PREPARED STATEMENT OF GEORGE W. CHERRY, DIRECTOR OF AERONAUTICAL OPERATING SYSTEMS, OFFICE OF ADVANCED RESEARCH AND TECHNOLOGY, NATIONAL AERONAUTICS AND SPACE ADMIN

ISTRATION

INTRODUCTION

Mr. Chairman and Members of the Committee, in order to introduce the mission and programs of the Aeronautical Operating Systems Division, I would like to quote from "Issues and Directions for Aeronautical Research and Development", which you will recognize as a report of your subcommittee on Advanced Research and Technology.

"The most severe future limitations on commercial aircraft utilization in the United States have to do with operating problems-factors such as traffic control, airport facilities, and noise."

This is the opinion of the Corporate Vice President for Engineering and Research of the McDonnell Douglas Corporation, but it's an opinion echoed again and again by members of the air transportation industry and disinterested, knowledgeable observers. For example, quoted in the same report is this statement of Dr. H. Guyford Stever, President of Carnegie-Mellon University and member the Aeronautics and Space Engineering Board of the National Academy of Engineering.

"In the past, aviation research and development has been concerned primarily with improving the flight vehicle. But the flight vehicle is only one segment of the total air transportation system. In setting research and development objectives it is necessary to seek goals that improve the productivity of the total sysem-not just the flight vehicle." The conclusions of the joint DOT-NASA Civil Aviation Research and Development Policy Study concur with these viewpoints and cite noise, congestion of airways and airports, and the problems of lowdensity, short-haul air transportation as the most critical civil areas requiring research and development. "Issues and Directions for Aeronautical Research and Development" states that the stakes are high in finding a solution to our critical aeronautical operating problems: "On the one hand, continuing profitable operations, indeed survival, of a number of industries are deeply involved-for example, airlines and aerospace manufacturers. On the Government side, national security and economic well being are involved."

We are continuing existing programs and starting vigorous new ones which attack these problems. I would like to emphasize that these are authentic system research and development problems. Certainly the vehicles are pivotal elements, but these problems arise from the relationship of the basic flight vehicle and its systems to the operating environment-to the airport, to other aircraft, to the airways, to the traveller, to the pilot, and to the non-travelling public. Thus these are not aeronautical vehicle problems alone, nor air traffic control problems alone, nor airport problems alone, nor piloting problems alone. And the penalties for failure to solve the problems and the rewards for success lie in the socio-economic realm. Therefore, the total system approach to these problems must be taken, and the technical and operational goals and plans must be related to the social and economic benefits.

The problem of first priority is noise; aircraft noise in the terminal areas and in the vicinity of airports is making air transportation anathema to the communities ringing the airports. The fact is, because of noise, building of new, conveniently located, urban airports or the full utilization and expansion of existing ones is practically politically impossible. Thus, the growth of a transportation mode which has contributed so much to the economic vitality of our nation and the mobility of its citizenry is partially inhibited. And air transportation, which is so frugal of the use of our land, is being begrudged or denied the use of the necessary land for its flight origins and terminations. The affected airport neighbors in the meanwhile seek partial relief through the courts by fighting for curfews or flight path restrictions beyond those already conceded; and state legislators with airport communities in their constituency plan laws to limit airport expansion or restrict airport operations.

The NASA programs for aircraft noise abatement fall into the areas of hardware research and technology, life sciences research, and operating systems research and technology. The harware programs such as the NASA quiet engine program and the quiet STOL experimental vehicle program, and the life sciences program for determining the characteristics of noise which make it annoying to the human being, are described in other OART statements.

In the operating systems area, OART has already conducted a research and flight test program to demonstrate that the noise impinging on the airports environs from a landing aircraft can be reduced by steepening the flight path. The experimental steep flight path reduces the noise in a twofold way.

1. The aircraft engines are operated at a lower thrust setting on the steeper flight path.

2. The aircraft is higher above the community over which it is flying. Figure 1 illustrates the noise abatement effect due to the latter principle alone when the flight path is steepened from the conventional three degrees. While six degree flight paths are no aerobatic stunt and give considerable noise reduction (the NASA CV-990, a four-engine jet transport, has been flown on nearly twenty degree approach paths!), the operating problems must be carefully examined. Therefore, we are initiating a contract in this fiscal year with an airline to conduct a flight program using conventional civil airliners piloted by airline pilots to determine whether vertical area navigation and a flight path display can be used to permit safe operation of civil airliners on noise-abating, steep flight paths. The data will be used for NASA research in avionics, flight control systems, instrument landing systems, displays, aircraft design, and operational procedures. The goal of the research is to make noise-abating flight paths the standard, normal all-weather method of approaching and departing the airport. In the short term, we want to find out whether we can propose an inexpensive aircraft retrofit, pilot training program, and operating procedure which would permit earlier employment of noise-abating, steep flight paths.

