Section 107.51 Operating limitations for small unmanned aircraft. (2018)


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Section 107.51 Operating limitations for small unmanned aircraft.

A remote pilot in command and the person manipulating the flight controls of the small unmanned aircraft system must comply with all of the following operating limitations when operating a small unmanned aircraft system:

(a) The groundspeed of the small unmanned aircraft may not exceed 87 knots (100 miles per hour).

(b) The altitude of the small unmanned aircraft cannot be higher than 400 feet above ground level, unless the small unmanned aircraft:

(1) Is flown within a 400-foot radius of a structure; and

(2) Does not fly higher than 400 feet above the structure’s immediate uppermost limit.

(c) The minimum flight visibility, as observed from the location of the control station must be no less than 3 statute miles. For purposes of this section, flight visibility means the average slant distance from the control station at which prominent unlighted objects may be seen and identified by day and prominent lighted objects may be seen and identified by night.

(d) The minimum distance of the small unmanned aircraft from clouds must be no less than:

(1) 500 feet below the cloud; and

(2) 2,000 feet horizontally from the cloud.

My Commentary on Section 107.51 Operating limitations for small unmanned aircraft.

These can all be waived.

 

Advisory Circular 107-2 on Section 107.51 Operating limitations for small unmanned aircraft.

Operating Limitations for Small UA. The small UA must be operated in accordance with the following limitations:

• Cannot be flown faster than a groundspeed of 87 knots (100 miles per hour);
• Cannot be flown higher than 400 feet above ground level (AGL), unless flown within a 400-foot radius of a structure and does not fly higher than 400 feet above the structure’s immediate uppermost limit;
• Minimum visibility, as observed from the location of the CS, may not be less than 3 statute miles (sm); and
• Minimum distance from clouds being no less than 500 feet below a cloud and no less than 2000 feet horizontally from the cloud.

Note: These operating limitations are intended, among other things, to support the remote pilot’s ability to identify hazardous conditions relating to encroaching aircraft or persons on the ground, and to take the appropriate actions to maintain safety.

5.10.1 Determining Groundspeed. There are many different types of sUAS and different ways to determine groundspeed. Therefore, this guidance will only touch on some of the possible ways for the remote PIC to ensure that the small UA does not exceed a groundspeed of 87 knots during flight operations. Some of the possible ways to ensure that 87 knots is not exceeded are as follows:

• Installing a Global Positioning System (GPS) device on the small UA that reports groundspeed information to the remote pilot, wherein the remote pilot takes into account the wind direction and speed and calculates the small UA airspeed for a given direction of flight, or
• Timing the groundspeed of the small UA when it is flown between two or more fixed points, taking into account wind speed and direction between each point, then noting the power settings of the small UA to operate at or less than 87 knots groundspeed, or
• Using the small UA’s manufacturer design limitations (e.g., installed groundspeed limiters).

5.10.2 Determining Altitude. In order to comply with the maximum altitude requirements of part 107, as with determining groundspeed, there are multiple ways to determine a small UA’s altitude above the ground or structure. Some possible ways for a remote pilot to determine altitude are as follows:

• Installing a calibrated altitude reporting device on the small UA that reports the small UA altitude above mean sea level (MSL) to the remote pilot, wherein the remote pilot subtracts the MSL elevation of the CS from the small UA reported MSL altitude to determine the small UA AGL altitude above the terrain or structure;
• Installing a GPS device on the small UA that also has the capability of reporting MSL altitude to the remote pilot;
• With the small UA on the ground, have the remote pilot and VO pace off 400 feet from the small UA to get a visual perspective of the small UA at that distance, wherein the remote pilot and VO maintain that visual perspective or closer while the small UA is in flight; or
• Using the known height of local rising terrain and/or structures as a reference.

5.10.3 Visibility and Distance from Clouds. Once the remote PIC and VO have been able to reliably establish the small UA AGL altitude, it is incumbent on the remote PIC to determine that visibility from the CS is at least 3 sm and that the small UA is kept at least 500 feet below a cloud and at least 2,000 feet horizontally from a cloud. One of the ways to ensure adherence to the minimum visibility and cloud clearance requirements is to obtain local aviation weather reports that include current and forecast weather conditions. If there is more than one local aviation reporting station near the operating area, the remote PIC should choose the closest one that is also the most representative of the terrain surrounding the operating area. If local aviation weather reports are not available, then the remote PIC may not operate the small UA if he or she is not able to determine the required visibility and cloud clearances by other reliable means. It is imperative that the UA not be operated above any cloud, and that there are no obstructions to visibility, such as smoke or a cloud, between the UA and the remote PIC.

FAA’s Discussion on Section 107.51 Operating limitations for small unmanned aircraft from the Final Small Unmanned Aircraft Rule

The NPRM also proposed additional visibility and cloud-clearance requirements to ensure that the person maintaining visual line of sight has sufficient visibility to see and avoid other aircraft. Specifically, the NPRM proposed a minimum flight visibility of at least 3 statute miles from the location of the ground control station. The NPRM also proposed that the small unmanned aircraft must maintain a minimum distance from clouds of no less than: (1) 500 feet below the cloud; and (2) 2,000 feet horizontally away from the cloud. This rule will finalize these minimum-flight-visibility and cloud-clearance requirements as proposed in the NPRM but will make those requirements waivable.

Commenters including NAAA, ALPA, and Commonwealth Edison Company supported the proposed minimum flight visibility and distance-from-clouds requirements. Commonwealth Edison asserted that the proposed visibility requirements, in combination with the other proposed operational requirements, would “safeguard safety while recognizing reasonable commercial interests in such a rapidly evolving technological environment.” NAAA stated that the proposed requirements are consistent with the VFR visibility requirements under 14 CFR 91.155 and 91.115. The Professional Helicopter Pilots Association strongly agreed that “weather minimums be at least basic VFR.” ALPA also agreed that all operations must take place in visual meteorological conditions (VMC) with the identified cloud clearances. ALPA further recommended that it be made clear that the 3-mile visibility requirement for VMC does not mean that the visual-line-of-sight required elsewhere in the proposed regulation can necessarily be maintained at 3 miles.

