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On January 24, 2003, about 1626 Pacific standard time, a Beech 95, N2733Y, experienced the in-flight separation of one right engine propeller blade, which was followed by the engine dislodging from its firewall mounts. The pilot was unable to maintain controlled flight, and the airplane descended into a private residence in Rancho Cucamonga, California. The sole occupant in the house was not injured. The airplane was destroyed, and its private pilot, the sole occupant in the airplane, was fatally injured. The pilot co-owned and operated the airplane. The personal flight, which was reportedly the first following maintenance, was performed under the provisions of 14 CFR Part 91. Visual meteorological conditions prevailed, and no flight plan was filed. The flight originated from the (uncontrolled) Cable Airport, Upland, California, about 1620.
The airplane departed from runway 24 and climbed to about 4,500 feet mean sea level. A pilot who was flying in the area observed the Beech and noticed it suddenly made a steep turn. Subsequently, the airplane descended. Several ground-based witnesses who noted smoke trailing from the airplane observed the descent. One witness reported observing the right engine hanging straight down toward the ground with the propeller stopped. Thereafter, the airplane rolled over until becoming upside down, and it dove straight toward the ground. Several other witnesses also reported observing the airplane in a steep right bank turn and then a nosedive toward the ground. The airplane's descent terminated when it impacted a house in a near vertical nose down attitude.
A single family residence was partially destroyed.
The pilot held a private pilot certificate with airplane single and multiengine land ratings. He also held an aircraft repairman certificate, which was issued on January 6, 1998. The repairman certificate was valid for troubleshooting, inspection, and maintenance of aircraft, airframe, and engines while employed by Foothill Aircraft Sales and Service, Inc., Upland. The pilot's previous aircraft repairman certificate was issued on July 24, 1981.
The pilot's flight time and currency information was provided by acquaintances of the pilot and by the Federal Aviation Administration (FAA). The pilot's personal flight record logbook was not provided for examination, and his recent flying experience/currency was not confirmed.
The pilot's flight hours reported herein are derived from the aforementioned sources and Safety Board investigator estimates. Acquaintances reported they believed the pilot's total flight time was about 3,000 hours; his flying activity during the preceding 90 days was 40 hours, and his experience flying the Beech 95 was 25 hours.
According to FAA airmen medical records, on medical certificate applications dated 9/19/2002, 7/3/2000, and 4/14/1998, the pilot reported that his total flight times were 3,000, 1,200, and 1,800 hours, respectively. On these dates, the pilot also reported that his flying activity during the preceding 6 months was 80, 15, and 10 hours, respectively.
The Beech 95 (Travelair), serial number TD-72, was manufactured in 1958, and was issued a standard FAA airworthiness certificate. The airplane's two 180 hp Lycoming O-360-AIA engines are equipped with 2-bladed, single acting, hydraulically operated, constant speed, full feathering Hartzell propellers, model HC-92ZK-2. The propellers are manufactured with 8447-12(A,R) blades (Z-shank). This designation identifies them as steel hub, single shoulder blades with internal bronze bushings. Z-shank blades are manufactured from a one-piece aluminum forging. The hub and blade clamps are steel.
Oil pressure from the propeller governor is used to move the blades to the low pitch (blade angle) direction. Blade mounted counterweights and feathering springs actuate the blades towards the high pitch/feather direction in the absence of governor oil pressure. Propeller rotation is clockwise as viewed from the rear.
The National Transportation Safety Board investigator reviewed the airplane, engine, and propeller logbooks provided by the airplane owner's attorney and by the owner of T & W Propellers. In pertinent part, airplane logbook No. 1 indicates that, in 1988, the left engine was equipped with propeller hub serial number (S/N) 279F. The right engine's propeller hub was S/N 282F. The left engine's propeller blade S/Ns were 113573 and 114546. The right engine's propeller blade S/Ns were 114565 and 114356.
Subsequently, the left engine's hub was changed, and the two propeller blades on each of the hubs were also changed. According to the airplane's maintenance records, on the accident date the airplane was configured as follows:
Left Engine, per Foothill Invoice number 5708: S/N RL-1280-36
Total Time on the Factory Remanufactured Engine: 6,668 hours
Hartzell Propeller HC-92ZK-2A; Blade Design 8447-12A
Hub: S/N 481F
Blades Marked: S/N A49334 and S/N A49352
Right Engine, per Foothill Invoice number 5708: S/N L-501-36
Total Time on Engine: 2,383
Hartzell Propeller HC-92ZK-2B; Blade Design 8447-12R
Hub: S/N 282F
Blades Marked: S/N C36230 and S/N C36547
NOTE: During the wreckage examination the above listed hub/propeller assemblies were found attached to the opposite engines. The right engine's propeller hub bore S/N 481F. The butt end of the blade shank fragment that remained clamped in the hub (from the separated blade) was found stamped with S/N A49334. (In this report, this failed blade is referred to as blade "R1.") These reversed positions were not documented in the airplane logbook. No explanation was provided by maintenance personnel regarding this discrepancy.
