This file contains the text of the General Aviation Airworthiness Alerts, AC 43-16, with graphics and illustrations removed. The advisory circular is published monthly by the FAA Flight Standards Service. Items in the publication are selected from Malfunction or Defect Reports submitted by the general aviation public. Items are selected for publication when the subject is likely to be of interest to a broad segment of the general aviation industry or when a particular safety issue is reported. Inclusion of an item in the Alerts does not imply that a hazard exits or that an analysis has been conducted on any part or product. A free subscription to the Alerts is available by contacting: Regulatory Support Division, AFS-600 ATTN: AFS-643 P.O. Box 25082 Oklahoma City OK 73125 (405) 954-6487 ALERTS SEPTEMBER/1995 INDEX AIRPLANES AERONCA BEECH BELLANCA CESSNA FOUGA LAKE PIPER STINSON HELICOPTERS AGUSTA AMERICAN EUROCOPTER BELL HUGHES/SCHWEIZER AGRICULTURAL AIRCRAFT PIPER BALLOONS AND GLIDERS THE BALLOON WORKS AMATEUR AND EXPERIMENTAL BUILT AIRCRAFT KR-2 LONG EZ ZODIAC PROPELLER AND POWERPLANT TEXTRON LYCOMING ACCESSORIES SLICK MAGNETOS AIR NOTES LINSEED OIL RESIDUE DISPOSAL AIRPLANES AERONCA Aeronca Fuel Gascolator Model 7AC 2821 Champ After an accident caused by fuel starvation, an investigation determined the glass gascolator bowl had failed. Although the glass bowl was broken, the safety wire and bail were still attached to the assembly. Champion Aircraft Corporation “Service Hint #15” recommends the glass gascolator bowl be replaced with a metal unit. Previous failures, caused by vibration and/or overtorqueing of the adjustment clamp, prompted the issue of this document. This condition may also affect the many other aircraft using a glass gascolator bowl. Part total time-4,399 hours. Aeronca Rudder Cable Damage Model 7AC 2720 Champ During an annual inspection, the left rudder control cable (P/N 1-2364) was found severely frayed. Approximately 80 percent of the cable strands were broken at the point it passed over a 1-inch diameter pulley at the rear cabin bulkhead. A 1-inch diameter pulley at a different location was found not rotating and had a flat spot worn into the cable groove. The submitter stated these defects did not exist during the previous annual inspection and suggested more frequent inspections. Part total time not reported. BEECH Beech Nose Landing Gear Collapse Model E-18S 3230 The pilot reported the landing gear failed to retract after takeoff, and the nose gear collapsed during landing. All three green “down-and-locked” indicator lights were reported to be illuminated prior to landing. An inspection revealed the bolts, used to secure the nose gear retraction nut (P/N 221-4) and push-pull tube (P/N 221- 2), had failed. During an operational test of the landing gear, the wire connected to the landing gear motor control switch on the nose gear “walking beam” was found broken. Evidently, the motor shut off at the same time the wire failed. Also, the position indicator light switches were out of rig enough to allow a “down-and-locked” indication prior to the gear locking in the “down” position. The submitter speculated the motor control switch wire failed just prior to full extension of the gear and placed a tension load on the bolts previously mentioned. It was recommended an operational test be accomplished to assure the landing gear rigging allows the gear to attain the “down-and-locked” position prior to illumination of the green indicator lights. Part total time not reported. Beech Wing Root Seal Model F33A 5350 Bonanza During a day VFR flight, a loud disconcerting drumming noise and vibration was felt and heard. The sound was similar to that produced by closing the cabin door on a dangling seatbelt or a broken ADF antenna wire. After a routine landing, it was discovered the wing root rubber seal detached from the lower side of the left wing, and had been slapping the fuselage and lower wing surface. This seal is normally attached by an adhesive and had been poorly installed after a recent aircraft paint job. The loose end of the seal was responsible for opening the “belly drain door” and bending its hinge. The submitter recommended this seal be inspected for security and condition during preflight and scheduled inspections. Part total time-1,200 hours. Time since seal installation was 30 hours. Beech Elevator Control Push-Pull Model 35-C33A Tube Bonanza 2740 During a scheduled inspection, the elevator push-pull tube was removed for inspection. A hole was found at the aft end of the tube (P/N 95-524017- 8) at the point where the tube tapers. The hole was probed and found to be caused by internal corrosion. The rod-ends were removed, and an inspection of the tube interior revealed extensive corrosion requiring replacement of the part. It is recommended all flight control push-pull tubes be given extensive scrutiny during scheduled inspections and maintenance. Part total time-3,974 hours. Beech Engine Air Filter Model F-35 7160 