Aviation Missile Command (AMCOM) Safety of Flight Message Summaries

 

 

In brief format, this page gives the Summary of Problem as indicated in the appropriate Safety of Flight (SOF) issued by Commander, Aviation Missile Command (AMCOM).    Note: Safety of Flight Messages never expire, remaining valid indefinitely unless rescinded or superceded. In many instances, SOF Messages are superceded when incorporated in a follow-on Technical Bulletin (TB). In such cases, the TBs remain valid until rescinded or superceded. The document superceding the SOF Message is as equally important in maintaining airworthiness of the fleet as the original Safety of Flight Message itself.

 

 

 

SOF CH-47-06-03, 8 March 2006 Title: Aft Rotor Blade, Root End Fiber Distortion. Summary: During Boeing investigations of a Royal Air Force cracked H-47 rotor blade, and a US Army H-47 rotor blade Quality Deficiency Report (QDR), Boeing found the rotor blade manufacturing process generated distortion in some of the composite material fiber wraps around the rotor blade root end bore. Instead of the root end bore fibers curing in the resin with one smooth and continuous direction, cured fibers sustained wrinkled shaped distortions. Rotor Blade fiber distortion wrinkles preclude the rotor blade from being able to achieve blade fatigue life. [Full Text Photograph download Slow? Right Click and save target as...(819 Kb).]

 

 

SOF CH-47-05-02, 4 January 2005 Title: Rotor Blade, Root End Fiber Distortion. Summary: During Boeing investigations of a Royal Air Force cracked H-47 rotor blade, and a US Army H-47 rotor blade Quality Deficiency Report (QDR), Boeing found the rotor blade manufacturing process generated distortion in some of the composite material fiber wraps around the rotor blade root end bore. Instead of the root end bore fibers curing in the resin with one smooth and continuous direction, cured fibers sustained wrinkled shaped distortions. Rotor Blade fiber distortion wrinkles preclude the rotor blade from being able to achieve blade fatigue life. [Full Text Photograph download Slow? Right Click and save target as...(819 Kb).]

 

 

SOF CH-47-05-01, 4 January 2005 Title: Swashplate Rotating Ring. Summary: Recent inspection of over one hundred H-47 swashplate rotating rings in overhaul revealed the following anomalies: (1) fatigue cracks emanating from the bearing retention flange; (2) a serial number (SN) from an unapproved source; and (3) maintenance induced mechanical damage. The swashplate rotating ring life is based on a specific usage spectrum. Loads derived from this spectrum were then utilized during fatigue testing to substantiate the current rotating ring life. Consequently, the fatigue cracked rotating rings, with relatively low flight hours, were most likely cracked under loads and airspeeds in excess of currently authorized limits. In addition, mechanical damage appearing to have been induced from drifts, punches, and/or screwdrivers on the rotating ring, inner diameter, may develop into further crack initiation sites. [Full Text ]

 

 

SOF CH-47-04-01, 5 February 2004 Title: Swashplate Bearing, Forward and Aft. Summary: Safety of Flight message, CH-47-03-01, established inspection requirements for the H-47 Forward and Aft Swashplate Assemblies. These inspection requirements included submitting a grease sample for analysis by the Army Oil Analysis Program (AOAP). Inconsistent results from this program do not show correlation between grease sample results and actual swashplate assembly damage/condition. The AOAP grease sampling results can not be considered a reliable method to indicate pending bearing failure or even used to assess the condition of the swashplate bearings. This message is effective until rescinded or superseded. [Full Text ]

 

 

SOF CH-47-03-01, 4 October 2002: Title: Swashplate Bearing, Forward and Aft. Summary: During ground run, a CH-47D Chinook aircraft experienced an aft rotating ring drive arm lug failure that resulted in a Rotor Blade strike to the fuselage, upper tunnel cover and other significant aircraft damage. Investigation has revealed that this incident was the end result of an Aft Swashplate Bearing failure. Superseded by SOF CH-47-04-01. [Full Text ]

 

 

SOF CH-47-02-06, 19 June 2002: Title: Inspection of Combining Transmissions. Summary: A unit reported that after experiencing a debris screen latch, they found plastic type debris in the combining transmission oil filter. Analysis of the debris revealed that it was plastic media. It has been determined that this material is the result of the use of plastic media blast procedure by CCAD to remove surface coatings from the housing assemblies. This procedure can leave particles inside the transmission that could interfere with necessary oil flow. [Full Text ] Superceded by TB 1-1520-240-20-148.

