Results
2003-04-22: This amendment adopts a new airworthiness directive (AD), that is applicable to Hartzell Propeller Inc. model HD-E6C-3B/E13890K propellers with certain serial numbers of model D-1199-2 propeller control units (PCU's) installed. This amendment requires initial and repetitive inspections for below-limit propeller flight idle blade angles, and, as a terminating action, removal of the affected PCU's from service and performance of a complete Major Periodic Inspection (overhaul) when the applicable time-since-new or time-since-overhaul limit is reached, or when any flight idle blade angle is below limits. This amendment is prompted by a review by Hartzell Propeller Inc. of the model D-1199-2 PCU overhaul procedures, that revealed several dimensional checks and a nondestructive evaluation were not performed on certain serial number PCU's during a Major Periodic Inspection (overhaul). The overhaul procedures are required to comply with the Airworthiness Limitation PCU Major PeriodicInspection (overhaul) directive. The actions specified by this AD are intended to prevent below-limit flight idle propeller blade angles that, if not corrected, could result in degraded aircraft performance and control.
98-06-11: This amendment adopts a new airworthiness directive (AD), applicable to certain de Havilland Model DHC-8-100 series airplanes, that requires a one-time visual inspection to determine the presence of block seals on the upper portions of the cabin/baggage compartment bulkheads, and installation of a new or serviceable block seal for any missing block seal. This amendment is prompted by the issuance of mandatory continuing airworthiness information by a foreign civil airworthiness authority. The actions specified by this AD are intended to prevent smoke contamination of the passenger and crew cabins, in the event of fire or smoke in the baggage compartment, due to a direct smoke path between the baggage compartment and the cabins.
55-17-01: 55-17-01 LOCKHEED: Applies to All Models 49, 149, 649, 749, and 1049 Airplanes. Compliance required by December 1, 1955, unless already accomplished. A recent failure of wing flap torque tube assembly, P/N 326605-3, on a Model 1049C is attributed to a defective bolt, P/N AN 23-19. Initial overtorque of the bolt is suspected as the cause of failure of the bolt. It is therefore necessary that all Constellation and Super Constellation airplanes be inspected to ascertain proper installation of bolts, including bolt torque, on all wing flap torque tubes. Proper torque value for the AN 23-19 bolts is 10 to 20 inch-pounds. Nut torque must be checked with a torque wrench and all overtorqued bolts replaced. If necessary, the next size longer bolt (P/N AN23-20) may be used to facilitate installation within proper torque tolerances. Washers may be used as required, but not to exceed two under the head or two under the nut, to prevent the nut from bottoming on the shank.
98-07-13: This amendment adopts a new airworthiness directive (AD), applicable to certain Boeing Model 767-200 and -300 series airplanes, that requires a one-time inspection for worn or broken wire bundles in the ceiling above the main passenger door and repair, if necessary; and relocation of the wire bundles to prevent chafing. This amendment is prompted by a report indicating that the opening of the main passenger door caused the door liner and a ceiling panel to chafe and ultimately break wires installed in this area. The actions specified by this AD are intended to prevent these wires from becoming worn or breaking, which could lead to the failure of several systems, such as the fuel shutoff valves, and may contribute to the inability of the flight crew to stop the flow of fuel to the engines in the event of an engine fire.
2018-03-12: We are adopting a new airworthiness directive (AD) for certain Airbus Model A318 series airplanes; Model A319 series airplanes; Model A320-211, -212, -214, -231, -232, and -233 airplanes; and Model A321- 111, -112, -131, -211, -212, -213, -231, and -232 airplanes. This AD was prompted by reports of fatigue damage in the structure for the door stop fittings on certain fuselage frames (FR). This AD requires repetitive rototest inspections for cracking of the fastener holes in certain door stop fittings, and repair if necessary. We are issuing this AD to address the unsafe condition on these products.
55-22-02: 55-22-02 ERCO: Applies to 415-C, -CD and -D Aircraft Serial Numbers 113 Through 2468 for Fuselage Tank Replacement; Serial Numbers 113 Through 2622 For Wing Tank Replacements. Inspection required each 25 hours; replacement at time leakage discovered. Unless the terneplate fuselage fuel tank has been replaced with a stainless steel tank and the terneplate wing fuel tanks replaced with aluminum alloy or stainless steel tanks, the tanks should be inspected frequently for signs of leakage at intervals not greater than 25 hours. If tank leakage is observed, the tank should be replaced with one of stainless steel or aluminum alloy, as required, before the next flight. Erco Service Department Bulletins No. 10 and No. 10A and Memorandums No. 31 and 43 pertain to the inspection and replacement of these tanks. This supersedes AD 47-50-10.
