4,036 research outputs found
A new method for measuring slipperiness of airport runways and other paved surfaces
Aircraft stopping distances on wet runways are accurately predicted by measurements taken with a conventional automobile equipped with diagonal braking system and simple instrumentation for recording stopping distances
Friction evaluation of unpaved, gypsum-surface runways at Northrup Strip, White Sands Missile Range, in support of Space Shuttle Orbiter landing and retrieval operations
Friction measurement results obtained on the gypsum surface runways at Northrup Strip, White Sands Missile Range, N. M., using an instrumented tire test vehicle and a diagonal braked vehicle, are presented. These runways were prepared to serve as backup landing and retrieval sites to the primary sites located at Dryden Flight Research Center for shuttle orbiter during initial test flights. Similar friction data obtained on paved and other unpaved surfaces was shown for comparison and to indicate that the friction capability measured on the dry gypsum surface runways is sufficient for operations with the shuttle orbiter and the Boeing 747 aircraft. Based on these ground vehicle friction measurements, estimates of shuttle orbiter and aircraft tire friction performance are presented and discussed. General observations concerning the gypsum surface characteristics are also included and several recommendations are made for improving and maintaining adequate surface friction capabilities prior to the first shuttle orbiter landing
Influence of Tire Tread Pattern and Runway Surface Condition on Braking Friction and Rolling Resistance of a Modern Aircraft Tire
A series of taxiing tests was conducted at the Langley landing loads track with both braked and unbraked (freely rolling) single and tandem wheels equipped with 32x8.8 type VII aircraft tires of different tread designs to obtain data on tire and braking characteristics during operation on dry and on contaminated concrete and asphalt run ways. Contaminants used were water, slush, JP-4 jet fuel, and organic and detergent fire-extinguishing foams. Forward velocities for the tests ranged from approximately 13 to 104 knots. Vertical loads of approximately 9,000 to 22,000 pounds and tire inflation pressures of 85 to 350 pounds per square inch were used. Results indicated that the unbraked tire rolling resistance increased with increasing forward velocity on dry and on contaminated runway surfaces. Peak tire-ground friction coefficients developed during wheel braking decreased rapidly with increasing velocity on contaminated runways but remained relatively unchanged on dry runways as the forward velocity was increased. Dry-runway friction coefficients were found to be relatively insensitive to tire tread pattern. However, the magnitude of the friction coefficients developed by tires on contaminated runways was extremely sensitive to the tire tread pat tern used, with circumferential-groove treads developing the highest values of friction coefficient, and smooth and dimple treads the lowest values for the tread patterns and runway conditions investigated
Some effects of adverse weather conditions on performance of airplane antiskid braking systems
The performance of current antiskid braking systems operating under adverse weather conditions was analyzed in an effort to both identify the causes of locked-wheel skids which sometimes occur when the runway is slippery and to find possible solutions to this operational problem. This analysis was made possible by the quantitative test data provided by recently completed landing research programs using fully instrumented flight test airplanes and was further supported by tests performed at the Langley aircraft landing loads and traction facility. The antiskid system logic for brake control and for both touchdown and locked-wheel protection is described and its response behavior in adverse weather is discussed in detail with the aid of available data. The analysis indicates that the operational performance of the antiskid logic circuits is highly dependent upon wheel spin-up acceleration and can be adversely affected by certain pilot braking inputs when accelerations are low. Normal antiskid performance is assured if the tire-to-runway traction is sufficient to provide high wheel spin-up accelerations or if the system is provided a continuous, accurate ground speed reference. The design of antiskid systems is complicated by the necessity for tradeoffs between tire braking and cornering capabilities, both of which are necessary to provide safe operations in the presence of cross winds, particularly under slippery runway conditions
Surveyor spacecraft system - Surveyor 6 flight performance Final report
Surveyor 6 spacecraft flight performance characteristics, including data on television equipment, alpha scattering experiment, and powered flight translatio
Preliminary test results of the joint FAA-USAF-NASA runway research program. Part 1: Traction measurements of several runways under wet and dry conditions with a Boeing 727, a diagonal-braked vehicle, and a mu-meter
The stopping distance, brake application velocity, and time of brake application were measured for two modern jet transports, along with the NASA diagonal-braked vehicle and the British Mu-Meter on several runways, which when wetted, cover the range of slipperiness likely to be encountered in the United States. Tests were designed to determine if correlation between the aircraft and friction measuring vehicles exists. The test procedure, data reduction techniques, and preliminary test results obtained with the Boeing 727, the Douglas DC-9, and the ground vehicles are given. Time histories of the aircraft test run parameters are included
High spectral resolution time-resolved optical spectroscopy of V893 Sco
We present high resolution time-resolved optical spectra of the high
inclination short orbital period dwarf nova V893 Sco. We performed spectral
analysis through radial velocity measurements, Doppler mapping, and ratioed
Doppler maps. Our results indicate that V893 Sco's accretion disk is dissimilar
to WZ Sge's accretion disk, and does not fit any of the current accretion disk
models. We derive the system parameters M1 and i, and present evidence for V893
Sco as a very young cataclysmic variable and an ER UMa star. We advance the
hypothesis that all ER UMa stars may be newly formed cataclysmic variables.Comment: 23 pages (total), 8 figures, accepted by Ap
- …