Some standard content:
National Standard of the People's Republic of China
GB/T11469—1989
General specification for radio altimeters
General specification for radio altimeters1989-03-01Promulgated
Implementation on 1990-01-01
Promulgated by the Ministry of Machinery and Electronics Industry of the People's Republic of China
National Standard of the People's Republic of China
General specification for radio altimeters
General specification for radio altimeters1Subject content and scope of application
GB/T11469—1989
This standard specifies the general technical requirements, test methods, inspection rules and marking, packaging, transportation and storage of radio altimeters (hereinafter referred to as altimeters).
This standard applies to altimeters used by various types of aircraft, and altimeters used by other aircraft should also be used as a reference. 2 Reference standards
GB2423.4 Basic environmental test procedures for electric and electronic products Test Db: Alternating damp heat test method
GB2423.16 Basic environmental test procedures for electric and electronic products Test J: Mildew test method
GB2423.17
Basic environmental test procedures for electric and electronic products Test Ka: Salt spray test method
GB2423.22
HB5662wwW.bzxz.Net
HB5870
3 Technical requirements
Basic environmental test procedures for electrical and electronic productsTest Nb: Temperature change test method with specified temperature change rate
Requirements and test methods for electromagnetic compatibility of aircraft equipmentGeneral technical conditions for transportation packaging of aviation auxiliary productsPackaging storage and transportation graphic signs
3.1 General requirements
3.1.1 Appearance
The surface should not have obvious dents, cracks, deformation, etc., and the surface coating should not bubble, crack or fall off; metal parts should not have rust and other mechanical damage.
3.1.2 Safety
The personal safety of the operator must be considered, and the easily accessible parts with high working voltage should be protected; the casing should have a reliable grounding device.
3.1.3 Working frequency
The working frequency should be selected in the following range: 1.5~1.7GHz and 4.2~4.4GHz. 3.1.4 Transceiver
The transceiver shall be capable of independently providing altimeter information output, and shall have a jack and monitoring device for testing the main performance of the altimeter.
3.1.5 Antenna
The antenna's directional pattern, gain, standing wave ratio, and isolation shall meet the requirements of the product standard. 3.1.6 Indicator
The indicator shall be direct-reading and have internal lighting; for pointer-type indicators, there shall be no reflection, and the pointer shall be as close to the dial as possible to reduce parallax. The indicator shall have a simple and identifiable altitude warning indication and fault warning indication. Approved by the Ministry of Machinery and Electronics Industry of the People's Republic of China on March 1, 1989 and implemented on January 1, 1990. 3.1.7 High-frequency cable
The total attenuation of the high-frequency cable connected between the transceiver and the antenna should be less than the gain of one antenna, and the standing wave ratio of the high-frequency cable should meet the requirements of the product standard.
3.1.8 Operation and accessibility of controllers
During flight, the operation of the controllers in various possible combinations and sequences should not have a harmful effect on the continuous working performance of the altimeter; controllers that do not usually require adjustment should be placed in places that are not easily accessible to flight personnel. 3.1.9 Self-test
The altimeter should have a self-test function. Any failure of the self-test device should not affect the performance of the altimeter. 3.1.10 Multi-channel operation
When more than two independently operating altimeters work simultaneously on the same aircraft, they should not affect each other. 3.1.11 Warm-up time
Unless otherwise specified, the warm-up time shall not exceed 3 minutes. 3.1.12 Output interface
The output interface of the altimeter shall comply with the provisions of the relevant interface standards. 3.1.13 Power supply requirements
The altimeter can work normally under the conditions of DC 27V±10%, AC 115V±5%, 400Hz±5%. 3.2 Main performance requirements
3.2.1 Altimeter range
The altimeter range is specified by the product standard. 3.2.2 Indicator accuracy
When the altimeter range is below 760m, the altimeter indicator accuracy shall comply with the provisions of Table 1. When the altimeter range is greater than 760m, the altimeter indicator accuracy shall be specified by the product standard.
3.2.3 Altimeter accuracy
When the altimeter range is below 760m, the altimeter altitude accuracy shall comply with the provisions of Table 1. When the altimeter range is greater than 760m, the altimeter altitude accuracy shall be specified by the product standard.
