Flight load spectrum: tracker aircraft

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Flight load spectrum: tracker aircraft

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NATI ONAL A ERONAUTICAL ESTAB L ISHMENT

OTTAWA, CANADA

LABORATORY MEMORANDUM

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SUBJECT PFIEPAFIED a v I SS U ED TO Ii II Op e n

SECU RI TY C LASSIFIC ATI O N ... .

FLIGHT LOAD SPECTRUM - TRACKER AIRCRAFT

ｾ＠ fi.\-u., ｾｾ＠ !...J 1.,,,.1,,.J /f)..L G. F . W. Mcca f frey Inte r nal N .. C - C !9TJ AERO J M. E. LI BRARY

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TH I S MEM Ol'tAN C U M IS I S S U E D TO FURNISH IN F ORM A T I O N

IN ADVANCE OP' A A•PO R T . I T I S P RELIMINARY IN C HAR ACTER ,

H AS N O T REC EI V ED THE C AR EFUL EDI T I NG OF A REPO RT. ANO

The Tracker aircraft has been in service with the Canadian Armed Forces for approximately 20 years, with

individual aircraft accumulating some 8,000 flying hours in that period . With the object of extending the useful life of the aircraftJ a fatigue test is about to begin on a specimen which consists of an airframe whi ch was taken out of service at just over 5,000 hours, fitted with outer wings which have been modified in the vicinity of the wing-fold

joint. The centre - section and outer wine93are fitted with new attachment fittings .

Over the past 10 years, 8 recording acce l erometer systems have been employed to obtain counts of exceedances of discrete values of aircraft normal acceleration during vari ous periods of flying time. Each of these systems consists of a sensor and two registers which permit counts at 8 levels. In September 1971 the pattern of counting

levels employed was altered to improve the rec ording efficiency of the system. The latter data, after editing, is stored in a computer which is programmed to make certain logic checks and to provide print-outs of the acceptable data by aircraft together with maximum and minimum values and linearly deter -mined means and standard deviati ons a t each recording level.

Examination of these print - outs reveals some ra t h e r

alarmingly large values of exceedances per flying hour at t he

2.0 to 4.0 "g" levels compared to similar data from other sources and to the data gathe red prior to September 1971 in this program. In addition, they would appear to constitute a rather severe fatigue spectrum for the tes t aircraft and suggest a very real possibility of exceeding the Ul tima te Jesign Load (4 .5g ) of t he aircraft in a n unacceptab l y short

1 1 11

The analysis, reported herein was undertaken to arrive at a spectrum which would represent normal flying · and could be used to commence testing, and to attempt to isolate by aircraft and time period the occurrence of ab- . normal values to assist in understanding their origin and significance.

2.0 METHOD

2.1 Linear Analysis

The data available consisted of the computer file print -out to October

1978

and the individual reporting forms . Visual scanning of the print-out identified a pattern of long periods of what might be called "normal flying" inter-spersed by bursts of data (usually a single entry which might cover 1 to 6 months for that aircraft) which were characterized

by unusually large counts at one or more of the higher and/ or lower g levels. The l evels recorded in the data file are -0.5, O, .5, 1 . 5 , 2.0~ 2.5, 3 . 5·and 4.0 . . By rejecting these entries by inspection it was apparent that the resulting spectrum was quite close to that obtained by utilizing all of the data recorded prior to September

1971

and also to a spectrum generated by Grumma.n from·· u

.s;

Navy recording accelerometers.

The rejected data showed a strong tendency to be concentrated across the instrumented aircraft especially in the reporting periods after the change of register settings

(involving re-wiring the electrical harness) and in early

1973,

In an attempt to devise a more formal method of screening t he data, an analysis was carried out in which an entire l ine (and the associated flying hours) was rejected if any two (of eight) levels exceeded the limits of the mean ±4 Standard Deviations as determined by the computer-generated values of those parameters. Examination of t he rejected data against the reporting forms raised a strong

suspicion that many were the result of failure to deduct

counts put on during servicing and calibration of the syste~s. A sma ll amount of the remaining data was rejected during

inspection of the reporting forms, resulting in the spectru:n labelled "clean data", hereinafter. Other samp les such as all 1974 data were examined by a similar analysis for com-parison.

