Chapter 5. Subpart F--Equipment Section 1. General
1. § 23.1301 Function and Installation.
a. Explanation. Section 23.1301 gives specific installation requirements. Particular attention should be given to those installations where an external piece of equipment could affect the flight characteristics. The flight test pilot should evaluate all installations of this nature to verify that the equipment functions properly when installed.
b. Avionics Test.
(1) Very High Frequency VHF Communication Systems. Refer to AC 20-67B. AC 20-67B references Radio Technical Commission for Aeronautics (RTCA) document DO-186.
DO-186, paragraph 3.4.2.3 speaks to ground facility coverage area. FAA Order 6050.32, Appendix 2, shows the coverage limits for various facility parameters.
(2) High Frequency (HF) Communication Systems.
(i) Ground Station Contacts. Acceptable communication should be demonstrated by contacting a ground station on as wide a range of frequencies as HF propagation conditions allow. Distances may vary from 100 to severa l hundred nautical miles (n.m.). The system should perform satisfactorily in its design modes.
(ii) Precipitation Static. It should be demonstrated that precipitation static is not excessive when the airplane is flying at cruise speed (in areas of high electrical activity, including clouds and rain if possible). Use th e minimum amount of installed dischargers for which approval is sought.
(iii) Electromagnetic Compatibility (EMC). Electromagnetic compatibility tests should be conducted on the ground and in flight at 1.0 MHz intervals. Any electromagnetic interference (EMI) noted on the ground should be repeated in flight at the frequency at which the EMI occurred on the ground. Since squat switch es may isolate some systems from operation on the ground (that is, air data system, pressurization, and so forth), EMI should be evaluated with all systems operating in flight to verify that no adverse effects are present in the engine, fuel control computer, brake antiskid, and so forth, systems.
(3) Very High Frequency Omnirange (VOR) Systems.
(i) Antenna Radiation Patterns. These flight tests may be reduced if adequate antenna radiation pattern studies have been made and these studies show the patterns to be without significant holes (with the airplane configuration used in flight; that is, flaps, landing gear, and so forth). Particular note should be made in recognition that certain propeller r.p.m.
settings may cause modulation of the course deviation indication (prop-modulation). This information should be made a part of the AFM.
(A) Reception. The airborne VOR system should operate normally with warning flags out of view at all headings of the airplane (wings level) throughout the standard service volumes depicted in the Aeronautical Information Manual (AIM) up to the maximum altitude for which the airplane is certified.
(B) Accuracy. The accuracy determination should be made such that the indicated reciprocal agrees within two degrees. Tests should be conducted over at least two known points on the ground such that data are obtained in each quadrant. Data should correlate with the ground calibration, and in no case should the absolute error exceed ±6 degrees. There should be no excessive fluctuation in the course deviation indications.
(ii) En Route Reception. Fly from a VOR facility rated for high altitude along a radial at an altitude of 90 percent of the airplane's maximum certificated altitude to the standard service volume range. The VOR warning flag should not come into view, nor should there be deterioration of the station identification signal. The course width should be 20 degrees ±5 degrees (10 degrees either side at the selected radial). The tests should be flown along published route segments to preclude ground station anomalies. If practical, perform an en route segment on a Doppler VOR station to verify the compatibility of the airborne unit. Large errors have been found when incompatibility exists. Contac t the nearest FAA Airway Facilities Sector Office to locate a Doppler VOR.
(iii) Low-Angle Reception. Perform a 360 degree right a nd 360 degree left turn at a bank angle of at least ten degrees at an altitude just above the lowest edge of the standard service volume and at the maximum service volume distance. Signal dropout should not occur as evidenced by the warning flag appearance. Dropouts that are relieved by a reduction of bank angle at the same relative heading to the station are satisfactory. The VOR identification should be satisfactory during the left and right turns. [note to myself, do a search]
(iv) High-Angle Reception. Repeat the turns described in (c) above, but a distance of 50-70 n.m. (20-30 n.m. for airplanes not to be operated above 18,000 feet) from the VOR facility and at an altitude of at least 90 percent of the maximum certificated altitude of the airplane.
(v) En Route Station Passage. Verify that the to-from indicator correctly changes as the airplane passes through the cone of confusion above a VOR facility.
