! 

A 

NASA Technical Memorandum 86726 

t 

z 

Digital Program for Calculating Static 

Pressure Position Error 

J. Blair Johnson, Terry J. Larson, and Jules M. Ficke 

(EASA-TB-86720) LlGIlAL EECGEM FOM N87-16dil 

CALCULATIW SPAllC PBESSURE ECSlIIC~ dhlHCR 

1 

(KASA) 28 p CSCL 01c 

u IAC la S 

G3/05 44004 

February 1987 

National Aeronautics and 

Space Administration 
NASA Technical Memorandum 86726 

. 

Digital Program for Calculating Static 

Pressure Position Error 

J. Blair Johnson, Terry J. Larson, and Jules M. Ficke 

Ames Research Center, Dryden Flight Research Facility, Edwards, California 

1987 

National Aeronautics and 

Space Administration 

Ames Research Center 

Dryden Flight Research Facility 

Edwards, California 93523- 5000 

.I 
SUMMARY 

e 

c 

A computer program written to calculate the static pressure position error 

of airspeed systems contains five separate methods for determining position error, 

of which the user may select from one to five at a time. The program uses data 

from both the test aircraft and the ground-based radar to calculate the error. In 

addition, some of the methods require rawinsonde data or an atmospheric analysis, 

or both. 

The program output lists the corrections to Mach number, altitude, and static 

pressure that are caused by position error. Reference values such as angle of 

attack, angle of sideslip, indicated Mach number, indicated pressure altitude, 

stagnation pressure, and total temperature are also listed. 

INTRODUCTION 

The measurement of true airspeed and altitude is extremely important when 

flight testing aircraft. To increase the accuracy of these measurements, the 

static pressure position error must be determined, then accounted for. Though 

many methods have been developed and used successfully, the data analysis can be 

tedioiis. To decrease the workload, a computer program (PERROR) was written that 

contains several methods (all incorporating radar measurements) for determining 

static pressure position error for a given air data system. The program accesses 

data from a file that contains ground-based radar and test aircraft information. 

Additionally, atmospheric analysis data are entered in table form if available. 

PERROR then calculates the position error for the system. 

This report describes the methods that are used in the program, the inputs 

necessary for each method, and the limitations of the methods. In addition, the 

output from an actual test is presented. 

NOMENCLATURE 

ALPHANB 

BETANB 

CP 

IIANG 

DESCP 

DESCT 

DHP 

DHPG 

DM 

angle of attack, deg 

angle of sideslip, deg 

pressure coefficient, (PICT - P)/QCIT 

difference between azimuth angle and direction of pressure gradient 

descent pressure method 

descent temperature method 

calculated difference between true and indicated pressure altitude 

difference between geometric and pressure altitude as a function of 

horizontal position 

calculated difference between true and indicated Mach number 

.\ 
DPR 

D I? 

DZ 

DZEN 

D ZES 

DZH 

DZHTARL 

E 

1.' I, I G HT 

G 

GGHTHI, 

GH 

HP 

HPREI.' 

H PT 

h 

I ETSV 

I ET 

I ETA0 

I1 

I SI! 

rsimr) 

2 

calculated difference between true and indicated static pressure 

distance from radar site to aircraft, ft 

constant adjustment to radar altitude (ft) that allows the computed 

pressure altitude at the reference point to equal the calibrated 

pressure altitude; used if KK f 0 and LL f 0 

difference between geometric altitude and indicated pressure altitude 

as a function of elevation angle along a survey run 

difference between geometric altitude and indicated pressure altitude 

at the maximum elevation angle along a survey run 

difference between geometric and pressure altitude as a function of 

geometric altitude 

table of pairs of DZH as a function of altitude; used if KK .f: 0 and 

LL f 0 

radar antenna elevation angle, deg 

f liqh t number 

pressure gradient obtained from atmospheric analysis, ft/n.mi. 

table of triples of G and GH as a function of altitude; used if KK # 0 

and ISURVEY = o 

direction of the pressure gradient (direction of decreasing 2 - HP at 

constant geometric altitude, measured in degrees from true north) b 

true pressure altitude, ft 

reference pressure altitude, ft; used if MM f 0 

test or indicated pressure altitude, ft 

geopotential altitude, ft 

end time (HR, MINI SEC, MSEC) of the survey run; used if ISURVEY f 0 

stop time (HR, MINI SEC, MSEC) 

end time (HR, MIN, SEC, MSEC) of the acceleration-deceleration run 

associated with a survey run; used if ISURVEY f 0 

flag set to nonzero to calculate position error using radar-rawinsonde 

method 

start time (HR, MINI SEC, MSEC) 

start time (HR, MIN, SEC, MSEC) of the acceleration-deceleration run 

associated with a survey run; used if ISURVEY f 0 

. 
ISTSV start time (HR, MINI SEC, MSEC) of the survey run; used if ISURVEY f 0 

ISlJRVEY set to nonzero for a survey run (a survey run is used only when KK f 0) 

IIJNITS set to 0 indicates standard English units for all inputs; set to 1 

indicates pressure units are in lb/in2 and other units are in standard English units; set to 2 indicates pressure is in N/m2 and TT is 

in kelvins 

KK 

1,L 

M 

MI 

r4 M 

NDZH 

NGGH 

NN 

00 

P ICT 

RRA 

flag set to nonzero to calculate position error using level 

acce leration-deceleration method 

leve 1 acce leration-deceleration method 

flag set to nonzero to calculate position error using descent pressure 

method 

Mach number 

indicated Mach number 

fiag set to nonzero to calciilate positioi; errar usin.; descent temperature method 

two times the number of pairs of entries in the DZH table; used if 

KK f o or LL 1: o 

three times the number of triples of entries in the GGH table; used if 

KK f 0 and ISURVEY = 0 

flaq set to nonzero to calculate position error using total temperature 

method 

flag set to 1 to compute PT from WIT and PICT from the merged file; 

set to 2 to compute PT from VCT and HPT from the merged file; default 

of 0 will use PT as it comes from the merged file 

indicated static pressure, lb/ft2 

ambient pressure determined from rawinsonde balloon measurements, lh/ft2 

indicated total pressure , lb/f t2 

indicated impact pressure, lb/ft2 

flag set to nonzero to output pressure coefficient CP; default of 0 

will output pressure altitude correction DHP 

radar parameter identification for azimuth angle, deg 

3 
RRH 

RRTA 

RRX 

RRY 

RUN 

T 

TOT 

TS 

TT 

VCT 

z 

Y 

Suffixes: 

