1、LANGLEU WORKNG PAPER 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 Walter B. Horne, Thomas J. Yager, Robert K. Sleeper NASA Langl
2、ey Research Center and Leslie R. Merritt Federal Aviation Administration This paper is given limited distribution and is subject to possibl in 4 ,for5aiPffAj/ FEB f972 i 1 e F 5-i, 1 .Cyiirg ,.*, - . 5 . . . c 3;: wet = average DBV wet stopping distance time correlated to aircraft run, ft 842 = DBV
3、stopping distance in section A at time 0 (time of aircraft test) from figure 27, ft a,. a. 650 = length of rubber-coated surface in test section, ft . ? 731 = DBV stopping distance in section D at time 0 (time of ., aircraft test) from figure 27, ft 2810 = length of uncontaminated surface in test se
4、ction, ft 3460 = aircraft stopping distance from start of test section, ft (see table IX) L L . The average DBV wet stopping distance obtained by this technique for run 43 was 752 feet and this is the value noted in table IX. A similar data reduction technique was used for all DBV runs where the tes
5、t section surface was not uniform in texture. For uniform test section surfaces, the DBV runs in different areas of the test section were given equal weight and arithmetically averaged to obtain an average wet stopping distance for the time of aircraft run and noted in table IX. 3.7.2.6 The DBV SDR
6、(wet/dry stopping distance ratio) time correlated to each aircraft run was obtained by dividing the wet DBV stopping distance by the dry stopping distance listed in table IX for each wet aircraft test run. 3.7.3 Mu-Met er 3.7.3.1 The Mu-Meter was towed at constant speed (usually 40 mph) over the sec
7、tion of the runway to be measured. In addition to the test speed of 40 mph, some runs in this investigation were made with the Mu-Meter at speeds of 20 and 60 mph to obtain data on the effect of speed on Mu-Meter readings. Typical test records obtained with the Mu-Meter before and after aircraft run
8、 43 at Houston are shown in figure 13. The Mu-Meter instrumentation included a remote mechanical integrator which automatically read out an average friction reading for the length of test section measured by the Mu-Meter on the runway. The integrator average friction reading obtained for each test r
9、un of the Mu-Meter is listed in table VIII. For most aircraft runs, the aircraft did not require the full runway test section length to come to a complete stop. Consequently, the Mu-Meter test records were analyzed only over the portion of the test section (see figure 13) in which the aircraft test
10、occurred. In this manner, the average, maximum,and minimum friction readings of the Mu-Meter were obtained for the length of the runway test section associated with the Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-aircraft test, These Mu-Meter ave
11、rage record friction readings for each test run are also listed in table VIII. 3.7.3.2 The Mu-Meter average record friction reading at 40 mph was time- correlated with aircraft test run 43 as shown in figure 27. In this figure, the Mu-Meter average record friction reading at 40 mph taken before and
12、after the aircraft test run was plotted against time from aircraft run data obtained from table VIII. An interpolated Mu-Meter friction reading of 0.423 was obtained by this method as the Mu-Meter runway slipperiness indication at the time aircraft run 43 was made. All of the Mu-Meter test runs made
13、 at 40 mph test speed were analyzed in this manner and the time-correlated Mu-Meter average friction readings are listed in table IX. 3.7.33 For those Mu-Meter test runs made at speeds other than 40 mph, the time-correlated record average friction readings were plotted against test speed for each ai
14、rport as shown in figure 28. With the aid of this figure, it was possible to obtain an interpolated record average friction reading value for an aircraft test run at an airport even though the Mu-Meter test speed for the particular aircraft run was not made at 40 mph. For example, the Mu-Meter test
15、speeds before and after aircraft run 46 at Houston were made at 60 mph. From the Houston curve of figure 28, an interpolated friction reading of 0.430 was obtained at 40 mph test speed. This friction reading value is listed in table IX. This technique was followed for all other Mu-Meter runs in whic
16、h the test speed was not 40 mph and the interpolated friction values listed in table IX. 3.7.4 Average Runway Test Section Water Depth 3.7.4.1 Water depth measurements were made beside each runway marker by the water depth measuring test crew in the aircraft left, nose, and main wheel tracks of the
17、runway test section at three separate intervals during an aircraft test run sequence. These many individual water depth measure- ments were used to determine the average test section water depth values listed in table VI. These water depth values were plotted against the time from aircraft run data