Modovolate Aviation, NAMIC, the Property Drone Consortium, and a few individuals generally opposed the imposition of minimum flight visibility and distance from-cloud requirements. The commenters asserted that such requirements are unnecessary, given the visual-line-of sight requirement of § 107.31. Modovolate stated that it is unlikely that an operator can keep a small UAS in sight at a distance of 3 miles, so a separate weather-visibility requirement is redundant. Modovolate also stated that a small UAS operator cannot maintain visual contact with his small UAS if it is flown in a cloud, but he would be able to fly his small UAS closer than 500 or 1,000 feet to a well-defined cloud without risk.

The Professional Society of Drone Journalists (PSDJ), and Edison Electric Institute, individually and jointly with NRECA and APPA, recommended the removal of the cloud distance requirements altogether. PSDJ asserted that the proposed cloud distance requirements would render many types of weather coverage and research projects impossible and would also make it impossible for small UAS to replace high-risk manned flights, “such as inspecting tower, bridges, or other structures,” as contemplated by the NPRM. The Travelers Companies, Inc. recommended the removal of the requirement that small UAS maintain a distance of no less than 2,000 feet horizontally from a cloud, claiming it is not relevant or workable for pilots flying small UAS from the ground. Aerial Services added that the safety concerns associated with cloud clearance will be alleviated with automation, the maximum altitude restriction, and the restriction on the use of small UAS in the vicinity of airports.

Several other commenters generally supported the imposition of minimum flight visibility and cloud clearance requirements, but said the proposed minimum requirements should be reduced. Commenters including State Farm, AUVSI, the Unmanned Safety Institute, and DJI, argued that the minimum flight visibility and cloud distance should be reduced to 1 statute mile and changed to “remain clear of clouds.” AUVSI asserted that this reduced requirement will reflect the small size, low speeds, and additional operating limitations of small UAS.

EEI said the proposed regulation is too restrictive, especially in areas prone to low cloud cover. The commenter argued that, as long as the operator maintains visual line of sight with the small UAS, the aircraft should be permitted to navigate up to 500 feet, regardless of the elevation of the clouds above 500 feet. In a joint comment, EEI, NRECA, and APPA noted that under the proposed visibility rules, for every foot cloud cover dips below 1,000 feet, the small UAS dips a foot below 500 feet, so that cloud cover at 500 feet would ground all small UAS operations. The commenters suggested that operations in Class G airspace should be allowed up to 500 feet AGL, or the height of cloud cover, whichever is lower. Exelon Corporation further suggested the rule include permission to
operate on the transmission and distribution rights-of-way at altitudes not to exceed the tops of the structures plus 50 feet without weather visibility restrictions. The News Media Coalition suggested eliminating the flight-visibility and cloud-clearance requirements for UAS operated within the parameters in the blanket COA for section 333 exemptions. The specific parameters suggested by the commenter consisted of flight at or below 200 feet AGL and at least (a) 5 nautical miles from an airport having an operational control tower; (b) 3 nautical miles from an airport with a published instrument flight procedure, but not an operational tower; (c) 2 nautical miles from

As discussed earlier, under this rule, the remote pilot in command will be responsible for observing the operating environment for other aircraft and, if necessary, maneuvering the small unmanned aircraft to avoid a collision with other aircraft. However, there is a significant speed difference between a manned aircraft and a small unmanned aircraft. Under part 91, a manned aircraft flying at low altitude could travel at speeds up to 230 to 288 miles per hour (mph).86 On the other hand, a small unmanned aircraft operating under this rule will have a maximum speed of 100 mph and many small unmanned aircraft will likely have a far lower maximum speed.

Because of this difference in maximum speed, the remote pilot in command will need time to respond to an approaching manned aircraft. A minimum flight visibility requirement of 3 statute miles is necessary to ensure that the remote pilot in command can see far enough away to detect a manned aircraft near the area of operation in time to avoid a collision with that aircraft. Additionally, cloud clearance provisions that require the small unmanned aircraft to maintain a distance of at least 500 feet below the cloud and 2,000 feet horizontally away from cloud are necessary to reduce the possibility of having a manned aircraft exit the clouds on an unalterable collision course with the significantly slower small unmanned aircraft. Accordingly, this rule will retain the proposed minimum-flight visibility requirement of 3 statute miles and minimum cloud-distance requirements of 500 feet below the cloud and 2,000 feet horizontally away from the cloud.

In response to ALPA’s concern, the FAA clarifies that the minimum-flight visibility and visual-line-of-sight requirements of this rule are separate requirements that must both be satisfied. The visual-line-of-sight requirement of § 107.31 is intended to ensure that the person maintaining visual line of sight can see the small unmanned aircraft and the immediately surrounding airspace. It is unlikely that a person will be able to maintain visual line of sight of a small unmanned aircraft in compliance with § 107.31 if that aircraft is 3 miles away from him or her. Conversely, the 3-mile visibility requirement
of § 107.51 is intended simply to ensure that the person at the control station is able to see relatively larger manned aircraft that may rapidly be approaching the area of operation. Southern Company suggested that small UAS operations should mirror the VFR weather minimums for manned-helicopter flight and that the Special VFR minimums under 14 CFR 91.157 should also apply to small UAS operations to the extent available for helicopters. The commenter suggested that small UAS operations would satisfy the requirements for Special VFR flight, because only ATC authorization is necessary before Special VFR flight and all small UAS must receive an ATC clearance when operating in controlled airspace. The commenter also asserted that the use of helicopter minimums is appropriate in this rule because, like helicopters, a small UAS is highly maneuverable and easier to land than fixed-wing aircraft. The Small UAV Coalition similarly suggested that the FAA adopt the helicopter cloud-clearance test for small UAS.

