Yes TW variante is grandfathered in both EASA & FAA systems not sure about cross crediting but “difference training” do not require an actual flight, a breifing with CRI or CFI could be enough?
PS: it gets interesting when talking about grandfathering tailwheel variante & difference training in single seaters but you can combine that with SEP & BFR signoff in double seats 
but “difference training” do not require an actual flight, a breifing with CRI or CFI could be enough?
What is there to grandfather in the FAA „system“?
How can someone obtain a differences training to fly conventional gear airplanes without a flight? Sounds like learning to surf by watching a PowerPoint presentation.
For FAA worth reading CFR 14 part 61.31 (h)(2)(I)(2)(i), I think the cutoff date is 1991 for “pressurisation” and “tailwheel” ?
https://www.law.cornell.edu/cfr/text/14/61.31
In EASA, there was a similar grandfather right but no cutoff date
How can someone obtain a differences training to fly conventional gear airplanes without a flight?
The initial context was grandfathering rights: someone did his PPL in Tiger Moth in 1970 and had 1000h PIC on it under ANO rules, does he legally need to fly dual and get a logbook signature for difference training to fly Cubs after 2012 with FCL transition? the obvious answer is NO
In addition, FCL does not even state actual flights are required for variants (TW, T, SLPC, VP, RG) difference training, maybe it was a typo
I snipped the following from an FAA instructors website.
Note that the applicable date to be grandfathered in is March 15, 1991 and therefore those with applicable experience logged before that date do not require an instructor endorsement.
Note also that FAA-H-8083-3 “Airplane Flying Handbook”, Chapter 15 covers transition to tailwheel airplanes.
Excerpt from AC-61-98A, Chapter 4, Section 16, TAILWHEEL AIRCRAFT
The general flight experience requirements specified in FAR Section 61.57 state that pilots who act as PIC of a tailwheel aircraft carrying passengers or certificated for more than one required pilot flight crewmember must have made three landings to a full stop within the preceding 90 days to maintain currency.
Under FAR Section 61.31, no person may act as PIC of a tailwheel airplane unless that pilot has received flight instruction from an authorized flight instructor who has found the pilot competent to operate a tailwheel airplane and has made a one-time endorsement so stating in the pilot’s logbook. The endorsement must certify that the pilot is competent in normal and crosswind takeoffs and landings, wheel landings (unless the manufacturer has recommended against wheel landings), and go-around procedures. The endorsement is not required if a pilot has logged flight time as PIC of tailwheel airplanes before March 15, 1991.
In addition to the requirements specified in FAR Section 61.31, the FAA recommends that pilots obtain a thorough checkout and transition training for each make and model of tailwheel airplane to be flown due to significant differences in operating characteristics of individual tailwheel airplanes. For example, many older types of tailwheel airplanes have pronounced or unusual stall and spin characteristics which differ greatly from those of more recently certificated tailwheel airplanes. In addition, many older airplanes may lack the comprehensive operating data and information typically found in pilot operating handbooks for comparable newer airplanes. Also, systems taken for granted in newer model airplanes may not exist in older aircraft, requiring a pilot to be familiar with unusual or seldom-used procedures. For example, the absence of electrical systems on many older aircraft compels the pilot to be familiar with hand propping procedures. The absence of attitude and heading gyroscopic instruments requires the pilot to depend more heavily on visual and other cues for basic aircraft control. Finally, the lack of radio equipment in many tailwheel airplanes obligates the pilot to be current in navigation by pilotage and no-radio traffic pattern procedures.
Additional factors may affect the instructional environment in tailwheel airplanes equipped with tandem seating. These factors may include reduced visibility from the rear seat, difficulty in communicating with the student due to seating position and higher noise levels, and lack of complete instrumentation or aircraft controls for the pilot
Additional factors may affect the instructional environment in tailwheel airplanes equipped with tandem seating. These factors may include reduced visibility from the rear seat, difficulty in communicating with the student due to seating position and higher noise levels, and lack of complete instrumentation or aircraft controls for the pilot in the rear seat.
Thanks for the FAA links.
In addition, FCL does not even state actual flights are required
Indeed it doesn’t. However, how can TW be learned other than flying in one?
how can TW be learned other than flying in one?
If you never been in one yes NFW you would go and fly without training & checkout, usually, the question of skipping TW sign-off did always come from people who had training & load of time on them before the new rules come up 
also, remember in Gliders, TMG and Microlights you don’t need TW but I don’t think it’s enough to skip a checkout in Pitts…
Ibra wrote:
Yes TW variante is grandfathered in both EASA & FAA systems not sure about cross crediting but “difference training” do not require an actual flight, a breifing with CRI or CFI could be enough?
Differences training does require an actual flight with an instructor. Familiarisation training, on the other hand, does not – nor does it require a logbook entry.
But yes, if you already have a pre-JAR/EASA logbook endorsement then it should still be valid.
Ibra wrote:
In addition, FCL does not even state actual flights are required for variants (TW, T, SLPC, VP, RG) difference training, maybe it was a typo
FCL says very little about differences training, but it has
Differences training requires the acquisition of additional knowledge and training on an approproate training device or the aircraft. (GM1 FCL.710 (b))
Of course training device does not imply “actual flights” but apart from that, I always read this to mean that actual flight was indeed required.
Ibra wrote:
In addition, FCL does not even state actual flights are required for variants (TW, T, SLPC, VP, RG) difference training, maybe it was a typo
It does!
GM1 FCL.710 Class and type ratings – variants
DIFFERENCES AND FAMILIARISATION TRAINING
(a) Differences training requires the acquisition of additional knowledge and training on an appropriate training device or the aircraft.
(b) Familiarisation training requires the acquisition of additional knowledge
ErlendV wrote:
endorsement pre-JAR/EASA, is it still «valid»?
Pre-JAR there was no such thing as a tailwheel endorsement in Denmark. Each pilot had a type card, and to start flying C172’s, I had to do a questionnaire and fly with an instructor, who then had to fill in a form and send to the CAA. So back then the CAA had a record of every single type for every single pilot.
The concept of differences trainings was introduced with JAR-FCL. I don’t recall any grandfathering procedure, but if you had BL8 on your type card (Bellanca w/ tailwheel), then you had the TW diff. training. P28R on the type card gave you VP and RG, and so on.
