The downwind turn myth

Martin Pauly

Martin Pauly

Line Up and Wait
PoA Supporter
Joined
Dec 27, 2011
Messages
885
Location
Cedar Rapids, IA
Display Name
Display name:
Martin Pauly
Doug Rozendaal and I recorded another chat - this time about the downwind turn - specifically the myth that one loses airspeed when turning from upwind to downwind.

- Martin

 
Well, you do lose airspeed, in just about every turn, unless you make an adjustment.
 
Notwithstanding Ed's comment about loss of airspeed in a turn, I didn't know that people thought that to begin with. An old wive's tale I apparently missed. But if Martin and Doug discuss this in a video, I'm pretty sure it's worth watching.
 
write-stuff said:
Notwithstanding Ed's comment about loss of airspeed in a turn, I didn't know that people thought that to begin with. An old wive's tale I apparently missed.
Click to expand...
It's still out there, and some people pick it up and believe it.
 
write-stuff said:
Notwithstanding Ed's comment about loss of airspeed in a turn, I didn't know that people thought that to begin with. An old wive's tale I apparently missed. But if Martin and Doug discuss this in a video, I'm pretty sure it's worth watching.
Click to expand...
Dan Thomas said:
It's still out there, and some people pick it up and believe it.
Click to expand...

The same people that have trouble distinguishing the difference between airspeed and ground speed, and how it does or doesn't affect the plane.
 
It’s interesting the twists those downwind turn conversations take…it happens close to the ground, but not at 10,000 feet because at that point it’s not which way the air is moving with respect to the earth, but which way it’s moving with respect to space. :rolleyes:
 
Hey, it’s right there in rule 18. Can’t you guys read? Can’t think of any other reason why you’d crash other than losing airspeed. Just sayin.

Hafta admit, rule 21 caught me off guard, guess I gotta quit doing that… hmmm.

Nothing about assless chaps, guess I’m good.

Ya, y’all are welcome for that visual! Ha!
 
Tools said:
Hey, it’s right there in rule 18. Can’t you guys read?
Click to expand...
But it doesn’t say it’s because of the change from headwind to tailwind.
Hafta admit, rule 21 caught me off guard, guess I gotta quit doing that… hmmm.
Click to expand...
You can keep wearing the chaps if you like, though.

I was once told that the early Lears have a limitation against wearing cowboy boots (not specifically, but heels above a certain height.)
 
write-stuff said:
Notwithstanding Ed's comment loss of airspeed in a turn, I didn't know that people thought that to begin with. An old wive's tale I apparently missed. But if Martin and Doug discuss this in a video, I'm pretty sure it's worth watching.
Click to expand...
For real. Any time you can get doug rozendaal talking is worth a watch. The videos on "the drill" are solid gold. Basically all the ground school needed for an amel rating lol.
 
Jim K said:
For real. Any time you can get doug rozendaal talking is worth a watch. The videos on "the drill" are solid gold. Basically all the ground school needed for an amel rating lol.
Click to expand...
I'm proud to say I name dropped Doug during my AMEL checkride - though the DPE's response was "who?" - shame shame. I'm a big big fan of Dougs (and Martin of course).

I'll chime in here as well whilst scratching the top of my head - don't pilots learn about this effect during ground reference maneuvers for the PPL? It also has an impact on IAS until the system normalizes in the "new wind" and "flight" condition. If it still doesn't make sense, I encourage you all to go sailing where the wind has a much greater impact than flying.
 
Tools said:
assless chaps
Click to expand...
I only wear fully assed chaps. Some people call them pants, but I prefer the former.

MauleSkinner said:
I was once told that the early Lears have a limitation against wearing cowboy boots (not specifically, but heels above a certain height.)
Click to expand...
That's easy to believe. I once attempted a flight lesson in the archer wearing my size 13 steel toed work boots. After that I did the Mr. Rogers shoe change routine in the fbo every time.
 
Dave Theisen said:
I seem to remember an article by Richard Collins professed it was true.
Click to expand...

Didn't see that, but I do recall it being mentioned by one of the celebrity CFIs on YouTube. I just figured he didn't know what he was talking about and discarded it as hogwash. I didn't realize it was a commonly-held myth.
 
YES!

