Below is a copy of an FAA Chief Counsel written opinion:

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Legal Interpretation # 92-52

October 30, 1992

Mr. David M. Reid

Dear Mr. Reid:

Thank you for your letter of June 12, 1992, concerning the logging of
pilot-in-command (PIC) time under the Federal Aviation Regulations
(FAR).

In your letter you ask four questions. First, you ask whether there
are "any circumstances when, during a normal flight, two Private Pilots
may simultaneously act as (and therefore log the time as)
Pilot-In-Command?" The answer is two private pilots may not
simultaneously act as PIC but they may, under certain circumstances,
simultaneously log PIC time.
There is a difference between serving as PIC and logging PIC time.
PIC, as defined in FAR 1.1, means the pilot responsible for the
operation and safety of an aircraft during flight time. FAR 61.51 deals
with logging PIC flight time, and it provides that a private or
commercial pilot may log as PIC time only that flight time during which
he is the sole manipulator of the controls of an aircraft for which he
is rated, or when he is the sole occupant of the aircraft, or when he
acts as PIC of an aircraft on which more than one pilot is required
under the type certification of the aircraft, or the regulations under
which the flight is conducted. It is important to note that FAR 61.51
only regulates the recording of PIC time used to meet the requirements
toward a higher certificate, higher rating, or for recent flight
experience.

Therefore, while it is not possible for two pilots to act as PIC
simultaneously, it is possible for two pilots to log PIC flight time
simultaneously. PIC flight time may be logged by both the PIC
responsible for the operation and safety of the aircraft during flight
time in accordance with FAR 1.1, and by the pilot who acts as the sole
manipulator of the controls of the aircraft for which the pilot is
rated under FAR 61.51. Enclosed please find two prior FAA
interpretations concerning logging of PIC time. We hope that these
will be of further assistance to you.

In your second question you ask "[h]ow shall two Private Pilots log
their flight time when one pilot is under the hood for simulated
instrument time and the other pilot acts as safety
pilot?" The answer is the pilot who is under the hood may log PIC time
for that flight time in which he is the sole manipulator of the
controls of the aircraft, provided he is rated for that aircraft. The
appropriately rated safety pilot may concurrently log as second in
command (SIC) that time during which he is acting as safety pilot.

The two pilots may, however, agree prior to initiating the flight that
the safety pilot will be the PIC responsible for the operation and
safety of the aircraft during the flight. If this is done, then the
safety pilot may log all the flight time as PIC time in accordance with
FAR 1.1 and the pilot under the hood may log, concurrently, all of the
flight time during which he is the sole manipulator of the controls as
PIC time in accordance with FAR 61.51(c)(2)(i). Enclosed please find a
prior FAA interpretation concerning the logging of flight time under
simulated instrument flight conditions. We hope that this
interpretation will be of further assistance to you.

In your third question you ask "[d]uring instrument training, how shall
a VFR Private Pilot log the following flight time: Pilot-In-Command
time, Simulated Instrument time, and Actual Instrument time, when that
pilot is ... A) ... under the hood? B) ...in actual instrument
conditions? C) ... under the hood in actual instrument conditions?"
The answer is the VFR private pilot may log all of the flight time you
described as PIC flight time under FAR 61.51(c)(2)(i) if he was the
sole manipulator of the controls of an aircraft for which he is rated.
Under FAR 61.51(c)(4) the pilot may log as instrument flight time only
that time during which he operates the aircraft solely by reference to
instruments, under actual or simulated instrument flight conditions.
Please note that the FARs do not distinguish between "actual" and
"simulated" instrument flight time. Enclosed is a prior FAA
interpretation concerning the logging of instrument flight time. We
hope this interpretation will further assist you.

Finally you ask "[d]oes FAR 61.57 affect how the VFR Private Pilot
shall log Pilot-In-Command time during instrument training, either
before or after meeting the 6/6/6 requirement, and if so, how?" FAR
61.57 does not affect how a pilot logs PIC time during instrument
training; FAR 61.51(c)(2) and (4) govern logging of instrument flight
time. FAR 61.57(e) provides currency requirements for acting as PIC
under instrument flight rules (IFR) or in weather conditions less than
the minimums for visual flight rules (VFR). Enclosed please find a
prior FAA interpretation on instrument flight time and FAR 61.57(e).
We hope this interpretation will further assist you.

We hope this satisfactorily answers your questions.

Sincerely,

/s/ Donald P. Byrne
Assistant Chief Counsel
Regulations Division