Bonanza After installation of a Brackett air filter, the submitter found the manifold air pressure (MAP) was 2 inches (Hg) lower at takeoff power than with the original filter installed. An investigation determined the differential pressure was opening the alternate air door. The alternate air door began to open at 21 inches MAP, and was fully open at 23 inches MAP. A new alternate air door spring was installed, and another operational test produced the same result. From reading this report, one would conclude the Brackett air filter was not allowing sufficient airflow to the engine. This problem was presented to the manufacturer who stated this was not normal. According to Brackett, “one should normally see approximately 2 inches H20 drop or 1/5 inch Hg.” This air filter system has been in use for many years, and the manufacturer is not aware of this type of previous occurrences. A review of the FAA Service Difficulty Reporting (SDR) data base revealed 53 entries associated with Brackett air filters since 1986. Only two of these reports cited symptoms described in this article. The cause of one report was attributed to excessive oil on the filter element, and the other to installing the assembly “backward.” Most of the other reports concerned water or ice saturation of the filter element during operation and deterioration of the foam filter element. The exact cause of this defect has not been determined. If additional information is obtained, it will be printed in a future edition of this publication. Part total time-0 hours. Beech Landing Gear Extension Failure Model B-60 3230 Duke During a landing approach, the landing gear would not extend normally, and a “burning” odor was detected. When the gear was extended manually, a loud “popping” sound was heard. An inspection revealed the right main gear uplock roller (P/N 6NBC914YJ or NAS 505-65) was seized, and the roller would not disengage from the uplock block. The submitter speculated this caused the gear motor to burn out and bend the retraction rod (P/N 60-810057-617). The manufacturer’s maintenance manual requires lubrication and inspection of the uplock roller assembly each 100 hours of operation. Part total time-3,354 hours. Beech Pneumatic System Plumbing Model B-90 3610 King Air The pilot reported the pneumatic pressure, and vacuum was low and declining. An investigation disclosed the pneumatic regulator was contaminated with “black dust” and larger pieces of debris. The contamination source was traced to a pneumatic supply hose (P/N 156001-10D-184) on the left engine. Approximately one-third of the internal hose lining was missing, and the remainder crumbled when the hose was even slightly bent. Although the hose had no identifying marks, the submitter believed it to be an incorrect part number for this installation. Exposure to engine-generated heat was blamed for the hose deterioration. This hose was reported to be 5.4 years old Beech Wing Flap Drive Bearing Model C-90A 2750 King Air During routine maintenance and lubrication, the wing flap drive gear (P/N 100-524074-1) bearing (P/N B36) was found with all of the “needles” missing. (Refer to the following illustration.) The bearing cage and both races were all that remained in the gear assembly. No evidence of the missing “needles” could be found in the gearbox. Evidently, the bearing had been installed with the “needles” missing. The submitter did not offer any other conclusion. Part total time-3,378 hours. Beech Aileron Structure Model C-99 5751 Airliner During a scheduled inspection, a crack was found in the right aileron skin. The crack was located on the forward side of the top aft outboard skin (P/N 99-130000-11) at the point where it attached to the aileron spar. The orientation of the 4-inch long crack is shown in the following illustration. The submitter stated a similar crack was found in the same location on another like aircraft by them. The cause of this defect was not given. Part total time-6,750 hours. Beech Air-Conditioner Bearing Model B-200 Failure Super King Air 2110 During a scheduled inspection, the air-conditioner system drive quill shaft (P/N 101-910108-1) was found sheared. Further inspection revealed the aft support bearing (P/N 206SZZC) appeared to have seized, spun in the drive pulley, and caused the drive quill to shear. The submitter stated this was their second experience with this type failure. Inadequate lubrication of the bearing was blamed for this failure. Since this is a sealed bearing, it should be changed at the first sign of abnormal operation. Part total time-389 hours. Beech Engine Controls Model 400A 7603 Beechjet The pilot reported that while taxiing, the left engine failed to respond to power lever input. The engine was shut down using the firewall shut-off valves, and the aircraft was returned to the parking ramp. An investigation revealed the ball joint swivel assembly (P/N 85043-3), located on the forward end of the engine control cable (P/N 45AS42010-13), had unthreaded from the