The FAA acknowledges that the part 107 visibility requirements for small UAS operations in Class G airspace will be more stringent than the requirements of part 91. Part 91 allows aircraft operating in Class G airspace to operate with 1 statute mile visibility and simply requires the aircraft to keep clear of clouds. However, as numerous commenters pointed out, small UAS operating under this rule may, as a result of their size, be difficult to see for manned-aircraft pilots. Additionally, unlike manned aircraft, small unmanned aircraft will not be required to carry equipage, such as TCAS and ADS-B, that aids in collision avoidance. Because of the additional challenges with collision avoidance raised by small UAS operating under part 107, a more stringent visibility requirement is necessary than the one imposed by part 91 on manned-aircraft operations in Class G airspace.

Vail Resorts asked the FAA to reduce or eliminate cloud clearance requirements in certain terrain, or with certain mitigation in place (e.g., a lighting system on the small UAS). The commenter stated that the minimum-flight-visibility and distance-from-cloud requirements are unnecessarily restrictive in a high alpine environment where the potential for interaction with manned aircraft is incredibly remote, and can be mitigated by other limitations. Venture Partners asserted that its products will contain onboard technology and capabilities that will allow UAS to operate in adverse weather conditions.

The FAA agrees that there could be operations in areas where the likelihood of interaction with manned aircraft is reduced or in which the risk of collision with a manned aircraft is mitigated by other means (such as technological equipage). Accordingly, the FAA has made the visibility and cloud-clearance requirements of part 107 waivable and will consider individual operating environments and other mitigations as part of its review of a waiver request. The FAA plans to use data acquired as part of the waiver process to inform future agency actions that will further integrate UAS into the NAS.

The Airborne Law Enforcement Association requested an exception from the 3- mile minimum flight visibility requirement for public safety operations, saying that, with the visual-line-of-sight restriction, “there are many opportunities to safely utilize UAS technology to the benefit of public safety operations.” The Organization of Fish and Wildlife Information Managers recommended a disaster-response exemption from the 3- mile flight visibility requirement, asserting that UAS flights in conditions with less than 3 miles of visibility could be integral in protecting human life and natural research welfare in the event of a man-made or natural disaster.

As discussed earlier, this rule will not apply to public aircraft operations unless the operator chooses to conduct the operation as a civil aircraft. Thus, public aircraft operations, such as public safety operations conducted by law enforcement agencies, will not be subject to part 107. With regard to the other specific types of operations mentioned in the comments, as discussed previously, the minimum-flight-visibility and cloud clearance requirements of this rule will be waivable. Thus, operations conducted for salutary purposes, such as the ones mentioned by the commenters, could be authorized through the waiver process if the remote pilot establishes that the operation can safely be conducted under the terms of a certificate of waiver.

The Metropolitan Airports Commission, Airports Council International-North America, the American Association of Airport Executives, and Exelon Corporation recommended that the requirement for 3 miles of visibility be from the location of the small unmanned aircraft and not from the location of the ground control station. The Metropolitan Airports Commission stated that the 3-mile visibility requirement is based on a manned aircraft pilot’s vantage point positioned inside the aircraft, which provides a 3- mile observation radius around the aircraft to see and avoid potential hazards. Airports Council International-North America claimed that a 3-mile visibility requirement from the unmanned aircraft instead of the ground control station will prevent cases where the UAS operator operates an aircraft at the limit of the operator’s line of sight. Lloyd’s Market Association and the International Underwriting Association said the 3-mile minimum flight visibility requirement may be difficult to administer and police, and wondered if maximum wind speeds have been taken into account.

This rule will retain the requirement that the minimum visibility must be measured from the control station. The reason for this requirement is to allow the person manipulating the flight controls of the small UAS to see other aircraft that could be entering the area of operation. The person manipulating the small UAS flight controls will be located at the control station (since the control station is the interface used to control the flight), and thus the minimum-visibility requirement must be measured from the control station. With regard to the comment arguing that the 3-mile minimum flight visibility requirement may be difficult to administer and police, the remote pilot in command must, among other things, ensure that the small UAS operation complies with part 107.

This rule will not impose prescriptive requirements on maximum permissible wind speed because there is a wide range of small UAS that could be operated under part 107. These UAS will have varying ability to respond to wind and a prescriptive regulatory requirement would be more stringent than necessary on certain small UAS while being less stringent than necessary on other UAS. Instead, § 107.49(a)(1) will require the remote pilot in command to assess local weather conditions as part of the preflight assessment required by § 107.49. If the remote pilot in command determines that the wind speed is too high to safely conduct the small UAS operation, then he or she will have to either reschedule the operation or implement mitigations to ensure the safety of the operation.

One commenter asked the FAA to clarify whether the 3-mile flight visibility requirement is horizontal visibility or slant angle visibility. The commenter asserted that there are many situations where radiation or advection fog might obscure horizontal visibility yet bright blue sky is visible above the fog.

The 3-mile flight visibility requirement is based on a slant angle from the control station. In other words, a person standing at the control station of the small UAS must be able to see at a diagonal distance of 3 miles into the sky in order to detect other aircraft that may be approaching the area of operation. This requirement ensures that the remote pilot in command can effectively observe the airspace for presence of other aircraft, and reduces the possibility of the remote pilot or visual observer losing sight of the unmanned aircraft.

To further clarify this concept, the FAA has amended § 107.51(c) to explain that flight visibility refers to the average slant distance from the control station at which prominent unlighted objects may be seen and identified by day and prominent lighted objects may be seen and identified by night.

The University of North Dakota’s John D. Odegard School of Aerospace Sciences suggested that the rule prohibit small UAS operations above clouds because those operations could endanger manned aircraft flying under instrument flight rules (IFR). In response, the FAA notes that a person is unlikely to be able to maintain visual line of sight of a small unmanned aircraft that is flying above the clouds.

Schertz Aerial Services, the Permanent Editorial Board of the Aviators Model Code of Conduct Initiative, and the City and County of Denver, Colorado suggested that the proposed flight-visibility and minimum-cloud-distance requirements be increased. Schertz Aerial Services said that because UAS are so much smaller than manned aircraft, the proposed 3-mile flight visibility requirement, which was developed for manned aircraft, is not adequate for UAS and should be increased to 5 statute miles. Denver also recommended increasing the minimum flight visibility requirement to 5 statute miles, but only in controlled airspace. The commenter additionally recommended the imposition of a 2,000-foot ceiling for operations in controlled airspace. “Those visibility enhancements,” Denver continued, “will maximize opportunities for both the operator and other aircraft pilots to successfully employ the see-and-avoid technique.”

