Aircraft Performance Parameters Research Articles

A Comparison of Exhaust Condensation Trail Forecast Algorithms at Low Relative Humidity

Abstract The Schrader and Schumann contrail forecast algorithms and a third algorithm are evaluated under low relative humidity conditions using a dataset of asynoptic atmospheric soundings and 318 coincident ground-based aircraft and contrail observations collected near Dayton, Ohio. Aircraft were positively identified and their flight altitudes were determined using either Federal Aviation Administration flight logs or data collected with the Wright–Patterson Air Force Base air traffic control radar. The sounding data were used with assumed aircraft performance parameters to prepare nowcasts of contrail critical temperatures. The nowcasts were examined subjectively by comparing the distribution of correct and incorrect forecasts as a function of the difference between critical temperature and ambient temperature. Objective evaluation against the contrail observations also was done using several common statistical measures. The third algorithm produced critical temperatures that were systematically too c...

Characterizing the Supercooled Large Droplet Environment with Corresponding Turboprop Aircraft Response

This continuing study evaluated turboprop aircraft performance response to various environmental conditions. These conditions included clear air, warm rain, ice only, mixed phase, and supercooled drops encountered during 19 separate e ights. Supercooled droplets consisting of cloud, drizzle, and rain sizes were the main focus of this study. Aircraft response was quantie ed by rates of change in aircraft rateof-climb capability, lift and drag coefe cients and, lift over drag ratio. The aircraft performance parameters were compared to environmental hydrometeor parameters, such as 80% volumetric diameter (80VD)*liquid water content (LWC), quantifying the environmental conditions. Results show that encounters with supercooled drizzle drops, or ZL, resulted in maximum rates of performance degradation. These high rates of degradation forced the pilot to take evasive action within 5 min of entering these hazardous conditions. The Wyoming King Air experienced substantial increases in drag and stall speed, substantial decreases in climb capability, and signie cant lift degradations while encountering ZL. Encounters with supercooled cloud and rain-sized drops resulted in minor to low rates of performance degradation, whereas encounters with supercooled drops in low ice particle concentrations resulted in only minor rates of degradation. In addition, aircraft response to high ice particle concentrations and low liquid water, following a ZL encounter, resulted in rapid performance recovery, possibly because of erosion of ice on the airframe. Aggregates of needles and hexagonal plates led to the highest rates of recovery, whereas cold, clear air resulted in the lowest rates of recovery. Furthermore, e ight analyses facilitated quantifying ZL horizontal extents and encounter frequencies. For example, ZL measured by a one-dimensional cloud probe during atmospheric research e ights exceeded 0.05 g /m 3 twice per 10 e ight hours over a horizontal length of 29 km. The results presented herein show a strong relationship between aircraft response and environmental parameters utilizing the largest drops in the hydrometeor distribution (80VD*LWC and ZL LWC). The results suggest that the most severe icing is actually caused by drizzle-sized drops as opposed to freezing rain. In addition, the results suggest that activating the de-icing boots (with typical chordwise coverage) after a ZL encounter may have little effect on aircraft performance recovery.

Turboprop Aircraft Performance Response to Various Environmental Conditions

This study evaluated aircraft performance response to various environmental conditions encountered during flight. These conditions included clear air, ice only, mixed phase, and supercooled drops. Supercooled drops consisting of cloud, drizzle and rain sizes were the main focus of this study. Aircraft response was quantified by rates of change in aircraft climb capability, drag coefficient, and lift over drag ratio. The aircraft performance parameters were compared to an environmental hydrometeor parameter quantifying the environmental conditions. Results show that encounters with supercooled drizzle drops, or SCDD, resulted in maximum rates of performance degradation. Encounters with supercooled cloud and rain sized drops resulted in minor to low rates of performance degradation while encounters with supercooled drops in low ice particle concentrations resulted in only minor rates of degradation. In addition, aircraft response to high ice particle concentrations, in low liquid water, following a SCDD encounter resulted in rapid performance recovery. The results presented herein show a strong relationship between aircraft response and an environmental parameter utilizing a weighted volume diameter and liquid water content. The results suggest that the most severe icing is actually caused by SCDD as opposed to freezing rain. (Author)

Flight test certification of multipurpose head-up display for general aviation aircraft

