Chương 4 / 510% của kỳ thi
Loading and Performance
How much you hang on the aircraft, and where you hang it, changes how it flies long before it changes whether it flies at all. This chapter covers the 55-pound limit, center of gravity, the way payload eats into endurance and stability, battery behavior in heat and cold, and how to read the performance limits the manufacturer publishes.
Weight, the 55-Pound Limit, and Payload
A small unmanned aircraft is defined by weight, and the definition includes everything carried or attached at the moment of takeoff. That means the airframe, batteries, camera, gimbal, spray tank, and any mount all count against the same number. Manufacturers publish a maximum takeoff weight that is usually far below the regulatory ceiling, and that lower number is the one that actually governs your flight. Exceeding either limit is a compliance problem and a safety problem at the same time, because an overloaded aircraft climbs poorly, responds slowly, and stresses its motors and structure.
Under 55 pounds at takeoff
A small unmanned aircraft weighs less than 55 pounds on takeoff, including everything that is on board or otherwise attached to the aircraft.
14 CFR §107.3The manufacturer's maximum takeoff weight is the real limit
Published maximum gross weight reflects tested motor, structure, and battery margins, and staying under it is part of operating the aircraft in a condition for safe operation.
14 CFR §107.15Secure every payload
Anything attached must be mounted so it cannot shift, detach, or contact the propellers, since a released object can create an undue hazard to persons or property.
14 CFR §107.23No hazardous materials as cargo
Part 107 flights may not carry hazardous material, which rules out many chemicals, compressed gases, and certain battery shipments.
14 CFR §107.36Property carriage stays intrastate and inside the weight limit
When transporting property for compensation or hire, the aircraft and its cargo must together remain under 55 pounds, and the flight may not cross state or international boundaries.
Center of Gravity and Balance
Center of gravity is the point where the aircraft would balance if it were suspended, and every airframe has a manufacturer-defined range in which that point must stay. Mounting a camera far forward or a battery far aft moves the center of gravity out of that range and forces the flight controller to hold a constant correction. On a multirotor this shows up as motors on one side running hotter and draining faster, which quietly shortens flight time and can trigger an early power warning. On a fixed-wing aircraft an aft center of gravity reduces longitudinal stability and makes the aircraft pitch-sensitive and hard to recover, while a forward center of gravity increases stall speed and control forces.
Keep the CG within the published envelope
Load the aircraft so the center of gravity stays inside the range specified in the manufacturer's manual for the configuration you are flying.
Mount payloads at or near the balance point
Placing heavy items close to the center of gravity minimizes the correction the flight controller must apply and keeps motor loads even.
A shifting load shifts the CG in flight
Liquids in a tank, a swinging camera, or a cargo release changes balance while airborne, so account for the condition both before and after any drop.
Aft CG hurts stability
A rearward center of gravity makes the aircraft less stable in pitch and slower to return to level after a disturbance.
Forward CG raises control forces and stall speed
A nose-heavy fixed-wing aircraft needs more elevator authority and stalls at a higher airspeed, which shortens the margin during slow flight and landing.
How Payload Affects Endurance, Stability, and Control
Every additional ounce must be held up by additional thrust, and additional thrust is bought with current from the battery. That is why endurance falls off faster than weight rises: a payload that adds twenty percent to gross weight can easily cost more than twenty percent of flight time. Heavier aircraft also accelerate, decelerate, and turn less crisply, so the aircraft needs more room to stop and more lead time to avoid an obstacle. Wind makes this worse, because holding position against a gust while already near maximum thrust leaves nothing in reserve.
Added weight costs endurance disproportionately
Higher gross weight demands more motor current at hover, so flight time drops faster than weight increases.
Heavier means less responsive
Greater mass increases inertia, lengthening stopping distance and slowing the aircraft's reaction to control inputs and to obstacles.
Thrust margin shrinks as weight grows
Near maximum gross weight the motors have little reserve power left for gusts, sudden climbs, or an aggressive avoidance maneuver.
Drag from external mounts matters
Brackets, spotlights, and parachute pods add aerodynamic drag as well as weight, increasing power required especially in forward flight.
Load factor increases stall speed
In a banked turn a fixed-wing unmanned aircraft experiences a load factor greater than one, which raises the speed at which it will stall.
Plan a landing reserve
Set a return-to-home threshold that leaves enough energy for the trip back plus a wind allowance, rather than flying to the low-battery alarm.
Batteries, Temperature, and Power Management
Lithium polymer batteries deliver most of a small drone's performance and cause most of its surprises. Cold reduces usable capacity and increases internal resistance, so a battery that shows a full charge in a warm car may sag badly within a minute of a winter takeoff. Heat is the other extreme: charging or discharging a hot pack accelerates aging and, in the worst case, leads to thermal runaway and fire. Preflight includes verifying that there is enough power for the intended flight, and that verification should account for temperature, payload, and wind rather than assuming the advertised flight time.
Verify sufficient power before every flight
The remote PIC must confirm that all systems and the power supply are sufficient to operate the aircraft for the intended operation.
14 CFR §107.49Cold cuts usable capacity
Low temperature raises internal resistance and lowers voltage under load, so warm packs before use and expect shorter flights in the cold.
Heat accelerates damage
Do not charge a hot pack or leave batteries in a closed vehicle in the sun; excess heat shortens life and increases the risk of thermal runaway.
Retire swollen or damaged packs
A puffed, punctured, or physically damaged battery is unairworthy and must be removed from service rather than flown one more time.
Watch voltage under load, not at rest
A pack can read acceptable at rest and still sag below the safe minimum during a full-throttle climb, which is when an in-flight failure is most likely.
Store at the recommended charge state
Long-term storage at full charge degrades lithium cells; follow the manufacturer's storage voltage guidance between jobs.
Performance Limits and Manufacturer Data
The performance section of the manufacturer's manual is the primary source for what your specific aircraft can do, and the exam expects you to treat it as authoritative. It typically publishes maximum takeoff weight, maximum wind resistance, service ceiling, operating temperature range, and expected flight time at a given weight. Those numbers are measured in near-ideal conditions, so real-world density altitude, payload, and wind all erode them. Building a personal margin into every published limit is what separates a repeatable commercial operation from an eventual incident.
The manual is the authoritative performance source
Operate within the maximum takeoff weight, wind limits, altitude ceiling, and temperature range published for your make and model.
14 CFR §107.15Published figures assume ideal conditions
Advertised flight time usually reflects a hover at sea level with no payload and no wind, so discount it for the actual job.
High density altitude reduces available thrust
At high elevation or high temperature the propellers move less dense air, which lowers climb performance and maximum payload.
Respect the wind limit as a total, not a gust
A maximum wind rating assumes sustained wind; gusts, rotors near buildings, and turbulence can exceed the aircraft's authority even when the average is within limits.
Do not exceed 100 miles per hour groundspeed
Regardless of what the airframe can do, the regulatory groundspeed limit for Part 107 operations is 100 miles per hour.
14 CFR §107.51Kiểm tra kiến thức của bạn
Câu hỏi luyện tập về Loading and Performance