DP 

wr 

L I) 

R 

TT 

radar file parameter identification for geometric altitude, ft above 

sea level 

radar file parameter identification for ambient temperature, OF 

radar file parameter identification for x coordinate, centered at station, positive east, ft 

radar file parameter identification for y coordinate, centered at station, positive north, ft 

run number 

ambient temperature, OF 

total temperature method 

standard temperature, OF 

total or stagnation temperature, OF 

calibrated airspeed, knots 

geometric altitude, ft 

specific heat ratio 

output calculated using the descent pressure method 

output calculated using the descent temperature method 

output calculated using the level acceleration-deceleration method 

output calculated using the radar-rawinsonde method 

output calculated using the total temperature method 

DESCRIPTION OF METHODS 

Leve 1 Acce leration-Deceleration Method 

The level acceleration-deceleration method involves deriving true pressure 

altitude HP from geometric altitude Z and a calculated or measured difference in 

qeometic altitude and pressure altitude, Z - HP. Ideally, the test aircraft flies 

a constant-altitude acceleration-deceleration run to cover the desired Mach range. 

However, if desired, this method can be used €or a climbing or descending maneuver. 

Geometric altitude is obtained from ground-based radar. 

4 
An atmospheric analysis is conducted to determine values of Z - HP, pressure 

altitude gradient G, and ambient temperature T. When the value of 2 - HP is 

subtracted from the radar altitude, true pressure altitude is obtained. The value 

z - HP is referenced vertically, directly above the radar site. The pressure altitude qradient is the slope of the pressure altitude in the horizontal plane and is 

represented in vector form. The magnitude is in geopotential feet per nautical mile 

of horizontal distance and in the direction of decreasing Z - HP. The origin of 

this vector is at the radar site. 

The atmospheric analysis is based on information received from rawinsonde 

soundings. NASA Ames Research Center, Dryden Flight Research Facility (AmesDryden) receives information from the Air weather Service at the Air Force Flight 

Test Center, Edwards AFB. The Air Weather Service gathers data from rawinsonde 

soundings made twice a day at numerous locations. The analysis is made from 

constant-pressure-level maps from which pressure-height, temperature, and wind 

information can be extracted for the flight test runs. In addition, an Edwards 

rawinsonde sounding is generally scheduled by Ames-Dryden to provide data in the 

vicinity of the calibration flight, at approximately the time of the flight. Data 

from this sounding provide more points per unit of altitude than does the other 

sounding information. 

When using the level acceleration-deceleration method, two options are 

available to compensate for the horizontal pressure gradient: the nonsurvey 

option, using an atmospheric analysis, and the survey option, using a constantspeed survey run made along the same path as the acceleration-deceleration. The 

option descriptions follow. 

-- Nonsurvey option. - The nonsurvey option of the level acceleration-deceleration 

method uses both Z - HP and pressure-altitude gradient from the weather analysis. 

At each time interval (typically every second), a value of Z - HP as a function of 

vertical height DZH and a value of Z - HP as a function of horizontal position DHPG ~ 

are calculated. The value of DZH is obtained directly from the weather analysis; 

DHPG is calculated by multiplying the distance to the aircraft from the radar site, 

DR, by the pressure gradient G and the cosine of the difference between the azimuth 

angle and direction of the pressure gradient, DANG: 

DHPG = (DR) (G COS DANG) 

,, n --La."?t<" ab ,,.-,, ef this method is shown in fiqure l(a). True pressure altitude is then 

determined by the equation 

HP = Z - DZH + DHPG - DZ 

where DZ is an adjustment. The variable DZ defaults to zero if there is no 

existing static-pressure position error correction. If a position error is firmly 

established for a specific flight condition, DZ can be used so that the calculated 

pressure altitude at the same flight condition is equal to the known pressure altitude. The previous equation can also be used for the "bootstrap" method where, 

again, the static pressure position error is known at a reference point, but values 

of DZH and DHPG are not used. In such a case, DZ is evaluated at the reference 

point. Finally, in all cases, DZ is applied as a constant throughout the entire 

test run. 

5 
Survey option. -with the survey option, DZH is used to provide a vertical 

component of Z - HP, as in the nonsurvey method. However, a different scheme is 

used to arrive at a horizontal component. During the flight test, a constantMach run is made at the same altitude and over the same path as the accelerationdeceleration run. From the survey run, a correction for pressure gradient error 

and radar error (such as, in elevation angle) can be obtained as a function 

of radar-antenna elevation angle. An initial Value of Z - HPT = DZES is determined at the highest elevation angle, where radar errors are at a minimum. A table 

of z - HPT values (DZEN) as a function of elevation angle is generated from the 

survey run. Then a correction for each point along the acceleration-deceleration 

can be determined from DZEN at the corresponding elevation angle. This method is 

shown schematically in figure 1 (b) . The following equation is used to calculate 

pressure altitude : 

__-- 

HP = Z - DZH - (DZEN - DZES) - DZ 

Radar-Rawinsonde Method 

The radar-rawinsonde method determines true Mach number directly. Adiabatic 

equations relating Mach number to stagnation and static pressure are used: 

M = [~(PT/P)OO~*~~ - 5Ioo5 M 1.0 

M = [(le42851 - 0.357143~ - 0.0625y2 - 0.025~3 - 0.012617~4 

- 0.00715~5 - 0.004358~6 - O.O087725~9)/ylO*5 M > 1.0 

where 

y = 1.839371/(PT/P) 

The supersonic equation accounts for the total pressure loss across a normal shock 

wave. The approximation is given in appendix A. It is assumed in the equations 

that there.is no position error in the measured stagnation pressure. The static 

pressure as a function of geometric altitude is obtained from the rawinsonde 

listing €or the flight test. 

Descent Pressure Method 

The descent pressure method, which can also be used for climbs, is similar to 

the level acceleration-deceleration method in that it calculates true pressure 

altitude by subtracting Z - HP from radar altitude. However, with this method the 

test aircraft is flown in a descent or ascent, as opposed to level flight, and no 

corrections are made for horizontal variations in the atmosphere. 

As in other methods, Z - HP is obtained from an atmospheric analysis, and DZ 

can be iised to obtain the correct pressure altitude at a reference point in the run 

for which the static-pressure position error is known. As previously described, 

this correction is then applied throughout the rest of the run. 

HP = 2 - DZH - DZ 

6 

8 
Descent Temperature Method 

The descent temperature method, which can also be used for climbs, calculates 

true pressure altitude from stagnation temperature, indicated Mach number, and 

radar altitude. The difference between true and indicated pressure altitude then 

determines the correction for static-pressure position error. 