83-07-19: 83-07-19 WYTWORNIA SPRZETU KOMUNIKACYJNEGO PZL-MIELEC: Amendment 39-4621. Applies to Model PZL M18 (Serial Numbers 1Z005-11 through 1Z005-14) airplanes certificated in any category. Compliance: Required within the next 100 hours time-in-service after effective date of this AD, unless already accomplished. To prevent loss of primary flight control about the airplane roll axis, accomplish the following: a) Replace the connecting segment of the aileron push rods with Part No. 3-26x1- 430 ZN-72/L-381-307 as prescribed in Mandatory Bulletin No. I/012/81 dated 4/81. b) Aircraft may be flown in accordance with Federal Aviation Regulation 21.197 to a location where this AD can be accomplished. c) An equivalent method of compliance with this AD, if used, must be approved by the Manager, Aircraft Certification Staff, AEU-100, Europe, Africa and Middle East Office, FAA, c/o American Embassy, 1000 Brussels, Belgium.
98-07-11: This amendment adopts a new airworthiness directive (AD) that is applicable to GKN Westland Helicopters Limited (Westland) WG-30 series 100 and 100-60 helicopters. This action requires an initial visual inspection and replacement, if necessary, of all main rotor head tie-bars. Thereafter, this AD requires, at intervals not to exceed 220 hours time-in-service (TIS), replacing each main rotor head tie-bar (tie-bar) with an airworthy tie-bar. This amendment is prompted by an accident on a similar model military helicopter in which a tie-bar failed; it is suspected that the military helicopter involved in the accident exceeded the power-off transient rotor speed limitation. This condition, if not corrected, could result in failure of a tie-bar, loss of a main rotor blade, and subsequent loss of control of the helicopter.
83-03-02 R1: 83-03-02 R1 ALLISON GAS TURBINE OPERATIONS/DETROIT DIESEL ALLISON (ALLISON): Amendment 39-4560 as amended by Amendment 39-4814. Applies to all Model 250-C20, -C20B, -C20C (T63- A720), -C20F, -B17, -B17B, -B17C, and -B17D engines equipped with the following slotted third stage turbine wheels: PART NO. TYPE OF SHROUD PART NO. TYPE OF SHROUD 6887113 Full slot 6898823 Crimped full slot 6888633 Full slot 6899364 Crimped full slot 6896863 Crimped full slot 6899406 Crimped center slot 6898551 Center slot 6899415 Crimped center slot 6898567 Center slot 6899416 Crimped center slot 6898733 Center slot 6899417 Crimped center slot 6898743 Center slot 6899418 Crimped center slot 6898753 Center slot 6899419 Crimped center slot 6898763 Center slot Accomplish the following to prevent possible engine power loss resulting from partial blade and/or shroud separation of slotted third stage turbine wheels: 1. Compliance required,as indicated, unless already accomplished: Remove from service and replace affected turbine wheels per the accomplishment instructions provided in Allison Commercial Engine Alert Bulletin CEB-A-1174/1146, Revision 3 dated January 26, 1984, or FAA approved equivalent, in accordance with the following schedule: Wheel Time Since New (TSN) - Hours Remove 1650 or more Within the next 100 hours time in service. 1000 or more and less than 1650 Within the next 400 hours time in service, or prior to exceeding 1750 hours TSN, whichever comes first. More than 500 and less than 1000 Within the next 600 hours time in service, or prior to exceeding 1500 hours TSN, whichever comes first. 500 or less Within the next 850 hours time in service, or prior to exceeding 1100 hours TSN, whichever comes first. 2. Compliance required not later than August 12, 1983, unless already accomplished: a. Placards, markings, or flight manual changes shall be provided to flight crews to avoid sustained operation of all affected engines between 90 and 98 percent N2, except during transients, while maintaining safe flight practices. This restriction also applies to autorotation practice and engine idle during engine-out simulation on multiengine aircraft. b. During all ground operation of affected turbine wheels installed in 250-C20, -C20B, C20C (T63-A720 engines, the engine N1 speed must be maintained at ground idle, except during transient operations, when performing required operational checks, or in high or gusty wind conditions, or where safety would be adversely affected. Placards, markings, or flight manual changes shall be used to advise flight crews of the ground operating restriction. c. During all ground operation of affected turbine wheels installed in 250-B17, -B17B, -B17C engines, the engine N2 speed must be maintained below 90 percent N2 r.p.m., except during transient operation, when performing required operational checks or in high or gusty wind conditions, or where safety would be adversely affected. Placards, markings, or flight manual changes shall be used to advise flight crews of the ground operating restriction. Upon request of the operator, an equivalent means of compliance with the requirements of this AD may be approved by the Manager, Chicago Aircraft Certification Office, FAA, Central Region. Special flight permits may be issued in accordance with FAR's 21.197 and 21.199 to operate aircraft to a base where compliance with this AD can be accomplished. The manufacturer's specifications and procedures identified and described in this directive are incorporated herein and made a part hereof pursuant to 5 U.S.C. 552(a)(1). All persons affected by this directive who have not already received these documents from the manufacturer may obtain copies upon request to Allison Gas Turbine Operations, General Motors Corporation, Indianapolis, Indiana 46206-0420. These documents may also be examined at the New EnglandRegional Office, 12 New England Executive Park, Burlington, Massachusetts 01803. A historical file on this AD is maintained by the FAA at the New England Regional Office. This AD supersedes Amendment 39-3011, 42 FR 43969, AD 77-18-03. Amendment 39-4560 became effective June 13, 1983. This Amendment 39-4814 becomes effective February 28, 1984.
