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In 2021 the Federal Aviation Administration in collaboration with the National Research Council of Canada performed research on altitude ice crystal icing of aircraft engines using the modular compressor rig, ICE-MACR, in an altitude wind tunnel. The aim of the research campaign was to address research needs related to ice crystal icing of aircraft engines outlined in FAA publication Engine Ice Crystal Icing Technology Plan with Research Needs. This paper reports the findings on ice accretion from a configuration of ICE-MACR with two compression stages. Inherent in two-stage operation is not just additional fracturing and heating by the second stage but also higher axial velocity and potentially greater centrifuging of particles. These factors influence the accretion behavior in the test article compared to single stage accretion.

High Ice Water Content (HIWC) has been identified as a primary causal factor in numerous engine events over the past two decades. Previous attempts to develop a remote detection process utilizing modern commercial radars have failed to produce reliable results. This paper discusses the reasons for previous failures and describes a new technique that has shown very encouraging accuracy and range performance without the need for any modifications to industry’s current radar design(s). The performance of this new process was evaluated during the joint NASA/FAA HIWC RADAR II Flight Campaign in August of 2018. Results from that evaluation are discussed, along with the potential for commercial application, and development of minimum operational performance standards for future radar products.

NASA's Deep Space Network (DSN) uses high-power transmitters on its large antennas to communicate with spacecraft of NASA and its partner agencies. The prime reflectors of the DSN antennas are parabolic, at 34m and 70m in diameter. The DSN transmitters radiate Continuous Wave (CW) signals at 20 kW - 500 kW at X-band and S-band frequencies. The combination of antenna reflector size and high frequency results in a very narrow beam with extensive oscillating near-field pattern. Another unique feature of the DSN antennas is that they (and the radiated beam) move mostly at very slow sidereal rate, essentially identical in magnitude and at the opposite direction of Earth rotation.

This paper describes the recently established Commercial Aviation Alternative Fuel Initiative (CAAFI), including its goals and objectives, as well as presents an alternate fuel roadmap that was originally generated by industry and refined by the CAAFI stakeholders. CAAFI is designed to coordinate the development and commercialization of “drop-in” alternate fuels (i.e. fuels that can directly supplement or replace crude oil derived jet fuels), as well as exploring the long-term potential of other fuel options. The ultimate goal is to ensure an affordable and stable supply of environmentally progressive aviation fuels that will enable continued growth of commercial aviation. This initiative is organized into four sub-groups: Research and Development (R&D), certification, environment, and economics & business. The R&D group seeks to identify promising new drop-in alternate fuels, and to foster coordination of development efforts.

Many of the certification regulations in 14 CFR Part 25 are by design, broad and as such, can be subject to large differences in the interpretation of what constitutes adequate compliance. Advisory Circulars (AC's) were developed for many of the regulations to assist industry, as well as certification personnel, with what is considered an acceptable, but not the only means, of compliance. However, there are many regulations where no advisory material is available. In these cases, the “acceptable means” of compliance can vary to a greater degree among the various aircraft certification offices. This difficulty is aggravated as new applicants and regulatory personnel enter the certification field. Recent discussions and interpretations on the usage of an avionic unit's mean time between failure or MTBF for its detectable faults as the basic repair rate for undetected or latent faults, is a subject area where no significant advisory material exists.

Weather is a major cause of aircraft accidents and incidents and the single largest contributor to air traffic system delays. Through improvements in the knowledge of current weather conditions and reliable forecasts, the Federal Aviation Administration (FAA) can improve aviation safety, increase system capacity, and enhance flight planning and fuel efficiency. The FAA has established an Aviation Weather Research (AWR) program to address specific requirements for weather support to aviation by providing the capability to generate more accurate and accessible weather observations, warnings, and forecasts and also by increasing the scientific understanding of atmospheric processes that spawn aviation weather hazards. The goal of AWR is to provide meteorological research that leads to the satisfaction of specific aviation weather requirements.

“As we handle more operations and passengers in the air, we must make certain we have the capacity to handle increased traffic on the ground.” - Jane Garvey, FAA Administrator (4/20/98) The FAA Technical Center (Aviation System Analysis and Modeling Branch, ACT-520) has been responsive to the FAA Airport Capacity Program customers for the past 22 years, developing, testing, and applying airfield and airspace simulation models. More than 90 capacity studies have been completed with ACT-520 personnel contributing their technical expertise to the Airport Design Teams. The teams are comprised of FAA personnel, airport operators, air carriers, other airport users and aviation industry representatives at major airports throughout the US. Initial studies focused on modeling airport operations from final approach, taxi, gate operations and departure processing. Later in the program, local airspace studies were included in some airport study efforts.

Recent changes in DoD procurement directives have encouraged the purchase of civilian products for use in certain military applications. One such application is the upgrade of avionics suites with the Global Positioning System (GPS) in military air transport aircraft to meet joint civil-military operational requirements. This paper reviews the Commercial Off-the-Shelf (COTS) concept and the proper use of TSOs, ACs, and FARs in both the design and integration process.

