Originally Posted by HEATHROW DIRECTOR
When I was current I was never much in favour of clockwork mice charging about with Mode C showing because it was unverified and I might end up taking unneccessary action. However, I do appreciate that others have different opinions - maybe even the "book" tells you to do it nowadays.
HD, this is what the "book" (UKAIP) now says about SSR operation:
ENR 1.6.2 — SSR OPERATING PROCEDURES
1 General
1.2 In airspace where the operation of transponders is not mandatory, pilots of suitably equipped aircraft should comply with paragraph 2.2.2.
...
2.2 Mode A Conspicuity Code
2.2.1 When operating at and above FL 100 pilots shall select Mode A code 7000 and Mode C except:
(a) When receiving a service from an ATS Unit or Air Surveillance and Control System Unit which requires a different setting;
(b) when circumstances require the use of one of the Special Purpose Mode A codes or one of the other specific Mode A conspicuity codes assigned in accordance with the UK SSR Code Assignment Plan as detailed in the table at ENR 1-6-2-4 to ENR 1-6-2-8.
2.2.2 When operating below FL 100 pilots should select Mode A code 7000 and Mode C except as above.
So, it would seem, if we've got it, we should (but NOT must) use it ... although I do think your point about it not necessarily being verified is very pertinent.
JD
