1、rca “ . _- L NASA TECHNICAL NOTE 6827 LOAN COPY: RETUR AFWL (DOUL) KRTLAND No FLIGHT CALIBRATION OF COMPENSATED AND UNCOMPENSATED PITOT-STATIC AIRSPEED PROBES AND APPLICATION OF THE PROBES TO SUPERSONIC CRUISE VEHICLES ,/ , ,I i ,. . by Lunnie D. Webb and Harold P. Washington . . . .:. r . , .,jL. .
2、, . Flight Reseurch Center Edwurds, Gal;$ 93523 NATIONAL AERONAUTICS AND SPACE ADMINISTRATION WASHINGTON, D. C. MAY 1972 1 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-TECH LIBRARY KAFB. NY 1. Report No. 2. Government Accession No. 3. Recipients C
3、atalog No. NASA TN D-6827 4. Title and Subtitle FLIGHT CALIBRATION OF COMPENSATED :OMPENSATED PITOT-STATIC AIRSPEED PROBES AND APPLICATION IF THE PROBES TO SUPERSOMC CRUISE VEHICLES 6. Performing Organization Code 7. Author(s) “ 8. Performing Organization Report No. H-665 .annie D. Webb and Harold P
4、. Washington - 10. Work Unit No. 9. Performing Organization Name and Address JASA Flight Research Center . 0. Box 273 1 761-74-02-00-24 I 11. Contract or Grant No. Zdwards, California 93523 I 13. Type of Report and Period Covered 12. Sponsoring Agency Name and Address Technical Note Tational Aeronau
5、tics and Space Administration Yashington, D. C. 20546 14. Sponsoring Agency Code 15. Supplementary Notes 16. Abstract Static-pressure position-error calibrations for a compensated and an uncompensated XB-70 nose-boom Pitot-static probe were obtained in flight. The methods (Pacer, acceleration-decele
6、ration, and total tem- perature) used to obtain the position errors over a Mach number range from 0.5 to 3.0 and an altitude range from 7600 meters (25,000 feet) to 21,000 meters (70,000 feet) are discussed. The error calibrations are compared with the position error determined from wind-tunnel test
7、s, theoretical analysis, and a standard NACA Pitot-static probe. Factors which influence position errors, such as angle of attack, Reynolds number, probe tip geometry, static-orifice location, and probe shape, are discussed. Also included are examples showing how the uncertainties caused by position
8、 errors can affect the inlet controls and vertical altitude separation of a supersonic transport. 7. Key Words (Suggested by Author(s) 18. Distribution Statement itot-static probes Unclassified - Unlimited I 19. Security Classif. (of this report) $3.00 40 Unclassified Jnclassified 22. Price 21. No.
9、of Pages 20. Security Classif. (of this page) _ *For sate by the National Technical Information Service, Springfield. Virginia 22151 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-., . , Provided by IHSNot for ResaleNo reproduction or networking per
10、mitted without license from IHS-,-,-CONTENTS -ge INTRODUCTION . 1 SYMBOLS 2 DESCRIPTION OF APPARATUS 3 OnboardSensors . 3 Onboard Recording Instrumentation 3 Radar and Meteorological Apparatus . 4 Pacer Method 4 Acceleration-Deceleration Radar Method . 4 Total-Temperature Method 5 Wind-Tunnel Tests
11、. 6 PRECISION . 6 Uncertainties in Sensors and Supporting Equipment . 6 Pacer . 6 Pressure transducers . 6 Radar (AN/FPS-16) 7 AN-GMD-1 (AN/AMT-4B) rawin set . 7 Total-temperature probe . 7 Data . 7 Pacer method . 7 Acceleration-deceleration radar method . 7 Total-temperature method 8 Wind-tunnel da
12、ta 8 TESTS 8 RESULTS AND ANALYSIS . 9 XB-70 Position Errors From Wind Tunnel and Flight 9 Subsonic 10 Supersonic . 10 Analysis of Pitot-Static-Probe Characteristics 11 Angle-of-attack sensitivity 11 Reynolds number effect 11 Comparison of static-orifice location on the compensated probe . 12 FLIGHT
13、CALIBRATION PROCEDURES AND WIND-TUNNEL TESTS . 4 Uncertainties in the Flight Calibration Procedures and Vvhd-Tunnel Comparison of position errors . 12 Influence of Pitot-static Probes on Supersonic Transport Operation and Performance 13 CONCLUDING REhWRKS 14 REFERENCES . 15 TABLE 1.- VALUES OF AM AN
14、D CALIBRATION FOR THE COM- PENSATED AND UNCOMPENSATED PROBES 17 FIGURES . 18 p, . iii Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-I FLIGHT CALIBRATION OF COMPENSATED AND UNCOMPENSATED PITOT-STATIC ALRSPEED PROBES AND APPLICATION OF THE PROBES TO
15、SUPERSONIC CRUISE VEHICLES Lannie D. Webb and Harold P. Washington Flight Research Center INTRODUCTION Precise knowledge of Mach number and altitude is of utmost importance for super- sonic cruise aircraft. The information is necessary for both pilot displays and auto- matic systems. Even greater pr
16、ecision is required for evaluating the aircraft and the propulsion system performance in flight. Seemingly minor errors in the measurement of free-stream static pressure greatly affect the measurement of inlet recovery and the range of the aircraft. It has been common practice to calibrate nose-boom
17、 Pitot-static systems in wind- tunnel tests and in flight only through the transonic speed region and either to assume that there was no supersonic error or to extrapolate the usually small supersonic error to higher speeds. Experience with the XB-70 airplane (fig. 1) showed that neither practice is