2.2 Log- Normal Analysis

It had become apparent during the above-described linear analysis and close examination of the data that

numerous entries whic h appeared to have insufficient counts at some levels were not rejected because the criterion of mean minus 4 Standard Deviations was zero for all except t he 2g level. Detailed examination of the data for aircraft 12195 showed that the exceedances at each leve l were distri-buted log-normally i.e. the logarithms of the exceedance values were distributed about the mean logarithm in the

form of a "normal" distribution. It is considered reasonable to assume that data for all flying would be similarly dis-tr ibuted.

As will be discussed in section 3.0 below a

criterion of Mean ±2 Standard Deviations in the log-no rmal analysis is a more discriminating test than mean ±4 Standard Deviations applied as though the data \'ere norma lly distributed .

. Log- normal means and Standard Deviations (S.D.'s) from samples generated in the arithmetic (linear) analysis were used to establish upper and lower limits (criteria) at each level which could be applied to the individual reports of flying hours and ac celeration counts. Some difficulty was encountered in establishing values for the 3.5g level because the vast majority of entries wer~ zero. To overcome this problem , the flying hours associated with zero counts were all applied to the next occurring count of 3.5g as re -corded in the computer print - out . A similar procedure was

11,

I I

adopted, when required, at the 2.5g l evel. Using these

criteria1 the entire file was examined by individual aircraft and as grouped data rejecting all data in an entry if the criterion . Mean ±2 S.D.'s indicated too low or too high counts at any level between 0.5g and 3,5g. This process produced a sample of 8879.2 hours of data whose spectrum was very similar to the "clean data" previously described. In view of the difficulty of establishing appropriate criteria for 3.5g, entries rejected at that level (3 out of over 200) were subsequently restored to the sample without appreciable effect on the spectrum which resulted.

A similar analysis was conducted on the data from the original register settings. Since these data are rela-tively free of unusually high counts (and contain no 4g occurrences in 4500 flying hours) the resulting spectrum is quite similar to that obtained by taking arithmetic means at each level.

3.0 DISCUSSION OF RESULTS

3.1 The Effects of Various Analysis Methods

To assist the reader in appreciating the merits of using log-normal analysis in refining the raw data Figure 1 .shows a linear representation of the distribution of a log-normal population having a mean and S.D. closely approximating that of the 3.5g data in the file. Superimposed on this

are the criterion limits mean ±4 S.D.'s (linear) and mean ±2 S.D.'s (log-normal). It is immediately apparent that the latter is far less demanding at the upper limit and yet

allows the exclusion of data for insufficient counts such as will occur if the instrument is inoperative for part of the reporting period.

If the data were from a uniform distribution one would expect to reject slightly less than 5 per cent of the entries at the mean ±2 S.D. level but in actual fac t about one-third is rejected, more or less equally distributed

11 ·1 I,

1111

between too many and too few counts. No 4g counts remain but · by re - introducing data rejected at the 3 . 5g level (only) ,

5

counts of

4g

re - appear with no significant changes at any other l evels of the spectrum.

Table 1 shows the effect of various sampling strategies on the arithmetic means and Table 2 on the log-normally - determined means. Table 3 is a compilation of the log- normally-determined means, standard deviations and log (means) by aircraft and grouped . The values labelled "all" are not the arithmetic means of the individual aircraft but rather over- all values of the grouped (fleet) data.

Figure 2,

3

and

4

display some of the tabulated data in the form of flight load spectra. It is readily apparent that only minor discrepancies exist in the data after systematic removal of unusually high and low counts. As a matter of fact, these spectra are very similar to one generated early in the analysis by simply "eye-balling " the raw data and deleting entries which, by inspection, appeared to contain "spurious" data.