2003-04-06: This amendment adopts a new airworthiness directive (AD) that is applicable to various aircraft equipped with a certain Honeywell Primus II RNZ-850/-851 Integrated Navigation Unit. As one alternative for compliance, this action provides for a one-time inspection to determine whether a certain modification has been installed on the Honeywell Primus II NV850 Navigation Receiver Module, which is part of the Integrated Navigation Unit. In lieu of accomplishing this inspection, and for aircraft found to have an affected navigation receiver module, this action provides for revising the aircraft flight manual to include new limitations for instrument landing system (ILS) approaches. This action is necessary to ensure that the flightcrew has an accurate glideslope deviation indication. An erroneous glideslope deviation indication could lead to the aircraft making an approach off the glideslope, which could result in impact with an obstacle or terrain. This action is intended to address the identified unsafe condition.
2003-04-07: This amendment adopts a new airworthiness directive (AD) that applies to all British Aerospace Model HP.137 Jetstream Mk.1, Jetstream Series 200, Jetstream Series 3101, and Jetstream Model 3201 airplanes. This AD requires you to repetitively inspect the horizontal and vertical stabilizer attachment fittings and associated hardware for corrosion and wear (damage). If damage is found, this AD also requires you to repair or replace the damaged parts. This AD is the result of mandatory continuing airworthiness information (MCAI) issued by the airworthiness authority for the United Kingdom. The actions specified by this AD are intended to detect and correct damage on the horizontal and vertical stabilizer attachment fittings and associated hardware, which could result in failure of the attachment fittings. Such failure could lead to flutter and subsequent structural failure of the empennage.
98-06-36: This amendment adopts a new airworthiness directive (AD) that is applicable to Eurocopter France Model SA341G and SA342J helicopters. This action requires inspecting the tail gearbox support tripod (support tripod) for cracks. This amendment is prompted by reports of cracks that were discovered during routine maintenance inspections. The actions specified in this AD are intended to detect cracks at the welds of the tail gearbox support tripod, which could cause failure of one or more of the tripod arms, subsequent separation of the tail gearbox, and loss of control of the helicopter.
2011-27-09: We are adopting a new airworthiness directive (AD) for Socata Model TBM 700 airplanes. This AD results from mandatory continuing airworthiness information (MCAI) issued by an aviation authority of another country to identify and correct an unsafe condition on an aviation product. The MCAI describes the unsafe condition as installation of the wrong (switched) aileron control cables in the wing. This unsafe condition could lead to restricted movement of the aileron, resulting in reduced control of the airplane. We are issuing this AD to require actions to address the unsafe condition on these products.
98-06-37: This amendment adopts a new airworthiness directive (AD) that applies to certain Alexander Schleicher Segelflugzeugbau (Alexander Schleicher) Model ASK-21 sailplanes. This AD requires replacing any tow release cable assembly that does not have a swivel-type end with a cable assembly that does have a swivel-type end. This AD is the result of mandatory continuing airworthiness information (MCAI) issued by the airworthiness authority for Germany. The actions specified by this AD are intended to prevent the inability to release the tow rope because of the design of the cable assembly, which could result in loss of control of the sailplane during towing operations.
