1、EVALUATION OF BRAKING PERFORMANCE OF A LIGHT, TWIN-ENGINE AIRPLANE ON GROOVED AND UNGROOVED PAVEMENTS by Thomas J. Yager, W. Pelham Phils, and Perry L, Deal Langley Reseurch Center Hampton, Va. 23365 NATIONAL AERONAUTICS AND SPACE ADMINISTRATION WASHINGTON, D. C. OCTOBER 1971 Provided by IHSNot for
2、ResaleNo reproduction or networking permitted without license from IHS-,-,-TECH LIBRARY KAFB, NM Illllli11111111111111lllllllllllllllIll1111 4. Title and Subtitle 5. Report Date EVALUATION OF BRAKING PERFORMANCE OF A LIGHT, October 1971 TWIN-ENGINE AIRPLANE ON GROOVED AND UNGROOVED 6. Performing Org
3、anization Code PAVEMENTS 7. Author(s) 8. Performing Organization Report No. Thomas J. Yager, W. Pelham Phillips, and Perry L. Deal L-7643 10. Work Unit No. 9. Performing Organization Name and Address 133-61-12-01 .NASA Langley Research Center 11. Contract or Grant No. Hampton, Va. 23365 13. Type of
4、Report and Period Covered 12. Sponsoring Agency Name and Address ITechnical Note National Aeronautics and Space Administration 14. Sponsoring Agency Code Washington, D.C. 20546 15. Supplementary Notes . 16. Abstract The braking performance of a nine-place, light, twin-engine airplane was evaluated o
5、n comparative grooved and ungrooved surfaces of the landing research runway at NASA Wallops Station. The test airplane was equipped with manual braking on the main wheels of the tricycle landing gear, and its weight varied from 33.4 to 35.6 kN (7500 to 8000 Ib). The test results indicate that paveme
6、nt grooving significantly improves aircraft braking and directional control on wet runways. Measurements and observations of airplane tire treads made during this test program showed no indication of unusual wear and/or damage attributable to grooved surfaces. Comparative braking data obtained with
7、a jet fighter and a civil and a military jet transport are also presented. 7. Key-Words (Suggested by Author(s) I 18. Distribution Statement Airplane braking performance Unclassified - Unlimited Runway surface treatments Runway slipperiness due to adverse weather 19. Security Classif. (of this repor
8、t) 20. Security Classif. (of this page) 21. NO. of Pages 22. Price Unclassified Unclassified 34 $3.00 _ -. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-EVALUATION OF BRAKING PERFORMANCE OF A LIGHT, TWIN-ENGINE AIRPLANE ON GROOVED AND UNGROOVED PAV
9、EMENTS By Thomas J. Yager, W. Pelham Phillips, and Perry L. Deal Langley Research Center SUMMARY The braking performance of a nine-place, light, twin- engine airplane was evaluated on comparative grooved and ungrooved surfaces of the landing research runway at NASA Wallops Station. The test airplane
10、 was equipped with manual braking on the main wheels of the tricycle landing gear, and its weight varied from 33.4 to 35.6 kN (7500 to 8000 lb). The test results indicate that pavement grooving significantly improves aircraft braking and directional control on wet runways. Measurements and observati
11、ons of airplane tire treads made during this test program showed no indication of unusual wear and/or damage attributable to grooved surfaces. Comparative braking data obtained with a jet fighter and a civil and a military jet transport are also presented. INTRODUCTION It is generally recognized tha
12、t the installation of transverse grooves in runway pave ments provides improved tire traction under adverse weather conditions and thereby increases the safety of aircraft ground operations. The results from pavement grooving studies at the Langley landing-loads track (ref. 1) were sufficiently enco
13、uraging to effect the installation of a landing research runway at NASA Wallops Station, Virginia. This run way, described in reference 1, was constructed primarily to study the effects of pavement grooving on full-scale aircraft take-off and landing performance in simulated adverse weather conditio
14、ns. Since March 1968, the NASA has been engaged in a research program to study the braking performance of various types of aircraft on the comparative grooved and ungrooved surfaces of the landing research runway. Test airplanes were selected for this research to provide a wide variation in the majo
15、r parameters which affect braking performance; namely, airplane weight, landing-gear arrangement, braking system, and tire inflation pressure. The selected airplanes included a two-engine jet fighter (McDonnell Douglas F-4D), and two four-engine jet transports (Convair 990A and Lockheed C-141A) all
16、of which were equipped with antiskid braking systems. The results from the braking per formance studies of these airplanes are presented in references 1to 5 and indicate that the braking capability under adverse weather conditions is significantly improved when the various pavements are transversely
