Engineering topics
Publications and source records attributed to Holmes, B. J..
A computer code has been developed for predicting trajectories of particles released in the wakes of airplanes or helicopters. The code accounts for effects of turbulence, crosswind, propeller slipstream, terrain variations, and plant canopy density on particle trajectories. Comparisons are given between experiments and theory. Applications of the code for spray pattern improvement are illustrated.
The results of natural laminar flow (NLF) experiments conducted by NASA to determine if modern aircraft structures can benefit from NLF as do sailplanes are presented. Seven aircraft, ranging from a Cessna 210 to a Learjet 28/29, with relatively stiff skins were flown in production configurations with no modifications. Measurements were made of the boundary-layer laminar to turbulent transition locations on various aerodynamic surfaces, the effect of a total loss of laminar flow, the effect of the propeller slipstream on the wing boundary-layer transition and the boundary-layer profiles, the wing section profile drag, the effect of flight through clouds, and insect debris contamination effects. Favorable pressure gradients for NLF were concluded to be feasible up to a transition Reynolds number of 11 million. Laminar flows were observed in propeller slipstreams, and insects were found to cause transition 1/4 of the time.
The prospects for significantly increasing the fuel efficiency and mission capability of single engine business aircraft through the incorporation of advanced propulsion, aerodynamics and materials technologies are explored. It is found that turbine engines cannot match the fuel economy of the heavier rotary, diesel and advanced spark reciprocating engines. The rotary engine yields the lightest and smallest aircraft for a given mission requirement, and also offers greater simplicity and a multifuel capability. Great promise is also seen in the use of composite material primary structures in conjunction with laminar flow wing surfaces, a pusher propeller and conventional wing-tail configuration. This study was conducted with the General Aviation Synthesis Program, which can furnish the most accurate mission performance calculations yet obtained.
Experimental results obtained at NASA Langley during studies of natural laminar flow (NLF) over commercially produced aircraft surfaces are reported. The general aviation aircraft examined were light aircraft, yet displayed NLF extents close to the maximum available and equivalent to high performance business aircraft flying envelopes. Sublimating chemicals and acoustic detection techniques were employed to measure the boundary layer transition. Theoretical predictions of boundary layer stability were found to match well with the experimental data, with consideration given to both swept wings and the amplitudes of allowable waves on the airfoil surfaces. The presence of the NLF on the airfoil surfaces confirmed the benefits available from use of composite materials for airfoil surfaces.
Design data are presented for a class of high-performance single-engine business airplanes. The design objectives include a cruise speed of 300 knots, a cruise altitude of 10,700 m (35,000 ft), a cruise payload of six passengers (including crew and baggage), and a no-reserves cruise range of 1300 n.mi. Two unconventional aerodynamic technologies were evaluated: the individual and combined effects of cruise-matched wing loading and of a natural laminar flow airfoil were analyzed. The trade-off data presented illustrate the ranges of wing geometries, propulsion requirements, airplane weights, and aerodynamic characteristics which are necessary to meet the design objectives. Very large design and performance improvements resulted from use of the aerodynamic technologies evaluated. It is shown that the potential exists for achieving more than 200-percent greater fuel efficiency than is achieved by current airplanes capable of similar cruise speeds, payloads, and ranges.
A flight evaluation was conducted to determine the effects of winglets on the performance and handling qualities of a light, single-engine general aviation airplane. The performance measurements were made with a pace airplane to provide calibrated airspeeds; uncalibrated panel instruments in the test airplane were used to provide additional quantitative performance data. These tests were conducted with winglets on and off during the same day to measure relative performance effects. Handling qualities were evaluated by means of pilot comments. Winglets increased cruise speed 8 knots (5.6 percent) at 3962 m (13,000 ft) density altitude and 51 percent maximum continuous power setting. Maximum speed at 3962 m was virtually unchanged. Rate of climb increased approximately 6 percent, or 0.25 m/sec (50 ft/min), at 1524 m (5000 ft). Stall speed was virtually unchanged. Handling qualities were favorably affected.
A design study has been conducted to optimize a single-engine airplane for a high-performance cruise mission. The mission analyzed included a cruise speed of about 300 knots, a cruise range of about 1300 nautical miles, and a six-passenger payload (5340 N (1200 lb)). The purpose of the study is to investigate the combinations of wing design, engine, and operating altitude required for the mission. The results show that these mission performance characteristics can be achieved with fuel efficiencies competitive with present-day high-performance, single- and twin-engine, business airplanes. It is noted that relaxation of the present Federal Aviation Regulation, Part 23, stall-speed requirement for single-engine airplanes facilitates the optimization of the airplane for fuel efficiency.
