The following applies to aircraft under the purview of the FAA. Any differences in interpretation by other countries regulatory authorities is beyond the scope my own knowledge. However I would not expect European agencies to differ by much.
In the USA, there is no exemption from compliance with ADs. SBs and STCs may provide alternate means of compliance, but the AD must be complied with. The "smart stem" is an example of incorporating an STC to comply with the AD by an acceptable alternate means.
There IS an exemption mentioned in a Bombardier training document, but it is NOT an exemption from compliance with the AD. It is an exemption from a requirement that part 135 operators must consider tire pressure checking to be a maintenance function pilots cannot perform. The exemption states that when properly trained, part 135 pilots may perform the AD required tire pressure check. Pilots operating under part 91 have never been precluded by regulation from performing the check. There is an FAA legal council finding that checking tires is a "preventative maintenance" activity and therefore may be performed by pilots under the provisions of part 91. The exemption simply extends the permissibility of this activity to part 135 pilots with the approval of the required training and procedures by the certificate holders FAA inspection team. (POI/PMI)
I suggest that any Lear 60 pilots who have not done so already take the time to review the Bombardier training document on the subject.
The actual causes of the accident which precipitated this mess involve more factors than just the underinflated tires, but that was indeed the first link in the accident chain. T/R and FADEC logic with a disconnected squat switch combined with crew response issues round out the major holes in the cheese.
Shortly after that accident while undergoing recurrent training at Bombardier, we had the opportunity to recreate several variations of the accident scenario. (extra sim time at Bombardier's expense) Failed tires or not, this outcome simply should not have occurred.
Happy flying in the 60! It's a real pleasure to fly in spite of it's shortcomings.
westhawk