Preflight Checklist: Maintenance and Inspection

As we’ve mentioned several times throughout this course, the responsibility to inspect the drone(s) to ensure its in a safe operating condition rests solely with the remote pilot in command. And as required by part 107, the remote pilot must also conduct a preflight inspection to include the aircraft and control station systems checks, and to ensure the sUAS is in a condition for safe operation. Establishing a preflight checklist not only ensures the safety of all of the crewmembers, it also creates a flight log that the remote pilot can use to provide proof of the chain of events that lead up to flight operation and flight itself.

You can never be too careful when operating your sUAS for commercial purposes, and creating and establishing a flight log and checklist can help prove your innocence in case someone in the public domain tries to press false charges against you for human or property damage you’re not responsible for. There are many downloadable checklist apps available online, but be aware that some are dated and do not adhere to recent FAA changes. One app that I like is the Hover app which is free, but in addition to the flight log, it also includes a simple fly/no-fly indicator, fly zones, and real-time weather too and it will email your manually-entered flight log information to you too. Remote pilots have a lot of options to just Google “sUAS flight logging apps” and you’ll have plenty to choose from.

§107.49 Preflight Familiarization, Inspection, and Actions for Aircraft Operation

Prior to flight, the remote pilot in command must:

A. Assess the operating environment, considering risks to persons and property in the immediate vicinity, both on the surface and in the air. This assessment must include:

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

B. Ensure that all persons directly participating in the small unmanned aircraft operation are informed about the operating conditions, emergency procedures, contingency procedures, roles and responsibilities, and potential hazards;

C. Ensure that all control links between ground control station and the small unmanned aircraft are working properly;

D. If the small unmanned aircraft is powered, ensure that there is enough available power for the small unmanned aircraft system to operate for the intended operational time; and

E. Ensure that any object attached or carried by the small unmanned.

Preflight Checklist – Maintenance and Inspection

Although the FAA does not provide or mandate a specific type of preflight checklist, one best practice is to check your sUAS before leaving your office or home and of course again at the job site. A typical preflight inspection might include:

• Airspace unrestricted or flight authorized; potential obstructions near flight path?
• Weather and visibility: 3 miles, 500 ft below cloud base, wind <15mph, rain none?
• sUAS air frame & propellers okay; no structural defects visible?
• sUAS battery charged, not less than 75%?
• sUAS remote controller charged, not less than 75%?
• Display device charged?
• sUAS memory card installed, sufficient memory available?
• Camera gimbal lock removed?
• Power up display, controller, sUAS; all okay?
• sUAS status lights flashing green?
• Check camera view?
• Compass calibration or current location if required?
• Set flight altitude limits (height <120 meters (394 feet AGL); distance <500 meters)?
• Set flight mode to GPS controller?
• Launch location clear with 25 foot radius, no overhead obstructions? No bystanders?
• Start sUAS and run at idle for 60 seconds, no abnormal noise?
• Ensure Home Point is set, or was automatically set?
• Hover sUAS for one minute and check flight and camera gimbal control; responses normal?

READY FOR FLIGHT

Scheduled and Non-scheduled Maintenance

Structural or Exterior Skin Cracking: Further inspect to determine scope of damage and existence of possible hidden damage that may compromise structural integrity. Assess the need and extent of repairs that may be needed for continued safe flight operations.

Delamination of Bonded Surfaces: Further inspect to determine scope of damage and existence of possible hidden damage that may compromise structural integrity. Assess the need and extent of repairs that may be needed for continued safe flight operations.

Liquid or Gel Leakage: Further inspect to determine source of the leakage. This condition may pose a risk of fire resulting in extreme heat negatively impacting aircraft structures, aircraft performance characteristics, and flight duration. Assess the need and extent of repairs that may be needed for continued safe flight operations.

Smell/Visual Detection of Electrical Burning or Arcing: Further inspect to determine source of the possible electrical malfunction. An electrical hazard may pose a risk of fire or extreme heat negatively impacting aircraft structures, aircraft performance characteristics, and flight duration. Assess the need and extent of repairs that may be needed for continued safe flight operations.