One commenter said the minimum flight visibility requirement should be increased to 10 to 12 miles and the distance-from-cloud requirements should both be increased by 1,000 feet. Another commenter said the FAA should set a specific percentage or range for cloud coverage to be allowed during flight, in addition to the distance-from-cloud requirements.

The FAA recognizes the fact that increased flight visibility would provide more time for the remote pilot in command to maneuver away from other aircraft. However, the likelihood of the remote pilot seeing other small UAS, other smaller aircraft, or other hazards such as power lines or antennas from a distance of five or more miles is not probable, so such a requirement would not create an additional safety buffer. A 5-mile visibility requirement above 10,000 feet mean sea level (not including the surface to 2,500 feet above ground level) is imposed by part 91 because manned-aircraft pilots have a need for increased visibility at that higher altitude due to permitted airspeeds above 288 mph. A remote pilot in command, on the other hand, will remain on the ground and will have to deal with ground obstacles that impede vision. The remote pilot in command will also be looking into the sky at a slant angle from the ground rather than horizontally in the manner of a manned-aircraft pilot. This means that a remote pilot will generally be challenged to perceive useful information from his or her vision beyond three miles. An increase in the cloud distance requirements poses the same dilemma, unless the object is large enough or distinct enough it will not likely be visible early enough to provide the opportunity to avoid or change course sooner.

PlaneSense and Cobalt Air, commenting jointly, recommended prohibiting a remote pilot from operating a small UAS if the ceiling is lower than 1000 feet MSL. The commenters contended that for manned aircraft, the pilot is in the aircraft and is therefore better able to make a determination about the distance to a cloud from the aircraft than an operator on the ground positioned 1/4 mile away from the unmanned aircraft.

The FAA declines to prohibit small UAS operations when cloud ceilings are lower than 1,000 feet AGL.87 Specifically, the FAA disagrees that the remote pilot in command will not be in a position to determine whether the unmanned aircraft is positioned sufficiently far enough from a cloud to meet the requirements of § 107.51(d). While this rule does not require specific technological equipage to determine altitude of the unmanned aircraft, nothing in this rule precludes the remote pilot in command from doing so as a means to mitigate the risk of cloud clearance requirements. A remote pilot in command may also opt to operate the unmanned aircraft at a sufficiently low altitude that he or she can easily determine the aircraft’s altitude. Further, cloud ceilings can be determined through nearby AWOS/ASOS/ATIS reports, visual cloud observations, or observation of obscuration of nearby prominent landmarks of a known elevation. If a remote pilot in command cannot ensure that the unmanned aircraft will maintain sufficient cloud clearance in accordance with § 107.51(d), that person may not conduct operations until weather conditions improve. As such, no minimum ceiling requirement is necessary in this rule.

Noting that the NPRM would not require a qualified weather observer, one commenter questioned who is responsible for determining visibility at the time of the operation. The commenter further questioned if the regulation has a requirement for the airman trained and certificated for small UAS to receive training and demonstrate competence in making accurate visibility determinations. Another commenter also questioned who determines visibility, and recommended that FAA require as a minimum that VMC exist and that the closest Official Weather Reporting Station be used. Under this rule, the remote pilot in command is ultimately responsible for determining whether a flight can be conducted safely. As part of the preflight assessment required by § 107.49, the remote pilot in command must evaluate local weather conditions, which includes an evaluation of whether those conditions are sufficient to meet the requirements of § 107.51(c) and (d). With regard to competence, as discussed in section III.F.2.j of this preamble, knowledge of aviation weather sources that can be used to inform the small UAS operation will be tested on both the initial and recurrent aeronautical knowledge test. The initial aeronautical knowledge test will also test the airman certificate applicant’s knowledge of effects of weather on small unmanned aircraft performance. For the reasons discussed in section III.F.2.e of this preamble, formal training and practical testing requirements are not a necessary component of this rule.

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ii. Vertical Boundary (Maximum Altitude)
Next, we turn to the vertical boundary of the confined area of operation. Because most manned aircraft operations take place higher than 500 feet above ground level (AGL), the NPRM proposed a 500-foot operating ceiling for small UAS operations. For the reasons discussed below, this rule will reduce the operating ceiling to 400 feet AGL unless the small unmanned aircraft: (1) is flown within a 400-foot radius of a structure, and (2) does not fly higher than 400 feet above the structure’s immediate uppermost limit. This operating-ceiling provision will be waivable.

Several commenters, including the Professional Photographers of America, ALPA, Boeing, Google, and State Farm, supported the 500-foot altitude limit proposed in the NPRM. Some noted that a 500-foot ceiling for UAS operations would strike a positive balance between flexibility for the UAS operator and the safety of manned aircraft operating in the NAS.

Other commenters, including Barrick Gold of North America, argued that the altitude restrictions in the rule are unnecessary because the current airspace stratification and operating rules already provide the requisite level of safety. Barrick added, however, that it would support a buffer of 200 feet below the terminus of Class G airspace. An altitude limit for small UAS operations is necessary in this rule. Given the expected proliferation of small UAS in the NAS, and the safety implications for manned aircraft, the FAA must address the safe use of small UAS in the NAS. Moreover, Congress has directed the FAA to establish a regulatory framework to safely integrate small UAS operations into the NAS. Allowing unrestricted small unmanned aircraft to operate at high altitude without the benefit of additional equipment (for example, transponders and altimeters) and the provision of air traffic services introduces a significant threat of collision to manned aircraft operating in the NAS. Most manned aircraft operations transit the airspace at or above 500 feet AGL, and an altitude limitation provides a necessary barrier between small unmanned aircraft and a significant majority of manned aircraft operations in the NAS. However, as discussed below, this rule will make an exception to the altitude restriction for small UAS operations that are conducted close to a structure. Other commenters, including Northrop Grumman Corporation, AOPA, EAA, and HAI, recommended a reduction in the proposed 500-foot altitude limit. These commenters were concerned about the potential for conflict with manned aircraft operating in the NAS. The United States Ultralight Association and the U.S. Hang Gliding and Paragliding Association expressed general concern regarding the volume of manned aircraft traffic below 500 feet and the potential for collisions with small unmanned aircraft.

