Tentative civil airworthiness flight criteria for powered-lift transports

Representatives of the U.S., British, French, and Canadian airworthiness authorities participated in a NASA/FAA program to formulate tentative civil airworthiness flight criteria for powered-lift transports. The ultimate limits of the flight envelope are defined by boundaries in the airspeed/path-angle plane. Angle of attack and airspeed margins applied to these ultimate limits provide protection against both atmospheric disturbances and disturbances resulting from pilot actions or system variability, but do not ensure maneuvering capability directly, as the 30% speed margin does for conventional transports. Separate criteria provide for direct demonstration of adequate capability for approach path control, flare and landing, and for go-around. Demonstration maneuvers are proposed, and appropriate abuses and failures are suggested. Taken together, these criteria should permit selection of appropriate operating points within the flight envelopes for the approach, landing, and go-around flight phases which are likely to be most critical for powered-lift aircraft

Factors affecting handling qualities of a lift-fan aircraft during steep terminal area approaches

The XV-5B lift-fan aircraft was used to explore the factors affecting handling qualities in the terminal area. A 10 deg ILS approach task was selected to explore these problems. Interception of the glide slope at 457.2 m, glide slope tracking, deceleration along the glide slope to a spot hover were considered. Variations in airplane deck angle, deceleration schedule, and powered-lift management were studied. The overall descent performance envelope was identified on the basis of fan stall, maximum comfortable descent rate, and controllability restrictions. The collective-lift stick provided precise glide slope tracking capability. The pilot preferred a deck-parallel attitude for which he used powered lift to control glide slope and pitch attitude to keep the angle of attack near zero. Workload was reduced when the deceleration schedule was delayed until the aircraft was well established on the glide slope, since thrust vector changes induced flight path disturbances

The effects of recreational footpaths on terrestrial invertebrate communities in a UK ancient woodland: a case study from Blean Woods, Kent, UK

Globally, terrestrial invertebrates are in decline, in part due to habitat fragmentation. Footpaths provide nature-based recreation to the public but can present small-scale spatially continuous changes in forest dynamics. However, their effects on terrestrial invertebrate communities are unknown. Pitfall trapping was undertaken to identify whether terrestrial invertebrate communities were disrupted by a popular recreational footpath in Blean Woods, an ancient UK woodland. The study identified 720 invertebrates across 36 taxa from 20 footpath edge and forest interior traps. It was found that footpaths did not significantly affect terrestrial invertebrate communities. There was no difference in the taxonomic abundance, richness, and diversity; invertebrate trait abundance and richness; or invertebrate community composition between the footpath edge and woodland interior traps. Thus, footpaths in Blean Woods do not disturb the terrestrial invertebrate community, and therefore present a sustainable mechanism for facilitating public engagement with conservation in a nationally important protected ancient woodland

From Monterey to Galway: Evolution of the Oceans in National Income Accounts

This paper provides an introduction and overview of selected papers from the 5th International Symposium on the Oceans in National Income Accounts organized by the Socio-Economics Marine Research Unit at the National University of Ireland Galway in March 2021. Eleven papers drawn from the symposium are included in this volume. The papers cover the current status of defining the ocean economy within national accounts, the expansion of ocean accounting to include environmental economic values, and methodological tools to assist the integration

The Evolving Accretion Disc in the Black Hole X-ray Transient XTE J1859+226

We present HST, RXTE, and UKIRT observations of the broad band spectra of the black hole X-ray transient XTE J1859+226 during the decline from its 1999-2000 outburst. Our UV spectra define the 2175A interstellar absorption feature very well and based on its strength we estimate E(B-V)=0.58+/-0.12. Hence we deredden our spectra and follow the evolution of the spectral energy distribution on the decline from outburst. We find that the UV and optical data, and the X-ray thermal component when detectable, can be fit with a simple blackbody model of an accretion disc heated by internal viscosity and X-ray irradiation, and extending to close to the last stable orbit around the black hole, although the actual inner radius cannot be well constrained. During the decline we see the disc apparently evolving from a model with the edge dominated by irradiative heating towards one where viscous heating is dominant everywhere. The outer disc radius also appears to decrease during the decline; we interpret this as evidence of a cooling wave moving inwards and discuss its implications for the disc instability model. Based on the normalisation of our spectral fits we estimate a likely distance range of 4.6-8.0kpc, although a value outside of this range cannot securely be ruled out.Comment: 10 pages including figures. Accepted for publication in MNRA

