This lesson examines:

• Recommended maintenance
• Preflight inspection requirements
• Loading considerations
• Performance considerations
• The effects of weather

Maintenance for sUAS includes scheduled and unscheduled overhaul, repair, inspection, modification, replacement, and system software upgrades for the unmanned aircraft itself and all components necessary for flight. 

This first section of the lesson examines maintenance requirements and best practices.

Manufacturers may recommend a maintenance or replacement schedule for the unmanned aircraft and system components based on time-in-service limits and other factors. Follow all manufacturer maintenance recommendations to achieve the longest and safest service life of the sUAS.

If the sUAS or component manufacturer does not provide scheduled maintenance instructions, it is recommended that you establish your own scheduled maintenance protocol. 

For example:

• Document any repair, modification, overhaul, or replacement of a system component resulting from normal flight operations
• Record the time-in-service for that component at the time of the maintenance procedure 
• Assess these records over time to establish a reliable maintenance schedule for the sUAS and its components

During the course of a preflight inspection, you may discover that an sUAS component requires some form of maintenance outside of the scheduled maintenance period.

For example, an sUAS component may require servicing (such as lubrication), repair, modification, overhaul, or replacement as a result of normal or abnormal flight operations. Or, the sUAS manufacturer or component manufacturer may require an unscheduled system software update to correct a problem.

In the event such a condition is found, do not conduct flight operations until the discrepancy is corrected.In some instances, the sUAS or component manufacturer may require certain maintenance tasks be performed by the manufacturer or by a person or facility (personnel) specified by the manufacturer. 

It is highly recommended that the maintenance be performed in accordance with the manufacturer’s instructions. However, if you decide not to use the manufacturer or the personnel recommended by the manufacturer and you are unable to perform the required maintenance yourself, you should:

• Solicit the expertise of maintenance personnel familiar with the specific sUAS and its components
• Consider using certificated maintenance providers, such as repair stations, holders of mechanic and repairman certificates, and persons working under the supervision of a mechanic or repairman

If you or the maintenance personnel are unable to repair, modify, or overhaul an sUAS or component back to its safe operational specification, then it is advisable to replace the sUAS or component with one that is in a condition for safe operation. 

Complete all required maintenance before each flight—preferably in accordance with the manufacturer’s instructions or, in lieu of that, within known industry best practices.

Before beginning any sUAS flight operation:

• Assess the operating environment
• Inform any supporting crewmembers about the operation and their roles
• Inspect the sUAS to ensure that it is in a condition for safe operation
• Maintain documents required in the event of an on-site FAA inspection

Before an sUAS operation, assess the operating environment.

The assessment must include, but is not limited to:

• Local weather conditions
• Local airspace and any flight restrictions
• The location of persons and property on the surface
• Other ground hazards

Before any sUAS operation, at a minimum, ensure that all persons directly participating in the sUAS operation are informed about:

• Operating conditions
• Emergency procedures
• Contingency procedures
• Roles and responsibilities of each person involved in the operation
• Potential hazards

Before any sUAS operation, inspect the aircraft for equipment damage or malfunctions.

For example, ensure that:

• All control links between the control station and the small unmanned aircraft are working properly
• There is sufficient power to continue controlled flight operations to a normal landing
• Any object attached or carried by the small unmanned aircraft is secure and does not adversely affect the flight characteristics or controllability of the aircraft
• The unique identifier is readily accessible and visible upon inspection of the small unmanned aircraft

Visit the Resources page to access a sample preflight inspection checklist.

Careful recordkeeping can be highly beneficial for sUAS owners and operators. For example, recordkeeping provides essential safety support for commercial operators who may experience rapidly accumulated flight operational hours/cycles.

Consider maintaining a hardcopy and/or electronic logbook of all periodic inspections, maintenance, preventative maintenance, repairs, and alterations performed on the sUAS.

Such records should include all components of the sUAS, including the:

• Small unmanned aircraft itself
• Control station
• Launch and recovery equipment
• Data link equipment
• Payload
• Any other components required to safely operate the sUAS

You must make available to the FAA, upon request, the sUAS for inspection or testing.

