HIRF

Discu ss the method s of protection against HIRF and the checks/ inspection s whichwould be carried out after a fault was entered in the technical log.

HIGH INTENSITY RADIATED FIELD (FIRF) Discuss the methods of protection against HIRF and the checks/ inspections whichwould be carried out after a fault was entered in the technical log. I NTRODUCTION

High Intensity Radiated Field (HIRF) is produced by high energy systems located ont h e g r o u n d a n d o c c ur s a t a l l f r e q u en c i e s . I t a f fe c t s a n y e l e ct r o n i c a n d d i g i t a l systems on the aircraft, causing affected systems to operate erratically. P ROTECTION

Aircraft and systems can be protected against HIRF by proper shielding of cables,E M I f i l t e r s , g o o d b o n d i n g , e l e c t r o st a t i c d i sc h a r g e r. Proper termination of a i r c r a f t s y s t e m c o n n e c t o r s a n d s e a l i n g o f L R U s c o n d u c t i n g s u r f a c e o n windows, screening of cables.C HECKS

/I NSPECTIONS

If a fault had been entered in the technical log as HIRF I would make the aircraft safei n a c c o r d a n c e wi t h t he Ai r cr a f t Ma i n t e n an c e M a n u a l ( A M M ) a n d r a i s e a n y o t h er p a p er wo r k r e q u ir e d . I wo u l d a t t e m p t t o i s o l a t e t h e f a u l t , d e br i e f t h e a ir c r e w, i f necessary and confirm it is HIRF and not just a fault with the systems involved. Thetechnical log could be consulted to establish if there is a pattern of previous similar faults. If HIRF appeared to be the cause I would check the serviceability of EMIfilters, continuity check of shielding and bonding and carry out BITE (Built InTest Equipment) tests where possible to rectify the defect. And also check for the following: 

Detailed bonding resistance 

Using loop resistance tester to measure the loop resist a n c e / i m p e d a n c e measurement. 

Disassemble the connector to detect corrosion. 

A r r a n g e t o r e c o n f i r m l o op p o s i t i o n wi t h i n t he l i m i t . C a r r y o u t r e l a t e d s ys t e m functional test. C ERTIFICATION

Any work carried out would be recorded and signed as the job progressed. If anyi t e m s w e r e r e p l a c e d c r o s s c h e c k t h e E A S A F o r m 1 o r F A A 8 1 3 0 - 3 f o r i t e m s airworthiness conformity and would be attached to paper work, part numbers GRN’s,s e r i a l n u m b e r s o n a n d o f f w o u l d b e r e c o r d e d . C R S w o u l d b e i s s u e d b y a appropriately authorized engineer and a statement would be made in the technicallog to monitor the systems affected on the next flights. R EPORTING

As any occurrence of HIRF is an incident this must be reported to the CAA throught h e M a n d a t o r y O c c u r r e n c e R e po r t ( M O R ) s c h e m e . I wo u l d a l s o r e p or t i t t o t he organisation HIRF programme.