Barrel Rolling

[PJ_Godzilla]

I added the barrel roll to my repertoire a while back. I use a little rudder and opposite roll and my D-9 makes a nice helix.

Here's the issue: If I do that from zero pitch, the inverted portion of my horizontal helix "sags" - i.e., I lose alt inverted.

It seems to me that, to do a rolling scissor properly, you need to cycle the elevator sinusoidally as you maintain your aileron and rudder setting - by no means an easy feat. I almost think it'd be easier if I could decouple the two degrees of freedom (pitch and roll) on my Saitek...

Perhaps this part of the reason it's hard to be a good pilot. Has anyone got any useful advice on maintaining a tight rolling scissor with zero alt loss?

[bcadoo]

You have to relax it over the top because you have the constant 1G pulling you down.  In all maneuvers that you wish to maintain altitude you will have to bias it this way.

[PJ_Godzilla]

You have to relax it over the top

First, I find this statement highly ambiguous. Second, it seems to me, if anything, over the top I should be at something like full down elevator to maintain alt. "relax" implies, to me, less control input.

Third, this looks like a restatement of the issue identified in my question, rather than practical advice on elevator cycling in the maneuver.

No offense... but I didn't find this very helpful. I don't think you're obliged, I was just hoping for more.

[moot]

It seems to me that, to do a rolling scissor properly, you need to cycle the elevator sinusoidally as you maintain your aileron and rudder setting

Keep in mind that this might be (I'm not sure if I'm correctly picturing what you describe) the combat trim changing how much you actually have to move your js at low speed.

Perhaps this part of the reason it's hard to be a good pilot. Has anyone got any useful advice on maintaining a tight rolling scissor with zero alt loss?

It's specific to each plane.  In general you want to try and vertically stretch the barrels as much as you can, in the D9.  Because at low speed (keeping with your "tight" criteria) you won't be able to pull much angle as you come out of the vertical extremety of the barrel.  The D9 just isn't light enough on its wings to pull until relatively (compared to most other planes you'll be fighting in this rolling scissor) much later.

[PJ_Godzilla]

Keep in mind that this might be (I'm not sure if I'm correctly picturing what you describe) the combat trim changing how much you actually have to move your js at low speed.
 
It's specific to each plane.  In general you want to try and vertically stretch the barrels as much as you can, in the D9.  Because at low speed (keeping with your "tight" criteria) you won't be able to pull much angle as you come out of the vertical extremity of the barrel.  The D9 just isn't light enough on its wings to pull until relatively (compared to most other planes you'll be fighting in this rolling scissor) much later.

What I meant was, as you roll, your a/c's orientation w/r grav changes but, if you don't change your elevator setting, your lift vector does not... hence, the axis of your helix will bend toward the ground and you will lose alt going forward. I don't see that as a combat trim issue. To counteract this effect, you'd clearly have to apply additional elevator nose up as your roll angle increased, until your roll angle hit 90 degrees, at which point you'd need to start applying negative elevator to keep your nose up w/r the ground plane. At a roll angle of 180, you'd be at max negative elevator. Over time, this trace of elevator is only sinusoidal on the inverted side and discontinuous at +/- 90 degrees of roll since you go from max positive to zero at +/- 90. This isn't an issue in a single or even double barrel roll  but it is over a long scissoring maneuver.

Otherwise, I see what you mean about "tight"... The D9 would doubtless like a looser/larger radius scissor at higher speed since no f-dub, least of all the d-9, knows nothin' 'bout no low-speed flyin', Miss Scarlett, and that tight rolling would doubtless bleed the E posthaste.

Funny thing about the scissors is that, supposedly, over a long one, often opponents will fix on each other as they engage in opposite barrels. That's great, except for the fact that, doing so, that e-bleed makes either of 'em vulnerable to an outsider not so fixated or the auger - see "axis of helix bending" issue above.

Am I just crazy to think about this? Do most people do their barrels and just accept altitude loss?

[ImADot]

I'm no flight expert, but you seem to be talking about two different things here.  The post title, and your first paragraph lead us to believe you are talking about a barrel roll.  Then the rest of your post and all the replies since, seem to be talking about a rolling scissor.

A basic barrel roll involves you doing a 360 aileron roll with up elevator (pull your stick diagonally down-left or down-right).  You will climb through the first half, and when inverted you will descend - when you are wings level again, you should be a pretty near the same altitude you started at.

[PJ_Godzilla]

Imadot, correct me if I'm wrong but, if I hold the setting to which you refer beyond that first barrel roll, I will continuo barrel roll, yes? In so doing, am I not performing what is, really, half of a rolling scissor - sans the opponent?

If so, the same issue applies... You've only got some lift-weight up but the same lift+weight on the downside - meaning, unless you modify that elevator setting, your barrel roll is a net alt loss - and that's only going to be exarcerbated by repetition.

[ImADot]

Here, I found this...now you know why I'm no flight expert. 

Ok, let’s clear up the barrel roll question first.

