Service Difficulty Reports about rotorcraft that either show a trend or should be known by the airworthiness community.
On this page
- Aerospatiale HC
- Airbus Helicopters
- Bell Textron - Canada
- Bell Textron - USA
- Dart Aerospace, Equipment
- Eurocopter France
- Helicopter Technology Company, Equipment
- Robinson
Aerospatiale HC
AS 350B2 Damaged Tail Rotor Control Rod Assembly
SDR #: 20211217008
Subject:
On a scheduled inspection, it was found that the protective sheathing was damaged and worn away to the point where the tail rotor control rod was damaged. The control rod guide had pressure on it as did some of the forward guides. It was found that the control rod was likely bent during a previous removal and installation. The maintenance manual describes the removal and installation, and if that process is followed, there is a risk of bending the control rod. To reduce this risk, the fin can be easily removed.
Transport Canada Comments:
The submitter of this Service Difficult Report has provided an excellent example of maintainers needing to remain vigilant during the performance of scheduled or unscheduled maintenance. As described by this submitter, the tail rotor control rod was only damaged because of the control rod being bent due to suspected improper maintenance during a previous installation or removal. Maintainers are reminded to always exercise good technical judgement and practices when performing any maintenance task to avoid inducing damage as described in this example.
Damage found on the tail rotor control rod assembly after the rod was found bent during an inspection
AS 350B2 - Main Gearbox Oil Filter Gasket
SDR #: 20201127013
Subject:
During the final two minutes into approach for landing after a maintenance test flight, the main gearbox (MGB) low pressure light came on. The pilot returned immediately to the landing pad at the hangar and advised that the aircraft landed without the MGB oil temperature light coming on. The MGB ran 1 minute 30 seconds in flight with the low pressure light, and 30 seconds on the ground for cool down. During the investigation, maintenance discovered that the gasket from the previous spin on filter had stuck to the housing on the MGB, and the new filter was spun on with it still in place not allowing the new filter to seal properly, and therefore allowing the oil loss. Maintenance installed a new filter, cleaned the aircraft and added the correct amount of synthetic oil. Maintenance did a 30 minute ground run, loading the MGB to the point just before hovering. There were no chip lights and after shutdown, there were no chips on any magnetic plugs. The aircraft maintenance manual (AMM) 05-50-00, 6-1 indicates the replacement of the MGB, mast bearings and possibly the main rotor shaft, and roughly 500ml of Mobil-jet 254 synthetic fluid was still in the transmission when drained. The gasket on the filter is of a thick black rubber and loose removal type can potentially be left in situ on the filter housing. Other spin-on filters, which have the gasket swaged onto the top of the filter housing, are not easily removed and come off, and are part of the filter cartridge.
Transport Canada Comments:
The submitter of this service difficulty report (SDR) has identified a physical difference in the gasket seating area of the oil filter even for the same part number (P/N) 7050A3632296 (alternate P/N FA01315A). Specifically, the oil filter gasket seating area could either allow the gasket to be removed freely, or be partially retained by an intentional swage in the filter housing completed during manufacture. Airbus Helicopters published Information Notice 3631-I-63 to clarify the maintenance of pre and post MOD 077162 MGB oil filters by helicopter configuration. The P/N 7050A3632296 (alternate P/N FA01315A) oil filters are post MOD 077162 and considered to be non-cleanable type filters. They are replaced in accordance with the maintenance instructions published in the master servicing manual. Transport Canada Civil Aviation (TCCA) wishes to make maintainers aware that the gasket that belongs with a removed MGB oil filter, has the potential to remain in place on the MGB filter support during maintenance and should be removed prior to the new filter installation.
AS 350B2 - Starter Generator Updated Overhaul and Time Between Overhaul Schedule
SDR #: 20210215012
Subject:
Starter generator driveshaft sheared during start attempt.
Transport Canada Comments:
Airbus Helicopters published service bulletin (SB) No. AS350-80.00.12 providing a modified schedule for the next overhaul of installed and non-installed starter generators. The SB also introduces a calendar limit to the time between overhaul (TBO). A review of the SB is required to determine the overhaul compliance limit established by the starter generator part number and the production or latest overhaul date. Transport Canada Civil Aviation (TCCA) recommends that operators review the SB for potential updates to their scheduled starter generator overhaul and TBO limits.
AS 350B3 - Unserviceable Post-modification 079568 Hydraulic Pump Bearing
SDR #: 20151217011
Subject:
At 10 363.6 airframe hours, the affected pump support assembly was installed to upgrade the aircraft to post-modification 079568 status. Prior to installation, the bearing was inspected and greased to ensure it was fit for service. At 10 877.0 airframe hours, the bearing was inspected as per the Aircraft Maintenance Manual. It was noted that during the tactile check, the bearing felt rough. The bearing has subsequently been sent to Airbus for evaluation. We are awaiting the final analysis from Airbus France on the bearing. Note: the bearing had not been greased during the 513.4 hours in accordance with the Maintenance Service Manual. A small amount of grease was noted on the deck during the first 20 hours of service which would be considered normal.
Transport Canada Comments:
Airbus Helicopters published Alert Service Bulletin (ASB) No. AS350-63.00.24 following reports of the pre-modification 079568 hydraulic pump bearing being seized. The European Aviation Safety Agency (EASA) subsequently mandated the ASB with Airworthiness Directive 2014-0233. Transport Canada has recently received reports of post-modification 079568 hydraulic pump bearing part number 704A33651269 being removed from service. At the time of writing, none of the reports have indicated that the bearing was found seized. If a post-modification 079568 hydraulic pump bearing is removed from service, please evaluate the part and submit a Service Difficulty Report (SDR) if it is determined as reportable.
AS 355NP - Cracked Tail Rotor Drive Shaft Support Bracket
SDR #: 20150330010
Subject:
Minor edits have been made to the text below taken from the Service Difficulty Report’s Problem Description. Transport Canada Civil Aviation reserves the right to edit for spelling, grammar and punctuation to increase comprehension.
