The U.S. aircraft register, updated daily
Special conditions · appliance

Special Conditions: Aero Propulsion, Inc., Piper Model PA28-236; Installation of Societe de Motorisation Aeronautiques (SMA) Model SR305-230 Aircraft Diesel Engine (ADE) for Full Authority Digital Engine Control (FADEC) System and the Protection of the System From the Effects of High Intensity Radiated Fields (HIRF)

Special conditions are rules the FAA writes for one design when the standard certification rules do not cover something new about it. These were published June 15, 2006 for Aero Propulsion. System: engine.

What it applies to

Applicant
Aero Propulsion
Makes
Piper
Models
—
Published
June 15, 2006
Effective
June 8, 2006
The FAA's document
On the FAA's site

The FAA's summary their words, unchanged

These final special conditions are issued to Aero Propulsion, Inc., for Piper Model PA28-236 airplanes with a Societe de Motorisation Aeronautiques (SMA) Model SR305-230 ADE. The supplemental type certificate for these airplanes will have a novel or unusual design feature associated with the installation of an aircraft diesel engine that uses an electronic engine control system instead of a mechanical control system. The applicable airworthiness regulations do not contain adequate or appropriate safety standards for this design feature. These special conditions contain the additional safety standards that the Administrator considers necessary to establish a level of safety equivalent to that established by the existing airworthiness standards.

Source: FAA special conditions (final) from the Dynamic Regulatory System; the Federal Register carries the same notices.