(vi) VOR Approach. Conduct VOR approaches with gear and flaps down. With the facility 12-15 n.m. behind the airplane, use sufficient maneuvering in the approach to ensure the signal reception is maintained during beam tracking.
(vii) Electromagnetic Compatibility (EMC). With all systems operating in flight, verify, by observation, that no adverse effects are present in the required flight systems. In VMC, incur fault condition to test activation of failure flag on the display.
(4) Localizer Systems.
(i) Antenna Radiation Patterns. Flight test requirements should be modified to allow for adequate antenna radiation pattern measurements as discussed in VOR systems, paragraph (3)(A).
(A) Signal Strength. The input to the receiver, presented by the antenna system, should be of sufficient strength to keep the malfunction indicator out of view when the airplane is in the approach configuration (landing gear extended - approach flaps) and within the normal limits of localizer coverage shown in the AIM. This signal should be received for 360 degrees of the airplane heading at all bank angles up to ten degrees left or right at all normal pitch attitudes and at an altitude of approximately 2,000 feet (refer to RTCA guidance).
(B) Bank Angles. Satisfactory results should al so be obtained at bank angles up to 30 degrees when the airplane heading is within 60 degrees of the inbound localizer course.
Satisfactory results should result with bank angles up to 15 degrees on headings from 60 degrees to 90 degrees of the localizer inbound course and up to 10 degrees bank angle on headings for 90 degrees to 180 degrees from the localizer inbound course.
(C) Course Deviation Indicator (CDI). The deviation indicator should properly direct the airplane back to course when the airplane is right or left of course.
(D) Station Identification. The station identification signal should be of adequate strength and sufficiently free from interference to provide positive station identification, and voice signals should be intelligible with all electric equipment operating and pulse equipment transmitting.
(ii) Localizer Intercept. In the approach configurati on and at a distance of at least 18 n.m. from the localizer facility, fly toward the localizer front course, inbound, at an angle of at least 50 degrees. Perform this maneuver from both left and right of the localizer beam. No flags should appear during the time the deviation indicator moves from full deflection to on-course.
(iii) Localizer Tracking. While flying the localizer inbound and not more than five miles before reaching the outer marker, change the heading of the airplane to obtain full needle deflection. Then, fly the airplane to esta blish localizer on-course operation. The localizer deviation indicators should direct the airplane to the localizer on-course. Perform this maneuver with both a left and a right needle deflection. Continue tracking the localizer until over the transmitter. Acceptable front course and back course approaches should be conducted to 200 feet or published minimums. In VMC, incur fault condition to test activation of failure flag on the display.
(iv) Electromagnetic Compatibility (EMC). With all systems operating in flight, verify, by observation, that no adverse effects are present in the required flight system.
(5) Glide Slope Systems.
(i) Signal Strength. The signal input to the rece iver should be of sufficient strength to keep the warning flags out of view at all distances to ten n.m. from the facility. This performance should be demonstrated at all airplane headings between 30 degrees right and left of the localizer course (refer to RTCA Document DO-1010). The deviation indicator should properly direct the airplane back to path when the airplane is above or below the path.
Interference with the navigation operation, within ten n.m. of the facility, should not occur with all airplane equipment operating and all pulse equipment transmitting. There should be no interference with other equipment as a result of glide slope operation.
(ii) Glide Slope Tracking. While tracking the glide slope, maneuver the airplane through normal pitch and roll attitudes. The glide slope deviation indicator should show proper operation with no flags. Acceptable approaches to 200 feet or less above threshold should be conducted.
(iii) Electromagnetic Compatibility (EMC). With all systems operating in flight, verify, by observation, that no adverse effects are present in the required flight systems.
(6) Marker Beacon System.
(i) Flight Test.
(A) In low sensitivity, the marker beacon annunciator light should be illuminated for a distance of 2,000 to 3,000 feet when flying at an altitude of 1,000 feet AGL on the localizer centerline in all flap and gear configurations.
(B) An acceptable test to determine distances of 2,000 to 3,000 feet is to fly at a ground speed listed in the table below (table 10) and time the marker beacon light duration.