Following an inspection of our AS 355NP, two cracks on the forward tail rotor drive shaft bracket were found between the short and long shaft. The flange had play because of the nut being loose and was likely the cause of the cracks due to the excessive vibration. The bearing appeared to be running dry. The flange assembly was sent for repair and the worn and damaged parts were replaced.
Transport Canada Comments:
This Service Difficulty Report serves as a reminder to inspect all areas of the aircraft including the items in the post-flight inspection. The cracks may have been caused by the lack of grease in the bearing but detection prior to failure was definitely a break in the chain of events. Routine servicing can play a vital role in safety and serviceability of your aircraft.
Example of the crack found in the flange.
Airbus Helicopters
AS 350B2 - Tail Rotor Gearbox Chip Light
SDR #20200326017
Subject:
During ground runs, after a scheduled 600 hour airframe inspection of an Airbus AS350 B2, a tail rotor gearbox chip light indicated on the warning panel. The procedures in the Aircraft Maintenance Manual (AMM) were followed, and the chip plug and the oil were inspected for chips and particles. The recovered particles and chips were classified, and four were found to be over the 2mm length limit as described in the AMM. As prescribed in the AMM, the particles have been sent to a lab for metallurgical analysis. Depending on the results, the gearbox may either be operated "monitored in service" or the gearbox must be sent for overhaul.
Transport Canada Comments:
As a reminder of the importance of collecting, characterizing and following up on particles in dynamic component lubricating systems, Airbus Helicopters recently published Safety Information Notice (SIN) No. 3638-S-63. The purpose of this SIN is to raise awareness of implementing strict monitoring of the dynamic assemblies to detect emerging degradation and therefore preventing the extension of its damages. The SIN provides instructions and references to the latest updates included in the AMM specific to each type of helicopter. Airbus Helicopters has also published Information Notice (IN) No. 3586-I-00 to provide notes about oil analysis and the laboratories capable of performing the analysis. Use of the instructions provided in the IN and SIN has a potential to reduce the degradation in the safety margins of the dynamic assembly over time, as well as ease repair costs by limiting the damages to surrounding parts.
Bell Textron - Canada
CAN, 407 - Smoke in the Cockpit due to Air Conditioner System Fouling
SDR #: 20210512006
Subject:
Smoke in the cockpit with ground power on was reported to Bell. A clamp was found contacting transistor.
Transport Canada Comments:
The cause of this service difficulty was determined to be a clamp from the Air Comm Corporation air conditioner system fouling with the Bell Automatic Flight Control System (AFCS). The smoke was generated when the hardware that was used to secure the clamp contacted an electrical component of the AFCS. As a result of the Air Comm Corporation investigation, Service Bulletin (SB) 407-221012 was published. The SB provides instructions to resolve the potential fouling condition between the air conditioner system and the AFCS. Transport Canada Civil Aviation would like to raise awareness of this SB to the owners, operators and maintainers of Bell 407 helicopters with an Air Comm Corporation air conditioner system installed along with the AFCS or the provisions for the AFCS.
Picture 1 - Hardware from the air conditioning system clamp contacting the electrical component of the AFCS.
CAN, 505 - Fuel Drain Tube Chafing
SDR #: 20220706006
Subject:
It was reported to Bell that a fuel drain tube was chafing against a compressor wash line tube.
Transport Canada Comments:
Bell has investigated reports of chafing between a fuel drain tube and the engine compressor wash tube, and consequently, issued Alert Service Bulletin (ASB) 505-22-29. The ASB provides instructions to accomplish a one-time inspection of the affected tubes for chafing. In addition to the inspection, the ASB also introduces clamping to ensure proper clearance between the tubes is maintained. Transport Canada Civil Aviation (TCCA) encourages the owners, operators, and maintainers of Bell model 505 helicopters to review and accomplish Bell ASB 505-22-29.
CAN, 505 - Bell 505 Fractured Main Rotor Hub Bearing Roller
SDR #: 20220216008
Subject:
Feathering bearing, part number (P/N) 206-011-118-001, was removed from a main rotor hub of a Bell model 505 helicopter. The main rotor hub has not been disassembled since new. Total time is 197.2 hours since new. The feathering bearing was found damaged upon removal. Bell Helicopter has been notified.
Transport Canada Comments:
Bell investigated this service difficulty and indicated that it may have been possible for the bearing to have been inadvertently damaged during the assembly of the main rotor hub. Although the roller was found fractured, an inspection of the rollers mating surface on the main rotor yoke showed no damage. Transport Canada Civil Aviation encourages owners, operators, and maintainers to submit a Service Difficulty Report if a fractured bearing roller is discovered during inspection of any helicopter model with a similar designed main rotor hub.
Fractured roller in bearing P/N 206-011-118-001
CAN, 407 - Parts Manufacturing Approval (PMA) Tail Rotor Pitch Link for Bell 407
SDR #: 20220328031
Subject:
During the preflight walk-around, the pilot noticed that the tail rotor pitch link at the pitch horn did not look correct. Upon further investigation, it was found that the inner bearing had been separated from the housing. The bearing did not show excessive signs of wear at the last progressive inspection event #1, which was completed 150 hours prior to the incident. It is noted that the effected part is not an original equipment manufacturer (OEM) part however, it is a PMA part.
Transport Canada Comments:
Transport Canada Civil Aviation (TCCA) has received service difficulty reports (SDRs) of excessively worn bearings on PMA part number (P/N) 4AA-312-103-101 tail rotor pitch link assembly. The SDRs are limited to the Bell model 407 helicopter, however, this PMA tail rotor pitch link assembly is also eligible for installation on model 206L4 and 427 helicopters. Supplemental instructions for continued airworthiness (ICA) are not published for these PMA tail rotor pitch links, the current ICA from Bell helicopter are applicable for each model. The PMA holder, Able Aerospace Services, has been made aware of the recent SDRs. To raise awareness, TCCA reminds operators and maintainers of the PMA P/N 4AA-312-103-101 tail rotor pitch links to remain vigilant when inspecting, and to report any service difficulties for this product.
