Rhinelander

The company pilot and two employees had departed on an aerial imagery survey flight of forest vegetation. The airplane began to level off at an altitude of about 16,100 ft mean sea level (msl) and accelerated to a maximum recorded groundspeed of 209 knots. Less than 2 minutes later, the groundspeed decreased to about 93 knots, and the airplane descended about 500 ft while on a steady heading. The airplane subsequently entered a rapid descent and a right turn, and “mayday, mayday, mayday” and “we’re in a spin” transmissions were broadcast to air traffic control (ATC). A witness, who was located near the accident site, noticed the airplane nose down at high rate of speed and then saw the airplane spinning rapidly about its longitudinal axis. The airplane wreckage was located in remote wetlands and wooded terrain. Postaccident examination revealed that the airplane impacted the ground in a nose-low vertical attitude and at high speed. All major components of the airplane were located at the accident site. Examination of the airframe, engines, and propellers revealed no preimpact mechanical malfunctions or failures that would have precluded normal operation. According to the aircraft performance study for this accident, when the airplane pitched down, the normal load factor decreased rapidly from about 1.6 to less than 1 G. A rapid decrease in normal load factor is consistent with a stall when the wing exceeds its critical angle of attack. At that point, the air flow becomes separated at the wing, and the wing can no longer generate the necessary lift. If the airplane is in uncoordinated flight at the stall, a spin can result. Thus, the pilot likely did not maintain adequate airspeed, causing the airplane to exceed its critical angle of attack and enter a stall and spin. An important but unknown factor before and during the initial stall was the behavior of the pilot regarding his flight control inputs, including his possible attempt to recover. The airplane’s Pilot Operating Handbook states that spins are not authorized and does not include a procedure for inadvertent spin recovery.

The pilot reported that, upon reaching the decision altitude on a GPS instrument approach, he saw the runway end identifier lights and continued the approach. Shortly after, the lights disappeared and then reappeared. He continued the approach and landing thinking the airplane was lined up with the runway by using the runway edge lights for reference. Upon touching down about 225 ft left of the runway, the airplane dug into snow and flipped over, which resulted in substantial damage to the wings and tail. The pilot reported that there were no preaccident mechanical malfunctions or failures with the airplane that would have precluded normal operation.

There were five recorded transmissions of conversations from one of the pilots aboard the accident airplane and the Fort Dodge, Iowa AFSS; one on 12/27 and four on 12/28. The weather forecast for icing included wording such as '...moderate to isolated severe icing from seven thousand downward for your entire route of flight....' The pilot stated that he received 'Full Flight Service briefings...' and also indicated that he spoke to flight watch prior to takeoff. While executing the ILS approach to the destination airport, the pilot was unable to maintain the proper glidepath even with the application of full power. The pilot maintained marginal control of the airplane during the descent until impact with trees and the terrain about 10 miles west of the destination airport. The pilot and passengers reported 'vibration' and 'shudder' of the airplane prior to the impact. One passenger reported that she saw ice forming on the left 'rear' wings. Persons on the ground reported severe icing conditions around the time of the accident.

While on approach to Wausau-Waukesha Airport, one of the engine failed. The pilot lost control of the airplane that stalled, entered a spin and crashed few miles from the airport. The aircraft was destroyed and all three occupants were killed.

The crew (pilots and technicians) were engaged in a local test flight consisting of an electric equipment post maintenance check. After liftoff, while in initial climb, the seaplane encountered difficulties to gain height, stalled and crashed in flames in an open field. Both pilots were killed while three other occupants were seriously injured. The aircraft was destroyed.