1、CEN PREN*3371 94 m 3404589 006222b 420 Edition approved for publication 1 994-0 1 -3 1 AECMA STANDARD NORME AECMA AECMA NORM C2 Chairman M. J. Le Cunff Comments should be sent within six months after the date of publication to AECMA Technopolis - 1 75, rue Jean-Jacques Rousseau 921 38 Issy-les-Mouli
2、neaux Cedex - FRANCE prEN 3371 Edition P 1 January 1994 EDITE PAR LASSOCIATION EUROPENNE DES CONSTRUCTEURS DE MATERIEL AROSPATIAL Technopolis - 175, rue Jean-Jacques Rousseau - F-92138 Issy-les-Moulineaux Cedex - Tl. (1) 47.36.98.76 UDC : Descriptors : Srie arospatiale Mtallisation Spcification tech
3、nique ENGLISH VERSION Aerospace series Electrical bonding Technical specification Luft- und Raumfahrt Masseverbindung Technische Lieferbedingungen This “Aerospace Series“ Prestandard has been drawn up under the responsibility of AECMA (Association Europenne des Constructeurs de Matriel Arospatial).
4、It is published on green paper for the needs of AECMA-Members. It has been technically approved by the experts of the concerned Technical Committee following comment by the Member countries. Subsequent to the publication of this prestandard, the technical content shall not be changed to an extent th
5、at interchangeability is affected, physically or functionally, without re-identification of the standard. After examination and signature of the AECMA Standard Checking Centre INPS) and formal agreement of the Official Services of the Member countries it will be submitted as a draft European Standar
6、d to CEN (European Committee for Standardization) for formal vote. Copyright Association Europeene des Constructeurs de Materiel Aerospatial Provided by IHS under license with AECMANot for ResaleNo reproduction or networking permitted without license from IHS-,-,-CEN PREN*337L 7Y 3404589 0062227 367
7、 Page 3 prEN 3371 : 1994 O Introduction This document has taken into consideration Stanag 3659. I Scope This standard defines the characteristics as well as the verification of bonding in on-board aircraft electrical systems. They refer basically to requirements relating to the effect of lightning,
8、return currents, electromagnetic interference, as well as to the accumulation of electrostatic charges and personnel shock hazard. This standard states the maximum permissible resistance values which guarantee, according to the installation, good conductivity of the whole of the structure, of the wh
9、ole installation and the bonding terminals; these values shall ensure correct operation of the systems. The rules of installation are defined in EN 3197. 2 Normative references EN 3197 Aerospace series - Installation of aircraft electrical and optical interconnection Stanag 3659 systems 1 Bonding an
10、d in-flight lightning protection for aircraft 2, 3 Terminology Chassis : represents the whole of the metallic parts electrically connected to each other, of a support or piece of equipment whose potential generally represents the reference potential (earth “O“ volt). Bonding : process of connecting
11、together metal parts so that they make low resistance electrical contact for direct current and low frequency alternating current. NOTE : necessary for getting a low resistant electrical current path. Grounding : the bonding of an equipment case, frame or chassis to an object or vehicle structure to
12、 ensure common potential. NOTE : necessary for getting a common potential, also for keeping up a common potential at a high electrical fault - or lightning strike caused - current by the means of low grounding resistant electrical current path which are equal to means for bonding. 1) Published as AE
13、CMA Prestandard at the date of publication of this standard 2) Published by : NATO, Military Agency for Standardization (MAS), BI 1 1 O BRUSSELS. Previous page is blank Copyright Association Europeene des Constructeurs de Materiel Aerospatial Provided by IHS under license with AECMANot for ResaleNo
14、reproduction or networking permitted without license from IHS-,-,-CEN PRENt3371 94 D 3404589 O062228 2T3 D Page 4 prEN 3371 : 1994 Earthing : the process of making a satisfactory electrical connection between structure, including the metal skin of an object or vehicle at the mass of earth to ensure
15、a common potential with the earth. NOTE : necessary for getting a common potential of the earth. Equipotential connection : an electrical connection which feeds the same potential to the elements of power production in addition to the other parts. Category I or II : the category I or II is determine
16、d by a common agreement between the aircraft manufacturer and the Official Services. 4 Primary bonding They comprise the whole of the conducting parts of the structure, of bonding parts and conductors which can be traversed by considerable energy (lightning discharge currents). 4.1 Main structure Th
17、e assemblies forming the structures are generally good conductors and allow the discharge of static charges and lightning currents. The structures are generally used as a return current path for the sum of the currents of the on-board electrical installation (for example : under a current of 300 A i