Tail rotor pitch link housing found dislodged from the bearing during preflight inspection.
CAN, 429 - Worn Directional Control Idler Bearing
SDR #: 20210211015
Subject:
The following was reported to Bell upon the 800-hour inspection. Excessive wear was found on the bearing of the directional control idler.
Transport Canada Comments:
The worn bearing, part number (P/N) MS14101-5A, is a component of the tail rotor directional control idler assembly, P/N 429-001-721-105. Several Service Difficulty Reports (SDRs) were received describing a worn bearing, P/N MS14101-5A, in the idler assembly. Bell investigated these reports and published Operation Safety Notice (OSN) 429-19-04 to highlight the importance of completing the scheduled detailed inspection of the bearing. In addition to publishing the OSN, Bell has indicated the possibility of a future design change to replace the existing bearing. Transport Canada Civil Aviation (TCCA) will monitor this service difficulty and reminds operators and maintainers to continue submitting a report for each reportable service difficulty.
Bearing, MS14101-5A, installed in the tail rotor directional control idler assembly, P/N 429-001-721-105
CAN, 429 - Bell 429 Non-Conforming Main Rotor Pitch Change Link Upper Retaining Bolt
SDR #: 20210825042
Subject:
When trying to install an alternate bolt part number (P/N) 20-114C5P47AD for the upper main rotor pitch change link rod end, it was found with an existing hardware stack up. The nut bottoms out on the shank prior to reaching the torque specification. A bolt, according to specification, should be 2.938 inches but was measured at 2.995 inches. After an investigation, it was found that the length discrepancy is the result of a manufacturing error.
Transport Canada Comments:
Bell has investigated and found some of the P/N 20-114C5P47AD bolts to be non-conforming to the design due to a grip length that is greater than the specification. A bolt with a grip length that is greater than specification presents the potential risk of an improper clamp-up to the assembly. When the nut is installed and torqued to the specified value, it could bottom out on the grip portion of the bolt before the correct clamp-up is achieved. Bell has published Alert Service Bulletin (ASB) 429-21-55 to provide instructions for the one-time inspection and removal of non-conforming bolts. If not already completed, Transport Canada Civil Aviation (TCCA) encourages owners, operators, and maintainers of the affected helicopters to review and carry out the accomplishment instructions of ASB 429-21-55.
CAN, 429 Bell 429 Battery Venting
SDR #: 20200311006
Subject:
During an inspection, battery acid was found leaking from the battery case lid. The acid had been spilled throughout the battery compartment and damaged the battery hold-down hardware. This is the third case of battery failure causing acid spillage on this airframe in three years.
Transport Canada Comments:
Bell has published Technical Bulletin (TB) 429-17-53 after receiving reports of moisture in the nose compartment through the battery door and vent system. Accumulated moisture in the vent system has a potential to prevent normal battery venting. Some model 429 helicopter operators have experienced and reported a service difficulty where the battery vented directly from under the lid instead of through the airframe venting provisions. The Accomplishment Instructions of TB 429-17-53 incorporate a modification to install a new gutter along with vent and drain improvements. Transport Canada Civil Aviation (TCCA) will continue to monitor for additional related Service Difficulty Reports.
CAN, 505 Air Conditioner Tube Fouling with Electrical Harness and Cargo Hook Release Cable
SDR #: 20210506023
Subject:
A potential fouling condition of an electrical harness was found at four locations between the air conditioner kit (505AC-101) and the cargo hook kit when installed. The aircraft was inspected but no visible chafing damages were present.
Transport Canada Comments:
Bell investigated the possibility of some air conditioner system tubes chafing various locations of wire harnesses and cargo hook release cables on the model 505 helicopter. The investigation revealed that chafing could exist and if not corrected, could lead to damage of the wire harnesses and cargo hook release cables protective shielding. Following their investigation, Bell published alert service bulletin (ASB) 505-21-24 to provide instructions to inspect for damage due to chafing, and the installation of additional clamps when the air conditioning system kit is installed. Transport Canada Civil Aviation recommends that owners and operators review ASB 505-21-24 and complete the Accomplishment Instructions of this ASB for the affected helicopters.
View of air conditioner tube and wire harnesses without the additional clamps
CAN, 505 Bell 505 Airframe Furnished Engine Oil Tank Cracked Mounting Tabs
SDR #: 20200617008
Subject:
Bell reports that during assembly it was noticed that there were cracks in the mounting tabs of the engine oil tank.
Transport Canada Comments:
Bell investigated and found that on some model 505 helicopters a condition exists where cracks in the engine oil tank mounting attachment flanges may have developed during the manufacturing process. Alert Service Bulletin (ASB) 505-20-15 was published to provide instructions to detect damage (cracks) and where possible, repair the mounting attachment flange. Following the release of ASB 505-20-15, Bell published Technical Bulletin (TB) 505-21-28 to introduce a new engine oil tank design with a manufacturing process that eliminated the stresses that created this condition. Installation of the new engine oil tank meets the terminating action requirements for the repetitive inspection of ASB 505-20-15 and incorporates a new maximum level line to clarify sight glass markings. Transport Canada Civil Aviation (TCCA) encourages owners, operators, and maintainers of Bell model 505 helicopters to review ASB 505-20-15 and TB 505-21-28 to detect this condition and rectify as needed.
CAN, 429 - Bell 429 Main Rotor Transmission Debris Pan Inspection
SDR #: 20210219018
Subject:
An operator found one debris pan incorrectly installed, which could prevent the mast chip detector from detecting metal contamination from the mast bearing. After Bell investigated, it was found that the maintenance procedure was clear and accurate, however the figure in support of the procedure could be misleading. Consequently, the maintenance manual figure will be updated to avoid repeating such an issue.
