IO540 – I wouldn’t have said that radar coverage is that spartan! Perhaps in the Highlands, North West of Scotland and parts of Wales, then yes. However, this is not where the majority of the traffic we are discussing, with regard to Mode S, operates.
Shortstipper - I’m not too sure there are that many types, even PFA or on Permits, that would be that financially hit to the extent that a basic Garmin GTX320A would render them grounded!! It’s all in context. Do you fly in controlled airspace frequently, mixing with the big boys, or in the open FIR at higher altitudes? If not, then why bother with such equipment?
Airliners are on very shaky ground when operating in the open FIR on a RIS, which is a very good reason to have a transponder. Recall incident with Flybe Dash 8 and a couple of Fast Blacks over the Irish sea?? I wonder how many times you have flown fairly close to the base of overcast cloud and never thought that something may be descending through it?? A transponder in this case would make you more visible to ATC (if within radar range which is very likely) and the a/c if TCAS was installed. In fact, it could save your bacon!!
Robin – You seem against the idea of having such equipment fitted to you’re a/c. Can I ask why?
The way that I look at transponders is in the realm of flight safety. It’s a relatively inexpensive bit of electronic magic, that when the proverbial hit’s the fan and you are getting even a FIS from a chap/chapess with radar, SAR will have an infinitely better chance of getting to you. Of that there is no doubt.