The NTSB issued a full aircraft accident report https://libraryonline.erau.edu/online-full-text/ntsb/aircraft-accident-reports/AAR73-10.pdf for what seems to me to be a small general aviation crash. What I don’t understand is why it received this full report and not just a brief https://www.ntsb.gov/Pages/brief.aspx?ev_id=66900&key=0 like other such accidents
While at first glance this may seem like a garden variety GA crash, it is not. It has several factors that make it stand out well enough to conduct a full investigation, to find the actual reason for the accident among many possible factors, and thus make it possible to improve processes to avoid such accidents in the future.
Furthermore, the flight was "general aviation business flight", and while I'm not fully familiar with the regulatory basis for this kind of operations I'm gonna make a bold assumption this would somewhat fall into the category of professional aviation, further emphasizing the need to investigate the accident.
The specific points of interest, separating this accident from a common GA accident would be:
- flight being a "general aviation business flight" with two paying customers (my assumption)
- loss of all occupants, totalling three deceased
- flight conducted under IFR rules
- adverse weather condition, especially known icing enroute
- the fact that the weather conditions were brought to the attention of the pilot
- the plane not having de/anti-icing equipment, and thus no approval for flight into known icing (FIKI)
- the approach method being precision approach radar (PAR)
So the severity of the accident, and it being a "business flight" brought it into specific attention in the first place. Commercial/professional aviation has a lot to lose if the utmost standard in safety is not upheld. There were several interesting factors in the accident: poor weather, icing, no FIKI approval, despite of which the pilot set on the journey, PAR approach, which while generally being a safe procedure, can be very laborous to a pilot not well accustomed to it.
It was necessary to filter all the possible reasons and factors to come up with a definitive report on what went wrong, and how to avoid that from happening again.
Further reading on principles of accident investigation can be found in ICAO Annex 13: https://unitingaviation.com/news/safety/accident-investigation-provisions-of-icao-annex-13/