Although the ability to measure vertical eddy fluxes of gases from aircraft platforms represents an important capability to obtain spatially resolved data, accurate and reliable determination of the turbulent vertical velocity presents a great challenge. A nine-hole hemispherical probe known as the “Best Air Turbulence Probe” (often abbreviated as the “BAT Probe”) is frequently used in aircraft-based flux studies to sense the airflow angles and velocity relative to the aircraft. Instruments such as inertial navigation and global positioning systems allow the measured airflow to be converted into the three-dimensional wind velocity relative to the earth’s surface by taking into account the aircraft’s velocity and orientation. Calibration of the aircraft system has previously been performed primarily through in-flight experiments, where calibration coefficients were determined by performing various flight maneuvers. However, a rigorous test of the BAT Probe in a wind tunnel has not been previously undertaken. The authors summarize the results of a complement of low-speed wind tunnel tests and in-flight calibrations for the aircraft–BAT Probe combination. Two key factors are addressed in this paper: The first is the correction of systematic error arising from airflow measurements with a noncalibrated BAT Probe. The second is the instrumental precision in measuring the vertical component of wind from the integrated aircraft-based wind measurement system. The wind tunnel calibration allows one to ascertain the extent to which the BAT Probe airflow measurements depart from a commonly used theoretical potential flow model and to correct for systematic errors that would be present if only the potential flow model were used. The precision in the determined vertical winds was estimated by propagating the precision of the BAT Probe data (determined from the wind tunnel study) and the inertial measurement precision (determined from in-flight tests). The precision of the vertical wind measurement for spatial scales larger than approximately 2 m is independent of aircraft flight speed over the range of airspeeds studied, and the 1σ precision is approximately 0.03 m s−1.

Aircraft-based vertical flux measurements fill a gap in the spatial domain for studies of biosphere-atmosphere exchange. To acquire valid flux data, a determination of the deviation from the mean vertical wind, w , is essential. When using aircraft platforms, flux measurements are subject to systematic and random errors from airflow distortion caused by the lift-induced upwash ahead of the aircraft. Although upwash is typically considered to be a constant quantity over periods used for calculating fluxes, it can vary significantly over short (and longer) periods due to changes in aircraft lift. The characterization of such variations in upwash are of undeniable importance to flux measurements, especially when real-time computations of w are required. In this paper, the variability in upwash was compared to the calculated upwash from the model of Crawford et al. (Boundary-Layer Meteorol, 80:79-94, 1996) using data taken during a long-period (phugoid mode) free oscillation of the aircraft. The cyclic variation of lift during the free oscillation offers an ideal scenario in which to acquire in-flight data on the upwash that is present, as well as to test the capability of upwash correction models. Our results indicate that while this model corrects for much of the mean upwash, there can be significant variations in upwash on a time scale that is important to flux measurements. Our results suggest that use of the measured load factor could be an easily implemented operational constraint to minimize uncertainty in w due to changing upwash from changing aircraft lift. We estimate, using the phugoid data, and from variations 123 462 K. E. Garman et al. in aircraft attitude and airspeed in flux-measurement configuration, that the uncertainty in w caused by variable upwash is approximately ±0.05 m s −1 .

This paper describes a human factors (HF) study of Unmanned Aircraft System (UAS)accidents. This study is significant because it contributes to understanding the complex human-machine environment. This study utilized the Human Factors Analysis and Classification System (HFACS) to classify the kinds of human factors errors involved in a particular subset of UAS accidents. The study researcher presented four UAS accident reports to a group of diversely experienced pilots. Each of these four accidents involved the same make and similar models of UAS. These UAS models are acutely prone to humanmachine interactive failures because their designs are distinctly different than are normally present in human-occupied aircraft. The researcher then subjected the HFACS analyses results to a safety risk analysis involving several qualitative analytical methods. The study results showed that 8 of the 19 (42%) HFACS categories overwhelmingly contributed to 77% of the total risk in the aggregate of the four UAS accidents under study, while another 6 of the 19 (32%) HFACS categories contributed to less than 5% of the total risk.

With the resurgence of the general aviation market, there is a growing need to acquire flight test data on light aircraft and to educate engineers on the methods used to test such aircraft. Data acquisition for such operations has often been performed by manually recording instrument readings from the aircraft's instrument panel. Until recently, electronic data acquisition was not realistic for flight testing light aircraft, because the instruments' weight and bulk could significantly alter the performance and handling characteristics of the aircraft.This paper describes the development and testing of portable, computer-aided electronic instrumentation. This instrumentation can be used to acquire flight test data on a variety of light aircraft in a cost effective manner with simple installation procedures. Multidisciplinary coordination was necessary between system engineers, mechanics and pilots to ensure that the system was legal for installation and useful during flight. An instrumented light aircraft can be used to educate engineering students and professionals in flight testing procedures without altering the aircraft used. Airspeed calibration and long-period mode (phugoid) experiments were performed to demonstrate the usefulness of such instrumentation. _______________________________________

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