Recent flight and wind tunnel evaluations of winglets mounted on general aviation airplanes have shown improvements in cruise fuel efficiency, and climbing and turning performance. Some of these analyses have also uncovered various effects of winglets on airplane handling qualities. Retrofitting an airplane with winglets can result in reduced cross wind take-off and landing capabilities. Also, winglets can have a detrimental effect on the lateral directional response characteristics of aircraft which have a moderate to high level of adverse yaw due to aileron. Introduction of an aileron-rudder-interconnect, and reduction of the effective dihedral by canting-in of the winglets, or addition of a lower winglet can eliminate these flying quality problems.
A standard service airspeed system on a single engine research support airplane was calibrated by the trailing anemometer method. The effects of flaps, power, sideslip, and lag were evaluated. The factory supplied airspeed calibrations were not sufficiently accurate for high accuracy flight research applications. The trailing anemometer airspeed calibration was conducted to provide the capability to use the research support airplane to perform pace aircraft airspeed calibrations.
An analysis procedure is given and cases analyzed for the effects of wing geometry on lateral transport of a variety of agricultural particles released in the wake of an agricultural airplane. The cases analyzed simulate the release of particles from a fuselage centerline-mounted dry material spreader; however, the procedure applies to particles released anywhere along the wing span. Consideration is given to the effects of taper ratio, aspect ratio, wing loading, and deflected flaps. It is noted that significant lateral transport of large particles can be achieved using high-lift devices positioned to create a strong vortex near the location of particle release.
Aerial applications research conducted by NASA seeks improvements in environmental safety, fuel efficiency, and aircraft productivity and safety. From 1976 to 1978, NASA studied the technology needs of the aerial applications industry and developed in-house research capabilities for meeting those needs. This paper presents the research plans developed by NASA. High potential appears to exist for near term contributions to the industry from existing NASA research capabilities in drift reduction, stall departure safety, and dry materials dispersal system technology. A brief, annotated bibliography is included listing documents recently produced as a result of NASA aerial applications research efforts.
Research airspeed systems on three low-speed general aviation airplanes were calibrated by the trailing anemometer method. Each airplane was fitted with an NASA pitot-static pressure tube mounted on either a nose or wing boom. The uncalibrated airspeed systems contained residual static-pressure position errors which were too large for high-accuracy flight research applications. The trailing anemometer calibration was in agreement with the tower flyby calibration for the one aircraft for which the comparison was made. The continuous deceleration technique for the trailing anemometer method offers reduced test time with no appreciable loss of accuracy for airspeed systems with pitot-static system lag characteristics similar to those described.
Project organization and execution, airplane description and performance predictions, and the results of the flight evaluation of an advanced technology light twin engine airplane (ATLIT) are presented. The ATLIT is a Piper PA-34-200 Seneca I modified by the installation of new wings incorporating the GA(W)-1 (Whitcomb) airfoil, reduced wing area, roll control spoilers, and full span Fowler flaps. The conclusions for the ATLIT evaluation are based on complete stall and roll flight test results and partial performance test results. The Stalling and rolling characteristics met design expectations. Climb performance was penalized by extensive flow separation in the region of the wing body juncture. Cruise performance was found to be penalized by a large value of zero lift drag. Calculations showed that, with proper attention to construction details, the improvements in span efficiency and zero lift drag would permit the realization of the predicted increases in cruising and maximum rate of climb performance.
The present status and flight-test results are presented for the ATLIT airplane. The ATLIT is a Piper PA-34 Seneca I modified by the installation of new wings incorporating the GA(W)-1 (Whitcomb) airfoil, reduced wing area, roll-control spoilers, and full-span Fowler flaps. Flight-test results on stall and spoiler roll characteristics show good agreement with wind-tunnel data. Maximum power-off lift coefficients are greater than 3.0 with flaps deflected 37 deg. With flaps down, spoiler deflections can produce roll helix angles in excess of 0.11 rad. Flight testing is planned to document climb and cruise performance, and supercritical propeller performance and noise characteristics. The airplane is scheduled for testing in the NASA-Langley Research Center Full-Scale Tunnel.