Transport Canada Comments:
The debris pan has a tab and a cutout, an incorrect installation of the debris pan is when the tab of the pan is not properly aligned with the slot in the main rotor transmission. Following their investigation, Bell published Alert Service Bulletin (ASB) 429-21-54 to provide instructions for completing a one-time inspection, and a figure showing the correct installation of the oil debris pan. The ASB states that incorrect installation could result in the lubricating oil not being supplied to the mast chip detector and to the mast spline from the #13 oil jet. In addition to the ASB, Bell will be revising the potentially misleading figure currently published in the model 429 maintenance manual. Transport Canada, Civil Aviation (TCCA) encourages owners, operators and maintainers to review and accomplish ASB 429-21-54 to verify the correct installation of the debris pan.
An example of the current potentially misleading figure in the maintenance manual and the debris pan.
206L 3 - Throttle Cable Assembly Failures and New Part Number Introduction
SDR #: 20180323008
Subject:
During an initial inspection of the throttle cable, it was felt to have considerable friction, crepitus and stiffness. While performing rigging and troubleshooting, the cable broke. Upon removal, the throttle cable was found to have wear inside the housing and on the cable, and both areas had rust and corrosion. This area of rust, corrosion and wear was located at the bottom of the tunnel elbow approximately 1.2 meters down from the attachment point on the collective throttle. This could have eventually failed in flight if not discovered, investigated and replaced at inspection. A new throttle cable part number 1608750-0041 was installed and re-rigged serviceable. No further issues have resulted.
Transport Canada Comments:
Bell has received several reports of throttle cable assemblies failing on the model 206L and 407 helicopters. Following their investigation, the majority of the failures were found to have occurred at the first bend under the pilot seat. It was noted that certain areas of the throttle cable could have high stress loads applied, or be kinked during installation. Subsequent to the investigation, Bell has published information letters (IL) 206L-21-103 and 407-21-124 to identify the root causes, introduce a new part number throttle cable assembly and provide improved installation procedures.
CAN, 206B - Main Rotor Blade Trim Tab Adhesive Cracking and Debond
SDR #: 20180604020
Subject:
During the 100 hour inspection of the main rotor blade a fine crack was found in the “paint” on the lower surface of the trim tab of the main rotor blade. Further inspection of the area revealed that the trim tab had become debonded from the main rotor blade lower surface. A feeler gauge could be inserted between the blade and the tab for approximately 25% of the tab area. A tap test of the complete tab failed to indicate the debond, it was only the fact that the debond migrated to the edge of the tab and cracked the “squish out” of the bonding agent that allowed us to find the defect. The main rotor blade is a carbon fiber component that has a different “ring tone” than we are used to with traditional metal blades. The pilot had noted that the aircraft seemed rougher than it should have been during certain flight regimes. Repeat visual inspections had failed to show the defect. The affected blade and the matching blade have been removed and returned to the manufacturer Van Horn Aviation.
Transport Canada Comments:
Multiple Service Difficulty Reports (SDRs) have been received by Transport Canada Civil Aviation (TCCA) related to cracks and debonding found in the adhesive securing the trim tab to the main rotor blade. The main rotor blades are supplemental type certified, the affected part number (P/N) is 20631000-101 for Supplemental Type Certificate (STC) SH16-46 and P/N 20633000-101 for STC SH18-69. TCCA has notified STC holder Van Horn Aviation of the SDR events. As a result of their investigation, Van Horn Aviation has published Service Bulletin (SB) 33000-3R2 to provide instructions for replacing the trim tab on main rotor blades with P/N 20633000-101. Van Horn Aviation has an additional pending SB to address the trim tab replacement for main rotor blade P/N 20631000-101.
CAN, 429 - Loose Horizontal Stabilizer Spar Clamp
SDR #: 20200706010
Subject:
An aircraft customer reported a loose horizontal stabilizer spar clamp due to a broken screw head on the left and right hand side stabilizer. Subsequent wear was noted on the clamp, fitting and spar tube.
Transport Canada Comments:
Bell Helicopter has investigated multiple reports where excessive looseness was found in the left and right horizontal stabilizers. The cause of the looseness was determined to be a fracture of the rib clamp screw that secures the horizontal stabilizer to the spar tube. Subsequent to the investigation, Bell has published alert service bulletin (ASB) 429-19-44 to provide instructions for replacing all of the rib clamp screws with a new part number screw. Transport Canada Civil Aviation (TCCA) encourages owners and operators to review the affected helicopters’ section of ASB 429-19-44, and, if found applicable comply with the Accomplishment Instructions.
407 - Erratic Measured Gas Temperature Indications
SDR #: 2016010902462
Subject:
After takeoff from a scene flight with a patient onboard, the pilot reported that the measured gas temperature (MGT) readings became erratic displaying intermittent values from 150 degrees Celsius to normal operation temperature. The pilot said that the fluctuations would last for five (5) to 10 seconds or more then stabilize at normal temperatures for 30 seconds to one (1) minute then fluctuate again. The pilot returned to base after noticing his MGT was fluctuating from 150 to 650 degrees Celsius.
Transport Canada Comments:
There are many electrical connections on the Bell 407 helicopter, and some of these connections are exposed to environmental conditions. Moisture contamination of the electrical connectors is a cause of electrical discrepancies especially for aircraft that operate in high relative humidity environments. In the past, Bell Helicopter Textron Canada Inc. (Bell) published Technical Bulletin (TB) 407-TB-08-81 to approve and encourage the use of contact enhancer Stabilant 22. Bell has now listed Stabilant 22 in the standard practice manual as a consumable material and it should be applied to the applicable electrical connectors whenever possible.
407 - Paravion External Load Mirror Specific Maintenance Instructions
SDR #: 20200226023
Subject:
The manufacturer is Paravion Technology Inc. During a daily inspection, it was noticed that the external load mirror was missing. Upon further inspection, it was discovered that the arm that attaches the mirror to the aircraft was broken in half. Upon examining the remaining portion of the broken shaft, it was discovered that the set screw that is used to position and hold the arm in place had caused deep damage to the arm. It appears that a crack may have started from the damaged area. After researching this part in the Supplemental Type Certificate (STC), it was discovered that this STC does not contain any instructions for continued airworthiness, inspection criteria or damage limitations. As a result, this installation was not undergoing any regular inspections.