According to the Hartzell participant, Beech 95 series aircraft are approved with either 8447-12A or 8447-12R blade designs. The only difference is the blade tip shape; the -12R blade has a round tip with a relatively large tip radius. The propeller positioned on the left engine was found to have -12R blades, and the propeller positioned on the right engine had -12A blades, with a less circular tip shape.
Propeller Maintenance History.
On December 3, 1996, the airplane received maintenance. As indicated on Foothill Aircraft Sales & Service, Inc., invoice number 1148, at a tachometer time of 1,035 hours, the propellers were removed from the airplane and sent to Southern California Propeller Service (SCPS), which operated an FAA repair station under certificate No. VXSR617L. On Foothill's invoice number 1597, at a tachometer time of 1,435 hours, a notation appears indicating that per SCPS's invoice number 4639, the propellers had been disassembled and inspected. A notation was made that the blade shank inspection and compression roll was required every 500 hours.
On December 6, 1996, SCPS, made an entry in the airplane's propeller logbook. The entry indicated that the left engine's hub S/N 481F with blades S/N A49334 and A49352, and the right engine's hub S/N 282F with blades S/N C36230 and C36547, had been "COMPLETELY REPAIRED." The maintenance was also recorded with the same date on the "Overhaul Record" page in the logbook. Also, on the "AIRWORTHINESS DIRECTIVE AND SERVICE BULLETIN/LETTER COMPLIANCE RECORD" page, the following airworthiness directives were listed as having been complied with: 95-11-08 and 85-14-10R2.
According to an entry in the airplane's logbook, on December 6, 1996, the airplane received an annual inspection. Its total airplane time was listed as 9,221 hours. The next consecutive logbook entries were dated February 26, 1997; March 28, 1997; and May 23, 1997. These entries indicated performance of annual inspections. On June 10, 1997, the airplane received a 50-hour inspection. By this date the airplane's total time was listed as 9,679 hours.
The owner of T & W Propellers reported that on December 10, 1999, it received the aforementioned left and right propeller hubs and blades from the airplane's owner-operator, who requested that they be overhauled. T & W Propeller's owner provided the Safety Board investigator with documents indicating that his company completed the requested propeller overhaul on January 11, 2000. Thereafter, the hubs and blades were returned to the airplane's owner. The indicated time since overhaul (TSO) was recorded as being 0.0 hours.
According to the airplane's maintenance records, between May 14 and 15, 2002, the left propeller blades (from Hub S/N 481F) were installed on the airplane's left engine, and the right propeller blades (from Hub S/N 282F) were installed on the right engine. Both assemblies were dynamically balanced, and the engine was satisfactorily ground run tested. The listed time since overhaul was 0.0 hours.
Subsequently, the right hub and propeller assembly were returned to T & W Propellers for correction of a vibration problem. According to the propeller logbook entry, T & W Propellers checked the blade track, angles, and balance to repair the vibration. T & W Propeller's owner reported to the Safety Board investigator that his company did not disassemble the propeller from the hub. No discrepancies were noted. That was the last time he saw the propellers. It was his understanding that the following day the assembly was reinstalled on the airplane. The logbook indicates that the assembly was dynamically balanced and satisfactorily ground run tested. The listed time was 0 hours since overhaul. The airplane's total time was listed at 9,679 hours.
The airplane's maintenance record logbook indicates that the airplane's last annual inspection was completed on January 24, 2003, the day of the accident. The listed total airframe time in this logbook was still 9,679 hours. The time since the airplane's last engine and propeller overhauls was listed as 0.0 hours.
Airplane Total Time Determination.
The Safety Board's investigator's additional inquiry regarding the airplane's total time disclosed, on a printout entitled "Airworthiness Directive Compliance Record," dated January 17, 2003, that the airplane's Hobbs meter registered 5.0 hours. Also, the airplane's total time was listed on this record as 9,684 hours.
Acquaintances of the pilot reported that when a requisite amount of engine oil pressure is produced, the Hobbs meter may activate, and this may occur during ground engine operation. Some of the maintenance records indicated that the Hobbs meter was connected to an air switch.
The Safety Board investigation did not ascertain whether the accident occurred during the first flight following completion of the propeller and engine overhauls and the January 24, 2003, annual inspection, or whether it occurred during a flight commencing 5 hours thereafter. (See statements of Foothill Aircraft Sales and Service personnel for additional information regarding the airplane's maintenance and flight time history.)
