Requirements for stray magnetic field testing of air cargo

    Since weak stray magnetic fields can interfere with the aircraft's navigation system and control signals, magnetic cargo is classified as Class 9 dangerous goods according to the International Air Transport Association (IATA) regulations and must be restricted during transportation. Therefore, some air cargo with magnetic materials (such as speakers, etc.) now needs to undergo magnetic testing to ensure the flight safety of the aircraft. This article briefly introduces and explains the stray magnetic field test and related requirements for air cargo.

    The main reference standards are:

    International Air Transport Association

    Packing instruction 902

    State variations: AEG-01. FRG-09, USG-12

    OPERATOR VARIATIONS: AM-09, JL-06,KZ-04,VN-11

    The limit requirements for stray magnetic fields are as follows:

    If the maximum magnetic field strength measured at 2.1m (7ft) from the object does not exceed 0.159A/m (200nt), the item is not restricted as a magnetic material and can be accepted as ordinary cargo.

    If the magnetic field strength at a distance of 4.6m from any point on the surface of the assembled goods does not exceed 0.418A/m (0.00525 gauss) or the magnetic compass scale deviation does not exceed 2 degrees, the goods can be accepted as dangerous goods. If this requirement cannot be met, the items cannot be transported by air, and the owner can entrust the goods to sea transportation.

    Testing method for stray magnetic field:

    Before magnetic testing, customers are required to pack the goods according to air transport requirements. The testing process itself will not damage the packaging of the goods. The goods are not unpacked during magnetic field testing. Only stray magnetic fields are tested on each side of each piece of goods. There are two specific testing methods, and you only need to meet any one of the test methods:

    Method 1: Use a magnetic field meter (measurement unit is A/m, or gauss), first find an area without any magnetic field interference except the earth's magnetic field, and two points on the east/west straight line with a distance of 2.1m, place the magnetic field meter at one point and reset it to zero, and then place the magnetic material to be measured at the other point. Finally, read the reading of the magnetic field meter and rotate the magnetic field cargo 360 degrees to find the maximum magnetic field strength value. If it is less than 0.159 A/m (0.002 gauss), it can be regarded as ordinary cargo. Otherwise, the distance between the two points can be increased to 4.6m and the above method can be used for measurement again. If the measurement result is less than 0.418A/m (0.00525 gauss), it can be regarded as dangerous goods transportation. Otherwise, rectification is required to meet the requirements.

    Method 2: Use a magnetic compass. First, find two points that are 2.1m apart in a straight line from east to west and in an area without any magnetic interference except the earth's magnetic field. Place the magnetic compass at one point and place the magnetic material to be measured at the other point. Finally, read the reading of the magnetic field meter and rotate the magnetic field cargo 360 degrees to find the maximum magnetic field strength value. If it is less than 0.5 degrees, it can be regarded as ordinary cargo. Otherwise, the distance between the two points can be increased to 4.6m and the above method can be used for measurement again. If the measurement result is less than 2 degrees, it can be regarded as dangerous goods transportation. Otherwise, rectification is required to meet the requirements.

    Measuring equipment requirements:

    According to regulatory requirements, the test equipment may use a magnetic field measuring instrument or a magnetic compass, but the conditions are:

    Magnetic field meter: minimum scale cannot exceed 0.0398 A/m (0.0005 gauss), tolerance range is between ±5%;
magnetic compass: minimum reading of 2 degrees, preferably less than 1 degree or lower;

    Correction method:

    If the test fails, rectification is required. The general rectification method is to shield the entire cargo or readjust the position of the cargo in the container.

    The above is a brief introduction to the stray magnetic field detection required by the International Air Transport Code.