Barrel roll
Encyclopedia
A barrel roll is an aerial maneuver in which an airplane makes a complete rotation
on its longitudinal axis while following a helical
path, approximately maintaining its original direction. It is sometimes described as "a combination of a loop and a roll". The G-force
is kept positive (but not constant) on the object throughout the maneuver, commonly between 2-3 G, and no less than 0.5 G.
). Most often, a barrel roll refers to a helical roll around the relative forward motion of the aircraft, in which the nose ends up pointed along the flight path. It is performed by doing a combination of a roll and a loop.
Outside of aerobatic competition, the Boeing 367-80 and Concorde
prototype were barrel rolled during testing. The Boeing 367-80 was rolled twice by Tex Johnston
in an unauthorized maneuver while demonstrating the aircraft to the International Air Transport Association
over Lake Washington
, Seattle. The Concorde was rolled multiple times by her test pilots, including Jean Franchi and Brian Walpole
.
input, which is accomplished by easing the stick to either the right or the left. As the airplane rolls it will continue to pitch upward. The pilot will need to control the roll rate, keeping the nose 45 degrees off the reference point on the horizon as the plane rolls around this spot. Some planes may require rudder
input, while most high powered planes will only need to be guided by aileron and elevator
control.
When the aircraft has rolled 90 degrees, and the wings are vertical, the nose should be pitched about 45 degrees directly above the reference point on the horizon. As the plane continues to roll upside-down it will begin to level out, and the horizon will appear to rise to meet the nose. When in the completely inverted position, the aircraft should be level and the nose should still be 45 degrees to the side of the reference point, putting it 90 degrees off of the original flightpath. As the nose drops through the horizon, the pilot may need to reduce the elevator pressure, to counter-act the force of gravity and the loss of lift. Still keeping the nose 45 degrees off the reference point, the plane should roll into level flight along the same flightpath and at the same altitude at which the maneuver began.
ing, a barrel roll may refer to one of many maneuvers. These maneuvers are often simply called barrel rolls, but many fall into the category of "displacement rolls."
. This can also help an attacker to prevent an overshoot. This often forces both planes to continue through a series of rolls known as a rolling scissors maneuver. A barrel roll is also often used to check blind spots while remaining on a steady flight path.
of less than one, each consecutive roll will be lower than the previous, and the pilots can quickly find themselves at ground level. Any advantage is usually lost by the first pilot that attempts to disengage.
By moving the fighter more into the vertical plane, the pilot can use gravity to assist the aircraft in turn performance. In vertical or oblique geometric planes, the turn will be much slower over the top, but the turn radius will be much smaller. Conversely, the turn radius will be much larger through the bottom of the turn, but the turn rate will be faster. Displacement rolls make full use of this assistance provided by gravity. By moving the fighter into more of the vertical plane, the pilot can then control the roll rate and yaw to provide a sharp reduction in turn radius, helping the attacker to prevent an overshoot and remain inside of the defender's turn.
This type of roll is called a canopy roll, because it is often used as a way for aircraft to quickly change positions, by rolling over the top of an airplane and coming down on the other side. Canopy rolls are often used in combat, to displace the attacker in relation to the defender's flight path. An attacker following inside the defender's turn may need to displace the aircraft to the outside of the defender's turn in order to prevent an overshoot. Similarly, if following outside the turn of a defender that is much more maneuverable, the attacker may be unable to pull the nose up into a suitable firing position. By using a canopy roll, the attacker can shift the aircraft laterally away from the defender's flightpath. This will cause the flightpaths of both airplanes to cross, using geometry to change the attacker's aim. Canopy rolls are often used by the attacker when the defender reverses the turn, allowing the attacker to follow the reversal while keeping the correct relative position.
The maneuver is performed when an overshoot is imminent and cannot be corrected with a normal displacement roll. Much more aggressive than a normal displacement roll, the maneuver begins by rolling slightly toward the direction of the defender's break, and then pulling up sharply. At roughly 30 degrees from the horizon, the pilot begins the barrel roll away from the defender's break, applying more elevator pressure than roll. When inverted, the pilot then uses the assistance provided by gravity combined with rudder control to bring the fuselage
s of both aircraft into alignment. As the nose passes through the horizon, the pilot will then align the lift vector ahead of the defender, to bring the fighter back into the correct geometric plane, inside of the defender's turn.