The Barrel Roll is one of a family of closely related maneuvers that can be carried out offensively or defensively. Naming conventions vary among simulation pilots, and it is common to see them refer to a barrel roll when they are actually executing a lag roll, a quarter plane, or a vector roll. I’ll describe the Barrel and Vector Roll attacks together since they are pretty similar in execution (g being the major variable). Offensively, these maneuvers are not seen much in the Aces High arena... When used offensively they are well up the "food chain" in sophistication and complexity, so the barrel roll is employed far more often as a means of turning a defensive situation into a brief offensive one, after a poorly executed attack. That’s the rub, it only works with some unwitting co-operation from the attacker, but it can be very impressive when it works, because it can often get a kill against an attacker that has a big advantage.

Before talking about the barrel roll though, it is important to remain clear about the motive for carrying out any maneuver during air combat, and in air combat there is only one reason to maneuver… Any ideas?

You maneuver in air combat so as to improve your chances of a successful shot. 

The Barrel/Vector roll is designed to solve an aspect problem when you can match the turn rate and speed of your opponent but you find yourself too much inside his turn. Basically your range and aspect present you with a very low probability shot. In this situation, you have aligned your fuselage with his but you have too much lateral separation, i.e. you have too much sideways displacement. Your objective is to reduce the lateral separation without losing your angle off advantage... meaning you want to get behind him and still keep your fuselage aligned with his.

Make sure you understand the underlying need, what BFM problem are you trying to solve? Assume your opponent is turning in a similar aircraft and you are holding the turn with him. Your angle off is low, your fuselages nearly aligned, that’s good. Your aspect, however, is too far inside his turn... meaning that you are too far away from him with too much lateral displacement for a shot and appear to be stuck there. What you want to do is to somehow move your aircraft across the space between you and your opponent without changing your low angle off and without losing angles or energy. So, the basic idea of these two maneuvers when used offensively is to reduce your aspect angle, without losing your angle off advantage, while holding onto any small closure or turn rate advantage you may have.

Most arena pilots will try to solve that problem by opening their turn, and trying to take the low probability shot, at a close enough range that can work well, but when the combination of range and aspect are just beyond your gunnery skills, attempting to open the turn for a shot will cost angles, increase the range and the aspect, and because they will need to tighten the turn again afterwards to recover, by pulling higher G at higher speed, they will also waste energy. The end result will be wasted ammunition and energy and a bigger BFM problem than the one they started with.

However, that is the most common response in the arena, and sometimes it will work, particularly if in a dissimilar aircraft engagement, one aircraft outclasses the other, in weapons or performance such that the attacking pilot is willing to sacrifice good BFM for a shot, and if you are an excellent shot, you can afford to be lazy. Don’t forget, the whole point of our maneuvers is to reduce the angle off, aspect, and range inside the limits of our gunnery skills.

So, back to the Barrel Roll… Your aspect angle is too high and... you don’t want to overshoot his 3/9 line for all the obvious reasons. If you simply try to pull harder on the bandit and then reverse back to his heading, you will bleed too much energy. Instead, you execute a rolling maneuver designed to reduce your aspect without losing too much energy in the process. You start by aligning fuselages then begin an easy pull to approximately 20 degrees above the plane of motion of your opponent, you should see him low on your canopy rail area, continue the roll over your opponent’s flight path into a lag pursuit position. Aim just behind him. As a technique, do not roll past 90 degrees relative to his plane of motion. Do not use extra back pressure in the roll. Extra back pressure will pull your nose towards his six and will increase your angle off. You do not want that to happen. Hold the roll as your opponent drifts below your canopy rail and continue as your flight path drifts from its starting point inside the turn to a point at your opponent’s high six o’clock. His turn rate will cause you to “float” to his high six. Think of yourself as being “inverted” relative to his bank angle. Now roll quickly 180 degrees so that you are now looking down onto your opponent... your bank angle now approximates his. Your angle off is close to his and your aspect angle is minimal. Overbank slightly to bring your nose down... the enemy aircraft should be coming into your forward view/gun sight so that you can complete your attack.

Vector Roll.  For this maneuver, you are rapidly approaching your opponent from the inside of his turn. You have little angle off or aspect, but your closure is excessive. So much so that you cannot kill it with idle power or other braking techniques (dropping flaps or landing gear). You are in danger of overshooting his 3/9 line. You are going to have to let geometry save the day. The concept behind this maneuver is to rotate your lift vector aggressively around the flight path of your opponent. This will require a relatively high g load with a resultant high angle of attack (AOA) and corresponding high drag penalty. This rotating of your lift vector and associated drag will kill off your excessive closure. Start by blending in back pressure and aileron to raise your nose and, at the same time, begin pulling it towards your opponent’s six o’clock. 20-30 degrees pitch should be plenty. Pull your throttle back if closure is very high, otherwise leave your throttle where it is. You will see your opponent descend towards your canopy rail. You will be rolling around his high six. Keep the back pressure in as you continue to roll all the way around back to where your bank angle approximates his. You should have your opponent in your front quarter. If he is not in your forward view, roll towards him and pull until he appears in the gun sight. Do not confuse this maneuver with a Lag Roll. A lag roll is similar but flown with much less g. In a lag roll, you roll with moderate g (2-3) around your opponent’s flight path. The objective in a lag roll is to “back out” from a too close six o’clock position, while a vector roll’s objective is to reduce closure without necessarily reducing your range.

