What happened
The FAA’s narrative, in sentence case. The FAA writes it in capitals and removes private details.
Narrative: the Cessna hose clamp, p/n NAS397-34 failed to keep the carb. Air duct attached to the muffler shroud. It is suspected that the engine built up carb. Ice during the flight and the pilot was unable to get rid of it. This was a primary instructional flight. The CFI reported that while returning to the detroit city airport there was a drastic reduction in engine RPM. Carb. Heat was applied and no change in engine RPM was noted. The CFI applied full throttle and the engine lost more RPM, down to idle. An off airport landing was made on a factory service road. During the landing roll out the left wing and flap struck a sign post and received minor damage.
As the FAA filed it
NARRATIVE: THE CESSNA HOSE CLAMP, P/N NAS397-34 FAILED TO KEEP THE CARB. AIR DUCT ATTACHED TO THE MUFFLER SHROUD. IT IS SUSPECTED THAT THE ENGINE BUILT UP CARB. ICE DURING THE FLIGHT AND THE PILOT WAS UNABLE TO GET RID OF IT. THIS WAS A PRIMARY INSTRUCTIONAL FLIGHT. THE CFI REPORTED THAT WHILE RETURNING TO THE DETROIT CITY AIRPORT THERE WAS A DRASTIC REDUCTION IN ENGINE RPM. CARB. HEAT WAS APPLIED AND NO CHANGE IN ENGINE RPM WAS NOTED. THE CFI APPLIED FULL THROTTLE AND THE ENGINE LOST MORE RPM, DOWN TO IDLE. AN OFF AIRPORT LANDING WAS MADE ON A FACTORY SERVICE ROAD. DURING THE LANDING ROLL OUT THE LEFT WING AND FLAP STRUCK A SIGN POST AND RECEIVED MINOR DAMAGE.