Table 10 – Light Duration Altitude = 1,000 feet (AGL) Ground Speed Light Time (Seconds) Knots 2000 feet 3000 feet 90 13 20 110 11 16 130 9 14 150 8 12 (C) For ground speeds other than table values, the following formulas may be used:
Upper limit = 1775 (seconds) Ground Speed in Knots Lower limit = 1183 (seconds) Ground Speed in Knots (D) In high sensitivity, the marker beacon annunciator light and audio will remain on longer than when in low sensitivity.
(E) The audio signal should be of adequate strength and sufficiently free from interference to provide positive identification.
(F) As an alternate procedure, cross the outer marker at normal ILS approach altitudes and determine adequate marker aural and visual indication.
(ii) Electromagnetic Compatibility (EMC). With all systems operating in flight, verify, by observation, that no adverse effects are present in the required flight system.
(7) Automatic Direction Finding (ADF) Equipment.
(i) Range and Accuracy. The ADF system installe d in the airplane should provide operation with errors not exceeding five degrees, and the aural signal should be clearly audible up to the distance listed for any one of the following types of radio beacons:
(A) 75 n.m. from an HH facility.
(B) 50 n.m. from an H facility. Caution —service ranges of individual facilities may be less than 50 n.m.
(C) 25 n.m. from an MH facility.
(D) 15 n.m. from a compass locator.
(ii) Needle Reversal. The ADF indicator needle should make only one 180 degree reversal when the airplane flies over a radio beacon. This test should be made with and without the landing gear extended.
(iii) Indicator Response. When switching stations with relative bearings differing by 180 degrees ± 5 degrees, the indicator should indicate the new bearing within ± 5 degrees in not more than ten seconds.
(iv) Antenna Mutual Interaction. For dual installations , there should not be excessive coupling between the antennas.
(v) Technique.
(A) Range and Accuracy. Tune in a number of radio beacons spaced throughout the 190-535 kHz range and located at distances near the maximum range for the beacon. The identification signa ls should be understandable and the ADF should indicate the approximate direction to the stations. Beginning at a distance of at least 15 n.m. from a compass locator in the approach configuration (landing gear extended, approach flaps), fly inbound on the localizer front course and make a normal ILS approach. Evaluate the aural identification signal for strength and clarity and the ADF for proper performance with the receiver in the ADF mode.
All electrical equipment on the airplane should be operating and all pulse equipment should be transmitting. Fly over a ground or appropriately established checkpoint with relative bearings to the facility of 0 degrees, 45 degrees, 90 degrees, 135 degrees, 180 degrees, 225 degrees, 270 degrees, and 315 degrees. The indi cated bearings to the station should correlate within five degrees. The effects of the landing gear on bearing accuracy should be determined. (A calibration placard should be provided, if appropriate.)
(B) Needle Reversal. Fly the airplane over an H, MH, or compass locator facility at an altitude 1,000 to 2,000 feet above ground level. Partial reversals that lead or lag the main reversal are permissible.
(C) Indicator Response. With the ADF indicating station dead ahead, switch to a station having a relative bearing of 175 degrees. The indicator should indicate within ±5 degrees of the bearing in not more than ten seconds.
(D) Antenna Mutual Interaction.
(1) If the ADF installation being tested is dual, check for coupling between the antenna by using the following procedure.
(2) With #1 ADF receiver tuned to a station near the low end of the ADF band, tune the #2 receiver slowly throughout the frequency range of all bands and determine whether the #1 ADF indicator is adversely affected.
-
(3) Repeat (2) with the #1 ADF receiver turned to a station near the high end of the ADF band.
(vi) Electromagnetic Compatibility (EMC). With all systems operating in flight, verify, by observation, that no adverse effects are present in the required flight systems.
(8) Distance Measuring Equipment (DME).
(i) Tracking Performances. The DME system should continue to track without dropouts when the airplane is maneuvered throughout the airspace within the standard service volume of the VORTAC/DME station and at altitudes above the lower edge of the standard service volume to the maximum operating altitude. This tracking standard should be met with the airplane:
(A) In cruise configuration;
(B) At bank angle up to ten degrees;
(C) Climbing and descending at normal maximum climb and descent attitude;
(D) Orbiting a DME facility; and (E) Providing a clearly readable identification of the DME facility.