3.2 Possible Explanations of Non- Conforming Data

Low counts do not require too much explanation since they usually appear to be the result of a failure of the measuring system during the period in question which may be confirmed by the appearance of an "all-zero" entry in the following period . On occasion one register fails to record and this will be evident from examination of the record since the "A" register ends at 1.5g and the "B" re-gister begins at 2.0g both of which should normally produce other than zero counts except for very short reporting

periods.

Incideritally, the desirability of ri g idly-enforced, short, reading - intervals (not more than one month) has been repeatedly demonstrated during this study both as an aid in isolating spurious data and preventing loss of large segments

11

of good data which may be lumped with a short burst cf dubious data or in the case of instrument failure rejected for

insufficient counts, during part of the reporting period. The presence of excessive counts particularly at the 2.5 to 4.0g levels and less frequently at the - 0.5 to +0 .J5 le¥els (although they often coincide) : presents two very serious problems . They may result in an overly- conser-vative test spectrum with resulting financial penalties but , far more import~ntly, if they are the result of flying, the risk of loss of life through break- up of an aircraft in flight is unacceptably high. The latter statement is based not only on the recorded exceedances of 4g but also on the knowledge from calibration of 2 of the systems (ex

aircraft 12188 and 12195) that 4.2 to 4 . 4g is required at the sensor to register a count of 4g and a patter n of such readings in a relatively short r ecor ding period i mpl i es that the Design Ultimate Load factor has probably been exceeded. It may be that the production aircraft has a static strength in excess of 4.5g at design A.U.W . or that these counts are registered in aircraft confi gurations which are less demanding than that which was tested . The static test conducted by

Grumman some 25 years ago resulted in the achievement of a load factor of 5.27g after at least two failures below the required 4.5g and subsequent repair of the test specimen but the record is not too clear as to the relevance of that test to the Canadian- manufactured aircraft and current oper-ating conditions .

It seems generally agreed·, at this time, that the abnormal counts are the . result of short periods of intense flying or counts added, but not recorded, during routine

servicing and checking of the instruments or some combination of these.

There is a good deal of circumstantial evidence to support a theory that most, lf not all, arise from the latt er cause. Three methods of calibration are referred to in t h e report forms, two of which are formal calibrations which artificially put either single counts on each register or a burst of approximately 1,000 on each register. Only one

I

instance of the latter can be identified and it is properly documented. The former is documented in most instances, although occasionally as on a/c 12195 for the period ending

29/5/73 one has apparently slipped through but, in general, it would be difficult to identify these when combined with flying data. The third method, sometimes referred to as a calibration consists of simply shaking the sensor with power on and either or both registers connected. The pattern

produced, as documented on occasion, and from direct experience in this laboratory, when combined with one to six months

flying will only be recognizable to the extent of the apparently excessive counts at the extreme ends of the registers.

In further support of this view there is not a single count of

4g

in ~500 hours of data at the original register settings but 100 are recorded (of 133 total in the file) in a period of 7300 hours immediately following this when re- wiring of all systems and the necessary checking

(and resulting familiarity with the . system's characteri stics) almost certainly produced the flood of counts at both extremes of the counting levels, which in all probability had nothing to do with flying. The following year (1974) produced only one count of

4g

in

1673

hours .of data and that was in air-craft 12173 whose system went unserviceable one mont~ later for a period of

4!

years. Interestingly enough the same

system, one month after it was restored to operating condition by repairing an open circuit in its power supply at a

micro-switch in the landing gear bay, produced the largest single accumulation of 4g counts in a single reporting period (26

1

in

55.5

hours) during a month in which it apparently took part in 2 days of rocket-firing. The other instrwnented aircraft on the same exercise recorded none in 61.6 hours although it did exhibit higher than normal counts at lower levels.