Numerical simulations indicate that blast loading on aircraft structural joints can impart loading rates in excess of 10 Mlb/sec (ten million pounds per second, Reference 1). Experimental evidence, on the other hand, suggests that mechanical joint failure loads are highly loading rate dependent; for example, the failure load for a dynamically loaded tension joint can double from its static value. This paper discusses the progress and to-date findings of research on the assessment of strength failure of aircraft structural joints subjected to loading rates expected from an internal explosive detonation, and several associated experimental procedures to generate such dynamic loading. This work is conducted at MDC and at the University of Dayton Research Institute (UDRI) in support of the FAA Aircraft Hardening Program.

Voice communications are crucial to safe and efficient air traffic operations. Controllers are required to use standard phraseology, and pilots are encouraged to use it when talking to controllers. Incomplete or inaccurate communications were implicated in mishaps such as the Tenerife accident. This research examined the frequency of phraseology deviations in a sample of 5,000 transmissions from 3 terminal facilities. The Aviation Topics-Speech Acts Taxonomy (ATSAT) was used to develop baseline data and analyze controller/pilot communications. Clearance instructions were transmitted most frequently and they contained a higher percentage of deviations from standard phraseology than any other speech act category. Identification of the types of errors typically associated with specific miscommunications could result in implementing new training approaches that ensure a higher compliance with standard procedures and improve standard phraseology usage.

Microprocessor technology is allowing functions in aircraft to be implemented to a greater degree by digital process control than by conventional mechanical or electromechanical means. A review of this technology indicates a need for updated certification criteria. A high level of commitment to the technology such as fly-by-wire is completely beyond the scope of existing certification criteria. This paper emphasizes the areas of software validation levels, increased concern with basic power system qualification, and increased environmental concerns for electromagnetic interference and lightning.

Average continuous flow rates for each type of aircraft exit were examined in 89 full-scale evacuation demonstrations. Passengers tend to form continuous lines at available exits when evacuating an airplane. The study concludes that, with rare exception, the passenger rates of egress from the same type exit on different make and model airplanes are not significantly different. Passenger cabin configuration, seat pitch, and aisle width have no significant bearing on the egress rates provided the aircraft certification requirements for minimum aisle width and exit accessibility are met. Injuries resulting from actual emergency evacuations and evacuation demonstrations are also examined.

The advent of digital electronics for use in civil aircraft, particularly the new technology represented by central processor and microprocessor controlled systems, represents a major challenge to the aviation industry. The Federal Aviation Administration (FAA) is charged with the responsibility of evaluating these systems to determine if they can be used safely. The complexity of these systems as compared to their analog counterparts in use today makes their evaluation difficult. This paper outlines the major concerns of the FAA with the use of software controlled digital systems for airborne applications. The methods which can be used by members of the aviation industry to obtain FAA certification of these systems are also discussed. The proposal of Special Committee SC-145 of the Radio Technical Commission for Aeronautics (RTCA) form the basis of the design methodology which is described for the successful development of the computer programs (software) to be used by these systems.

In view of the fact that future generations of derivative or new aircraft will be faced with problems of increasing operating efficiency, new and more advanced technology will have to be introduced. To this end, the Federal Aviation Administration has been examining the certification question and has concluded that simulation may be increasingly important in the future certification activities. Through a contract with Lockheed Aircraft Company, the FAA will be able to review past use of industrial simulation in connection with certification.

Many problems exist in meeting the future surveillance and communication needs of air traffic control. Many functions and services are now being developed for eventual implementation beginning after 1977. The operation, role, and impact of the Discrete Address Beacon System in meeting these needs and functions are discussed in this paper.

The need to improve the efficiency and capacity of the Air Traffic Control and Navigation System has placed greater emphasis on the functional integration of subsystems which have been treated independently in the past. This paper presents results of limited test programs designed to explore the relationship of terminal area navigation and the air traffic control system, and to show the benefits of an optimum combination of both functions. The need for further analysis is indicated with respect to carrying out the third generation system design postulated by the DOT Air Traffic Control Advisory Committee. It is concluded that functional integration of ATC and navigation in the terminal area presents the greatest challenge. In other areas, such as enroute, the availability of new, integrated avionics systems provides an expanded operational capability.

Area navigation offers a means of establishing an air route system without the constraints entailed in flying toward or away from the signal source. In terminal areas, an area navigation system of routes, combined with ATC computer-aided sequencing and airborne collision-avoidance technology, offers possibilities for establishing future methods of moving high volumes of traffic on and off a complex of multiple parallel runways. Such a system would reduce air-ground communications and controller workloads which are serious limiting factors in today's system. In the en route system, the use of area navigation will result in more efficient utilization of airspace, although regimentation of traffic will continue to be necessary in areas of high traffic density. An area navigation system, based on VOR/DME inputs is possible in the near future.