Transport Canada Comments:
The details of this service difficulty report and information about the STC instructions for continued airworthiness (ICA) were sent to Paravion Technology Inc. for review. The ICA maintenance instructions were determined to be incomplete therefore Paravion Technology Inc. published Service Bulletin SB-206-407EM-20200407. The SB is applicable to Bell model 206 series or 407 helicopters equipped with Paravion Technology Inc. external mirror STC installations and provides specific maintenance instructions. Owners and operators of the applicable Paravion Technology Inc. external mirror STC installations are encouraged to review and complete the instructions of SB-206-407EM-20200407.
429 - Expandable Blade Bolt Loose Pivot Pin
SDR #: 20200605011
Subject:
It was reported to Bell that during a main rotor blade removal, the expandable blade bolt pivot pin fell out on the bench. As a result, the compression handle became detached from the core pin. Inspection and comparison to the other bolts revealed that the end of the pivot pin had not been swaged.
Transport Canada Comments:
Through investigation, Bell has determined that a lack of swaging could exist on the pivot pin of some expandable blade bolt assemblies part number 429-310-004-101. As a result of the investigation, Bell has published Alert Service Bulletin (ASB) 429-20-53 to provide instructions for inspecting and in some cases replacing the expandable blade bolt. Transport Canada encourages owners, operators and maintainers to review and accomplish the instructions provided in ASB 429-20-53.
505 - Effects of Overfilling Engine Reduction Gearbox Oil
SDR #: 20190911012
Subject:
Minor edits have been made to the text below taken from the Service Difficulty Report’s Problem Description. Transport Canada Civil Aviation reserves the right to edit for spelling, grammar and punctuation to increase comprehension.
It was reported to Bell that a helicopter was flying in hover 0.2 hours after the completion of TF90 inspection when the pilot observed high engine oil temperatures and zero engine oil pressure. (The engine accessory gearbox reportedly got so hot that it bubbled the sealant used to seal the top of the freewheel housing to engine gearbox interface). The helicopter landed without incident. A preliminary inspection revealed that the engine oil tank was full and no loss of oil was observed. The engine manufacturer was notified and initial thoughts suggest that the engine oil pump had failed.
Transport Canada Comments:
The conditions experienced in this Service Difficulty Report (SDR) have been attributed to excess oil in the engine reduction gearbox. As part of the investigation conducted by Bell and Safran HE, Information Letter 505-IL-19-05 was published to share information about the current findings. The Information Letter has a list of possible conditions if excess oil is present in the engine reduction gearbox. The letter also directs readers to references of existing procedures in the Rotorcraft Flight Manual and Maintenance Manual to maintain the proper oil level.
429 - Pitot-Static System Fittings Loose Hardware
SDR #: 20161121001
Subject:
Minor edits have been made to the text below taken from the Service Difficulty Report’s Problem Description. Transport Canada Civil Aviation reserves the right to edit for spelling, grammar and punctuation to increase comprehension.
While performing a 24 month pitot-static check, it was discovered that many pitot-static B nuts were only finger-tight and could be loosened by hand.
Transport Canada Comments:
Transport Canada has received several service difficulty reports for the Bell 429 model helicopter with loose hardware on the pitot-static system. The loose hardware was investigated and found to be the result of incorrect tightening of the plastic fittings. Subsequently, Bell has amended the torque procedures for all plastic fittings in the instructions for continued airworthiness. Be aware that the torque values identified as standard practices can be different than the manufactures’ instructions for a specified task. The Caution and Note sections for each procedure should be read carefully and adhered to as they may differ from one job to the next.
Example of the plastic fittings that can be found in a pitot-static system.
407 - Expandable Main Rotor Blade Bolt Pivot Pin Movement
SDR #20170209010
Subject:
The pivot pin in the expandable blade bolt assembly was found out of position.
Transport Canada Comments:
Due to a lack of swaging, the expandable main rotor blade bolt pivot pins installed on some model 407 and 427 helicopters were found to have movement. The expandable main rotor blade bolt can be installed by either the Bell Helicopter Textron Kit Installation Instruction or the Paravion Technology Inc. aftermarket Supplemental Type Certificate (STC). Bell Helicopter Textron Canada has issued Alert Service Bulletins (ASB) 407-17-115 and& 427-17-41 to provide a detailed visual and load test inspection of the pivot pins.
206B - Cracked Tension Torsion Strap Urethane Coating
SDR #20170808010
Subject:
During a routine 3 year calendar tension/torsion strap change, cracks were found in the urethane casing of the strap. This exposes the stainless steel wires to the elements.
Transport Canada Comments:
Cracks in the urethane protective coating of any tension/torsion strap could lead to internal corrosion of the straps. Visual inspection of the straps should be conducted whenever the opportunity is available to do so. The Australian Civil Aviation Authority has issued Airworthiness Bulletin 63-009 recommending inspection of the straps for cracks in the coating. Similarly, Bell Helicopter has issued Alert Service Bulletin 206-13-130 introducing a reduction to the life limit and removal of some part numbered straps. If cracks are found in the urethane coating of any manufactures tension/torsion straps please submit a Service Difficulty Report for each occurrence.
206B - Cracked Aft Fuselage Frame
SDR #20160715005
Subject:
During a scheduled 100 hour airframe inspection, while looking through the inspection panel of the most-aft section of the airframe, the aircraft maintenance engineer found a suspected crack approximately 6 mm long. The crack was discovered in the aft frame near the upper right-hand tail boom attachment fitting, specifically fuselage station 205.0, water line 75.0 at the 2:00 position, when viewed from the rear, looking forward. The crack was in a difficult position to inspect with a magnifying glass because it was nestled behind a reinforcement angle. A liquid penetrant inspection was performed to confirm the suspected crack. The tail boom was removed and the crack was again confirmed. The liquid penetrant had seeped through from the front side and was visible from the aft side. The frame was paint stripped and the crack was measured to be approximately 33 mm long. The origin of the crack is unknown, there has been no recent operational incident and it was found on the compression side of the tail boom.