18、t is usual to measure resistance from 0,2 mR to 2 mR between two points about 30 m apart. 4.2 Detachable parts In principle, parts (non-articulated access doors, for example) attached by a significant number of metallic screws shall ensure good electrical continuity and shall not require the additio
19、n of bond braids. The metallic parts attached by quarter turn screws are bonded by suitable methods (braids, contact arms, interposition of conducting materials, etc.). 4.3 Articulated parts Parts which are articulated and placed permanently or temporarily on the exterior of the aircraft such as con
20、trol surfaces, doors, hatches, gear legs shall be correctly bonded, taking the following two points into consideration : - the articulation can be, by its construction, made sufficiently conductive even if it is lubricated, provided that the contact pressure is sufficient; - the articulation is not
21、conductive by the nature of its materials or protection used. In this instance, it is advisable to ensure bonding by a number of bond braids, ensuring redundancy and with the shortest possible length arranged so as to avoid any loop or risk of jamming during operation or by suitable means. Copyright
22、 Association Europeene des Constructeurs de Materiel Aerospatial Provided by IHS under license with AECMANot for ResaleNo reproduction or networking permitted without license from IHS-,-,-CEN PRENx3371 74 m 3404587 0062227 L3T m Page 5 prEN 3371 : 1994 4.4 Fuel tank covers and holes The design of th
23、e tank covers shall be such that there is no danger of inflammation of vapour, should lightning strike these covers directly. The refuelling and drainage holes, and air vents shall be carefully bonded. 4.5 Engines and auxiliary starter unit The main articulated attachments for the cooling system and
24、/or ball joints shall be shunted by a braid, unless the electrical continuity between engine and structure is permanently ensured by fixed attachment points. The fixed or moveable pipes shall also be bonded in relation to the jet engine either by construction or braids. 4.6 Non-metallic external par
25、ts The non-metallic components, especially in areas where there is high probability of lightning (radome, wing tips and extremities of stabilizer, fin, etc.) shall be correctly protected and bonded to allow electrostatic charges to be discharged and provide effective protection against the effects o
26、f lightning. 4.7 External protruding parts 4.7.1 shall be bonded to the structure at a point situated as close as possible on the aircraft skin. Internal metallic parts protruding on the exterior of the aircraft (Pitot tube, drain, for example) 4.7.2 Protruding parts connected to the on-board electr
27、ical circuit (sensors - Pitot tubes) Extremely good bonding is necessary to reduce possible damage to the on-board aircraft electrical system. 4.8 Ground connections Their composition, form, section, length shall be selected in relation to the result to be obtained (minimum bonding resistance). They
28、 shall be as short as possible. The choice of attachment points shall be such that the join is as direct as possible, avoiding loops. 1) The auxiliary starter unit is also designated APU (Auxiliary Power Unit) in this standard. Copyright Association Europeene des Constructeurs de Materiel Aerospatia
29、l Provided by IHS under license with AECMANot for ResaleNo reproduction or networking permitted without license from IHS-,-,-CEN PREN83371 94 = 3404589 O062230 951 Page 6 prEN 3371 : 1994 5 Secondary bonding There are several groups in this category : - electrical current returns by the aircraft str
30、ucture; - grounding of all metallic parts necessary for correct operation of electrical circuit protection; - the discharge paths for electrostatic charges; - the grounding of electrical shielding; - the dischargers of electrostatic charges; - the earthing of the aircraft on the ground; - the ground
31、ing of equipment to avoid electromagnetic interferences. 5.1 Return of electrical currents by the structure Grounding equipment or circuits Particular care should be taken concerning the quality of electrical contact to the structure. 4 The structural part on to which the bonding is made shall be ca
32、refully chosen. Ensure that the bonding points have adequate cross sectional area. 5.2 Grounding to avoid danger of electrical shock Electrical panels or other equipment accessible to the occupants of the aircraft (circuits with voltages of over 42 V) shall be bonded to avoid the danger of electrica
33、l shock. Articulated panels which are not detachable, attached by screws or similar metallic components, are only provided with braids if the contact ensured by the attachments is considered uncertain or inadequate. 5.3 Discharge of electrostatic charges The accumulation of significant electrostatic