 

 

SOF CH-47-02-05, 22 March 2002: Title: Inspection of the Rotary Wing Head Tie Bar Assembly. Summary: CH-47-02-03 was issued on 24 January 2002 requiring inspection of the Tie Bar Assembly and Rotor Tachometer. With regard to the tie bar inspections, the intent of the message was to inspect for cracked plates and deformation of washers only. Scores, scratches, buckling/separation of plates, and other minor installation damage are not grounds for failing this special inspection. The 1200 hour operating time special inspection will still be required. At the time the 1200 hour operating time special inspection is due, all tie bars that fail the inspection criteria of TM 55-1520-240-23, Task 5-23.1.1 (H-47D/F), or TM 1-1520-252-23, Task 5-31 (MH-47E), will require replacement. [Full Text] Superceded by TB 1-1520-240-20-146.

 

 

SOF CH-47-02-04, 7 February 2002: Title: Inspection of Forward Pivoting Actuator to Swashplate attachment hardware for proper installation. Summary: A Quality Deficiency Report has been received from the field documenting that the wrong bearing was installed in the Forward Pivoting Actuator Upper Attachment. The apparent cause was an error in the parts manual; while this wrong bearing fits properly in the actuator, its inner diameter is too large for the mating bolt. [Full Text] Superceded by TB 1-1520-240-20-145.

 

 

SOF CH-47-02-03, 24 January 2002: Title: Inspection of the Rotary Wing Head Tie Bar Assembly and Rotor Tachometer. Summary:    History - CH-47-02-02 was issued on 24 January 2002 requiring inspection of the Tie Bar Assembly and Rotor Tachometer. This message supercedes the requirements in CH-47-02-02. Changes have been made to para 1c, 8a, 8b, 9a, and 10d.    (1) Tie Bar Plate failure - Reports from the field on Tie Bar Assemblies indicate that Tie Bar Plate cracks have occurred much earlier than the retirement life of 8,693 hours. Even though the Tie Bar Assembly is currently inspected at 1,200 hours and at the 2,400 hour overhaul, it is possible that some fielded Tie Bars may have Tie Bar Plates which have cracked.    (2) Tie Bar over speed damage - testing has shown that initial deformation of the Rotary Wing Head Tie Bar Assembly may occur at a point just above 111 percent rotor rpm. Currently, the 145ES008 Rotor Tachometers (all H-47D/F) and Multi Function Displays (MFD) (MH-47E) indicate 115 percent rpm as the maximum transient rotor speed limit. Because of this, some Tie Bar Assemblies may have already been damaged due to exceeding 111 percent rpm. [Full Text ] Superceded by TB 1-1520-240-20-141.

 

 

SOF CH-47-02-02, 24 January 2002: Title: Inspection of the Rotary Wing Head Tie Bar Assembly and Rotor Tachometer. Summary:    (1) Tie Bar Plate Failure - reports from the field on Tie Bar Assemblies indicate that Tie Bar Plate Cracks have occurred much earlier than the Retirement Life of 8693 hours. Even though the Tie Bar Assembly is currently inspected at 1200 hours and at the 2400 hour Overhaul, it is possible that some fielded Tie Bars may have Tie Bar Plates which have cracked.    (2) Tie Bar Over Speed Damage - Testing has shown that initial deformation of the Rotary Wing Head Tie Bar Assembly may occur at a point just above 111 Percent Rotor RPM. Currently, the 145ES008 Rotor Tachometers (all H-47D/F) and Multi Function Displays (MFD) (MH-47E) indicate 115 Percent RPM as the Maximum Transient Rotor Speed Limit. Because of this, some Tie Bar Assemblies may have already been damaged due to exceeding 111 Percent RPM. [Full Text ] Superceded by CH-47-02-03.

 

 

SOF CH-47-02-01, 24 January 2002: Title: Swashplate Lower Seal Retainer self-locking nut inspection. Summary: A field unit has discovered the use of self-locking nut P/N NAS 1758-l6 on the Swashplate Lower Seal Retainer. The overall height of these nuts does not allow full engagement of the locking features in the nut. Use of the incorrect nuts could cause damage to the stationary ring due to inadequate clearance between the nut and the stationary ring, especially if the nut were to back off the bolt. In addition, if a nut or bolt were to back off and drop below the Swashplate Assembly, the possibility exists that a linkage could be jammed by the fastener, which could cause a partial or complete loss of rotor control. [Full Text] Superceded by TB 1-1520-240-20-144.

