On December 1, 2024, at 1821 central standard time, a Piper PA-28R-200 airplane, N41997, sustained substantial damage when it was involved in an accident near Boscobel, Wisconsin. The flight instructor and pilot receiving instruction were not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 instructional flight. According to the flight instructor, they were established in cruise flight on the return leg of a night cross-country instructional flight at 9,000 ft msl, when they noticed an odor in the cockpit. The flight instructor noted no additional issues in the cockpit, and adjusted the cabin heat control, after which the odor diminished. The flight instructor then noticed an opaque windscreen and immediately thought they had encountered icing conditions. The flight instructor contacted ATC and requested a lower altitude. Using a flashlight, the flight instructor illuminated the windscreen and noticed a “brown river” completely obscuring their forward visibility. The cockpit engine oil pressure gauge indicated little to no oil pressure. The flight instructor declared an emergency with ATC and took over control of the airplane from the pilot receiving instruction. The flight instructor located the nearest airport to attempt a forced landing. However, due to restricted visibility due to the oil-covered windscreen, the airplane landed hard adjacent to the runway, bounced, and then came to rest upright on the ground. The airplane sustained substantial damage to the right horizontal stabilator, and the airframe contained engine oil on the top engine cowling, windscreen, and empennage. During recovery of the airplane, recovery personnel noted that the engine oil breather tube and alternate air outlet was obstructed by ice that accumulated during the flight (see Figure 1).

Figure 1. Ice-obstructed engine oil breather tube and alternate air outlet. (Source: Myers Aviation - Recovery Company) Additional postaccident examination of the engine revealed that the solid-ring crankshaft oil seal was extruded from the crankcase (see Figure 2).

Figure 2. Extruded crankshaft oil seal. According to the airplane manufacturer, Piper Aircraft, Inc., the engine oil breather tube should contain two secondary alternate air outlets that are located within the engine cowling area of the airframe. Additionally, the breather tube primary outlet should not extend beyond 0.5” outside of the engine cowling. The accident airplane’s engine oil breather tube, which was not a Piper Aircraft, Inc. part, contained one alternate air outlet that was fabricated about 1.5” from the end of the breather tube. The end of the breather tube extended about 3” outside of the engine cowling (see Figure 3).

Figure 3. Removed breather tube with alternate air outlet and location of engine cowling. A review of the maintenance records revealed that the engine oil breather tube was replaced (part number unknown) on December 18, 2006. No subsequent maintenance entries were noted that referenced any maintenance of the breather tube.