This is an idiotic belief only held true by morons who think the plane is somehow attached to the ground.

I honestly don't understand how anyone can possibly believe this. If you're flying in a 30 knot headwind and start doing steep turns your IAS is *NOT* going to fluctuate through a 60 knot band. The plane, remember, doesn't interact with "wind" it's merely moving through it as a medium. It doesn't know if it's a 2,000 knot wind or a 0 knot wind. The earth itself is spinning at around 1,000 mph.. but the plane is oblivious to that as we're traveling relative to it, not the universe. Same with the plane, it's traveling relative to the air, not the ground. Boats travel relative to the water, not the ground or wind.

Anyone who doesn't believe this needs to watch video above, especially at 6:45. They go from 53 ground speed to 90 groundspeed with virtually no change in power or IAS. Proof. Really shouldn't even need proof but here we are. This is the same reason there are stupid people out there who get tripped up by the whole "plane on a treadmill" crap.
 
Jim K said:
...The videos on "the drill" are solid gold. Basically all the ground school needed for an amel rating lol.
Click to expand...

if only people knew that this information has been taught for a lot longer than that video has been out...........

don't get me wrong, that doug guy sounds like he'd be a great instructor, but the info isn't new. it was probably just new to people who didn't study for or get their multi but watched that video.
 
Tools said:
Hey, it’s right there in rule 18. Can’t you guys read? Can’t think of any other reason why you’d crash other than losing airspeed. Just sayin.

Hafta admit, rule 21 caught me off guard, guess I gotta quit doing that… hmmm.

Nothing about assless chaps, guess I’m good.

Ya, y’all are welcome for that visual! Ha!
Click to expand...
I tried not to google it. I really tried hard. And I really tried not to post it. But I have no will power. Sorry.

upload_2022-12-16_11-29-47.jpeg
 
OK, from a Newtonian mechanics perspective it's a total myth. But funny things happen when you throw human perception in the mix.

Not full scale aircraft, but it happened to me. Flying an RC glider (Goldberg Gentle Lady) just above the treetop level making the turn from upwind (after launch) back down wind, from my perspective it appeared that the airplane was accelerating so I started back on the stick. And more back. And, whoops, WTF?
By the time "stall/spin" registered in my brain it was too late.

Turning from base to final with a strong crosswind from behind, I can see the potential to try to make the turn look "right" and do the tighten up...
 
Capt. Geoffrey Thorpe said:
OK, from a Newtonian mechanics perspective it's a total myth. But funny things happen when you throw human perception in the mix.

Not full scale aircraft, but it happened to me. Flying an RC glider (Goldberg Gentle Lady) just above the treetop level making the turn from upwind (after launch) back down wind, from my perspective it appeared that the airplane was accelerating so I started back on the stick. And more back. And, whoops, WTF?
By the time "stall/spin" registered in my brain it was too late.

Turning from base to final with a strong crosswind from behind, I can see the potential to try to make the turn look "right" and do the tighten up...
Click to expand...

exactly, then add if the turn is below the pivotal altitude (remember that commercial maneuver) then the turn can look like a slipping turn so the pilot may inadvertently add inside rudder (skidded turn) to make it look like a more normal higher altitude turn. Or the other reason is the pilot add rudder is they are afraid of steep turn so instead of adding the bank they need the skid the plan around. Then we have the perfect set up of pulling back and inside rudder and the next thing we see is a Spin entry.

Looks a lot this or exactly like this..


Brian
 
eman1200 said:
if only people knew that this information has been taught for a lot longer than that video has been out...........

don't get me wrong, that doug guy sounds like he'd be a great instructor, but the info isn't new. it was probably just new to people who didn't study for or get their multi but watched that video.
Click to expand...
Not new, but also not presented so succinctly in any place I've ever seen. I'd like to fly a twin some day, but knew zero about them going into those videos; they answered a LOT of questions for me.

Sidebar; I was thinking about how long we (as a species) have been flying twins, and it occurred to me that the Wright Flyer had two props. Would that be considered a twin? If one of those chains broke, how much effect would the asymmetric thrust have? Are there any more modern examples of a single powerplant driving multiple props? So many questions...
 
eman1200 said:
if only people knew that this information has been taught for a lot longer than that video has been out...........

don't get me wrong, that doug guy sounds like he'd be a great instructor, but the info isn't new. it was probably just new to people who didn't study for or get their multi but watched that video.
Click to expand...
Agreed…not new. But presented from a perspective of experience rather than rote knowledge, which adds a lot of nuance and connection of certain dots that the majority of multi training doesn’t include.
 