 

 

SOF CH-47-01-03, 16 February 2001: Title: Ungrounding requirements for aircraft with incorrectly installed Droop Stops. Summary: While conducting an accident investigation, incorrectly installed Droop Stops were discovered. Safety of Flight Message CH-47-01-02 was issued calling for a one time inspection on Forward and Aft Droop Stops for proper installation. [Full Text] Superceded by TB 1-1520-240-20-137.

 

 

SOF CH-47-01-02, 3 February 2001: Title: Inspection of Droop Stops. Summary: While conducting an accident investigation, incorrectly installed Droop Stops were discovered. [Full Text] Superceded by TB 1-1520-240-20-136.

 

 

SOF CH-47-01-01, 22 December 2000: Title: Inspection of Aft Rotor Head Assemblies and Engine Cross Shaft Adapter Assemblies. Summary: Two Deficiency Reports were received which indicated that a CH-47D unit was issued MH-47E closed loop items through the normal supply system. Certain MH-47E items are placed on the closed loop list because there is a reduction in finite life due to the MH-47E flight spectrum. A thorough review of all closed loop items has revealed that 36 engine Cross Shaft Adapter Assemblies (P/N 145D3500-16/-17) and one Aft Rotor Hub (P/N 114R2050-36) could have escaped into the CH-47D supply system. [Full Text] Superceded by TB 1-1520-240-20-134.

 

 

SOF CH-47-00-07, 26 September 2000: Title: Combining Transmission Cooling Fan Drive Shaft inspections. Summary: A MH-47E aircraft experienced a failure of the Combining Transmission Cooling Fan Drive Shaft, P/N 145D5319-5. Failure of this shaft was contained by the "stove pipe". But, since the Cooling Fan was no longer operating, the oil temperature of the Combining Transmission and both Engine Transmissions exceeded the operating limits. This high temperature condition required landing of the aircraft as soon as possible without delay and replacement of the Combining and both Engine Transmissions. Currently there is an ongoing investigation as to the cause of the Fan Shaft failure. [Full Text] Superceded by TB 1-1520-240-20-129.

 

 

SOF CH-47-00-06, 8 May 2000: Title: APU Containment Device. Summary: Safety of Flight Message CH-47-00-01 was issued in October 1999. The message directed the establishment of a retirement life based on starts and operational restrictions for aircraft with APUs which had reached specified start-counts. Subsequently a safety containment device has been designed and tested. This device can fully contain the debris from a compressor wheel burst. This message is effective until rescinded or superseded. [Full Text]

 

 

SOF CH-47-00-05, 1 May 2000: Title: Inspection of Pitch Housing. Summary: Quality Deficiency Reports reported new Pitch Housings were received from supply that had surface gouges and nicks. Investigation revealed that the defects were beyond serviceability limits and that the defects were present when received from the manufacturer, Tura machine company. Since Tura's processing and inspection procedures are suspect all subject parts obtained from them require inspection. [Full Text] Superceded by TB 1-1520-240-20-120.

 

 

SOF CH-47-00-04, 27 January 2000: Title: Inspection of Engine Transmissions Records for suspect gears and replacement of suspect transmissions. Summary: During Boeing Helicopter overhaul of international CH-47 Engine Transmissions (Part Number 145D6300), three instances of cracked gears have been found. These cracks have been found in the Bevel Gearshaft (Part Number 145D6301) and Spiral Gearshaft (Part Number 145D6302). None of these cracks have resulted in an Engine Transmission failure. [Full Text] Superceded by TB 1-1520-240-20-117.

