1、NASA TECHNICAL NOTE|Z,ZNASA TN D-4330AN ANALYSIS OF VGH DATAFROM ONE TYPE OF FOUR-ENGINETURBOJET TRANSPORT AIRPLANEDURING COMMERCIAL OPERATIONSby Paul A. HunterLangley Research CenterLangley Station, Hampton, Va.NATIONAL AERONAUTICS AND SPACEADMINISTRATION WASHINGTON, D. C. FEBRUARY 1968Provided by
2、IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NASA TN D-4330AN ANALYSIS OF VGH DATA FROM ONE TYPEOF FOUR-ENGINE TURBOJET TRANSPORT AIRPLANEDURING COMMERCIAL OPERA
3、TIONSBy Paul A. HunterLangley Research CenterLangley Station, Hampton, Va.NATIONAL AERONAUTICS AND SPACE ADMINISTRATIONFor sale by the Clearinghouse for Federal Scientific and Technical InformationSpringfield, Virginia 22151 - CFSTI price $3.00Provided by IHSNot for ResaleNo reproduction or networki
4、ng permitted without license from IHS-,-,-_ _ i_ _Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-AN ANALYSIS OF VGH DATA FROM ONE TYPEOF FOUR-ENGINE TURBOJET TRANSPORT AIRPLANEDURING COMMERCIAL OPERATIONSBy Paul A. HunterLangley Research CenterSUMMA
5、RYAn analysis of VGH records collected on one type of four-engine turbojet transportduring routine commercial operations on two airlines has provided information on accel-eration, turbulence, and airspeed operating practices. The data cover operations of twoairplanes by one airline on eastern United
6、 States and Caribbean routes and of one airplaneoperated by a second airline on routes which ranged along the east coast of the UnitedStates, across the Caribbean Sea and along the west coast of South America.For the two airplanes operated by the same airline, the results were very simi-lar in regar
7、d to the gust-velocity experiences and the accelerations caused by gusts,operational maneuvers, check-flight nmneuvers, and landing impact. The results indi-cated that the acceleration experiences, the gust velocity experiences, and the airspeedoperating practices were not significantly different fo
8、r the airplanes operated by the twoairlines. The amount of rough air encountered at various altitudes and the gust veloci-ties experienced during both operations were in overall agreement with previouslypublished estimates of the gust environment. In general, the airspeeds in rough air(gust velocity
9、 =2 fps (0.6 m/sec) were approximately equal to the airspeeds in smoothair. The results indicated, however, that the airspeeds in heavy turbulence (gust veloci-ties higher than 20 fps (6.1 m/sec) were generally lower than the average operatingspeeds.INTRODUCTIONConcurrent with the introduction of tu
10、rbine-powered airplanes into commercialtransport operations, the NASA initiated a program for collecting data on normal accel-eration, airspeed, and altitude from routine airline operations. These measurementsare being utilized to provide statistical data on a number of operational aspects of thetur
11、bine-powered aircraft, such as accelerations experienced during gusts, maneuvers,and oscillations; operating practices; and landing impact accelerations. This programis a continuation of the long-standing NACA/NASA effort to collect operational data onProvided by IHSNot for ResaleNo reproduction or
12、networking permitted without license from IHS-,-,-commercial transport airplanes. In the past, information obtainedfrom the data collec-tion program has proved useful for comparison of the operational experiences of air-planeswith the conceptsto which they were designed,for detection of new or unant
13、icipatedaspectsof the operations, and as backgroundinformation for application in the design ofnewairplanes. Typical results obtainedfor several types of airplanes are given in ref-erences 1 to 6.This paper presents an analysis of the accelerations experienced,the gust veloci-ties encountered,and th
14、e operating airspeeds and altitudes of onetype of four-engineturbojet transport during operations on two airlines. Someof the preliminary datafromtheseoperations havebeenreported in references 6 and 7, but are included herein toprovide a summary of the operations. Information onexceedancesof placard
15、 speedsisnot included becauseit was presentedin reference 7, and subsequentchangesin theplacard speedmarkings and overspeedwarning margins detract from its present utility.SYMBOLSThe units used for the measurementsof this investigation are given in both U.S.Customary Units and the International Syst
16、em of Units (SI). Factors relating the twosystems are given in reference 8.A aspect ratioa n incremental normal acceleration, g unitsc wing chord, ft (meters)g acceleration due to gravity, 32.2 ft/sec 2Kg gust factor,m5.3 + pglift-curve slope, per radian,6 AcosAA + 2 cos2A(9.81 meters/second 2)A + 2
17、 cos A )A/1-M2cos2A + 2 cos AM Mach numberMNE never-exceed Mach numberMNO normal operating limit Mach number-N:-Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-S wing area, sq ft (meters 2)Ude derived gust velocity, fps (meters/second)V e equivalent