18、 adequate. In some instances wind-tunnel calibrations of Pitot-static probes at high supersonic speeds may also be inadequate unless the wind-tunnel tests provide for very accurate measurements under simulated flight conditions. The XB-70 airplane was flight-tested initially with a compensated Pitot
19、-static probe which had a specially contoured shape near the static-pressure ports (ref. 1). This probe was designed to reduce the measured position error experienced by un- compensated Pitot-static probes at transonic speeds and to maintain a minimal position error at supersonic speeds. Early XB-70
20、 flight tests produced inconsistent supersonic calibration data. Because the reasons for the nonrepeatability of the data could not be determined from the flight data, wind-tunnel tests were conducted at the NASA Langley Research Center by Virgil S. Ritchie and Frank L. Jordan, Jr. Subsequently, the
21、 compensated Pitot-static probe was replaced by a more conventional uncompensated Pitot-static probe (modified MA-I type). Although the uncompensated probe produced a larger subsonic position error than the compensated probe, the supersonic data were more consistent. In this report flight and wind-t
22、unnel data are combined to form a complete position- error calibration. Position-error data from flight and wind-tunnel tests for both com- pensated and uncompensated Pitot-static probes are analyzed and compared with data from other types of Pitot-static probes. The effects of Reynolds number and a
23、ngle of attack on the data obtained from the Pitot-static probes used on the XB-70 airplane are discussed. The implications of using these types of probes on supersonic transports or other aircraft operating at high speeds and altitudes are also discussed. I Provided by IHSNot for ResaleNo reproduct
24、ion or networking permitted without license from IHS-,-,-SYMBOLS Physical quantities in this report are given in the International System of Units (SI) and parenthetically in U. S. Customary Units. Measurements were taken in Customary Units. Factors relating the two systems are presented in referenc
25、e 2. hr geometric (radar) altitude, meters (feet) hpe true pressure altitude, meters (feet) Ah Pt, 2 true pressure altitude minus indicated pressure altitude, meters (feet) stagnation pressure, newtons/meter2 (pounds/inch2) PC0 ambient pressure, newtons/mete$ (pounds/inch2) indicated static pressure
26、 minus ambient pressure, newtons/meter2 (pounds/inch2) indicated Mach number Moo true Mach number AM true Mach number minus indicated Mach number R Reynolds number, per meter (foot) SdS2 rearward manifolded static orifices (for both compensated and uncompensated Pitot-static probes) s3 TO forward ma
27、nifolded static orifices (for both compensated and un- compensated Pitot-static probes) total temperature, degrees Kelvin or degrees Celsius (degrees Rankine or degrees Fahrenheit) ambient temperature, degrees Kelvin or degrees Celsius (degrees Rankine or degrees Fahrenheit) AT0 uncertainty in the m
28、easurement of total temperature AToo uncertainty in the measurement of ambient temperature CY angle of attack, degrees Y specific-heat ratio, 1.4 2 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-AY E uncertainty in the measurement of specific-heat r
29、atio recovery factor DESCMPTION OF APPARATUS Onboard Sensors Photos of the compensated and uncompensated Pitot-static probes used on the XB-70 aircraft are shown in figure 2. Dimensions of the probes and the nose-boom assembly are shown in figures 3 and 4, respectively. As shown in figure 4, the nos
30、e boom was inclined downward at an angle of 4.17O (referenced to the aircraft s centerline) for approximate alinement of the Pitot-static probe with the relative wind during cruise flight conditions. Both types of probes used on the XB-70 airplane were equipped with dual sets of static orifices whic
31、h were sepa- rated by 2.54 centimeters (1 inch) (fig. 3). The S3 orifices were connected to the XB-70 plenum chamber reference tank system and the cockpit instruments. The pri- mary source of airspeed data was the rear set of static orifices (S1/S2), which was connected to the recording pressure tra
32、nsducers and the central air data computer. Both the compensated and the uncompensated Pitot-static probes were mounted so that the S1/S2 orifices were 180.8 centimeters (71.2 inches) from the apex of the nose of the airplane, as illustrated in figure 4. Both installations incorporated angle-of-atta
33、ck and angle-of-sideslip vanes. Two total-temperature probes were mounted on the XB-70 airplane below and 152.4 centimeters (60 inches) back of the apex edge of the inlet ramp, as illustrated in figure 5(a). The dimensions of the probes and a photograph are shown in figures 5) and 5(c), respectively