Procedurally, the calculation begins at a reference point (either the first or 

last point of the run) for which the true pressure altitude HPREF is required. 

The departure of the radar altitude from the reference altitude is divided into 

increments, each being converted to a pressure-altitude increment by the following 

method. First , the geometric altitude increments are converted to geopotential 

altitude by using the approximation 

Ah IT (20,825,000 Az)/(20,825,000 + z) ft 

The resulting geopotential increment is converted to the associated pressurealtitude increment by the equation 

AHP = TS/T Ah 

In this equation the temperatures are caicuiated by averaging the tem_peratures at 

the end points of the altitude increments. The standard temperature TS is calculated as a function of geopotential altitude. The ambient temperature T is determined from the approximation 

T = TT/(l + 0.2M2) 

Iteration is required in this equation since Mach number is used. Indicated 

Mach number is first used to obtain TI from which position error (and hence a new 

Mach number) is calculated. This new Mach number is used in the preceding equation for another iterative cycle. Convergence on true Mach number occurs rapidly. 

After the geometric altitude increments have been converted to pressurealtitude increments, they are summed to determine position error correction €or the 

te s t poi n t : 

Y 

HP HPREF + C (AHP)j - HPT 

j =O 

where y is the number of altitude increments and the sum of the first two terms on 

the right-hand side of the equation is the true pressure altitude. 

Total Temperature Method 

The total temperature method solves for Mach number from the equation 

TT = T(l + 0.2M2) 

7 
The specific heat ratio is assumed to be 1.4. The stagnation temperature TT is 

measured onboard the test aircraft, and the ambient temperature T is obtained from 

the atmospheric analysis, or directly from the rawinsonde. 

I 

Radar Data 

The correction for Mach number determined by this method is for total pitotstatic position error, not just the correction for the static-pressure position error. 

METHOD LIMITATIONS 

General Limitations 

This program has several limitations. No data smoothing is done nor does the 

program seek and discard wild points. There are no provisions to compensate for 

pneumatic lag of the airspeed system. In addition, there are no corrections to the 

position error for real gas effects. One safeguard, however, is that if the value 

PT < P, calculations for that point are terminated. 

4 

The radar data used by Ames-Dryden are obtained from an FPS-16 radar system. 

Following a series of flight experiments, it was determined that the radar data may 

be questionable when the radar antenna elevation angle is below 7O. This is due in 

part to the large uncertainty of the refraction correction that exists at the low 

elevation angles. However, radar data from the lower elevation angles may be used 

if the survey option is exercised because the option will account for systematic 

radar errors. In addition, loss of beacon track will give unusable radar data. 

Level Acceleration-Deceleration 

When using the level acceleration-deceleration method with the nonsurvey 

option, the results are very dependent on the accuracy of the atmospheric analysis. 

Temperature Descent Method 

When exercising the temperature descent option, the altitude intervals should 

be less than 100 ft to adequately approximate the ambient temperature. 

PROGRAM USE 

General Description 

To implement the program the user must first create a merged file of the necessary aircraft and radar data. All other necessary inputs are contained on a single 

data card that must be submitted with PERROR. The program then reads the data for 

the specified time interval, and unit conversions of inputs to the standard English 

8 
system are made if required. If total pressure PT is not available directly, it 

is calculated from either impact pressure QCIT and static pressure PICT or velocity VCT and pressure altitude HPT. The output format for the flight conditions 

are then written. 

At this point the corrections for position error are calculated, using any or 

all of the five methods, but usually no more than three. Each method uses common 

subroutines for calculating Mach number, pressure altitude (1962 Standard 

Atmosphere), and static pressure, for example. The main program calculates and 

writes the corrections for Mach number DM, static pressure DPR, and pressure altitude DHP caused by position error for each method used. After the calculations are 

performed for one time point using all methods selected, the program completes the 

appendix B. 

* calculations for the next time point. A listing of the program is presented in 

Program Inputs 

A block diagram of the input sources to PERROR is shown in figure 2. In addition, table 1 lists the necessary input parameters for a particular method. First, 

a flight data base file and a radar data file are created. Rawinsonde data may be 

included when creating the radar data file. The data card required to run PERROR 

must contain the following quantities: FLIGHT, RUN, IUNITS, 00, and QQ. Zero is 

the default value for the last four quantities. The indices 11, KK, LL, MM, and NN 

are used to designate which position error methods are to be used (refer to the 

NOMENCLATURE section). 

The following is an example of a data card used when running PERROR (the DZH 

and GGH tables given in table 2 are included in the data card below). 

Program Output 

A sample page of output is shown in figure 3. For this particular case, the 

level acceleration-deceleration method with the nonsurvey option was used. For 

each time point, angle of attack, angle of sideslip, indicated Mach number, indicated pressure altitude, stagnation pressure, and total temperature are listed, in 

addition to the corrections to Mach number, altitude, and static pressure due to 

position error. The corrections are labeled DM , DHP , and DPR , respectively. 

The last letter of each parameter specifies the<ethod-&ed to caGulate the position error. If QQ = 0, appropriate headings for CP output are made. Any other 

integer for QQ results in appropriate headings for DHP output. 

9 
Conclusions 

The computer program presented calculates static pressure position error of 

airspeed systems. The program contains five separate methods for determining position error, of which the user may select from one to all five at a time. All the 

methods require an input data file consisting of aircraft and radar parameters. In 

addition, most of the methods require rawindsonde data or an atmospheric analysis, 

or both. 

National Aeronautics and Space Administration 

Ames Research Center 

Dr yden Flight Research Facility 

Edwards, California, Jan. 9, 1984 

c 
APPENDIX A - SUPERSONIC MACH NUMBER EQUATION 

The following derivation for calculating supersonic Mach number (PT/P > 1.893) 

was developed by Raymond Jackson of NASA Ames Research Center, Dryden Flight 

Research Facility. 