Advances in flight display technology have enabled manufacturers to provide a head-up display (HUD) of aircraft control and performance parameters for use in general aviation aircraft without the use of inertial platforms or specialized data bus architecture. The Federal Aviation Administration currently has no regulatory guidance regarding HUD or flight symbology certification. A specific certification pro- gram is presented. The process of categorizing the HUD as a supplemental system instead of a primary display is discussed. Flight display symbology is discussed, and the final symbology set is presented. The certification flight test plan is discussed including the requirements for functional, usability, and opera- tional testing. Flight test data are discussed. A HUD system was certified for single-pilot use in instrument meteorological conditions in a general aviation aircraft. HE head-up-displ ay (HUD) was first developed in mili- tary aircraft from reflecting optical sights. The HUD places flight and navigation data in the pilot's forward field of view (FOV). These data are presented through various symbols as a collimated image that appears to be floating at infinity. Early HUDs were used for weapons delivery with displays tailored for a single task. HUDs today can provide a variety of aircraft state and navigation data. Recent HUD develop- ment, as an enhancement tool to facilitate manually flown in- strument approaches to weather minima as low as a runway visual range of 1200 ft, has obvious implications for air carrier operations. The ability to ease the instrument-to-visual ap- proach transition and acquire the runway environment sooner is a desirable feature of any cockpit display system. Though these systems usually require high-fidelity inertial reference platforms and are costly, the advantage gained in arrival reli- ability has been deemed cost effective. Additionally, because the pilot has state and navigation data available while looking through the aircraft windscreen, the increased ability to visu- ally clear for other traffic is a safety enhancement. Current HUD development and operational concept are toward dis- plays that are useful and certifiable during all phases of flight. Lower cost displays that do not provide enhanced capability, but do provide increased out-of-the-cockpit awareness for cor- porate and general aviation aircraft are also emerging into the marketplace. A typical HUD displays airspeed, altitude, pitch and roll attitude, and heading. In addition, navigation or mission data can usually be selected for display. Flight director modes, radar altitude, and marker beacon passage can also be shown, if available. Most HUDs can also display master warning and caution annunciators. The subject HUD was targeted for the corporate and general aviation industry. This HUD differed from other operational systems in that it used conventional aircraft gyros and did not depend on an inertial navigation system platform for attitude information. Since conventional aircraft gyros are less precise than inertial platforms, the HUD symbology was not confor-

Horizontal variable-speed interception game solved by forced singular perturbation technique

The time-optimal pursuit-evasion game in the horizontal plane between two airplanes is analyzed by applying the technique of forced singular perturbations (FSPT). Based on the assumption of multiple time scale separation, a zeroth-order closed-form solution is obtained, enabling one to use realistic aerodynamic and propulsion data. Control strategies are approximated by explicit feedback expressions of the state variables and the aircraft performance parameters. The zeroth-order feedback approximation is compared to the optimal openloop solution of the game. This comparison confirms the validity of the FSPT approximation for sufficiently large initial distances of separation.

Investigation of F/A-18A Engine Throttle Usage and Parametric Sensitivities

Projection of realistic engine usage is essential for advanced tactical fighter aircraft to avoid significant durability problems and associated high weapon system costs. Previous engines such as the TF41 and F100 experienced durability deficiencies because actual field usage was more severe than initial projections. Thus, MCAIR developed systematic prediction procedures to provide improved usage estimates for preliminary design. These procedures based on digital flight simulation models were used to investigate throttle usage for peacetime training flights of the Navy F/A-18A aircraft with F404-GE-400 engines. The purpose was to identify major contributors to engine damaging usage and provide an early assessment of anticipated F/A-18A field utilization. Data are presented for individual mission throttle cycles and time histories as well as composite engine duty cycles. The prediction procedures were validated demonstrating excellent agreement by comparing results with flight data from the contractor phase of the Navy’s Accelerated Service Test (AST) at Patuxent River Naval Air Station (NAS). Engine usage was projected for F/A-18A transitional training at Lemoore NAS, the first deployment site. Results indicate that the severity of cycles and hot time at Lemoore will be comparable to that for AST. The ground attack, air combat, and air intercept missions were found to contribute the most to usage. Sensitivities were also evaluated parametrically for F/A-18A aircraft performance and mission parameter variations. Usage was found to be most sensitive to aircraft thrust to weight, and insensitive to store drags. The results provide valuable insight into how missions, maneuvers, and aircraft performance parameters affect usage which is important for cost effective design of durable, high-performance engines.