MIT Lincoln Labs responds to FAA UAS BVLOS request for comment

MIT Lincoln Laboratory has responded to the Federal Aviation Administration (FAA) request for comment on UAS Beyond Visual Line-of-Sight Operations. Technical representative Andrew Weinert posted notable excerpts from the response on the applicability of the ASTM F3442/F3442M–23 DAA Standard, well clear criteria, requirements within the Mode C veil, and shielded operations. He strongly recommends reviewing the entire comprehensive MIT LL response which can be accessed here.

Applicability of the ASTM F3442/F3442M–23 DAA Standard (C1)

The ASTM F3442/F3442M–23 “hockey puck” should be applicable in the following circumstances:

  • UAS encounters a crewed aircraft when the UAS is in Class E or G airspace or in lower altitudes within Class B, C, and D airspace
  • UAS has a maximum dimension of 25 feet or less (a MGTOW greater than 55 lbs is permittable)

Note that these circumstances extend the ASTM F3442/F3442M-23 defined scope, but align with the analysis used to establish the “hockey puck.”

It should not be used under these circumstances:

  • Requirement that the “hockey puck” never be violated and a loss of simultaneous separation of 2000 and 250 feet never occurs.
  • Class A airspace
  • Environments where the small UAS will frequently encounter crewed aircraft flying faster than 250 knots

Coordinated close-proximity small UAS to crewed aircraft operations (e.g., formation flight)

Alternative well clear criteria (C2)

The ASTM “hockey puck” was defined as a relative separation where a desired unmitigated risk threshold is achieved and informed by operational acceptability. Accordingly, maintaining 2000 ft (horizontally) or 250 ft (vertically) separation can be viewed as a general mitigation to reduce collision risk but will not be operationally suitable in all circumstances nor does the simple “hockey puck” take advantage of additional information or mitigations. If the 2000 and 250 ft “hockey puck” was codified by the FAA, the FAA could permit exemptions if an operator can demonstrate that with additional mitigations or information that a separation criteria corresponds to a 10% or less likelihood of an NMAC because this would satisfy the key design objective and assumptions of the “hockey puck.” An alternative would be to grant an exemption to the LoWC functional and performance requirements from ASTM F3442/F3442M-23, with the exemption either changing the performance requirement or not requiring it all together.

Requirements within Mode C Veil (E1)

General strategic deconfliction capabilities or procedures should be employed in all airspaces: this may include technical deconfliction capabilities or airspace constructs (e.g., operating altitude, location). No aircraft, including UAS, should be permitted to fly without mitigations to reduce airborne and ground risk. Specifically, strategic deconfliction services and conformance monitoring should be required within airspace classes A, B, C, and D and the lateral limits of a Mode C Veil because of the relatively high traffic density of crewed aircraft and complexity of the airspace around Class B airports and large metropolitan areas.

Conformance monitoring should not be required in Class E or G airspace, unless the operation requires strategic deconfliction and conformance monitoring to sufficiently reduce risk.

Operating Environments in which the FAA should not authorize shielded operations (G2)

Due to security risks, the FAA should limit operations in the National Capital Region airspace and near secure detention facilities. The FAA should also not authorize operations if the total risk near a specific critical infrastructure sector is not acceptable.

If operating in airspace classes A, B, C, or D, or within the lateral limits of a Mode C veil, the sUAS operator should have ADS-B In surveillance capabilities, and land or operate closer to the obstacle/infrastructure if the shielded area is compromised.

To minimize risk to airport operations, shielded operations should not be authorized, in the near-term, within 0.5 nautical mile from the end of a runway for all types of landing facilities (to include vertiports/heliports). Airport based keep out zones should be judiciously implemented.

Applicability of 100′ above and 100′ lateral offsets from an obstacle for shielded operations (G3)

The 100’ above and lateral offsets is supported by evidence from a 2019 analysis of helicopter air ambulance tracks near buildings in Boston and a 2021 analysis of aircraft broadcasting 1090 MHz ADS-B near point obstacles and bridges.

Both of these evidence sources could also be used to justify offsets greater than 100 feet and the FAA should make a data-driven decision for defining an appropriate offset.

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