 

 

SOF CH-47-00-03, 6 December 1999: Title: Increase of operating limitations for Forward and Aft Transmission Gear/Bearing Assemblies identified by serial number prefix "VB". Summary: Safety of Flight Messages CH-47-99-02, CH-47-99-03, CH-47-99-04, and CH-47-99-05 grounded all H-47 aircraft, provided inspection requirements, and released some aircraft for restricted flight. The aircraft released for restricted flight contained Forward and Aft Transmissions which had all Planetary Gear Bearing Assemblies identified with the serial number prefix "VB". The restriction limited flight operations to a maximum of 80 percent dual engine torque. Analytical investigations, testing of discrepant gear/bearing assemblies, results of gear bearing assembly inspections, and research of historical data have led to a risk determination that the 80 percent dual engine torque operating limitation imposed by Safety of Flight Message CH-47-99-04 can be increased to the new operating limitation identified in paragraph 9. [Full Text] Superceded by TB 1-1520-240-20-116. See also CH-47-99-05, CH-47-99-04, CH-47-99-03, CH-47-99-02.

 

 

SOF CH-47-00-02, 8 November 1999: Title: Revision to SOF CH-47-00-01, Operational Restrictions and revision to historical records for T-62T-2B Auxiliary Power Unit (APU). Summary: SOF Message CH-47-00-01 contained incorrect funding and reimbursement instructions. [Full Text] Superceded by TB 1-2835-205-20-4.

 

 

SOF CH-47-00-01, 8 October 1999: Title: Operational Restrictions and revision to historical records for T-62T-2B Auxiliary Power Unit (APU). Summary:    Background:    (1) In 1995 there was an incident where an APU Compressor Wheel burst during start-up (see reference 13a). The failure was attributed to fatigue which originated from boltholes on the back of the wheel (see reference 13b). The damaging fatigue cycles are incurred by starting the APU.    (2) Previously, APU starts have not been recorded and have not been maintained and transferred with the APU. Currently, start cycles for a particular compressor wheel are estimated based on the hours logged on the aircraft records. The estimates use four APU starts for one flight hour.    (3) APUs overhauled since November 1996 were subject to magnetic particle inspection of the compressor wheel for fatigue cracks and are given a one-time life extension of 2,100 starts since inspection at Depot (see "note" in para 9). Only APUs specifically listed in paragraph 9b below are authorized to operate up to 525 hrs or 2,100 starts since inspection (SSI). Future APUs from Depot shall have forms and records reflecting this new retirement life.    (4) The data from these inspections indicate that with no life limit, which is the current situation, the T-62T-2B APU compressor wheel has a high probability of catastrophic failure. In the event of an impeller burst, up to three pieces of the impeller may exit the APU radially. These pieces will weigh up to 1.1 pounds each and will be moving at extremely high velocity.    (5) A new design has been approved for the compressor wheel which will have a greater fatigue life. The new wheels will be incorporated by OLR team using MWO or by Depot. [Full Text] Revised by CH-47-00-02. Superceded by TB 1-2835-205-20-4. See also CH-47-00-06.

 

 

SOF CH-47-99-05, 13 September 1999: Title: Replacement of suspect Forward and Aft Transmission Assemblies with ones that have been inspected and cleared for operation. Summary: Safety of Flight Messages CH-47-99-02, CH-47-99-03, and CH-47-99-04 grounded all H47 aircraft, provided inspection requirements and released for limited flight aircraft with 100% Gear/Bearing assemblies identified with the prefix "VB". This message provides instructions for the issue of inspected and repaired transmissions and the return of transmissions requiring inspection and repair. [Full Text] Superceded by TB 1-1520-240-20-115. See also CH-47-00-03, CH-47-99-04, CH-47-99-03, CH-47-99-02.

 

 

SOF CH-47-99-04, 26 August 1999: Title: Inspection of H-47 aircraft for Forward and Aft Transmission Gear/Bearing Assemblies identified by serial number prefix "VB". Summary: One discrepant Second Stage Planetary Transmission Gear/Bearing Assembly identifiable to "VB" serial number prefix was found. Four discrepant Second Stage Planetary Transmission Gear/Bearing Assemblies identifiable to "GG" serial number prefix were found. The discrepancies were not detected by the required inspection procedures at time of manufacture. These gears are located in the Forward and Aft Transmissions. An analytical investigation and research of historical data have led to a risk determination that Gear/Bearing Assemblies identifiable by a serial number prefix "VB" are considered serviceable with improbable risk of failure (i.e. crack propagation) if the operating limitation identified by paragraph 9 are adhered to. [Full Text] Superceded by TB 1-1520-240-20-114. See also CH-47-00-03, CH-47-99-05, CH-47-99-03, CH-47-99-02.