(1 +. y)2#2 l’(y-l) 

- 1 (eq. 3-26, ref. 1) 1 WIT --M2[ 1 +Y 

P 2 4YM2 - 2(y - 1) 

1+ 

Let 

Y + 1M2 1 l/(Y-l) 

2 Y/(Y-1) y-1 1 y+1 =-[-(+I Y+l Y 

Let 

Then 

K = x(l - x)l/(Y-l) = x(l - x)5/2 Qc IT 

1 +- 

P 

RFnomi a1 expansion yields 

x4 K I x --x2 5 +-x3 15 -- 

WIT 2 8 16 Y= 

1 +- 

P 

x7 ... -- x5--x6-- 3 

128 256 1004 

and reversion of series gives 

x = y + 2.5~2 + 10.625~3 + 55~4 + 316.05469~5 

+ 1938~6 + 12421.919~7 

11 
Let 

- 0.02522 - 0.012617187~3 - 0.00715~4 

- 0.004345752~5 - 0.008772528 

The last term of this equation was added empirically so that the equation is exact 

at Mach 1. The effect of the empirical term is null at high Mach numbers. 

M = [(le428572 - 0.35714282 - 0.0625z2 - 0.02523 

- 0.01216172~4 - 0.00715~5 - 0.0043458~6 

- 0.0087725~~ 1 /zI '2 

where z = 1.839371(P/PT). 

12 

L ___ ~ ~~ ~~ - 

z = 1oy = lo( 0.1839371 ) - 1.83971 

WIT 1 +- 1 +- P 

I Then I 

x = 0.12 + 0.02522 + 0.010625~3 + 0.005524 

+ 0.003160546825 + 0.001938~6 + 0.0012421919~7 

1 

-=-- lo 2.5 - 0.43752 - 0.17522 - 0.08832031523 

xz 

- 0.05005~~ - 0.03042026525 

1*4285714 - 0.35714286 - 0.06252 1 M2 =-- 7x - Z 
APPENDIX 8 --ERROR LISTING 

The following is a complete listing of the PERROR program. It is written in 

FORTRAN 77 and is run on an ELXSI computer at NASA Ames-Dryden. 

13 
PROGRAM PERROR 

C 

C 

C 

C 

C 

C 

I 

TH IS PROGRAM CALCULATES POS IT ION ERRORS US I NG ME OPT IONS 

OF SEVERAL DIFFERENT MlHB 

DIMENS ION DZHTABL(40) ,GGHTABL(GO) 

DIMENSION EMINMAX( lO),EAPPROX( lO),ZtF'DIF( lo), 

INTEGER FLIWT, RUN, 00, W 

DIMENSION IT(4) 

DATA L I NE /6/ 

NAMELIST /pRW I I, KK, LL, )rM, NN, 00, W, IUNTS, "REF, 

*FLIGHT, RUN, DZ, HIZH. OZHTABL. NGW. GGHTABL, ISURVEY, 

'ISTSV, IETSV, ISTAD, IETAD 

*DZ, ISURVEY /14*0/ 

- ISTSV(4), IETSV(4). ISTAO(4). IETAD(4) 

DATA I I, KK, LL, M, NN, 00, W, IUNTS, "REF, FLIWT, RUN, 

L I NE=O 

WEN (UN IT=3,F I LE='perrorcut' ) 

OPEN (UN IT=4, F ILE=' f nnerge' ,FORM= 'UNFORMATTED ' ) 

OPEN (UNIT=l ,F ILE='perrorin') 

READ NAMLIST CARDS. SOME OF WlCH ARE OPTIONAL OEPENIING ON MEMOOS USED 

READ(1,PROG) 

IF A SURVEY RUN IS BE I NG PROCESSED, READ FL IDAB-RADAR DATA WR IM; WVEY, 

CREATE DZEN TABLE, AH) CALWLATE DZES. 

IF(IStlRVEY.EP.0) GO TO 7 

MSTSV = 3600000*ISTSV(l) t 60000.ISTSV(2) t 1000*ISTSV(3) t 

MTSV = 3600000*IETSV(l) t WlETSV(2) t lOWlETSV(3) t 

MSTAD = 3600000'ISTAD(l) t 60000*ISTAD(2) t lOWISTAo(3) t 

MTAD = 3600000.IETAD(l) t 60000.IETAD(2) t 1000*IETAD(3) t 

EMINMAX(1) = 1.OE10 

EMINMAX(10) = -1.OE10 

- ISTSV(4) 

- IETSV(4) 

- ISTAD(4) 

- IETAD(4) 

30 READ(4,EH)-31) TIM,Z,R,E,T,MA,PR, 

- VCT,WT,A,B,PT,P ICT,PCIT,TT,FPA,FPH 

E=E/57.3 

RRA-RW57.3 

X=R*COS(E)S I N(RRA) 

Y=R*COS(E)*COS(RRA) 

IDTTL=T IME81000. 

IF(IDTTL.LT.MSTSV) GO TO 30 

IF( t0TTL.GT.MTSV) GO TO 31 

IF(E.LT.EMIW(1)) EMIW(l)=E 

IF( E .GT .EM I W( 10)) EM IW( 1O)f 

GO TO 30 

31 DO 32 1=2,9 

32 CONTINUE 

REWIH) 4 

Do 33 1-1.10 

EAPPROX(1) = 1.OE10 

ZtF'DIF(I) = 0.0 

EMINWX( I) = EMIW(1) t (I-l)*((EMI~(lO)-EMINWX(1))/9.0) 

33 rnlM 

34 READ(4,ENkS) TlM,Z,R,E,T,RRA,PR. 

- VCT ,tPT , A.B ,PT .P I CT .PC I T,TT, FPA, FPH 

E-E/57.3 

14 
RRASU(M57.3 

X=R*COS(E)*S IN(RRA) 

Y=Rm(E)m(RRA) 

lOTTL=T lK*1000. 

IF( IDTTL .LT.MSTSV) GO TO 34 

IF(IDTTL.GT.MTSV) GO TO 36 

w 35 1=1,10 

IF(ABS(E-EMIW(I)).GT.ABS(EAPPROX(I)-EMINMAX(I))) GO TO 35 

EAPPROX( I) = E 

ZW)IF( I) = ZSPT 

35 CONT I MIE 

GO TO 34 

36 OZES = ZtPDIF(10) 

REWIH) 4 

Do 37 1=1,10 

WlTE(3.101) EMIW( I),EAPPROX(I).ZtPDIF( I) 

101 FORMAT (1H ,812.5) 

37 CONTINUE 

C CALL SUBROUTINE TO MITE TOP OF PAGE HEADlKjS n L 

7 CALL HEAO(FLIGHT,RUN) ***** C READ FL IDAB AH) RADAR DATA FROM MRGEO DATA BASE. 

10 READ(4.EHti99) TIM,Z,R,E.T,RRA,PR, 

-VCT ,WT .A,B ,PT ,P ICT ,aC IT ,TT ,FPA,FPH 

E=E/57.3 

RRA-RRM57.3 

X=R*COS(E)*S IN(RRA) 

Y=R*COS(E)m(RRA) 

I OTTL-T I ME.1 OOO. 

