Downwind turn Myth
#1501
My Feedback: (4)
Interesting link. For me, these threads are a study in human psychology, or communications or something. Something about a counter-intuitive reality (airspeed vs groundspeed in this case) can generate such a back and forth. There is something inherent in the question and the basic counter-inuitive explanation that creates such a rich breeding ground for outrageous posts.
FWIW, in my experience, misjudgment of ground TRACK in the landing pattern (in a base leg cross wind favoring the rear of the model) causes many problems. The model needs more bank (and therefore more elevator and AoA) to establish proper ground track on final and poof.
FWIW, in my experience, misjudgment of ground TRACK in the landing pattern (in a base leg cross wind favoring the rear of the model) causes many problems. The model needs more bank (and therefore more elevator and AoA) to establish proper ground track on final and poof.
The concept is taught in primary full scale flight training world and it relates directly to us. They teach how flying a ground reference maneuver (exactly what we're doing) is effected by wind, and the resultant control inputs required. There are an almost infinite number of examples, diagrams and data that prove this.
For all the folks that believe this myth, there is preponderance of information that explains exactly what is going on & and is easily be verified through multiple sources with Google or any other search engine in seconds. Yet they can't provide ANY credible data to the contrary all the while refusing to even entertain the possibility that they may be in fact incorrect.
#1502
My Feedback: (1)
wind affects an aircraft only while the wheels are on the ground or you are navigating. a steady head wind doesn't increase lift, a tailwind doesn't decrease lift, a steady wind won't push you or cause you to stall in a turn. it will cause your ground speed to be different than your airspeed, your ground track to be different than your heading and your climb angle to vary depending on the direction of travel in relation to the wind. its not magic but it can be very counterintuitive.
#1507
My Feedback: (4)
wind affects an aircraft only while the wheels are on the ground or you are navigating. a steady head wind doesn't increase lift, a tailwind doesn't decrease lift, a steady wind won't push you or cause you to stall in a turn. it will cause your ground speed to be different than your airspeed, your ground track to be different than your heading and your climb angle to vary depending on the direction of travel in relation to the wind. its not magic but it can be very counterintuitive.
#1509
My Feedback: (4)
The plane ONLY cares about wind in reference to the ground i.e take off and landing (x-wind component-you have to line up with the runway) & navigating (you have to arrive at the airport at some time) which ironically is on the ground! In free flight steady state wind has no effect on the airplane, only ground speed and track. The plane always sees the same IAS. Ground speed and course change with the wind.
#1510
#1511
Senior Member
#1512
My Feedback: (57)
Quoting my own post from January of last year:
I've already done exactly this! I fly UAV's for a living. By nature they navigate via GPS waypoints (ground reference manuvers!) and are very highly instrumented! When turning downwind to final, or upwind to downwind, (our wind limits are 35 kts, which I've flown in many times) there is no change in IAS, ground speed changes of course, but not indicated. Your argument has no credibility. I have telemetry files to back it up.
Once again you are not grasping the issue at hand here, microbursts are NOT steady state wind, which is what this thread is about.
I've already done exactly this! I fly UAV's for a living. By nature they navigate via GPS waypoints (ground reference manuvers!) and are very highly instrumented! When turning downwind to final, or upwind to downwind, (our wind limits are 35 kts, which I've flown in many times) there is no change in IAS, ground speed changes of course, but not indicated. Your argument has no credibility. I have telemetry files to back it up.
Once again you are not grasping the issue at hand here, microbursts are NOT steady state wind, which is what this thread is about.
And mine is not a quad either, but a 500 pounder.
#1513
Nice to finally see some common sense (Lownverted, cfircav8r, M3Baker) to name a few.
Exactly: Once airborne a fixed wing airplane does not recognise a moving air mass - period. Other phenomena such as turbulence caused by gusts, mountain waves, microbursts are rapid and sudden changes and the effects are obvious.
However, for those who have flown Helicopters (rotor wings), will know that the wind does have an effect once airborne, and below transitional lift.
Exactly: Once airborne a fixed wing airplane does not recognise a moving air mass - period. Other phenomena such as turbulence caused by gusts, mountain waves, microbursts are rapid and sudden changes and the effects are obvious.
However, for those who have flown Helicopters (rotor wings), will know that the wind does have an effect once airborne, and below transitional lift.
#1514
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You are on the right track, but have taken a slight detour.
A round loop will look round regardless of the wind and it's not "risky" to fly pattern in the wind. The cut off for competition is 12 m/s which is 43.2 KMH or 26.8 MPH.
If you are flying some sort of weird egg shaped ellipse with a long narrow end, then that's exactly how it will look. Flying pattern, the loop is performed in reference to the centre pole and must be central to that reference, regardless of how windy it is to score well. Just because the wind is blowing from say left to right, doesn't mean the loop will move left to right with the wind. The loop will stay central to the fixed point, which in this case is the centre pole. What does change is the attitude of the plane, but the flight path is still round. The CG of the plane must describe a round flight path, not the thrust line.
