In aviation, we have a term: Sterile Cockpit.
This means, during critical phases of flight, all attention is on the flight. There is no banter, paperwork, ipad/phone use, no programming the GPS, etc. Communication is only as necessary, which includes checklist and ATC calls.
Critical phases are Taxi, Take-off, and Landing. If you need to program the radios or GPS, you do it parked, or during cruise. Logbook info for the flight is after the engine is stopped. etc.
While it may be inconvenient, and consume extra time, it’s done this way for safety. When workload is higher, or when distraction is more likely to be hazardous, you reduce distraction.
An important point of this is that it applies to the Pilot In Command especially, and all crew generally. If you have a copilot, the SIC may be able to program the GPS / flight director, and handle ATC calls, while the PIC has eyes out of the plane.
At no time should the PIC be head’s down. If the PIC needs to go head’s down, then really, controls are transferred to the other pilot. That pilot, even if they are SIC, becomes PIC. This is why single-pilot operations have higher accident rates than dual pilot, even student+instructor.
When it’s a student and a Certified Flight Instructor (CFI), the instructor is the Pilot In Command. The only time a student can be PIC is when they are solo, or when granted PIC by an examiner.
The instructor is always responsible for the behavior of a pre-certificated student. Because of that, it is up to the instructor to never grant more authority to the student than they are capable of handling.
Most importantly, a CFI must never be heads-down. Being heads down is the same as letting them fly solo. Head-down, there is no way to see whether they are being safe. Heads-down is not instructing.
This all came about because a very experienced instructor was heads down, filling out a logbook, during post-flight taxi with a 23-hour student. The aircraft collided with a hangar that was fairly close to the taxiway. The instructor claimed it was the student’s fault; asked that the FSDO not be notified; claimed the student did not follow diretions; etc. This instructor has previously worked for the NTSB, and knows that damage to a wing spar from collision during taxi constitutes “substantial damage” and requires immediate notification as per CFR 830.
CFR 830: http://www.ecfr.gov/cgi-bin/text-idx?tpl=/ecfrbrowse/Title49/49cfr830_main_02.tpl
Safety Reporting: http://asrs.arc.nasa.gov/report/electronic.html