Transport Canada Comments:
As described in this service difficulty report, there was likely no operational incident that can be considered root cause for the frame cracking. Age and fatigue may have contributed however the original design and/or the outdated "pressed" aft fuselage bulkhead, were the probable cause of why it cracked. Bell Helicopter has released Technical Bulletin TB 206-12-199 Revision A to address this area of concern. Specifically, part two of the technical bulletin introduces and provides instructions for installation of a new machined aft fuselage bulkhead that is made of thicker material. The new bulkhead is a direct replacement on the 206A/B.
407 - Fractured Tail Skid
SDR #20160614023
Subject:
The tail skid (stinger) was missing after the pilot shut down and performed a walk around of the aircraft. The stinger was found several feet away in a work camp. The part had been installed 15 months prior and accumulated 602 hours since new as part of a company Bell 407 fleet replacement program following previous stinger failures.
Transport Canada Comments:
Bell Helicopter previously issued Information Letter 407-04-80 to inform owners and operators of a serial number specific recall for tail skids that did not meet the required hardness. The tail skid identified in the Service Difficulty Report #20160614023 was not listed in the serial numbers range identified in the Information Letter. Transport Canada Civil Aviation wishes to remind both Pilots and Aircraft Maintenance Engineers to remain vigilant when performing preflight and scheduled inspections. This area could be susceptible to environmental conditions; inspection for corrosion in addition to mechanical damage should not be overlooked. Bell Helicopter has been notified of this occurrence for further investigation.
Fractured tail skid, it appears the crack originated from the through bolt hole at the vertical stabilizer attachment point.
429 - Pitch Restraint Spring Debonding
SDR #20160128004
Subject:
The pilot reported an abnormal vibration and "shifting" that was felt while the aircraft was in a hover and during flight. A precautionary landing was carried out. The pilots observed that the transmission was resting on the "pin back-up mounts". An Aircraft Maintenance Engineer was dispatched to inspect the aircraft and a subsequent flight test was carried out to confirm the main rotor transmission restraint condition. The aircraft was allowed to return to base with a speed restriction.
Debonding between inner and outer member of the Pitch Restraint Spring assembly was found. The Pitch Restraint Spring assembly did have an Alert Service Bulletin (ASB) 429-13-10 issued in April 2013, limited to a certain quantity of units, however this unit was not included.
Transport Canada Comments:
Following the initial issue of ASB 429-13-10, Bell Helicopter and Transport Canada continued to receive service difficulty reports for debonding of the pitch restraint spring 429-310-201-105 from the pylon pitch restraint spring assembly 429-010-204-101. Following an investigation, it was found that as ambient temperatures decrease, the risk of debonding may increase. As a result, Bell Helicopter has revised ASB 429-13-10 now dated 7 November 2016 to introduce a recall of suspect pitch restraint spring assemblies and to upgrade the restraint spring configuration to prevent future occurrences of debonding.
Specific area on the Pylon Pitch Restraint Spring Assembly where the debonding between the inner and outer member can be found.
Bell Textron - USA
212 - Fractured Lug on the Swashplate Inner Ring
SDR #: 20211005009
Subject:
Swashplate inner ring part number 204-011-402-021 was found to have one lug broken off. It is evident that the lug was fractured for some time. Bell Helicopter has been notified of this service difficulty report. The subject parts have been placed into quarantine stores.
Transport Canada Comments:
Bell received reports of cracked or broken lugs on the swashplate inner ring, and to raise awareness, have subsequently published Information Letter (IL) 212-22-74. The IL is addressed to owners and operators of model 204B, 205, 205B, 212 and 412 helicopters. It emphasizes the importance of the scheduled daily and 25-hour inspections (as applicable). The IL also provides a reminder of the importance of the caution notice found in the disassembly instructions of the applicable Maintenance & Overhaul (M&O) or Component Repair & Overhaul (CR&O) manual. The caution is a reminder that a retaining compound was used during the installation process, and that in order to prevent damage to the lug, it must be supported when driving out the bolts. To raise awareness of this service difficulty, Transport Canada Civil Aviation (TCCA) encourages the owners and operators of the affected helicopter models to review Bell IL 212-22-74 and to remain vigilant during the inspection and disassembly of the swashplate and support assembly.
Picture 1 – Fractured lug on the Swashplate inner ring
USA, 212 - Updated Bell Medium Main Rotor Gearbox Spider Inspection
SDR #: 20200127013
Subject:
The transmission was removed from the aircraft for inspection and conversion to 212 HP status. During this inspection, the spider was found to have a broken lug. There was no prior indication of this failure. This part is being sent to an independent facility for review.
Transport Canada Comments:
Bell has received multiple service difficulty reports (SDRs) of a cracked or broken lug found on the main rotor gearbox spider. Following the investigation of the parts, Bell concluded that an update to the manufacturing planning and the component repair and overhaul (CR&O) instructions for all Bell Medium Helicopters was required. Once revised, the CR&O will have updated instructions for the magnetic particle method used to inspect the spider. Transport Canada Civil Aviation (TCCA) encourages operators and maintainers of Bell Medium Helicopters to review the latest revision of the applicable CR&O prior to inspecting the main rotor gearbox spider by magnetic particle method.
Main rotor gearbox spider with the broken lug separated from the part
Dart Aerospace, Equipment
Dart Aerospace Spacedoor Dislodged on Bell 412
SDR #: 20180306004
Subject:
Minor edits have been made to the text below taken from the Service Difficulty Report’s Problem Description. Transport Canada Civil Aviation reserves the right to edit for spelling, grammar and punctuation to increase comprehension.
Shortly after departing for a maintenance test flight, the right-hand cargo door dislodged and eventually departed the aircraft. Maintenance personnel describe the cargo door as dislodging from the lower cabin door track. It first came out from the aft portion then moving forward along the entire length of the door.
