Even if an aircraft passes its EMC testing, as far as I'm aware, that testing is conducted on a 'fresh-out-of-the-hangar' aircraft. Whereas in-service wear-and-tear can cause other issues....
Couldn’t agree more.
Any comments or limitations in the RTS are based on the tail number presented to Boscombe for CAR Trials. To avoid testing every aircraft we have other processes for ensuring every tail number is, as far as reasonably practicable, to the same standard. Many of these come under the general heading “Quality Assurance” which is why QA is a vital core component of maintaining the build standard, in turn a prerequisite to airworthiness. What was happening to Director General Defence Quality Assurance at this time? That’s right, being disbanded. Waste of money. Instead of identifying problems before they reached the shop floor, in the space of a few months complete crap was being delivered from certain factories and ½ Line didn’t have the resources to make good the aircraft; or even know about the differences in the first place. In EMC terms, the problem manifested itself as inconsistent/non-compliant wiring and routing and, worst of all, appalling primary and secondary bonding. If you have a Nav problem, what does the book tell you to check first? Bonding.
I recall flying a rogue VC10K whose rudder pedals would tremble and CCTV screen would flare whenever a transmission (or even 'blip tuning') was made on HF/SSB. Basically a leaking antenna feeder cable induced transients into the yaw damper system (and, with autopilot engaged, the rudder pedals) - the CCTV flare was equally obvious as being proportional to transmitted audio level (and hence SSB RF modulation level).
Spot on. Steam driven HF Antenna Tuning Units and their 8 second tuning cycle. Screwed up everything in the aircraft.