Weight and Loading

If you put too much weight on your unmanned aircraft, it will have trouble flying. An overweight unmanned aircraft could result in the following conditions or requirements:

• Higher takeoff speeds

• Longer takeoff and launch runs;

• Reduced rate of climb;

• Lower maximum altitude;

• Shorter range;

• Reduced cruising speed;

• Reduced maneuverability;

• Higher stalling speed;

• Higher approach and landing speed; and

• Longer landing roll.

Caution at High Density Altitudes

When flying in conditions where there is a higher density altitudes (high altitude, high water vapor, etc. - remember back to our weather lectures), the UAV operator needs to be especially cautious about the loading of the unmanned aircraft, as extra load and high density altitude both decrease performance.

On a hot, muggy day, the air becomes “thinner” or less dense, and its density at a pilot’s location is equivalent to a higher altitude in the standard atmosphere. It is hazardous to aircraft during takeoff and climb because:

- Aircraft power is reduced. The engine will ingest less air to support combustion.

- Aircraft thrust is reduced. A propeller will have less "grip" on the air, while a jet engine will will exhaust less mass.

- Lift is reduced. The thinner air will exert less upward force on the airfoils.

As a result, a longer takeoff and landing roll is required, especially for a fully-loaded aircraft. After takeoff, the aircraft will have a smaller rate of climb and will have a lower service ceiling.

Density altitude is usually reported at each AWOS/ASOS station in the Remarks section of the METAR, if the value is greater than 1000ft higher than the elevation of the airfield. Here's an example:

METAR KMSY 291400Z AUTO 18006KT 10SM CLR 28/13 A3001 RMK SLP161 DENSITY ALT 1000FT