IF(ISIRVEY.NE.0 .AH). 1OTTL.LT.MSTAD) GO TO 10 

IF(ISURVEY.NE.0 .AH). IOTTL.GT.META0) GO TO 99 

IF(KK.EP.0 .AH). LL.EP.0) GO TO 6 

IF(Z.LE .DZHTABL(l)) DZt!=DZHTABL(2) 

IF(Z.GE.OZHTABL(NlZH-1)) DZ"TbBL(H1ZH) 

IF(Z.LE.DZHTABL(1) .OR. Z.GE.OZHTABL(NIZH-1)) GO TO 3 

MI 1 1=3,HlZH,2 

IF(Z.LT.OZHTABL(1)) GO TO 2 

C ***** OBTAIN OM FRLM TABLE OMTABL. 

1 CONTIWE 

2 RATIO = (Z-DMTABL( I-2))/(0MTABL( I)-DZHTABL( 1-2)) 

OM OMTABL( 1-1) t RATIO*(OZHTABL( I+l)-DMTABL( 1-1)) 

IF(KK.EP.0) GO TO 6 

IF(IWVEY.NE.0) GO TO 8 n ****) --. *.. .. -,.-. -.-. c --.-. L miAin b Mi VI rmm imLt unim. 

3 IF(Z.LE.GGHTABL(1)) GGMTABL(2) 

IF(Z.LE.GGHTABL(1)) GIMUiTABL(3) 

IF( Z .GE . GGHTABL (tGUi-2)) GGGHIABL( W1) 

IF(Z.GE.GGttTABL(NXH-2)) Gt!&XTABL(NGGH) 

IF(Z.LE.GUiTABL(1) .OR. Z.GE.GMIABL(NGM-2)) THEN 

W6080.0 

GO TO 6 

ENIIF 

IF(Z.LT.GGHIABL(1)) GO TO 5 

m 4 I=~.NGI~,~ 

4 CoHllNJE 

5 RATIO = (Z-GUiTABL( I-B))/(GGHTABL( I)-G(HTABL( 1-3)) 

G = WML( 1-2) t RATIO*(GGHTABL( Itl)-G[wTABL( 1-2)) 

G = WBJBo.0 

GO TO 6 

[;H * GQHIABL( 1-1) t RATIO*(WiTABL( lt2)-GGHTBL( 1-1)) 

15 
C ***** OBTAIN DZEN FROM TABLES EAPPROX AM ZK'IIIF. 

8 IF( E .LE .EAPPROX( 1 ) ) DZEkZHTI IF( 1 ) 

IF( E .GE . EAPPROX( 10)) DZECm IF( 10) 

IF(E.LE.EAPPROX(1) .OR. E.GE.EAPPROX(10)) GO TO 6 

00 9 I-2,lO 

IF(E.LT.EAPPROX( I)) GO TO 11 

9 CONTINUE 

11 RATIO (E-EAPPROX( I-l))/(EAPPROX( I)-EAPPROX( 1-1)) 

DZEN = zH)DIF( 1-1) t RATIO*(;W)IF( I)-;W)IF( 1-1)) 

C TEST LINE MXINT AM CALL HEAD IF NECESSARY 

C 

6 LINE = LINE t 1 

IF (MD(LINE.6) .Ea. 0) CALL HEAD(FLIGHT,RUN) 

C 

C CALL SUBRWT I NE UN ITS TO MAKE UN IT COWERS IONS TO ENGL ISH UN ITS IF NECESSARY 

C 

IF( lUNTS.EP.0) GO TO 15 

CALL UNITS (IUNTS,PT,PICT,PCIT,TT) 

C 

C CALCULATE PT IF PClT AH) PlCT OR VCT AH) WT ARE USED AS IWTS 

C 

15 IF(OO.EP.0) GO TO 20 

lF(OO.EP.2) GO TO 17 

16 PT=dXITtPICT 

GO TO 20 

17 CALL PCC(VCT,PCIT) 

CALL PRES(W1 ,P ICT) 

GO TO 16 

C CALCULATIONS OF INIICATED MACH No AH) INIICATED PRESSLRE ALTIWE 

C 

20 IF(PT.LT.PICT) GO TO 10 

PRAT I9T/P I CT 

IF(OO.NE.O.AM.W.EP.0) Go TO 21 

aC lT=PT-P I CT 

CALL tF'C (PICT,WI) 

21 CALL MACH(PRATI.AMI) 

C 

C MITE HEADING FOR FLIGHT COH)ITIONS, RITE COH)ITIONS AM HEADING FOR 

C POSITION ERRORS 

C 

WRITE (3.901) 

CALL SECTOT(TIY, IT) 

WR ITE( 3,902) IT, A,B. AM I ,If' I ,PT ,ll 

IF(W.H.0) GO TO 23 

RITE (3,903) 

GO TO 24 

23 WRITE (3.916) 

C 

C POSITION ERRDR CALCUATION USING RADAR-RAWIm MEMOD 

C 

24 IF (II.EP.0) GO TO 40 

P=PR 

PRATST/PR 

CALL MACH (PRAT.AM) 

CALL PECALC(P.P 1CT.K IT ,If',tP I .AM,AMI ,Dw,OPR,W.B. W 

IF(PP.NE.0) Go TO 25 

RITE (3.904)oM.opR,W 

Go TO 40 

25 RITE (3,910) Dw,OPR.cP 

16 
C 

C POSITION ERROR CALCULATION USING LEVEL DECEL MTHOO 

C 

40 IF(KK.EP.0) GO TO 50 

IF( ISUIVEY .EP.O) CALL LEvrxcS(aM.G,~.Wp,P,PT.Z,ozH.X,Y .RRA,DZ) 

I F( I SURVEY. NE. 0) CALL LEWS( AM, W ,P .PT .Z .OZH ,OZ ,OZEN,OZES) 

CALL PECALC(P.PICT,CC lT,W,W I ,AM,AMI ,M(,OPR,W.CP,W) 

IF(PQ.NE.0) GO TO 41 

W I TE (3,906)OM ,opR . 0" 

GO TO 50 

41 RITE (3,912) 0M,opR,CP 

C 

C WSlTlON ERROR CALCULATION USING MSCENT PRESSlRE KTHOO 

50 IF(LL.EP.0) GO TO 60 

CALL DEsCp(DZ,Z,OZH,P,PT,aM,W) 

