Number 3's Diamond Roll video

"How To" by our Pilot Staff
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Dr_Ripper
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Number 3's Diamond Roll video

Post by Dr_Ripper » Thu May 10, 2012 9:18 am

First off, that was an awesome video demonstration!



Your video was very insightful at demonstrating how you guys perform your barrel rolls and I have a few questions about the nature of the technique you guys use. I made a few observations on how I think you perform them and was wondering if you could please confirm them or correct them. Thanks!

Only moments before you begin rolling the formation, it seems that you release nearly (if not) all of the pull used for the initial climb. Then you accelerate to your full roll rate quite quickly (perhaps in the first 45 degrees?) and maintain it until about 270 degrees giving more time to the deceleration than you give towards the initial acceleration to aid in a smoother exit. On the exit, you seem to have quite a bit of pull in order to bring yourselves back to level flight. I was wondering that if all the above is correct, then you must be increasing the amount of pull during the roll? How exactly are you guys applying this and does it occur in a short period at some specific point during the roll or gradually (linearly/exponentially) throughout the duration?

Thanks in advance! :D
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Teej
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Re: Number 3's Diamond Roll video

Post by Teej » Thu May 10, 2012 12:37 pm

Doesn't sound far from accurate. We're just following the boss. :D

We've put up comms in and/or from our shows before, and you can follow through the roll pretty much with what you said. "Smoke on ready now nose coming up......rolling left and rolling......into the float......back in with the pull."

I would say we don't "release pull, then roll" though...it's a very fluid motion...similarly there's not _much_ pull being added at the end, but there definitely is some (fraction of a G worth I'd say). G builds more than what we add because speed is coming back up on the back side of the roll, plus we're coming back upright so we get God's G loading us up again....I'd say the amount we physically add with back pull is somewhere around 1/3 G, and probably less. It's a more subtle than what you think you're seeing - easy to miss when flying it if you don't expect it...but it's not a large change at all.
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Frazer
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Post by Frazer » Thu May 10, 2012 2:28 pm

One question remains, who or what is actually rolling? The earth...or the formation?
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Dr_Ripper
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Post by Dr_Ripper » Thu May 10, 2012 2:32 pm

Both.

Thanks Teej. :)
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Lawndart
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Post by Lawndart » Fri May 11, 2012 11:36 am

Trying to think of a way to summarize some objectives and what the Leader does with his hands throughout a roll. If I was home I'd record my stick movements in a video, but here's a description.

Objectives
  • Getting enough G before the roll by the target pitch angle (e.g. 2G @ 15 deg). This will help meet the target altitude at the apex and keep the front/back sides looking symmetrical.
  • Using a roll rate that allows apexing at or 2-4 deg above the horizon. The first 90 deg of roll uses an asymmetrical rate that's increasing to achieve this with the goal being to keep a uniform roll rate from ~90 deg through 270 deg of roll. (A Delta Roll vs. Diamond Roll uses a slower roll rate to accommodate the outer wingmen who need to arc/pull their way around the formation with exponentially larger stick deflection than the inner wingmen, but the same objective still applies for the Leader; to apex at or 2-4 deg above the horizon. What allows the roll rate to be slower in the Delta is the target pitch angle before the roll - e.g. 2G @ 22 deg. This also yields a different target altitude).
  • There are two more objectives that include the float and building up the G again on the backside as the roll rate is decelerated, and I'll explain this by the radio calls:
"NOSE COMING UP"
Leader begins adding back pressure with the goal of reaching 2.0-2.8Gs by the target pitch angle.

"ROLLING LEFT AND ROLLING"
Leader begins building up the roll rate with the goal of reaching maximum rate by 90 deg. Any unload or release of back pressure before the roll movement is purely unintentional; however...

"INTO THE FLOAT"
As the roll rate is being established the Leader eases forward on the stick ever so slightly, usually between 45 to 90 deg of bank. This helps achieve on top params as well as preserve airspeed and thereby maneuverability by the wingmen. The Leader has to be careful not to release too much back pressure or too quickly. Just breathe forward on the stick.

"BACK IN WITH THE PULL"
Approx at ~235 deg of roll the Leader begins to build up the G again very smoothly to match the onset and pitch angle of the front side. This call also serves to slow the roll rate gradually during the last quarter. The Leader begins adding an ounce of G before the 270-degree point and afterwards focuses more on slowing the roll rate while that ounce of back pressure and airspeed increasing builds up the G to a number approximately equal to the front half. The more important thing the Leader should look for (rather than G) is the lowest pitch angle, comparing it to the target pitch angle on the entry, to determine whether more or less G is required, and then "playing the bottom" to hit the exit altitude as the roll rate is diminished.


Summary

There's no intentional release of back pressure prior to the roll (other than possibly a fraction by the mechanics of moving the stick left to begin the roll).

The roll rate is increased during the first 90 deg of roll and slowed down during the last 270 deg of roll. The rate acceleration/deceleration depends on the pitch angle and apex, so it's not necessary for the frontside to match the backside in that regard. The objective for the Leader is making the roll appear uniform to the crowd, even if that means it was sped up faster than it was slowed down. Typically you'd have a lengthier roll rate deceleration on the backside since the objective is to apex at or above the horizon (never below) over the top.

The toughest part in a roll is for the left wingmen around the 270-degree point when they have to shift their light forward pressure/float and begin adding back pressure again while being properly cupped/toed to not drift while the light push becomes a pull instead. (The right wingman's toughest part is anticipating the roll and not letting himself get deep at the start when the formation starts rolling away from him, but it never requires a diametrically opposed control input at any point during the roll).
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Dr_Ripper
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Post by Dr_Ripper » Sun May 13, 2012 5:14 pm

Wow, that was beautifully concise and fascinating. Thank you very much for taking the time to explain! :D :D :D
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