Table 1 Accuracy Classification
0～~30
30~150
150~760
3.2.4 Sensitivity
Indicator Accuracy
Altimeter Altimeter Voltage Output Altimeter Accuracy
The sensitivity of the altimeter shall ensure the requirements of the altitude measurement range and altitude measurement accuracy. The sensitivity shall be specified by the product standard. 3.2.5 Altitude Alarm Range and Alarm Accuracy
The alarm altitude shall be continuously adjustable within the entire altitude measurement range. The alarm accuracy shall be specified by the product standard. 3.2.6 Fault Alarm
When the altimeter loses power or loses the ability to measure altitude, a fault alarm shall be provided. 3.2.7 Locking Function
When the altitude exceeds the altitude measurement range, the altitude signal output of the altimeter shall be greater than the maximum altitude measurement value or less than zero meters. 3.2.8 Output noise
GB/T11469—1989
Within 30m, the RMS value of the noise contained in the altimeter altitude signal output must be less than 0.1m. 3.2.9 Response time
At altitudes below 60m, when the input altitude signal jumps by 10%, the response time of the output signal should not exceed 0.1s. 3.3 Environmental requirements
3.3.1 Temperature-altitude
The altimeter should be able to operate normally at the temperature and altitude specified in Table 2. For the classification of the use conditions of the altimeter temperature-altitude test, see Appendix A (Supplement). Table 2 Temperature and altitude requirements
Low temperature working temperature, ℃
High temperature working temperature, ℃
High temperature short-time
working temperature, ℃
Ground low temperature
Tolerance temperature, ℃
Ground high temperature
Tolerance temperature, ℃
Altitude, km
+55+70
+55+70
+70+70
+70+70
+85+85+85+85
Note: 1) Specified by product standards.
3.3.2 Temperature change
The altimeter should be able to work normally during the temperature change of -55～+55℃. 3.3.3 Alternating damp heat
The altimeter should be able to work normally in an alternating damp heat environment with a temperature of +25～+55℃ and a relative humidity of not less than 95%. 3.3.4 Vibration
Under the conditions specified in Table 3 and Figure 1, during the normal vibration test, the altimeter can work normally and keep its structure intact. After the endurance vibration test, the altimeter can work normally.
GB/T11469—1989
Hnrnig\
The highest exemption seat. H
Figure 1 Vibration test curve
Test classification
Normal vibration
Durable vibration
3.3.5 Shock
Aircraft equipped with
Turbojet or turbofan
engine
Aircraft with propeller engine
Helicopter
Turbojet
Shock absorber
GB/T 11469—1989
Vibration level classification
Test level
Frequency range
55~2000
55~2000
55~300
55~300
70~100
55~2000
Double amplitude
Acceleration
The altimeter should be able to work normally under working impact conditions and keep the structure intact. Under collision safety impact conditions, bending and deformation are allowed, but the installation connection parts shall not have mechanical damage and displacement of the altimeter. 3.3.6 Fungus
The altimeter should not have rust that affects mechanical and electrical connections under tropical climate fungus growth conditions. 3.3.7 Salt spray
The altimeter should not have rust that affects the mechanical and electrical connections under the marine salt spray atmospheric conditions. 3.3.8 Acoustic vibration
The altimeter should be able to work normally under the maximum noise sound pressure level of 135dB and ensure that the structure is intact. 3.3.9 Explosive atmosphere
The altimeter working in various states (height measurement, alarm, tripping, self-test) should not cause the explosion of the mixed gas in the test chamber. 3.4 Power supply change requirements
The performance of the altimeter should meet the requirements when the input power supply voltage and frequency change. 3.5 Reliability and maintainability requirements
The mean time between failures (MTBF) and the mean time to repair (MTTR) of the altimeter should be specified in the product standard. 3.6 Magnetic influence
In various working states, the safety distance of the altimeter that causes the standard magnetic compass to be disturbed and deflected by 1° should not be greater than 0.3m. 3.7 Electromagnetic compatibility requirements
GB/T11469—1989
The electromagnetic compatibility requirements of the altimeter shall comply with the requirements of HB5662. 3.8 Transportation requirements
After being transported under the specified conditions, the altimeter shall operate normally and have no mechanical damage. 3.9 Flight test
The altimeter shall meet the main technical requirements during flight during flight test. The measurement conditions for the altimeter to conduct aircraft tests should be: lateral speed: 0~15m/s;
longitudinal speed: 0~90m/s;
vertical speed: below 30m, 0~5m/s
above 30m, 7m/s;
pitch angle range: 0~±20°
roll angle range: 0~±20
4 Test method
Unless otherwise specified, all performance tests should be carried out under the following normal test atmospheric conditions: a.
