Narrative of Events
During a training mission lasting 2 hours and 40 minutes, the pilot maintained a low power setting with the fuel mixture at full rich. After completing the mission, the pilot climbed the airplane to 9,000 feet above ground level (AGL) to clear obstacles on the route to the destination. During the subsequent descent, the pilot reduced power more rapidly than usual and descended faster than normal at approximately 180 knots indicated airspeed (KIAS). At an altitude between 800 and 1,000 feet AGL, while in the traffic pattern, the pilot applied power. Both engines then lost total power. The pilot set up a glide at 85 KIAS, completed emergency procedures, and retracted the landing gear. The engines did not restart. The pilot did not feather the propellers. Prior to touchdown, the pilot extended the landing gear but did not flare the airplane, resulting in the airplane colliding with the ground.
Examination Findings
During an examination of the engines, soot was noted on all spark plugs. However, both engines started and ran normally from idle to full acceleration during the test run.
Recommendations and Manual Notes
The engine manual and the Pilot's Operating Handbook (POH) recommend adjusting the fuel mixture for cruise flight. A note in the engine manual states that long descents at low power should be avoided because the engines may cool excessively and may not accelerate satisfactorily when power is reapplied. The POH recommends feathering the propellers and gliding at 120 KIAS in the event of a dual engine failure.