Glossary

What the words in this manual mean.

ACRO: The rate mode of the sim. The sticks set the rate of roll and pitch. When you centre the sticks, the plane holds its attitude. Use it for aerobatics.
AGENT mode: A flight mode of our ArduPlane fork, custom mode 50. In AGENT mode, the executor flies the agent plan from the ground. The safety envelope keeps the plane safe. A change of the mode switch on the radio takes the plane out of AGENT mode at once.
Agent plan: What the ground control agent tells a plane to do for the next few seconds. It has a primitive, a target or a point, a plan id and a time to live. The ground sends it as a MAVLink COMMAND_INT with the command 31010. Only a plane in AGENT mode takes it.
Agent status: What a plane in AGENT mode tells the ground once a second, as four NAMED_VALUE_INT messages. AG_PLAN is the id of its plan, AG_PRIM the primitive of that plan, AG_ENV the count of interventions and AG_FALL the fallback. The console of the runner shows them as plan, prim, env and fall.
ANGLE: The self-levelling mode of the sim. The sticks set the angle of bank and pitch. When you release the sticks, the plane becomes level. Use it when you learn to fly.
Annunciator: A lamp on the CAUTION / WARNING screen of the ground station. ARMED lights when the plane is armed. Other lamps show the link, GPS, the battery, a stall and the fence.
ArduPilot: The open-source autopilot. ArduPlane is its version for planes. Here, it runs as SITL and flies the plane of the sim. The Ground control station talks to it.
Arena: The part of the sky for a game of tag: a circle of 90 m round the centre of the field (the arena centre, for the runner), below 60 m. Small cones mark its edge. If you fly out of it, you are it.
Arena centre: The centre of the arena of a game of tag in the runner, and of the fence of AGENT mode: 70 m north of home. The arena is 90 m round it. The fence is 85 m round it, so the plane turns back before it leaves the arena.
AUTO: The mode of ArduPilot that flies the mission on the vehicle, one item after the other.
Band: A primitive, number 5: stay between two heights and circle over the arena. The altitude of the plan is the bottom of the band. The radius of the plan is its thickness.
Ceiling: The highest height above home that the safety envelope allows, set with AGENT_CEIL.
Chase: The view from just behind the plane, following it.
COMMAND_ACK: The MAVLink reply to a command. result is 0 when the plane accepts it, and 2 when the plane refuses it. For an agent plan, result_param2 gives the reason of a refusal.
Computer pilot: An opponent in the games that the sim flies. Each computer pilot flies a T1-S on the same physics as your plane, and has its own skill. Kestrel is an ace, Merlin flies at a club level and Swift is a rookie.
CRSF: The serial protocol of ExpressLRS radio links. The TX15 and the flight computer use it on their serial line: channels one way, telemetry and MAVLink the other.
CRUISE: The mode of ArduPilot for forward flight that holds the height and the heading. The sticks steer the plane, and the autopilot does the rest. Use it to travel.
Current item: The mission item that the plane flies to in AUTO. The map shows it in magenta. WP1 sends the plane back to the first item.
Cut: A turn inside a pylon in a pylon race. One cut adds 10 % to your time. Two cuts disqualify you.
Differential thrust: When you use the rudder, one motor turns faster and the other turns more slowly. Thus the plane turns more quickly in yaw than with the rudder only. X turns it on and off.
EKF: The extended Kalman filter of ArduPilot. It estimates the position, the velocity and the attitude of the plane from its sensors.
Evade: A primitive, number 2: break away from the track that the plan names. The plane flies fast, away from the threat and 20 m above or below it.
Executor: The code in the plane that flies an agent plan: cognition_executor, a Rust library. It turns the plan into a bank, a pitch and a throttle, 50 times a second. The same code runs in ArduPilot, in SITL and in the tests.
Fallback: What the plane does when it cannot fly its agent plan. AG_FALL tells you why: 1 when the plan ran out or its target went silent, 2 for bad input, 3 for a recovery.