CALL PECALC(P.P ICT ,pC 1T.W.W I .AM.aMI ,DM,OPR.W,CP,W) 

IF(W.NE.0) GO TO 51 

WlTE(3,907) 0M.OPR.W 

4 

GO TO m 

51 WITE(3.913) OM.DpR,CP 

C 

C POSITION ERROR CALCULATION USING DESCENT TEWERATURE METrmo 

60 IF(W.EP.0) GO TO 70 

CALL DESCT(Z .tPREF ,M( I .Ti .PT ,E .AS ,'WS j 

CALL PECALC(PS,P ICT.9C IT,H5.WI ,AL(s.AMI ,OM,OPR.W.CP.W) 

IF(W.NE.0) GO TO 61 

MITE (3,908)MA.OPR.W 

GO TO 70 

61 MITE (3,914) CM.DPR.CP 

C 

C POSITITION EWWR CALCUATION USING TOTAL TEWEFUWE YTHOD 

C 

70 IF (NN.EP.0) GO TO 10 

CALL TOT( TT .T .P .PT ,AM) 

CALL PECALC(P.P ICT.9C IT,W,W I .aM.AMI ,OM,OPR,W.B.W) 

IF(W.E.0) GO TO 71 

MITE (3.909)0M,OPR,W 

GO TO 98 

71 RITE (3.915) 0M.OPR.W 

98 GO TO 10 

99 cLOsEI1) 

cLosE(3) 

cLOsE(4) 

SMP 

C 

C FORMAT STATEEHTS 

C 

901 FORMAT( 1X,/,T3, 'TIE(tR,YIN,SEC)' ,T25, 'ALPHA,OEG' .T45, 'BETA, DEG' , 

.T63,'IH) UACH W',T79,'IH) PRESSUIE ALT',TS,'STAG PRESSUIE'.T121, 

*'TOT W'/T85, 'FEET' ,T104, 'PSFA' ,T122, 'EG, R'/) 

902 FORMAT(lX,T7,3( 12.1X). 13.T28J5.1 ,T47,F5.11 

*T67,F5.3.T85.F6.O,Tl~,F6. 1 ,TlZ,FB. l//) 

903 FORMAT (lX.T12,'OY(',T18,'0PRP',T25,'aPR'.T32,'OKD',T38,'OPRLO', 

- T45, 'WID' ,TS, 'CW' ,T58, 'WW' ,TS, 'I)pop' ,T72, 'OYIT' , - ~8,'OPWIT',T85,'MPDT',T92.'~',T98,'OPRTT',T105,'aPTT'/) 

904 FWT (lX,TlO,F6.4,Tl6,F6.3.TB,F7.0) 

906 FOWUT ( 't ' ,T31 ,F6.4,T37.F6.3,T44,F7.0) 

907 FORMAT ( 't' ,T51 ,F6.4.T57.FS.3.Ts4.F7.0) 

17 
C 

C 

C 

C 

C 

C 

C 

C 

C 

C 

C 

C 

C 

C 

C 

C 

908 FORMAT ( ’t‘ ,171 .F6.4,Tn,F6.3,Ts4.F7.0) 

909 FORMAT ( ‘t’ ,191 ,F6.4.T97.F6.3.T104,F7.0) 

910 FWT (lX,TlO,F6.4,Tl7,F6.3,124,F6.4) 

912 FORMAT ( ‘t’ ,130,F6.4,137,F6.3,144,F6.4) 

913 FORMAT ( ‘t’ ,T50,F6.4,157,F6.3,T64,F6.4) 

914 FORMAT (’t’ ,170,F6.4,179,F6.3,184,F6.4) 

915 FORMAT (‘t‘ ,T90,F6.4.T97.F6.3.Tl04,F6.4) 

916 FORMAT (lX,T12,’~’.T18,’DPRR‘.T26,’CPR‘.T32,‘~0’,T38,‘DPRLD‘, 

- T46,’CPLD’,T52,’oW”,T58, ‘WRIP’,T66,‘CPDP’,T72,’DM)T‘, 

- T78,’OPRDT‘ .T86.’CWT’ ,T92. ’WIT‘ .T98.‘OPRTT‘ ,T106,’CPTT’/) 

EH] 

SUBROUTINE SECTOT(t Ime, It ) 

THIS SuBROUTINE CONVERTS A SINGLE REAL TIM rmW, REPRESENTING 

TOTAL SECOMB TO A 4 mwU, INTEGER ARRAY REPRESENTING 

hr,nln,sec,nsec 

real mln,nsec 

Integer lt(3) 

hr=t Im/3600. 

It( 1 )4r 

m In4 I me/60. 

It (2)4 In- I t( 1)*60 

mseot lne*1000. 

lt(4)--lt(3)*100(Flt(2)*6.&t-It(l)*3.6e06 

return 

end 

SuBROuTINE HEAD(FLIGHT.RUN) 

THIS SUBROUllME MITES MAIN HEADINGS AT THE TOP OF EAUi PAGE 

WITE(3,lM))FL IMI,RuN 

W ‘,l3,‘ RUN ‘,l2,///) 

100 FORMAT(lHl.T36.’STATIC PRESSLRE WSlTlON ERROR CORRECTIONS FOR FLI 

RETLRN 

EH) 

SlsROUTIM UNITS( IUNTS,PT,PICT,OCIT,TT) 

C 

C 

C 

C 

THIS !URoIITINE CONVERTS PARAMETERS IN METRIC UNITS TO EMILISH UNITS 

IF( IUNTS.EP.2) Go TO 5 

PT=144. ‘PT 

P ICT-144. ‘P IC1 

OC I T-144. VC I T 

Go TO 10 

5 PT=.020885’PT 

P ICT-. Mo885.p I CT 

QC IT- .020885.QC IT 

TT 1.8*(ll-458.67)t273.16 

10 REW 

18 
ENI 

SUBROUT I NE PECALC (P.P 1CT.N IT ,F,W I ,AM.AM I ,DM,DpR,DH?,Cp,W) 

C 

C 

C 

C SBROUTINES 

THIS SBRWTINE CALCULATES POSITION ERRORS WN TO ALL OF THE 

m- (P-PICT)/P 

WAM-AM I 

IF (Pq.NE.0) GO TO 5 

CALL Hpc(P,tP) 

W=HJ-tPI 

GO TO 10 

5 CP=(P-PICT)/WIT 

10 RETLRN 

ENI h 

SUBROUTINE W (PRAT.AM) 

C 

C TH IS SUBROUT INE CALCULATES MACH MER AS A FUNCT ION OF PRESSURE RAT IO 

C 

IF (PRAT.GT.1.89293) GO TO 5 

-T( 5*( (PRAT )** .2857- 1 . ) ) 

GO TO 10 

5 Y=l.839371/PRAT 

AWcRT( ( 1.42857-.357143.Y- .0625*(Y**2)- .025*(Y**3)-. 012617*( Y**4) 

*-.~?!s*(r**5)-.~~34~*~~**~~-.~~~*!~**~??,~? 