In addition, you must verify before flight that all required documentation is physically or electronically available in the event of an on-site FAA inspection. Such documentation may include:

• Pilot certificate
• Aircraft registration
• Any necessary waiver or exemption
• Other documentation related to the operation

Prior to each flight, the Remote PIC must ensure that any object attached to or carried by the small unmanned aircraft is secure and does not adversely affect the flight characteristics or controllability of the aircraft.

This next section of the lesson describes:

• Loading considerations
• Techniques for evaluating sUAS performance during flight

As with any aircraft, compliance with weight and balance limits is critical to the safety of flight for sUAS. An unmanned aircraft that is loaded out of balance may exhibit unexpected and unsafe flight characteristics.

Before any flight, verify that the unmanned aircraft is correctly loaded by determining the weight and balance condition.

• Review any available manufacturer weight and balance data and follow all restrictions and limitations
• If the manufacturer does not provide specific weight and balance data, apply general weight and balance principals to determine limits for a given flight. For example, add weight to the unmanned aircraft in a manner that does not adversely affect the aircraft’s center of gravity (CG) location—a point at which the unmanned aircraft would balance if it were suspended at that point.

Although a maximum gross takeoff weight is normally specified for a given unmanned aircraft, the aircraft may not be able to launch with this load under all conditions. Or if it does become airborne, the unmanned aircraft may exhibit unexpected and unusually poor flight characteristics.

Factors that may require a reduction in weight prior to flight include:

• High density altitude conditions
  • High elevations
  • High air temperatures
  • High humidity
• Runway/launch area length
• Surface
• Slope
• Surface wind
• Presence of obstacles

Excessive weight reduces the flight performance in almost every respect. In addition, operating above the maximum weight limitation can compromise the structural integrity of an unmanned aircraft.

The most common performance deficiencies of an overloaded aircraft are:

• Reduced rate of climb
• Lower maximum altitude
• Shorter endurance
• Reduced maneuverability

Weight changes have a direct effect on aircraft performance.

Fuel burn is the most common weight change that takes place during flight.

For battery-powered unmanned aircraft, weight change during flight may occur when expendable items are used on board (e.g., agricultural use). Changes of mounted equipment between flights, such as the installation of cameras, battery packs, or other instruments, may also affect the weight and balance and performance of an sUAS.

Unmanned airplane performance can be decreased due to an increase in load factor when the airplane is operated in maneuvers other than straight and level flight.

The load factor increases at a terrific rate after a bank has reached 45° or 50°. The load factor for any aircraft in a coordinated level turn at 60° bank is 2 Gs. The load factor in an 80° bank is 5.76 Gs. The wing must produce lift equal to these load factors if altitude is to be maintained. The Remote PIC should be mindful of the increased load factor and its possible effects on the aircraft’s structural integrity and the results of an increase in stall speed.

As with manned aircraft, an unmanned airplane will stall when critical angle of attack is exceeded. Due to the low altitude operating environment, consideration should be given to ensure aircraft control is maintained and the aircraft isn’t operated outside its performance limits. The load factor on wings may be increased anytime the airplane is subjected to maneuvers other than a straight line. Stalls occur when the wing exceeds it's critical angle of attack.

A small unmanned aircraft may not carry hazardous material as defined in 49 CFR part 171.8:

“Hazardous material means a substance or material that the Secretary of Transportation has determined is capable of posing an unreasonable risk to health, safety, and property when transported in commerce, and has designated as hazardous under section 5103 of Federal hazardous materials transportation law (49 U.S.C. 5103). The term includes hazardous substances, hazardous wastes, marine pollutants, elevated temperature materials, materials designated as hazardous in the Hazardous Materials Table (see 49 CFR 172.101), and materials that meet the defining criteria for hazard classes and divisions in part 173 of subchapter C of this chapter.”

Lithium batteries that are installed in an sUAS for power during the operation are not considered a hazardous material under part 107.

However, spare (uninstalled) lithium batteries would meet the definition of hazardous material and may not be carried on the sUAS.

Performance or operational information may be provided by the manufacturer in the form of an Aircraft Flight Manual, Pilot’s Operating Handbook, or owner’s manual. Follow all manufacturer recommendations for evaluating performance to ensure safe and efficient operation.

Even when specific performance data is not provided, the Remote PIC should be familiar with:

• The operating environment
• All available information regarding the safe and recommended operation of the sUAS

The Remote PIC is responsible for ensuring that every flight can be accomplished safely, does not pose an undue hazard, and does not increase the likelihood of a loss of positive control.

