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#4080369 - 02/18/15 03:06 AM Barrel Roll  
Joined: Mar 2007
Posts: 483
Aullido Offline
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Aullido  Offline
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Joined: Mar 2007
Posts: 483
There is a plenty of videos about barrel roll, the problem is that no one shows how the controls are used. I know there are two kinds of barrel roll, around the wing tip and the other around the lift vector. On the first case I don't even know if rudders must be applied. I usually keep a constant pull all the time. Any advise?

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#4080616 - 02/18/15 06:38 PM Re: Barrel Roll [Re: Aullido]  
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rollnloop. Offline
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rollnloop.  Offline
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It depends on what you're trying to do. If it's an offensive barrel roll started early enough you may want to keep your energy, so it's soft pull/soft roll/keep engine power. Usually more pull than roll.

If it's a defensive overshoot move, you may need to pull harder, roll a bit more, and add some rudder into the roll acting as airbrake, while idling your engine. Then as soon as it's obvious your ennemy will overshoot, apply full power and bite his butt.

#4080881 - 02/19/15 01:07 PM Re: Barrel Roll [Re: Aullido]  
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Deacon211 Offline
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Deacon211  Offline
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A Barrel Roll in the classic sense is a rolling and pulling maneuver. As such, there is usually little need for or benefit to using rudder, unlike say, a wing over.

In general, in jets at least, you don't use a great deal of rudder unless you are fairly slow (like reversing in a flat scissors). Since you should never be extremely slow in a Barrel roll, you should generally not need to use the rudder. Of course you may want to use the rudder for other purposes, such as if you had to extend the top portion of the BR because of what the bandit is doing and then needed to align your nose for a quick shot or to get your nose back down.

But in these cases, you aren't really doing a BR anymore, but something else. This is perfectly fine as air combat isn't so much an "I'm going to do this, and then I'm going to do that" sort of endeavor. It's more of a "What am I going to do right now?" affair. So, if what you were doing isn't working, then it's time to do something else. smile

#4082352 - 02/22/15 11:04 PM Re: Barrel Roll [Re: Aullido]  
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Aullido Offline
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Aullido  Offline
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Posts: 483
Thank you both for your advise.

#4097322 - 03/26/15 02:09 PM Re: Barrel Roll [Re: Aullido]  
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Deacon211 Offline
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Deacon211  Offline
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Hey Aullido,

I ran across this while I was researching something else...naturally.

http://www.answers.com/topic/barrel-roll-2

It gives a pretty good coverage of barrel rolls and all their variations including some nice animations.

Two things that I think are worthy of pointing out,

1. Unlike what we said, some airplanes will require rudder to complete the roll. This is logical enough as many, particularly early prop, planes don't roll all that well by aileron alone. Once you move into jets however, rudder use becomes more the exception than the rule.

2. One thing the article suggests that I think is a bit misleading, is that you should commence rolling the aircraft shortly after your nose breaks the horizon.

One of the big lessons to be learned from the Barrel Roll is lift vector placement.

In other words, where goes the lift vector, so go you.

Your goal in the first portion of the BR is to get your nose 45 degrees up, against the force of gravity. You also need to get your nose 45 degrees off heading, but you will see that that isn't very difficult. If however, you begin rolling immediately in the BR, you will rapidly divert your lift vector from the vertical and you will find it increasingly difficult to get your nose up where you want it. Remember, after only 30 degrees of roll you have already lost about 13% of your lift; the rest being diverted into the horizontal. By 60 degrees, half.




So, in order to perform a good BR, I'd recommend rolling not at all until you get a good 30-35 degrees of nose up. Then you can play out the remainder of of your angle of bank to reach 45 degrees up when you reach 45 degrees off heading.

This is not a pointless lesson restricted to airshows pilots. If you want to get your nose up to do a turn reversal, do it wings level. If you are at the bottom of a rolling vertical scissors and you are trying to minimize the vertical portion of the overshoot, do it wings level. If your nose is buried after a bombing run and you are trying to get back up above the threat envelope....wait for it....yes, do it wings level.

In cases other than the pure vertical, the lesson still holds. If you want to get behind someone, don't put your lift vector (or velocity vector if you aren't turning) in front of them. This is why continuing a high aspect attack by continually leading a bandit yields a (generally ugly) overshoot.

Hope that helps.

Deacon



Moderated by  Andy Bush, RacerGT 

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