The success of a barrel roll attack depends greatly on the aircraft's ability to zoom climb
. As the attacker is coming down, the defender may counter by pulling up unto a barrel roll, resulting in a rolling scissors.
Rotation
A rotation is a circular movement of an object around a center of rotation. A three-dimensional object rotates always around an imaginary line called a rotation axis. If the axis is within the body, and passes through its center of mass the body is said to rotate upon itself, or spin. A rotation...
on its longitudinal axis while following a helical
Helix
A helix is a type of smooth space curve, i.e. a curve in three-dimensional space. It has the property that the tangent line at any point makes a constant angle with a fixed line called the axis. Examples of helixes are coil springs and the handrails of spiral staircases. A "filled-in" helix – for...
path, approximately maintaining its original direction. It is sometimes described as "a combination of a loop and a roll". The G-force
G-force
The g-force associated with an object is its acceleration relative to free-fall. This acceleration experienced by an object is due to the vector sum of non-gravitational forces acting on an object free to move. The accelerations that are not produced by gravity are termed proper accelerations, and...
is kept positive (but not constant) on the object throughout the maneuver, commonly between 2-3 G, and no less than 0.5 G.
Etymology
The barrel roll is so named because an aircraft executing this maneuver looks as though it were flying with its wheels running along the inside edge of a barrel. A more common modern visualization is to imagine an airplane trying to fly in a horizontal corkscrew around the line of the direction of travel.Aviation
In aviation, the maneuver includes a constant variation of attitude in all three axes, and at the midpoint (top) of the roll, the aircraft is flying inverted, with the nose pointing at a moderate angle to the general path of flight. The term "barrel roll" is frequently used, incorrectly, to refer to any roll by an airplane (see aileron rollAileron roll
The Aileron Roll is an aerobatic maneuver in which the aircraft does a full 360° revolution about its longitudinal axis. When executed properly, there is no appreciable change in altitude and the aircraft exits the maneuver on the same heading as it entered...
). Most often, a barrel roll refers to a helical roll around the relative forward motion of the aircraft, in which the nose ends up pointed along the flight path. It is performed by doing a combination of a roll and a loop.
Outside of aerobatic competition, the Boeing 367-80 and Concorde
Concorde
Aérospatiale-BAC Concorde was a turbojet-powered supersonic passenger airliner, a supersonic transport . It was a product of an Anglo-French government treaty, combining the manufacturing efforts of Aérospatiale and the British Aircraft Corporation...
prototype were barrel rolled during testing. The Boeing 367-80 was rolled twice by Tex Johnston
Alvin M. Johnston
Alvin M. "Tex" Johnston was a American jet-age test pilot for Bell Aircraft and the Boeing Company.-Early years:...
in an unauthorized maneuver while demonstrating the aircraft to the International Air Transport Association
International Air Transport Association
The International Air Transport Association is an international industry trade group of airlines headquartered in Montreal, Quebec, Canada, where the International Civil Aviation Organization is also headquartered. The executive offices are at the Geneva Airport in SwitzerlandIATA's mission is to...
over Lake Washington
Lake Washington
Lake Washington is a large freshwater lake adjacent to the city of Seattle. It is the largest lake in King County and the second largest in the state of Washington, after Lake Chelan. It is bordered by the cities of Seattle on the west, Bellevue and Kirkland on the east, Renton on the south and...
, Seattle. The Concorde was rolled multiple times by her test pilots, including Jean Franchi and Brian Walpole
Brian Walpole
Captain Brian Walpole OBE, FRAeS is a pilot who was the General Manager with responsibility for Concorde with British Airways.Walpole started his career in aviation by joining the RAF in 1952...
.
