Lexington, KY, USA
N9985B
CESSNA 172RG
Upon arrival at the intended destination airport during an instructional flight, the pilot receiving instruction attempted to extend the airplane's landing gear. Only the nose gear and the left main landing gear extended and locked in the down position. Both pilots reported they attempted to retract the landing gear; however, the left main landing gear remained in the down and locked position and the nose landing gear's position could not be determined. The flight instructor reported that he performed the emergency gear extension procedure specified in the airplane's flight manual, but the right main landing gear did not extend or lock into position. The pilots elected to divert to a nearby airport. During the landing roll, the airplane veered off the runway, resulting in substantial damage to the elevator. An examination of the airplane revealed that a landing gear pressure hose had ruptured and the hydraulic fluid was depleted. It was constructed of material similar to that used in the automotive industry, thus, the hose likely was not an approved airplane part. No logbook entry was provided that disclosed when the hose was replaced or inspected. Because of the rupture, the lack of hydraulic fluid within the system precluded the right main landing gear from extending and locking as well as the left main and nose landing gear from retracting.
On November 14, 2012, about 1915 eastern standard time, a Cessna 172RG, N9985B, was substantially damaged while landing after diverting to Blue Grass Airport (LEX), Lexington, Kentucky. Night visual meteorological conditions prevailed and an instrument flight rules flight plan was filed. The certificated flight instructor (CFI) and private pilot were not injured. The airplane was owned by Christensen Aviation, Inc. and was operated by Eastern Kentucky University. The instructional flight was conducted under the provisions of Title 14 Code of Federal Regulations Part 91 and had departed from Madison Airport (I39), Richmond, Kentucky at 1730 with an intended destination of Warren County Airport/John Lane Field (I68), Lebanon, Ohio. According to both pilots, during the approach to I68, the left main and nose landing gear extended; however, the right main landing gear would not extend. An attempt was made to raise the landing gear; however, the left main landing gear and nose gear would not retract. Attempt was made to extend the landing gear with the emergency gear extension; however, no resistance was felt while manually pumping. Determination was made to divert to LEX to perform an emergency landing; upon landing, the airplane veered off the runway and came to rest in the grass. According to a Federal Aviation Administration inspector who examined the wreckage, the right stabilator was substantially damaged. Further examination of the hydraulic reservoir for the landing gear revealed that it was devoid of hydraulic oil. The airplane's landing gear system was examined and a hydraulic hose was observed with a full thickness rupture as well as evidence of hydraulic oil around the hose's rupture. Examination of the hose by the NTSB Materials Laboratory revealed the full thickness rupture and secondary parallel fractures, feather –like structures and micropeaks. The fractures were consistent with environmental stress crack growth. Examination of the stress crack growth revealed the initial fracture likely initiated on the interior near the collar on the fitting. Examination of the hose material revealed that it was a polyester/polyurethane co-polymer and the cloth sleeving material was consistent with polyester and contained similar characteristics of the polyester component in the hose material. The hose construction did not match any of the three specifications provided by the manufacturer, and had similar material makeup of hoses within the automotive industry. According to the airframe maintenance records, during a 100-hour inspection, on November 2, 2012 the landing gear retraction test was performed three times. During the same inspection the emergency landing gear extension was checked. Following the inspections the airplane was determined to be in an airworthy condition. According to the "Cessna 172RG Pilot's Operating Handbook", Chapter 7 "Aircraft & Systems Descriptions", states in part; "The landing gear extension, retraction, and main gear down lock release operation is accomplished by hydraulic actuators powered by an electrically-driven hydraulic power pack… a hand-operated hydraulic pump, located between the front seats, is provided for manual extension of the landing gear in the event of a hydraulic system failure. The landing gear cannot be retracted with the hand pump…" Chapter 3 "Emergency Procedures" contains a "Landing Gear Fails to Extend" checklist which defines the procedures as: 1. Master Switch – ON 2. Landing Gear Lever – DOWN 3. Landing Gear and Gear Pump Circuit Breakers – IN 4. Emergency Hand Pump – EXTEND HANDLE, and PUMP (perpendicular to handle until resistance becomes heavy – about 35 cycles) 5. Gear Down Light – ON 6. Pump Handle – STOW According to a Cessna Service Letter (SN85-54), dated November 27, 1985, the landing gear hydraulic system hoses were revised from a "5 year overhaul/replacement interval" to an "on condition overhaul replacement interval." According to the Cessna Aircraft Company Continued Airworthiness Program, the Hydraulic Hose was to be inspected every 1000 hours or every 3 years. The maintenance information provided to the NTSB could not accurately determine if the hydraulic hose had been inspected in the required time frame.
The rupture of the landing gear’s hydraulic pressure hose, which resulted in the depletion of all of the hydraulic fluid, and the inability of the landing gear to raise or lower. Contributing to the accident was the installation of an unapproved hydraulic hose by unknown maintenance personnel.
Source: NTSB Aviation Accident Database
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