The FAA says an airworthiness directive banning most early Cessna twins (except 337s) from flight into known icing is necessary because too many pilots were ignoring a mandatory service bulletin issued by the company in 1997 that says the same thing. Cessna sent out the bulletin after it became clear that even a little ice on almost 7,000 of the twins (PDF) could seriously affect the slow-speed handling, resulting in a lot of hard landings. The problem persisted after the service bulletin and the FAA issued the AD to actually make it illegal to fly the aircraft into known ice. The AD affects 4,200 aircraft in the U.S., more than a third of which have anti-icing gear. It becomes effective April 7, 2014.
The AD mandates installation of a panel placard that also requires pilots to carry an extra 15 knots on approach if they encounter inadvertent icing. Several operators protested the rule, saying that with the proper training pilots could safely operate the aircraft in known icing. They also said the limitations could cost them millions of dollars in lost business, but the FAA rejected those arguments. It based its decision to issue the AD on analysis of 51 accidents over 30 years. Based on the assessment, the FAA says it believes the AD will prevent 1.5 accidents a year and save 1.2 lives a year.
