F3N Piro globe double reversed

[richardv]

"MA enters in upright flight and then performs four pirouetting loops. During each loop, the flight path is changed continually in a way that the low point is passed rotated about 45° (seen from above) until a complete globe has been described.
After each loop the pirouetting direction is changed at the bottom of the loop. MA performs on every top of the loop a half roll in either direction while still performing pirouettes. The MA exits the manoeuvre at the same altitude but in opposite direction to the beginning. During each loop, the MA must perform at least two pirouettes."

My question is around the roll at the top. I've seen a few versions and I have no idea what's correct.

a) The piro stops with the heli travelling sideways, performs a half roll in the direction of travel and then continues pirouetting.

b) The piro stops with the heli travelling forwards, performs a half roll at 90 degrees to the direction of travel and then continues pirouetting.

c) While pirouetting continuously, a piro flip is performed in the direction of travel, starting and ending with the model travelling sideways.

d) While pirouetting continuously, a piro flip is performed at 90 degrees to the direction of travel, staring and ending with the model travelling forwards/backwards.

D seems the most correct to me, but I don't know what the judges are expecting.

[Steve Graham]

This is a really interesting example of the challenge of creating clear but concise maneuver descriptions when a maneuver becomes too complex. It is further complicated when it leaves out mathematical notations.

On first glance I'd argue the goal is simply to have the model transition from inverted at the apex of the first loop to upright. This transforms the loop from an inside (disc in) to an outside (disc out) maneuver. It requires the pilot demonstrate proficiency in both types of piro loop.

Since the description indicates the model continues to piro while rolling I suggest neither A nor B can be correct.

The description only specifies the pilot must perform at least 2 piros per loop. I'd take this to mean that the pilot is free to choose higher rotation rates. A fundamental tenet of precision aerobatics is consistent roll and piro rates as well as things like arc radii. Therefore I'd suggest the piro rate the pilot chooses would dictate whether the model was in forward or sideways flight at the beginning of the piro roll/flip. For example if the pilot chose any whole number of piros per loop the model would be in either forwards OR backwards flight at the apex. If the pilot chose any other ratio of piro's per loop the model would be in something other than forwards/backwards flight at the apex. For example if the pilot choose 2.5 piros/loop the model would be in sideways flight at the apex.

The use of the word "roll" could be taken as a requirement that the inversion of the model be started with a roll input. In the past I've distinguished piro flips from piro rolls as maneuvers where the first cyclic excursion was elevator or aileron respectively. If we stipulate to this convention it would seem to require that the number of piros per loop must be whole in order to put the heli in forwards or backwards flight as the model reaches the apex.

The description is lacking definition in my opinion. It would be nice if the F3C leadership would be more specific when describing these kinds of complex compound maneuvers.

It strikes me that if the goal of F3C is precision the ability to fly and judge maneuvers requires a certain limitation on their complexity. When a maneuver contains too many elements it tends to become just a hot mess of rotations that is nearly impossible to fly or judge accurately. Frankly I think the maneuver would benefit from a clarification that the model shall stop pirouetting and perform a half roll at the apex on the arc of the loop. This accomplishes the intended goal of requiring both inside and outside piro loops in a clean fashion.

I've marked up in red some of my issues with this maneuver description.

MA enters in upright flight and then performs four pirouetting loops. During each loop, the flight path is changed continually in a way that the low point is passed rotated about Why the use of the word "about"? the flight path should change by EXACTLY 45 degrees over the course of each loop. 45° (seen from above) until a complete globe has been described.
After each loop the pirouetting direction is changed at the bottom of the loop. MA performs on every top of the loop a half roll in either direction while still performing pirouettes. As already asked why the choice of the word "roll" instead of piro flip? The MA exits the manoeuvre at the same altitude but in opposite direction to the beginning. During each loop, the MA must perform at least two pirouettes. As I said this is a defined set maneuver flown as precision aerobatics. Why not stipulate the exact number of piros per loop?

If I were to re-write the description it might go as follows:

MA enters in upright forward flight and then performs four pirouetting loops. The piro rate shall be such that 3 complete pirouettes (1080 degrees of rotation) are completed during each loop. During each loop, the flight path is changed continually in a way that the low point is passed rotated exactly 45° (seen from above) until a complete globe has been described.

After each loop the pirouetting direction is changed at the low point of the loop.

Approaching the apex of each loop the MA shall perform a piro flip with the goal of transitioning between inside (disc in) and outside (disc out) loops. The piroflip shall follow the pre-established arc radius. The piroflip shall start 30 degrees from the loop apex after the completion of one and one half pirouettes (450 degrees). Holding the piro rate constant and matching the cyclic rotation to it, the MA will execute 180 degrees of cyclic rotation and 180 degrees of piro rotation completing the piroflip 30 degrees past the loop apex.

At the completion of the piroflip the MA will complete the remainder of the loop while continuing the last one and one half piro rotations. The MA exits the maneuver in upright forward flight opposite the direction that it entered.

Forgive the long reply. These things interest me especially as they provide a mechanism to advance the state of the art of heli flying. At any rate I'm looking forward to seeing how the top pilots interpret this Gordian knot of a maneuver. Video please

[Steve Graham]

If you want to take esoterica to the sublime we could argue the use of manoeuvre VS maneuver.

I really should be cleaning up after this weekend's fun fly.

[richardv]

Here's one by a UK pilot.

B.3 Piro Globe Double Reversed (0 min 34 sec)

[GJacksonF3N]

Some of the descriptions are very vague, maybe to the point of inaccurate. There was a recent update to the F3N bulletin issued by FAI that tries describe Duus Igloo in a better way. There were some issues this past year at NATS with the description of Galaxy.
I still believe that all of the different competitions should have a video to accompany the maneuver so conpetitiors know exactly what the judges are looking for.

[richardv]

I've decided to stick with what I've been practicing for now.
3 and a half piros on the way up,
from tail-first start the roll to the side and begin a single piro flip.
I should cross the centre-line going nose-first in knife-edge.
Flip finishes backwards inverted,
3 and a half piros on the way down.

This means each loop starts nose-first and the makes it easy to remember when to start the roll.

I made a video last week, but I don't have Movie Maker any more, so I need to find a free editor just to clip the ends.

[richardv]

Piro Globe Double Reversed (0 min 35 sec)

[richardv]

Another one here at about 1:40.
He does 4 piros per loop and seems to start the roll after 1 and a quarter piros on the way up. It's hard to figure where it starts and ends though.

FAI F3N SET MANUVUER FINAL (7 min 17 sec)

[p1andy]

Richard that's Just a standard reversal he's appears to be doing, he enters and exits each loop upright. My bad only watched the first move

Looks like he completes two piro on the way up then at the top almost a stationary flip before continuing the piro back down

[richardv]

Originally Posted by p1andy

Looks like he completes two piro on the way up then at the top almost a stationary flip before continuing the piro back down

I've played it at its slowest and now I think he's doing 1 and 3/4 on the way up with a piro flip roll in the direction of travel.

He's the 2nd person I've seen do that so I think the wording around roll means it can be started with aileron and not necessarily at 90º to travel.

Starting the roll in the direction of travel means you can use it to pull the heli over the top instead of relying on inertia. It might be worth trying.
Cheers

Update: Nope, after the roll it goes into 1/4 to forward flight so if you do the remaining 3 and 1/2 on the way down, you're starting the next loop backwards.