(ii) Electromagnetic Compatibility (EMC). With all systems operating in flight, verify, by observation, that no adverse effects are present in the required flight systems.
(iii) Climb and Maximum Distance. Determine that there is no mutual interference between the DME system and other equipment aboard the airplane. Beginning at a distance of at least ten n.m. from a DME facility and at an altitude of 2,000 feet above the DME facility, fly the airplane on a heading so that the airplane will pass over the facility. At a distance of five to ten n.m. beyond the DME facility, operate the airplane at its normal maximum climb attitude up to 90 percent of the maximum operating altitude, maintaining the airplane on a station radial (within five degrees). The DME should continue to track with no unlocks to the range of the standard service volume.
(iv) Long-Range Reception.
(A) Perform two 360 degree turns, one to the right and one to the left, at a bank angle of at leastten degrees at the maximum service volume distance of the DME facility and at an altitude of at least 90 percent of the maximum operating altitude.
(B) Unlocks may occur and are acceptable if they do not interfere with the intended flight path of the airplane or are relieved by a reduction of bank angle at the same relative heading to the station.
(v) High-Angle Reception. Repeat the flight pattern and observations of (iii) above at a distance of 50-70 n.m. (20-30 n.m. for airplanes not to be operated above 18,000 feet) from the DME facility and at an altitude of at least 90 percent of the maximum operating altitude.
(vi) Penetration. From 90 percent of the maximum operating altitude, perform a letdown directly toward the ground station using normal maximum rate of descent procedures to a DME facility so as to reach an altitude of 5,000 feet above the DME facility 5-10 n.m. before 143
reaching the DME facility. The DME should continue to track during the maneuver with no unlocks.
(vii) Orbiting. At an altitude of 2,000 feet above the terrain, at holding pattern speeds appropriate for the type of airplane and with the landing gear extended, fly at least 15 degree sectors of left and right 35 n.m. orbital patterns around the DME facility. The DME should continue to track with no more than one unlock, not to exceed one search cycle, in any five miles of orbited flight.
(viii) Approach. Make a normal approach at an actual or simulated field with a DME. The DME should track without an unlock (station passage expected).
(ix) DME Hold. With the DME tracking, activate the DME hold function.
Change the channel selector to a localizer frequency. The DME should continue to track on the original station.
(9) Transponder Equipment.
(i) Signal Strength. The Air Traffic Control (ATC) transponder system should furnish a strong and stable return signal to the interrogating radar facility when the airplane is flown in straight and level flight. This includes the airspace within 160 n.m. of the radar station from radio line of sight to within 90 percent of the maximum altitude for which the airplane is certificated or to the maximum operating altitude. Airplanes to be operated at altitudes not exceeding 18,000 feet should meet the above requirements to only 80 n.m.
(ii) Single Site Tracking. Special arrangements shoul d be made for single-site tracking. ATC coverage includes remote stations and, unless single-site is utilized, the data may be invalid.
(iii) Dropout Times. When the airplane is flown within the airspace described above, the dropout time should not exceed 20 seconds in the following maneuvers:
(A) In turns at bank angles up toten degrees;
(B) Climbing and descending at normal maximum climb and descent attitude;
and (C) Orbiting a radar facility.
(iv) Climb and Distance Coverage.
(A) Beginning at a distance of at least ten n.m. from and at an altitude of 2,000 feet above that of the radar facility and using a transponder code assigned by the ARTCC, fly on a heading that will pass the airplane over the facility. Operate the airplane at its normal maximum climb attitude up to within 90 percent of the maximum altitude for which the airplane is certificated, maintaining the airplane at a heading within five degrees from the radar facility.
After reaching the maximum altitude for which the airplane is certificated, fly level at the maximum altitude to 160 (or 80) n.m. from the radar facility.
(B) Communicate with the ground radar personnel for evidence of transponder dropout. During the f light, check the "ident" mode of the ATC transponder to ensure that it is performing its intended function. Determine that the transponder system does not interfere with other systems aboard the airplane and that other equipment does not interfere 144
with the operation of the transponder system. There should be no dropouts for two or more sweeps.
