Loading & Performance

Pitch (nose up or down), roll (left or right wing up or down for banked turns), and yaw (rotation round the vertical axis) on fixed wing aircraft (pictured above) have equivalents on quadcopters.  

For a quacopter, pitch is controlled by moving the right stick forward (nose down) or backward (nose up) causing the aircraft to move forward or backward.  Roll is controlled by moving the right stick left (tilt left) or right (tile right) causing the aircraft to move left or right.  Yaw is contolled by moving the left stick left or right, causing the nose of the aircraft to rotate left or right.  Remember, all of this happens because of differential speeds of the propellers.

Key points ...

• Maximum allowable ground speed of your aircraft is 87knots (100mph)

• Maximum allowable altitude is 400ft AGL ... unless flown with a 400ft radius of a structure, in which case it can be flown more than 400ft above the structure's uppermost height

Ways to determine speed  include ...

• GPS on the aircraft that reports ground sped

• Dead reckoning: measure time flying between points of known distance and do the math

• Use a radar gun

Ways to determine altitude include ...

• Altimeter or GPS on the aircraft

• Compare to height of known structure or terrain

• Measure 400ft on the ground to get perspective on how far it is and the visual size of the aircraft at that distance

Key points ...

• If you overload your aircraft (exceed maximum gross weight) you will not have enough lift to take off or to maintain flight

• Excess weight reduces flight performance, including climb rate, maximum altitude (MSL), endurance, and maneuverability

• If you push the center of gravity of your aircraft outside a safe envelope, you may not be able to control the aircraft.  In any event, your aircraft will be less stable.

• The center of gravity can change during flight (e.g., if you're taking on or jetissoning materials) and you must ensure it is always within the safe envelope

• Look to information from the manufacturer about gross weight and calculating center of gravity

• Load also increases when turning the aircraft - see load factor charts

Visit the FAA's Weight & Balance Handbook for many more details.

Airfoils - wings, propellors, rotors - create lift by moving through the air.  The angle at which an airfoil moves through the air - defined as the angle between the airfoil chord and relative wind - is called the angle of attack.  When the angle of attack increases into the 18-20 degree range - the critical angle of attack - the movement of air over the top of the airfoil becomes turbulent and lift is lost.  This is a stall and the aircraft will be pulled by gravity toward the ground.  The angle of attack must be reduced (nose down) to regain lift.  A stall can occur at any airspeed, attitude, or altitude once the critical angle of attack is exceeded. 

Vortex Ring State

Rotor-type remote aircraft are most likely to stall when descending rapidly in a vertical straight line.  The turbulence when doing this can disrupt lift through a phenomenon called vortex ring state - basically, the aircraft is descending into it's own downdraft and loses lift.  To avoid a vortex ring state, descend at a reasonable rate and with some lateral motion so that the aircraft is always moving out of the turbulence it creates.  To recover, add forward or sideways motion; do NOT try to ascend out of it because that will just make things worse.  Some modern drones have programming to prevent descent rapid enough to cause this problem.

• Density altitude ("thin" air), wind (changes power requirements), cold (ice formation), and excessive heat (overheating) can all reduce the performance of you aircraft

• As remote pilot in command, it is your responsibility to consider these factors