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Why's and How's of a Coordinated Turn


Bearfoot

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Thanks! Yes, to be honest I don't know whether my explanation explains it or not. I fly Cessnas, and I've certainly never seen that behavior, not that I could apply enough angle of bank that quickly to mimic that in a Cessna, although now I think next weekend I might just give it a test, lol. It'd be interesting to hear Victory 205's take, and tell me if I'm full of shit or not, lol.  

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At 3:11, a similar demonstration to my video. The ball moves accordingly with adverse yaw. I think this supports the findings in my video that the ball is behaving oppositely to how it should during roll in the DCS F-14.

 


Edited by Callsign JoNay
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http://www.heatblur.se/F-14Manual/cockpit.html#air-combat-maneuver-panel

Quote

#14 - Turn-and-Slip indicator

Indicator showing rate of turn around aircraft vertical axis.
The upper part contains an electrically driven pointer, one needle deflection equalling a 360° turn in 4 minutes.
The lower part contains an inclinometer with a ball suspended in a dampening fluid.
Even NATOPS does not mention much more than that.

Edited by draconus

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5 hours ago, Spartan111sqn said:

I guess a proppeller behaviour is different than in a jet.

I though that in Tomcat the above indicator reflects the nose and the below one the tail of the plane...


I’m not 100% sure as I never flew the Tomcat in real life, but that is almost certainly wrong. The top part is turn rate, and the ball is the inclinometer (shows slips/skids). At least that’s how every other aircraft I know works

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16 hours ago, Spartan111sqn said:

I guess a proppeller behaviour is different than in a jet.

I though that in Tomcat the above indicator reflects the nose and the below one the tail of the plane...


Ooh, no, it’s the exact same instrument. Basic flight instruments haven’t changed in 80 years, and they’re the same whether you’re flying a Skyhawk, a Mustang, a Tomcat or a 747. 

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I only have experience in sims flying viper and hornet..., so at the end I have to see the below needle and step on the ball, right?, so in navigation flying in Tomcat is needed to use rudder according to the instrument indication or rudder is only for high AoA?

 

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The Tomcat is more like a Warbird than it is a Hornet or a Viper as far as stick and rudder skills go. You need to use the rudder. You need to use the rudder as the primary means of lateral control (rudder first, augment with stick) above 20 units AOA. At the end of the day it’s a jet and not a prop, so you’re not going to need as much rudder as you would a Cessna or a Christen Eagle, but it becomes critical in certain flight regimes. 

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Former USN Avionics Tech

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VF-101 90-93

 

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There is nothing wrong with how F-14 behaves in roll/yaw or with the turn and slip indicator. The F-14s roll control is provided by spoilers and diff. stabilator deflections (not ailerons) which causes F-14 to exhibit proverse yaw. Which means on for example left roll, the spoilers on left wing pop up reducing lift on this wing relative to right wing so the aircraft will roll left. But spoilers not only dump lift, they will also increase drag on the left wing so the the aircraft will yaw to the left, which means that the ball inside the slip indicator will move to the opposite side (right).

OK that is initial roll into turn, now that we are established in bank we center the stick lowering the spoilers flush with left wing again cancelling the roll and by that also canceling the proverse yaw. Which means the aircraft want will swing its nose back due to yaw torque of the vert. stabs. Now it just behaves like any other aircraft and depending on speed and configuration it will need a little rudder into the turn to center the ball (more so when slow and configured for landing).

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3 hours ago, Golo said:

There is nothing wrong with how F-14 behaves in roll/yaw or with the turn and slip indicator. The F-14s roll control is provided by spoilers and diff. stabilator deflections (not ailerons) which causes F-14 to exhibit proverse yaw. Which means on for example left roll, the spoilers on left wing pop up reducing lift on this wing relative to right wing so the aircraft will roll left. But spoilers not only dump lift, they will also increase drag on the left wing so the the aircraft will yaw to the left, which means that the ball inside the slip indicator will move to the opposite side (right).

OK that is initial roll into turn, now that we are established in bank we center the stick lowering the spoilers flush with left wing again cancelling the roll and by that also canceling the proverse yaw. Which means the aircraft want will swing its nose back due to yaw torque of the vert. stabs. Now it just behaves like any other aircraft and depending on speed and configuration it will need a little rudder into the turn to center the ball (more so when slow and configured for landing).

It's not doing that in DCS World though. Watch my video again. I align the wing symbol with the peak of a mountain, roll back and fourth and each time there is adverse yaw present, not proverse. It's right there to see in slow motion.