(v) Long-Range Reception. Perform two 360 degree turns, one to the right and one to the left, at bank angles of at least ten degrees with the flight pattern at least 160 (or 80)
n.m. from the radar facility. During these turns, the radar display should be monitored and there should be no signal dropouts (two or more sweeps).
(vi) High-Angle Reception. Repeat the flight pattern and observations of (d) above at a distance of 50 to 70 n.m. from the radar facility and at an altitude of at least 90 percent of the maximum operating altitude. There should be no dropout (two or more sweeps). Switch the transponder to a code not selected by the ground controller. The airplane secondary return should disappear from the scope. The controller should then change his control box to a common system and a single slash should appear on the scope at the airplane's position.
(vii) High-Altitude Cruise. Fly the airplane within 90 percent of its maximum certificated altitude or its maximum operating altitude beginning at a point 160 (or 80) n.m. from the radar facility on a course that will pass over the radar facility. There should be no transponder dropout (two or more sweeps) or "ring-around."
(viii) Holding and Orbiting Patterns.
(A) At an altitude of 2,000 feet or minimum obstruction clearance altitude (whichever is greater) above the radar antenna and at holding pattern speeds, flaps and gear extended, fly one each standard rate 360 degree turn right and left at a distance of approximately ten n.m. from the ARSR facility. There should be no signal dropout (two or more sweeps).
(B) At an altitude of 2,000 feet or minimum obstruction clearance altitude (whichever is greater) above the radar antenna and at holding pattern speeds appropriate for the type of airplane, fly 45 degree sectors of left and right ten n.m. orbital patterns around a radar facility with gear and flaps extended. There s hould be no signal dropout (two or more sweeps).
(i) Electromagnetic Compatibility (EMC). With all systems operating in flight, verify, by observation, that no adverse effects are present in the required flight systems.
(10) Weather Radar.
(i) Bearing Accuracy. The indicated bearing of objects shown on the display should be within ±10 degrees of their actual relative bearing. Verify that as airplane turns to right or left of target, the indicated display moves in the opposite direction. Fly under conditions that allow visual identification of a target, such as an island, a river, or a lake, at a range of approximately 80 percent of the maximum range of the radar. When flying toward the target, select a course that will pass over a reference point from which the bearing to the target is known. When flying a course from the reference point to the target, determine the error in displayed bearing to the target on all range settings. Change heading in increments of ten degrees and determine the error in the displayed bearing to the target.
(ii) Distance of Operation. The radar should be capable of displaying distinct and identifiable targets throughout the angular range of the display and at approximately 80 percent of the maximum range.
(iii) Beam Tilting. The radar antenna should be installed so that its beam is adjustable to any position between ten degrees above and below the plane of rotation of the antenna. Tilt calibration should be verified.
(iv) Contour Display (ISO Echo).
(A) If heavy cloud formations or rainstorms are reported within a reasonable distance from the test base, select the contour display mode. The radar should differentiate between heavy and light precipitation.
(B) In the absence of the above weather conditions, determine the effectiveness of the contour display function by switching from normal to contour display while observing large objects of varying brightness on the indicator. The brightest object should become the darkest when switching from normal to contour mode.
(v) Antenna Stabilization, When Installed. While in level flight at 10,000 feet or higher, adjust the tilt approximately 2-3 degrees above the point where ground return was eliminated. Roll right and left approximately 15 degrees, then pitch down approximately ten degrees (or within design limits). No ground return should be present.
(vi) Ground Mapping. Fly over areas containing large, easily identifiable landmarks such as rivers, towns, islands, coastlines, and so forth. Compare the form of these objects on the indicator with their actual shape as visually observed from the cockpit.
(vii) Mutual Interference. Determine that no objectionable interference is present on the radar indicator from any electrical or radio/navigational equipment when operating and that the radar installation does not interfere with the operation of any of the airplane's radio/navigational systems.
(viii) Electromagnetic Compatibility. With all systems operating in flight, verify, by observation, that no adverse effects are present in the required flight systems.
(ix) Light Conditions. The display should be evaluated during all lighting conditions, including night and direct sunlight.
(11) Area Navigation.
(i) AC 90-96. This AC has the basic criteria for evaluating an area navigation system, including acceptable means of compliance to 14 CFR.