The X-ray transient XTE J1118+480: Multiwavelength observations of a low-state mini-outburst

We present multiwavelength observations of the newly discovered X-ray transient XTE J1118+480 obtained in the rising phase of the 2000 April outburst. This source is located at unusually high Galactic latitude and in a very low absorption line of sight. This made the first EUVE spectroscopy of an X-ray transient outburst possible. Together with our HST, RXTE, and UKIRT data this gives unprecedented spectral coverage. We find the source in the low hard state. The flat IR-UV spectrum appears to be a combination of optically thick disk emission and flat spectrum emission, possibly synchrotron, while at higher energies, including EUV, a typical low hard state power-law is seen. EUVE observations reveal no periodic modulation, suggesting an inclination low enough that no obscuration by the disk rim occurs. We discuss the nature of the source and this outburst and conclude that it may be more akin to mini-outbursts seen in GRO J0422+32 than to a normal X-ray transient outburst.Comment: 4 pages, 3 figures, replaced with accepted version. Uses emulateapj5.st

On the Optical -- X-ray correlation from outburst to quiescence in Low Mass X-ray Binaries: the representative cases of V404 Cyg and Cen X-4

Low mass X-ray binaries (LMXBs) show evidence of a global correlation of debated origin between X-ray and optical luminosity. We study for the first time this correlation in two transient LMXBs, the black hole V404 Cyg and the neutron star Cen X-4, over 6 orders of magnitude in X-ray luminosity, from outburst to quiescence. After subtracting the contribution from the companion star, the Cen X-4 data can be described by a single power law correlation of the form $L_{opt}\propto\,L_{X}^{0.44}$, consistent with disk reprocessing. We find a similar correlation slope for V404 Cyg in quiescence (0.46) and a steeper one (0.56) in the outburst hard state of 1989. However, V404 Cyg is about $160-280$ times optically brighter, at a given $3-9$ keV X-ray luminosity, compared to Cen X-4. This ratio is a factor of 10 smaller in quiescence, where the normalization of the V404 Cyg correlation also changes. We show that once the bolometric X-ray emission is considered and the known main differences between V404 Cyg and Cen X-4 are taken into account (a larger compact object mass, accretion disk size, and the presence of a strong jet contribution in the hard state for the black hole system) the two systems lie on the same correlation. In V404 Cyg, the jet dominates spectrally at optical-infrared frequencies during the hard state, but makes a negligible contribution in quiescence, which may account for the change in its correlation slope and normalization. These results provide a benchmark to compare with data from the 2015 outburst of V404 Cyg and, potentially, other transient LMXBs as well.Comment: Accepted on ApJ, 12 pages, 4 figures, 4 table

Expanding hot flow in the black hole binary SWIFT J1753.5-0127: evidence from optical timing

We describe the evolution of optical and X-ray temporal characteristics during the outburst decline of the black hole X-ray binary SWIFT J1753.5-0127. The optical/X-ray cross-correlation function demonstrates a single positive correlation at the outburst peak, then it has multiple dips and peaks during the decline stage, which are then replaced by the precognition dip plus peak structure in the outburst tail. Power spectral densities and phase lags show a complex evolution, revealing the presence of intrinsically connected optical and X-ray quasi-periodic oscillations. For the first time, we quantitatively explain the evolution of these timing properties during the entire outburst within one model, the essence of which is the expansion of the hot accretion flow towards the tail of the outburst. The pivoting of the spectrum produced by synchrotron Comptonization in the hot flow is responsible for the appearance of the anti-correlation with the X-rays and for the optical quasi-periodic oscillations. Our model reproduces well the cross-correlation and phase lag spectrum during the decline stage, which could not be understood with any model proposed before.Comment: 13 pages, 11 figures, MNRAS submitte

An investigation of the mechanisms of sound generation in initially laminar subsonic jets using the Goldstein acoustic analogy

This version has been accepted for publication.Published in Journal of Fluid Mechanics / Volume 714 / January 2013, pp 24 - 57 Copyright © Cambridge University Press 2013 DOI: http://dx.doi.org/10.1017/jfm.2012.448, Published online: 02 January 201