NOISE CONTOURS AS A FUNCTION OF FLIGHT PATH ANGLE
(ASSUME CONSTANT THRUST AND OMNIDIRECTIONAL SOUND SOURCE)

There are other operational techniques for reducing the noise impinging on a community from an aircraft approaching or departing an airport. In Washington, we are familiar with the procedure which the aircraft follow of trying to fly over the Potomac River on their approach to Washington National Airport. This curved ground track reduces the aircraft noise which impinges on the communities of the greater Washington, D.C. area. Curved ground-track approaches are common noise-abating procedures at many of our urban airports. These noiseabating approach paths would be more widely used if our instrument landing systems were compatible with curved ground tracks. During low-visibility weather, for example, the pilot cannot see the ground to fly the curved path. A national plan is being developed by FAA, DOD, and NASA to develop, test, produce, and install a new instrument landing system. This new landing system, based on the scanning-beam microwave principle, would permit precision allweather curved ground tracks. The new landing system would also provide guidance for precision, safe, steep flight paths. Thus, the new landing system should contribute substantially to aircraft noise abatement.

The NASA, in cooperation with DOT and FAA, is undertaking validation of the new landing system for STOL aircraft. More will be said about this joint program. Much of the work that will be undertaken to validate the new landing system for STOL will be applicable to conventional takeoff and landing (CTOL) vehicles also. The new scanning-beam ILS has other advantages. It will permit safer approaches and landings and better runway utilization for our crowded urban airports.

The problem of second priority is congestion of our airways and airports. Congestion, especially in the terminal areas, increases the aircraft "block_time."* "Holding" in the air, "slow flying," waiting on the taxiways, and waiting on an aircraft gate are unproductive consumption of the aircraft, crew, and passenger's time. In our crowded air corridors which originate from and terminate at busy hub airports, block times sometimes approach twice the time the flight vehicles are capable of yielding. These inefficient block times drive operating costs up and decrease traveller convenience. Figure 2 is a plot of direct operating costs in cents per available seat mile versus stage length for jet short-haul trips with and without a large delay. These curves tell the story of why high-density shorthaul air transportation is frequently unprofitable. Much of this flight delay occurs in the terminal areas and airports because of inefficient air traffic control, inadequate surveillance, navigation, guidance and communication, and less-thanoptimum runway, taxiway, and gate design. The aircraft must not be entirely acquitted of blame. While the aircraft are capable of shorter block times in some sort of idealized air traffic control and airport environment, the fact of the matter is, the aircraft and their associated airborne systems are not configured to land in very bad weather, fly noise-abating paths, or land on short or closely spaced parallel runways. The congestion and delays have become so intolerable at some airports that the FAA has instituted a quota system to limit the number of landings and departures scheduled in any hour. This changes the traveller's problem from the prospect of a possibly long delay to the prospect of not being able to book a flight when he wants it. Obviously, these are extremely complex aeronautical operating system problems. Otherwise the FAA would not have resorted to limiting natural peak hour traffic.

The block time is only part of the story for the typical traveller whose origin and destination are not a pair of airports but rather two other places linked at each end to the airport by some mode of ground transportation. Ideally the traveller wants a short block time and short trips to and from the airports. This would mean in many cases locating airports nearer urban centers. The noise problem and the problems I have just discussed are formidable obstacles to creating this ideal situation.

There are solutions to these problems of congestion, delays, quotas, and inhibited air traffic growth; and NASA is doing its part and hopes to do more by providing some of the required research and technology. For example, one way in which operating systems research and technology can yield striking benefits is illustrated in Figure 3, a plot of runway landing capacity versus longitudinal guidance error for both STOL and CTOL traffic. The runway landing capacity, i.e., the number of airplanes which can be landed per hour, is directly related to how many aircraft can be accommodated without excessive delay.

"Block time" from the passenger's viewpoint can be defined as the time between his boarding the aircraft at his air trip origin and his deplaning at his air trip destination.