Various other explanations involving for example removal of the g-limiter and the introduction of a fighter flight-path for rocket-firing do not appear to be supported by the facts; in particular, more counts of 4g were recorded in an equivalent period before these measures were introduced than after. (It is assumed that all g limiters were removed circa January 1973 as recorded in the log- book of the test specimen a/c 12167. )

It seems entirely reasonable that manual shaking of the sensor (with power on) would be a widely-practised method of ensuring that the system is functioning. In fact, it has advantages overt.he formal calibrationmethod normally used in that it ehecks the function of the system rather

than just the registers. This advantage was documented in the case of the system in a/c 12173, previously mentioned, on which, after

3!

years of nil data, a formal calibration (documented) confirmed that the registers were functi oning but no records were obtained for a further year because there was no power on the system . Shaking the sensor would have clearly indicated the malfunction~ Hewever it may not be obv ious to the technician servicing the unit that such false counts must be recorded and reported to the meter-reader. Ten to 15 counts of 4g·, and larger numbers of other positive g levels can easily be registered in 20 seconds of vigorous shaking and 2 to 5 4g-counts would be required to ensure that there is a one-to- one correspondence of

4g

counts with the maximum positive acceleration applied.

Very little appears to be known of the actual f light capability of this aircraft other than what can be deduced

from these records. The Grumman flight test report of pr ot o-type flying shows 2g as the maximum positive level achieved. Uncontaminated data in this analysis such as those at higher

register settings, and in the year

1974 ,

suggest that limit

load (3g) is exceeded rather more frequently (5 to 8 times per 1,000 hours) than might be expected for any type of aircraft. This would be consistent with a 3,5g exceedance 1 to 3 times per 1000 hours, on average, and assuming the necessary control authority and pilot motivation a

4g

exceed-ance in several thousand hours. It is considered beyond the realm of probability (possib ility) that

26

exceedances of

4g

could be accumulated . in 2 days of rocket-firing as

stated on the reporting form for a/c

12173

for October

1978

i.e. in 10 to 15 hours . of flying, approximately, or

9

in

8 . 7

hrs. as recorded for a/c 12197 in Feb.

1973

and · other similar reports .

4.0

CONCLUSIONS AND RECOMMENDATIONS

4.1

It is proposed that the fatigue test be started based on the flight load spectrum of figure 4, on the under-standing that it may be necessary tomodify it to a more-or less - demanding form at some future time.

4.2 Since it is proposed to continue recording monthly data from 7 systems it is recommended that these reports be monitored for high and low counts preferably at the squadron levels so that any unusual occurrences can be

immediately investigated and findings reported in the remarks column provided on the form. To accomplish this the techni cian who reads the registers could be provided with a simplified control table such as shown in Appendix A. · It is considered that such an approa.ch would improve the quality of the limited amount of data (3,000 hours per year approximately) which

will become available during testing and may provide additional understanding of existing data, ·ror very little additional

10

-effort. The appended table is based on the log-normal mean ±2 S.D. rounded to whole numbers at the mid-interval flying hours .

4,3 It is strongly recommended that any instrumented aircraft that participate in rocket firing exercises, or any similar activities, in the next year or two do so with maximum attention being paid to ensuring the quality of

the recorded data . Recommended procedures would include (but no t be limited to) flight -b y-flight rec ording of register counts, duplicated. recording systems and/or con-tinuous trace recordings of each pass, pilot interviews, comp l ete control of any servicing or calibration of the instruments and removal of any restrictions on flight accel-erations other than the pilot's judgement.

4.4

The techniques used in this analysis, particularly the log-normal analysis when applied to homogeneous log-nor-mal data should establish the true mean, which should be that of the original data. Since it is not, except for the 1.5g level, it must be concluded that the original data is not homogeneous. Although strong· evidence exists to support a contention that most of the contaminating data are not the result of flying, their extreme effect on the flight load spectrum is sufficient justification for a continuing program within D.N . D. to seek understanding of their source in existing records as well as in future operations.

12

11

10!

