1、NASA TN D-36 TECHNICAL NOTE 0-36 ANALYSIS OF ACCELERATION, AIRSPEED, AND GUST-VELOCITY DATA FROM A FOUR-ENGINE TUBOPROP TRANSPORT OPEEATITdG OVER THE EASTERN UWTED STATES By Martin R. Copp and Mary W. Fetner Langley Research Center Langley Field, Va. NATIONAL AERONAUTICS AND SPACE ADMINISTRATION WAS
2、HINGTON September 19 59 (bASA-Tb-C-36) AbALYS-IS Cr ACCELEPATION, Hi3 9- 7 07 25 AIRSPEED ANC GL21-VELCCIZP CAlA EECB A CUR-EhGX8E TUGECFCF XFiAEZECLP CFERATJNG CVE8 18E EASIERE CNIIEI; SIAIE5 (hASAi Unclas Fanqlcy besearch CentEr) 54 OO/OS 0194262 r Provided by IHSNot for ResaleNo reproduction or n
3、etworking permitted without license from IHS-,-,-1A J TECHNICAL NOTE D-36 d ANALYSIS OF ACCELERATION, AIRSPEED, AND GET-VELOCITY DATA FROM A FOUR-ENGm TURBOPROP TRANSPORT OPERATING OVER THE EASTERN UNITED STATES By Martin R. Copp and Mary W. Fetner Airspeed, altitude, and acceleration data obtained
4、with an NASA (formerly NACA) VGH recorder installed in a four-engine turboprop trans- port operating over the Eastern United States were evaluated to deter- mine the magnitude and frequency of occurrence of gust velocities and gust and maneuver accelerations. The results obtained were then com- pare
5、d with the results previously obtained from two long-haul operations zti1izii-g transports equipped -ith four piston-type engines and f lo-rn over essentially similar routes. The gust and gust-load experiences for the turboprop operation were essentially similar to those for the piston-engine operat
6、ions. In addi- tion, the results indicated that maneuver-acceleration histories for the turboprop operation were similar to those for piston-engine operations previously sampled. conditions at a higher percentage of its design cruising speed than were the piston-engine transports. The turboprop tran
7、sport was flown during cruise INTRODUCTION Beginning about 1932, a continuing study of the magnitude and fre- quency of occurrence of gusts, gust accelerations, and maneuver acceler- ations experienced by transport airplanes in routine operations has been made. During this time, commercial airline o
8、perations have been system- atically sampled in order to obtain as wide a coverage as possible with regard to airplane types, operators, and geographical location of routes. Assessments of the effects of these variables on the gust and load his- tories and operating practices of the operations sampl
9、ed have then been made. With the introduction of turbine-powered transports, it might be expected that the operating practices and, therefore, loads histories would change because of differences in the characteristics of the new .1. airplanes and the current piston-engine airplanes. Provided by IHSN
10、ot for ResaleNo reproduction or networking permitted without license from IHS-,-,-2 4 In order to obtain statistical information on the gust loads and operating practices of these new airplane types, the National Aeronautics h and Space Administration has initiated a program with the cooperation of
11、the airlines to install NASA (formerly NACA) V-G and VGH recorders in several of their turbine-powered transports. The present paper presents an analysis of the initial sample of VGH data obtained from a four-engine turboprop transport operating over the eastern portion of the United States. boprop
12、transport are compared with those for two long-haul operations utilizing transports equipped with four piston-type engines and flown over essentially similar routes (ref. 1 and operation H-VI11 of ref. 2). The gust and load histories and operating practices of the tur- INSTRUMENTATION AND SCOPE OF D
13、ATA The data were collected with an NASA (formerly NACA) VGH recorder which obtains a continuous record of the airplanes indicated airspeed, pressure altitude, and normal acceleration for use in a study of the airplanes load history and its associated operating practices. detailed description of the
14、 recorder is given in reference 3. A The present data were obtained from routes flown over the eastern portion of the United States from June 1957 to September 1958. VGH data representing 1857.5 hours of flight were obtained; this number included 19.3 hours spent in check flights. A total of 1,347 o
15、perational flights were made during the record-collection period with an average flight duration of 1.36 hours. Cruising altitudes of these flights ranged from about 5,000 feet to 24,000 feet. - The characteristics of the airplane used in evaluating the VGH records and analyzing the data are as foll
16、ows: Design gross weight, W, lb . Average operating weight, lb Wing area, S, sq ft Mean geometric chord, E, ft Slope of lift curve, per radian Span, b, ft Aspect ratio, A computed from - 6A . ( A + 2 seeref. 4) . Design speed for maximum gust intensity (indicated), Design cruising speed (indicated),