Consider how your decisions affect the safety of flight. For example:

• If you attempt flight in windy conditions, the unmanned aircraft may require an unusually high power setting to ascend. This action may cause a rapid depletion of battery power and result in a failure mode.
• If you attempt flight in wintery weather conditions, ice may accumulate on the unmanned aircraft's surface. Ice increases the weight and adversely affects performance characteristics of the small unmanned aircraft.

Due to the diversity and rapidly-evolving nature of sUAS operations, individual Remote PICs have flexibility to determine what equipage methods, if any, mitigate risk sufficiently to meet performance-based requirements, such as the prohibition on creating an undue hazard if there is a loss of aircraft control.

The FAA acknowledges that some manufacturers provide comprehensive operational data and manuals, such as Aircraft Flight Manuals or Pilot’s Operating Handbooks, and others do not. When operational data is provided, follow the manufacturer’s instructions and recommendations.

Even when operational data is not supplied by the manufacturer, the Remote PIC can better understand the unmanned aircraft's capabilities and limitations by establishing a process for tracking malfunctions, defects, and flight characteristics in various environments and conditions. Use this operational data to establish a baseline for determining performance, reliability, and risk assessment for your particular system.

Even though sUAS operations are often conducted at very low altitudes, weather factors can greatly influence performance and safety of flight.

Specifically, factors that affect sUAS performance and risk management include:

• Atmospheric pressure and stability
• Wind and currents
• Uneven surface heating
• Visibility and cloud clearance

As with any flight, the Remote PIC should check and consider the weather conditions prior to and during every sUAS flight.

This section of the lesson describes the effects of weather on aircraft performance.

Wind and currents can affect sUAS performance and maneuverability during all phases of flight. Be vigilant when operating sUAS at low altitudes, in confined areas, near buildings or other manmade structures, and near natural obstructions (such as mountains, bluffs, or canyons).

Consider the following effects of wind on performance:

• Obstructions on the ground affect the flow of wind, may create rapidly changing wind gusts, and can be an unseen danger
  • The intensity of the turbulence associated with ground obstructions depends on the size of the obstacle and the primary velocity of the wind
  • Even when operating in an open field, wind blowing against surrounding trees can create significant low level turbulence
• High winds may make it difficult to maintain a geographical position in flight and may consume more battery power

Remember that local conditions, geological features, and other anomalies can change the wind direction and speed close to the Earth’s surface.

For example, when operating close to a building, winds blowing against the building could cause strong updrafts that can result in ballooning or a loss of positive control. On the other hand, winds blowing over the building from the opposite side can cause significant downdrafts that can have a dramatic sinking effect on the unmanned aircraft.

Different surfaces radiate heat in varying amounts.

The resulting uneven heating of the air creates small areas of local circulation called convective currents. Convective currents can cause bumpy, turbulent air that can dramatically affect the Remote PIC's ability to control unmanned aircraft at lower altitudes.

For example:

• Plowed ground, rocks, sand, and barren land give off a large amount of heat and are likely to result in updrafts
• Water, trees, and other areas of vegetation tend to absorb and retain heat and are likely to result in downdrafts

As in manned aircraft operations, good visibility and safe distance from clouds enhances the Remote PIC’s ability to see and avoid other aircraft. Similarly, good visibility and cloud clearance may be the only means for other aircraft to see and avoid the unmanned aircraft.

The regulatory requirements for visibility and cloud clearance are discussed in a later module. But it should be noted here that adherence to the regulatory requirements in conjunction with good airmanship and effective scanning techniques can preclude in-flight collisions. And collision avoidance is an essential aspect to the safe integration of sUAS into the NAS.

This lesson examined preflight requirements for sUAS.

In summary, the Remote PIC is responsible for maintenance and pre-flight inspection of the sUAS, safe loading techniques, and continuous assessment of performance in flight.

You should now be able to describe:

• Recommended maintenance procedures for sUAS
• Inspection requirements to verify that the sUAS is in a condition for safe operation
• Considerations for safe loading of unmanned aircraft
• Procedures for evaluating performance
• The effects of weather on performance

The next lesson examines sUAS operating rules.