9

8

ACTUAL DISTRIBUTION OF A SIMULATED

3.5g LOG-NORMAL DISTRIBUTION

HAVING L06 CHEAN)• 2.S AND STD . DEV.• 0 . 75

CCOMPARE

A/C 12186:

i •

2.634_ CF• 8.7718) 71t 1-....MEAN =316.2 (/) ｾ＠ 6 z lo.I er It:'.

a

s

0 0 ｾ＠ 0

41

w ｾ＠ 1-z 3 lo.I 0 a: w Q. 0 MEAN :I: 2cr (LOG NORMAL) M ± 4 er ( LINEAR ANALYSIS )

FIG.

t

5000 10000

EXCEEOANCES PER 104 HOURS

15000

TO 0.6%

U> w u z <t 0 w 1.1.J (.) X w

1.oL - - - --

---+--____;~-COMPUTER FrLE '--. CLEAN DATA ONLY

ALL AIRCRAn

CTO OCT. 1078)

{AR ITHMETIC METHOD)

FILE

o.001L l f ,

-0.0001

L-_

..1.1.-₀-...L.---L₀-...JL----:-1.~o:---...J---::: 2:L;.0 ~--1-~3_'no:----'--'""".4°t_'no-g LEVEL

FIG . 2

a: : ) 0 :I: a:: w Q. U) Lu (.) z <{ 0 I.I.I w (.) X L&J

FUOO LOAD SPECTRllt

L06--t«INL ANALYSIS

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All.

DATA TO

ref .

1978

DELETINS:

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- ALL IIENn'S

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COMPUTER FILE - - - / \ - - - COMPUTER F ILE

0.1 (ARITHMETIC METHOD) ---T"-+----+----~...--+-~ (ARI THMETIC METHOD)

'

0.01

'

I I I I I I LOG NORMAL ANALYSIS

'

\ \ \

'

\ I O.OOl 1 1 - - - ~ 1 - - - + - - L - E G _ E _ N _ D - - - \ + --/

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+ 2Q"' MEAN - 2 CT ( L-N) 0.0001..._ _ _ _ _._ _ _ _ _.. _ _ _ _ ..,.._ _ _ _ ... _ _ _ _ ..._ _ _ _ -+-- 1.0 0 . 1.0 2.0 3.0 4.0

fIG. 3

g LEVEL

a: ::> 0 r a: w 0. V) w L) z <t 0 w w L) X w 1.0 0.1 0 .01

TRACKER

fUQtT

LOAD SPECTRllt

SAIA£:

R£C(IIE)

DATA TO OCT. 1878

LESS

:t

2cr

YALlES AT

LEVflS

8.5, 1.5, 2.8, 2.S

AN>

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AIW.YSIS)

8878.2

Im.

I I I I I I \

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DATA FROM ORIGINAL

REGISTER SETTINGS

\

( SAME METHOD OF ANALYSIS) \ \ \ \ \

'

I 0.001 + + + + t f -I _LEGEND I

₊

_{2 O"} I HIGHEST A/C __ l___ MEAN (ALL) LOWEST A/C - 2o-0 1.0 2.0 0.0001 - - - -_-1•.0- - - - . . . _ _ _ _ ..., _ _ _ _ 3.0 4.0 g LEVEL

FIG. 4

0 ;I: :r. ;;: c;: 2 <( ,... .•. - :£ C )< r.i

Hrs. Computer ri' ile

To Oct/78 15815.7 Computer File 14841. 2 To 1 March/78 To Mar.178 Reject b y ±3a _{11547. 6} To Oct/78

ReJ ect by ±4o _11356.3

Tc Oct/78 (7(.. fSiH,q. ｾ＠

"CLEAN DATA ONLY" 1110 1 . 5

_ALL 1974 DATA _{1672 . 9}

197 4 DATA

(De l eting 33,2 hrs . on 12195) 1 639 , 6 CLEP.N DATA ONLY

WI Tn ALL 4g's DELETED 10731.3

ALL DATA AT HIGHER

REGI STER SETTINGS 4480.8

DITTO - BUT

EXCLUDI NG 91 HRS. ON _{43 e9 .8}

A/C 1 2195 SAMPLE USED FOR

L::>g::-Normal At1alysis 3 UT 52 55 ,8 ARITH . MEANS ARITH MEANS OF 8879,2 HR. SAMPLE _{8879. 2} DI TTO BUT WI TH EXCLUSIONS@ 3,5g LEVEL RESTORED 9527 ,9 , , tlMMt\11¥ Q1;1

Mr•:Mi E XCE:EU/W(.!li..J flili 110 Ult

BY "g" LEVEL (ARITH~~ETIC MEANS) -0.5 0 0.5 1. 5 .00051 . 0233 9 . 26145 2.97458 .0005 4 . 02480 . 2733 6 3.01013 .000 17 _{. 00528 . 12444 2.51489} . 0001?6 .00537 . 14098 2.7030 Ii 'QO J-1 ., i o;

A·H?