Temperature: 15~35℃;
Relative humidity: 45%~75%
Air pressure: 86~106kPa.
Unless otherwise specified, the accuracy of the instruments and special equipment used to test the altimeter shall be three times the accuracy index of the altimeter being tested. b.
The volume of the test chamber shall be at least ten times the volume of the altimeter. c.
The normal test voltage shall be:
DC: 27.5±0.5V, AC: 115±2V, 400±8Hz. e.
Pretreatment: If necessary, the altimeter shall be kept in normal test atmospheric conditions for at least 4 hours before each environmental test. For the requirements in Article 3.1, if the test method is not given in this chapter, it shall be checked by checking the altimeter manufacturing drawings and other relevant documents.
4.1 General test
4.1.1 Appearance
The visual inspection shall meet the requirements of Article 3.1.1. 4.1.2 Antenna
Inspect according to the test method specified in the product standard and it shall meet the requirements of Article 3.1.5. 4.1.3 High-frequency cable
Inspect according to the test method specified in the product standard and it shall meet the requirements of Article 3.1.7. 4.2 Main performance test
4.2.1 Altitude measurement range
According to the aircraft test method.
4.2.2 Indicator accuracy
Measure by comparing the indicated reading with the standard altitude (in the form of voltage, current and other signals) input to the indicator. Select multiple test points within the entire indicated altitude range. The preferred test points are: one point every 30m below 150m; one point every 100m above 150m.
4.2.3 Altitude measurement accuracy
Connect the test circuit according to Figure 2, and measure the height signal (voltage, current, resistance, mathematical and other signal forms) output by the altimeter by comparing it with the equivalent height of the altitude simulator. There should be no less than two test points in the entire altitude measurement range. When measuring the altitude measurement accuracy, the attenuation of the external loop should be consistent with the attenuation of the external loop at the accuracy calibration point, and the attenuation error should be less than ±2dB. Altitude indicator
4.2.4 Sensitivity
No-electric sticker meter
Pre-installation device
Altimeter test schematic diagram
Korean voltage car
Altitude simulator
Measure the sensitivity of the altimeter and connect according to Figure 2. The simulated altitude should comply with the provisions of the product standard. On the basis of 4.2.3, gradually increase the loop attenuation until the change of the altimeter altitude output signal reaches the specified error. At this time, the total attenuation of the outer loop is the sensitivity of the altimeter.
4.2.5 Altitude alarm range and alarm accuracy
On the basis of 4.2.2, adjust the alarm mark to the scale line of the test altitude, change the altitude signal input to the indicator, and make the pointer approach the alarm mark in the direction of decreasing altitude until the alarm is sounded. The difference between the altitude corresponding to the altitude signal and the altitude scale value at this time is the alarm accuracy. The alarm mark should be continuously adjustable in the entire altitude measurement range, and the test point is the same as that of 4.2.2. 4.2.6 Fault alarm
When the altimeter is powered on, the altimeter is powered off or loses its altitude measurement capability. The fault alarm device should provide an alarm signal (flag or voltage).