34、 charges on the various metallic parts or insulators of the aircarft shall be avoided by ensuring correct discharge of these charges on the main structure of the aircraft. The electrostatic charges are discharged in flight by dischargers. The dischargers shall be fitted in sufficient number and adeq
35、uately located (because of their possible interaction with the aerial circuits) to ensure correct discharge into the atmosphere of stored electrostatic charges. Earthing of the aircraft on the ground shall be made using earthing contacts to discharge the static charges, unless the tyres are conducto
36、rs by design. The accessories and equipment, electrical or otherwise, shall be individually bonded. Copyright Association Europeene des Constructeurs de Materiel Aerospatial Provided by IHS under license with AECMANot for ResaleNo reproduction or networking permitted without license from IHS-,-,-CEN
37、 PRENa3373 94 3404589 O062233 898 Page 7 prEN 3371 : 1994 5.3.1 Fuel circuit The fuel circulation pipes shall be provided with bonding braids or be bonded by their attachment (support, clamp, etc.), the electrical continuity being ensured either by the attachment itself or by braids arranged upstrea
38、m and downstream from the attachments, or by a braid shunting the attachment. The refuelling accessories shall be bonded and very carefully connected to the aircraft structure. An aircraft ground connection shall be available for the refuelling tanker in close proximity to each refuelling point. 5.3
39、.2 Hydraulic circuits The hydraulic lines shall be grounded by : - their supports if bonded; - their bulkhead union connections; - the equipment to which they lead; - additional connections if required. 5.3.3 Flight controls and various mechanical controls Units which are operated by the occupants o
40、f the cabin (handles, pedals, control wheels, levers, seat and window controls, etc.) shall be bonded. 5.3.3.1 Pressurized area The metallic controls routed along the fuselage may be bonded solely at each of their extremities. Only the important parts included in these assemblies will be provided in
41、dividually with bonding braids or bonded by other means, thereby ensuring their grounding to the structure. 5.3.3.2 Non-pressurized area The parts in the non-pressurized area shall be subjected to the regulation for primary bonding. 5.3.4 Air conditioning, pneumatic and airspeed circuits The lines s
42、hall be grounded by : - their supports if bonded; - their connections, for example bulkhead union; - the equipment to which they lead; - additional connections if required. 5.3.5 Oxygen circuit The bonding of the whole circuit with the fittings and corresponding equipment shall be carried out thorou
43、ghly, to avoid risks of explosion in case of a defective hose or poor bonding. Copyright Association Europeene des Constructeurs de Materiel Aerospatial Provided by IHS under license with AECMANot for ResaleNo reproduction or networking permitted without license from IHS-,-,-CEN PRENa3371 94 3404589
44、 O062232 724 Page 8 prEN 3371 : 1994 5.3.6 External surface of the aircraft All the non-conducting components forming the external surface of the aircraft shall be treated to avoid the accumulation of electrostatic charges and to avoid interferences with radiocommunication and radionavigation. 5.4 E
45、quipment grounding to avoid interferences The values shall be taken from ground reference points or from the nearest structure. 5.4.1 The bonding of electrical equipment fitted on racks shall be ensured by at least one of the following methods : Equipment fitted in bays or on racks - bearing faces o
46、f the base plate of the equipment and the slide faces of the bay; - a pin of the equipment connector and by electrical cables of minimum section 0,60 mmz; - a bonding braid. The resistance values shall be determined in relation to the assembly mode as well as the length of the section of conductor c
47、onnected to the structure. In certain cases the grounding continuity may also be ensured by attachments on the brackets, the guide pins and by means of a conductor shunting the shock mounts. 5.4.2 Miscellaneous components Braids shall be provided when the attachments do not provide a good connection
48、 with the aircraft structure. 6 Measurement methods and bonding resistance limits Use the fixed method of resistance measurement - four points - where the current-carrying circuit is independent of the measuring circuit. 6.1 Primary bonding measurements The primary bonding measurements in tables 1 a
49、nd 2 shall be carried out on the assembled structure before installation of the different systems. For parts defined in table 1, the current and duration of the tests shall be defined by agreement with the Design offices. The bonding values shall be taken either between points A and B or from the ground reference point and B. In some cases the measurements in table 1 may be replaced by measurements taken between the different reference points of each main section.