In summary, by the accident date, it had been about 6 years and 463 (engine) operational hours since the propellers had received maintenance from SCPS. It had been about 3 years and 5 (engine) operational hours since the propellers received an overhaul from T & W Propellers.
The closest aviation weather observation station to the accident site is located at the Ontario International Airport, about 4.5 nm south (162 degrees, magnetic) of the accident site. In pertinent part, at 1553 Ontario reported the following weather conditions existed: wind from 260 degrees at 4 knots; 10 miles visibility; scattered clouds at 10,000 feet, broken ceiling at 20,000 feet; altimeter 30.04 inHg; and temperature 24 degrees Celsius.
FAA Quality Assurance personnel reported that no air traffic control communications or services had been provided to the accident airplane during its flight.
WRECKAGE AND IMPACT INFORMATION
A 2.5-foot-long portion of one of the two right engine propeller blades separated from the remainder of the propeller, which remained secured to the propeller hub assembly. The fragment impacted terrain about 1.2 statute miles northwest (304 degrees, magnetic) from the location where the main wreckage impacted into a private residence on Cathedral Court, Rancho Cucamonga. The global positioning system coordinates for the main wreckage were about 34 degrees 07 minutes 49.5 seconds north latitude by 117 degrees 36 minutes 33.9 seconds west longitude. The elevation is about 1,515 feet mean sea level.
Reports received from the San Bernardino County Sheriff's office indicated that at least six persons found debris from the airplane. The majority of the witnesses were located within about 0.25-mile from where the piece of propeller blade was found. In total, about 23 pieces of airframe components and engine accessory-related components were located in this area.
The main wreckage was observed in a near vertical nose down pitch attitude, and it had penetrated the roof of a 2-story house. The nose of the airplane was at ground level. The right engine was partially separated from its firewall attachment mounts and was partially ripped out of the airframe. The left engine was secure to the airframe. All flight control surfaces were present. A pool of fuel was present on the floor of the house, beneath and surrounding the airplane.
During the extrication of the airplane, the left wing was found separated from the structure outboard of the engine nacelle. The majority of the wing was destroyed, with the skin separated from the spars, and the leading edge was crushed and torn. Aileron control cable continuity was confirmed to the control linkage in the left wing. The engine and nacelle remained attached to the inboard wing portion that had remained partially attached to the fuselage. The nose of the fuselage was observed crushed in an aft direction, relative to the longitudinal axis of the airplane.
The left engine gauges were observed registering 36 inches of manifold pressure and 500 rpm. The right engine gauges were observed registering 41 inches of manifold pressure and 0 rpm. The fuel selector was on the main tank position. All of the empennage flight control surfaces, hinges, cables, and counterweights were found with the main wreckage.
The structure that attached the right engine to the firewall was found fractured. An oil residue was observed on the right horizontal stabilizer's leading edge, and on the stabilizer's upper and lower surfaces. The oil was noted dispersed in an aerodynamically streamlined direction. No similar oil residue was observed on the left side of the fuselage.
The landing gear was in the retracted position. There was no fire.
MEDICAL AND PATHOLOGICAL INFORMATION
The pilot's last aviation medical certificate was issued in the third-class on September 19, 2002. No restrictions were listed.
An autopsy was performed on the pilot by the San Bernardino County Coroner's Office on January 28, 2003.
The FAA's Toxicology and Accident Research Laboratory, Oklahoma City, Oklahoma, performed toxicology tests on specimens from the pilot. No evidence of carbon monoxide, cyanide, ethanol, or any screened drugs was reported.
TESTS AND RESEARCH
In pertinent part, the Lycoming Engine participant who examined the engines and attached propeller assemblies under the Safety Board investigator's direction and observation, indicated the following with respect to the left engine: (1) The two-bladed propeller remained attached at the crankshaft flange and exhibited bending signatures consistent with torsional deformation; (2) The propeller blades remained attached to the propeller hub, and the blades exhibited leading edge gouging, torsional twisting, chordwise striations and "S" bending; (3) The carburetor bowl, oil pressure screen and induction system were free of contaminants; and (4) The spark plugs exhibited coloration consistent with normal operation (reference Champion Spark Plugs "Check-a-Plug" chart).
In pertinent part, the right engine and the portion of the propeller assembly that remained attached to the engine was examined, and the following was noted: (1) The propeller blades with their respective clamp assemblies remained attached to the propeller hub. However, one of the propeller blades had separated a few inches outboard of the blade clamp; and (2) The observations regarding the left engine referenced above as numbers 3 and 4 were also found with respect to the right engine.