17、 grooved. I Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-The purpose of this report is to present the results from braking performance tests of the Beech Queen Air B80, a business-type airplane equipped with a manual braking sys tem. Over 100 brak
18、ing test runs were conducted with this airplane on the various test surfaces of the landing research runway under dry, wet, flooded, and ice-covered surface conditions. The results of these tests are presented in terms of braking friction coeffi cients computed from measurements recorded onboard the
19、 airplane. Information is also presented concerning the effects of braking on tire tread life and the airplane directional control on grooved and ungrooved surfaces. Comparative braking data obtained with two jet transports and a jet fighter are pre sented in the appendix. The principal factors affe
20、cting the braking performance of each test airplane are listed to provide a basis for evaluating the braking test results. SYMBOLS Measurements for the dimensional quantities presented herein were originally taken in U.S. Customary Units but are presented also in the International System of Units (S
21、I). Conversion factors relating the two systems of units are given in reference 6. longitudinal acceleration, g units (lg = 9.81 m/sec2 = 32.17 ft/sec2) total drag force (rolling resistance included), newtons (pounds) vertical force acting on main wheel axle, newtons (pounds) tire inflation pressure
22、, newtons/centimeter2 (pounds/inch2) ground speed, knots hydroplaning speed, knots airplane weight, newtons (pounds) braking friction coefficient effective braking friction coefficient (average p developed by airplane as modified by pilot braking or antiskid braking system) maximum braking friction
23、coefficient Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-APPARATUS Test Airplane The test airplane used in this braking investigation is the Beech Queen Air B80, a nine-place, twin-engine, low-wing monoplane with a gross test weight which varied b
24、etween 33.4 and 35.6 kN (7500 and 8000 lb). The general geometric characteristics of the airplane are shown in figure 1. The airplane is equipped with a tricycle landing gear incorporating hydraulic disk brakes on the main gear and a steerable, unbraked nose wheel. No electrical antiskid fea tures a
25、re incorporated in the landing-gear design. In these tests, however, the available wheel braking torque was insufficient to cause wheel skidding on dry pavements. The main-gear tires are type 111, 8.50 X 10 and have a circumferential four-groove tread design, and the nose gear utilized a four-groove
26、, type 111, 6.50 X 10 tire. Inflation pressures for the main- and nose-gear tires were 32.4 and 24.1 N/cm2 (47 and 35 lb/in2), respectively. Runway Surfaces A schematic view of the landing research runway at NASA Wallops Station is pre sented in figure 2 together with photographs which give an indic
27、ation of the texture of each of the nine test surfakes comprising the 1050-m (3450-ft) test section. A level (both transversely and longitudinally) 427-m (1400-ft) concrete section and a 427-m (1400-ft) asphalt section are separated by a 198-m (650-ft) Gripstop transition surface having a longitudin
28、al slope of 0.1 percent. Each of the test surfaces, identified by code letters A to I, have surface treatments described as follows: SurfaceA - Ungrooved concrete with canvas-belt drag surface finish Surface B - Grooved concrete with canvas-belt drag surface finish Surface C - Grooved concrete with
29、burlap drag surface finish Surface D - Ungrooved concrete with burlap drag surface finish Surface E - Ungrooved rock asphalt (Gripstop) Surface F - Ungrooved small-aggregate asphalt Surface G - Grooved small-aggregate asphalt Surface H - Grooved large-aggr egate asphalt Surface I - Ungrooved large-a
30、ggregate asphalt Each test surface is 107 m (350 ft) in length except for surface E which is 198 m (650 ft). The grooves of surfaces B, C, G, and H are cut transversely in a geometrically similar pattern: 0.63 cm (1/4 in.) wide and deep, spaced 2.54 cm (1in.) apart. The small and 3 Provided by IHSNo
31、t for ResaleNo reproduction or networking permitted without license from IHS-,-,-large aggregate used in the asphalt test surfaces refer to stone sizes less than 0.95 cm (3/8 in.) and 1.91 cm (3/4 in.), respectively. A more detailed description of the runway surfaces is given in reference 7. The bra
32、king performance of the instrumented test airplane was evaluated on the comparative grooved and ungrooved test surfaces under dry surface conditions and under two different surface wetness conditions: namely, wet with isolated puddles and flooded to a water depth which ranged from 0.25 cm (0.1 in.)
