Go Back  RCU Forums > RC Airplanes > RC Jets
Reload this Page >

Downwind turn Myth

Notices
RC Jets Discuss RC jets in this forum plus rc turbines and ducted fan power systems

Downwind turn Myth

Old 09-09-2015, 03:13 PM
  #1501  
Lownverted
My Feedback: (4)
 
Lownverted's Avatar
 
Join Date: Aug 2002
Location: Palmdale, CA
Posts: 549
Received 6 Likes on 6 Posts
Default

Originally Posted by mr_matt
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.
You've got it nailed. Somebody tries to make the ground track look the same in wind as it does without. The results can be disastrous.

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.
Old 09-09-2015, 03:14 PM
  #1502  
cfircav8r
My Feedback: (1)
 
cfircav8r's Avatar
 
Join Date: Jul 2004
Location: Hampton, IA
Posts: 1,242
Likes: 0
Received 1 Like on 1 Post
Default

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.
Old 09-09-2015, 03:15 PM
  #1503  
Lownverted
My Feedback: (4)
 
Lownverted's Avatar
 
Join Date: Aug 2002
Location: Palmdale, CA
Posts: 549
Received 6 Likes on 6 Posts
Default

Originally Posted by rgburrill
The process of a turn is also not steady state wind. Your quads are very highly manueverable and are not at all representive of a winged aircraft.
BTW, show the tlemetry plots! Prove it.

Who said it was a quad? Fixed wing actually, 200 lbs in this example. An yes it is absolutely in steady state wind.
Old 09-09-2015, 03:16 PM
  #1504  
Lownverted
My Feedback: (4)
 
Lownverted's Avatar
 
Join Date: Aug 2002
Location: Palmdale, CA
Posts: 549
Received 6 Likes on 6 Posts
Default

Originally Posted by chip_MG
If wind speed makes not difference then why do all full scale aircraft manuals state a maximum cross wind component, meaning it's not safe to fly at all if winds are higher?

That's for takeoff and landing which is (surprise!!) a ground reference maneuver. C'mon guys this is simple,......
Old 09-09-2015, 03:19 PM
  #1505  
drac1
My Feedback: (4)
 
drac1's Avatar
 
Join Date: Jul 2008
Location: Romaine, Tasmania, AUSTRALIA
Posts: 1,736
Received 7 Likes on 7 Posts
Default

Originally Posted by mr_matt
HUH? ALL of the comments say that windspeed affects aircraft groundspeed. You are saying the same thing.
HUH? NOT all the comments are about ground speed. Someone posted that the plane doesn't care about wind. I was just saying that the plane does care about wind.

Of course wind affects ground speed.
Old 09-09-2015, 03:19 PM
  #1506  
Lownverted
My Feedback: (4)
 
Lownverted's Avatar
 
Join Date: Aug 2002
Location: Palmdale, CA
Posts: 549
Received 6 Likes on 6 Posts
Default

Originally Posted by drac1
If wind has no effect on the aircraft, why does everyone, (full scale and models), take off and land into the wind?
Jeez do people even read?

Once again its to shorten the take off and landing roll. Nothing else. Again.....ground reference maneuver. Seriously people...Google just a little......
Old 09-09-2015, 03:21 PM
  #1507  
Lownverted
My Feedback: (4)
 
Lownverted's Avatar
 
Join Date: Aug 2002
Location: Palmdale, CA
Posts: 549
Received 6 Likes on 6 Posts
Default

Originally Posted by cfircav8r
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.
Exactly......
Old 09-09-2015, 03:22 PM
  #1508  
cfircav8r
My Feedback: (1)
 
cfircav8r's Avatar
 
Join Date: Jul 2004
Location: Hampton, IA
Posts: 1,242
Likes: 0
Received 1 Like on 1 Post
Default

Originally Posted by drac1
HUH? NOT all the comments are about ground speed. Someone posted that the plane doesn't care about wind. I was just saying that the plane does care about wind.

Of course wind affects ground speed.
no the pilot cares, as he is the one trying to navigate, the plane is not affected in the least
Old 09-09-2015, 03:24 PM
  #1509  
Lownverted
My Feedback: (4)
 
Lownverted's Avatar
 
Join Date: Aug 2002
Location: Palmdale, CA
Posts: 549
Received 6 Likes on 6 Posts
Default

Originally Posted by drac1
HUH? NOT all the comments are about ground speed. Someone posted that the plane doesn't care about wind. I was just saying that the plane does care about wind.

Of course wind affects ground speed.
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.
Old 09-09-2015, 04:07 PM
  #1510  
M3Baker
 
M3Baker's Avatar
 
Join Date: Feb 2010
Location: Goldsboro, NC
Posts: 309
Likes: 0
Received 1 Like on 1 Post
Default

Originally Posted by mr_matt
Lower ground speed and needs less runway
Also allows you more time to clear an obstacle. Lower ground speed allows more time to gain altitude.

Jeeze, I can't believe I'm posting on this thread.
Old 09-09-2015, 05:10 PM
  #1511  
KC Air
Senior Member
 
Join Date: Jun 2015
Location: Kansas City
Posts: 115
Likes: 0
Received 1 Like on 1 Post
Default

Originally Posted by M3Baker
Also allows you more time to clear an obstacle. Lower ground speed allows more time to gain altitude.