18、in table VI (see figure 27) so that an interpolated value of average test section water depth at time of aircraft run could be obtained. In figure 27, this technique yielded an average test section water depth of 0.019 at the time aircraft run 43 was made. This procedure was followed for each aircra
19、ft wet test run and the results obtained are listed in tables V and IX. 4.0 RESULTS AND DISCUSSION 4.1 All test results have been time-correlated to the time of the air- craft test as explained in paragraph 3.0 above. These results are presented in table IX for each test site by run number. The data
20、 contained in table IX and table VI were used, for the most part, in preparing the figures presented in this section. . Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-4.2 NASA Wallops Station 4,2.1 Nine maximum braking stops were made at NASA Wallop
21、s Station on runway 10/28 in addition to nine calibration runs and 10 flooded test section tests, The flooded tests are not addressed in this paper, but will be analyzed at a later date. The water depth variation with time for runway 10/28 at Wallops is shown in figure 29(a). It can be seen that for
22、 all wet runs except run 12, the average water depth at the time of aircraft landing was 0.01 inch. 4.2.2 For run 12, the water depth at time of aircraft test was 0,019 inch. With this water depth condition, the airplane at a light weight of 99,500 pounds and a relatively high brake application spee
23、d of 117 knots, the two outboard wheels locked up six seconds after the brakes were applied, A total of 18 brake pressure application/release cycles were accomplished by the anti- skid system before full lockup occurred. The anti-skid system did not permit the outboard wheels to regain synchronops s
24、peed once they had spun down to a speed which caused brake pressure release, This is summarized in table XI, As a result of the wheel lockup, a large reverted rubber patch was generated on each of the outboard tires. Figure 30 shows the nature and size of the reverted rubber patch. 4.2.3 All of the
25、data points obtained at Wallops for the aircraft, DBV, and Mu-Meter are shown in figure 29(a), It is readily apparent that the air- craft point for run 12 falls outside any correlation boundary. This seems obvious since a tire operating in the reverted rubber skidding mode can produce a much reduced
26、 friction coefficient compared to that produced by an efficiently operating anti-skid system, The effect of new tires on aircraft stopping distance ratio can also be seen in the figure. Figure 31 shows the actual time histories of the pertinent aircraft parameters for dry, wet (no wheel lockups) and
27、 wet (two wheels locked) conditions. The computed coeffi- cient of friction values are also given in these figures, Examination of the coefficient of friction plots indicates, as stated above, th8t the friction developed in the case where wheel lockups occurred and reverted rubber skids were present
28、 is much lower than for the cases where no wheel lockups occurred, This phenomenon will be discussed further in 4.8.1 below, 4,3 Houston Intercontinental Airport 4.3.1 Four dry and six wet maximum braking stops were made at Houston Intercontinental Airport on runway 08L, The water depth variation wi
29、th ti+e for the six wet runs is shown in figure 29(b). Each run was faired separately to obtain the data shown in table IX. The average water depth varied from 0.016 inch to 0.028 inch at the time of aircraft test, Three of the wet stops experienced lockup of the two outboard wheels, These lockups o
30、ccurred from 2.14 seconds to 3.82 seconds after brake application. Four to eight anti-skid system pressure application/release cycles occurred prior to lockup (see table XI), These lockups occurred over a wide weight and speed range and in water depths of 0.027 to 0.028 inch. I 4.3,2 All of the data
31、 points obtained at Houston for the aircraft, DBV, and Mu-Meter are shown in figure 29(b). It is interesting to note that although the aircraft SDR obtained from run 41, which was conducted with worn Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-ti
32、res, falls outside the correlation boundaries, the SDRPs obtained from runs 46 and 47, which were conducted with new tires, falls within the corre- lation boundaries. Thus, even in the condition where two outboard wheels are locked and skidding, the inboard wheels, which are really generating the br
33、aking force, are much more effective with new tires than with worn tires, Figure 32 shows the actual time histories of the pertinent aircraft parametex for dry, wet (no wheel lockups) and wet (two wheels locked) condi- tions. The computed coefficient of friction values are also given in these figure