While some commenters did not recommend a specific alternate maximum altitude, most that did favored a 400-foot operating ceiling. Commenters offered a variety of reasons to support a 400-foot altitude limit. One commenter justified a lower altitude by noting it is difficult for the operator to maintain visual contact with the small unmanned aircraft when operated above 500 feet, and a 400-foot limit would provide an added margin of safety. Most commenters stated that a 400-foot altitude limit would provide a reasonable buffer between UAS and manned aircraft operating in the NAS. NAAA remarked that recent narrowly averted collisions involving agricultural aircraft and UAS aircraft justify the establishment of a 400-foot limit. NAAA also noted the importance of the missions performed by aircraft at lower altitude, including agricultural and air ambulance operations. Northrop Grumman and the Aviation Division of the Washington State Department of Transportation asserted that a 500-foot altitude does not provide an adequate buffer between UAS operations and those conducted by manned aircraft.

Other commenters, including the North Central Texas Council of Governments, noted that the 100-foot difference between the limits for model aircraft and UAS aircraft, which would result from the proposed 500-foot altitude ceiling, would create confusion. These commenters pointed out that because it is difficult to distinguish between UAS and model aircraft, the two should have similar altitude restrictions.

Some commenters identified lower ceilings for UAS operations in other countries. For example, one commenter noted that Australia has established a 400-foot limit for UAS operations. Further, Transport Canada cited a similar approach for UAS operations in Canada, noting that a 400-foot operating ceiling provides a margin of safety that considers barometric altimeter error and cold weather temperature corrections.

Some commenters, however, asserted that even a 400-foot maximum altitude is too high. The Professional Helicopter Pilots Association recommended a limit of 200 feet to provide an adequate altitude buffer between UAS and rotorcraft operations. One commenter suggested a 200-foot limit until ADS-B is mandated for UAS. Positive air traffic control was also recommended as a requirement for operations above 200 feet. In contrast, several commenters, including those from the media and agricultural communities, asserted that the proposed 500-foot altitude limit for small unmanned aircraft operations is overly restrictive. One commenter stated that the 500-foot altitude ceiling increases the risk for striking terrain, power lines, or other structures. A commenter also noted that the proposed altitude restriction may contribute to a loss of communication with the aircraft due to terrain and other obstructions.

The most frequently cited reason for raising the altitude limit was to allow the small unmanned aircraft to more effectively perform missions such as search and rescue, aerial surveys, and other applications for industries ranging from agriculture to petroleum, as well as inspections of buildings, bridges and other structures. In addition, several commenters asserted that a 500-foot limit is impractical for radio-controlled soaring. Aerobatic operations would also be severely limited by a 500-foot restriction. Other commenters highlighted the needs of the media industry, remarking that a
500-foot restriction limits the utility of UAS for certain newsgathering operations.

Commenters noted that for these activities, the ability to operate at higher altitudes increases their ability to film news events and access other areas beyond normal reach. Some commenters, including the Nebraska Farm Bureau Federation, suggested that the 500-foot operating ceiling could be lifted under certain circumstances in remote areas given the uncongested airspace above remote areas. The American Petroleum Institute agreed that a case-by-case process is needed for approval to fly at higher altitudes. In its comments, API noted that the proposed rule effectively eliminates lower-resolution surveillance operations where larger ground sample distances would have value for a variety of activities over broad areas, such as pipeline right-of-way surveying and metocean (meteorology and physical oceanography used in offshore and coastal engineering) data gathering. In addition, in areas with high vegetation, this restriction acts to limit distances across which pre-programmed flights may function even if the visual line-of-sight restriction were modified. One commenter noted this would be similar to what is now codified in 14 CFR 91.119 (b) and (c), and to the precedent established by 14 CFR part 101.

Many commenters, such as Boeing and the News Media Coalition, also focused on the need to permit higher operating altitudes in proximity to certain structures. This would allow small unmanned aircraft to be used to perform inspections and other tasks that would traditionally place persons in harm’s way. The Exelon Corporation noted the need to allow for inspection of tall structures. An individual recommended that the FAA allow operations at higher altitudes within a 2,000-foot radius of certain towers. NoFlyZone.org asserted that UAS operations above 500 feet should be permitted within 250 feet of a structure as long as the operator has permission from that structure’s owner. Skycatch asked that operations above 500 feet be permitted under specific circumstances, such as bridge or building inspections as proposed by AUVSI. The Professional Society of Drone Journalists stated that the airspace above and around buildings should be considered to be the domain of legal UAS operations.

Commenters also recommended mechanisms to allow operations above 500 feet ranging from pilot training and equipment requirements (such as transponders and ADS-B), to the establishment of flight restriction areas or a waiver process. The American Insurance Association requested that UAS aircraft be allowed to operate above 500 feet if accompanied by a visual observer on the ground aided by a mechanical enhancement of his or her sight.

Other commenters noted that an increase in altitude may be appropriate in areas where the threat to manned aircraft is minimal. For example, one commenter proposed that in Class G airspace, the ceiling for UAS operations be raised to the base of the overlying controlled airspace. A variety of other altitudes were proposed. Clean Gulf Associates stated that 1,000 feet is an appropriate altitude, allowing for oil spill skimming targeting operations, where the mid-air threat over water is lower. Prioria Robotics also proposed 1,000 feet. The American Fuel & Petrochemical Manufacturers noted that technical developments in the near future will allow for operations up to 1,000 feet with additional equipage and procedural safeguards. Another commenter stated that if an under-10-pound category of UAS aircraft could be created, an altitude of 1,000 feet should be permitted. Another commenter offered that an increase in maximum altitudes is appropriate as size of the UAS aircraft increases. For example, a rotorcraft up to 4 kgs or a fixed-wing aircraft between 6 and 12 kgs would be able to fly up to 700 feet AGL. Rotorcraft up to 20 kgs and fixed wing up between 12 and 24 kgs would be able to fly up to 3,000 feet AGL. These altitude limits would be accompanied by pilot medical and training requirements, as well as additional equipage requirements, such as ADS-B.