At the conclusion of the examinations, the Lycoming Engine participant opined that no evidence was noted of a preimpact catastrophic mechanical malfunction. (For additional details of the engine examinations, see the Lycoming Engine participant's Multiengine Final Report.)
On January 29, 2003, an initial optical examination of the broken propeller was performed by SEAL Laboratories, El Segundo, California. The examination revealed that the propeller exhibited a "fracture surface...[with] 'beach marks' indicative of a fatigue fracture." Corrosion pits were present.
On January 31, 2003, a teardown and inspection of the propellers was performed by the Hartzell participant under the supervision of the Safety Board investigator. In pertinent part, during this examination, the blades from the left propeller were found exhibiting rotational scoring signatures. According to the Hartzell participant, this indicated that the propeller had considerable rotational energy with power on at the time of impact. Neither of the right propeller blades was found bent, nor exhibited rotational signatures.
The Hartzell participant reported that the outboard area of the propeller blades, including the transition radius and the end face of the bore, is considered a critical load-bearing surface. Hartzell refers to this area as being "area A." Overhaul instructions caution against the introduction of stress raisers in area A, and a blemish or corrosion pit in this area that cannot be worked out by blending within specified limits is cause to scrap the blade. (For additional information regarding the area A designation, overhaul and inspection procedures pertinent to the accident model of propeller, see Hartzell Service Bulletin 136A, issued March 12, 1993.)
The Hartzell participant reported that because of its location inside the blade bore, area A is not accessible to inspection unless the propeller is disassembled. Therefore, unless the propeller undergoes an overhaul inspection, corrosion that develops in area A will likely remain undetected to failure. Hartzell instructions for continued airworthiness include a recommended time interval between overhaul (TBO), which Hartzell strongly encourages. However, most aircraft with Z-shank blade propellers are operated under Part 91 of the Federal Aviation Regulations, which do not require compliance with manufacturer recommended TBOs.
The recommended TBO for Hartzell propellers pertinent to the accident airplane is 2,000 hours of use or 5 years, whichever occurs first. According to the Hartzell participant, most Z-shank blade propellers are not maintained in compliance with recommended TBOs, and it is not unusual for Z-shank propellers to continue in service for 40 or more years without undergoing overhaul inspections.
During the Hartzell participant's teardown examination he made a series of observational findings. He observed the following discrepancies between the overhaul procedures specified by Hartzell in its maintenance manuals and the physical evidence found in the propellers:
1. The blade internal bores were clearly not in compliance with overhaul requirements for inspection, rework, and finishing. There was no paint and there appeared to be no chemical conversion coating in the bore area. There was extensive corrosion in the internal bearing bore area A, as defined by Hartzell Service Bulletin 136H. The participant stated that a proper overhaul requires removal of the blade bronze bushings in order to accomplish rework and inspection.
2. The hub arm of the right propeller had cadmium plating on top of deep corrosion pits. Such corrosion is required to be removed during overhaul.
3. A blade clamp in the right propeller had cadmium plating on top of deep corrosion pits. Such corrosion is required to be removed during overhaul.
4. Blades from the left propeller were too long. The aircraft is approved for installation of a propeller having a diameter of 72 to 70 inches. The length of blade L1 was measured to be approximately 32-5/8 inches long, which corresponds to a 74-inch diameter. Blades from the right propeller were measured to be approximately 31-5/8 to 31-3/4 inches, which is the correct length and corresponds to a 72-inch diameter.
5. Blades from the left propeller were impression stamped 8447-4 and 8447-12, and should have been stamped 8447-12R. Blades from the right propeller were impression stamped 8447, and should have been stamped 8447-12A.
6. Remnants of phenolic washers were found in the left propeller. The washers were approximately 1 to 2 inches in diameter and installed over the hub pilot tube, between the hub arm and blade butt of both blades. These were not Hartzell parts and such usage is not authorized.
7. Small particles, which appeared to be plastic cleaning media, were found in the grease in the blade balance hole.
8. The cadmium plating on the blade clamps and hubs was unusual. While much of the surfaces had bright cadmium plating, there were numerous spots that had no plating, areas of dull gray appearance, and areas that appeared worn. Portions appeared to have either deteriorated plating or had not been plated. Given the report that the propeller had only 5 hours of operation since overhaul, the general condition of the cadmium plating was considered very poor.
9. One 0-ring, used as a seal between the clamp and hub was severely deteriorated. It had many cracks around the circumference of the outside diameter. The other three blade clamp 0-rings were in good condition. It appeared that the deteriorated 0-ring had not been replaced during overhaul.