cable. During an inspection of the right engine, the control cable was found loose on the cable shaft and could be rotated using light hand pressure. There was no damage found with either of the cable or ball joint swivel assemblies. After consulting the technical data, it was found that both engine control cable assemblies were missing a jamnut (P/N NAS509-4C) intended to lock the cable shaft to the ball swivel. (Refer to the following illustration.) The jamnut and ball swivel are part of the control cable assembly, and there is no independent listing for them in the Illustrated Parts Catalog. Since it is necessary to remove the jamnut and ball swivel to facilitate installation of the assembly, the submitter speculated the nut was omitted during the last installation. It was recommended that all operators conduct a one-time inspection of this assembly for condition, security, and proper installation. Part total time-1,645 hours. BELLANCA Bellanca Flight Control Cable Corrosion Model 7GCBC 2700 During an annual inspection, three flight control cable turnbuckle ends were found severely corroded. Two elevator cable ends and one wing flap cable end, located in the aircraft belly, were affected. The corrosion had consumed approximately one-half of the original cable end diameter. These turnbuckles had been safetied with “brass” safety wire, and the submitter speculated this along with exposure to a salt-air environment caused the corrosion. When the remaining flight control turnbuckles were inspected, all had been safetied with stainless steel safety wire, and no signs of corrosion were found. Part total time-1,408 hours. Bellanca Wing Spar Cracks Model 8GCBC 5711 Scout While installing new fabric on the left wing, several small cracks were found on the front wing spar. The cracks were located near the strut attachment point where two doublers were installed. The doublers were located on the forward and aft sides of the spar, and the cracks appeared to originate in the spar at the corner where each doubler ends. All of the cracks were approximately .75-inch long, and it was necessary to replace the wing spar. The submitter did not speculate concerning the cause of this defect. It would be wise to inspect this area for similar defects at every opportunity. Part total time-6,787 hours. CESSNA Cessna Horizontal Stabilizer Rib Model 152 Cracks Aerobat 5511 A recent report stated frequent findings of cracked and/or broken ribs on the horizontal stabilizer leading edge during scheduled inspections. The defective ribs (P/N’s 0432001-6 and 0432001-46) were primarily found on the right side of the stabilizer. The submitter speculated the cause was the elevator trim assembly (located on the right side) exerting excessive loads on the ribs. The aircraft maintained by this operator are used in a training environment, which may have been a contributing factor. Improper ground handling may also have been the cause of these defects. Part total time-7,804 hours. Cessna Alternator Failure Model 172N 2421 Skyhawk The instructor pilot reported smelling smoke and hearing a noise which appeared to originate at the alternator. A visual inspection gave no indication of trouble; however, when the drivebelt tension was checked by hand, the front half of the alternator moved away from the rear half. The case bolt and safety wire were still intact and (at first look) appeared to be alright. A further inspection disclosed the case bolts had broken at the point where they thread into the rear case half and were held in place only by the safety wire. Part total time not reported. Cessna Horizontal Stabilizer Model R182 Structure Skylane RG 5510 During a preflight inspection, a 1-inch crack was found on the left side of the horizontal stabilizer. The crack was located in a bend radius of the rear spar attachment reinforcement bracket (P/N 0732101-4) adjacent to the outboard hole. The operator stated this was the second occurrence of this defect on the same aircraft and similar cracks had been found “numerous times on other aircraft in their fleet.” The exact number was not given. The submitter stated the most likely cause of this defect was improper ground handling of the aircraft. It was recommended this area be given special attention during scheduled inspections. Part total time not reported. Cessna Alternator Intermittent Model T182RG Operation Turbo Skylane 2420 The aircraft owner complained that the alternator operated intermittently. Maintenance records indicated the alternator had recently been replaced by another maintenance facility in response to the same problem. Although all electrical system components appeared to function properly, an engine operational check disclosed the problem was still present. It was decided to change the alternator control unit (P/N C611005-0103). When the unit was removed and turned upside down, water ran out of the six pin plastic connector. After the part was thoroughly dried and reinstalled, the intermittent alternator problem did not