Execution
To do a barrel roll from the pilot's perspective, it may best be thought of as a roll around a point on the horizon that is 45 degrees off the flightpath. Starting from a level flight, the pilot will usually pick such a point on the horizon as a reference. The pilot will then pull back on the stick, bringing the plane up into a brief climb. As the nose passes through the horizon, the pilot begins to apply aileronAileron
Ailerons are hinged flight control surfaces attached to the trailing edge of the wing of a fixed-wing aircraft. The ailerons are used to control the aircraft in roll, which results in a change in heading due to the tilting of the lift vector...
input, which is accomplished by easing the stick to either the right or the left. As the airplane rolls it will continue to pitch upward. The pilot will need to control the roll rate, keeping the nose 45 degrees off the reference point on the horizon as the plane rolls around this spot. Some planes may require rudder
Rudder
A rudder is a device used to steer a ship, boat, submarine, hovercraft, aircraft or other conveyance that moves through a medium . On an aircraft the rudder is used primarily to counter adverse yaw and p-factor and is not the primary control used to turn the airplane...
input, while most high powered planes will only need to be guided by aileron and elevator
Elevator (aircraft)
Elevators are flight control surfaces, usually at the rear of an aircraft, which control the aircraft's orientation by changing the pitch of the aircraft, and so also the angle of attack of the wing. In simplified terms, they make the aircraft nose-up or nose-down...
control.
When the aircraft has rolled 90 degrees, and the wings are vertical, the nose should be pitched about 45 degrees directly above the reference point on the horizon. As the plane continues to roll upside-down it will begin to level out, and the horizon will appear to rise to meet the nose. When in the completely inverted position, the aircraft should be level and the nose should still be 45 degrees to the side of the reference point, putting it 90 degrees off of the original flightpath. As the nose drops through the horizon, the pilot may need to reduce the elevator pressure, to counter-act the force of gravity and the loss of lift. Still keeping the nose 45 degrees off the reference point, the plane should roll into level flight along the same flightpath and at the same altitude at which the maneuver began.
Military attack
In air combat maneuvering, historically known as dogfightDogfight
A dogfight, or dog fight, is a form of aerial combat between fighter aircraft; in particular, combat of maneuver at short range, where each side is aware of the other's presence. Dogfighting first appeared during World War I, shortly after the invention of the airplane...
ing, a barrel roll may refer to one of many maneuvers. These maneuvers are often simply called barrel rolls, but many fall into the category of "displacement rolls."
Barrel roll
The term barrel roll, by itself, most often refers to a helical roll around a straight flight path, the purpose of which is to slow the relative forward motion of the aircraft. This can help a defender to force an attacker, who is usually behind the defender, to fly out in front, called overshootingOvershoot (aviation)
In aviation, an overshoot is an aborted landing. See: Go-around and Runway safety area.In air combat maneuvering, also called dogfighting, an overshoot can refer to three different situations. The first is referred to as a wingline overshoot...
. This can also help an attacker to prevent an overshoot. This often forces both planes to continue through a series of rolls known as a rolling scissors maneuver. A barrel roll is also often used to check blind spots while remaining on a steady flight path.
Rolling scissors
The rolling scissors, also called vertical scissors or simply "rollers," is usually an undesirable maneuver to be caught in, both for the attacker and the defender. The advantage usually goes to the aircraft with the higher turn rate, especially when pulling the nose through the top and bottom of the turns. Correct placement of the lift vector during the maneuver is crucial to keep from moving ahead, relative to the opponent. There are many optical illusions that affect the pilot's ability to determine the relative position of the opponent, and mistakes can easily be made. It is extremely difficult to get a suitable firing solution during the rolling scissors. If the aircraft have a thrust-to-weight ratioThrust-to-weight ratio
Thrust-to-weight ratio is a ratio of thrust to weight of a rocket, jet engine, propeller engine, or a vehicle propelled by such an engine. It is a dimensionless quantity and is an indicator of the performance of the engine or vehicle....
of less than one, each consecutive roll will be lower than the previous, and the pilots can quickly find themselves at ground level. Any advantage is usually lost by the first pilot that attempts to disengage.