17、 Vc, knots Vg, knots 63, ooo 53 , 500 963 93.7 9.1 10.3 4.92 166 238 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Never-exceed speed (indicated), VNE, knots . . . . . . . . . . . 272 0 Normal acceleration corresponding to the limit-gust-load- fact
18、or increment, LF , Maneuver Accelerations Operational- and check-flight-maneuver accelerations were evaluated b:. reading the appropriate peak deflections of the acceleration trace gr.:ater than a value of fO.lg. accelerations have been described in detail in previous papers. for example, ref. 7.) T
19、he procedures used to evaluate maneuver (See, Frequency distributions of positive and negative operational- and check-flight-maneuver accelerations are given in table 111. The total number of record hours, the amount of time actually spent in check flights, and the flight miles represented by the di
20、stributions are also shown in this table. The frequency of occurrence of positive and negative operational- and check-flight-maneuver accelerations for the turboprop operation are plotted in figure 4. distributions of gust accelerations are shown also in figure 4 for the turboprop trmsport . For com
21、parison, positive and negative frequency Gust Velocities Derived gust velocities Ude were calculated for each gust accel- eration peak by means of the revised gust-load formula of reference 8: where Ude w airplane weight, lb derived gust velocity, fps Provided by IHSNot for ResaleNo reproduction or
22、networking permitted without license from IHS-,-,-5 8n normal accel Kg gust factor r air density at PO tion, g units sea level, slugs/cu ft ve equivalent airspeed, fps m slope of lift curve per radian S wing area, sq ft The average airplane operating weight of 53,500 lbs was used in deter- mining th
23、e values of The resulting combined (positive and negative) frequency distributions of derived gust velocities for the turboprop operation are listed in table IV in class intervals of 4 feet per second for each 5,000-foot pressure-altitude interval and for the total operation. flight hours, flight mi
24、les, and the average number of gust velocities equal to or greater than 4 feet per second encountered per miie of flight for each aititude interval mi Cs the t.ot.ai operztlm given in table IV. % and in calculating the gust velocities. The number of slso The frequency of occurrence of gust velocitie
25、s for the complete operation is plotted in figure 5. for operations A and B are shown in figure 5 for comparison. Due to incomplete frequency counts of gust velocities less than 12 feet per second for operations A and B, the frequency of occurrence of gust velocities less than 12 feet per secviid g5
26、;s szittcd frcz firrllre 5 for the three operations shown. Gust-velocity frequency distributions u Operating Airspeeds The indicated airspeed and pressure altitude were read from the VGH records for each 1-minute interval of flight in order to obtain average airspeeds and pressure altitudes for the
27、climb, en route, and descent flight conditions and for the total data sample obtained. Average airspeeds in rough air were also computed to determine whether significant airspeed reductions were made upon encountering turbulence. These values were calculated from the 1-minute airspeed readings which
28、 were read during rough-air conditions. For this evaluation, any portion of the VGH record was considered to represent rough air if the acceler- ation trace contained gust-acceleration peaks of at least f0.2g. Aver- age airspeed values for the overall operation and for the rough-air phases of the gp
29、eration are listed in table I as fractions of for Vc Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-6 the climb, en route, and descent. flight conditions. Similar airspeed ratios for operations A and B are shown also in table I. For opera- tions A a
30、nd B, however, airspeeds in rough air were defined as airspeeds at which gust accelerations greater than +0.3g were encountered. RELIABILITY OF RESULTS Instrument errors in the VGH recorder and installation errors have been discussed in detail in reference 9. These errors are not considered of suffi
31、cient magnitude to affect the reliability of the present results. Reading errors, however, can affect the reliability of the results as indicated in reference 10. The effect of these errors tends to diminish as the data sample increases up to about 1,000 hours after which it remains essentially cons
32、tant. For the present operation (1857.5 hours), it is estimated that the acceleration and derived-gust-velocity values for the total operation are reliable to within kl3 percent for a given frequency of occurrence at the lower values. The reliability of the dis- tributions for 5,000-foot altitude in
33、tervals and for the climb, en route, and descent flight conditions is somewhat less due to the smaller amount of data in each distribution. The reliability of the gust accelerations and derived gust veloc- ities for operation A (operation F-VI of ref. 2; 1,038 hours) and oper- ation B (operation H-V