One commenter noted that the rule is harsh toward non-hazardous UAS operations. This commenter argued that low-altitude quad copter operations should be given relief to operate at altitudes similar to those used for a commercial moored balloon or kite. The Resource Stewardship Consortia proposed an extension up to 1,400 feet for a proof of concept trial performed in places where the threat of collateral damage is minimal should a failure occur, and for operations that would benefit from a higher altitude.

In response to comments addressing the specific altitude limit, the FAA agrees that a 400-foot ceiling will allow for a significant number of applications for the small UAS community, while providing an added level of safety for manned-aircraft operations. A ceiling of 400 feet AGL will provide an additional 100-foot margin of safety between small UAS operations and a majority of aircraft operations in the NAS. This additional 100-foot buffer will help maintain separation between small unmanned aircraft and most manned aircraft in instances such as the remote pilot losing positive control of the small unmanned aircraft or incorrectly estimating the altitude of the aircraft.

Further, the revised limit addresses other concerns regarding potential confusion between model aircraft and small unmanned aircraft. Specifically, limiting operations to 400 feet is consistent with FAA guidance on model aircraft best practices identified in AC 91-57A, thus standardizing operating altitudes for the majority of small unmanned aircraft flying in the NAS. A 400-foot altitude ceiling is also consistent with the approach adopted in other countries. Specifically, Canada, Australia, and the United Kingdom all set a 400- foot or lower altitude limit on UAS operations conducted in those countries. While the FAA considered the lower altitudes proposed by commenters, it ultimately determined that these lower limits would unnecessarily restrict small UAS operations without a commensurate increase in safety because the concentration of manned aircraft below 400 feet AGL is much lower than the concentration of manned aircraft at or above 500 feet AGL. The FAA also considered the comment recommending positive air traffic control above 200 feet. The FAA ultimately rejected this recommendation because it is overly burdensome to both remote pilots and the air traffic control system. Air traffic controllers could not reliably provide positive separation for operations at this altitude throughout the NAS, and the benefits to users from such separation efforts would not justify the significant additional workload placed on air traffic controllers or the equipment and training costs to remote pilots. In addition, without additional equipment mandates, the provision of positive air traffic control would be unachievable.

To address the concerns expressed by commenters requesting higher operating altitudes in proximity to buildings, towers, power lines, and other tall structures for the purposes of inspections and repair, the FAA is establishing new provisions in the final rule that will enable those operations in a way that does not compromise aviation safety. Specifically, the FAA notes that 14 CFR 91.119 generally prohibits manned aircraft from operating in close proximity to structures. Section 91.119 requires manned aircraft to stay 500 to 1,000 feet away from the structure, depending on whether the area is congested. Because manned aircraft are not permitted to operate in close proximity to structures, this rule will allow a small unmanned aircraft to fly higher than 400 feet AGL as long as that
aircraft remains within a 400-foot radius of a structure up to an altitude of 400 feet above the structure’s immediate uppermost limit. Allowing higher-altitude small UAS operations within a 400-foot lateral limit of a structure will enable additional operations (such as tower inspection and repair) while maintaining separation between small unmanned aircraft and most manned aircraft operations.

The FAA disagrees that a further increase in altitude is justified. Higher-altitude small unmanned aircraft operating in airspace that is transited by most manned aircraft operations would no longer be separated from those manned aircraft, which would greatly increase the risks of a collision. Most remote pilots of small UAS would also benefit very little from an additional increase in altitude because the visual-line-of-sight restrictions of this rule and the equipment limitations of a small UAS would, in many cases, limit the ability or need to operate at altitudes higher than what is provided for by this rule. Such a limited benefit would not be commensurate with the added risk that a higher altitude would impose upon other users of the NAS.

However, the FAA recognizes that new technologies may increase the feasibility of higher altitude operations. Therefore, to provide flexibility to accommodate new developments, the altitude limitation of this rule will be waivable. Thus, if a remote pilot demonstrates that his or her high-altitude small UAS limitation will not decrease safety, the FAA may allow that operation through a certificate of waiver. This will enable a number of operations, such as research and development for higher-altitude small UAS operations. The FAA is committed to working with the stakeholder community to pursue such options when it is deemed appropriate.

With regard to search and rescue operations, most of these operations are conducted by government entities under COAs as public aircraft operations. Those operations will therefore not be subject to the altitude limitations of this rule.

Several commenters raised concerns regarding a remote pilot’s ability to discern the altitude of the small unmanned aircraft. Commenters including AOPA and GAMA asserted that current UAS lack accurate altimetry systems, making compliance with any altitude restriction difficult. GAMA asked that the FAA clarify how an operator determines the UAS altitude in flight. Similarly, one individual stated that while the altitudes proposed in the rule are in principle sound, they are unenforceable. Other commenters asserted that it is impossible to judge altitude, particularly over precipitous terrain, and that altitude restrictions of any kind may only be relied upon if UAS were required to have altitude limiting devices. The Permanent Editorial Board of the Aviators Model Code of Conduct
proposed that the FAA require the use of a practical technique for UAS operators to estimate their altitude with sufficient accuracy or require the use of a technical solution to ensure compliance.

Remote pilots have effective techniques to determine altitude without mandating the installation of an altimetry system. For example, with the unmanned aircraft on the ground, a remote pilot in command may separate him or herself 400 feet from the aircraft in order to gain a visual perspective of the aircraft at that distance. Remote pilots may also use the known height above the ground of local rising terrain and/or structures as a reference. The FAA acknowledges that these methods of estimating altitude are less precise than equipment-based altitude determinations, which is one of the reasons this rule will increase the separation between manned and small unmanned aircraft by reducing the maximum altitude for small unmanned aircraft to 400 feet AGL.