4.2.7 Locking function
The locking function of the altimeter shall be checked according to the test method specified in the product standard and shall meet the requirements of 3.2.7. 4.2.8 Output noise
Inspect according to the test method of product standard. 4.2.9 Response time
Connect the altimeter to the altitude simulator and adjust the simulated altitude between 30m and 60m. Then suddenly change 10% of the simulated value. At this time, the output of the altimeter should reach 63% of the stable value with an overshoot of less than 5%. The response time should be less than 0.1s. 4.3 Environmental test
4.3.1 Temperature-altitude
4.3.1.1 Temperature test
a. Low temperature test
The altimeter is not working. It is placed in the test box. Under standard air pressure, the temperature of the altimeter is stabilized at the ground low temperature tolerance temperature specified in Table 2 and maintained at this temperature for at least 3h. Then, when the altimeter is in working state, the air temperature of the test box is adjusted and maintained at the low temperature working temperature specified in Table 2. After the temperature of the altimeter reaches stability, it is powered on for another 30min. During this period, the air temperature of the test box is maintained at the low temperature working temperature specified in Table 2. Finally, determine whether the altimeter meets the requirements of Articles 3.2.2 to 3.2.7 of this standard. The temperature in the test chamber must be maintained within ±3°C of the specified temperature. b. High-temperature short-time working test
Under standard atmospheric pressure, the altimeter does not work, and the temperature in the test chamber is stabilized at the ground high temperature tolerance temperature specified in Table 2, and this temperature is maintained for 3 hours. Then, when the altimeter is not working, it is subjected to the high-temperature short-time working temperature in Table 2 for no less than 30 minutes, and then the altimeter is operated, and the temperature in the test chamber is maintained at the high-temperature short-time working temperature in Table 2, and the altimeter works for 30 minutes. During its operation, determine whether it meets the requirements of Articles 3.2.2 to 3.2.7 of this standard. If the high-temperature short-time working temperature is the same as the high-temperature working temperature, there is no need to perform the high-temperature short-time working temperature test. c. High temperature working test
The altimeter is in working state. Under standard air pressure, adjust the temperature in the test chamber to the high temperature working temperature specified in Table 2. After the altimeter temperature reaches stability, make the altimeter work for another 2 hours, and keep the air temperature in the test chamber at the high temperature working temperature. During the 2-hour working period of the altimeter, determine whether it meets the requirements of 3.2.2 to 3.2.7 of this standard. 4.3.1.2 Altitude test
Make the altimeter work under normal test environment temperature, reduce the air pressure to the altitude specified in Table 2, and keep the altimeter temperature stable for 2 hours. Determine whether it meets the requirements of 3.2.2 to 3.2.7 of this standard. 4.3.2 Temperature change
The temperature change test is carried out in accordance with the provisions of GB2423.22 test Nb. The average speed of the box temperature change is 1 ± 0.2℃/min, the number of cycles is 2, and the exposure time T1 is 1h.
4.3.2.1 Initial test
Performance measurement and appearance inspection are carried out under normal test atmospheric conditions. After that, the altimeter is placed in the test chamber. 4.3.2.2 Intermediate test
During the test, the altimeter is powered on and runs at the simulated altitude specified in the product standard, and should work without failure. After the cycle is completed, the chamber temperature reaches the temperature of the normal test atmospheric conditions and stabilizes before it can be taken out of the chamber. 4.3.2.3 Final test
Under normal test atmospheric conditions, place it for 2 hours to allow the temperature to stabilize, and perform a performance check. It should meet the requirements of 3.2.2 to 3.2.7.
4.3.3 Alternating damp heat
Alternating damp heat test is carried out in accordance with GB2423.4 Test Db is carried out, the high temperature is 55℃, and the cycle days are 6 days. 4.3.3.1 Initial test
Same as 4.3.2.1.
4.3.3.2 Intermediate test
During the last 2 hours of the high temperature period of each cycle, turn on the power supply and the altimeter should work without failure. After the cycle is over, the box temperature reaches the temperature of the normal test atmosphere and can be taken out of the box only after it stabilizes. 4.3.3.3 Final test
After being placed under normal test atmosphere for 24 hours, perform performance inspection and it should meet the requirements of 3.2.2 to 3.2.7. 4.3.4 Vibration
The vibration test is carried out by the test method of continuous sinusoidal swept frequency vibration. According to the installation method used on the aircraft, it is fixed on the vibration table by a special clamp, and the three axial directions of X, Y and Z should be tested respectively.
X axis: consistent with the longitudinal axis of the aircraft, forward is positive. Y axis: in line with the horizontal axis of the aircraft, positive to the right. Z axis: in line with the vertical axis of the aircraft plane, positive downward. 4.3.4.1 Normal vibration
The altimeter fixed on the vibration table is in working condition, and the X-axis direction is vibrated first. Change the frequency and amplitude of the vibration at a rate not exceeding 1.0 oct/min within the range specified in Table 3 and Figure 1. During the initial frequency scan, the critical frequency of the altimeter should be determined. The critical frequency is defined as the frequency at which mechanical resonance (peak amplitude) and significant change in altimeter performance occur, and the altimeter performance indicators are not considered at this time. In addition, any changes or no changes in the critical frequency during the vibration test should be recorded, and the continuous vibration working time is 1 hour. 8
GB/T11469—1989
According to the above requirements, vibrations are carried out in the Y-axis and Z-axis directions respectively, and the total vibration time in the three directions is 3 hours. The altimeter should be free of faults and work normally during vibration. After vibration, appearance inspection, mechanical inspection and performance inspection should be carried out, and the requirements of Articles 3.2.2 to 3.2.7 should be met.