10 RETUlN 

EH) 

SUBROUTINE PRATIO (AM.PRAT) 

C 

C 

C 

C 

THIS SUBRDuTltE CALCUATES PRESSURE RATIO AS A FUNCTION OF MACH WER 

IF(AM.LT.1.) GO TO 5 

PRATtl .PW*P( ( (5.76.Wm2)/( 5.8.W.2- .8))**2.5) 

GO TO 10 

5 PRAT=(l .t.PAM.*2)**3.5 

10 RETUlN 

EH) 

SlmIJTINE Hpc(P.F) 

C 

C 

C 

C PRESSLRE 

MIS SUBROURIME CAlCUATES PRESSURE ALTlTUOE AS A FUNCTION OF STATIC 

IF(P.LT.II~.S) rio io 5 

IF(P.LT.472.68) GO TO 10 

GO TO 15 

GO TO 15 

GO TO 15 

15 RETLRN 

EH) 

SUBRDuTlNE PRES (W,PS) 

W=-145442.*((P/2116.Z?)**. 190262-1.) 

5 W=65616.8t710794.*(( .M)8746T)**(-.M9271)-1.) 

10 W=3608!3.2-208&.7'(ALUoc( .oM1155TJ)) 

C 

C 

C 

C ALTITWE 

THIS SlsROuTlNE CALCUATES STATIC PRESSlRE As A FU(cTI0N of PRESSURE 

IF(W.CT.36089.2) M TO 5 

IF(W.LT.65616.8) GO TO 10 

19 
PS=51.9754*( ( 1 - .0000042204*(W-65616.8))**(-11.3%/M’/~ 

GO TO 15 

GO TO 15 

5 PS2116.22*(1.-.0000068754’tP)**5.2561 

10 &472.68*( 2.71828**(-. 000048C63*( W-36089.24))) 

15 RETURN 

EHI 

SUBROUTINE CCC(VCT,pC) 

C 

C 

C 

C 

THIS SUBROUTINE CALCULATES PC AS A FUNCTION OF VCT 

IF(VCT.GT.661.4) GO TO 5 

X-2116.22*( ( .142857*( .MXXX)32*VCT**2)tl. )**3.5-1) 

Go TO 10 

5 QG .005805*VCT**2*( 5.76/( 5.6-349964 .NCT**2) )**2.52116.22 

10 RETURN 

EHI 

SUBROUT I NE LEVDNS (AM.G.GH,tF’,P,PT ,Z,DM ,X ,Y ,RRA,DZ) 

C 

C 

C 

C 

C 

THIS SUBROUTINE CALCULATES TRUE MACH MMER AH) STATIC PRESSURE 

BY THE LEVEL DECELERATION KTM1D FOR NON-SURVEY TEST. 

DANG = ABS(RRA-GH)/57.3 

DR = SPRT(X**2 t Y**2) 

Uf’G = DR’G.COS(DANG) 

tP = z-0-z 

CALL PRES(W,P) 

PRAT=PT/P 

CALL MACH(PRAT,AM) 

RETURN 

EM 

SUBRollllNE LEVDS(AM,tP,P,PT,Z,DM,DZ,DZEN,DZES) 

C 

C 

THIS SUBROUTINE CALUATES TRUE MACH MMER AH) STATIC PRESSURE 

BY THE LEVEL DECELERATION YW FOR SLRVEY TEST. 

tP = Z-DZH-DZENtDZES-DZ 

CALL PRES (tP,P) 

FRAT = PT/P 

CALL MACH (PRAT,AM) 

RETURN 

ENI 

SUBROUTINE DEsCP(DZ.Z,DZH,P,PT,AM,tP) 

TH IS SUBRollT I NE CALCULATES TRUE MACH MER AH) STAT IC PRESSURE 

BY THE DESCENT STATIC PRESSLRE METHO0 

w = Z-0Z-DD.l 

CALL PRES(tP,P) 

PRAT = PT/P 

CALL W(PRAT,AM) 

RETWIN 

ENI 

SiBROUl I NE TOT(ll, T .P .PT .AM) 

THIS SUBRollllNE CALCULATES MACH MER FROM LfllSUREMENTS of TOTAL 

TEWRATWIE AH] AkBIENT TEWERATUIE 

UeSaRT( 5*(TT-T)/T) 

20 
C 

C 

C 

C 

C 

C 

C 

C 

C 

C 

C 

C 

C 

C 

CALL PRATIO(W,PRAT) 

P=PT/PRAT 

RETURN 

ENI 

SUBROUT I NE DESCT(2 .tFREF, W I ,ll ,PT .P, AMM.H') 

THIS SUBROUTINE CALCULATES TRUE MACH MER AH) STATIC PRESSURE 

BY THE DESCENT TEWERATLRE MMOO 

STATEENT FUNCTION FOR CALCULATING MIENT TEWERATURE 

LOGICAL FIRST 

DATA FIRST/.TRUE./ 

IF(.NOT.FIRST) GO TO 10 

FIRST = .FALSE. 

W-HPREF 

CALL PRES(W,P) 

PRAT=PT/P 

CALL MACH(PRA1.W) 

GO TO 60 

CALCULATION OF TRUE PRESSURE ALTlTl.DE USING ITERATION 

10 OZ=Z-ZJ 

SET COUNTER FOR MER ff ITERATIONS LIMITED TO 10 

N=O 

") 

ZBAR = (ZtZJ)/2. 

TlBAR=(lltTTJ)/2. 

WAM I 

DH-(20825000.412)/(2082~.tZBAR) 

CALUJLATlpN OF AkelENT TEWERATWE AS A FU(CTI0N ff ALTlTUlE 

IF(ZBAR.GT.36089.) GO TO 20 

GO TO 40 

TS-390. 

