A discussion thread on r/flying raises a narrow but instructive question of FAA logging regulations: can a certificated flight instructor (CFI) log pilot-in-command (PIC) time while instructing in a tailwheel airplane if that instructor does not personally hold a tailwheel endorsement? The poster correctly identifies the controlling regulation, 14 CFR 61.51(e)(3), which permits a CFI to log PIC time while serving as "the authorized instructor in an operation" only if the instructor "is rated to act as pilot in command of that aircraft." Because a tailwheel endorsement is a prerequisite under 61.31(i) to act as PIC of a tailwheel airplane, an instructor lacking that endorsement is not "rated" to act as PIC of the aircraft in question, regardless of instructor certificate privileges. The poster's own analysis—that logging is prohibited—aligns with the plain text of the regulation and is the generally accepted interpretation among CFIs, DPEs, and FAA legal interpretations addressing analogous scenarios (such as high-performance, complex, or type-rated aircraft where the instructor lacks the required endorsement or rating).
This distinction matters for working CFIs, particularly those building time or teaching in aircraft outside their personal endorsement history, because logbook accuracy has downstream consequences well beyond academic correctness. Improperly logged PIC time can surface during an FAA check ride, an insurance audit, a 135/121 records check, or a certificate action investigation, and inconsistencies discovered later can jeopardize not just the flight time in question but the instructor's credibility on every other logged entry. CFIs routinely instruct in aircraft for which they hold instructor privileges but not the specific endorsement (tailwheel, high-performance, complex, high-altitude) needed to independently act as PIC—flight schools and clubs sometimes overlook this gap when pairing instructors with aircraft, especially in legacy taildraggers like Cubs, Champs, Citabrias, or Decathlons used for spin and upset training. The regulatory logic is consistent across 61.31 endorsements: instructing privileges under 61.193 do not substitute for the operating privileges required by 61.31, and 61.51(e)(3) explicitly ties PIC logging to the latter, not the former.
The practical workaround, well understood in flight training circles, is for the CFI to obtain the tailwheel endorsement before instructing in type, which is typically a same-day process involving a few hours of dual instruction from another qualified instructor. This is a low-cost fix relative to the regulatory and career risk of logging PIC time improperly, and it also ensures the instructor is genuinely proficient in tailwheel-specific skills (three-point and wheel landings, crosswind technique, ground-loop avoidance) before teaching them to a student—an important safety consideration independent of the logging question. Some instructors mistakenly assume that CFI privileges are universal across category and class once the CFI certificate itself is issued in category/class, but the endorsement requirements of 61.31 operate as a separate layer of privilege that follows the aircraft, not the certificate.
More broadly, this thread reflects a recurring theme in FAR/AIM literacy among CFIs and pilots pursuing time-building or additional ratings: the regulations governing logging (61.51) are frequently conflated with the regulations governing acting privileges (61.31, 61.3), when in fact they are interdependent but distinct frameworks. For check airmen, DPEs, and chief instructors reviewing logbooks, tailwheel and complex/high-performance endorsement gaps are a known area of scrutiny during stage checks and initial CFI hiring, and operators building out tailwheel or backcountry training programs should proactively verify that all instructing staff hold the relevant 61.31 endorsements before assigning them to those aircraft. As tailwheel and warbird/vintage aircraft training see renewed interest—driven by upset-prevention and recovery training (UPRT) requirements and general aviation's growing "stick-and-rudder" skills movement—this kind of regulatory precision will only become more relevant to instructors expanding into new aircraft categories.