(ii) Electromagnetic Compatibility (EMC). With all systems operating in flight, verify, by observation, that no adverse effects are present in the required flight systems.
(12) Inertial Navigation.
(i) Basic Criteria. AC 25-4 has the basic criteria for the engineering evaluation of an INS and offers acceptable means of compliance with the applicable 14 CFR part. The engineering evaluation of an INS should also include an awareness of AC 121-13, which presents criteria to be met before an applicant can get operational approval. For flights up to ten hours, the radial error should not exceed two n.m. per hour of operation on a 95 percent statistical basis. For flights longer than ten hours, the error should not exceed ±20 n.m. crosstrack or ±25 n.m. along-track error. A two n.m. radial error is represented by circle, having a radius of two n.m., centered on the selected destination point.
(i) Electromagnetic Compatibility (EMC). With all systems operating in flight, verify, by observation, that no adverse effects are present in the required flight systems.
(13) Doppler Navigation.
(i) Doppler navigation system. Installed performance should be evaluated in accordance with AC 121-13.
(ii) Electromagnetic Compatibility (EMC). With all systems operating in flight, verify, by observation, that no adverse effects are present in the required flight systems.
(14) Audio Interphone Systems.
(i) Acceptable communications. These should be demonstrated for all audio equipment including microphones, speakers, headsets, and interphone amplifiers. All modes of operation should be tested, including operation during emergency conditions (that is, emergency descent, and oxygen masks) with all engines running, all pulse equipment transmitting and all electrical equipment operating. If aural warning systems are installed, they should be evaluated, including distinguishing aural warnings when using headphones and with high air noise levels.
(ii) Electromagnetic Compatibility (EMC). With all systems operating during flight, verify, by observation, that no adverse effects are present in the required flight systems.
(15) Electronic Flight Instrument Systems. Refer to AC 23.1311-1.
(16) LORAN C Navigation Systems. Refer to AC 20-121A.
(17) Microwave Landing Systems. Reserved.
(18) Global Positioning System Navigation. Reserved.
2. § 23.1303 Flight and Navigation Instruments.
a. Free Air Temperature (FAT). Section 23.1303(a)(4) requires that reciprocating engine- powered airplanes of more than 6,000 pounds maximum weight and turbine-powered airplanes have a free air temperature indicator or an air temperature indicator that provides indications that are convertible to free air. The temperature pickup can be calibrated against a test pick-up of known characteristics, or by flying at various speeds at constant altitude, or by tower fly-by. This calibration is frequently done in conjunction with one or more of the airspeed calibration methods described in paragraph 23.1323 of this AC.
b Speed Warning Device. The production tolerances of the speed warning device required with § 23.1303(a)(5) must be set to minimize nuisance warnings. In considering this requirement, manufacturers should endeavor to reduce, lessen, or diminish such an occurrence to the least practical amount with current technology and materials. The least practical amount is that point at which the effort to further reduce a hazard significantly exceeds any benefit, in terms of safety, derived from that reduction. Additional efforts would not result in any significant improvements in reliability.
3. § 23.1305 Powerplant Instruments.
a. Explanation. Section 23.1305 is specific as to the powerplant instruments required for each type of installation. The requirement for specific instruments on specific airplanes should be determined by analysis of type design data prior to certification flight test.
b. Procedures. Verify proper functioning of each required instrument/indicator installed. If the creation of a required malfunction would require establishing a potentially hazardous condition in flight, proper functioning of these indicators may be verified by ground test.
c. Fuel Flowmeters. AC 23-17 covers the installation of fuel flowmeters in airplanes with continuous-flow fuel injection reciprocating engines.
4. § 23.1307 Miscellaneous Equipment. Reserved.
5. § 23.1309 Equipment, Systems, and Installations. This item is covered in AC
23.1309-1E.
Section 2. Instruments: Installation
1. § 23.1311 Electronic Display Instrument Systems. This item is covered in AC
23.1311-1.
2. § 23.1321 Arrangement and Visibility. Reserved.
3. § 23.1322 Warning, Caution, and Advisory Lights. Reserved.
4. § 23.1323 Airspeed Indicating System.
a. Explanation.