GO TO 40 

TS-518.7.(1.-.0000068756'ZBAR) 

20 IF(ZBAR.GT.65617.) GO TO 30 

30 TS390.*(1 .t.ooaw)14069.(ZBAR-65617.)) 

40 TA=TTBW(l .O t 0.2dAW82) 

rrP-TSg!!rr 

W* 

CALL PRES(tP,P) 

PRAT-PTA' 

CALL IIUCH(PRAT,AM) 

DM I =&AM: 

WAY 

ttNtl 

IF(N.GT.10) GO TO 60 

GO TO 40 

TTJ-TT 

RETUtN 

EH) 

IF(MS(OMI).LT.O.O) GO TO m 

60 23.2 

21 
,. . 

REFERENCES 

1. Grilcey, William: Measurement of Aircraft Speed and Altitude. NASA RP-1046, 

1980. 

2. Larson, Terry J.; and Ehernberger, L.J.: Techniques Used For Determination of 

Static Source Position Error of a High Altitude Supersonic Airplane. 

NASA TM X-3152, 1974. 
TABLE 1. -NECESSARY METHOD INPUTS TO PERROR 

. 

LEVD 

-- DESCP DESCT TOT RADAR 

survey Nonsurvey 

(ISURVEY = 1 (ISURVEY = 0) 

$PROG card KK = 1 KK = 1 LL=1 MM=1 "=1 II=1 

ISTSV, IETSV DZHTABL DZH HPREF 

ISTAD, IETAD DZ DZ 

DZHTABL NDZH NDZH 

DZ NGGH 

NDZH 

Merged file P P, PT* P P P 

PT* GGHTABL PT* PT* PT* 

z Z, RRX, RRY Z Z TT 

RRA TT 

PR 

PT* 

Z 

Calculated DZEN DANG MI MI MI MI 

DZES DR T 

MI Mi 

*KIT and PICT or HPT and VCT may be substituted. 

TABLE 2. -ATMOSPHERIC ANALYSIS RESULTS 

FOR F-14 FLIGHT 557 

GH, deg 

true north z, 103 ft DZH G, ft/nmi 

46 920 1.9 045 

44 896 

42 866 

40 850 1.4 045 

38 900 

35 91 5 1.2 040 

31 91 5 

25 772 1.1 035 

20 650 0.9 027 

15 450 

11 340 0.5 030 

9 287 

7 240 

5 202 0.0 

surface 175 

--- --- 

--- --- 

--- --- 

--- --- 

--- --- 

--- --- 

--- --- 

--- 

--- --- 

23 
RRX, RRY 

(X, Y) 

b Fllghtpath 

N 

LE 

(a) Nonsurvey method. 

-+ ‘\\I- “PsuNey 

(constant Mach) 

\ 

= survey 

Elevation >\. (constant Mach) 

angle---/ -- --- $\\= radar i 

(b) Survey method. 

Figure 1. Methods used to compensate 

for the horizontal pressure gradient 

when using level accelerationdeceleration. 

base file 

Atmospheric 

analysis 

program 

Figure 2. Block diagram of 

input sources to PERROR. 
1 STATIC PRESSlRE POSITION ElwoR COlWECTlOHS FOR FLIW 178 Ru( 1 

TIM(HR,MIN,SEC) ALPHA.DEG BETA, DEG IH) YACH No IH) PRESSURE ALT STAG PRESSURE TOT TEW 

FEET PSFA DEG, R 

82330 0 6.7 ..... .780 m1. 1035.3 -7.1 

t .0197 -.m 433. 

TIM(HI,MIN,SEC) ALPHA.DEG BETA. DEG IH) YACH No IH) PRESSlRE ALT STAG WSSUIE TOT TEW 

FEET PSFA DEG. R 

82330500 6.7 ..... .780 27851. 1035.3 -7.1 

t .om -.019 430. 

8 23 31 0 6.8 ..... .783 27862. 1037.6 -6.9 

t .01Q3 -.019 428. 

1 IM (H( .MI N .SEC) ALPHAJEG BETA. LEG IH) MACH No IH) PRESSURE ALT STAG PRESSURE TOT TEP 

FEET PSFA DEG. R 

82331500 6.8 n... .783 27862. 1W7.6 -6.9 

t .ow -.m 431 

TIM(M,MIN,SEC) ALPHA,LEG BETA, DEG IH) YACH No IH) PRESSURE UT STAG PRESSURE TOT TEP 

FEET PSFA DEG. R 

02332 0 6.6 n... .786 27873. 1039.6 -6.7 

DYI opRp apR OYD OPRLD apu) OLap OpROp a9op WT opwlT apOT OYrr OPRTT aPll 

t .ow -.019 428. 

Figure 3. Output format of PERROR program. 

25 
1 Report Nn 2. Govlmnmnt Accession No. 

N4!>A TM-86726 

4 Title and Subtitle 

III~;ITAI, PROGRAM FOR CALCULATING STATIC PRESSURE POSITION ERROR 

3. Racipirnt'r Catalog No. 

5. Repon Data 

7 AuthorW 

J. Blair Johnson, Terry J. prson, and Jules M. Ficke 

e Performing Organization Name and Addrw 

NASA Ames Research Center 

Dryden Flight Research Facility 

P.0. ox 273 

8. Performing Orpnization Report No. 

H-1284 

10. Work Unit No. 

RTOP 505-31 -21 

11. Contract or Grant No. 

Edwards, CA 93523-5000 

13. Type of Report and Period Coverd 

I2 Sponsoring Agency Name and Address Technical Memorandum 

National Aeronautics and space Administration 

Washinqton, IX 20546 

14. Sponsoring Agency Code 

I5 Suoplementary Notes 

6 Abstract 

A computer program rrritten to calculate the static pressure 

position error of airspeed systems contains five separate methods 

for determining position error, of which the user my select from one 

to five at a time. The program uses data from both the test aircraft 

and the ground-based radar to calculate the error. In addition, some 

of the methods require rawinsonde data or an atmospheric analysis, 

or both. 

The program output lists the corrections to Mach number, altitude, 

and static pressure that are due to position error. Reference values 

such as angle of attack, angle of sideslip, indicated Mach number, 

indicated pressure altitude, stagnation pressure, and total temperature are also listed. 

I7 Kev Words [Sugyested by Authorbl I 18. Distribution Statement 

static pressure position error 

I:~~~~III ter code 

Unclassified - Unlimited 

Subject category 05 

b 

t 

I 

9 Securaty Clasrlf (of this report1 20. Security Classif. lof this pagel 

flqrlaqsif led Unclassified 26 A0 3 

'For sale by the National Technical Information Service, Springfield, Virginia 22161. 

21. NO. of Pages 22. Rice'