Battery Casing Bulging/Distorted: EXTREME CAUTION!  Further inspect to determine integrity of the battery as a reliable power source. Distorted battery casings may indicate impending failure resulting in abrupt power loss and/or explosion. An electrical hazard may be present, posing a risk of fire or extreme heat negatively impacting aircraft structures, aircraft performance characteristics, and flight duration. Assess the need and extent of repairs that may be needed for continued safe flight operations.

Control Inputs Not Synchronized or Delayed: STOP!  Discontinue flight and/or avoid further flight operations until further inspection and testing of the control link between the ground control unit and the aircraft. Ensure accurate control communications are established and reliable prior to further flight to circumvent possible loss of control resulting in the risk of a collision or flyaway. Assess the need and extent of repairs that may be needed for continued safe flight operations.

Diminished Flight Time Capacity: Further inspect to determine integrity of the battery as a reliable power source. Diminishing battery capacity may indicate impending failure due to exhausted service life, internal, or external damage. An electrical hazard may be present, posing a risk of fire or extreme heat negatively impacting aircraft structures, aircraft performance characteristics, and flight duration. Assess the need and extent of repairs that may be needed.

Noticeable Sound Decibel Change/Propellers: Further inspect entire aircraft with emphasis on the propulsion system components (i.e., motors and propellers) for damage and/or diminished performance. Assess the need and extent of repairs that may be needed for continued safe flight operations.

Loose/Missing Hardware Fasteners: Further inspect to determine structural integrity of the aircraft and/or components with loose or missing hardware/fasteners. Loose or missing hardware/fasteners may pose a risk of negatively impacting flight characteristics, structural failure of the aircraft, dropped objects, loss of the aircraft, and risk to persons and property on the grounds. For continued safe flight operations, secure loose hardware/fasteners. Replace loose hardware/fasteners that cannot be secured. Replace missing hardware/fasteners.

Strong Fuel Smell: Further inspect to determine source of the smell. Leakage exiting the aircraft may be present and/or accumulating within a sealed compartment. This condition may pose a risk of fire resulting in extreme heat negatively impacting aircraft structures, aircraft performance characteristics, and flight duration. Assess the need and extent of repairs that may be needed for continued safe flight operations.

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In-Flight Emergency Procedures

An in-flight emergency is an unexpected and unforeseen serious occurrence or situation that requires urgent, prompt action. An in-flight emergency could be a bird strike, sudden loss of GPS satellite communications that result in flyaway, failure of being able to retain or regain control of your sUAS, or perhaps in-flight fire as a result of the LiPo battery malfunctioning.

In case of an in-flight emergency, the remote pilot is permitted to deviate from any rule of part 107 to the extent necessary to respond to that emergency, and is only required to send a written report to the FAA explaining the deviation upon FAA or Administrator’s request. In all situations, emergency action should be taken in such a way as to minimize injury or damage to property. A key part of emergency operations planning is to preempt and understand everything and anything that can go wrong during a flight operator, and then planning for your course of action.

An example of an emergency maneuver might include pressing your Return to Home (RTH) button on your remote controller, completely switching from automatic to manual mode; reducing or increasing your altitude to avoid a bird strike; or even maintaining a safe and static altitude level until the emergency passes.

Other emergency maneuvers may be necessary in the event you find yourself in a head-on collection with another aircraft. Remember we discussed in a previous lesson on “see and avoid” maneuvers, and the same procedures remain in force here… the remote pilot must yield right-of-way to all other manned aircraft.

Hazardous Flight Operations

As previously discussed, sUAS operations over people that are not directly involved as a crewmembers are prohibited, and sUAS operations are not allowed interfere with manned aircraft operations. Loading the sUAS beyond its capabilities to the point of losing control can also lead to a hazardous flight, as well as not observing weather conditions, nearby structures, trees, or flying in densely populated areas. Flying near emergency responders, firefighters or police during a crisis cannot only interfere with a first responder’s job, it can lead to creating additional hazards or injury.