(1) Airspeed Indicator. An airspeed indicator is usually a pressure gauge that measures the difference between free stream total pressure and static pressure and is usually marked in knots. Pitot tubes for duplicate airspeed indicators are usually located on opposite sides of an aircraft fuselage but may be situated on the same side provided that they are separated by at least 14 inches (35.6 cm.) vertically.
(2) Air Data Computer Systems. Reserved.
(3) Definitions. Section 1.1 of part 1 of 14 CFR defines IAS, CAS, equivalent air speed (EAS), true air speed (TAS), and Mach number. These definitions include the terms position error, instrument error, and system error, which may need further explanation.
(i) Position Error. Position error is the total-pressure (pitot) and static-pressure errors of the pilot-static installation. By proper design, the total pressure error may be reduced to the point where it is insignificant for most flight conditions. NASA Reference Publication 1046 (refer to paragraph g gives various design considerations. The static pressure is more difficult to measure and the static position error may result in large airspeed and altitude errors.
(ii) Instrument Error. Instrument errors are errors inherent in the instrument for mechanical instruments. These errors are the result of manufacturing tolerances, hysteresis, temperature changes, friction, and inertia of moving parts. For electronic instruments, these errors are due to errors in the electronic element that converts pitot-static pressures into electronic signals. Instrument errors are determined for infl ight conditions in steady state conditions. Ground run system calib rations may require the consideration of internal instrument dynamics, electronic lags, and display filtering that would cause indication errors during takeoff acceleration.
(iii) System Error. System error is the combination of position error and instrument error.
(4) Temperatures. Static air temperature (SAT) a nd total air temperature (TAT) are not defined in section 1.1 of 14 CFR but may be significant in accurate calibration of airspeed systems. For stabilized values of pressure altitude and calibrated airspeed, TAS is a function of static air temperature. Reference (2) in section f of appendix 2 discusses the heating effect of the airflow on the temperature sensor and shows how to determine the recovery factor of the sensor.
Figure 7 of appendix 7 gives temperature ram rise, if the sensor recovery factor is known.
(5) System Calibration. The airspeed system is calibrated to determine compliance with the requirements of § 23.1323 and to establish an airspeed reference that is used in demonstrating compliance with other applicable regulations. The airspeed system may be calibrated using the speed course method, pacer airplane method, tower fly-by method, trailing cone method or either the trailing bomb or airspeed boom method or both. The method used will depend on the speed range of the airplane tested, the configuration, and the equipment available.
System calibration of the airspeed system is usually determined at altitudes below 10,000 feet.
For airplanes approved for flight above 31,000 feet, it is appropriate to verify validity of position errors at the higher operating altitudes. For airplanes where the static ports are located in close proximity to the propeller plane, it should be verified that sudden changes in power do not appreciably change the airspeed calibration. Additionally, for commuter category airplanes, § 23.1323(e) requires an airspeed calibration for use during the accelerate-takeoff ground run.
(6) Instrument Calibration. All instruments used during the test should be calibrated, and all calibration curves should be included in the type inspection report.
b. Speed Course Method. The speed course method consists of using a ground reference to determine variations between indicated airspeed and ground speed of the airplane.
Refer to appendix 9 for test procedures and a sample data reduction.
c. Trailing Bomb or Airspeed Boom Method. Refer to appendix 9 for procedures, test conditions, and a sample data reduction.
d. Pace Airplane Method. Refer to appendix 9 for test procedures.
e. Tower Fly-by. Refer to appendix 9 for test procedures.
f. Ground Run Airspeed System Calibration. The airspeed system is calibrated to show compliance with commuter category requirements of § 23.1323(c) during the acceleratetakeoff ground run and is used to determine IAS values for various V1 and VR speeds. Refer to appendix 9 for definitions, test procedures, and sample data reductions.
g. Other Methods. Other methods of airspeed calibration are described in NASA Reference Publication 1046, "Measurement of Aircraft Speed and Altitude," by W. Gracey, May 1980. Refer to appendix 9 for GPS method.
5. § 23.1325 Static Pressure System.
a. Definitions. Section 23.1323 defines several of the terms associated with the pitot static systems. Others may need further explanation.