In conclusion, the Hartzell participant made the following statement regarding the observed overhaul procedure discrepancies: "The most significant discrepancy was the presence of obvious, significant corrosion in the internal bearing bore area of the blades. This, plus the absence of required corrosion protection (chemical conversion coating and paint) in this area, clearly indicates that proper overhaul was not accomplished."
Hartzell Service Bulletin 136H.
SB 136H states that during the cleaning and repair process of Z-shank blades "corrosion, scratches, scrapes, tool marks or pits may be present on the inside blade shank bore or bores and radius adjacent to the balance hole." The bulletin indicates that the following procedures are "REQUIRED ACTION" for a proper overhaul:
1. Remove all bearings, bushings in the blade pilot tube bore. Remove bronze bushings regardless of whether worn beyond limits. Removal is required in order to provide adequate inspection in the inner bearing radius (area A).
2. Clean the entire area of all grease, paint, and sealants.
3. Inspect the bore, including the bore's radii for surface blemishes, tool marks, scratches, scrapes, and/or corrosion.
4. Following rework and prior to performing a dye penetrant inspection, clean and etch the entire blade bore using sodium hydroxide and nitric acid. [Note: No alternate procedure or chemicals are authorized by Hartzell.]
5. Inspect for crack indications and corrosion pitting that holds dye penetrant.
6. Apply chromate conversion coating to bearing holes.
7. Paint blade pilot bore, area A, with wash primer, and then paint the primed area with Polane Black (black Polane is recommended, but gray is also authorized). "Paint helps to minimize corrosion in this critical area."
T & W Propellers Overhaul Procedures and NTSB's Inspection Observations.
The Safety Board investigator inspected T & W Propeller's repair station, and interviewed its owner and one of his repairman sons. In summary, the following was found:
Regarding specific work that T & W Propellers performed during the January 2000 overhaul, the owner said one of his sons actually performed the overhaul, including a dye penetrant inspection on the accident propeller. He stated that he checked his son's work. The owner also stated that each propeller is visually inspected using dye penetrant, and that an eddy current inspection may also be performed. He stated that at times he used a media blaster to assist in cleaning out the propeller bores. He acknowledged that he does not have sodium hydroxide or nitric acid at his repair station. The owner was asked to produce a series of manuals regarding the Hartzell overhaul procedures, and he indicated that some of the manuals were not presently available for review at his repair station. When asked about the manual's position on utilization of an eddy current inspection, he could not provide a Hartzell manual reference authorizing its use.
The Safety Board investigator interviewed the son who performed the overhaul on the accident propeller, and he made the following statements: In general, it is his procedure to look for corrosion when he inspects the propeller bore. If he sees corrosion, he removes the bushing to look for more corrosion. If he does not see corrosion, he does not always remove the bushing. He stated that the bushing is still in the bore when he inspects it with dye. Later, after reading SB136H during the lunch break, he changed his statement to say that he always removes the brass bushings when performing an overhaul.
The Safety Board investigator noted that the initials of the mechanic and inspector who performed and approved some of the work on the accident airplane's propeller blades (from Hub S/N 282F) were not, in all cases, written on the form. This omission is contrary to the requirements of T & W Propeller's "Procedures Manual." The owner acknowledged the error.
FAA Principal Maintenance Inspector (PMI) Responsibilities and Activity at T & W.
The PMI's work is directed by the FAA's "National Flight Standards Work Program Guidelines," Order Number 1800.56C.
In pertinent part, this order states that in order to ensure that the FAA fulfills its statutory and regulatory requirements, four major safety areas have been identified as critical to assure an overall level of safety within the aviation system. The four safety areas are listed in order of priority: surveillance, investigation, certification, and aviation education. Work performed in accordance with this order is recorded into the Program Tracking and Reporting Subsystem (PTRS).
Regarding surveillance, the order states, "one of the most significant duties of the FAA is to conduct surveillance in all areas of air transportation." The level of surveillance activities required by this order is considered a minimum, and accomplishment of these work functions is essential to provide a reasonable level of assurance of continued compliance with regulations, standards, and safe operating practices within the aviation community.
The FAA directs the activities of airworthiness inspectors who are responsible for the certification, technical administration, and surveillance of FAR Part 145 certificated domestic repair stations. Pertinent requirements for inspectors are published in Chapter 97 of Order number 8300.10, entitled "Airworthiness Inspector's Handbook."
The FAA assigned a PMI from the Riverside Flight Standards District Office to oversee T & W Propellers' operations, which were conducted under repair station certificate number T6WR776N. Since 1999, the same PMI has held this assignment.