0 . 00387 .09512 2. 1_{rn2 55} 0 . 00299 . 1 3091 2 . 7981 3 0 . 00183 . 12014 2.64561 0 . 00382 . 09 496 2 . 521 50 0 . 00134

-

-0 .00137

-

-0 .00571 . 15393 2 . 62643 0 .00360 . 12997 2.66206 0 . 00 420 ,131 82 2 . 63941

'l

3.0 2.0 2.5 3. '.> 4 . 0 , 33612 .14739 . 03 098 .008!Jl , 344 85 . 15 497 .03302 . 00896 .20498 .04997 .00580 .00087 .23194 . 05750 . 00616

. ooos·a

. 1q,-Lf$ _·6~11?~ · bO '-f(. 1.. _{q)t, 01 i} . 1948 4 . 04333 .00378 . 00027 .207 42 . 04663 . 00418 0 .18662 .03415 . 00183 0 , 19709 .04240 .00298 0 . 00 625 .13011 . 0281 2 .00223 0 . 00

~no

.12119 .02232 . 00091 0 . . .23346 .06089 . 006 28 .0 0076 .21984 .04032 . 00259 0

-.2 221 9 .04 545 . 00 430 .00 052

-BY "g" LEVEL LOG-NORMAL DETERMINATION 3 . 0 FLYING -0.5 0 0.5 1. 5 2 . 0 2.5 3.5 4. 0 HRS. Sample: Exclude all

Circled Data 5255.8 0 .00493 .01 qo2 2 . 34885 . 18961 .03261 .00682 . 00072 Exclude All Periods

of< 75 Hrs. DITTO

But Delete All 4679.6 0 .0 0389 .06726 2 . 38127 . 18879 .03018 . 00463 0 4g + Assoc. Data File To Oct 1978 Dele te by± 2o at 8879.2 0 .00430 . 06767 2 . 62498 .17508 .02965 .0 0553 0 0, • 5, 1. 5, 2. 0, 2 . 5 or 3 . 5g I .A.W. 4679.6 Hr . Stats. DITTO Except Retain 3,5g 9527,9 0 . 00479 .0 6934 2.61003 .17584 .03088 .00643 0 Level Deletions

ALL DATA AT OR.IGINAL . 00' 14

REGISTER SETTINGS 3586.1 .0 0262

-

-

-

.13229 .01676 . 00135 0

DELETE ± 2o ｾ＠ 2.0 · + 2 . 5g LEVELS + ASSOC. DATA SAMPLE AS IN 8879,2

HRS. (ABOVE) BUT ONLY 7023 . 8 0 .00332 .06043 2. 73571 .17539 .025 23 .00528 0 A/C HAVING 1000 HRS+ OF

CLEAN DATA ( ±2o)

