An EASA IR B1.2 engineer can certify ______.

The EASA IR B1.2 engineer is specifically trained and certified to maintain and certify aircraft, particularly those with piston engines. This qualification is part of the European Union Aviation Safety Agency's framework, which categorizes different classes of aircraft maintenance licenses.

The distinction between turbine-engined and piston-engined aircraft is significant within aviation regulations. Piston-engined aircraft operate differently than turbine-engined ones and require distinct knowledge and skills for maintenance and certification. Therefore, an EASA IR B1.2 engineer's ability to certify only piston-engined aircraft aligns with the specified scope of their training and regulatory limitations.

The other options include turbine-engined aircraft and helicopters, which are not within the purview of a B1.2 certification. Thus, it is not appropriate for someone with this specific qualification to certify anything beyond piston-engined aircraft. This highlights the importance of understanding the classifications and limitations imposed by aviation regulatory bodies when it comes to aircraft certification and maintenance.