Aerobatics question

[Typhoon1244]

I was doing some FlightSafety Academy-style aeronautical musing today, and I got to thinking about a certain kind of maneuver. (Bear in mind I've had very little formal aerobatic training...much to my chagrin.)

Suppose you rolled your aircraft 360 degrees at a moderate pace, but while doing it you maintained a constant one G. That would mean the aircraft would have to turn and descend while you were rolling...a kind of sloppy spiral.

So you maintain 1G all the way through...and at the end of the maneuver, would you be back on your initial heading? Or would you be pointed somewhere else entirely?

Does such a maneuver turn into just a conventional Barrel roll?

 

[ShawnC]

As far as I have been told a 1G roll is a barrel roll.

 

[Rush Limbaugh]

"Suppose you rolled your aircraft 360 degrees at a moderate pace, but while doing it you maintained a constant one G. That would mean the aircraft would have to turn and descend while you were rolling...a kind of sloppy spiral."

During the roll, the nose will fall and the heading will start to change but you should end with the same parameters you started with. To start with, pull the nose up 5 to 10 degrees and start the roll. The airspeed will decrease during this time and you wil obviously be climbing. As you roll, your nose will drop and be at about 5 to 10 degrees nose low depending on how fast you rolled. Your airspeed will increase again and when you recover the nose to the horizon, you should be at about the same airspeed you started with and around the same alitude, as well as the same heading.

"So you maintain 1G all the way through...and at the end of the maneuver, would you be back on your initial heading? Or would you be pointed somewhere else entirely?"

You should have the same heading. If you roll slowly at 1 G, your heading will change slightly until you reach inverted. Once you pass inverted, the heading change will reverse and assuming you continue the roll at the same rate, you will be back to the same heading when you have rolled the entire 360 degrees.

"Does such a maneuver turn into just a conventional Barrel roll?"

A barrel roll is a roll about a point. Instead of just rolling the airplane, you pick a point out in front of you like a cloud, point on the horizon or even another airplane. Your goal is to keep your reference point on the same spot on the windscreen throughout the roll. If the point is directly in front of you, turn 30 to 45 degrees to the right or left and then pull up and roll into the point. It is a much slower maneuver than an aileron roll and takes much more finesse. Again, you should end with the same amount of energy you started with and near the same heading.

 

[DoinTime]

I was doing some FlightSafety Academy-style aeronautical musing today, and I got to thinking about a certain kind of maneuver. (Bear in mind I've had very little formal aerobatic training...much to my chagrin.)

Suppose you rolled your aircraft 360 degrees at a moderate pace, but while doing it you maintained a constant one G. That would mean the aircraft would have to turn and descend while you were rolling...a kind of sloppy spiral.

So you maintain 1G all the way through...and at the end of the maneuver, would you be back on your initial heading? Or would you be pointed somewhere else entirely?

Does such a maneuver turn into just a conventional Barrel roll?

Attempting a maneuver as you describe would most likely result in 70-90 degree nose down dive. If only rolling at a moderate pace at one 'g' you would slowly lose pitch control as you initiated the roll resulting in zero pitch control while passing through 90 degrees of bank. By the time you regained pitch control as you rolled inverted you would be pointing straight down.

Depending on the aircraft you are in an aileron roll can be completed at near one 'g' but a barrel roll will always require less than one 'g' on the top while inverted and more than one 'g' on the bottom while regaining your original pitch attitude. The completion of either of these maneuvers should end on the heading you initiated the maneuver at.

 

[Loafman]

Ok, we're digressing here. There are 3 basic types of rolls, and previous posts have them confused.

Slow rolls, aileron rolls, and barrel rolls.

Slow rolls have to be flown normally on a straight line. The roll rate has to be constant and the longitudinal axis of the plane has to go straight. This requires constantly changing rudder and elevator control inputs throughout the roll. Hesitation or point rolls include stops at certain roll angles. The number on the base of the roll symbol describes the number of points the roll would have if it were a 360 degree roll. Allowed are 2 point, 4 point and 8 point rolls. The fraction on the arrow of the roll symbol describes what fraction of a full roll is to be executed. If no points are specified, rolling is done without hesitations.