Additionally, the FAA will provide, in its guidance materials, examples of equipment options that may be used by remote pilots to accurately determine the altitude of their small unmanned aircraft. One example is the installation of a calibrated altitude reporting device on the small unmanned aircraft. This device reports the small unmanned aircraft’s altitude above mean sea level (MSL). By subtracting the MSL elevation of the control station from the small unmanned aircraft’s reported MSL altitude, the aircraft’s AGL altitude may be determined. The installation of a GPS altitude-reporting device may also provide for a requisite level of altitude control. The FAA emphasizes, however, that this equipment is simply one means of complying with the altitude restrictions in this rule. One commenter asked if the proposed 500-foot limit represents the altitude above the launch point or the height of the UAS altitude above the ground. The commenter noted that some topographical features present dramatic changes in altitude. Glider operators raised similar questions regarding altitude over sloping terrain.

The maximum altitude ceiling imposed by this rule is intended to limit the height of the aircraft above the ground over which it is flying (AGL). It is incumbent upon the remote pilot in command to maintain flight at or below this ceiling regardless of the topography.

Several commenters stated that the 500-foot altitude restriction does not address the public’s expectation that airspace (up to 500 feet) above private property is under their control and may not be penetrated without permission. Event 38 Unmanned Systems stated that the FAA should attempt to set a reasonable altitude requirement for overflight of property not controlled by any UAS operator. This commenter proposed a 100-foot limit for incidental incursions and a 300-foot limit for intentional flight across private property without permission. Another commenter suggested requiring small UAS to operate between 400 and 500 feet AGL when flying above private property, unless the remote pilot has obtained the property owner’s permission. Other commenters, including the NJIT
Working Group and the Kansas Livestock Association, commented on the relationship between the final rule requirements and trespass and nuisance protections for private landowners.

Adjudicating private property rights is beyond the scope of this rule. However, the provisions of this rule are not the only set of laws that may apply to the operation of a small UAS. With regard to property rights, trespassing on property (as opposed to flying in the airspace above a piece of property) without the owner’s permission may be addressed by State and local trespassing law. As noted in section III.K.6 of this preamble, the FAA will address preemption issues on a case-by-case basis rather than doing so in a rule of general applicability.

The North Central Texas Council of Governments opposed a 500-foot maximum altitude, stating it is inconsistent with Public Law 112-95 and the 400-foot ceiling identified in Advisory Circular (AC) 91-57.

Public Law 112-95 directs the Department to establish requirements for safe integration of UAS operations into the NAS but does not specify the altitude parameters of such operations. AC 91-57A is advisory in nature and pertains to model aircraft not subject to part 107. However, the 400-foot maximum altitude imposed by this rule is similar to the 400-foot maximum altitude suggested as a best practice for modelers by AC 91-57A. One commenter stated that the COA process should be maintained for operations outside of class G airspace and altitudes above 500 feet. However, with the exception of flight that is within 400 feet of a structure, small unmanned aircraft seeking to fly higher than 400 feet AGL will have to obtain a waiver to do so.

Several commenters recommended the creation of specialized airspace for UAS operations. This may include designated airspace for certain clubs, or the establishment of special airways or corridors. Farris Technology and the University Of Washington promoted the use of corridors or dedicated airways that will allow UAS flights above 500 feet.

Creation of UAS-specific airspace is beyond the scope of this rule because the NPRM did not propose to create any new airspace classifications or reclassify existing airspace.

One commenter suggested that the 500-foot restriction in Class G airspace should only be in place for rotorcraft UAS. However, after careful consideration, the FAA could not find a compelling reason to differentiate between fixed-wing and rotorcraft UAS for the purposes of altitude restrictions. For both aircraft, the threats posed to the NAS are similar. The UAS aircraft class itself does not mitigate those threats in any calculable manner. Therefore, a distinction based on UAS aircraft class is unwarranted. ALPA recommended a change to the preamble discussion regarding the maximum altitude. As currently written, the preamble to the NPRM states that a small unmanned aircraft is prohibited from “travel higher than 500 feet AGL.”95 ALPA recommended replacing the word “travel” with “fly” or “operate.” For added clarity, the FAA will use the terms “fly” or “operate” in discussing the maximum altitude limitation in this preamble.

Several commenters, including Green Vegans, stated that the proposed 500-foot operating ceiling would make it impossible to comply with 14 CFR 91.119, which
prescribes minimum altitudes for part 91 operations. Green Vegans questioned how a small UAS operator could remain in compliance with both part 107 and section 91.119. Except where expressly stated to the contrary, the provisions of part 107 will replace the provisions of part 91 for small UAS operations subject to this rule. Consequently, a small UAS operating under part 107 will not be required to comply with § 91.119

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The NPRM proposed a maximum air speed limit of 87 knots (100 mph) for small unmanned aircraft. The FAA explained that this speed limit is necessary because if there is a loss of positive control, an aircraft traveling at high speed poses a higher risk to persons, property, and other aircraft than an aircraft traveling at a lower speed. The NPRM also noted that a speed limit would have safety benefits outside of a loss-of-positive-control scenario because a small unmanned aircraft traveling at a lower speed is generally easier to control than a higher-speed aircraft. For the reasons discussed below, this rule will impose an 87-knot (100 mph) speed limit. This rule will, however, make the pertinent speed measurement the groundspeed rather than the airspeed of the small unmanned aircraft. The speed limit will also be waivable. Commenters including NAMIC, the Drone User Group Network, and the Remote Control Aerial Platform Association supported the proposed maximum airspeed. These commenters generally noted that the speed limitation of 100 mph seems reasonable for small UAS operating within visual line of sight.

Other commenters, including the Air Medical Operators Association, the Virginia Department of Aviation, and SWAPA, stated that FAA should lower the maximum permissible airspeed (e.g., to 50 or 75 mph) because, the commenters argued, the proposed speed of 100 mph is too high and would pose undue risks. Several commenters, including Texas A&M University, HAI, the Virginia Department of Aviation and others, asserted that the NPRM failed to demonstrate the safety of the proposed speed limitation. These commenters argued that it would be extremely difficult to maintain positive control of a small unmanned aircraft flying at 100 mph.