The rolling scissors shown below often results from a close-in vertical overshoot, or may be a natural progression of the flat or low speed scissors. As the name implies, this type of scissors involves a series of barrel rolls with the axis of the roll in the direction of motion. The rolling scissors is a more efficient defensive manoeuvre than the horizontal scissors due to the utilisation of the three-dimensional maneuver (barrel roll). The rolling scissors may be used in nearly all situations where a horizontal scissors could be used, except when the defender does not have enough speed to roll over the top. It is most effective when the attacker overshoots the defender with a high angle off below his flight path.



You continue to barrel roll, placing your lift vector on or slightly aft of the bandit. Your goal is to execute the rolling scissors as shown and explained in the diagram above and to capitalize on any mistake the bandit makes.  To stay offensive in a rolling scissors, you use the three-dimensional environment to control your energy effectively by:

• Proper lift vector placement
• Pulling to the edge of the stall
• Trading airspeed for altitude to reduce your forward velocity vector
• Use flaps to lead the top and retract them to lag the bottom, just as you would in a vertical fight

In all this, you are trying to stay behind the bandit.  A key factor in winning the rolling scissors is to understand that it is the steepness of your climbs and dives (the helix angle of your flight path) that determines your horizontal movement more than your absolute speed.

Hope that helps...

Badboy

[mechanic]

Hi,

I fully understand your question and hope this answer may be simple and usefull.

Yes: You need to reverse your elevator deflection as you roll to near inverted. Exactly as you have assumed, opposite elevator deflection is vital to keeping the top of your barrel from sagging. If you use a combination of Rudder and Aileron to force a gentle snap roll (hard rudder and lightly moving the elevators back to create the desired roll rate, without being quite so restricted by the a/c aileron roll rate) through 180 degrees...Then you will find you need to reverse that elevator to full down deflection as you reach inverted to save the plane from flopping or simply just losing altitude through the inverted phase.

It is almost possible to imagine the shape of your helix and then also imagine the shape of your joystick being opposite to it in regard to elevator deflection. It is almost as if you must 'stir the pot' with your elevators in an opposite motion to the barrel.

Some aircraft will require almost no opposite elevator deflection to maintain a decent helix, where as others, such as your Dora, will drop out of the sky without a significant down deflection on the elevators through the top of the roll.

(garbled response, hope it helps)

[PJ_Godzilla]

Now we're talking. So, mechanic, pray tell what a/c don't sag over the top? I haven't tried this maneuver in my k-4 yet - since everything roll seems a bit slow. Yet, I have a feeling, given the better pitch and rudder authority, that I could pull off a better helix in the k-whopper.

In general, the k-4 is growing on me. The d-9 is a little dangerous to the pilot since, inevitably, I'm tempted to bleed energy in it. Once you've done that, you're hosed. The K-4, on the other had, is much better at acquiring potential E via it's fabulous climb rate. That, and I love the tater gun. I hit a Mossie with a single tater - BOOM.
I hit an A-20 with a single tater - fireball/BOOM. You've got to love that. Too bad you can't dive the thing...

[PJ_Godzilla]

Thanks, I'madot... That's pretty useful and requires some practice/mental working out to fully understand. I'm not quite sure about the use of the flaps for lag and lead as cited by Badboy in the scissors bit. However, I will pocket this one and take it with me to the training arena.

[mechanic]

a spifire mk16 for example will quite happily roll inverted with a slow speed roll and not lose stability or much altitude before rolling back to level. In a climbing turn or roll with alot of possitive elevator deflection the spit16 will still remain stable and a health angle of attack where as something like a mosquito will often lose it's tail round over the top of itself if it does not reverse the elevators for the inverted part.



edit: Here i made a small demo of the spit16 vs the mosquito for high G low alt barrels.

in order in the film

 - 3 barrels down the runway in spitfire mk16 using strong possitive elevator the whole time. Absolutely no change and no need to push the stick forward to avoid the ground.

 - 3 very low alt high speed 180 degree snap rolls in spitfire mk16 using instant change from possitive elevator to negative elevator to remain in level flgiht.

 - Mosquito take off barrel roll using full negative elevator to hold the inverted phase. After level flight returns goes on up into a stall turn on a wing tip (again, using alot of negative elevator to not lose angle of attack - wish we could see stick input in films)

 - Mosquito rolls down the runway to replicate the spitfire mk16 roughly. Requires full negative elevator to keep the shape and angle of attack through inverted phase 

 - Finally one attempt at a similar tight barrel in the mosquito remaining at constant possitive elevator - disasterous spin.


here is the film:

http://www.freeroleentertainment.com/barrel_rolls.ahf

[mechanic]

bumped sorry, jsut incase you missed the late edit.