POPLAR GROVE, IL, USA
N9581Y
BEECH E95A
THE PILOT DECLARED AN EMERGENCY WITH ATC AFTER EXPERIENCING WHAT HE BELIEVED WAS A LEFT ENGINE FAILURE. THE CONTROLLER GUIDED THE PILOT TO A NON-CONTROLLED AIRPORT FOR A LANDING. WITNESSES AT THE AIRPORT REPORTED SEEING THE AIRPLANE ENTER DOWNWIND FOR THE SOUTHEAST RUNWAY. THEY SAID THE AIRPLANE BEGAN A TURN FROM BASE LEG TO FINAL APPROACH. DURING THE TURN, THE AIRPLANE ENTERED A SPIN AND COLLIDED WITH THE GROUND. THE ON-SCENE INVESTIGATION REVEALED THAT ONE BLADE OF THE LEFT ENGINE PROPELLER BLADE HAD SEPARATED FROM THE ASSEMBLY. FURTHER EXAMINATION REVEALED THE SEPARATION WAS INITIATED BY A FATIGUE FRACTURE NEXT TO THE BLADE'S INNER CLAMP. TWO OF THE CLAMP SCREWS HAD FAILED DUE TO FATIGUE OVERLOAD. THE INNER CLAMP HAD BEEN ASSEMBLED WITH SCREWS THAT THE PROPELLER MANUFACTURER'S SERVICE BULLETIN SAID HAD TO BE CHANGED TO A DIFFERENT TYPE.
HISTORY OF FLIGHT On September 20, 1994, at 1735 central daylight time (cdt), a Beech E-95A, N9581Y, registered to Hectic Air, Incorporated of Wheeling, Illinois, and piloted by a multi-engine rated private pilot, was destroyed during a collision with terrain while on approach to Runway 12 at the Belvidere Airport, Poplar Grove, Illinois. The 14 CFR Part 91 personal flight was not operating on a flight plan. Visual meteorological conditions prevailed at the time of the accident. The pilot was fatally injured. The flight departed Waterloo, Iowa, at 1626 cdt. The pilot of N9581Y had been using the flight following radar services of the Federal Aviation Administration's Rockford, Illinois, Air Traffic Control Tower (ATCT). Approximately two minutes after ending the radar service the pilot contacted ATCT requesting an emergency descent to a landing due to a left engine failure. The pilot requested radar vectors to the nearest airport. The ATCT controller directed the pilot toward the Belvidere Airport at Poplar Grove, Illinois. Witnesses, about 3 to 4 miles south-southwest of the airport, stated they observed an airplane flying overhead that was wobbling as it headed northeast. Two witnesses observed pieces of the airplane detach from it and fall to the ground. These two witnesses stated they heard the airplane's engine sputtering and then saw the front of the airplane produce a large black cloud. Two witnesses at the airport said they saw N9581Y flying a downwind leg for runway 12. One witness said he heard only one engine running at what appeared to be partial power. Both said they saw the airplane begin a left turn to a base leg for runway 12, and it "...appeared to enter a stall/spin and descend straight down from an altitude of about 300-400 feet... ." A flight instructor at the airport stated he saw "...a twin on what appeared to be a close in downwind for 12." He said he "...had not heard any radio calls ... [he had the radio] volume turned low. Nevertheless, the traffic was not a factor." The instructor said he turned his attention away from N9581Y due to his instructing duties for a short time. He said he "...looked for the twin again, he was in spin directly in front of us approximately 1200 MSL." He said the airplane impacted ... the ground in a nose down attitude on the east bank of the creek." PERSONNEL INFORMATION The pilot's logbook showed a total time of 66.5 hours of multi-engine flight time. He had flown the Beech 95 a total of 62.5 hours. His logbook shows 10.0 hours of local dual, and 10.9 hours of cross country dual. A March 23, 1994, logbook entry showed he had receive dual instruction in single-engine landings. This instructional activity took place one day before his multi- engine private pilot checkride. According to the logbook the pilots multi-engine experience after receiving his rating was cross country flying in the Beech 95. AIRCRAFT INFORMATION N9581Y's annual inspection was concluded on May 18, 1994. At that time the airframe had 3,815.9 hours on it. The logbook showed a Hobbs meter reading of 740.8 hours. The right engine logbook had a serviceable part tag in it that had a May 21, 1990, date on it. The tag stated that the Hartzell propeller model number HC-9WK-2B, serial number 283F, had been overhauled. N9581Y's left engine had a 100 hour inspection on June 7, 1990. This logbook entry also stated the left engine propeller had been overhauled. An airframe total time was not shown in this entry a number, 158.0, was next to the word "tack." A copy of the left propeller work order dated May 3, 1990, showed the propeller was "O.H. per Hartzell O.H. Manual #109A." The work order also showed the facility had used an "Hartzell O.H. Kit TPI" during the propeller's overhaul. Propeller operating times (time since new or since last overhaul) were not found. The work order showed propeller blade serial number of B51780 and D7283 and Hartzell model and serial numbers HC-92ZK-2B and 940F respectively. These same serial numbers appear on the accident airplanes left propeller assembly. A serviceable part's tag found in the left engine logbook contained: The propeller's serial number, work order number, and overhaul completion date. These items matched what was written on the work order. WRECKAGE AND IMPACT INFORMATION N9581Y's wreckage was located on the east bank of north-south oriented creeks' east bank on an approximate 190 degree magnetic heading. The nose and front seat area of the cockpit was crushed upward and aft. The right wing was angled down into the