 

 

SOF CH-47-99-03, 23 August 1999: Title: Inspection of H-47 aircraft Forward and Aft Transmissions Gear/Bearing assemblies. Summary: Five cracked Second Stage Planetary Gears/Bearing Assemblies were found. The cracks were not detected by the required non-destructive testing procedure at time of manufacture. These Gear/Bearing Assemblies are located in the Forward and Aft Transmissions. The manufacturers of these also make the First Stage Planetary Gear/Bearing Assemblies. This message is the first in a series listing inspection requirements that must be accomplished, beginning at the Depot level. [Full Text] Superceded by TB 1-1520-240-20-113 and TB 1-1520-240-20-114. See also CH-47-00-03, CH-47-99-05, CH-47-99-04, CH-47-99-02.

 

 

SOF CH-47-99-02, 6 August 1999: Title: Immediate grounding of all H-47 series aircraft - Planetary Gear Assemblies. Summary:    A. A cracked Second Stage Planetary Gear was discovered during overhaul. The crack was created during manufacture and was not detected during inspection. The inspection of 11 additional gears revealed an additional cracked gear. A failure of the gear in flight would cause catastrophic loss of the aircraft.    B. As a prudent measure of safety, the Army is grounding its fleet of H-47 helicopters until a full records search and inspections can be conducted to determine the extent of the discrepant parts. A one time flight to return to home station is authorized at gross weight not to exceed 42,000 lbs, altitude not to exceed 3000 ft AGL, and an airspeed not to exceed 90 knots. An additional message is expected within the following week which defines un-grounding requirements. [Full Text] See also CH-47-00-03, CH-47-99-05, CH-47-99-04, CH-47-99-03 for details on the ungrounding requirements.

 

 

SOF CH-47-99-01, 30 June 1999: Title: Inspection of Sync Shaft Mounting Brackets for proper clearance to Sync Shaft. Summary: A Deficiency Report has been received on unacceptable clearance between the Sync Shaft Assembly and the mounting bracket (commonly referred to as the lord mount mounting bracket). The clearance was reported to be .010 inch. A specific manufacturer for this bracket has been identified as Davidson Fabricating Co, (FSCM 31684). The installation drawing states the proper clearance between structure and the rotating Sync Shafts is .25 inches. Inspection by the unit revealed that other brackets also exhibited clearance of less than .25 inches. [Full Text ] Superceded by TB 1-1520-240-20-111.

 

 

SOF CH-47-98-02, 16 July 1998: Title: Flight Restrictions for aircraft with MWO 1-1520-240-50-67, non-metallic spline adapters for Combining Transmission Cooling Fan Drive Shaft applied. Summary: Recently, three Chinook Combining Transmission Cooling Fan Drive Shafts have sheared. All three of these shafts were the new Combining Transmission Cooling Fan Shafts (P/N 145D5319-7) which were installed as part of MWO 1-1520-240-50-67. Failure of these shafts was contained by the "stove pipe" retaining shield, therefore eliminating any collateral damage. But since the Cooling Fan was no longer operating, the temperature of the Combining Transmission and both Engine Transmissions exceeded 140 degree Centigrade. This high temperature condition required landing of the aircraft as soon as possible without delay and replacement of all transmissions which exceeded the 140 degree Centigrade temperature limit. Currently there is an ongoing investigation as to the cause of the three fan shaft failures. [Full Text] Superceded by TB 1-1520-240-20-105.

 

 

SOF CH-47-98-01, 18 May 1998: Title: Inspection of Aft Upper Boost Actuators to Stationary Swashplate retaining hardware. Summary: Two reports have been received documenting that the wrong bolt was installed between the Aft Upper Boost Actuators and the Aft Stationary Swashplate. Both aircraft had come out of the refurbishment/standardization program at CCAD. In addition, confusion may exist when trying to identify the correct bolt due to incorporation and labeling of the Forward and Aft controls installation on the same page of the parts manual. [Full Text] Superceded by TB 1-1520-240-20-103.