2011-27-03: We are adopting a new airworthiness directive (AD) for all Model 737 airplanes. This AD was prompted by a report of extensive corrosion of a ballscrew used in the drive mechanism of the horizontal stabilizer trim actuator (HSTA). This AD requires repetitive inspections, lubrications, and repetitive overhauls of the ball nut and ballscrew and attachment (Gimbal) fittings for the trim actuator of the horizontal stabilizer; various modification(s); and corrective actions if necessary; as applicable. We are issuing this AD to prevent an undetected failure of the primary load path for the ballscrew in the drive mechanism of the HSTA and subsequent wear and failure of the secondary load path, which could lead to loss of control of the horizontal stabilizer and consequent loss of control of the airplane.
66-27-02: 66-27-02 BOEING: Amdt. 39-303 Part 39 Federal Register November 9, 1966. Applies to Model 707-300, -300B, -300C, and -400 Series Airplanes.\n \n\tCompliance required as indicated.\n \n\tTo detect cracks of the elevator nose structure in the outboard balance bay, accomplish the following:\n \n\t(a)\tWithin the next 800 hours' time in service after the effective date of this AD, unless accomplished within the last 800 hours' time in service, and thereafter at intervals not to exceed 1,600 hours' time in service from the last inspection until modified in accordance with (h), inspect elevators of Model 707-300 and -400 Series airplanes with 20,000 or more hours' time in service on the effective date of this AD, and elevators of Model 707-300B Series airplanes with 12,000 or more hours' time in service on the effective date of this AD in accordance with (f).\n \n\t(b)\tWithin the next 200 hours' time in service after the effective date of this AD, unless accomplished within the last 200 hours' time in service, and thereafter at intervals not to exceed 400 hours' time in service from the last inspection until modified in accordance with (h), inspect elevators of Model 707-300C Series airplanes with 2,000 or more hours' time in service on the effective date of this AD in accordance with (f). \n\n\t(c)\tBefore the accumulation of 20,800 hours' time in service and thereafter at intervals not to exceed 1,600 hours' time in service from the last inspection until modified in accordance with (h), inspect elevators of Model 707-300 and -400 Series airplanes with less than 20,000 hours' time in service on the effective date of this AD in accordance with (f).\n \n\t(d)\tBefore the accumulation of 12,800 hours' time in service and thereafter at intervals not to exceed 1,600 hours' time in service from the last inspection until modified in accordance with (h), inspect elevators of Model 707-300B Series airplanes with less that 12,000 hours' time in service on the effective date of this ADin accordance with (f). \n\n\t(e)\tBefore the accumulation of 2,200 hours' time in service and thereafter at intervals not to exceed 400 hours' time in service from the last inspection until modified in accordance with (h), inspect elevators of Model 707-300C Series airplanes with less than 2,000 hours' time in service on the effective date of this AD in accordance with (f).\n \n\t(f)\tVisually inspect for cracks in the leading edge of the elevators in bays No. 4 and No. 5 in accordance with paragraph 3, Part I, Boeing Service Bulletin No. 2386 (R-1), or later FAA- approved revision, except that the initial inspection of Bay No. 4 need not be accomplished until the next repetitive inspection of Bay No. 5 is required, if Bay No. 5 has been inspected in accordance with this paragraph.\n \n\t(g)\tIf cracks are found during the inspections specified in (f), before further flight, repair or replace cracked parts in accordance with the FAA-approved Structural Repair Manual or repair the elevatorin accordance with paragraph 3, Part II, Boeing Service Bulletin No. 2386(R- 1), or later FAA-approved revision or an equivalent approved by the Chief, Aircraft Engineering Division, FAA Western Region. \n\n\t(h)\tAfter the elevators have been modified in accordance with paragraph 3, Part II, Boeing Service Bulletin No. 2386(R-1) or later FAA-approved revision or an equivalent approved by the Chief, Aircraft Engineering Division, FAA Western Region, the repetitive inspections required by this AD may be discontinued.\n \n\t(i)\tUpon request of the operator, an FAA maintenance inspector, subject to prior approval of the Chief, Aircraft Engineering Division, FAA Western Region, may adjust the repetitive inspection intervals specified in this AD to permit compliance of an established inspection period of the operator, if the request contains substantiating data to justify the increase for that operator.\n \n\tThis directive effective November 9, 1966.
