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Certification and the UAS

By By David Downey and R&WI Staff | July 1, 2015



A DJI Phantom 2 Vision quadcopter. Photo from ThinkStock

Advocates for greater use of unmanned aerial systems in the U.S. insist that UASs can perform the same missions as aircraft with pilots aboard just as safely and reliably, but at much lower costs.

They argue that UASs often can be safer by sparing pilots from risking their lives unnecessarily in dangerous missions that might be better conducted unmanned.

“Whether it is assisting first responders with search and rescue missions, advancing scientific research or helping farmers more efficiently manage their crops, UASs will save time, money and, most importantly, save lives,” Brian Wynne, president/CEO of the Association for Unmanned Vehicle Systems International (AUVSI) told a June 17 hearing by the U.S. House of Representatives Committee on Oversight and Government Reform.

Many in the more traditional aviation community counter that such claims of safety and reliability are unsupported by the kind of heavily documented, extensive design analysis and testing that is at the heart of nearly every manned commercial aircraft flying today.

“Significant barriers exist for routine UAS access to civil U.S. airspace,” Dr. John Cavolowsky, director of NASA’s Airspace Operations and Safety Program, told that same hearing in summarizing the matter.

In addition to the safety and reliability of UASs, such barriers include unresolved questions about the ability of a UAS pilot on the ground to detect and avoid other aircraft or to use command and control communications frequencies without interfering with other users, as well as the wide variation in the size and performance characteristics of unmanned aircraft.

A key question in assessing the UAS market and the potential impact of such aircraft on commercial aviation is whether UASs could maintain their cost advantages if they are required to meet the same safety and reliability certification standards as manned rotorcraft.

This question is central to the UAS debate. The lack of demonstrated safety and reliability data is a primary reason why UASs are segregated from other aircraft in the skies­—and, in general, from people on the ground—by restrictions on where, when and how they can fly.

As one UAS manufacturer, Aero Kinetics of Fort Worth, Texas, has noted, “airworthiness and operational certification standards needed for commercial users and consistent access to the national airspace do not exist. As a result, UASs still have restrictive operating limits for commercial users.”

This month, we look at two aspects that drive the development, manufacturing and operating costs of manned aircraft and examine how they might affect the future costs—and the competitive advantage—of unmanned aircraft.

The first aspect covers the general requirements and procedures for type certification (under U.S. Federal Aviation Regulations, or FARs) of a rotorcraft and its systems for producing power to fly, controlling flight, navigating and communicating with air traffic controllers and other airborne aircraft.

The second aspect covers the current state of a UAS’s ability to detect and avoid other aircraft (referred to in manned aviation as see and avoid, and almost solely the responsibility of the pilot-in-command). We will look at the current level of confidence in UAS detect-and-avoid capability and the research and technical-standards development aimed at increasing this confidence.

UASs flying today for commercial purposes generally do so in one of two ways: they operate under a Restricted type certificate from the FAA, or they weigh less than 55 pounds and currently do not require any type of certification.

AeroVironment is among those seeking a full type certificate for UAS. Shown here is its Puma AE.
Photo courtesy of AeroVironment

A Restricted category type certificate (issued under FAR Part 21.25) permits an aircraft to be used for special-purpose operations if it complies with noise regulations and has no unsafe characteristics when flown within the limitations of its certificate. Aircraft in this category are used specifically for agricultural missions, forest and wildlife conservation, aerial surveying, pipeline/powerline/canal patrols, weather control, aerial advertising and other missions specified by the FAA.

The other aircraft operate under the FAA’s proposed rule for small UASs, which limits them generally to operations below 500 feet, beyond five miles of any airport and within the line of sight of an operator on the ground. They generally also are not permitted to fly over populated areas.

The process for obtaining an FAA aircraft type certificate that permits much less restricted operations is seemingly a maze of acronyms and frustration. It can take years to complete, depending on the size, complexity and mission of the aircraft. It also can cost a lot of money. For instance, Airbus Helicopters’ certification of its H175 super-medium, twin-engine aircraft for offshore oil and gas support and other missions is estimated to have cost more than $1 billion.

The FAA type certification process is outlined in FAR Part 21. The process for rotorcraft certification is identical to that used for airplanes and engines. Part 21 lays out time limits for completion of a project to gain type certification. For a Normal category (Part 27) rotorcraft type certificate, the limit is three years. For the Transport category (Part 29), it is five years.

A type certificate project is divided into several phases: pre-design, design, final design and test.

Pre-design includes determining the basic design end-points such as weight, range, speed, passenger count, mission profiles and reliability targets. It also is the phase in which the manufacturer determines whether the aircraft will be qualified for operation in instrument flight rules as well as visual ones. This phase yields design parameters that support the start of trade studies.