recur. The submitter suggested sealing the connector and wires or changing the unit mounting to preclude water entrance. Part total time not reported. Cessna Aileron Failure Model 195A 5751 During an accident investigation, cracks were found in the area of the left aileron hinge attachment point to the rear wing spar. Evidence indicated these cracks had grown over time and culminated in failure of the hinge point. The pre-existing cracks appeared to be concentrated at the lower attachment bolt (P/N AN3). Also, surface and skin lap corrosion was found in this area which may have contributed to weakening of the structure. It would be wise to conduct a rigorous inspection of this area during scheduled inspections and maintenance. Part total time-3,000 hours Cessna Nose Landing Gear Down Lock Model P210N Spring Centurion 3230 During and annual inspection, the nose landing gear down lock spring (P/N 9882024-1) was found broken. The Cessna Pilot’s Association Newsletter published an article covering this subject, and Cessna has issued a replacement part which is less prone to failure. A broken down lock spring may lead to inadvertent nose landing gear retraction. All aircraft using the old-style spring should be inspected and the spring should be replaced. Part total time-1,531 hours. Cessna Exhaust System Failure Model T310Q 7810 The pilot reported that during an aftertakeoff climb, the left engine began making a “deep throaty” sound. A precautionary landing was made, and the aircraft was turned over to maintenance. An inspection revealed the exhaust riser (P/N 0850710-31) on the number two cylinder had a hole in the lower side. Prior to this flight, the aircraft had been used for flight training which included single-engine procedures. After an interview with the pilot and further examination of the failed part, it was determined “shock cooling” may have been the cause. Part total time since overhaul-855 hours. Cessna Landing Gear Failure Model 337A 3230 Skymaster The pilot reported the left main landing gear would not extend and lock in the “down” position during a landing approach. All attempts to attain the “down-and-locked” position failed, and the aircraft was damaged during the landing. An investigation revealed the two taper pins (P/N AN386-2- 14A), which are used to attach the left main gear universal joint to the actuator, had sheared. (Refer to the following illustration.) The submitter speculated one of the taper pins had a pre-existing crack which culminated in failure. The second taper pin failed due to the increased load imposed. During a preliminary visual inspection, the taper pins appeared to be intact. A physical inspection of the taper pin installation during scheduled inspections was recommended. Part total time-2,487 hours. Cessna Landing Gear Trunnion Crack Model 402C 3213 Businessliner During a preflight inspection, the pilot reported the right main landing gear strut was low. While attempting to service the strut, maintenance personnel discovered a crack approximately 4 inches long adjacent to the casting mark on the upper gear trunnion (P/N 5141103- 14). During disassembly, the strut barrel was also found cracked. A review of the maintenance records, and interviews with pilots who recently flew the aircraft, did not indicate any unusual or hard landings. The landing gear had been inspected thoroughly by maintenance personnel 4 hours prior to this occurrence. A metallurgical analysis was not accomplished; however, due to the high number of operating hours on this part, metal fatigue seems the most likely cause for this failure. Part total time-16,399 hours. Cessna Landing Light Switch Failure Model 550 3340 Citation The pilot reported the right landing light was inoperative. An investigation determined the cockpit control switch (P/N MS35058-22) did not have electrical continuity. The switch displayed evidence of heat damage on the bottom and at one terminal lug. The submitter did not offer a cause for this defect; however, it is likely the switch suffered from an internal electrical short circuit. Part total time-7,966 hours. LAKE Lake Fuel Filter Bowl Corrosion Model LA 4-200 2821 Buccaneer During an annual inspection, the fuel filter element bowl was found severely corroded when it was being cleaned. The corrosion had progressed through approximately 50 percent of the wall thickness of the metal bowl (P/N 26413). The submitter stated a considerable amount of water was present inside the bowl which was blamed for the corrosion. If allowed to continue, the bowl wall thickness could have been penetrated, causing the potential for engine failure or fire. This filter element bowl was installed in accordance with Airworthiness Directive 76-12-11, and should be cleaned and inspected at every opportunity. Part total time-884 hours. FOUGA Fouga Rudder Travel Restriction Model CM 170 2720 Magister During a scheduled inspection, the rudder travel was found to be obstructed. An investigation determined the rudder pedal assembly was