The Safety Board investigator examined the PMI's surveillance activities regarding T & W Propellers, as recorded in the PTRS, from March 2001, to the accident date. In total, the records indicated that T & W Propellers had been inspected on four occasions. The two (2/7/2002 and 10/11/2002) required (R) inspections and the two (3/27/2001 and 10/15/2002) program (P) inspections had been completed. The PMI indicated in the PTRS record that T & W Propellers repair station was "satisfactory." No negative comments were indicated in the PTRS record.
The PMI stated to the Safety Board investigator that had any deficiency in the company's required operation been observed, he would have documented the finding in the PTRS record. Moreover, he considered T & W Propellers to be one of his better operators, and the company was in full compliance with applicable requirements.
Safety Board Materials Laboratory Propeller Examination.
The Safety Board's Washington, D.C., Materials Laboratory, examined the accident propeller assemblies. The following observations were made:
The blades had been marked R1 and R2 from the right (No 2) engine and L1 and L2 from the left (No 1) engine. Blade R1 was fractured near the butt end. Blade R2 was intact and straight. Blades L1 and L2 showed heavy curling deformation along with deep chordwise gouging and scratches indicating rotation at impact. All four blades were marked with drawing number "8447" and contained manufacturing features designating them as "Z" shank designs. However the right engine blades had square tips while the left engine blades had round tips.
Blade R1 was fractured approximately 4 inches from the butt end with the fracture passing through the pilot tube hole. Initial optical examinations of the fracture faces found characteristics of fatigue progression with the fatigue initiating from the pressure side of the bore of the pilot tube hole just outboard of the pilot tube bushing and inboard of the balance hole. The outboard portion of the pilot tube hole bore surface, including the transition radius and the end face, is referred to as area "A" by Hartzell. From initiation the fatigue propagated radially outward through the blade wall and circumferentially in both directions, penetrating about 60 percent of the local blade cross section before final overstress separation.
X-ray energy dispersive spectroscopy (EDS) and scanning electron microscope (SEM) viewing across this boundary did not find any major chemical or topographic differences.
The fatigue initiated at two sites of small corrosion pits in the pilot tube bore adjacent to the radius between the bore and the end face of the hole. Many additional corrosion pits were located circumferentially in line with the origin area, on the adjacent radius and bore surfaces, and on the end face of the pilot tube hole. The pits were filled with a dark material that appeared to be remnants of a coating or paint-like product, but the product was not consistent with the spectra of Polane paint.
SEM examinations also uncovered many unusual markings on the fracture surface that resembled sequential round indentations. The overlapping nature of these "peening tracks" indicated that they started from the bore surface and progressed outward as the fatigue crack propagated. Small spherical beads were found trapped on the fracture surface near the end of the tracks. Their appearance, composition (silicon, oxygen and calcium), and size were typical of glass beads used for blast cleaning.
The inner diameters of pilot tube bushings from four blades showed three distinct surface textures. The bushing from the fractured blade displayed a fine circumferential scratch pattern in the unworn areas. Additionally, this bushing had a continuous, deep, "Z" shaped gouge from the inboard edge along half the length. The unworn areas of the R2 blade bushing had a fine basket weave texture. Bushings from blades L1 and L2 had machined internal surfaces with deep spiraling grooves along their entire lengths.
The intact blades (R2, L1 and L2) were transversely and longitudinally sectioned to allow examination of area "A". No evidence of cracks was found, but corrosion pitting was observed on blades R2 and L2.
Visual examinations of area "A" in blade R2 found similar appearing but somewhat larger corrosion pits than in the fractured blade. These pits were also filled with dark material consistent with the material found in the pits of the fractured blade R1.
Blade L2 also contained many areas of corrosion pitting. These pits were located outboard of the fracture line in blade R1, in the radius and end face of the bore. On blade L2, the pits were clustered together and penetrated deeply into the blade material. No paint was found in these pits of blade L2 and the surfaces had a worn rounded appearance. Several pieces of foreign material were found in one of the pits. The material was slightly translucent and had a somewhat crystalline appearance. EDS found that the material contained a high carbon peak consistent with a plastic or other hydrocarbon material.
Somewhat similar translucent material (size and general shape) was found entrained in a grease sample removed from blade L1. This material was white in color and showed the high carbon peak found in the material from blade L2 but with considerably different trace elements.
Based on the surface finish of the blades and measurements made on molds of each hole, all blades appeared to have been reworked in area "A."
Hartzell Service Bulletin 136H allows removal of up to 0.010-inch of material per side to remove corrosion. The service bulletin also requires the reworked area to be chromate conversion coated producing a yellow to golden color and then painted with a wash primer and a topcoat of Prolane Black. None of the blades was painted, although a small area of a dark coating was noted on blade L1. Blades R2 and L1 also displayed areas with golden coloration, while R1 and L2 did not exhibit any coloration.
