[NSRCA-discussion] F17 barrel roll

Wed Aug 26 02:15:48 AKDT 2015

Clarification for F-17.07 "Barrel Roll" by Michael Ramel: 

"At first, please recall the manoeuvre description as in the Sporting Code: 

F-17.07 Barrel-Roll 

>From upright, pull through a 1/8 loop into a 45° upline, perform a barrel-roll with 45° spiral pitch, perform a 45° upline, push through a 1/8 loop, exit upright. 

You first pull into a 45° upline, then at mid level you start to perform a full roll with the flight path going around a horizontal cylinder in a spiral (as the thread of a screw in a 45° pitch). 

Assumed you fly from right to left performing the barrel roll into right direction: 

>From low level, the aircraft pulls upright in a 45° upline first, then will be in a knife-edge (right wing down) position after the first 1/4 of the roll heading away from you in a 45° angle seen from above, then it is inverted on a 45° downline after the second 1/4 of the roll, then in a knife-edge position (right wing up) after the third 1/4 of the roll heading towards you in a 45° angle seen from above, finally it is upright again in a 45° upline after the fourth 1/4 of the roll as to finish the manoeuvre on high level. 

You have seen this barrel roll many times in show flight performances when ie. one aircraft is flying on a level line, while another aircraft spirals around it in one or more barrel rolls. However, for F3A this manoeuvre is precisely described and brakes down to the various geometric reference points."

 <https://www.facebook.com/n/?photo.php&fbid=1002089093145841&set=gm.760492524072687&type=1&relevant_count=1&aref=1440577829877657&medium=email&mid=760492524072687&n_m=donramsey%40gmail.com> https://scontent.xx.fbcdn.net/hphotos-xpt1/v/t1.0-9/s130x130/11921665_1002089093145841_596662265647801978_n.jpg?oh=b29eab8bc2566c2a69a48c5ad60679b4&oe=5668B71A

From: NSRCA-discussion [mailto:nsrca-discussion-bounces at lists.nsrca.org] On Behalf Of Derek Koopowitz via NSRCA-discussion
Sent: Sunday, August 23, 2015 11:26 AM
To: Ed Alt; NSRCA List
Subject: Re: [NSRCA-discussion] F17 barrel roll

Perhaps a barrel roll isn’t the best name for this maneuver – I would call it a slow wave roll instead.  There are very clear areas of judging criteria to look for in this maneuver…. First the pull to a 45 up line, the knife edge view of the plane at the top radius of the 45 up line, the inverted downline, the knife edge on the bottom radius and the completion (upright) view of the plane on the 45 up line before a push to level flight.  Since this roll would have to be flown slowly, the difficulty is pretty high.  Obviously ensuring that all the radii are the same as well.

From: NSRCA-discussion on behalf of NSRCA List
Reply-To: Ed Alt, NSRCA List
Date: Sunday, August 23, 2015 at 5:35 AM
To: NSRCA List
Subject: Re: [NSRCA-discussion] F17 barrel roll

I'm not sure , but after 100 years or so, it seems that the barrel roll may have a new definition.  This appears to require that the model skid around the entire rotation, which is not really how a barrel roll is typically done as far as I know.  I believe that you would normally do one mainly with simultaneous pitch and roll inputs, and maybe touches of rudder to keep that coordinated, in much the same  way as  a coordinated turn would be done in a full scale aircraft to keep the turn & bank indicator's ball centered. As a result, it would present itself as if the aircraft were traveling along the inside of a cylinder with both of it's main gear wheels always in contact with its inner surface, hence the name barrel roll.  Executed this way, you could do that Bob Hoover demonstration of keeping a glass of some liquid perfectly still, resting on top of the instrument panel.

This definition seems to be more of a variation on an integrated roll, and as a result you would expect to see the tail pointed at perhaps a 45 deg yaw angle at one point (when roll angle = 90 deg), and the nose yawed at you 45 deg at another (when roll angle = 180 deg).  And I think that as a result it would also mean that the wing tip in the direction of the roll would always be in contact with the inner surface of the imaginary cylinder, instead of both wheels.  Am I visualizing that correctly?  It seems like it would be tricky to judge accurately.

Ed

  _____  

Date: Sat, 22 Aug 2015 23:10:49 -0700
To: underdw at gmail.com; nsrca-discussion at lists.nsrca.org
Subject: Re: [NSRCA-discussion] F17 barrel roll
From: nsrca-discussion at lists.nsrca.org

Hopefully this helps…

From: NSRCA-discussion on behalf of NSRCA List
Reply-To: Daniel Underkofler, NSRCA List
Date: Saturday, August 22, 2015 at 6:21 PM
To: NSRCA List
Subject: [NSRCA-discussion] F17 barrel roll

In F17 there is a cryptic aresti symbol that is described in the figure description as a barrel roll.  Will somebody please describe this in more detail and what control inputs will obtain the required result?

Thanks, Dan

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