hitting a recently installed “radio stack.” The cause of this defect is obvious and requires close attention, planning, and operational tests to avoid incidents of this type. Part total time not reported. PIPER Piper Fuselage Structure Model PA 18-150 5311 Super Cub During an annual inspection, a fuselage structural tube was found broken. The tube ran diagonally and was located at Fuselage Station (FS) 127.5 on the right side. It was broken at approximately the center of the tube length. The defective tube was repaired, and an inspection did not reveal any further damage. Although an obvious reason for this damage was not evident, the submitter suspected a hard landing and/or unusual flight attitudes as the cause. The aircraft was operated with floats installed. Part total time not reported Piper Flight Control Yoke Model PA 28-161 2701 Cadet During a 100-hour inspection, the flight control yoke on the pilot’s side was found to have an abnormal amount of “play” in aileron movement. The universal joint was excessively worn, and the aileron sprocket stop pin was cracked. The stop pin was almost completely broken. Although the submitter did not offer a cause for this defect, it was most likely caused by wind gusts on the control surfaces. This condition should prompt maintenance personnel to inspect the entire flight control system for related damage. Part total time-5,913 hours. Piper Pitot Mast Heater Model PA 28-181 3411 Archer II During an annual inspection, one of the two pitot mast heaters was found to be inoperative. Although the mast was warm, it would not get hot. This was a “shark fin” type pitot mast which is common to many other Piper model aircraft. Since pilots and many mechanics typically check pitot heat operation by feeling for heat, one heating element may be inoperative and go undetected. The 12-volt heating elements used in this mast are rated at 70 and 100 watts and are wired in parallel. They can be checked for operation by measuring their electrical resistance. The 70 watt heater has a resistance of 2.6 Ohms and the 100 watt heater has a resistance of 1.8 Ohms. Their combined resistance should be approximately 1.1 Ohms. Checking the system by this method may prevent some burned fingers. With only one pitot heating element functional, operation of the aircraft in icing conditions may lead to loss of the pitot static system. Part total time-1,114 hours. Piper Nose Landing Gear Drag Brace Model PA 28RT-201T 3220 Turbo Arrow IV The pilot reported that during cruise flight, a loud “bang” was heard, and the red landing gear warning light illuminated. The landing gear was extended normally, and a safe landing was made. An inspection revealed the nose landing gear upper drag brace (P/N 76426-03) was broken just forward of the hydraulic actuator attachment point. (Refer to the following illustration.) Piper has issued Service Bulletin (SB) 724A, which addresses this subject, and offers an improved part (P/N 76426-803) designed to prevent this type failure. Part total time-3,413 hours. Piper Alternator Fan Model PA 31-350 2421 Chieftain During a scheduled inspection, the alternator faceplate displayed signs of rubbing on the drivebelt. It was suspected this was caused by a cracked fan assembly (P/N 90-2241). When the alternator was removed for further investigation, a crack was found at the drive key hole and ran in a spiral direction around approximately one-half of the fan. The crack then went straight to a fan blade cutout. A second crack had started to form a “Y” shape which was also oriented toward another blade cutout. Failure of the fan assembly was imminent. The cause of this defect was not given. Part total time not reported. Piper Cabin Combustion Heater Model PA 31-350 2140 Chieftain While troubleshooting an overtemperature problem with the cabin combustion heater (Janitrol), the combustion air safety switch (P/N B42036) was found stuck in the “closed” position. The combustion air blower system had air leakage and did not supply sufficient airflow to support proper combustion. The safety switch did not open to shut the heater down, and it ran until the overtemperature switch deactivated the system. A malfunction of this type heater can be deadly and deserves close attention during inspections and maintenance. Part total time not reported. Piper Engine Fire Model PA 32RT-300T 8120 Turbo Lance II Information for the following article was taken from an FAA aircraft incident report submitted by Mr. Greg Minarik of the Fresno, California Flight Standards District Office. While conducting a parachute jump flight, the pilot noticed an acrid odor in the cockpit during the aftertakeoff climb. The odor was compared to what might be generated by burning rubber or fiberglass. After a short time, the engine began to miss, and the engine operating sounds became “deep and throaty.” The cockpit temperature began to increase rapidly, and flames were visible over the cowling, filling the cockpit with smoke. The four skydivers evacuated the