1) Do you know what it is?
Yes
2) Do you have it?
No
3) Would you buy/fit it?
Probably not
4) If so, why, if not, why not.
- It's a bit more clutter in the cockpit.
- There's a danger it may give a false sense of security and keep eyes inside the cockpit rather than outside.
- Quite a few aircraft don't have transponder fitted or turned on.
- The perceived risk of a mid-air collision is greater than the US accident statistics show the real risk to be.
Aviation Consumer did a review of the top 10 safety investments sometime last year and the traffic warning boxes didn't make the list. In the US there are about 10 midairs a year and they have about a 50% survival rate. From memory, in the UK there seems to be about 1 a year with a similar survival rate. Put simply, there are a lot more common ways to kill yourself than hitting another aircraft, and you're better off spending the money trying to avoid those real risks.
The top ten most effective safety investments according to Aviation Consumer:
1) An instrument rating
2) A real, thorough flight review
3) Add a rating
4) Fuel totalizer
5) In-cockpit weather link
6) Progressive maintenance
7) Seatbelt harness for older aircraft
8) 406 MHz ELT
9) Cabin airbags
10) Vortex generators
It's interesting the top three are all pilot-training related.