 

 

SOF CH-47-97-01, 14 November 1996: Title: Visual inspection of Forward Transmission Mounting (Barrel) Nuts. Summary:    A. Safety-of-Flight Messages (see para 13a and 13b below) issued in April 1990 required the inspection/replacement of NAS577B20A Barrel Nuts to purge the supply system of nuts manufactured by Hartford Aircraft Products (HAP) Inc., Cage 66861. These nuts mount the Forward Transmission to the airframe, and four (4) nuts are required per aircraft. Analysis of several failed Barrel Nuts manufactured by this vendor indicated impurities in steel and alloy segregation. All other manufacturers NAS577B20A Barrel Nuts are acceptable.    B. A report was just received that another subject Barrel Nut manufactured by this vendor was found in the field assets. It is logical to assume that additional discrepant nuts manufactured by Hartford Aircraft Products, Inc. maybe installed on H-47 Chinook aircraft. [Full Text ] Superceded by TB 1-1520-240-20-91.

 

 

SOF CH-47-95-02, 5 May 1995: Title: Visual inspection and torque check of Lower Drive Link to Swashplate retaining hardware. Summary: A CH-47D from Fort Hood crashed. Initial results indicate the Lower Drive Link to Swashplate retaining bolt failed in fatigue. The investigation is continuing. Initial safety board findings indicate that the primary cause of the accident may have been the omission of the slip-fit bushing in the Lower Swashplate Drive Arm. It is possible that the errors and inconsistencies in the -23 maintenance manual may have contributed to the omission. [Full Text ] * Superceded by TB 1-1520-240-20-76. Aircrew Consideration: Ensure the bushing is there on Daily and Preflight.

 

 

SOF CH-47-95-01, 6 December 1994: Title: Visual inspection of Upper Boost Actuator serial numbers to ensure proper screws are installed. Summary: A 1992 accident in Alaska was caused by a screw in the Upper Boost Actuator Control Valve failing from Hydrogen Embrittlement. The failed screw restricted the travel of the pilot valve in the actuator resulting in reduced controllability of the aircraft. To correct the problem, the material and plating of the screws have been changed. Also, the bonded nylon locking feature of the screws has been changed to a hexagonal or round configuration from a longitudinal strip type. After replacing the eight (8) actuator screws IAW Boeing Letter/Message 8-1420-3-4440, the actuators were re-identified with the letter "A" (Alpha) behind the serial number on the metal decal as stated in CH-47-93-02 message. However, recently CH-47 units have been reporting that they are receiving actuators from the supply system without the letter a following the serial number. [Full Text] * Superceded by TB 1-1520-243-20-2.

 

 

SOF CH-47-94-02, 16 September 1994: Title: Rescission of Safety of Flight Message CH-47-94-01 that grounded H-47 aircraft only assigned to the 160th SOAR. Summary: A review of inspection procedures regarding the electrical connector for the fuel pump inside the HM-020-800 has revealed an error in the inspection process used. The electrical connector is not, repeat, is not faulty and the pumps will not fail. Further investigation of the Fuel Control Panel for the HM-020-800 has revealed no problem, repeat, no problem with a relay capable of causing an excess amount of voltage to the Fuel Transfer Pumps. Therefore, Safety of Flight Message CH-47-94-01 is rescinded. The Red //X// required by CH-47-94-01 may be cleared on all H-47 aircraft assigned to the 160th SOAR (ABN). [Full Text] This message is effective until rescinded or superseded.

 

 

SOF CH-47-94-01, 9 September 1994: Title: Immediate grounding of H-47 aircraft assigned only to the 160TH SOAR (Fuel Pump Relays). Summary: Inspection has revealed that the electrical connector for the fuel pump inside the HM-020-800 tank could have a faulty connector and could cause the pumps to fail. The Fuel Control Panel for the HM-020-800 fuel system for the H-47 aircraft assigned to the 160th SOAR (ABN) may have a faulty relay causing an excess amount of voltage to the intake fuel transfer pumps causing them to fail. [Full Text] Rescinded by CH-47-94-02.

 

 

SOF CH-47-93-03, 16 July 1993: Title: Records check of Engine Transmissions, P/N 145D6300-(Series), to identify unserviceable transmissions. Summary:    A. A CH-47D helicopter experienced an engine transmission failure resulting in a Class C accident while at a steady state hover. Teardown analysis of the components revealed that an Engine Transmission Spiral Bevel Gear failed from fatigue originating from a defect.    B. The second source manufacturer's grinding and inspection processes are suspect. Therefore, it is necessary to remove from service all Spiral Bevel Gears, P/N 145D6302-2, made by this manufacturer for inspection. Engine Transmissions considered unserviceable are identified by 73 Engine Transmission serial numbers. In addition, any Engine Transmission historical record having a Spiral Bevel Gear, P/N 145D6302-2, serial number with a prefix "P" (Papa), makes that Engine Transmission unserviceable. If the Spiral Bevel Gear, P/N 145D6302-2, serial number is not listed on the Engine Transmission historical record, the Engine Transmission is also considered unserviceable; unless determined serviceable by the logistical POC. [Full Text] * Superceded by TB 1-1520-240-20-66.