aircraft at an altitude of 900 feet AGL, and the pilot made a 180 degree turn to the departure airport. While on short final approach, the landing gear failed to extend normally, and there was insufficient time for emergency extension. The aircraft was landed on a grass surface. There were no personal injuries, and the aircraft damage was classified as minor. An investigation revealed the turbocharger exhaust coupling (P/N 556-108) and turbocharger tailpipe (P/N 98705-2) failed, allowing hot exhaust gases to fill the engine compartment causing the fire. Airworthiness Directive (AD) 80-20-05 requires a one-time inspection of these parts. The submitter recommended these parts be inspected at frequent intervals and that the manufacturer’s service manual (SM) be adhered to when accomplishing inspections. The SM requires an inspection of the turbocharger tailpipe coupling clamp at 50-hour intervals, and it would be advisable to inspect the entire assembly at the same time. Part total time-1,850 hours Piper Engine Failure Model PA 34-200T 2840 Seneca III The pilot reported the left engine quit in the same manner as if the mixture control had been pulled. A safe single- engine landing was made. An investigation disclosed the copper fuel line running from the fuel flow/pressure indicator to the fuel flow divider had broken just behind the “B” nut at the flow divider end. This caused a loss of pressure to the fuel injector nozzles. The line had been properly supported and clamped; however, vibration appeared to be the cause of failure. The submitter suggested using a line constructed from a more substantial material than copper for this installation. Of course approved data would be required to make such a change. Part total time not reported. Piper Engine Exhaust Pipe/Heat Muff Model PA 46-350P 7800 Malibu Mirage During a scheduled inspection, the right tailpipe/heat muff assembly was found cracked around the circumference at a weld. (Refer to the following illustration.) Also, the heat muff had worn through the flange and was no longer sealing against the tailpipe. The submitter speculated the cause of this defect was a design problem with the tailpipe support. The support is attached to the heat muff which, along with extreme heat differentials, seems to stress the heat muff weld. This condition allows exhaust fumes to enter the cabin creating a very hazardous situation. Part total time not reported. Piper Engine Mount Corrosion Model PA 60-601P 5312 Aerostar During unscheduled maintenance, the right engine mount frame tubing was found severely corroded. Several areas of corrosion were found, all of which were covered by a protective heat shields. (Refer to the following illustration.) The stainless steel heat shields were lined with a fibrous material and were installed in 1981 as part of Supplemental Type Certificate (STC) SE978NW. The submitter stated the fibrous material held moisture in contact with the steel tubing causing the corrosion. The severity of corrosion, in this case, substantially compromised the structural integrity of the engine mount system, and jeopardized safe operation of the aircraft. It is recommended a one-time inspection of the affected area be accomplished by all operators to ascertain the condition of the engine mount tubing. Part total time not reported. STINSON Stinson Rudder Spar Structural Cracks Model 108-1 5541 Voyager During an annual inspection, the rudder spar was found cracked. There were two cracks, one on each side of the spar channel radii, approximately 1 inch long. The cracks originated at the lower end of the spar and traveled upward. This area is adjacent to the tailwheel yoke attachment point, and it was believed vibration from landings was the main cause of this defect. There have been several other reports of similar defects on Stinsons as well as other tailwheel equipped aircraft. The causes appear to be high-speed taxi on rough surfaces, landings on rough surfaces, and improper landing techniques. These conditions should be avoided; however, if any of these conditions are experienced, an inspection of the tailwheel and adjacent structure should be accomplished. Part total time not reported. HELICOPTERS AGUSTA Agusta Main Rotor Servo Model A109A 6730 Mark II While performing routine maintenance and using a hydraulic mule, a stream of Mil-L-5606 hydraulic fluid was discovered leaking from the right hand aft servo (P/N 109-0110-42-5). Further investigation revealed the leak was coming from the aft weep hole located at the split line of the servo. Technical Bulletin (TB) 109-72 deals with similar leaks at the upper body of the servo actuator. The submitter stated that this problem, although not addressed in TB 109-72, can result in a total loss of fluid in the number 2 hydraulic system reservoir. Part total time since overhaul-1,254 hours. AMERICAN EUROCOPTER American Eurocopter Cockpit Sliding Vent Window Model BK117-2 5210 Space Ship The pilot reported the right cockpit sliding vent window (P/N 