FBWA: Fly By Wire A, a mode of ArduPilot. The sticks set the angle of bank and pitch, and the autopilot holds them. It is like ANGLE in the sim.
Fence: The circle that the safety envelope keeps the plane inside: a geofence. AGENT_FENCE_N and AGENT_FENCE_E set its centre in metres from home, and AGENT_FENCE_R sets its radius. If AGENT_FENCE_R is 0, the circle geofence of ArduPilot is used.
Flight computer: The device between the TX15 and the autopilot. The TX15 sends it the stick and switch channels on a serial line. It passes them on to ArduPilot as the radio channels, and it sends the plane's state back to the TX15. In the sim, a simulated flight computer does this.
Floor: The lowest height above the ground that the safety envelope allows, set with AGENT_FLOOR. Below it, the plane climbs before it flies the plan again. On a flat field, the height above the ground and the height above home are the same.
FPV: First-person view: the picture from a camera in the nose of the plane. The camera points 20° up.
Game command: A MAVLink COMMAND_INT with the command 31011 that tells a plane the state of the game of tag: its role, the time left and the plane that it cannot tag back. A plane takes it in any mode.
Go to: A primitive, number 3: fly to the point of the plan, then circle it.
Ground control agent: The program on the ground that decides an agent plan for each plane, about once a second. Its brain can be a script, a trained network or a person. The scripted brain plays tag as the computer pilots do.
GUIDED: The mode of ArduPilot that flies the plane to one point. GOTO on the map puts the plane in GUIDED.
Hand launch: A launch where you throw the plane into the air. The plane does not use a runway. You launch the T1-S Ranger in this way, and also the plane in the sim.
Home: The point where you armed the plane. RTL brings the plane back to it. The map shows it.
HUD: The text on the view of the sim. The top line shows the flight mode, the rates and differential thrust. The lines below it show the controller, the view, the throttle, the speeds, the height, the attitude, the battery and the wind. Messages such as CRASHED and PAUSED (P) appear in the middle.
Intervention: A step where the safety envelope changes what the plan asks for. AG_ENV counts the interventions since the plane entered AGENT mode.
It: The plane that chases the others in a game of tag. The pilot who is it for the least time wins.
Line of sight: The view from the pilot box. You look at the plane as you do at the field. The HUD calls it LINE OF SIGHT, and the help screen calls it LOS.
LOITER: A mode of ArduPilot, a mission item and a primitive of an agent plan, number 6. Each one circles a point. The loiter primitive circles the place where the plane got the plan.
MANUAL: In the sim, the mode where the sticks move the control surfaces directly. Nothing helps you. In ArduPilot, the mode where the autopilot sends the sticks directly to the plane.
Marker: The symbol of another plane on the tactical map. A live marker is bright. A stale marker is dim and stays where the plane was last heard.
MAVLink: The protocol that ArduPilot and ground stations use to talk to each other.
Mission: The list of items that the autopilot flies in AUTO: waypoints, loiters, a takeoff, a landing or a return home. The map shows the mission on the vehicle as a solid line.
Orbit: A primitive, number 4: circle the point of the plan, at its radius and its altitude.
Pilot box: The place where you stand at the field to fly. The sim starts there, with the plane in your hand.
Pitch stick: The stick that moves the nose up and down. On the keyboard, W pushes it forward (nose down) and S pulls it back (nose up).
Plan: The mission that you edit in the ground station. The map shows it as a dashed line. When you upload it, it becomes the mission on the vehicle. In Flying by plan, a plan is an agent plan.
Plan altitude: The height above home for new waypoints. It shows between ALT- and ALT+.
Primitive: The kind of agent plan: pursue, evade, go to, orbit, band or loiter. AG_PRIM gives it as a number from 1 to 6, and 0 for no plan.
Pursue: A primitive, number 1: chase the track that the plan names, and stay on its tail, just outside the separation.
Pylon: A tall marker on the field. In a pylon race, the three pylons mark the turns of the course. Fly round the outside of each one.
Pylon race: A race round a triangle of three pylons, as in the pylon racing leagues. G starts one. Five laps make a race. The first pilot across the start line after the last lap wins.