Aileron rolls are flown with the rudder and elevator in the neutral position during the roll. The aileron is fully deflected in the direction of the roll. This is the easiest of the rolls to fly.
The aileron roll is started by pulling the nose up to 20 - 30 degrees above the horizon. The elevator is then neutralized and the aileron fully deflected in the direction of the roll. The controls are maintained in that position till the roll is completed. After the roll is completed the nose is usually 20 - 30 degrees below the horizon. Dointime is right. The most common mistake performing the aileron roll is not to pitch up sufficiently to allow for the nose drop. A botched aileron roll usually turns into a split-S. The entire maneuver is close to 1G. Bob Hoover rolls his Shrike while pouring a glass of iced tea from a pitcher to demonstrate the 1G.
The aileron roll is not a competition maneuver.

The barrel roll is a combination between a loop and a roll. You complete one loop while completing one roll at the same time. The flight path during a barrel roll has the shape of a horizontal cork screw. Imagine a big barrel, with the airplanes wheels rolling along the inside of the barrel in a cork screw path. During a barrel roll, the pilot experiences always positive G's. The maximum is about 2.5 to 3 G, the minimum about 0.5 G. The Barrel Roll is a not competition maneuver.

Hope this helps.


Loafman

AKA

Akroman

 

[rfeathe1]

Just want to add my .02 to the aileron roll explanation--starting the roll with the nose up 20 degrees or so & then releasing the back pressure from the pullup will maintain 1 +G throughout the roll. Airplanes with a very fast roll rate can do the manuever from almost straight & level & the nose won't noticeably drop while rolling through the inverted position. The slower the roll rate the more time the lifting action of the wings has to pull the nose down while rolling through inverted. Aircraft with slower roll rates should pull the nose up at least 20 degrees & sometimes even more depending on how slow the RR is. The most common mistake i've seen is neutralizing the ailerons when inverted--this will pull the nose down & usually results in a split S & exceeding VNE. A slow roll is a horse of a different color--it is an excerise in coordination, constantly manipulating the rudder & elevator to keep the aircraft rolling on it's longitudinal axis. It usually touches 1 G negative when inverted. When discussing aerobatics among pilots it's easy to get involved in semantics--barrell rolls mean one thing to a military pilot & something entirely different to a civilian pilot--I guess I've rambled on enough.

 

[EagleRJ]

....another thing that differentiates barrel rolls (at least the way I was taught them) is that they always include 180 degrees of heading change, while an aileron roll has no heading change.

In a barrel roll started on a heading of North, your nose passes through the horizon inverted on a heading of either East or West, and you finish the maneuver back on North. A smooth barrel roll maintains a steady 1G all the way around, while an aileron roll may briefly drop below 1G depending on your roll rate. Only a slow roll should ever generate negative G.

I think I'll clip my Aresti cards to the yoke on my next flight and see if the First Officer says anything!

 

[Iced_up]

Barrel Roll

In a barrel roll started on a heading of North, your nose passes through the horizon inverted on a heading of either East or West, and you finish the maneuver back on North. A smooth barrel roll maintains a steady 1G all the way around, while an aileron roll may briefly drop below 1G depending on your roll rate. Only a slow roll should ever generate negative G.

I'm not sure what maneuver you are explaining but it sounds more like a split S. As described earlier, a barrel roll is a +1G maneuver throughout and if executed properly you will end up at the same altitude and heading as when you started. If your heading changes 180 degrees then you "fell" out of it. Any aircraft is capable of doing a barrel roll.

 

[Iced_up]

Some more info

The term "barrel roll" came from the way it is executed. It's taught as if the undercarriage is stuck to the inside of a barrel during the roll.

 

[Iced_up]

you would slowly lose pitch control as you initiated the roll resulting in zero pitch control while passing through 90 degrees of bank. By the time you regained pitch control as you rolled inverted you would be pointing straight down.

If you step on the top rudder while knife edge then you would have control of the nose attitude. How much? Depends on the airplane. Each airplane is different. But to say you would have zero pitch authority is not correct. Next time your in a steep turn try pressing on the "top" rudder and watch what your altimeter does.

 

[Hugh Jorgan]

Re: Barrel Roll

I'm not sure what maneuver you are explaining but it sounds more like a split S. As described earlier, a barrel roll is a +1G maneuver throughout and if executed properly you will end up at the same altitude and heading as when you started. If your heading changes 180 degrees then you "fell" out of it. Any aircraft is capable of doing a barrel roll.

