Below is photo of AB-3 captured in Damascus on 06/12/13 (via Liwa al-Islam):
Below is photo provided for Chinese-sourced MD550:
Above motor inverted in relation to UAV airframe installation of similar powerplant seen in captured AB-3. Specifications, click HERE.
Below is photo provided for Iranian MADO MD-550 (Limbach L 550 E factory photo)
Above motor also inverted in relation to UAV airframe installation, sans optional cylinder "heat sinks,"with shown solid-state magneto units. Specifications, click HERE.