Normal vibration is applicable to altimeters installed on various aircraft. 4.3.4.2 Endurance vibration
Endurance vibration is applicable to altimeters installed on turbojet aircraft. The altimeter is in working condition and vibrates according to the provisions of Table 3 and Figure 1. The vibration duration in each direction is 3 hours, and the vibration time in the three directions is 9 hours in total. The altimeter is not required to meet the performance requirements of the product standard during this vibration period. After vibration, the altimeter meets the requirements of 3.2.2 to 3.2.7.
4.3.5 Shock
4.3.5.1 Working shock
According to the installation method used on the aircraft, the altimeter is fixed on the shock table by a special clamp, and the altimeter is impacted 3 times in the upper and lower directions parallel to the vertical axis of the altimeter, 3 times in the front and rear directions parallel to the horizontal long axis of the altimeter, and 3 times in the left and right directions parallel to the horizontal short axis of the altimeter, for a total of 18 times. The peak acceleration of each shock is 60m/s, and the pulse duration is 11ms. After the impact, the altimeter shall be inspected for appearance, mechanical and performance, and shall meet the requirements of 3.2.2 and 3.2.7. 4.3.5.2 Impact safety
Apply a peak acceleration of 150m/s2 and a pulse duration of 11ms to each altimeter at the position described in 4.3.5.1. After these 6 impacts, check whether the altimeter has mechanical damage. Bending and deformation are allowed at this time, but there shall be no mechanical damage to the installation connection part, and the altimeter shall not be displaced. This test can also use a model of the same mass to replace the altimeter, but the center of gravity position shall not be changed, and the installation of the model shall not increase the installation strength of the altimeter housing and mounting frame. 4.3.6 Fungus
The fungus test shall be carried out in accordance with GB2423.16 Test J, with an exposure time of 28d. Place an altimeter in the test box without packaging and without power for testing.
4.3.6.1 Initial test
Same as 4.3.2.1.
4.3.6.2 Final test
After the test, take the altimeter out of the box and immediately conduct an appearance inspection. The degree of mold growth is allowed to be 2 levels. a.
b. Wipe off the mold and use a magnifying glass to check the degree of physical corrosion on the surface. It should meet the requirements of Article 3.3.6. c. Under normal test atmospheric conditions, the recovery time is 24 hours, and then the performance test is carried out. It should meet the requirements of Articles 3.2.2 to 3.2.7. 4.3.7 Salt spray
The salt spray test is carried out in accordance with GB2423.17 test Kb, and the exposure time is 48 hours. The altimeter is not powered on and placed in the test box. The unused plug sockets should be covered with protective covers.
4.3.7.1 Initial test
Same as Article 4.3.2.1. The surface should be clean and there should be no damage to the protective layer. 4.3.7.2 Final test
After the test, remove the outer shell, wash off the salt deposits on the outer shell with running water, clean the salt stains that have penetrated into the altimeter with a cotton ball soaked in distilled water, and check the corrosion. After that, restore it under normal test atmospheric conditions for 24 hours, and then install the outer shell for performance inspection. Before the performance inspection, the power-on preheating time is allowed to be 20 minutes, and the requirements of 3.2.2 to 3.2.7 shall be met. 4.3.8 Acoustic vibration
4.3.8.1 Test equipment
a. The test room
shall be a reflection reverberation test room that can produce a chaotic diffuse sound field. When noise is introduced, the sound pressure distribution in the room shall be uniform, and the difference between the sound pressure level at each 9
GB/T 11469-1989
point and the specified value shall not be less than -2dB and shall not be greater than +4dB. b. White noise source
The noise octave spectrum distribution of the white noise source shall meet the requirements of Figure 3. Sound pressure level intensity dB
c. Test instruments
Microphone, frequency band analyzer, sound intensity meter. 4.3.8.2 Initial test
Same as 4.3.2.1.
4.3.8.3 Test procedure
200202
Noise octave spectrum curve
Hang the altimeter transceiver or indicator in the center of the test room with four springs or rubber ropes. The natural frequency of the suspension device shall be lower than 25Hz and no additional vibration shall be brought. Each surface of the transceiver or indicator shall be exposed to the sound field. b. Introduce the noise into the test room for 30 minutes of vibration. 4.3.8.4 Intermediate test
According to the product standard.
4.3.8.5 Final test
Take out the transceiver and indicator from the test room for performance inspection. They shall meet the requirements of 3.2.2 to 3.2.7, and their appearance and structure shall remain intact.