Propeller Repair Station History and Certificate Holder Information.
Safety Board investigator research revealed that on August 3, 1992, the individual who subsequently started and became the owner of T & W Propellers was listed on Southern California Propeller Service's (SCPS) FAA Form 8310-3, entitled "Application for Repair Station Certificate And/Or Rating" as being an owner or partner of SCPS. SCPS was located in Inglewood, Los Angeles County, California, and operated a propeller repair station. Based upon SCPS's location, the FAA's Los Angeles Flight Standards District Office was assigned direct oversight responsibility of SCPS.
While working at SCPS, the individual was active in the daily operation of the company, and he worked as its chief inspector. Records indicated that in 1996, SCPS terminated its association with this individual.
On June 16, 1998, after receiving multiple complaints spanning several years, the FAA revoked the SCPS propeller repair station certificate (number VXSR617L) due to improper maintenance and overhauls. The FAA reported in a Special Airworthiness Information Bulletin (SAIB No. NE-01-19, published March 20, 2001) that the improper overhauls showed corrosion signs, which could serve as the point of origin for cracks, and fatigue cracks that could propagate to blade failure, resulting in the loss of aircraft control.
About 17 months prior to the FAA's revocation of SCPS's certificate, on January 22, 1997, the FAA issued an Air Agency Certificate to T & W Propellers, located in Chino, San Bernardino County, California. (San Bernardino County is adjacent to Los Angeles County.) The FAA authorized the aforementioned individual's company to operate a repair station with the following ratings: "Limited Propeller, & Limited Specialized Service." The certificate had no expiration date. Based upon T & W Propellers' location, the FAA's Riverside Flight Standards District Office was assigned direct oversight responsibility for the company. State of California, Secretary of State, documents identified the aforementioned individual as being the president of T &W Propellers.
A review of FAA records further indicated that an examination of T & W Propellers' Operations Specifications, dated November 30, 2000, listed the following requirements: "The repair station certificate holder shall conduct operations in accordance with CFR Part 145" and with the issued operations specifications.
FAA records indicate that under T & W Propellers repair station certificate, the company was authorized to perform maintenance on (1) Sensenich propellers; (2) McCauley (constant speed and feathering) propellers; (3) Hartzell (constant speed & feathering, steel hub turbine, non-feathering, hydro-selective, 4-blade light weight turbine) propellers; (4) Dowty Rotol propellers; and (5) various Hamilton Standard propellers.
T & W Propellers' owner employed his wife as the office manager and their two sons in the daily operation of the company. The sons were trained by the owner/father and were responsible for performing repairs under the authority granted by their father, the repair station certificate holder.
Regarding the qualifications of the sons, in November 2001, T & W Propellers' owner wrote two letters to the PMI. Accompanying the letters were applications for repairman certificates for his sons. The sons reported that their experience had been, in part, acquired while being employed as propeller mechanics with SCPS from March 1992 to June 1996, and with T & W Propellers from November 1996 to the then current date, November 19, 2001. The father reported that the certificate applicants (his sons) had already been employed as propeller mechanics with his company, and that as repairmen they would have the duties and responsibilities to perform complete overhauls, modifications, and testing of Hartzell propellers, and propellers manufactured by other companies. The father also reported that the applicants were "fully qualified" to perform these assigned duties. The PMI issued the requested airman certificates in December 2001.
Safety Board Investigation of Other Overhauls Performed by T & W Propellers.
A. Two Propellers (4 blades), models HC92ZK-2B and HC92WK-2B, from Beech 95, N2620U, were examined by the Safety Board investigator at the facilities of American Propeller Service, Redding, California, on March 7, 2003. As indicated on the "Serviceable Part Tag" that accompanied the propellers, T & W Propellers had overhauled the propellers on December 29, 1997. The tag indicated that the propellers' total time since new was 2,500 hours, and the time since being overhauled (by T & W Propellers) was 0.0 hours.
The propeller owner's representative reported to the Safety Board investigator that, following this 1997 overhaul, neither propeller had been used. The propellers had been placed into storage. Because of the on-going activity with T & W Propeller, the representative desired to have the propellers examined prior to installing them on an airplane.
The following summarizes the Safety Board investigator's findings during the March 2003 inspection of the two propellers at American Propeller Service:
Evidence of corrosion was observed in area A of blades L1 and L2. The blade clamps exhibited moderate to deep corrosion pitting. Cadmium plating had been applied over the pits and was absent in certain areas. In certain areas there was an absence of conversion coating and Polane black paint. In the bore, particles were found that were consistent with glass bead material, and the particles were found in an area that should have been devoid of all foreign objects. Numerous additional discrepancies were documented regarding the propellers' assembly.