18、airspeed, fps (meters/second)VNE never-exceed speed, knots (indicated)VNO normal operating limit, airspeed, knots (indicated)W airplane weight, lbf (newtons)A sweep angle of wing quarter-chord line, deg2Wpg airplane mass ratio, mpcgSP atmospheric density, slugs/ft 3 (kilograms/meter 3)Po atmospheric
19、 density at sea level, slugs/ft 3 (kilograms/meter 3)INSTRUMENTATION AND SCOPE OF DATAThe data were collected with NASA VGH recorders, which provide continuous time-history records of indicated airspeed, normal acceleration, and pressure altitude. Adetailed description of the VGH recorder is given i
20、n reference 9. The normal accelera-tions were sensed by an accelerometer located in the main-landing-gear wheel well nearthe airplane center of gravity. Pressure lines for the recorder were connected to thecopilots airspeed system.The two airplanes of operation A were operated on routes covering the
21、 eastern halfof the United States and part of the Caribbean Sea. The airplane of operation B wasoperated on routes which extended along the east coast of the United States, across theCaribbean Sea, and along the west coast of South America.The scope of the data samples for the two airplanes (A-1 and
22、 A-2) of operation Aand the one airplane (B-l) of operation B is summarized in table I. As shown in thetable, the sizes of the data samples from the individual airplanes ranged from about 1240flight hours to 1700 flight hours. Airplane check and pilot-training flights accounted for53 to 134 flight h
23、ours per airplane. The histograms of flight durations are given in fig-ure 1 (a) and the histograms of altitude are given in figure 1 (b) for the two operations.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-As shownin table I, the data sampleswere
24、collected betweenJanuary 1960andDecember 1962. The records were rather uniformly spacedthroughoutthe recordingperiod for airplanes A-2 andB-1. Althoughirregular intervals occurred betweenrecordsreceived from airplane A-I, the longer recording period for this sample tendedto com-pensateand to give, o
25、n a monthly basis, a uniform sample. Consequently,it is thoughtthat eachof the datasamples is representative of year-round operations.Airplane characteristics pertinent to the evaluation of the data are given in table II.Inasmuchas the two models of the airplane used in operations A and B are geomet
26、ricallyidentical, single values are given for all characteristics exceptweights andwing loadings.EVALUATION OF DATA AND RESULTSGeneralEachflight on the VGH records wasclassified as beingeither a routine passenger-carrying operational flight or a checkflight for pilot training or airplane testing. Ch
27、eckflights were distinguished from operational flights by the higher amplitude and frequencyof occurrence of maneuver accelerations and by larger and more irregular variations inairspeed and altitude.The operational flights were divided into three segments representing climb,cruise, and descent cond
28、itions. Both climb and descent occasionally included shortperiods of level flight as a result of operational or air traffic-control procedures. Thecruise condition occasionally included periods when the airplane was climbing ordescending to a different cruise altitude. Operational flights were also
29、divided into seg-ments representing flight in rough or smooth air. The airplane was considered to be inrough air during the traverse of any continuous turbulent area which produced at leastone acceleration corresponding to a gust velocity of about 2 fps (0.6 m/sec) or higher.The average operating we
30、ights during each 30-minute interval of flight were codedon the records for subsequent correlation with the gust accelerations. These weightswere based on weight data obtained from the airlines and on average fuel consumptionrates of the airplanes.Accelerations Due to GustsThe criterion used to dist
31、inguish gust accelerations from maneuver accelerationswas that gust accelerations have a much higher frequency content and are accompaniedby high-frequency low-intensity fluctuations of the airspeed trace. In the event that agust acceleration was superimposed on a maneuver acceleration, the maneuver
32、 accelera-tion was used as the reference. The evaluation of gust accelerations consisted of readingpositive and negative incremental acceleration peaks above a threshold of 0.2g using the4Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-1g position of
33、 the acceleration trace as a reference. Only the maximum peak for eachcrossing of the reference and threshold was read. For each acceleration peak read, thecorresponding airspeed and altitude were also read.The frequency distributions of the combined (positive and negative) accelerationsby flight co