Guy Wires

Many structures exist that could significantly affect the safety of your UA flight when operating below 400 feet AGL, and particularly below 200 feet AGL. Most cell and broadcasting towers are supported by guy wires which can extend up to 1,500-2,000 feet horizontally from a structure. These wires are extremely difficult to see even in good weather. If you’re hired to photograph a tower, the FAA recommends to fly at least 2,000 feet horizontally from these structures to be clear of guy wires. Overhead transmission and utility lines, construction cranes, tall trees, or flocks of birds all could promote a hazardous flight operation.

Flying Near Thermal Plumes, Smoke Stacks and Cooling Towers

Exhaust plumes are defined as visible or invisible emissions from power plants, industrial production facilities, or other industrial systems that release large amounts of vertically directed unstable gases. High temperature exhaust plumes can cause significant air disturbances such as turbulence and vertical shear. Other identified potential hazards include, but are not necessarily limited to reduced visibility, oxygen depletion, motor particulate contamination, exposure to gaseous oxides, and/or icing. Encountering one of these plumes may cause airframe damage and/or motor damage or failure.

These hazards are most critical during low-altitude flight in calm and cold air. When able, you should remain clear of exhaust plumes by flying on the upwind side of smokestacks or cooling towers.
When a plume is visible via smoke or a condensation cloud, remain clear and realize a plume may have both visible and invisible characteristics. Exhaust stacks without visible plumes may still be in full operation, and airspace in the vicinity should be treated with caution.

Flying Beneath Unmanned Balloons

The majority of unmanned free balloons have either a suspension device to which the payload or instrument package is attached or a trailing wire antenna extending below them, so extreme care must be exercised when flying your sUAS near unmanned balloons. Remote pilots are encouraged to report any unmanned free balloons sightings to the nearest FAA ground facility.

Wingtip Vortices

Wingtip vortices are circular patterns of rotating air left behind the wing of a large aircraft as it generates lift. The vortices are greatest when the aircraft is heavy, slow and developing full power, such as takeoff. In such a situation, the wingtip vortices tend to sink below the aircraft generating turbulence. While it’s rare that you’ll be operating close-enough to large aircraft where you’d experience wingtip vortices, this is something to keep in mind given how light small unmanned aerial systems are compared to their larger manned aircraft counterparts. In addition, this may be a question that may appear in your knowledge exam too. Wingtip vortices created by larger aircraft tend to sink below the aircraft generating turbulence.

Flying in the wire environment (flying near electric infrastructures)

The sUAS Knowledge exam consists of sections and subsections of 14 CFR part 107, Advisory Circular publications, and also several Safety Alert for Operator (SAFO) publications. An SAFO contains important safety information and may include recommended action, and its content should be especially valuable to air carriers in meeting their statutory duty to provide service with the highest possible degree of safety in the public interest.

One SAFO publication dated August 2010 specifically addresses “flying in the wire environment.” Operating an aircraft below 1,000 feet is when you’re flying in the wire environment.
The helicopter community in the United States, and world-wide, perform their critical operations typically at 1000 ft or less and more often, in a wire/obstruction rich environment where an increase of accidents between aircraft and manmade obstacles have occurred. A 13 year query of the National Transportation Safety Board (NTSB) database indicates a total of 996 reported aviation accidents/collisions involving wires/power lines in the United States and of those 996 accidents, 301 involved at least one fatality. That averages out to 76.6 accidents annually and with fatalities in 30% of the accidents.

The FAA wants you to know and be aware of “flying in the wire environment.”