The above observations were made in conjunction with the American Propeller Service's chief inspector and an FAA representative from the Aircraft Certification Office, Propulsion Branch, Long Beach, California. Neither of the inspected blades was airworthy. (For additional information, see the Propeller Teardown Report, dated May 2, 2003.)
B. Between April 24 and 25, 2003, American Propeller Service examined propellers it had received from Air Combat, Fullerton, California. Maintenance records that accompanied the blades indicated that Air Combat's Hartzell propellers, model HC-C2YK-1BF, with blade S/N D78028 and S/N D93710, had been overhauled by T & W Propellers on March 14, 2002. Thereafter, T & W Propellers had provided Air Combat with a logbook entry stating, in pertinent part, that the propeller had been "Overhauled IAW Hartzell" manuals and Federal Air Regulations, and was found airworthy for return to service.
The records indicated that since the date of T & W Propellers' overhaul, the propellers had been operated for an additional 702.9 hours before being removed for inspection by American Propeller Service. Personnel at American reported the following observations after disassembly and cleaning of the blade balance bores: The bores exhibited bare aluminum in most areas with some evidence of a transparent green coating on a portion of the balance bore surfaces. The green coating appeared similar to zinc chromate primer. No chemical conversion coating or Polane paint was observed in the blade bore. The blades were deemed not airworthy and were scrapped.
C. On May 8, 2002, under the supervision of an FAA inspector from the Los Angeles Aircraft Certification Office, Propulsion Branch, an examination of a McCauley propeller, model 2A36C23, was performed at the facility of Golden State Propeller. The propeller blades, K86537YS and K86502YS, had last received maintenance from T & W Propellers about June 2002. Thereafter, the propeller had been in service for about 51 hours. During the examination, improper logbook entries were observed relating to airworthiness compliance. Also, the blades were found dimensionally improper, and corrosion was noted beneath paint in areas devoid of conversion coating. The FAA inspector reported that of the anomalies observed on the teardown, the blade chord width being under dimension was the most significant because there is no allowance for returning the blades to service with these deficiencies. The overhaul did not conform to basic practices of corrosion removal and prevention.
As a result of this investigation, the following actions transpired:
T & W Propellers Surrendered Certificate.
On February 17, 2003, the owner of T & W Propellers wrote a letter to the Riverside FSDO. The letter stated that T & W Propellers' building lease would expire the following month, and it had ceased operations on February 14. Attached to the letter were the company's original Air Agency Certificate and Repair Station Operations Specifications.
Safety Board Recommendations.
The Safety Board issued to the FAA the below-listed recommendations: (No. 1 and No. 2 were issued in April 2003, and No. 3 and No. 4 were issued in February 2004.)
1. Require the immediate inspection of all propeller parts and propeller assemblies overhauled or inspected by T & W Propellers to determine if they are airworthy. (A-03-13);
2. Require that all Hartzell Z-shank propellers be overhauled every 2,000 hours or 5 years, whichever comes first, as recommended by the manufacturer. (A-03-14);
3. Issue a regulation, similar to 14 Code of Federal Regulations 119.39, that applies to applicants for a Part 145 repair station certificate, so the FAA can prevent individuals who have been associated with a previously revoked repair station from continuing to operate through a new repair station. (A-04-01); and
4. If an air carrier, operating, or repair station certificate is surrendered prior to completion of an enforcement investigation that is based on charges that could be grounds for revocation, the FAA should nonetheless complete the investigation to the extent necessary to document all available facts relating to the fitness of the involved individuals; these facts should be made available to all FAA personnel responsible for granting a future air carrier, operating, or repair station certificate when considering the fitness of the applicant. (A-04-02).
1. On March 31, 2003, the FAA issued a Suspected Unapproved Parts Notice, No. 2003-00142. In part, the notice indicated that T & W Propellers had "failed to accomplish maintenance in accordance with the manufacturers' maintenance manuals...or FAA-approved procedures....Evidence indicated that T & W installed incorrect hardware and may have falsified work orders and other documentation associated with approving the propellers for return to service. The FAA has been unable to determine the exact time span during which the improper maintenance occurred. Therefore, all propellers that T & W maintained or approved for return to service from approximately 1997 until 2003 are suspect."
2. The FAA issued Airworthiness Directive No. 2005-18-12, with an effective date of October 14, 2005. The AD requires inspecting certain Hartzell propeller blades and other critical propeller parts for corrosion and mechanical damage that can cause failure of a propeller, which could result in loss of control of the airplane.
Following the conclusion of the investigation, the airplane wreckage was released to the owner's assigned insurance agent. No original records were retained.