Some commenters, including the American Association for Justice, the United States Ultralight Association, and the State of Nevada, asserted that the kinetic energy of a 55-pound object moving at 100 mph could cause significant damage to large aircraft. The US Hang Gliding & Paragliding Association, the Metropolitan Airports Commission, and Predesa stated that a lower maximum speed would provide additional time for UAS operators and pilots of manned aircraft to see and avoid each other. Several of these commenters, including the Metropolitan Airports Commission and Kansas State University UAS Program, stated that a 100 mph speed limit would make it extremely difficult (if not impossible) for an operator to maintain visual line of sight with the unmanned aircraft. NBAA, the Airports Council International—North America and the American Association of Airport Executives recommended that the FAA conduct further study and risk assessment regarding appropriate speed limitations for this type of UAS. The Permanent Editorial Board of the Aviators Model Code of Conduct Initiative argued that FAA should establish a lower maximum speed that will create no greater harm than is caused by most birds (approximately 30 knots) until such time as further data demonstrates the safety of a higher speed limitation.

A speed limit of 87 knots (100 mph) must be viewed within the context of the overall regulatory framework of part 107. In other words, a small unmanned aircraft may reach a speed of 87 knots only if the remote pilot in command can satisfy all of the applicable provisions of part 107 while flying the small unmanned aircraft at 87 knots. For example, since this rule requires small UAS operations to be conducted within visual line of sight, a remote pilot in command may not allow the small unmanned aircraft to reach a speed where visual-line-of-sight cannot be maintained in accordance with § 107.31. Additionally, as discussed in section III.E.3.b.vi of this preamble, the remote pilot in command must, prior to flight, assess the operating environment and consider risks to persons and property in the vicinity both on the surface and in the air. The remote pilot in command must also ensure that the small unmanned aircraft will pose no undue hazard to other aircraft, people, or property in the event of a loss of control of the aircraft for any reason. Thus, if the remote pilot in command plans to have an operation in which the small unmanned aircraft will travel at 87 knots, that remote pilot will, as part of the preflight assessment process, need to take precautions to ensure that the unmanned aircraft will not pose an undue hazard to other aircraft, people, or property on the ground. Those precautions will likely be greater than the precautions that a remote pilot in command will need to take for a small unmanned aircraft traveling at a lower speed. Accordingly, a maximum speed limit of 87 knots is appropriate because the remote pilot in command will have to implement mitigations commensurate with the risk posed by his or her specific small UAS operation.

Other commenters, including Textron Systems recommended no limitations regarding airspeed, arguing that as long as the operator can maintain visual line of sight and control of the UAS, there should be no performance limitations.

A speed limit is generally necessary for small unmanned aircraft because an aircraft traveling at high speed poses a higher risk to persons, property, and other aircraft than an aircraft traveling at lower speed. As discussed earlier, the other parameters of this rule (such as visual line of sight and the preflight assessment conducted by the remote pilot in command) mitigate this risk for small unmanned aircraft traveling at speeds up to 87 knots. However, those parameters do not address the risk posed by small unmanned aircraft traveling at speeds faster than 87 knots. Accordingly, this rule will retain the proposed 87-knot speed limit but will make that limit waivable. As part of the waiver process, the FAA will consider operation-specific mitigations to address additional risk posed by higher-speed small UAS operations.

The Kansas State University UAS Program and SWAPA questioned whether there would be any commercial applications of small UAS that would necessitate a 100 mph airspeed. Further, several commenters, including Modovolate Aviation, asserted that many small UAS, such as those employing multi-rotor technology, may not need to or may not be able to reach a speed of 100 mph.

The FAA agrees that there will likely be small unmanned aircraft incapable of reaching a speed of 87 knots. The FAA also agrees that there will likely be small UAS operations that are incapable of satisfying the other provisions of this rule, such as visual line of sight, at a speed of 87 knots. However, that is not a sufficient justification for reducing the maximum permissible speed for all small unmanned aircraft because there may be small UAS operations that can reach a speed of 87 knots and operate safely at that speed in compliance with all applicable provisions of part 107.

The New Hampshire Department of Transportation noted that the FAA did not propose any specific equipage requirements for small UAS that would be used to determine airspeed. Similarly, CAPA stated that the NPRM does not require or define how the operator will maintain operations below a specified airspeed other than visually, which the commenter said would be very difficult to do when operating in congested airspace and scanning for other conflicts.

Aerius recommended that the FAA amend the proposed regulatory text to make any speed limitations based on groundspeed because many UAS are not equipped with a system that would provide airspeed to the small UAS operator. Several individuals noted that multi-rotor helicopter UAS cannot sense airspeed, only groundspeed. Another individual suggested that the regulatory text be amended to reference GPS-generated airspeed because all UAS do not have the equipment to provide airspeed to the operator.

As noted by the commenters, the provisions of this rule will not require small UAS to be equipped with a system that would provide calibrated airspeed to the remote pilot in command. The FAA also notes that the groundspeed of the small unmanned aircraft is what is pertinent to the safety of a small UAS operation because that is the information that specifies how quickly the aircraft is moving relative to the ground in proximity to where the remote pilot is located. Because changing the standard to groundspeed rather than calibrated airspeed would not have a detrimental effect on safety and because many unmanned aircraft may not have the equipage necessary to measure calibrated airspeed, the FAA agrees with the commenters and has changed the maximum airspeed standard to be a function of groundspeed. A small unmanned aircraft’s groundspeed could be determined by measures such as GPS-based speed, visual estimation, a radar gun, or timed travel across a fixed distance. This rule will retain the maximum speed limit of 87 knots (100 mph), but that limit will be a measure of groundspeed rather than airspeed.

A few individuals (who self-identified as recreational operators of model aircraft) said the proposed maximum speed would preclude them from holding certain types of model aircraft competitions. In response, the FAA emphasizes that, as discussed in section III.C.4 of this preamble, part 107 will not apply to model aircraft operations that meet the criteria of section 336 of Public Law 112-95.

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