117-24163-86) separated from the aircraft during flight. It was speculated air turbulence, vibration, and cracks adjacent to the handle assembly caused the window to be lost. The submitter stated cracks typically develop near the handle assembly due to the handle hitting the solid window during operation. There was no damage to the airframe or rotor blades attributed to this incident. This window and the latching mechanism should be inspected for defects at every opportunity. Part total time-32 hours. Ameican Eurocopter Right Hand Sliding Model BK117-2 Vent Window Space Ship 5210 The pilot reported the right sliding cockpit window (P/N 117-24163-86) separated from the aircraft during flight. It was speculated air turbulence, vibration, and cracks adjacent to the handle assembly caused the window to separate. The submitter stated cracks typically develop near the handle assembly due to the handle hitting the solid window during operation. Neither the airframe nor the rotor blades sustained damage resulting from this incident. This window and the latching mechanism should be inspected for defects at every opportunity. Part total time-32 hours. Bell Starter Generator Model 206L-3 2435 Long Ranger III While performing a power recovery following an autorotation, the engine would not return to 100 percent N2 (power turbine RPM) when the throttle was “rolled on.” The RPM only returned to 97 percent N2. All the engine controls were replaced; however, the problem remained. A Bell Helicopter Technical Representative recommended replacing the starter generator. It was explained that starter generator vibrations have, in a few instances, interfered with the operation of the governor. The starter generator was changed, and the problem was resolved. Part time since overhaul-841 hours. Bell Tail Boom Assembly Model 206L-3 5302 Long Ranger III While performing a routine inspection, a crack was discovered on the aft portion of the tail boom assembly. The crack was “L-shaped” and approximately 10 inches long. The crack appeared to have started at one of the rivets used to mount the tail rotor gearbox mount casting to the tail boom skin, and it ended on the right side of the tail boom at the skin splice. The pilot reported no unusual vibrations in the airframe or rudder pedals on the previous flight. The submitter suspected the cause of this defect was an out-of- balance tail rotor. The submitter suggested that Bell Helicopter Textron amend their 100-hour inspection form to include checking the tail rotor dynamic balance. Part total time not reported. Hughes/Schweizer Strut Assembly Model 269B 3270 An accident investigation was conducted after the helicopter “self-destructed” when a ground resonance condition was encountered. During the inspection, it was noted that both the left hand shock strut and skid attachment lugs were severely corroded (exfoliation) and separated. The submitter suggested removal of all shock struts during annual/100-hour inspections to ensure no corrosion exists in these areas. Part total time not reported. AGRICULTURAL AIRCRAFT PIPER Piper Structural Tubing Cracks Model PA 36 5311 Pawnee Brave When the hopper was removed for repair, an inspection revealed cracks in the engine mount tubing clusters. The tubing was cracked aft of the firewall, adjacent to the top engine mount attachment points. Airworthiness Directive (AD) 79-12-09, which requires installation of gussets in this area, had been accomplished, and it appeared these cracks developed after that installation. One of the cracks was approximately 2 inches long. The submitter did not offer a conclusion concerning the cause of this defect. Part total time-4,550 hours. AMATEUR AND EXPERIMENTAL AIRCRAFT KR-2 Propeller Hub 6114 The first flight of this amateur built aircraft ended with an accident when the propeller separated from the converted Volkswagen engine. The cotter pins, through the prop hub attachment bolts, had sheared and the bolts backed out of the bolt holes. The owner/builder stated he had not checked the bolts for proper torque. Part total time - 60 hours. Long Ez Oil Cooler 7921 While in cruise flight, the oil cooler ruptured at the output end of the oil cooler. This caused a rapid loss of oil and ensuing engine failure. An on-airport landing was performed without further incident. The submitter suspected the solder flux was not thoroughly cleaned from the tank (an improved method of cleaning these tanks has since been implemented), and caused a thinning of the material at the output end of the oil cooler during manufacture. The above mentioned oil cooler is part of a certified engine that is installed on the Cessna CE-172M. Part total time-2,200 hours. Zodiac Propeller Bolts 6110 During a power change while flying in the airport traffic pattern, the propeller departed the aircraft. Examination of the six .25-inch attachment bolts indicated they had failed at a point flush with the crank shaft flange. All these bolts appeared to have been overtorqued at installation only 