QHOVER: A hover mode of ArduPilot for a VTOL. The throttle stick sets the climb or the descent. The plane does not hold its place, so the wind moves it.
QLOITER: A hover mode of ArduPilot for a VTOL that also holds the plane at one place. Use it to take off and land.
QRTL: The mode of ArduPilot for a VTOL that flies the plane to home and lands it straight down.
Rates: How far the control surfaces move for a movement of the stick. High rates give tight turns. Low rates give gentle turns. L changes between them.
Recovery: A fallback, number 3: the plane is below the floor or the stall margin. It gets its height or its airspeed back first. Then it flies the plan again.
Remote ID: A broadcast that an unmanned aircraft sends on Bluetooth or Wi-Fi. It says who the aircraft is and where it is, about once a second. Any receiver near the aircraft can read it. The standard is ASTM F3411. Many countries ask for it.
Roll stick: The stick that banks the plane. On the keyboard, A rolls the plane to the left and D rolls it to the right.
RTL: Return to launch: ArduPilot flies the plane back to home. RTL is also a mission item that does the same.
Runner: cognition_runner, a program that flies three ArduPlane SITL planes with no window, faster than real time. With --agent, the ground control agent flies them in a game of tag. With --console as well, you send agent plans to the first plane after the game. Type plan, again, mode, wait, watch, status, reset or quit.
Safety envelope: The part of the executor that checks each demand before the plane flies it. It keeps the plane inside the fence, between the floor and the ceiling, clear of other aircraft and above the stall margin. A plan cannot switch it off.
Sensor feed: The window that shows the picture from the camera below the nose of the plane, with the sensor symbols on it. The ground station can point the camera.
Separation: The smallest distance to another aircraft that the safety envelope allows, set with AGENT_SEP. The envelope keeps a buffer round it, of at least 3 m. Across or above and below, the larger distance counts.
SITL: Software in the loop. ArduPilot runs on your computer, not on a flight controller. The sim gives it the physics and the sensors of the plane.
Stall margin: The airspeed that the plane must keep over AIRSPEED_MIN, set with AGENT_ASPD_MRG. Below AIRSPEED_MIN plus this margin, the safety envelope gets the airspeed back first.
T1-S Ranger: The plain plane of the sim (--aircraft t1s-ranger): two motors, a V-tail, and only a receiver and two ESCs, so it has no flight controller and one flight mode, MANUAL. You throw it by hand and fly it from the keyboard or a radio.
T1-S VTOL: The other plane of the sim, and its default (--aircraft t1s-vtol): the T1-S airframe with two tilt-rotors and a rear rotor, and a flight controller. ArduPilot flies it, and you fly it from the ground control station.
Tactical map: The map of the valley in the ground station, on the screen with the title TACTICAL SITUATION. It shows the plane, home, the plan and the mission on the vehicle.
Tag: A game where one plane is it and chases the others. When it touches another plane, that plane is it. In the simulator, T starts one. The runner plays one with ArduPilot planes.
Telemetry link: The radio link that brings the data of the plane to the station. The station gets it from the TX15. The link is narrow, so the plane sends its own data first.
tilt-rotor: A motor that can turn between pointing up and pointing forward. In a hover it lifts the plane like a copter rotor. In forward flight it pushes the plane like the motor of a plane.
Time to live: How long an agent plan is good for, in seconds, from when the plane gets it. If no new plan comes in this time, the plane circles where it is.
Track: Another aircraft as the plane knows it: its id, its position, its velocity and the time since the plane heard it. The ground sends tracks as ADSB_VEHICLE messages. The plane ignores a track that it has not heard for 3 s.
transition: The change between a hover and forward flight. The plane does it while it flies: the wing motors tilt, and the wing takes the weight from the rotors, or gives it back.
VTOL: An aircraft that takes off and lands vertically (Vertical Take-Off and Landing), like a copter, and flies forward on its wing, like a plane. The T1-S VTOL is one.
Waypoint: A point that the plane flies to, at a set height. Most items in a mission are waypoints.