Jeeze, I can't believe I'm posting on this thread.
The thread is like an auto accident.. you don't want to see it, but you can't help but look.
Old 09-09-2015, 05:29 PM
  #1512  
George
My Feedback: (57)
 
Join Date: Dec 2001
Location: Va Beach, VA
Posts: 3,069
Likes: 0
Received 12 Likes on 11 Posts
Default

Originally Posted by Lownverted
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.
+1
And mine is not a quad either, but a 500 pounder.
Old 09-09-2015, 05:37 PM
  #1513  
darryltarr
My Feedback: (2)
 
darryltarr's Avatar
 
Join Date: Nov 2002
Posts: 269
Likes: 0
Received 1 Like on 1 Post
Default

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.
Old 09-09-2015, 05:40 PM
  #1514  
RZielin
Member
My Feedback: (1)
 
Join Date: Jun 2009
Location: Madbury, NH
Posts: 73
Likes: 0
Received 0 Likes on 0 Posts
Default

Originally Posted by drac1
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.
I'm not sure where you're disagreeing with me, or where I'm "off track". You just repeated my post using different words. We agree (almost) completely. My point is that for the loop to remain in reference to the center pole, and not drift with the wind, and maintain a constant radius in the wind, the pilot must use different control inputs than in dead calm. Those same control inputs used in the "windy" loop would trace an egg shaped loop if done in dead calm. The converse is also true: using the inputs appropriate for dead calm will cause the loop to appear egg shaped and drift downwind if done without modification in wind.

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.
Old 09-09-2015, 09:39 PM
  #1515  
highhorse
Thread Starter
My Feedback: (2)
 
highhorse's Avatar
 
Join Date: Nov 2006
Location: Memphis, TN
Posts: 2,564
Received 93 Likes on 49 Posts
Default

Originally Posted by M3Baker
Also allows you more time to clear an obstacle. Lower ground speed allows more time to gain altitude.

Jeeze, I can't believe I'm posting on this thread.
Resistance is futile. You will be assimilated.
Old 09-09-2015, 11:58 PM
  #1516  
drac1
My Feedback: (4)
 
drac1's Avatar
 
Join Date: Jul 2008
Location: Romaine, Tasmania, AUSTRALIA
Posts: 1,736
Received 7 Likes on 7 Posts
Default

Originally Posted by Lownverted
Jeez do people even read?

Once again its to shorten the take off and landing roll. Nothing else. Again.....ground reference maneuver. Seriously people...Google just a little......
Seriously you....

If YOU read all the posts and come up with the correct meaning and context, you would know that was a leading question to another post.

Try to keep up just a little.
Old 09-10-2015, 05:38 AM
  #1517  
paladin
My Feedback: (9)
 
Join Date: Feb 2002
Location: Vestal, NY
Posts: 2,921
Received 6 Likes on 6 Posts
Default

I'm amazed!!!!

if you have not figured it out yet this is just a place for a few to poke fun at the many.

Joe
Old 09-10-2015, 05:51 AM
  #1518  
Lownverted
My Feedback: (4)
 
Lownverted's Avatar
 
Join Date: Aug 2002
Location: Palmdale, CA
Posts: 549
Received 6 Likes on 6 Posts
Default

Originally Posted by drac1
Seriously you....

If YOU read all the posts and come up with the correct meaning and context, you would know that was a leading question to another post.

Try to keep up just a little.
I've been here from the very beginning and have kept up just fine, but believe what you want.
Old 09-10-2015, 05:53 AM
  #1519  
Jaybird
Senior Member
 
Join Date: Jul 2002
Location: Brunswick, ME
Posts: 1,192
Likes: 0
Received 0 Likes on 0 Posts
Default

What???? This whole thread is just one big prank???? Well, you got me.

Jaybird
Old 09-10-2015, 07:04 AM
  #1520  
rgburrill
 
rgburrill's Avatar
 
Join Date: Dec 2010
Location: Dallas, Tx CT
Posts: 2,857
Received 76 Likes on 67 Posts
Default

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.
Old 09-10-2015, 07:07 AM
  #1521  
rgburrill
 
rgburrill's Avatar
 
Join Date: Dec 2010
Location: Dallas, Tx CT
Posts: 2,857
Received 76 Likes on 67 Posts
Default

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.
Old 09-10-2015, 09:03 AM
  #1522  
cowboy69
 
cowboy69's Avatar
 
Join Date: Dec 2014
Location: UTAH
Posts: 133
Received 0 Likes on 0 Posts
Default

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.
Old 09-10-2015, 09:04 AM
  #1523  
Top_Gunn
My Feedback: (6)
 
Join Date: Jun 2005
Location: Granger, IN
Posts: 2,344
Received 6 Likes on 5 Posts
Default

Originally Posted by rgburrill
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.
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.
Old 09-10-2015, 10:16 AM
  #1524  
Lownverted
My Feedback: (4)
 
Lownverted's Avatar
 
Join Date: Aug 2002
Location: Palmdale, CA
Posts: 549
Received 6 Likes on 6 Posts
Default

Originally Posted by rgburrill
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.
Lol! What point are you trying to argue again and why is it relevant?
Old 09-10-2015, 10:16 AM
  #1525  
Lownverted
My Feedback: (4)
 
Lownverted's Avatar
 
Join Date: Aug 2002
Location: Palmdale, CA
Posts: 549
Received 6 Likes on 6 Posts
Default

Originally Posted by Top_Gunn
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.
Ding ding ding......

Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service -

Copyright © 2024 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.