After a few moments of deflecting 8 to 12 inches outboard of the aircraft, the cargo door let loose of the upper track and departed the aircraft. After losing both emergency pop-out windows but prior to making contact with the rotor system, the cargo door became entangled with the external hoist, caught up where the forward emergency window would have been. After the aircraft and crew landed safely, the aircraft was inspected and determined to be airworthy.
Transport Canada Comments:
Dart Aerospace conducted an investigation and concluded that this Service Difficulty was a singular event occurrence. Subsequently, Dart issued Service Bulletin (SB) 18-1 as a precautionary measure with instructions to conduct an operational check and adjustment of the D412-694-011 Spacedoor installation. The Dart Instructions for Continued Airworthiness document ICA-D412-694 details the inspections recommended by the SB as well as the additional scheduled maintenance tasks. Operators can consult Transport Canada (TC) approved Supplemental Type Certificate SH05-10 for a list of the various aircraft type/models for the Spacedoor installation. Should any abnormalities be found with this installation, TC wishes to remind operators to submit a Service Difficulty Report for further evaluation.
Eurocopter France
EC 120 B - Worn Tail Rotor Drive Splines and Coupling
SDR #20171103022
Subject:
During a transmission removal from the aircraft, it was found that the splines of the transmission output wheel and coupling were excessively worn. The coupling which is part of an Air Comm Corporation (Air Comm) air conditioning kit (Supplemental Type Certificate (STC) SR00491DE) was worn to a point that tail rotor drive shaft failure was inevitable.
Transport Canada Comments:
STC SR00491DE is for installation of an Air Comm air conditioning kit on an Airbus Helicopters model EC120B helicopter. Similar to this Service Difficulty Report (SDR), Air Comm received reports of wear at the spline joint that consists of the air conditioner drive pulley and the tail rotor output wheel. This spline joint is an integral piece of the power transmission components responsible for the tail rotor drive. Air Comm published Service Bulletin (SB) EC120-111815 to specify an inspection of the pulley-output wheel interface for wear. The Federal Aviation Administration (FAA) has mandated inspection of affected aircraft with Airworthiness Directive (AD) 2017-06-11. Owners, operators and maintainers should be aware that the corrective action and compliance time specified in the SB and AD are different. In addition, the FAA AD requires the inspection results to be reported to the FAA.
Example of the wear found on the tail rotor output wheel spline
Helicopter Technology Company, Equipment
Delamination of Main Rotor Blade Abrasion Strip
SDR #20160613017
Subject:
During the 100 hour inspection of the main rotor blades, as required by the Helicopter Technology Company Service Notice 2100-8 revision 2, all five blades were found to have delamination of leading edge abrasion strip. All of the blades have a total time since new of 97.2 hours and 2074 torque events. The Main Rotor Blades are being sent back to manufacturer.
Transport Canada Comments:
In the elapsed calendar time since the release of Service Notice 2100-8 revision 2, operators have continued to report delamination or disbonding of the abrasion strip on Helicopter Technology Company Main Rotor Blades. The service difficulty reports have also indicated that failure to detect the delamination or disbonding when inspecting has resulted in departure of the Abrasion Strip in-flight. Due to these reports, Service Notice 2100-8R2 was superseded by Mandatory Service Bulletin (MSB) 2100-8R3 dated 29 April 2016. The MSB revises the frequency and requirements for accomplishing the inspection as well as introduces a modification that will be mandated by a future published Federal Aviation Administration (FAA) Airworthiness Directive.
Main Rotor Blade without leading edge abrasion strip following an in-flight departure.
Robinson
ROBINSON, R44 - R44 Loose Tail Rotor Blade Tip
SDR #: 2022612257152
Subject:
Tail rotor tip cap debonded and was thrown from tail rotor blade shortly after landing. The bonded area of tail rotor tip cap found to be severely corroded. A tap test of bonded area (as per R44 SL-82) showed no evidence of debonding during last inspection. It was observed during testing that tap test method is not a reliable way to determine tip cap debonding. With the tip cap loosely fitted, the tap test was tried and found no change in sound between this blade and a new blade, despite having no bonding. There was a possible rotor overspeed that may have caused extra stress required to cause separation, however the pilot is unsure if the overspeed had occurred.
Transport Canada Comments:
Robinson Helicopter Company (RHC) has received reports of tail rotor blade tips coming loose. The cause of the loose tip was determined to be a debonding of the tail rotor blade tip due to corrosion. A debonded tip could cause the helicopter to experience severe tail rotor vibrations. RHC has published R44 Service Bulletin SB-112 to provide instructions for a recurring inspection and replacement of affected tail rotor blades. Transport Canada Civil Aviation recommends that R44 series helicopter owners, operator and maintainers review and accomplish SB-112.
ROBINSON, R44 II - R44 II Main Rotor Gearbox (MRGB) Input Yoke Retaining Nut Loss of Torque
SDR #: 20200221010
Subject:
In flight, the rotor revolution per minute (RPM) indication fluctuated and the low rotor RPM warning was observed. The pilot in command did a precautionary landing. An inspection revealed a loss of torque at the AN320-8 nut securing the C908-1 yoke to the MRGB input pinion. Part of the MS24665-210 cotter pin securing the nut in place, was found below the MRGB. The nut was found backed off on the pinion thread. Damage to the pinion and yoke mating splines was noted. Excessive clearance between the yoke and pinion damaged the two parts and allowed the yoke to misalign the contact with the Hall effect senders. The Hall effect senders provide signal to the rotor tachometer gauge and to the low rotor RPM warning system.
Transport Canada Comments:
Robinson Helicopters previously issued Service Bulletin (SB) R44 SB-74 to acknowledge reports of torque loss of the AN320-8 nut and provide corrective action. The rotorcraft Affected section of the SB identifies specific R44 and R44 II aircraft serial numbers, the aircraft serial number from this Service Difficulty Report (SDR) is not listed in the SB. Transport Canada has forwarded the details of this SDR to Robinson Helicopters and encourages operators and maintainers to review R44 SB-74 even if the serial number of the aircraft is not within the serial numbers specified in the SB.