33、to 0.76 cm (0.3 in.). In addition, braking tests were conducted on the small-aggregate asphalt (surfaces F and G) under an ice-covered runway condition. Photographs of a test surface for the wet and the flooded test conditions are presented as figure 3. An ice-covered test condition was achieved on
34、the small-aggregate asphalt (sur faces F and G) by spraying water on these surfaces when the ambient temperature was -7.8O C (18 F) and allowing the water, both on the surface and in the grooves of sur face G, to freeze. During a test run, the airplane braking distance for these ice-covered surface
35、conditions was less than 53 m (175 ft). Instrumentation The test airplane was instrumented to measure and record continuous oscillograph traces of airplane attitude and accelerations, the angular velocity of the wheels, the brake-pedal pressures, and such information relative to the airplane braking
36、 characteristics as engine speed and the landing-gear shock-strut response. The main instrument package, shown in figure 4, was located near the airplane center of gravity and served as a mount for the accelerometers, attitude sensors, and recording equipment. Sample oscillograph records which show
37、the measured responses during brake application on wet and flooded surfaces are reproduced in figure 5. Also identified in the figure are the relative airplane ground speeds and the runway test surfaces encountered during the test. A visual display of right- and left-main-wheel ground speed was prov
38、ided so that wheel lockups could be monitored during maximum-braking tests. This display also served to aid the pilot in achieving the desired test speed for brake application. In addi tion, extensive ground and aerial photographic coverage was used during the tests to moni tor and record test event
39、s, airplane motions (such as lateral drifting and weather cocking), and the behavior of the main-landing-gear system. TEST PROCEDURE The testing technique consisted of taxiing the airplane at preselected ground speeds onto the desired runway test section, applying maximum braking, and recording the
40、air plane response. Prior to these braking performance tests, the airplane was operated at 4 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-various constant ground speeds over a measured distance to permit a calibration of the ground-speed instrumen
41、tation. In addition, free-roll tests (propellers windmilling) were performed on the different surfaces to evaluate the total airplane drag at ground speeds corresponding to those encountered during the braking tests. The braking tests were conducted with propellers windmilling and, in general, inclu
42、ded half of two adjacent grooved and ungrooved test surfaces of similar surface com position (e.g., surfaces A and B) to permit a comparison of the runway surface treatment at a consistent brake-pedal pressure. This technique subjected the test airplane to heavy braking for a distance of approximate
43、ly 107 m (350 ft). The relatively small braking dis tance was desirable since the airplane was found to be highly responsive to cross winds during braking on low-friction surfaces at speeds below minimum rudder-control speed (approximately 80 knots). Comparative braking effectiveness data were colle
44、cted at ground speeds which ranged from approximately 20 to 110 knots. PRESENTATION OF DATA Data describing each airplane braking test were obtained from an oscillograph record of the outputs of the onboard instruments. The sample records reproduced in fig ure 5 typify the data which include a time
45、history of airplane accelerations, brake pres sures, and the corresponding angular velocities of each main-gear wheel. Also included in the figure are the nature of the runway surface and the airplane ground speed. The ground speed throughout each test run was determined by using an onboard ground-s
46、peed indicator to obtain the initial velocity prior to brake engagement and then integration of the longitudinal deceleration to provide the velocity time history. The brake-pressure trace identifies the time and extent of brake application, and the wheel-velocity trace is used to denote wheel locku
47、ps (when wheel rotational velocity equals zero). The magnitude of the longitudinal deceleration is a measure of the braking effectiveness of the airplane for a particular test condition. To evaluate the braking performance of the aircraft, the effective braking friction coefficient peff was computed
48、 from the equation of motion which described the forces on the airplane while it is operating with windmilling propellers (thrust approximately equal to zero). This equation is where W is the airplane weight, ax is the longitudinal acceleration in g units (taken from the oscillograph record), D is t
49、he total drag (rolling resistance included) on the airplane determined from free-roll tests at various ground speeds, and FZ is the 5 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-vertical load on the main-gear tires as computed from the recorded strut pressures. The variation of wheel loading with ground speed is typified by the
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