If it is windy and the plane is wind corrected, then the loop may appear to be not round, but the CG of the plane will follow the round loop. This is where experience in flying and judging pattern comes into play.
As per the FAI Sporting Code, Section 4, Annex 5B.8.4, "A loop must have by definition, a constant radius, and be performed in the vertical plane throughout".
This applies regardless of the wind. Trying to maintain constant speed, (which is another judging criteria), makes it harder again when it's windy.
I've been flying and judging pattern for 17 years and currently fly F3A class. Flying correct geometry in the wind isn't easy.
A round loop will look round regardless of the wind and it's not "risky" to fly pattern in the wind. The cut off for competition is 12 m/s which is 43.2 KMH or 26.8 MPH.
If you are flying some sort of weird egg shaped ellipse with a long narrow end, then that's exactly how it will look. Flying pattern, the loop is performed in reference to the centre pole and must be central to that reference, regardless of how windy it is to score well. Just because the wind is blowing from say left to right, doesn't mean the loop will move left to right with the wind. The loop will stay central to the fixed point, which in this case is the centre pole. What does change is the attitude of the plane, but the flight path is still round. The CG of the plane must describe a round flight path, not the thrust line.
If it is windy and the plane is wind corrected, then the loop may appear to be not round, but the CG of the plane will follow the round loop. This is where experience in flying and judging pattern comes into play.
As per the FAI Sporting Code, Section 4, Annex 5B.8.4, "A loop must have by definition, a constant radius, and be performed in the vertical plane throughout".
This applies regardless of the wind. Trying to maintain constant speed, (which is another judging criteria), makes it harder again when it's windy.
I've been flying and judging pattern for 17 years and currently fly F3A class. Flying correct geometry in the wind isn't easy.
I'm just suggesting that pilots be conscious of the different inputs required. Airspeed changes differently during the loop in wind if you try to make it look round from our stationary ground perspective. Airspeed will NOT be different in wind if you use the same control inputs that you use in calm, but it's going to look different (not round) from the ground. If you're a novice such that anything in this thread is new to you, you'd be SAFER flying your loops in wind with the same smooth, gentle control inputs that you use in dead calm. Be patient and observe the egg shape that occurs and learn from that observation before you try to make the loop round in wind the way a pattern pilot would.
Where I disagree with you is when you say it's just as "safe" to fly a loop in 25 MPH wind. Are you kidding?? It's extremely difficult to maintain airspeed over the top of that loop in 25MPH wind while still maintaining the same radius and center GROUND BASED reference point. This is the exact scenario that causes people to believe the MYTH and think that downwind robs airspeed. I doesn't, UNLESS you keep the same ground track like a pattern pilot.
Last edited by RZielin; 09-10-2015 at 03:18 AM.
#1520
Here is an experiment to try. Take your jet up to 350 feet and nose her over until she is going straight down, Adjust throttle and flight controls so that she is travelling straight down with all forces being equal. Clearly she has momentum with repsect to the ground. But just as clearly she has NO momentum with respect to the leading edge of the wing. Keep her pointed straight down and when when smacks into the gound tell me that momentum with respect to the ground doesn't matter.
#1521
Don't like that one? Okay, try this. Same scenario but instad of lettign her smack into the ground yank hard on the elevator so as to pull out just before she hits the ground. Now when the wings get ripped off tell me that is because she had zero momentum with respect to the leading edge.
#1522
OH MY!!!
I liked the provided analogy of; "Draw a loop on a piece of paper. Then do it with your eyes closed till you can consistently make a fairly round loop. THEN do the same thing as someone else slowly pulls the paper sideways."
I wish I made my living in an Airbus... that's got to be spectacular, with tons of responsibility/stress.
I liked the provided analogy of; "Draw a loop on a piece of paper. Then do it with your eyes closed till you can consistently make a fairly round loop. THEN do the same thing as someone else slowly pulls the paper sideways."
I wish I made my living in an Airbus... that's got to be spectacular, with tons of responsibility/stress.
#1523
My Feedback: (6)
Here is an experiment to try. Take your jet up to 350 feet and nose her over until she is going straight down, Adjust throttle and flight controls so that she is travelling straight down with all forces being equal. Clearly she has momentum with repsect to the ground. But just as clearly she has NO momentum with respect to the leading edge of the wing. Keep her pointed straight down and when when smacks into the gound tell me that momentum with respect to the ground doesn't matter.
#1524
My Feedback: (4)
Here is an experiment to try. Take your jet up to 350 feet and nose her over until she is going straight down, Adjust throttle and flight controls so that she is travelling straight down with all forces being equal. Clearly she has momentum with repsect to the ground. But just as clearly she has NO momentum with respect to the leading edge of the wing. Keep her pointed straight down and when when smacks into the gound tell me that momentum with respect to the ground doesn't matter.
#1525
My Feedback: (4)
Calculate the momentum of a plane flying due east at a particular airspeed on a calm day. Then make the same calculation flying due west at the same speed. Calculate the difference. Now do the same thing but with a steady east or west wind. You'll get the same difference.