34、I11 of ref. 2; 1,721 hours) is estimated also to be about +l5 percent. L 4 5 0 In addition to reading errors, sampling variations may also affect the reliability of the VGH data. Estimates of the statistical relia- bility of the total data sample were made, based on the method described in reference
35、 6, and indicated that the total distributions of gust accel- eration and gust velocity (figs. 2 and 5) are statistically reliable within a factor of about 2 on the ordinate scale at the smaller values and within a factor of about 3 at the higher values. were determined for operations A and B. Simil
36、ar estimates DISCUSSION Gust Accelerations and Gust-Load Histories Comparison of the curves of figure 2 indicates that for the three operations shown no differences are apparent in the frequency of occur- rence of gust accelerations. This might be expected since the routes flown and operating charac
37、teristics of the airplanes as noted in fig- ure 1 are essentially similar. It should be noted, however, that a Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-7 L 4 5 0 c turboprop airplane is capable of operating efficiently at other air- speeds and
38、 altitudes and other operations may differ significantly from the one sampled. A breakdown of the VGH gust-acceleration data into distributions for the climb, en route, and descent conditions indicated that the greatest number of gust accelerations 2 0.2g per mile of flight were encountered during t
39、he descent condition and the least number during the en route or cruise condition (table 11). These results are in gen- eral agreement with previous investigations. (See, for example, ref. 6. ) The curves of figure 3 indicate that the load history (based on exceeding given fractions of the computed
40、limit-gust-load-factor incre- ment) for the turboprop operation is approximately the same as for oper- ation A and slightly more severe than for,operation B. However, the differences as shown in figure 3 do not appear to be significant. Maneuver Ac ce ler at ions Figure 4 indicates that positive and
41、 negative frequency distribu- tions of gust accelerations as well as operational- and check-flight- maneuver accelerations are approximately spnetrical fer the turbcprcp operations and that the maximum positive gust and check-flight-maneuver accelerations were larger than the negative values. The re
42、sults shown in figure 4 are in general agreement with previous investigations (refs. 6, 7, and 11) which indicated that generally, for the smaller acceleration values, the gust accelerations are more frequent than the maneuver accelerations. For some operations (ref. 6), however, the frequency of th
43、e larger maneuver accelerations (1.Og or greater) may equal the frequency of the gust accelerations. noted for the positive maneuver accelerations (fig. 4) from the present operation. It is felt, therefore, that the relative contribution of the maneuver accelerations to the total flight load history
44、 is probably dependent upon individual piloting techniques as well as different oper- ational procedures used by the various airlines. Such a tendency may be Gust Ve lo c i t i e s Figure 5 shows that essentially no differences exist among the fre- quencies of occurrence of gust velocities for the t
45、hree operations. The similarity of the gust distributions would normally be expected since most of the VGH data for the three operations were obtained over essen- tially the same portion of the United States at approximately the same altitudes. Provided by IHSNot for ResaleNo reproduction or network
46、ing permitted without license from IHS-,-,-a A further breakdown of the gust-velocity data was made (table IV) to determine the variation of gust frequency with pressure altitude for the altitude range covered by the turboprop operation. that a fairly orderly decrease in gust frequency with increasi
47、ng pres- sure altitude existed from sea level to about 20,000 feet. For the 20,000- to 25,000-foot altitude interval, however, no further reductions were observed. data obtained for altitudes above 20,000 feet. tional data for the higher altitudes are needed before any definite trends can be establi
48、shed for airline operations although references 12 and 13 indicate that a decrease in gust frequency should continue to much higher altitudes. It was found This may be due to the comparatively small amount of (See table IV.) Addi- Airspeed Practices Ll 4 5 0 An examination of table I indicates that
49、the turboprop transport was flown during en route or cruise conditions at a higher percentage of its design cruising speed In addition, reductions of 3 percent and 7 percent, respectively, of are apparent for the cruise and descent conditions in turbulent air for the turboprop operation. For the piston-engine airplanes, however, no reductions in the average airspeeds upon encoun
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