34、ndition and for the total samples are given in table HI for each airplane. Theflight hours, nautical miles, and average true airspeed associated with each distributionare listed. The flight miles used throughout this report are nautical miles, computed bymultiplying appropriate values of time in hou
35、rs and average true airspeed in knots. Infigure 2(a) the cumulative frequency distributions of accelerations per nautical mile arepresented by flight condition for each airplane. These distributions were formed byprogressively summing the frequency distributions of table HI, beginning with the large
36、stacceleration, and dividing each sum by the flight distance of the sample. The cumulativefrequency per mile of accelerations for the total sample for each airplane of operation Ais given in figure 2(b) and for the total sample of the two operations is given in figure 2(c).Accelerations Experienced
37、During ManeuversOperational and check-flight accelerations were evaluated by reading each peakacceleration greater than a value of +0.1g relative to the 1 g reference. Only the maxi-mum value for each crossing of the reference was read. Frequency distributions of thepositive and negative operational
38、 accelerations by flight condition and total are given intable IV(a). Frequency distributions of positive and negative check-flight accelerationsare given in table IV(b). The amount of time spent in check flights, the total of opera-tional and check-flight record hours, and the nautical miles associ
39、ated with each distri-bution are listed. The nautical miles spent in check flights are computed as the productof the overall average true airspeed and the total time listed in the table. Cumu-lative frequency distributions of positive and negative operational maneuver accelerationsfor each airplane
40、are given in figure 3(a). Cumulative frequency distributions of com-bined operational maneuver accelerations by flight condition are given in figure 3 (b). Thedistributions of figure 3 (b) were divided by the flight distance of the sample, and theresulting distributions are presented in figure 3(c).
41、 Cumulative frequency distributionsper mile of combined operational maneuver accelerations for operations A and B and forthe airplane of reference 5 are given in figure 3(d). Cumulative frequency distributionsper mile of positive and negative check-flight maneuver accelerations are given in fig-ure
42、4. Total check-flight miles were used in computing each point for either positive ornegative accelerations. The airplane of reference 5 was the same model as those flownin operatio n A but was flown by a third operator. The number of flight hours in thesample of reference 5 was about the same as tha
43、t for airplane A-l.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Accelerations Experienced During OscillationsSamplerecords shownin figure 5 illustrate four types of oscillations notedonrecords from the present airplanes. In somecasesthe motions we
44、re evidenton the air-speedand altitude traces as well as on the acceleration trace. Accelerations wereevaluatedby countingpeaks abovea threshold of +0.05g. The duration of each occurrenceof oscillation was noted and used to calculate the percent of flight time spent in oscilla-tions. The flight time
45、 and nautical miles of the sample evaluated and the percent of timeoscillations occurred for each sample are listed in table V. Figure 6 indicates the per-cent of flight time that oscillations greater than a given magnitude occurred. The cumu-lative frequency distributions of oscillatory acceleratio
46、ns per mile of flight are shown infigure 7 for each airplane.Flight Loads SummaryIn order to indicate the relative importance of accelerations from various sources,the cumulative frequency distributions of gust, operational maneuver, check-flight maneu-ver, and oscillatory accelerations per mile of
47、flight are shown in figures 8(a), (b), and(c) for airplanes A-l, A-2, and B-l, respectively. The distributions from the varioussources were combined for each airplane as an indication of the total in-flight loads andare compared in figure 9.TurbulenceAmount of rough air.- The percent of time in each
48、 5000-foot (1.52 km) altitudeinterval thai was spent in rough air was determined by calculating the ratio of the timein rough air to the total flight time for each altitude interval. The results are presentedin figure 10 for operations A and B, together with similar data from reference 10 for awide
49、variety of aircraft.Gust velocities.- A value of derived gust velocity Ude was calculated for eachgust acceleration peak by means of the revised gust-load formula of reference 11:2Wa nUde =KgPoV e m SThe airplane weights W were, as mentioned previously, based on weights obtainedfrom each operator and included the effects of fue