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Proper Storage and Transportation of Lithium Ion Polymer Batteries (LiPo)

Lithium (LiPo) batteries present a risk of both igniting and fueling fires in aircraft cargo/baggage compartments. To reduce the risk of lithium battery fires, the U.S. Department of Transportation’s Hazardous Materials Regulations (HMR), and equivalent International Civil Aviation Organization’s Technical Instructions for the Safe Transport of Dangerous Goods (ICAO TI), prohibit spare lithium batteries from checked baggage (including baggage checked at the gate or on-board the aircraft). The term “spare” refers to lithium batteries not installed in a portable electronic device.

Always store your LiPo batteries in a cool, dry place and at “room temperature,” and never is a hot garage or in the refrigerator either. Your battery charging/discharging and storage area should be free from any materials that can catch fire, and the ideal charging surface area should be cool and dry such as concrete or ceramic. Never charge, discharge, use, or store a damaged or puffy LiPo battery, and never buy used LiPo batteries either.

Each LiPo battery must be individually protected so as to prevent short circuits by placement in original retail packaging, by insulating terminals by taping over exposed terminals, or placing each battery in a separate plastic bag or protective pouch, and take steps to prevent crushing, puncturing, or creating pressure on the battery.

Proper Storage and Transportation of Lithium Ion Polymer Batteries (LiPo)

Always use a fireproof LiPo safety bag, metal ammo box, or other fireproof container when you are charging, discharging, or storing your LiPo batteries, and never charge your batteries unattended. While LiPo fires are rare, they can happen incredibly quickly and can do a lot of damage. I recommend purchasing explosion/fire proof LiPo storage bags to store your LiPo batteries in, and you can find dozens of options online for just $10-$15.

Never leave your LiPo batteries sitting around on a full charge for more than 2-3 days. If by the third day you know that you’re not going to use your battery that day, you need to discharge your battery down to 3.6v-3.8v per cell for safe storage until you are ready to use the battery again.

And never discharge a LiPo battery below 3.0 volts per cell. Ideally, you never want to let the charge fall below 3.2 volts per cell in order to maintain a healthy battery, and 2.9 volts per cell or lower can cause permanent damage. LiPo batteries are a fantastic design and will provide approximately 300 charge cycles before needing to be replaced when properly cared for.

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Lost Link Procedures

A small unmanned aircraft system uses radio frequencies (RF) in the 2.4 GHz and 5.8 GHz, which are the same frequencies used by many home and office wireless router systems. Dense housing and office complexes and buildings can sometimes present interference with sUAS operations, and care should used if conducting flight operations near such area.

Preparing for Failure

Lost link is an interruption or loss of the control link between the control station and the unmanned aircraft, preventing control of the aircraft. As a result, the unmanned aircraft performs pre-set lost link procedures.

Such procedures ensure that the unmanned aircraft:

Remains airborne in a predictable or planned maneuver, allowing time to re-establish the communication link;
Autolands, if available, after a predetermined length of time or terminates the flight when the power source is depleted;
A lost link is an abnormal situation, but not an emergency, but a lost link is not considered a flyaway.

Contingency planning should include an alternate landing/recovery site to be used in the event of an abnormal condition that requires a precautionary landing away from the original launch location. Incorporate the means of communication with crewmembers (if used), as well as a plan for ground operations and securing/parking the aircraft on the ground. This includes the availability of control stations capable of launch/recovery, communication equipment, and an adequate power source to operate all required equipment. Take into consideration all airspace constructs and minimize risk to other aircraft by avoiding congested areas to the maximum extent possible.

Flyaways

A flyaway begins as a lost link, or an interruption or loss of the control link, that prevents control of the aircraft.  As a result, the unmanned aircraft is not operating in a predictable or planned manner.  Unlike in a lost-link connection, a flyaway is the result of the pre-programmed lost link procedures are not being executed by the unmanned aircraft, creating an emergency situation. If a flyaway occurs while operating in controlled airspace, it’s advisable that the remote pilot notify ATC as quickly as possible.

Congratulations! You’ve completed Lesson 9 on sUAS Preflight Checklists and Emergency Procedures. Be sure to click the COMPLETE button below to register your progress.