GadgetGuy
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The FAA’s Thoughts on Night Operations
The FAA gave us very insightful comments on pages 42,102-103 of the Operation and Certification of Small
Unmanned Aircraft Systems that was published in the Federal Register.
“Nighttime operations pose a higher safety risk because the reduced visibility makes it more difficult for the person maintaining visual line of sight to see the location of other aircraft. While the existence of other lighted manned aircraft may be apparent due to their lighting, the distance and movement of small unmanned aircraft relative to the distance and movement of those aircraft is often difficult to judge due to the relative size of the aircraft. In addition, visual autokinesis (the apparent movement of a lighted object) may occur when the person maintaining visual line of sight stares at a single light source for several seconds on a dark night. For this reason, darkness makes it more difficult for that person to perceive reference points that could be used to help understand the position and movement of the lighted manned aircraft, the small unmanned aircraft, or other lighted object.
The lack of reference points at night is problematic for small UAS subject to part 107 because they are not required to have any equipage that would help identify the precise location of the small unmanned aircraft. As such, a remote pilot in command operating under this rule will generally rely on unaided human vision to learn details about the position, attitude, airspeed, and heading of the unmanned aircraft. This ability may become impaired at night due to a lack of reference points because all a remote pilot may see of his or her aircraft (if it is lighted) is a point of light moving somewhere in the air. For example, a lighted small unmanned aircraft flying at night may appear to be close by, but due to a lack of reference points, that aircraft may actually be significantly farther away than the remote pilot perceives. An impairment to the remote pilot’s ability to know the precise position, attitude, and altitude of the small unmanned aircraft would significantly increase the risk that the small unmanned aircraft will collide with another aircraft.
In addition to avoiding collision with other aircraft, remote pilots in command must also avoid collision with people on the ground, as well as collision with ground-based structures and obstacles. This is a particular concern for small UAS because they operate at low altitudes. When operating at night, a remote pilot may have difficulty avoiding collision with people or obstacles on the ground which may not be lighted and as a result, may not be visible to the pilot or the visual observer. As such, this rule will not allow small UAS subject to part 107 to operate at night (outside of civil twilight) without a waiver. . .
Civil twilight is a period of time that, with the exception of Alaska, generally takes place 30 minutes before official sunrise and 30 minutes after official sunset. The FAA agrees with commenters that operations during civil twilight could be conducted safely under part 107 with additional risk mitigation because the illumination provided during civil twilight is sufficient for terrestrial objects to be clearly distinguished during clear weather conditions. As a result, many of the safety concerns associated with nighttime operations are mitigated by the lighting that is present during civil twilight. That is why current section 333 exemptions permit twilight UAS operations. Accordingly, this rule will allow a small UAS to be operated during civil twilight.
However, while civil twilight provides more illumination than nighttime, the level of illumination that is provided during civil twilight is less than the illumination provided between sunrise and sunset. To minimize the increased risk of collision associated with reduced lighting and visibility during twilight operations, this rule will require small unmanned aircraft operated during civil twilight to be equipped with anti-collision lights that are visible for at least 3 statute miles.
A remote pilot in command may reduce the intensity of the anti-collision lights if, because of operating conditions, it would be in the interest of safety to do so. For example, the remote pilot in command may reduce the intensity of anti-collision lights to minimize the effects of loss of night vision adaptation. The FAA emphasizes that anti-collision lighting will be required under this rule only for civil twilight operations; a small unmanned aircraft that is flown between sunrise and sunset need not be equipped with anti-collision lights.
The FAA acknowledges that current exemptions issued under Public Law 112–95, section 333 allow civil twilight operations without a requirement for anti-collision lighting. However, the section 333 exemptions do not exempt small UAS operations from complying with § 91.209(a), which requires lighted position lights when an aircraft is operated during a period from sunset to sunrise (or, in Alaska, during the period a prominent unlighted object cannot be seen from a distance of 3 statute miles or the sun is more than 6 degrees below the horizon). As such, UAS currently operating under a section 333 exemption have lighting requirements when operating during civil twilight.
However, while current section 333 exemptions rely on position lighting, it would be impractical for this rule to prescribe specifications for position lighting for civil twilight operations because a wider range of small unmanned aircraft will likely operate under part 107. Position lighting may not be appropriate for some of these aircraft. Thus, instead of position lighting, small unmanned aircraft operating under part 107 will be required to have anti-collision lights when operating during civil twilight. The FAA also notes that meteorological conditions, such as haze, may sometimes reduce visibility during civil twilight operations. Accordingly, the FAA emphasizes that, as discussed in the following section of this preamble, this rule also requires that the minimum flight visibility, as observed from the location of the ground control station, must be no less than 3 statute miles.”