MEANS

AIRCRAFT F LY ING g LEVEL

HRS. -0.5 0 . 5 1. 5 2 .0 2.5 3,5 4.0 12148 1322 . 6

-

-

.05111 1. 8 0191 _{.154 23} .02187

-

-12167 40 2. 3

-

-

.02560 2. 13855 .11980 .03972

-

-12170 576, 8

-

.01052 .18215 2.27778 .19754 .05401 .00697

-12173 593,3

-

.00727 .16248 2 .31 435 .16929 .03468

-

-12197 283.0

-

.06534 2.24438 . 25313 . 08400

-

-12189 2014.5

-

. 00587 . 06987 3.65732 . 18258 .02420 . 00275

-12195 2284 . 3 . 00169 .051 33 2 . 94413 .17382 . 02787 .00701

-12188 1402.4

-

. 00166 .07492 2.48409 . 18521 .02526 .00550

-ALL 8879 . 2

_-

. 00430 .0676 7 2.62498 . 17508 .02965 . 00553

-STANDARD DEVIATIONS 12148 1322. 6

_-

_-

.38217 . 13141 .29792 . 45280

-

-12167 402. 3

-

_-

.52228 . 27722 .35844 ,39638

-

-12170 576 . 8

-

.2 4461 .65782 . 18763 .22144 ,37596 . 36031

-12173 593 . 3

-

.81742 ,45203 .17649 .229 02 .22913

_-

-12197 283 . 0

_-

_-

.55752 ,32189 . 31810 .40632

-

-12189 2014.5

-

,52625 ,35860 .11 201 .28553 .45917 .9 273 0

-12195 228 4. 3

_-

.22003 .40113 .17 275 .30650 .29770 .3 7946

-12188 lll02. 4 .34798 .ll 1808 . 18078 ,34 22 4 .41434 , 43239

-ALL 8879.2 . 51262 _{.44857 . 19620 . 30176 . 39841 . 45013} Log ~MEAN} 12148 1322.6

-

-

-1 .2915 . 25573 -0. 8118 -1. 6602

-

-12167 402.3

-

-

-1.5918 , 33012 -0.9216 - 1. 4010 -

-12170 576.8

-

-1. 9778 -0.7 396 , 3575 - 0 . 7043 -1.2675 - 2 . 1565

-12173 593.3

-

- 2.1385 - 0,7892 ,364ll3 - 0 . 7714 -1.4 599

-

-l2197 283.0

-

-

-1 .1848 ,35110 -0.5967 -1.0757

-

-12189 2014.5

_-

-2.2316 -1.1557 ,5632 -0. 738 6 - 1.6163 -2.5602

-12195 2284.3

_-

-2.7714 -1. 2896 . 46896 - 0.7599 - 1. 55 49 - 2 . 1543

-12188 1402 . 4

_-

-2 . 7796 -1.1254 ,3952 -0 . 7323 -1.5976 -2 . 2595

-ALL 8879.2 - 2 .36635 - 1.16959 . 41913 - 0.75677 -1. 52795 -2.257 40

Al Bl

HRS. - 0 . 5 0

HIGH FROM TO

[BASED ON MEAN ±2o ( LOG NORMAL }]

cl Dl A2

0 . 5 l . 5 2 .0

FROM TO FROM TO FROM TO

B2 c2 D2

2.5 3 , 5 4 . 0

FROM TO FROM TO HIGH

105- 11 5 1 or More 0 5 l ₅₉ 117 71 3 5 77 1 20 0 5 1 or More 95 -1 05 85 - 95 75- 85 65-75 55-65 45- 55 35-45 25-3 5 15-25 0-15 0 5 1

IJ.t5J~

107 648 4 10 1 19 0 4 0 4 1 48 96 583 4 63 0 17 0 4 0 4 1 43 . 85 518 3 56 0 15 0 4 0 3 1 37 74 454 3 49 0 13 0 3 0 ₃ 1 32 64 389 3 42 0 11 0 ₃ 0 2 0 27 53 324 2 ₃₅ 0 9 0 2 0 2 0 21 43 259 2 28 0 7 0 2 0 1 0 16 32 194 1 21 0 6 0 1 0 1 0 11 21 130 I ! 1 1 4 0 4 0 1 0 0 0 4 8 49 I 0 ₅ 0 2 0 0 EXPLANATORY NOTES:

1. The l imit s us e d to pre pare thi R t a b l e will resu l t in occa sional s~a l l depar ture s f rom the tabulated values under no r ma l ~ondit i ons . ｾｾＭ

2 . The Ai and D2 r egi sters (- 0 . 5 and 4 . 0g ) sho uld normal ly show zero counts for t he f l ying t i mes specif i ed .

3 , Departures from t he tabula t e d va lues in t wo or more columns ( high or l ow} by more than l count (or 10 percent of the t a bulated val ue , if that i s greater) s houl d nor ma ll y j us t ify furt her i nvestigatio n and comme nt in the " Remar ks " block.