On September 25, 1997, at 1147 eastern daylight time (edt), an Universal Temco D-16, N110N, operated by a certified flight instructor, sustained substantial damage when the airplane's left engine was shut down for training. During the restart attempt, the left propeller would not come out of feather. Emergency landing gear extension was performed. During the subsequent emergency landing, the airplane's nose gear collapsed. Visual meteorological conditions prevailed at the time of the accident. The instructional flight was being conducted under 14 CFR Part 91. No flight plan was on file. The flight instructor and dual student reported no injuries. The flight originated at New Hudson, Michigan, at 1000 edt. In his written statement, the instructor pilot said he had shut down and secured the airplane's left engine as part of a final checkout flight he was giving to a student, prior to her taking her practical test for a multi-engine rating. During the restart attempt, the propeller would not come out of feather, and the engine would not start. The instructor pilot said that they had to manually pump down the landing gear, because the hydraulic pump for the gear was powered by the left engine. The three green lights, indicating that the airplane's landing gear was down and locked, did not illuminate. On their approach into Livingston County Airport, Howell, Michigan, the instructor pilot called the airport manager to visually confirm that the airplane's landing gear were down. The manager told the instructor pilot that the landing gear appeared to be down. By the time the instructor pilot and student received this information, they were too far down the runway to land, so they executed a go-around. The instructor pilot then took control of the airplane and brought it in for landing. During the touchdown, the landing gear collapsed. A Federal Aviation Administration (FAA) inspector examined the wreckage at the accident site. Both wings were bent down outboard of the engines approximately mid-way between the engine nacelles and the wing tip tanks, allowing the tip tanks to rest on the ground. The flaps were found partially extended. Both main landing gear struts were broken aft. The fuselage aft of the wings showed skin wrinkling. The nose wheel was found partially retracted in the wheel well. The right propeller showed chordwise scratches, torsional bending, and tip curling. The left propeller was found in the feathered position. Flight control continuity was confirmed. Examination of the engines, propellers, engine controls, and propeller controls revealed no anomalies. Examination of the airplane's normal landing gear extension system revealed no anomalies. Examination of the emergency landing gear extension system revealed that whenever flaps are selected during the hand pumping process, hydraulic pressure to the emergency landing gear system is interrupted, leaving the gear in an intermediate position. Hydraulic pressure is restored once flap extension/retraction is complete. The landing gear emergency extension procedure in the original pilot operating handbook for the airplane, made no reference cautioning pilots to not extend flaps when using the landing gear emergency extension procedure.