Accident Briefs: June 2017

Rush City, Minnesota

The student pilot was conducting a solo personal flight in the weight-shift-control aircraft. Video footage showed the airplane taking off, climbing to an estimated altitude of 300 to 400 feet, banking sharply left, descending, and then impacting terrain in a steep, nose-down attitude. The student did not have any solo endorsements on his student pilot certificate. The student had logged 14 hours in a different weight-shift-control aircraft but had never flown the accident aircraft type.

The student's flight instructor said that he did not feel the student was ready to fly solo and that he had not endorsed him for solo flight. He further stated that the student mismanaged takeoffs and landings and had the tendency to "leave the [control] bar out" after takeoff instead of letting it come back, which increased the aircraft's pitch attitude and caused it to climb too steeply. It is likely that the student increased the aircraft's pitch attitude too much during the initial climb, which led to his loss of aircraft control and an aerodynamic stall.

Probable Cause: The student pilot's failure to maintain the appropriate pitch attitude during initial climb, which resulted in an aerodynamic stall. Contributing to the accident was the student pilot's decision to conduct a solo flight without a solo endorsement in an aircraft in which he had no experience flying.

2 Nonfatal

Kewanee, Illinois

The pilot reported that, en route on an instrument flight rules flight plan in instrument meteorological conditions (IMC), the airplane began accumulating ice, and shortly thereafter, he requested a "precautionary diversion" to the nearest airport to land. The pilot further reported that he exited IMC about 1,642 feet above ground level and circled over the diversion airport for landing. He reported that he had kept the flaps and landing gear retracted "to not adversely affect lift" and forgot to extend the landing gear before landing. However, when the airplane was over the runway threshold he reduced power, which caused the auto-extend function of the landing gear system to attempt to extend the landing gear. During the landing roll, the right main and nose landing gear collapsed. The airplane gradually slid off the runway to the right.

The airplane sustained substantial damage to the right wing.

The pilot reported that there were no preaccident mechanical failures or malfunctions with the airframe or engine that would have precluded normal operation.

In the Procedures section of the Piper Arrow II Pilot's Operating Manual, it states in part: Some aircraft are equipped with an airspeed-power sensing system (backup gear extender) which extends the landing gear under low airspeed-power conditions even though the pilot may not have selected gear down. For normal operation, the pilot should extend and retract the gear with the gear selector switch located on the instrument panel, just as he would if the backup gear extender system were not installed.

The manual also states: The red gear warning light on the instrument panel and the horn operate simultaneously when: On aircraft equipped with the backup gear extender, when the system has lowered the landing gear and the gear selector switch is not in the down position and the throttle is not full open.

Probable Cause: The pilot's failure to extend the landing gear during the approach to land.

1 Nonfatal

Ionia, Michigan

The private pilot reported that, shortly after takeoff from a snow-covered runway, he heard a "thump" and saw that the left main landing ski tip had rotated up, past vertical, and was in contact with the left wing strut. He was unable to reposition the left ski into a normal position. Upon landing, the ski separated from the axle, the left gear leg dug into the snow, and the airplane rapidly decelerated before it nosed over.

As designed, the main landing skis are supported by two 5/32-in. braided steel cables and bungee/shock cords. Both ends of the steel cables terminate with a thimble-eye and a compressed/swaged nicopress sleeve. On the accident airplane, the forward and aft support cables had pulled through their respective nicopress sleeves where the cables attached to the left ski's tip and tail. The nicopress sleeves for the left ski tip and tail attachments were not located during the investigation. However, a postaccident examination of the remaining nicopress sleeves established that they were likely improperly formed with a 3/16-in swage tool instead of a properly-sized 5/32-in. tool. As a result, the steel support cables were able to pull through the inadequately-formed nicopress sleeves during the accident flight. It is likely that the aft support cable pulled through its nicopress sleeve during takeoff, which allowed the ski to rotate into a vertical position. The forward support cable likely pulled through its nicopress sleeve when the left ski separated from the axle during the subsequent landing.

The pilot reported that the airplane was typically equipped with snow skis during the winter. He purchased the main landing skis in used condition, with an undocumented service history, from an individual about 8 years before the accident. The forward and aft support cables were already fabricated and installed on the skis when they were purchased. Additionally, the pilot reported that the support cables had not been repaired or replaced since he owned the skis. The pilot, who was also an aviation mechanic, installed the main landing skis for the winter snow season 2 days before the accident. The accident occurred during the first flight since the skis were installed for the season.

Probable Cause: A failure of the aft support cable on the left main landing ski due to an inadequately formed nicopress sleeve, which allowed the ski to rotate into a vertical position shortly after liftoff, and its unavoidable separation during the subsequent landing.