Everything in the design of a rotorcraft is a tradeoff. If you want range, then fuel capacity becomes a design end-point. More fuel means more structure to hold the fuel; the increased fuel and structural weight will influence crash survivability. More fuel means less payload. You can see that design decisions can become a multi-variable equation.

A manufacturer can start a type certificate project without FAA involvement. This can be advantageous by reducing risk on research and development efforts and design strategies.

Once the FAA becomes involved, there is a Pre-Type Board meeting with representatives from the FAA’s closest Aircraft Certification Office and the standards staff of its Rotorcraft Directorate, the manufacturer and, usually, the engine and avionics companies. In this meeting, the manufacturer lays out to the FAA the basic aircraft configuration, what it believes is the appropriate certification basis and what exemptions from that basis it intends to pursue.

The certification basis discussion addresses which part of the FARs applies to the desired type certificate, as well as which amendment of that part applies. Amendments are periodic updates of the part that do not call for a full rewrite of the certification rules.

 

The manufacturer is required, in its certification basis submission, to detail how it will satisfy, paragraph by paragraph, each section of Part 27 or 29 and the appropriate amendment. This is laid out in a Methods-of-Compliance table. It must annotate whether specific methods of compliance will be accomplished through flight test, ground test, analysis or design, by comparison with a similar (or use of an equivalent) level of safety or exemption.

Determining the certification basis is crucial. Imposition of a new compliance requirement or method of compliance can be costly and impact the timelines for the aircraft program. For instance, if a manufacturer proposes analysis as a method of compliance with fuel-tank crash worthiness but the FAA insists on a drop test, the resulting cost and time required may be higher than the OEM planned.

Keep in mind that many of the certification rules are intended to keep the pilots and occupants of an aircraft safe. Since that is not an issue for unmanned aircraft, many of those rules—and the costs incurred for their compliance—may never be a factor for UASs. Other certification rules, however, are aimed at keeping people and property on the ground safe from unsound aircraft, and they and their related compliance costs (including those related to continued airworthiness) may well apply to UASs.

Detect and avoid is an entirely different matter.

It is hard to imagine an agency like the FAA, which for very good reason is conservative and risk-averse, giving an aircraft relatively unlimited access to civil airspace without a demonstrated ability to steer clear of other aircraft and obstacles.

The aviation industry is just now developing the technical standards to define that capability and the specifications to which the avionics that will provide it will be built, certified, operated and maintained. Those standards will almost certainly become cost drivers for UASs operators seeking broader use of the skies for commercial purposes.

The FAA in early 2013 asked the Radio Technical Commission for Aeronautics (RTCA) to take the lead in developing detect-and-avoid standards for UASs. Founded in 1935, RTCA is a private, not-for-profit association that is a premier venue for developing consensus with aviation on standards for avionics and other systems.

RTCA’s Special Committee 228 is charged with developing what are called minimum operational performance standards (MOPS) for UASs. It went to work on May 20, 2013, taking a phased approach to the subject. RTCA does not expect to publish the final MOPS for Phase 1 until July 2016.

Those MOPS will focus only on detect-and-avoid capabilities for UASs flying directly from the surface to Class A airspace (that is, 18,000 feet mean sea level of higher). Work on detect-and-avoid standards for aircraft flying in unrestricted, Class G airspace and in Class D airspace around smaller and less busy airports will start later.

The Lockheed Martin/Kaman Unmanned K-MAX for the U.S. Marine Corps is an example of a certificate manned aircraft in an unmanned mission.
Photo courtesy of the U.S. Marine Corps/Sgt. Keonaona C. Paulo

The group has been gathering data on what safe operations require and making technical decisions, but the challenge is largely one of “getting subject matter experts to agree,” Paul Schaeffer told the RTCA 2015 Global Aviation Symposium in Washington June 3.

Schaeffer, the U.S. Air Force’s program manager for Air Borne Sense and Avoid and a co-lead of the special committee’s working group on detect and avoid, noted the overall committee includes more than 270 members from the military, FAA, aircraft and avionics manufacturers and other industry participants.

One of the detect-and-avoid working group’s first tasks was to determine what “avoid” meant. Members agreed to adhere to the longstanding FAA air traffic principle that one aircraft should stay “well clear” of other aircraft while maneuvering. But it took a year for them to agree on what “well clear” means from a technical specifications perspective, Schaeffer said.

UAS operators aren’t waiting for those standards before acting. The FAA has received eight applications for full type certificates for unmanned aircraft, including some with rotorcraft designs. Aero Kinetics is one applicant; its design is a rotorcraft. Several applicants already have received Restricted type certificates.

A full type certificate would enable the recipient’s aircraft to be flown throughout U.S. airspace. But those UASs would still have to meet FAA requirements for safe separation from other aircraft.

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