 

 

SOF CH-47-93-02, 30 October 1992: Title: Ungrounding of U.S. Army CH-47D, MH-47D and MH-47E aircraft (Upper Boost Acuator Screws). Summary:    A. CH-47-93-01, DTG 232230Z OCT 92 grounded all U.S. Army CH-47D, MH-47D and MH-47E aircraft due to the material failure of a screw in the Upper Boost Actuator Control Valve due to Hydrogen Embrittlement.    B. Replacement screws are made of a different material, have been silver-plated and have a nylon locking feature bonded to them and are identified by six (6) dimples on the head. Boeing teams are being sent to centralized locations to train unit maintenance personnel (AVUM) and available CH-47D Logistics Assistance Representatives (LAR) on the proper installation and inspection of the new screws. Units will be telephonically notified of training schedule. Any questions should be directed to the logistical POC. The new screws and written instructions will be provided by Boeing teams. (Additional copies of Boeing Letter/Message 8-1420-3-4440, dated 29 OCT 92 may be obtained from local LAR). Units are required to provide qualified maintenance personnel to attend training which may be conducted after normal working hours. [Full Text] * Superceded by TB 1-1520-240-20-63

 

 

SOF CH-47-93-01, 23 October 1992: Title: Immediate grounding of CH-47 and MH-47 Series aircraft (Upper Boost Acuator Screws). Summary: During the investigation of a CH-47 accident in Alaska, the probable cause was isolated to the suspected material failure of a screw in the Upper Boost Actuator Control Valve. This failure would restrict the travel of the Pilot Valve in the Upper Boost Actuator resulting in reduced controllability of the aircraft. PEO - Aviation and ATCOM are working to get a full understanding of the problem and will provide continuous updates until the problem is fully understood and a final fix is identified. [Full Text] See also CH-47-93-02 for ungrounding requirements.

 

 

SOF CH-47-91-02, 15 May 1991: Title: Update to CH-47-91-01 to identify serviceable Combiner Transmissions and Engine Transmissions. Summary:    A. Safety of Flight (SOF) Message CH-47-91-01 directed that Combiner Transmissions and Engine transmissions with specified serial numbers and gears with a "P" (Papa) prefix were unserviceable. All requirements of SOF Message CH-47-91-01 remain valid.    B. Inspection procedures have now been developed to inspect gears in these transmissions at Depot level. Gears that pass inspection will have a //DG//, //DGC// or //DGS// at the end of the gear serial number. Transmission historical record will state the installed gear serial number. All transmissions with a "M" (Mike) in front of the gear serial number are considered serviceable.    C. The transmission list in SOF Message CH-47-91-01 is now updated. Some Transmissions have been deleted because they are not in the Army inventory. Some Transmissions have been added because units have reported additional transmissions containing gears having a serial number with a prefix "P" (Papa) IAW SOF Message CH-47-91-01. [Full Text] * Superceded by a Revised TB 55-1520-240-20-55.

 

 

SOF CH-47-91-01, 2 April 1991: Title: Inspection and removal of Combiner Transmissions and Engine Transmissions containing suspect input pinions and gears. Summary:    A. Recently a CH-47D helicopter experienced a Class A accident. While in-flight at high gross weight and low altitude the crew noted a No. 2 Engine Transmission Hot Light and smoke swirling around the Engine.    B. Teardown analysis of the components revealed that the No. 2 Engine Transmission failed from fatigue originating in a grinding defect at time of manufacture. Because the second source manufacturer's grinding and inspection processes are suspect it is necessary to remove all gears received from this manufacturer from service for inspection. This manufacturer has made four different gears used in Engine and Combining Transmission. Suspect gears are in 135 Engine and Combining Transmissions of which 56 aircraft may be affected. The balance are in spares. [Full Text] Updated by CH-47-91-02. * Superceded by TB 55-1520-240-20-55.

 

 

Note: Several Safety of Flight Messages were issued prior to 1991, but we do not have a copy of them.

 

 

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