N7154ZPiper PA-18-150 · 1965

On August 31, 2024, about 1000 Alaska daylight time, a Piper PA-18-150 airplane, N7154Z, sustained substantial damage when it was involved in an accident near McGrath, Alaska. The pilot was fatally injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 business flight.

The airplane departed from a remote hunting camp and traveled to a 2,500-ft ridge about 3.5 miles away to drop off supplies to a hunting guide; the pilot was planning to continue to McGrath for fuel. According to the guide who was at the scene of the accident, the airplane flew over their camp several times before flying further up the ridge, where it executed several passes over the ridge. While the pilot had landed on this ridge in seasons past, this would have been his first time landing on the ridge this season.

The guide reported that winds near the accident site were about 15 mph from the northeast and the visibility was good. He reported that the airplane was traveling slow and low on a southwest heading and then it began a right turn to the northeast. As the airplane began what the guide thought to be a right base to final turn, he lost sight of the airplane. However, the guide reported that he could still hear the airplane’s engine. He reported hearing the engine “call for a lot of power” twice and a few seconds later he heard the airplane impact the ground.

The airplane was found nose down in a near-vertical attitude on a northeast heading on the south side of the ridge. The wings remained partially attached and the tail was bent slightly to the right.

Based on witness statements, as well as pictures and videos from the pilot’s website, the accident airplane previously had leading edge slats and slotted two-piece flaps installed from 2020 until sometime in 2023-2024 (see Figures 1, 2). The bolt pattern observed on the leading edges of the accident airplane’s wings resembled that of the Mackey Slats (see Figure 3). However, engine and airframe logbooks could not be located so exact details were not available.

Leading edge slats and slotted two-piece flaps change the flight characteristics of a conventional airplane by reducing the maneuvering speed. There is currently no Supplemental Type Certificates (STCs) for leading edge slats; therefore, airplanes with these installed are not approved for passenger-carrying operations.

The FAA was notified in October 2022 that the pilot may have been flying passengers in the accident airplane with the leading edge slats installed, and the FAA contacted the pilot regarding the installation of the leading edge slats. The pilot reported that he was helping a manufacturer obtain an STC for the leading edge slats and denied flying passengers with leading edge slats installed. The pilot/owner removed the leading edge slats sometime in the spring of 2024, after his interaction with the FAA.

A postaccident examination of the airframe and engine revealed no preaccident mechanical malfunctions or failures with the airplane that would have precluded normal operation.

Figure 1 Accident airplane with slotted two-piece flaps and leading edge slats

Figure 2 Accident airplane with leading edge slats

Figure 3 Leading edge slat attachment points on wing of accident airplane

On July 14, 2012, about 1515 Alaska daylight time, a float-equipped Piper PA-18-150 airplane, N7154Z, sustained substantial damage during a forced landing shortly after takeoff from a remote lake about 6 miles north of Kenai, Alaska. The airplane was being operated as a visual flight rules (VFR) cross-country personal flight under Title 14, CFR Part 91, when the accident occurred. The pilot and the sole passenger were not injured. Visual meteorological conditions prevailed, and no flight plan had been filed. The flight was en route to the Lake Hood Seaplane Base, Anchorage, Alaska.

During a telephone conversation with the National Transportation Safety Board (NTSB) investigator-in-charge (IIC) on July 15, the pilot reported that just after takeoff, as the airplane climbed to 100 feet above the water, the engine began to vibrate so violently that he was concerned that the engine may possibly separate. He reduced engine power, turned the airplane left to avoid trees at the departure end of the lake, and attempted an emergency landing on the lake. During the turn, the airplane continued to descend, and it subsequently collided with a shallow portion of the lake. The airplane sustained substantial damage to the wings, fuselage, and empennage.

The pilot reported that a postaccident examination revealed that a 6-inch portion of the propeller appeared to be missing. The pilot added that the remaining portion of the fractured propeller blade had a semi-circular hole that was consistent with a high caliber bullet hole. The pilot reported that the tip portion of the blade was not recovered.

The airplane was equipped with a McCauley, two-bladed, fixed pitch, metal propeller, model number DES1A175.

On July 18, the NTSB IIC examined the airplane wreckage after it was recovered to the owner's hangar in Anchorage, and confirmed that a 6-inch portion of one propeller blade tip was missing.

The NTSB IIC's examination revealed a semi-circular hole located at about 1/3 of the chord width from the trailing edge. The semi-circular hole measured about 1/4 inch in diameter.

During an interview with the NTSB IIC on July 18, the owner of the airplane reported that the propeller was the original propeller installed when he purchased the airplane in September of 2011. He added that there was no preaccident damage to the propeller.

A review of the accident airplane's maintenance logs revealed that the serial number of the propeller reportedly installed on the accident airplane did not match the serial number of the one actually installed. In addition, no log book entry was found that would have indicated any damage, repairs, modifications, or propeller assembly installations.

The accident sequence was recorded on the aft-seated passenger's iPhone, and a copy of that recording was sent to the NTSB vehicle recorder laboratory in Washington, DC for review. After a review of key events on the video recording, it was determined that neither the images, nor audio portion of the recording, offered any additional information that had not already been obtained from the pilot. No video group was convened, and no video transcript was created. A summary report of the video is included the public docket for this accident.

A sectioned portion of the fractured propeller blade was sent to the NTSB's Materials Laboratory for examination.

A senior Safety Board metallurgist reported that a magnified examination of the fracture face revealed a relatively flat fracture surface, with features consistent with fatigue progression through the aluminum alloys. He added that there was a nearly cylindrical hole, measuring about 0.3 inch in diameter, and oriented about 20 degrees from perpendicular to the flat side of the blade.

A scanning electron microscope (SEM) examination revealed fracture traces indicating fatigue initiation in the vicinity of the corners formed by the intersection of the hole and the flat side of the propeller blade.

When the portion of the propeller blade was received at the NTSB's materials laboratory, both sides of the blade section were painted black. The paint was removed, which revealed shiny surface markings and abrasion patterns, on both the camber and flat sides of the propeller blade. These marking were consistent with local abrasive reworking around the hole. The flat side of the propeller blade had heavy deep scratches in addition to a finely sanded ring around the hole. The unabraded surfaces of the propeller blade had a dull greenish grey appearance consistent with green primer paint. A closer examination of the camber side revealed two areas with a white opaque plastic-like filler material, which is consistent with automotive body repair fillers.

A complete copy of the NTSB's materials laboratory factual report is included in the public docket of this report.