R44 II - Robinson R44 II Throttle Link
SDR #: 20190423010
Subject:
Minor edits have been made to the text below taken from the Service Difficulty Report’s Problem Description. Transport Canada Civil Aviation reserves the right to edit for spelling, grammar and punctuation to increase comprehension.
During run up, it was noted that the idle was high (around 70% belts engaged). Upon inspection, it was found that the bearing had come out of the part number (P/N) B564-2 link at the servo end.
Transport Canada Comments:
It should be noted when inspecting or replacing throttle link P/N B564-2 for the R44 and R44 II model helicopters, that the Robinson Helicopter Company has published multiple service bulletins for this service difficulty.
R44 Service Bulletin (SB)-62 identifies a failed throttle link where the bearing separated from the housing. Compliance with this SB involves the installation of a large-diameter washer to prevent loss of control if a bearing fails. The incorporation of the large-diameter washer is also published in the Robinson Illustrated Parts Catalog throttle control installation
R44 SB-71 introduces a throttle link with a TeflonTM-lined steel bearing race designed to prevent race separation from the link body. This SB requires replacing the earlier links having aluminum-bronze races while retaining the large-diameter safety washer requirement.
Figure 1: Pre R44 SB-71 throttle link P/N B564-2 having aluminum-bronze bearing races.
Figure 2: Post R44 SB-71 throttle link P/N B564-2 having TeflonTM-lined steel bearing races.
R44 II - Concorde Battery Electrical Short
SDR #: 20190318029
Subject:
Minor edits have been made to the text below taken from the Service Difficulty Report’s Problem Description. Transport Canada Civil Aviation reserves the right to edit for spelling, grammar and punctuation to increase comprehension.
The pilot returned to base and reported having to re-set the alternator after the light had illuminated several times in flight. The aircraft was due for a 100 hour inspection anyway, so the inspection was carried out. During the 100 hour inspection, it was found that the battery under the co-pilot seat was melted in two places. The alternator was close to overhaul, so it was replaced as a precaution. It can’t be sure that the battery caused the alternator issues, but it appears the battery shorted internally. The pilot did not report any odd smell in the aircraft.
Transport Canada Comments:
Concorde batteries can be commonly found installed in many different aircraft makes and models. Inspection instructions for the battery are often found in the aircraft manufacturer’s publications; however, it is important to note that battery manufacturers also publish instructions for continued airworthiness. The instructions for continued airworthiness for the battery should be consulted when each maintenance program is developed. For this battery installation, no internal checks are required and it appears that no external defects were noted prior to the battery failure. If a similar situation is encountered, Transport Canada encourages operators and maintainers to continue to submit Service Difficulty Reports in order to further evaluate this potential defect.
Image1: Battery as it was found during inspection when it was installed in the aircraft.
Image2: Battery opened for inspection and the subsequent electrical short observed.
R44 II - Defective R44 II Engine Air Induction Hose
SDR #: 20190611012
Subject:
Minor edits have been made to the text below taken from the Service Difficulty Report’s Problem Description. Transport Canada Civil Aviation reserves the right to edit for spelling, grammar and punctuation to increase comprehension.
During a scheduled maintenance of an R44 II, it was noted that Robinson Helicopter Company (RHC) Service Bulletin (SB) R44 SB-97 Part A (required within one flight hour) had not yet been accomplished. Visual inspection of the installed hose part number (P/N) A785-31 found evidence of separation between inner and outer layers as described in the SB. The “crinkling” noise was also evident. The defect was reported to the manufacturer (RHC), with two pictures and an audio file to confirm the “crinkling” noise as the indication of the defective hose. It was also noted to RHC that this particular P/N A785-31 hose did not fall within the effectivity range of R44 SB-97 (as the aircraft serial number was not applicable, and the hose was installed prior to the “may through November 2018” effectivity range). It is unknown if, though probable, this specific hose is “original equipment since aircraft manufacture”. Robinson’s technical support replied to the email and requested the discrepant hose be returned to RHC for evaluation which we will comply with.
Transport Canada Comments:
RHC issued SB-97 as a corrective action following reports of separation between the inner and outer layers of the engine air induction hose. The separation of the inner layer could block engine induction air flow. The Federal Aviation Administration (FAA) has mandated SB-97 with Airworthiness Directive (AD) 2019-12-18. Service Difficulty Report (SDR) 20190611012 describes the identification of a defective hose however, the aircraft serial number and installation date of the air induction hose are not within the required actions of FAA AD 2019-12-18. Transport Canada Civil Aviation (TCCA) has subsequently contacted the FAA regarding AD 2019-12-18 with this information. At the time of writing, this is the only SDR of a defective air induction hose. TCCA will continue to monitor and would like to remind operators and maintainers to submit an SDR for any reportable service difficulty found.
Image showing the inner layer of the engine air induction hose.
Tail Rotor Driveshaft Bearing Overheating
SDR #20160913004
Subject:
A Robinson R66 helicopter was cooling down after landing when the pilot reported a growling noise followed by a grinding sound. Further investigation revealed that the forward tail rotor drive shaft bearing housing had failed and caused the fan wheel to also fail. The operator was in correspondence with the Robinson Helicopter Company and determined the bearing was found to have broken loose from the bearing housing. The outer race of the bearing was spinning inside the housing causing heat and failure of the housing. The bearing was released from the housing and the drive shaft was released from its support which caused the fan to contact its housing which in turn sheared the fan from the drive shaft.
Transport Canada Comments:
The Robinson Helicopter Company has received additional reports of overheating F172-1 hanger bearing assemblies and has subsequently issued R66 Service Bulletin SB-20 dated 7 November 2016 as a corrective action. It is important to note that SB-20 supersedes R66 Service Bulletin SB-14 and requires upgrading the bearing assembly in addition to revising the requirements for an improved sealant application.