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Technical Paper

“Fuel Flow Method2” for Estimating Aircraft Emissions

In recent years there has been increasing interest in quantifying the emissions from aircraft in order to generate inventories of emissions for climate models, technology and scenario studies, and inventories of emissions for airline fleets typically presented in environmental reports. The preferred method for calculating aircraft engine emissions of NOx, HC, and CO is the proprietary “P3T3” method. This method relies on proprietary airplane and engine performance models along with proprietary engine emissions characterizations. In response and in order to provide a transparent method for calculating aircraft engine emissions non proprietary fuel flow based methods 1,2,3 have been developed. This paper presents derivation, updates, and clarifications of the fuel flow method methodology known as “Fuel Flow Method 2”.
Technical Paper

some thoughts on optimum combinations of Wings and Vertical Thrust Generators in VTOL Aircraft

THIS PAPER reviews VTOL problems, indicating probable ways toward optimization of whole lifting and propelling system. Also discussed are the power and thrust requirements for optimum cruise and vertical take-offs and landings for propeller-driven and jet-propelled aircraft. Three speed ranges offer the most promise for VTOL aircraft, if thrust requirements for cruise and take-off are to match. The ranges are centered around Mach numbers of 0.65, 0.8, and 2.0+. There is a possibility of overcoming the high thrust needed for hovering by use of bypass augmentation, special hovering jets, or favorable ground effects, the author reports.
Technical Paper

selection of Optimum Modes of Control for aircraft engines

THE optimum mode of control for an aircraft engine is dependent on both the configuration of the engine and its application. Each engine application requires several detail modes of control, one for each definable regime of operation of the engine. Discussions of control requirements can be simplified by classifying these regimes by objectives: physical limiting, thrust, and transient control. The turbojet engine is the basis for the discussion in this paper. Acceptable modes of control can often be selected by inspection of the engine and its application. Selection of an “optimum” control mode requires investigation of the operation of the engine and weapons system at every stage of its use. The selection of a “mode” of control requires a compromise between performance and other design factors. The need for simplicity and accuracy must be balanced against the stability requirements. The availability and flexibility of control components may limit the modes of control considered.
Technical Paper


THIS PAPER presents the development of the DC-8 suppressor and thrust brake unit from initial test work through the final design. The selection of the production unit was based on a wide background of test work using both model and full-scale facilities. On the basis of this work, the configuration selected for production consisted of a fixed, corrugated, suppressing nozzle with a retractable ejector. A target-type thrust brake, mounted in the ejector, was chosen for the thrust brake production unit. Approximately 12-db suppression and 44% reverse thrust are provided by the unit. The ejector is hydraulically operated and the thrust brake air actuated. Both actuation systems obtain power from the aircraft systems which provides for operation during engine-out conditions. Alternate methods of actuation are provided in case of a primary system failure.
Technical Paper

Yaw Effects on the Narrowband Spectra Above a Delta Wing in Turbulent Flow

Combat aircraft maneuvering at high angles of attack or in landing approach are likely to encounter conditions where the flow over the swept wings is yawed. This paper examines the effect of yaw on the spectra of turbulence above and aft of the wing, in the region where fins and control surfaces are located. Prior work has shown the occurrence of narrowband velocity fluctuations in this region for most combat aircraft models, including those with twin fins. Fin vibration and damage has been traced to excitation by such narrowband fluctuations. The narrowband fluctuations themselves have been traced to the wing surface. The issue in this paper is the effect of yaw on these fluctuations, as well as on the aerodynamic loads on a wing, without including the perturbations due to the airframe.
Technical Paper


MBB and Rockwell, under DARPA/NAVAIR and GMOD contract, are currently designing an experimental aircraft which will be dedicated to demonstrate “enhanced fighter maneuverability” (EFM) and supermaneuverability in particular. The aircraft is designed to break one of the last barriers left in aviation, the stall barrier. It will be able to perform tactical maneuvers up to 70° angle of attack and thus achieve very small radii of turn. Such highly instantaneous 3-dimensional maneuvers are of significant tactical value in future air combat with all aspect weapons. Key to the penetration into this unexplored flight regime is thrust vectoring in pitch and yaw. This feature is also used to enhance agility in critical flight conditions and to enhance the decoupling of fuselage aiming and flight path control as required for head-on gun firing.
Technical Paper

X-31 Helmet Mounted Visual & Aural Display (HMVAD) System

Agile aircraft (X-29, X-31, F-18 High Alpha Research Vehicle, & F-16 Multi-Axis Thrust Vector) test pilots, while flying at high angles of attack, experience difficulty predicting their flight path trajectory. To compensate for the loss of this critical element of situational awareness, the X-31 International Test Organization (ITO) installed and evaluated a helmet mounted display (HMD) system into an X-31 aircraft and simulator. Also investigated for incorporation within the HMD system and flight evaluation was another candidate technology for improving situational awareness - three dimensional (3D) audio. This was the first flight test evaluating the coupling of visual and audio cueing for aircrew aiding. The focus of the endeavor, which implemented two visual and audio formats, was to examine the extent visual and audio orientation cueing enhanced situational awareness and improved pilot performance during tactical flying.
Technical Paper