4.3.9 Explosive atmosphere
4.3.9.1 Fuel mixture: Mix the fuel by mass according to 13 parts of air and 1 part of fuel, and use gasoline with a fuel value of 100/130. 10
GB/T11469—1989
4.3.9.2 Place the altimeter, which is electrically connected in normal working state, in the test box, and remove or loosen the outer shell to facilitate the penetration of the mixed gas. Seal the test box and raise the air temperature in the box to 71°C. If the temperature that may be generated by the altimeter during operation is lower than 71°C, raise the temperature in the box to the highest temperature that may be generated when the altimeter is operating. Before the mixed gas is injected, the temperature of the test box wall is allowed to be higher than the air temperature in the box by less than 11°C to prevent gasoline from condensing. 4.3.9.3 Inject the required amount of gasoline (calculated according to the air volume and air temperature in the test box) into the box and allow 3±1min of vaporization time.
4.3.9.4 Turn on the power supply of the altimeter and make the altimeter work in various states. 4.3.9.5 If the altimeter causes the gas in the box to explode, this test is considered to be unqualified and no further test is required. 4.3.9.6 If the altimeter does not cause an explosion, remove the altimeter and replace it with a spark gap or hot-wire ignition plug, repeat the above test, and use the spark gap or hot-wire ignition plug to ignite the mixed gas in the box to verify the potential explosion of the mixed gas in the box. If an explosion occurs, the test is valid, otherwise the test is invalid and the entire test is repeated.
4.4 Power supply change test
4.4.1 High voltage test
4.4.1.1 For an altimeter using a 27V DC power supply, adjust the input voltage to 29.7V and operate for more than 30 minutes. During this period, the altimeter should meet the requirements of Articles 3.2.2 to 3.2.7. 4.4.1.2 For an altimeter using a 115V AC power supply, adjust the input voltage to 120.8V and the frequency to 420Hz. The operating time is more than 30 minutes. During this period, the altimeter should meet the requirements of Article 3.2.6. 4.4.2 Low voltage test
4.4.2.1 For an altimeter using a 27V DC power supply, adjust the input voltage to 24.3V and operate for more than 30 minutes. During this period, the altimeter should meet the requirements of 3.2.2 to 3.2.7. 4.4.2.2 For altimeters using 115V AC power supply, adjust the input voltage to 109.2V and the frequency to 380Hz, and operate for more than 30 minutes. During this period, the altimeter should meet the requirements of Article 3.2.6. 4.4.3 Voltage reduction test
4.4.3.1 For altimeters using 27V DC power supply, add 27V test voltage, operate for 30 minutes, and then reduce the voltage to 21.6V. Then reduce the voltage to 13.5V at a voltage change rate of less than 2% per minute, and after working for 10 minutes, return to 27V. The altimeter should meet the requirements of Articles 3.2.2 to 3.2.7.
4.4.3.2 For altimeters using 27V DC power supply, add 27V voltage to start the altimeter, and then reduce the voltage to 13.5V and then to 0V at a voltage change rate of less than 2% per minute in this state. Check whether there are abnormal phenomena such as ignition and smoke. 4.4.3.3 For altimeters using 115V AC power supply, first adjust the voltage to 100V, 400Hz, and work for 30 minutes. During this period, the altimeter should meet the requirements of 3.2.2~3.2.7. 4.5 Reliability and maintainability test
Reliability and maintainability test shall be carried out in accordance with the method specified in the product standard. 4.6 Magnetic influence test
a. Place a free magnet (such as an uncompensated magnetic compass) in a test environment with uniform magnetic field strength and a horizontal component of 14.4A/m±10%. Place the altimeter on the east-west line passing through the center of the magnet according to the use status. b. Power on the altimeter and put it in a stable state that can produce the maximum magnetic deflection. Rotate the altimeter in the horizontal plane to find the position when the magnetic deflection is the largest. Keep this state and orientation, translate the altimeter to make it close to and away from the magnet, and read the magnetic deflection data and distance data at intervals. The distance should be measured from the center of the magnet axis to the nearest point on the altimeter surface: draw a magnetic deflection angle-distance curve, and determine the distance of 1° deflection of the magnet on this curve, which should not be greater than 0.3m; C.
d. If the horizontal component of the magnetic field strength in the test environment is not the specified value, the safety distance is calculated as follows: L=Lr.1.44
Where: L—safety distance, m,
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