Is it possible to log IFR currency in a flight simulator without an instructor?
UPDATE: 83 FR 30232, updated the requirements of 61.51(g) where an instructor is NO LONGER required to be present in order to log time in a flight simulator or aviation training device for instrument currency. Note that an instructor is still required in order to log simulator time that counts towards a rating or certificate and that a FAA approved device must be used. This particular change was effective July 27, 2018.



The following is no longer accurate, but retained for historical purposes:

There has been quite a bit of confusion in this area due to language in a preamble to the 2009 Final rule on Pilot, Flight Instructor, and Pilot School Certification, which implied that an instructor was not required for instrument currency and 14 CFR 61.51(g)(4) which says that an instructor must be present. I believe this all started with an email to John King of King Schools, where Lance Nuckolls at AFS-810 stated:


  ...approved uses for a BATD and an
  AATD are governed by § 61.4(c) and the LOA. The LOA states that an
  authorized instructor must certify the instructional use. Simply
  satisfying the requirements of § 61.57(c)(2) is not considered
  instructional use, therefore an authorized instructor does not need to
  be present. 


(Emphasis added)

Interestingly enough, the PDF of this email is no longer available on the King Schools website. Instead users are redirected to the Rebird TD page where it now implies that an instructor is required to maintain instrument currency.  A copy of the message text is available here.

Of course, this was too much of a good thing, so someone had to get the lawyers involved! In Keller (2010), the FAA's Office of the Chief Counsel made their opinion known:


  ...in order to log the time an instructor must be present to observe
  an individual using a flight training device or flight simulator to
  maintain instrument recency experience.


This position was reasserted in Stewart (2014), which references the Keller letter and explicitly cites 14 CFR 61.51(g)(4).

So we now have a situation where the FAA doesn't agree with itself! Whose opinion wins?  The lawyers', of course! In Perry (2010), the Chief Counsel's office states:


  ...where two interpretations address an identical scenario and reach
  an inconsistent result, the interpretation issued by the Assistant
  Chief counsel for Regulations takes precedence.


Some additional background:

I believe the author is referring to the Redbird Flight Simulations' FAA approval page where it states:


  When using the Redbird to maintain instrument currency an instructor
  is not required to be present. This has been discussed with and
  confirmed by AFS-810. A current Instrument pilot is not required to
  have an instructor on board the real aircraft to log approaches in
  IMC, therefore it follows that the FAA trusts a pilot to correctly log
  an approach preformed in the Redbird.


On its face, this statement appears to be in direct conflict with FAA's legal interpretation. Of course, one could try challenging this position (an interpretation is an opinion, after all), but it won't be me!