I think if you re-read EAGLERJ's post, you'll see he described the barrel roll heading checkpoints perfectly. A split-s would have you end up on a reciprocal heading, something many-a-student have tried on me...not what you want to see when you enter the manuever with plenty of airspeed!

 

[Loafman]

Re: Re: Barrel Roll

I think if you re-read EAGLERJ's post, you'll see he described the barrel roll heading checkpoints perfectly. A split-s would have you end up on a reciprocal heading, something many-a-student have tried on me...not what you want to see when you enter the manuever with plenty of airspeed!

I agree with the heading checkpoints, but I'll buy ANYONE a case of beer that can execute a proper loop, barrel roll, or recover from any vertical downline at 1G constant. More like 2.5-3.5 in most acro platforms.

 

[DoinTime]

If you step on the top rudder while knife edge then you would have control of the nose attitude. How much? Depends on the airplane. Each airplane is different. But to say you would have zero pitch authority is not correct. Next time your in a steep turn try pressing on the "top" rudder and watch what your altimeter does.

This would be true, however, if your goal is to continue the roll putting in 'top' rudder will only get you into a cross controlled situation and stall your roll progress. 'Top' rudder will not give you altitude control in a 90 degree bank either it will only speed your progress towards the ground.

 

[Hugh Jorgan]

Re: Re: Re: Barrel Roll

I'll buy ANYONE a case of beer that can execute a proper loop, barrel roll, or recover from any vertical downline at 1G constant. More like 2.5-3.5 in most acro platforms.

Yer on!

 

[Typhoon1244]

Wait, wait, wait! You guys are straying away from my question.

Let me put it another way: let's assume you put in a certain amount of aileron and then leave it there so that the airplane is rolling at a constant, moderate rate. You don't pull the nose up first, you just roll into it like a sloppy student who's not maintaining altitude in a turn. (For grins, let's say you're rolling at ten degrees per second, so that you'll complete 360-degrees of roll in thirty-six seconds.) While holding that roll rate, you keep the ball in the center and do whatever you have to with the elevators to maintain one G.

What will the resulting maneuver look like? What will your pitch attitude be when you finish? How much will your heading change.

(I got to thinking about this after hearing about an AF student who attempted an aileron roll in a Slingsby T-3 and ended up in an unusual attitude recovery exercise...)

 

[rfeathe1]

If you are going to roll from straight & level, maintain 1 positive G & take 36 seconds to complete the roll, by the time you are rolling through the inverted position your nose will be WAY DOWN--probably 45 degrees or more. Airspeed will probably be about an inch past redline. I would not recommend attempting a roll like that, but if you do you better have a real tough airplane strapped to your ass.

 

[Typhoon1244]

I would not recommend attempting a roll like that, but if you do you better have a real tough airplane strapped to your ass.

Well, this is hypothetical, of course. Sort of an aerodynamic brain-teaser. (I'm not planning on trying this in an RJ anytime soon!)

 

[rfeathe1]

Doin Time--top rudder will not maintain altitude in a 90 degree bank??? Have you ever seen anyone fly knife edge & maintain altitude & a steady heading? How do you think they maintain altitude? With smoke & mirrors? They do it with top rudder which creates a positive AOA on the bottom side of the fuselage. They are flying the airplane off the side of the fuselage with top rudder & just enough elevator to keep it from turning.

 

[EagleRJ]

Ok Typhoon, aerodynamically speaking, if you were to try that, I'd bet that the plane's flight path would be a spiral that would stabilize at almost 90 degrees pitch down. I doubt that maintaining 1G, the plane would ever recover before hitting the ground, since as airspeed increases, each positive G produces less pitch rate. A constant roll would prevent recovery.

Assuming airspeed stabilizes at Vd + 30, or whatever, and infinite altitude, you might eventually reach level flight, hypothetically speaking, of course!

Anyone with a flight sim program want to give it a try?

 

[Typhoon1244]

Ok Typhoon, aerodynamically speaking, if you were to try that, I'd bet that the plane's flight path would be a spiral that would stabilize at almost 90 degrees pitch down. I doubt that...the plane would ever recover before hitting the ground, since as airspeed increases, each positive G produces less pitch rate. (emphasis added)

Okay. Suppose you did it in a Douglas SBD or maybe an AD Skyraider, an airplane whose dive brakes are so big you can push the nose over with them extended and not increase your airspeed by more than about 15%.

Remember, we're talking theory.