When turning from upwind to downwind near the ground, it's the perception of a slip that causes the problem, as Brian pointed out. It makes the pilot want to add rudder, and gets a skid.

Go up with another pilot on a windy (but smooth) day, put the foggles on, and do turns under the hood and see if you can tell which way you're pointing relative to the wind. See if the airspeed fluctuates. See if the ball wanders.

Gravity only works in the vertical. It cannot affect you laterally. The weight of the airplane has momentum relative to space itself, and since the earth and solar system and galaxy are travelling though space at terrific velocity (around 870,000 MPH) any changes in direction or velocity relative to this, at our puny speeds, will not cause anything detectable. The turn would have to be instantaneous to present any problems.
 
Last edited:
Capt. Geoffrey Thorpe said:
OK, from a Newtonian mechanics perspective it's a total myth. But funny things happen when you throw human perception in the mix.
Click to expand...
Right, the downwind turn problem as a physical thing is only believed by people who don't understand high school physics. But as a perceptual thing it's very real.

Fly a 20mph paramotor in a 10mph breeze and the "fish in the river" thing becomes very real and obvious. But interestingly, paramotors are affected by wind direction in some cases: If you're close to the ground it takes more power to fly level downwind than upwind (paramotors fly at a constant speed and have no pitch control, so the throttle is what determines climb, descent, or level flight). Due to wind gradient from friction with the ground, the airspeed seen by the pilot/motor may be different from that seen by the wing and thus require more (downwind) or less (upwind) power.
 
Velocity173 said:
Didn’t watch the vid but this goes back to the famous Barry Schiff argument. Yes, in a steady state wind only your ground speed will change. But, in the case of wind shear, your indicated airspeed can change.
Click to expand...
Sure, when climbing or descending brings the airplane into different wind, then that results in a momentary change of airspeed until the trimmed speed is achieved again. But that wasn't the topic of the video. This video and the people who have fallen for the downwind turn myth talk about level flight and constant wind, and they still believe the airspeed will decline when turning downwind, bringing the airplane closer to a stall.

- Martin
 
No Ag pilots here? They know what it’s about. So do guys who live in the low, slow, and short ops world. We fly airplanes in close proximity to the ground by ground reference and many times with lateral obstructions. Downwind turns within a restricted space can be very dangerous.
 
Stewartb said:
No Ag pilots here? They know what it’s about. So do guys who live in the low, slow, and short ops world. We fly airplanes in close proximity to the ground by ground reference and many times with lateral obstructions. Downwind turns within a restricted space can be very dangerous.
Click to expand...
Because of visual perceptions and Pilot reactions, not simply airspeed change due to turning downwind.
 
Jim K said:
I only wear fully assed chaps. Some people call them pants, but I prefer the former.


That's easy to believe. I once attempted a flight lesson in the archer wearing my size 13 steel toed work boots. After that I did the Mr. Rogers shoe change routine in the fbo every time.
Click to expand...

Hey… I saw you at Sporty’s. Are you sure those are only size 13’s! Would it be cheaper just to wear the boxes?

:lol:
 
Martin Pauly said:
Sure, when climbing or descending brings the airplane into different wind, then that results in a momentary change of airspeed until the trimmed speed is achieved again. But that wasn't the topic of the video. This video and the people who have fallen for the downwind turn myth talk about level flight and constant wind, and they still believe the airspeed will decline when turning downwind, bringing the airplane closer to a stall.

- Martin
Click to expand...

Doesn’t have to be climbing or descending but sure, you can get wind shear with a change in altitude (inversion layer). As far as the myth you describe, I’ve never heard of this being widespread. If someone believes that, they need to call their CFI and get a refund on their training.
 
Great video Martin.

it’s truly amazing how some of these myths continue
 
A guy last week told me that a headwind erroneously indicates high on the ASI because the air is blowing into the tube faster.
 
You must log in or register to reply here.
Back
Top