Jonker Sailplanes Cc JS 1B N555AP

Summary

On 29 April 2012 at about 19:00 local time, a Jonker Sailplanes Cc JS 1B registered N555AP was involved in an accident near Clines Corner, New Mexico, United States. One person was on board and one had minor injuries. The aircraft was substantially damaged. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

29 April 2012 at 19:00

Classification

Accident

Location

Clines Corner, New Mexico, United States

Coordinates

35.2808, -105.8483

Aircraft

Jonker Sailplanes Cc JS 1B

Registration

N555AP

Category

Glider

Operator

Not recorded

Operating rule

Part 91: General Aviation

Purpose of flight

Personal

Phase of flight

Not recorded

Route

Moriarty → Moriarty

Aircraft damage

Substantial

Weather

VMC

Light

Day

NTSB number

CEN12LA265

1 person had minor injuries.

The fatigue failure of the rudder cable due to the inadequate design of the rudder pedal system.

Quoted verbatim from the NTSB record. This site does not paraphrase or interpret it.

Read the full NTSB narrative

While in soaring flight, the pilot heard a loud metallic sound come from the area near the rudder pedals and subsequently lost contact between his feet and the pedals, which resulted in a temporary loss of glider control. Although the pilot regained control of the glider, it was descending. When the glider had descended to about 10,000 feet mean sea level, the pilot chose to bail out with a parachute due to the descent rate and the unfavorable terrain for landing. The glider subsequently impacted a mesa and sustained substantial damage. Subsequent examination of the adjustable rudder pedal system revealed that the right rudder cable had fractured at the forward opening of the S-tube on the right rudder pedal. Examination of the rudder pedal design configuration revealed that full-forward deflection of the rudder pedal forced the cable to sharply bend at the point where it exited the forward opening of the S-tube, which was confirmed by a corresponding wear pattern on the accident glider’s S-tube. The repeated bending during normal operation resulted in the fatigue failure of 92 percent of the individual right rudder cable wires and, subsequently, final overstress failure of the remaining wires. After the accident, the owner of another glider of the same design examined the rudder cable on his glider and found similar damage to the cable. Subsequently, he conducted ground testing, which confirmed that repeated operation of the rudder pedals resulted in further damage to the rudder cables, indicating a progressive failure. Therefore, it is likely that the right rudder cable failed during the flight and resulted in the loss of rudder control. The glider manufacturer subsequently issued service bulletins and service letters to address the rudder pedal system deficiencies discovered during the accident investigation. Flight testing conducted by the manufacturer in an exemplar glider confirmed that the glider would have been controllable if the pilot had not chosen to bail. However, the flight testing was conducted under controlled conditions, and the test pilot was fully aware of the modifications made to the exemplar glider to simulate the cable failure. Further, despite these modifications, the test pilot was still able to fully control the rudder, if necessary, during the flight test. Since the accident pilot did not have knowledge of the nature of the control problem and did not have the ability to gain full rudder control, his decision to bail out of the airplane was understandable.

Quoted verbatim from the NTSB record.