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1 hour ago, Callsign JoNay said:

roll back and fourth

What exactly do you think you are achieving by doing that? You will figure out exactly nothing looking at the indicator, only thing you are doing is oversaturating it, so it shows BS. Roll smoothly once to either side up to 60° and observe the ball (it will move opposite of direction of the roll) then rollout wings level and try again.

 

Edit: I can see from your video at 07s on your first left roll that the ball moves opposite as it should.


Edited by Golo
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23 minutes ago, Golo said:

What exactly do you think you are achieving by doing that? You will figure out exactly nothing looking at the indicator, only thing you are doing is oversaturating it, so it shows BS. Roll smoothly once to either side up to 60° and observe the ball (it will move opposite of direction of the roll) then rollout wings level and try again.

 

Edit: I can see from your video at 07s on your first left roll that the ball moves opposite as it should.

 

 

Ignore the ball and look out the window. You said the F-14 should generate proverse yaw in roll onset because of the wing spoiler. It does not do that in DCS. It's adverse yaw.

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1 hour ago, Jayhawk1971 said:

 

 

Yeah so you can see it in that video too. Roll to the right, the nose yaws to the left. (Slip/Adverse Yaw). But the ball also goes left. Etc.

 

Edit: Oh I should've kept watching. I see now what's going on. I'm using the wing symbol as my reference but I should be using the datum instead.


Edited by Callsign JoNay
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2 hours ago, Callsign JoNay said:

It's not doing that in DCS World though. Watch my video again. I align the wing symbol with the peak of a mountain, roll back and fourth and each time there is adverse yaw present, not proverse. It's right there to see in slow motion.

HI.

What you see in your video moving adverse to the roll, the bars with a dot in the middle  (in the HUD) is not where the longitudinal axis is pointing at: it is slightly under the axis, so as you roll left, the upper posrtion of the HUD moves CCW/to the left and the lower portion, also CCW but to the right, creating the effect that there is an adverse yaw, but you should look  at a place between the wing mark and the gun cross, witch is the correct axis projection.

I hope I made myself clear!

Saca111

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On 6/9/2021 at 8:05 AM, Spartan111sqn said:

I only have experience in sims flying viper and hornet..., so at the end I have to see the below needle and step on the ball, right?, so in navigation flying in Tomcat is needed to use rudder according to the instrument indication or rudder is only for high AoA?

 

Ideally you always add rudder inputs to your rolls, and during high performance non-vertical turns, rudder inputs are must to avoid wing drop. Which though a year late (not that i could do it at the time) brings me to one of the most important reasons why coordinating is tactically important...... it's practically the only way to ride the stall, or max-perform you plane. Look at the AoA values bellow (true degrees), you can't do this without proper rudder inputs.

Now, this doesn't mean you should always do these bat-turns, but there are times when they are needed. And yes, the main and aux flaps weren't dropped during these tests, only maneuver flaps on auto.

 

f-14 AoA 1.jpg

f-14 AoA 2.jpg

f-14 AoA 3.jpg

f-14 AoA 4.jpg

f-14 AoA 5.jpg

f-14 AoA 6.jpg

f-14 AoA 7.jpg

f-14 AoA 8.jpg

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  • 8 months later...

I have a set of VKB mk IV pedals, I have always felt something is not right with rudder setup in dcs. For example to centre the ball it feels like my input needs to be non-existent. If i step on rudder in the direction i'm turning its always to much despite being the most minute of inputs. I probably centre the ball better in a turn by not touching the pedals, Its almost like I have auto rudder applied in the sim but I don't.  I've tried applying curve but that does not help. If i start applying dead zone I loose precision.   

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6 hours ago, westr said:

I have a set of VKB mk IV pedals, I have always felt something is not right with rudder setup in dcs. For example to centre the ball it feels like my input needs to be non-existent. If i step on rudder in the direction i'm turning its always to much despite being the most minute of inputs. I probably centre the ball better in a turn by not touching the pedals, Its almost like I have auto rudder applied in the sim but I don't.  I've tried applying curve but that does not help. If i start applying dead zone I loose precision.   

Use what is necessary. Most DCS aircraft don't need rudder for less than a standard rate coordinated turn, including the F14.

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10 hours ago, westr said:

I probably centre the ball better in a turn by not touching the pedals.

 

I too have mostly given up trying to coordinate turns during cruise speeds. Ever since they reworked the slip ball, its all over the place for me. I usually just agitate the ball even more if I try to coordinate with rudder. Most of my rudder use is reserved for slow speed or high alpha rolling now.

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