Click to expand...
Yup. And a plane has a center of gravity and it will act as a pivot point. Not a 'fixed' one, of course like a weather vane. Big ol' gust of wind broadside catching that big ol' tail is going to pivot the plane a little. I don't think this is really what the OP had in mind. More like a sustained effect as relates to heading needed to maintain a course. But he did ask "...Can an outside force (ie wind) change it's heading? How?..." It can.
 
RoscoeT said:
No, you can go off heading in turbulence while sitting there flying coordinated. You can correct it, but you can't totally preempt it.
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That turbulence is causing you to (temporarily) be uncontrolled.
 
dtuuri said:
Depends on what "coordinated" means. If "aerodynamically coordinated" in a nose-high, slow flight regime — it would appear to be in a ""skidding" turn due to (wait for it) P-factor. Applying opposite rudder would change the heading to less of a turn or possibly to straight flight resulting with the ball re-centered. But then it would be in an uncoordinated aerodynamic side-slip.
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A diagram, or video explanation would be helpful in parsing this. Got one?
 
Shifting winds and updrafts/downdrafts would cause roll about the longitudinal axis, tending to shift the lift vector off vertical and cause the airplane to turn. My $0.02 worth.
 
Yes. If you could fly a fixed straight line on the surface east to west in zero wind, you will be crossing different degrees of Variation and your true course would remain unchanged and your magnetic heading would change over time.
 
Clip4 said:
Yes. If you could fly a fixed straight line on the surface east to west in zero wind, you will be crossing different degrees of Variation and your true course would remain unchanged and your magnetic heading would change over time.
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You don't even need to get variation involved. Except for flying on North/South courses (or east west on the equator), the heading changes CONTINUALLY if you are flying a straight line course. Draw a line on a globe (or even a conformal projected chart like a sectional).
 
@Jaybird180 , what exactly is it you want to know? There's all kinds of talk here about what heading is needed to fly a line. Course, rhumb line, great circle, line over the ground, stuff like that. But this going to be a force from inside the plane choosing the heading to stay on that line, be it the pilot or the auto pilot. Wind, variation, declination, compass error and whatever else is going to affect the heading the pilot selects to fly. Is that what you meant? Or literally what you asked, "...Can an outside force (ie wind) change it's heading? How?..."
 
luvflyin said:
@Jaybird180 , what exactly is it you want to know? There's all kinds of talk here about what heading is needed to fly a line. Course, rhumb line, great circle, line over the ground, stuff like that. But this going to be a force from inside the plane choosing the heading to stay on that line, be it the pilot or the auto pilot. Wind, variation, declination, compass error and whatever else is going to affect the heading the pilot selects to fly. Is that what you meant? Or literally what you asked, "...Can an outside force (ie wind) change it's heading? How?..."
Click to expand...
Very perceptive sir. I'll PM you.
 
luvflyin said:
@Jaybird180 , what exactly is it you want to know? There's all kinds of talk here about what heading is needed to fly a line. Course, rhumb line, great circle, line over the ground, stuff like that. But this going to be a force from inside the plane choosing the heading to stay on that line, be it the pilot or the auto pilot. Wind, variation, declination, compass error and whatever else is going to affect the heading the pilot selects to fly. Is that what you meant? Or literally what you asked, "...Can an outside force (ie wind) change it's heading? How?..."
Click to expand...
A constant heading won't result in a straight line except in the degenerate cases I mentioned. It doesn't matter if you're doing true or magnetic or what the variation, declination, etc... is.
 
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