34、s. Figure 30 shows the nature and size of the reverted rubber skid patch developed during prolonged locked wheel skids at Houston. Edwards AFB 4,k.l Four dry and eight wet maximum braking runs were made at Edwards AFB on runway 04. In addition, two runs were made using normal reverse thrust on all t
35、hree engines and maximum braking after touchding down in the wetted test section. The water depth variation with time for the wet runs is shown in figure 29(c). Each run was faired separately to obtain the data shown in table IX. The average water depth varied from 0.024 inch to 0,049 inch. For runs
36、 50 and 53, one percent of organic foam was mixed with the water to obtain a water depth greater than that for water alone. Commencing with run 53, a third water tanker was used to increase the amount of water dis- charged onto the runway. All wet stops except run 97 experienced either two- or four-
37、wheel lockups. Table XI shows the time of wheel lockup after brake application and the number of anti-skid pressure/release cycles which occurred prior to lockup. In four instances, prolonged locked wheel skids generated reverted rubber in the tire footprint producing low aircraft decelerations whic
38、h resulted in the aircraft exiting the wetted test section. For these four cases, a plot of the deceleration versus velocity was made down to the point where the airplane exited the test section. The trend of the curve at that point was extrapolated to zero velocity and the average deceleration was
39、used to compute an incremental distance to stop which would have been realized if the wetted test section had been sufficiently long The incre- mental distances used were as follows: Run - The stopping distances for these runs shown in table IX include these incre- mental values. 4.4.2 All of the da
40、ta points obtained at Edwards for the aircraft, DBV, and Mu-Meter are shown in figure 29(c). In all cases, the aircraft data fall ,outside of the correlation boundaries. This, again, is caused by the low friction realized as a result of wheel lockups and reverted rubber skidding. It is also evident
41、in these data that the new tires effect a re6uction in the aircraft SDR. Figure 33 shows the actual time histories of the pertinent aircraft parameters for dry, wet (two wheels locked), wet (four wheels locked), Provided by IHSNot for ResaleNo reproduction or networking permitted without license fro
42、m IHS-,-,-and wet (no wheels locked, reverse thrust applied and brake application speed = 94 knots). The computed coefficient of friction values are also given in these figures. For figure 33(d), the magnitude of the computed friction coefficient is higher than actual since the effect of reverse thr
43、ust was not included in the calculation. This effect will be considered in the final report. 49 5 Seattle-Tacoma International Airport 4.5.1 Three dry andfivewet maximum braking runs were made at Sea-Tac on runway 16. In addition, two runs were made using normal reverse thrust on all engines and max
44、imum braking after touching down in the wetted test section. It is characteristic of the Sea-Tac grooved runway that in a matter of seconds after the water tankers passed a water depth measuring station there was no measurable depth of water on the runway. Thus, only a damp condition was available f
45、or test. This is reflected in all the data shown in figure 29(d) where the stopping distance ratios in the cases of the aircraft and DBV are very nearly 1.0 and the friction measurement taken by the Mu-Meter is but slightly less than for the dry condition. Figure 34 presents typical time histories o
46、f the pertinent aircraft parameters for the dry and wet (damp) surface conditions. The computed coefficient of friction values are also given in these figures. It is typical of some grooved runways that tire tread cutting (chevron cutting) is produced at the initial contact and spin- up of the aircr
47、aft tire, The runway at Sea-Tac produced such cutting as is shbwn in figure 30. 4.6 Lubbock Regional Airport 4.6.1 Four dry and seven wet maximum braking runs were made at Lubbock Regional Airport on runway 08. In addition, two dry and two wet runs were made using normal reverse thrust on all three
48、engines and maximum braking. On run 98 the brakes were applied gradually over a period of approximately five seconds rather than in an abrupt manner as in all the other maximum braking tests, This was done to assess the stopping distance associated with a normal airline stopping procedure. The water
49、 depth variation with time for the wet runs is included in figure 29(e). Each run was faired separately to obtain the data shown in table IX. The average water depth varied from 0.024 inch to 0.034 inch. Five of the wet runs experienced lockups of the two main outboard wheels. Table XI shows the time of wheel lockup after brake application and the number of anti-skid system pressure/release cycles which occurred prior to lockup. The smooth asphalt surface at Lubbo