11 hours prior to the accident. The submitter suggested that all operators of Rotax engines using .25-inch propeller bolts, check for condition and proper torque of these bolts. Part total time-11 hours. HOT AIR BALLOONS AND GLIDERS THE BALLOON WORKS The Balloon Works Deflation Line Pulley Failure Model Firefly 11 5102 While attempting to deflate the balloon, the eyebolt used to retain one of the two deflation line pulleys broke. The pilot stated it took three people and extraordinary effort, strength, and time to deflate the balloon. Fortunately, the winds were light during this event. A high- wind landing could have been dangerous without the mechanical advantage of the pulley system. In addition to anchoring the deflation line pulley, the eyebolt is also used to fasten the heater superstructure to the basket. Therefore, with the eyebolt broken the heater support system is also compromised. Inspection of the eyebolts for cracking, bending of the shank, and visible damage at every opportunity is recommended. This is especially important on high-time balloons. Part total time-80 hours PROPELLERS AND POWERPLANTS TEXTRON LYCOMING Textron Lycoming Cylinder Damage Model O-235-L2C 8530 This engine was installed in a Piper Model PA 38-112 aircraft. While the cylinders were removed for accomplishment of Supplemental Type Certificate (STC) SE792NW, all four displayed evidence of pitting on the cylinder walls. The camshaft lobes and lifter lands had flat spots, pitting, and excessive wear. The submitter speculated this damage was caused by corrosion which occurred during a long period of inactivity. The maintenance records and recording tachometer indicated only 3.2 hours of operation between March 1991 and August 1993. The maintenance records did not indicate any preservation procedures had been accomplished as recommended by Textron Lycoming Service Letter L4180A. It seems neglect resulted in some very costly repairs in this case. Part total time since overhaul-1,546 hours. Textron Lycoming Push Rod Failure Model O-235-L2C 8530 This engine was installed in a Beech Model 77 aircraft. While investigating the cause of excessive valve clearance, all of the push rods were found to have the wrong part number. Airworthiness Directive (AD) 80-25-02, which references Service Bulletin (SB) 453, requires installation of an improved push rod. (Refer to the following illustration for push rod part numbers and markings.) The push rods found, in this case, were not in compliance with the AD, and displayed signs of damage described in the previously referenced documents. This operator contacted the manufacturer who stated the records indicate the engine was shipped from their facility to Beech with push rods that were in compliance with the AD. The aircraft records did not indicate the push rods had been changed since delivery of the aircraft. The origin of the improper push rods remains a mystery. It would be wise to check compliance with the AD at every opportunity and make appropriate maintenance record entries. Part total time-1,491 hours ACCESSORIES SLICK Slick Improper Magneto Points Model 4250R 7414 This magneto was installed on a Textron Lycoming O-360 engine in a Cessna 172N aircraft. After a complaint of an engine “miss” on one magneto, it was removed and examined. It was found the point gap had “closed down,” and the points were an improper type for this magneto. Since these points had been recently installed, the installing facility was called. According to their 1993 edition of the manufacturer’s manual, the points (P/N M3637) were correct. According to the 1994 edition of the manufacturer’s manual (and 1989), the correct part number is M3081. Another call to the manufacturer verified the mistake was in the 1993 manual. If there is any doubt about the correct use of a part, it should be verified before installation. Part total time-68 hours. AIR NOTES LINSEED OIL RESIDUE DISPOSAL After using linseed oil as a corrosion inhibitor in a pair of aircraft wing lift struts, the soaked paper towels used to remove the residue were deposited in a trash barrel. Approximately 1 hour later, the odor of overheated material was noticed. While investigating the source of this odor, the linseed oil-soaked paper towels in the trash barrel were found to be near the point of spontaneous combustion. The entire barrel was warm to the touch and the compacted paper towels were charred in the center. Left unattended, the resulting fire may have destroyed the hangar and its precious contents. There are several precautions which should be observed when disposing of excess materials, and the best source of information on this subject is your local fire department. Their advice should be sought and adhered to strictly. Many of the materials we use every day have the potential for disaster, either alone or in combination with other materials, when not properly handled, disposed of, and/or stored. Our thanks to the submitter from Florida for the information contained in this article.