High g barrel roll
A high g barrel roll is a last ditch defensive maneuver, performed when the attacker has achieved a suitable firing solution. The maneuver is performed when the attacker is very close, and a barrel roll performed by the defender may cause an overshoot. The maneuver begins by cutting the throttle, extending the speed brakes, or turning very hard to encourage an overshoot. The maneuver is then executed by applying hard rudder input during the barrel roll to assist with the roll. The sudden change in the relative forward speed may cause a surprised attacker to fly out in front of the defender. Depending on the situation, a high g barrel roll can be performed "over the top," by beginning the roll like a normal barrel roll. The roll can also be performed "underneath," by doing a half aileron roll into the inverted position and beginning the barrel roll while upside-down.Displacement roll
There are a variety of maneuvers that can be described as displacement rolls. A displacement roll is a barrel roll that moves the aircraft laterally, displacing it from its projected flightpath and moving it onto a new flightpath. Depending on how a displacement roll is executed, it may provide a shift laterally onto a parallel flightpath, or more aggressive rolls can be used to provide a reduction in turn radius.By moving the fighter more into the vertical plane, the pilot can use gravity to assist the aircraft in turn performance. In vertical or oblique geometric planes, the turn will be much slower over the top, but the turn radius will be much smaller. Conversely, the turn radius will be much larger through the bottom of the turn, but the turn rate will be faster. Displacement rolls make full use of this assistance provided by gravity. By moving the fighter into more of the vertical plane, the pilot can then control the roll rate and yaw to provide a sharp reduction in turn radius, helping the attacker to prevent an overshoot and remain inside of the defender's turn.
Canopy roll
A canopy roll is the simplest form of displacement roll. The roll is used to provide lateral displacement while maintaining the original heading. The maneuver begins like a normal barrel roll, but when the plane is nearly inverted, the pilot places the elevators and ailerons close to the neutral position. Called "unloading," this allows the inverted aircraft to fly momentarily in a fairly straight arc. When the pilot has achieved enough lateral displacement, the pilot continues through the second half of the barrel roll.This type of roll is called a canopy roll, because it is often used as a way for aircraft to quickly change positions, by rolling over the top of an airplane and coming down on the other side. Canopy rolls are often used in combat, to displace the attacker in relation to the defender's flight path. An attacker following inside the defender's turn may need to displace the aircraft to the outside of the defender's turn in order to prevent an overshoot. Similarly, if following outside the turn of a defender that is much more maneuverable, the attacker may be unable to pull the nose up into a suitable firing position. By using a canopy roll, the attacker can shift the aircraft laterally away from the defender's flightpath. This will cause the flightpaths of both airplanes to cross, using geometry to change the attacker's aim. Canopy rolls are often used by the attacker when the defender reverses the turn, allowing the attacker to follow the reversal while keeping the correct relative position.
Lag displacement roll
A lag displacement roll, or "lag roll," helps improve the firing position of the attacking aircraft, and helps to increase range. The attacker performs the roll during a hard, turning chase, rolling both up and away from the turn. Typically performed a little slower than a normal displacement roll, the attacker achieves the proper reduction in turn radius on, or just outside of the defender's turn. Upon completing the roll, when the aircraft's lift vector points directly at the enemy, the pilot pulls back on the stick, reentering the turn with the ability to achieve a better firing position.Barrel roll attack
A barrel roll attack is a military maneuver that improves the attacker's offensive position and prevents the attacker from overshooting. In this maneuver the defender breaks one direction and so the attacker performs a barrel roll in the opposite direction. The attacker pulls back on the stick more than a normal barrel roll, performing a tighter loop than the roll. It is the three dimensional equivalent of a 90 degree turn, and the attacker finishes the loop, having completed three quarters of a roll, with the nose pointed along the defender's flight path.The maneuver is performed when an overshoot is imminent and cannot be corrected with a normal displacement roll. Much more aggressive than a normal displacement roll, the maneuver begins by rolling slightly toward the direction of the defender's break, and then pulling up sharply. At roughly 30 degrees from the horizon, the pilot begins the barrel roll away from the defender's break, applying more elevator pressure than roll. When inverted, the pilot then uses the assistance provided by gravity combined with rudder control to bring the fuselage
Fuselage
The fuselage is an aircraft's main body section that holds crew and passengers or cargo. In single-engine aircraft it will usually contain an engine, although in some amphibious aircraft the single engine is mounted on a pylon attached to the fuselage which in turn is used as a floating hull...
s of both aircraft into alignment. As the nose passes through the horizon, the pilot will then align the lift vector ahead of the defender, to bring the fighter back into the correct geometric plane, inside of the defender's turn.
The success of a barrel roll attack depends greatly on the aircraft's ability to zoom climb
Zoom climb
A zoom climb is a climb where the rate of climb is greater than the maximum for a sustained climb, as determined from the thrust of the aircraft's engines. During a zoom climb, the aircraft accelerates to a high air speed at an altitude at which it can operate in sustained level flight. The pilot...
. As the attacker is coming down, the defender may counter by pulling up unto a barrel roll, resulting in a rolling scissors.