34、. Each probe consisted of two platinum, open-wire, resistance windings enclosed in three radiation shields. One total-temperature probe temperatures from -68O C (-90 F) to 171O C (340 F) and the other from 133 C (272O F) to 396O C (745O F). One platinum element in each probe provided data for the ce
35、ntral air data computer, and the other element provided data to a magnetic recording tape within the instrumentation package. measured i i I Onboard Recording Instrumentation The total and static pressures from the Pitot-static probes were measured by specially built unbonded strain gage pressure tr
36、ansducers, which were coupled directly to a 13-bit digital encoder. The output of these transducers, together with that of the air data computer and the total-temperature probes, was recorded by the airborne data acquisition system (ref. 3). To use the special pressure transducers, a 2-hour warmup w
37、as required before takeoff. Preflight and postflight zeros were obtained just before takeoff and just after landing and were compared to an aneroid barometer reading. 3 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Radar and Meteorological Apparatu
38、s Ground radars such as FPS-16, MPS-25, and SCR-584 units were used to track the XB-70 airplane to obtain its true geometric altitude. The ambient pressure and temperature at the radar-measured geometric altitude were obtained from an AN/AMT-4B rawinsonde balloon (ref. 4) released by the Air Force A
39、ir Weather Sew- ice, Edwards Air Force Base, Calif., at XB-70 takeoff. Atmospheric data from the radiosonde package were transmitted to an AN/GMD-1A rawin set (ref. 5) and re- corded on magnetic tape for subsequent data reduction (ref. 6). FLIGHT CALIBRATION PROCEDURES AND WIND-TUNNEL TESTS Because
40、of the large speed and altitude capability of the XB-70 airplane, several conventional and unconventional calibration procedures were used to obtain an airspeed calibration of the Pitot-static probes. As illustrated in figure 6, conventional stabilized Pacer data were obtained in the subsonic speed
41、region, whereas an unconventional radar tracking acceleration and deceleration technique was the primary source of airspeed data in the transonic and supersonic speed regions. The total-temperature probe was also used in the supersonic region. Wind-tunnel data helped to establish the final position-
42、error curve at the higher supersonic Mach numbers. Pacer Method Two U. S. Air Force calibrated Pacer (ref. 7) aircraft, a T-38 and an F-104, were used to calibrate the XB-70 position error in the subsonic Mach number range. During the airspeed calibration ms, the XB-70 airplane was stabilized at a p
43、redetermined altitude and Mach number. Next, the calibrated Pacer was stabilized alongside the XB-70 airplane. Indicated airspeed and pressure altitude were recorded by the cockpit camera in the Pacer aircraft. After these quantities were corrected for instrument and position error, they were correl
44、ated with the measured XB-70 pitot and static pressures to determine the static-pressure position error. Acceleration-Deceleration Radar Method An unconventional method-the acceleration-deceleration radar method-was used to calibrate the static-pressure position error of the Pitot-static airspeed in
45、stallation on the XB-70 airplane at high altitudes and at transonic and supersonic speeds. A precision radar-transponder system determined the geometric height of the airplane as it accelerated or decelerated at various pressure altitudes. During these test runs, measurements were made continuously
46、with the Pitot-static installation. True ambient pressure at a given geometric height was determined by flying the airplane at a speed for which the static-pressure error had been determined previously by an accepted method of obtaining an airspeed calibration, such as a tower flyby, a Pacer aircraf
47、t, radar plus rawinsonde balloon, a trailing cone, or a smoke trail laid by a Pacer air- Craft. Because true ambient pressure, and, hence, true pressure altitude, was known at 4 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-a referenced Mach number
48、, any small change in geometric height was assumed to correspond to a like change in pressure altitude during the calibration runs. Thus, for the Mach number range traversed during the XB-70 tests, the true pressure altitude was known and could he converted readily to true ambient pressure by using
49、standard atmospheric tables or equations. With this method, if the entire Mach number range of the test airplane could not be traversed at one test altitude, an overlapping acceleration-deceleration technique was used. The technique consisted of flying another acceleration or deceleration maneuver at a different altitude at which a larg
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