The FAA gave us very insightful comments on pages 42,102-103 of the Operation and Certification of Small
Unmanned Aircraft Systems that was published in the Federal Register.
“Nighttime operations pose a higher safety risk because the reduced visibility makes it more difficult for the person maintaining visual line of sight to see the location of other aircraft. While the existence of other lighted manned aircraft may be apparent due to their lighting, the distance and movement of small unmanned aircraft relative to the distance and movement of those aircraft is often difficult to judge due to the relative size of the aircraft. In addition, visual autokinesis (the apparent movement of a lighted object) may occur when the person maintaining visual line of sight stares at a single light source for several seconds on a dark night. For this reason, darkness makes it more difficult for that person to perceive reference points that could be used to help understand the position and movement of the lighted manned aircraft, the small unmanned aircraft, or other lighted object.
The lack of reference points at night is problematic for small UAS subject to part 107 because they are not required to have any equipage that would help identify the precise location of the small unmanned aircraft. As such, a remote pilot in command operating under this rule will generally rely on unaided human vision to learn details about the position, attitude, airspeed, and heading of the unmanned aircraft. This ability may become impaired at night due to a lack of reference points because all a remote pilot may see of his or her aircraft (if it is lighted) is a point of light moving somewhere in the air. For example, a lighted small unmanned aircraft flying at night may appear to be close by, but due to a lack of reference points, that aircraft may actually be significantly farther away than the remote pilot perceives. An impairment to the remote pilot’s ability to know the precise position, attitude, and altitude of the small unmanned aircraft would significantly increase the risk that the small unmanned aircraft will collide with another aircraft.
In addition to avoiding collision with other aircraft, remote pilots in command must also avoid collision with people on the ground, as well as collision with ground-based structures and obstacles. This is a particular concern for small UAS because they operate at low altitudes. When operating at night, a remote pilot may have difficulty avoiding collision with people or obstacles on the ground which may not be lighted and as a result, may not be visible to the pilot or the visual observer. As such, this rule will not allow small UAS subject to part 107 to operate at night (outside of civil twilight) without a waiver. . .
Civil twilight is a period of time that, with the exception of Alaska, generally takes place 30 minutes before official sunrise and 30 minutes after official sunset. The FAA agrees with commenters that operations during civil twilight could be conducted safely under part 107 with additional risk mitigation because the illumination provided during civil twilight is sufficient for terrestrial objects to be clearly distinguished during clear weather conditions. As a result, many of the safety concerns associated with nighttime operations are mitigated by the lighting that is present during civil twilight. That is why current section 333 exemptions permit twilight UAS operations. Accordingly, this rule will allow a small UAS to be operated during civil twilight.
However, while civil twilight provides more illumination than nighttime, the level of illumination that is provided during civil twilight is less than the illumination provided between sunrise and sunset. To minimize the increased risk of collision associated with reduced lighting and visibility during twilight operations, this rule will require small unmanned aircraft operated during civil twilight to be equipped with anti-collision lights that are visible for at least 3 statute miles.
A remote pilot in command may reduce the intensity of the anti-collision lights if, because of operating conditions, it would be in the interest of safety to do so. For example, the remote pilot in command may reduce the intensity of anti-collision lights to minimize the effects of loss of night vision adaptation. The FAA emphasizes that anti-collision lighting will be required under this rule only for civil twilight operations; a small unmanned aircraft that is flown between sunrise and sunset need not be equipped with anti-collision lights.
The FAA acknowledges that current exemptions issued under Public Law 112–95, section 333 allow civil twilight operations without a requirement for anti-collision lighting. However, the section 333 exemptions do not exempt small UAS operations from complying with § 91.209(a), which requires lighted position lights when an aircraft is operated during a period from sunset to sunrise (or, in Alaska, during the period a prominent unlighted object cannot be seen from a distance of 3 statute miles or the sun is more than 6 degrees below the horizon). As such, UAS currently operating under a section 333 exemption have lighting requirements when operating during civil twilight.
However, while current section 333 exemptions rely on position lighting, it would be impractical for this rule to prescribe specifications for position lighting for civil twilight operations because a wider range of small unmanned aircraft will likely operate under part 107. Position lighting may not be appropriate for some of these aircraft. Thus, instead of position lighting, small unmanned aircraft operating under part 107 will be required to have anti-collision lights when operating during civil twilight. The FAA also notes that meteorological conditions, such as haze, may sometimes reduce visibility during civil twilight operations. Accordingly, the FAA emphasizes that, as discussed in the following section of this preamble, this rule also requires that the minimum flight visibility, as observed from the location of the ground control station, must be no less than 3 statute miles.”
