Mark An exception to what Tony submitted would be if you intended to fly, meaning the aircraft could fly, but you taxiied out, and during the runup found the engine running bad or rough, something like that, then taxied back in. That time also counts because you intended to fly and legally could. Taxi testing for the purpose of testing ground operations with no intent to fly can only be logged as total time experience, not as PIC. Most people don't do this because they want their single engine & if they have multi multi-engine experience to add up to equal their total time. E-mail off net if you want to discuss further.
Colin & Bev Rainey KR2(td) N96TA Sanford, FL [email protected] http://kr-builder.org/Colin/index.html

