My overall question is can a safety pilot log the entire flight, even when other pilot isn't under the hood, as total time? I have read several different things. Let's say the total flight time was 2.0 and the pilot under the hood was under the hood for 1.8. Can the safety pilot log the entire 2.0 as total time, 2.0 as PIC, or even 1.8 as PIC and 0.2 as SIC? There is the Hicks 1993 Legal Interpretation that says if the safety pilot is deemed as the “PIC responsible for the operation and safety of the aircraft during the flight” then the safety pilot can log the entire flight as PIC even when the pilot under the hood isn't under the hood, even when the pilot going under the hood is the sole manipulator of the controls.
But then there is the Trussell 2012 Legal Interpretation that isn't as detailed as saying the safety pilot is deemed PIC but just says that the safety pilot can only log PIC when the other pilot is under the hood.
So if we deem that the safety pilot is PIC then can the total time be logged as PIC for both pilots?
First, which of you was agreed to be the PIC for the flight? Unless one of you was an instructor giving training to the other, “deemed” isn't relevant – just what the two of you agreed. And whoever was agreed upon as the PIC has to be fully PIC-qualified and current.
If the PIC is the pilot flying under the hood, then the pilot flying, as sole log manipulator of the controls, logs PIC time for the whole flight, and simulated instrument for the hooded portion (as well as the landing and the instrument events). The safety pilot logs SIC time for the portion of the flight the pilot flying was under the hood. The safety pilot does not log the landings made by or the instrument flown by the pilot flying.
If the safety pilot is the PIC, then the pilot flying logs the whole flight as PIC time and all the landings and instrument events just as if they were the PIC. But when the pilot flying dons hood, the safety pilot becomes the PIC of an aircraft when two pilots are requires and thus can log PIC time for as long as the pilot flying remains hooded. However, even though the safety pilot IS the PIC for the whole flight, s/he cannot log PIC time when the pilot flying isn't hooded because absent the hood, there is no provision of 61.51(e) under which s/he qualifies to log PIC time.
The important concept is that logging PIC time is covered by one regulation (61.51(e)) but BEING the PIC is a separate issue covered by other regs. So you can BE the PIC without being able to LOG it as PIC time, and you can be able to LOG time as PIC time without BEING the PIC. Further, while only one person at a time can BE the PIC, you can have two people LOGGING PIC time simultaneously.
Clear as mud, right? But that third paragraph above is the one the must be understood to grasp the concepts involved.
There is also an unspoken question that needs to be addressed. Only one of the pilots on the flight may log cross country time. I mention this because most people working toward a Commercial Pilot certificate (or 135 job or an ATP) need Cross Country PIC time. That is the most common scenario for asking about logging time as a safety pilot (time building).
And that would be the pilot who flew the whole flight including the takeoff and landing.