Piloted simulator study of allowable time delays in large-airplane response

A piloted simulation was performed to determine the permissible time delay and phase shift in the flight control system of a specific large transport-type airplane. The study was conducted with a six degree of freedom ground-based simulator and a math model similar to an advanced wide-body jet transport. Time delays in discrete and lagged form were incorporated into the longitudinal, lateral, and directional control systems of the airplane. Three experienced pilots flew simulated approaches and landings with random localizer and glide slope offsets during instrument tracking as their principal evaluation task. Results of the present study suggest a level 1 (satisfactory) handling qualities limit for the effective time delay of 0.15 sec in both the pitch and roll axes, as opposed to a 0.10-sec limit of the present specification (MIL-F-8785C) for both axes. Also, the present results suggest a level 2 (acceptable but unsatisfactory) handling qualities limit for an effective time delay of 0.82 sec and 0.57 sec for the pitch and roll axes, respectively, as opposed to 0.20 sec of the present specifications for both axes. In the area of phase shift between cockpit input and control surface deflection,the results of this study, flown in turbulent air, suggest less severe phase shift limitations for the approach and landing task-approximately 50 deg. in pitch and 40 deg. in roll - as opposed to 15 deg. of the present specifications for both axes

Spectroscopy of Hadrons with b Quarks from Lattice NRQCD

Preliminary results from an extensive lattice calculation of the B, B_c, and \Upsilon spectrum at quenched \beta = 6.0 are presented. The study includes radially and orbitally excited mesons, and baryons containing b quarks. The b quarks are formulated using NRQCD; for light and c quarks, a tadpole-improved clover action is used.Comment: talk given at LATTICE98(heavyqk), 3 pages LaTeX, 2 Postscript figure

Self-replenishing low-adherence coatings

Low-adherence coatings are widely used today since their water/oil repellency makes them easily cleanable (a well-known example is PTFE). The low surface tension is provided by fluorine- or silicon-containing species that are present at the film surface. Low adherence coatings have already been developed via surface segregation of fluorinated species. However, it has been shown that the fluorine-enriched layer is very thin, and the coating may not sustain low adherence upon mechanical abrasion. An approach to develop self-replenishing low surface energy coatings is to distribute long perfluoroalkyl-end-capped chains relatively homogeneously in a coating network. In case of surface damage that leads to the loss of the top layers of the coating, fluorinated tails from sub-layers will be able to reorient themselves to minimize the air/film interfacial energy. In order to study the self-replenishing behavior, model polyester precursors with controlled functionality were synthesized via controlled ring-opening polymerization of e-caprolactone using perfluoroalkyl alcohol or polyol as initiators. The as-prepared precursors were cured with polyisocyanate crosslinker to obtain films with low surface energy. The fluorine depth profile and the self-replenishing behavior have been investigated. The influence of the mobility of polymer spacer and network, as well as temperature, on the self-replenishing behavior will be discussed

Low adherence coating containing polymers with low surface energy

A low adherence coating comprises: (a) a crosslinked polymeric network (N), based on a first polymer (P), (b) a low-surface-energy group (E), coupled to the network via (c) a polymeric spacer (S), having the following relationship between the native surface energies of P, E, and S (resp. sp, se, and ss,, in mN/m): se <ss <sp. The coatings have a low adherence towards different types of contaminants. A coating contained a polycaprolactone terminated with perfluorooctyl ethanol. [on SciFinder (R)

Low adherence coating

The invention relates to a coating having a low adherence towards different types of contaminants. Such a coating comprises a crosslinked polymeric network provided with an end-functionalized dangling chain, as a result of which the surface maintains its low surface energy