Sorry, Christiaan, I was getting a bit tetchy.
This is an old UK CAA exam question, pre-1999, in the Radio Aids subject. There is some evidence that it was added to the JAA Central Question Bank early on and placed in the 022 Instrumentation section but I haven't seen it for years so, if it did get passed across, it seems to have been ditched fairly sharply. Personally, I think it was never transferred to the JAA Question Bank, it certainly isn't in the infamous 'Italian Feedback' which dates to around 2000.
We explored the answers to this with the UK CAA examiners 6+ years ago. They confirmed the Airbus view that civilian radio altimeters had a transmission pattern of 25º to 30º. Their standard textbook for the subject, Radio Aids by Underdown, was no help.
This question persists in 'school feedback' around Europe. The answers marked correct reflect the opinion of the instructor, not the examiner. I'm guessing that whoever told chrisbl that (a) was correct was taking their answer from military references.
Last edited by Alex Whittingham; 29th Aug 2006 at 09:11.