World's First VTOL Airplane Convair/Navy XFY-1 Pogo

The Convair/Navy XFY-1 VTOL fighter was ahead of its time. In the early 1950s it became the first airplane to take off vertically, hover, transition to high speed level flight, transition back to hover, and land vertically. Pilot “Skeets” Coleman made a number of successful flights at Moffett Field South of San Francisco, at Brown Field near the California/Mexican border, and at San Diego's Lindbergh Field. This “first of a kind” aircraft soon adopted the name “POGO”. The POGO with its stall proof delta wing had near perfect aerodynamic characteristics in hover, transition and level flight. There were no “black boxes” needed for stability augmentation. The POGO was one of the very first aircraft to use hydraulic power flight controls - a system used today on all modern fighter and transport aircraft.
Technical Paper

Wing Modification for Increased Spin Resistance

A simple wing leading-edge modification has been developed that delays outer wing panel stall, thus maintaining roll damping to higher angles of attack and delaying the onset of autorotation. The stall angle of attack of the outer wing panel has been shown to be a function of the spanwise length of the leading-edge modification. The margin of spin resistance provided by the modification is being explored through flight tests. Preliminary results have been used to evaluate spin resistance in terms of the difference in angle of attack between outer wing panel stall and the maxiumum attainable angle of attack.
Technical Paper

Wind-Tunnel Measurements of Wing-Canard Interference and a Comparison with Various Theories

CANARD-CONFIGURED AIRCRAFT DESIGNS have played a historic role in aeronautical research. However, only in the past decade or two has a canard been incorporated into a significant number of aircraft designs. Powered flight began with the Wright Flyer, which was a canard-configured aircraft. Unfortunately, however, that aircraft was longitudinally unstable and the misconception arose that all canard aircraft would be unstable in pitch, irrespective of the placement of the center of gravity. In the early years of aircraft development, the canard concept was dropped in favor of conventional tailaft designs. It was not until the 1960s that canards were again seriously considered for several high-speed, designs. For example, in the United States’ supersonic transport program, a canard was initially considered; because of several problems with aerodynamic interference, however, the idea was abandoned.
Technical Paper

Wind-Tunnel Investigation of the Low-Speed Aerodynamics of Slender Accelerator-Type Configurations

An investigation was conducted in the Langley 14- by 22-Foot Subsonic Tunnel to determine the low-speed aerodynamic characteristics of a generic, hypersonic accelerator-type configuration. The model consisted of a delta wing configuration incorporating a conical forebody, a simulated wrap-around engine package, and a truncated conical aftbody. Six-component force and moment data were obtained over a range of angle of attack from -4° to 30° and for a sideslip range of ±20°. In addition to tests of the basic configuration, component build-up tests were conducted; and the effects of power, forebody nose geometry, a canard surface, fuselage strakes, and lower surface engines alone were also determined. Control power was investigated via the testing of wing flap deflections as well as the deflections of an aftbody flap in the exhaust flow. Surface pressure data were obtained at several longitudinal locations along the conical forebody.
Technical Paper

Wind Tunnel Testing of an Advanced Flying Automobile Concept

A 1:12 scale model based on the Sokol A350 Advanced Flying Automobile Concept was examined in the San Diego State University Low Speed Wind Tunnel for performance and stability characteristics. Observation showed that the model stalled at angles of attack above 12 degrees, corresponding to a maximum coefficient of lift of 1.54 and a drag coefficient of .284 for the wing center position. Analysis of the moments revealed that the test model was unstable with the current design specifications, however varying the wing location provided additional insight on the stability of the model. With design changes based on moving the center of gravity forward, the prototype vehicle is capable of creating enough lift to fly safely.
Technical Paper

Wind Tunnel Investigations of a High Speed Stowed Rotor Aircraft

Model rotor tests were conducted to investigate aeroelastic and aerodynamic behavior of a stowed rotor aircraft during stopping and stowing of the rotor. Results at various tunnel speeds, using rotors of varying stiffness, indicated the lower limits of blade stiffness necessary to provide adequate airframe clearance and manageable hub moments during conversion. The effects of blade pitch control during conversion were evaluated, and the control values required to minimize stress and moments were established. Various rotor stopping positions were examined and improved aircraft stability and drag were shown to result from initiating blade fold with one blade stopped over the nose. An oscillatory response phenomenon encountered during blade fold was thoroughly explored, and means to prevent the oscillation were successfully tested. The tests gave further evidence that the stowed rotor concept is feasible, but showed that stiff blades may be required for successful conversion in rough air.
Technical Paper

Wind Tunnel Investigation of an Improved Upper Surface Blown-Flap Transport Semi-Span Model

The ASUKA was based upon the airframe of the home produced C-1 tactical transport which was modified into an Upper Surface Blowing (USB) powered high lift STOL aircraft. But the wing configuration was not changed. Therefore, this Experimental Aircraft doesn't always have the optimum configuration of a USB type aircraft. This paper describes the investigations which have been conducted to improve the aerodynamic characteristics of a subsonic jet transport semi-span model with an Upper Surface Blowing Flap system which has been newly designed using the NAL STOL-CAD program. The tests were conducted in the NAL 2- by 2-meter Gust Wind Tunnel and results were obtained for several flap and slat deflections at engine thrust coefficients from 0 to 1.85. As compared with the aerodynamic characteristics of the ASUKA model, we obtained the possibility of reduction of the airframe weight and significant improvement of the aerodynamic characteristics.

Wheel Roll on Rim Criteria for Aircraft Application

This Aerospace Recommended Practice (ARP) is to provide a recommended minimum laboratory roll performance for main landing gear aircraft wheel without tire. This document sets forth minimum roll performance capability for main landing gear wheel to be rolled without tire. The recommended test requirements establish a laboratory demonstration level to equate satisfactory experience on aircraft.