Yoder, KS, USA
N232EM
Schleicher ASW-20
The experimental sailplane impacted an agricultural field after losing elevator control during initial climb on an aero-tow. Post accident examination of the elevator control system revealed the elevator Louis L'Hotellier ball and swivel joint had become disengaged, which resulted in the loss of elevator control. The Louis L'Hotellier fitting consists of a ball and swivel joint that connects the elevator control rod to the control surface. The purpose of the fitting is to allow the quick disassembly and reassembly of a sailplane. Several airworthiness directives (AD) have been issued for Louis L'Hotellier type fittings in order to "prevent the connectors from becoming inadvertently disconnected, which could result in loss of control of the sailplane or glider." The AD requires the lock plates to be secured either by a safety pin, wire, or other approved method. One specific AD further requires the installation of a placard that states, "All L'Hotellier control system connectors must be secured with safety wire, pins, or safety sleeves, as applicable, prior to operation." According to the pilot, he did not install a safety pin or wire on the elevator fitting prior to the accident flight. Additionally, he reported the sailplane was not equipped with the placard requiring a securing device to be used. The pilot was the owner of the sailplane. The pilot reported completing a "positive control check... although a second person was not available to help." The recognized method of performing a positive control check involves two individuals; one to hold the control surface stationary, while the other individual attempts to move the control stick.
On March 28, 2004, at 1520 central standard time, a Schleicher ASW-20 sailplane, N232EM, piloted by an airline transport pilot, sustained substantial damage during an in-flight collision with the terrain following a loss of elevator control on initial climb from Sunflower Aerodrome/Gliderport (SN76), Yoder, Kansas. Visual meteorological conditions prevailed at the time of the accident. The personal flight was operating under the provisions of 14 CFR Part 91 without a flight plan. The pilot was not injured. The local flight was originating at the time of the accident. According to the pilot, the accident occurred during his first soaring flight of the year. The pilot reported he assembled the sailplane and checked continuity of the flight control system during a "positive control check... although a second person was not available to help." The pilot stated that during initial climb while on aero-tow, he heard "a very loud pop in the very back of the sailplane" which was followed by a loss of pitch control. The pilot reported he immediately released from the towline and the sailplane continued to climb to approximately 100 feet above ground level where it began pitching down and descending. The pilot stated the glider impacted approximately 30-35 degrees nose down in a recently plowed, muddy field. The pilot examined the elevator flight control system subsequent to the accident. The pilot reported that the elevator's Louis L'Hotellier assembly was found disengaged, which resulted in the loss of elevator control. The Louis L'Hotellier fitting consists of a ball and swivel joint that connects the elevator control rod to the control surface. The purpose of the fitting is to allow the quick disassembly and reassembly of a sailplane. The accident sailplane was manufactured in Germany during March of 1978 and subsequently was imported into the United States. The Federal Aviation Administration (FAA) certified the aircraft as an experimental category sailplane. The FAA airworthiness certificate included specific operating limitations; one of which was that the sailplane had to be maintained "in accordance with the manufacturer's maintenance instructions." During 1993, the German aviation regulatory agency (Luftfahrt-Bundesamt) issued an airworthiness directive (AD) 1993-001 for Louis L'Hotellier ball and socket connectors. The original AD was expanded and revised in 1993 and 1998. The AD was issued in order to prevent the inadvertent disconnection of the Louis L'Hotellier fitting, which could result in a loss of aircraft control. The AD requires a safety pin to be placed though the locking plate. The pin prevents the locking plate from backing out and thus allowing the socket to inadvertently disengage from its corresponding ball. On April 2, 1997, the FAA issued airworthiness directive (AD) 97-08-06 for Louis L'Hotellier ball and socket connectors. The FAA subsequently revised the AD and issued AD 97-08-06 R1 on August 1, 1997. The AD was issued in order to "prevent the connectors from becoming inadvertently disconnected, which could result in loss of control of the sailplane or glider." The AD requires that either a safety pin or wire be placed through a hole in the locking plate. The safety pin or wire prevents the locking plate from backing out and thus allowing the socket to inadvertently disengage from its corresponding ball. The AD further requires the installation of a placard that states, "All L'Hotellier control system connectors must be secured with safety wire, pins, or safety sleeves, as applicable, prior to operation." The placard is to be installed within the "pilot's clear view." The AD further states that the AD is not mandatory for gliders and sailplanes that do not have US type certificates; however, the FAA "strongly recommends compliance." According to the pilot, he did not install a safety pin or wire on the elevator Louis L'Hotellier fitting prior to the accident flight. Additionally, he reported the sailplane was not equipped with the placard that was called for in FAA AD 97-08-06 R1. The pilot also was the owner of the sailplane. FAA regulation 14 CFR 91.7 states that no person may operate a civil aircraft unless it is in an airworthy condition. The regulation further stipulates that the pilot-in-command is responsible for determining whether an aircraft is in a condition for safe flight. According to the Soaring Flight Manual, published by the Soaring Society of America, "A thorough preflight inspection should be given to the sailplane after it is assembled. During this inspection, all fittings, attachments, and safeties should be checked carefully. A positive control check should also be performed to insure the controls are connected and travel freely in the proper directions." The manual reports the positive control check should be completed as follows: (1) Hold the control stick firmly in the neutral position (2) Have a ground crewman hold the control surfaces firmly as the pilot attempts to move the control stick The manual states that, "If the pilot is able to move the [control] stick while the control surface is being held stationary, the controls are not hooked up properly."
The pilot's failure to secure the elevator Louis L'Hotellier connector with a safety pin or wire as directed in several airworthiness directives and his inadequate preflight inspection of the sailplane, both of which resulted in the in-flight loss of elevator control due to the inadvertent disengagement of the elevator Louis L'Hotellier connector.
Source: NTSB Aviation Accident Database
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