creek and had mid-span, upward, twisting to its tip. Fuel was found leaking from the right wing fuel cell. An undetermined amount of fuel was observed in the left wing fuel bladder. The left wing was elevated about 5 degrees above ground level from the creek bank. The left engine had impacted the ground at an approximate 75 degree angle. It was found in that position with its forward section below the surface. The aft fuselage was elevated above the ground at an approximate 45 degree angle. The airplane was not equipped with front seat shoulder harnesses. The left engine lower cowl was not found at the wreckage site. The lower cowl was found in Belvidere, Illinois. Oil spray was on the left engine's upper and lower nacelle. The engine compartment and fire wall was oil covered. The propeller was attached to the engine and one of its two blades was missing. The missing propeller blade was found in Belvidere, Illinois. The missing propeller blade had broken away just outside the propeller hub, next to the blade clamp. Part of the blade was observed aft of the blade pin. This metal segment was bent aft about 5 degrees. The other blade was bowed forward about 2 degrees from hub to tip. The separated blade had white paint transfer marks on its front at the midspan and outer half positions. The attached blade was loose in the hub. The right engine propeller had one blade curved aft about 90 degrees from its hub. The second blade's outboard half was bent aft about 20 degrees. The blades were not in a feathered position. The left engine magneto switch was in the 'OFF' position. The right engine's magneto switch was in the 'BOTH' position. Both generator switches were in the 'ON' position. The right throttle was full forward and the left throttle was about 1 inch aft of the right throttle. Both propeller controls were positioned "full forward." All flight controls had continuity from the control yoke and rubber pedals to their respective control surfaces. The landing gear and flaps were in the retracted position. ADDITIONAL INFORMATION Hartzell Propeller Company produced 2 service bulletins on October 23, 1981, and August 27, 1982, (Bulletin No. 130 & 137 respectively) addressing the replacement of the propellers' inner clamp bolt. Bulletin number 130 stated, in part, "...any of these propellers ... must have all A282 inner clamp bolts replaced prior to return to service." Bulletin number 137 stated: "At the next overhaul, or at any point when the propeller is disassembled, replace all existing inner clamp bolts with the new A-321 inner clamp bolt." Both bulletins said that the replacement bolts must be green colored. A review of N9581Y's engine/propeller logbooks did not show compliance with Hartzell Bulletin Number 130 and 137. According to the FAA Principal Maintenance Inspector participating in the accident investigation, the propeller shop who overhauled the left propeller had its overhaul manual updated with Hartzell Service Bulletins, including number 130 and 137, at the time it was overhauled. The left engine propeller overhaul work order showed, under the "Part No. or Description" section, a "Hartzell Overhaul Kit TPI." A technical representative at Hartzell said the company had provided propeller overhaul kits for the Hartzell propeller model HC-92ZK-2B. He stated the kit is listed on Hartzell Drawing A2788 for the HC-92ZK-2B propeller. When asked what he thought the "TPI" represented at the end of the statement on the work order the technician said it may be an indication that the overhaul shop made its own overhaul kit up. He said many shops do this because they add items to the list of items making up a Hartzell Kit. The Hartzell produced overhaul kit list is appended to this report. The left propeller was examined at the NTSB's Office of Research and Engineering Laboratory. The laboratory examination revealed fatigue and overstress cracking on the propeller blade that had experienced an in-flight separation. No corrosion was found at the fatigue cracks origin point. The report said that fatigue cracking covered "... slightly more than half of the blade cross section... ." Examination of the propeller blades inner clamp screws revealed they had a bronze color coat. The two screws had broken while in the clamp. The screw surface examination revealed "...fatigue cracking that initiated in a thread root on one side of the screw." The report stated that the clamp screws on the propeller being examined were made in accordance with Hartzell P/NA-282 drawing. This drawing was replaced by P/NA321 in 1982. The threads on the A-282 screws were made by roll forming with heat treatment after rolling. The A-321 screws threads were roll formed after heat treatment. The pilot's autopsy was performed on September 21, 1994, by the Boone County, Illinois, coroner's physician Dr. L. W. Blum. The autopsy stated the cause of death was blunt force injury to head and chest. The wreckage was released to Mr. Steve Thomas President of Belvidere Aviation, Incorporated, on September 21, 1994.
Aircraft control not maintained by the pilot when he began his turn from base leg to final approach. Factors associated with this accident were the fatigue failure of a propeller blade, improper maintenance overhaul of the propeller, and a material defect in the propeller blade clamp screws.
Source: NTSB Aviation Accident Database
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