2011-27-06: We are adopting a new airworthiness directive (AD) for certain Dassault Aviation Model FALCON 7X airplanes equipped with certain ram air turbine (RAT) transformer rectifier units (TRUs). This AD was prompted by a report of incorrect design of the TRU part of the RAT system. This AD requires replacing any affected RAT TRU with a modified RAT TRU. We are issuing this AD to prevent loose internal wiring in the RAT generator, which could result in degraded direct current power to essential airplane systems while the RAT is deployed, which could adversely affect continued safe flight and landing of the airplane.
2010-06-12R1: We are revising an existing airworthiness directive (AD) for Thielert Aircraft Engines GmbH models TAE 125-02-99 and TAE 125-01 reciprocating engines. That AD currently requires replacing the existing rail pressure control valve with an improved rail pressure control valve. This new AD requires the same actions but relaxes the initial compliance time from within 100 flight hours to within 600 flight hours for TAE 125-01 reciprocating engines. This AD was prompted by the determination that our AD was inadvertently more restrictive than European Aviation Safety Agency AD 2008-0128. We are issuing this AD to prevent engine in-flight shutdown, possibly resulting in reduced control of the aircraft.
69-05-01 R2: 69-05-01 R2 DE HAVILLAND: Amendment 39-728 as amended by Amendment 39-1175 is further amended by Amendment 39-3824. Applies to de Havilland DHC-6 airplanes certificated in all categories: (a) Prior to next flight unless accomplished within the last 50 hours time in service, and at intervals thereafter not to exceed 100 hours time in service from the last inspection, visually inspect the control column lower sub-assembly, P/N C3CF39-17 for cracks. Replace cracked parts before further flight with a part of the same part number or with an equivalent part approved by the Chief, Engineering and Manufacturing Branch, FAA, Eastern Region. (b) The repetitive inspection interval required by (a) may be increased by the Chief, Engineering and Manufacturing Branch, FAA, Eastern Region upon receipt of substantiating data submitted through an FAA maintenance inspector. (c) Report the results of the initial inspection findings required by this AD to the Chief, Engineering and Manufacturing Branch, FAA, Eastern Region (reporting approved by the Bureau of the Budget under B.O.B. No. 04-R0174). (d) Cracked parts, P/N C3CF39-17, may be replaced with a new sub-assembly, P/N C3CF39-19, in accordance with De Havilland Modification No. 6/1433 in De Havilland Service Bulletin (S/B) No. 6/180, Revision D, dated April 30, 1976, ACCOMPLISHMENT INSTRUCTION No. 5, or with an equivalent approved by the Chief, Engineering and Manufacturing Branch, FAA, Eastern Region. (e) The repetitive inspection required by (a) may be discontinued when the lower sub-assembly is replaced by P/N C3CF39-19 in accordance with De Havilland Modification No. 6/1433, or FAA approved equivalent. Amendment 39-728 effective March 5, 1969, and was effective upon receipt for all recipients of the telegram dated January 31, 1969 which contained this amendment. Amendment 39-1175 was effective March 23, 1971. This Amendment 39-3824 becomes effective July 7, 1980.
2011-26-09: We are adopting a new airworthiness directive (AD) for all The Boeing Company Model 737-600, -700, -700C, -800, -900, and -900ER series airplanes. This AD was prompted by reports of excessive in- service wear damage of the thumbnail fairing edge seal, and of the panel rub strip and skin assembly of the fan cowl. This AD requires replacement of the thumbnail fairing edge seals on both sides of the engines with Nitronic 60 stainless steel alloy seals. We are issuing this AD to prevent failure of the fire seal, which could allow a fire in the fan compartment to spread beyond the firewall and reach the flammable fluid leakage zones, resulting in an uncontrolled fire.
2011-26-06: We are adopting a new airworthiness directive (AD) for Airbus Model A330-200 and -300 series airplanes, Model A340-200 and -300 series airplanes, and Model A340-500 and -600 series airplanes. This AD results from mandatory continuing airworthiness information (MCAI) originated by an aviation authority of another country to identify and correct an unsafe condition on an aviation product. The MCAI describes the unsafe condition as: During a pre-flight test before delivery of an aeroplane from the Airbus production line, a fault message was triggered on FDU1 [fire detection unit]. Investigations by the supplier on the faulty FDU have identified a soldering quality issue on one of the internal cards. This quality issue resulted from a specific repair process that was applied to some FDU * * * during manufacturing. The FDU monitors the engine, Auxiliary Power Unit (APU) and Main Landing Gear (MLG) bay fire detection systems. This condition, if not corrected, may adversely affect the fire detection system performance in case of a fire in the area that is monitored by the faulty FDU, potentially resulting in an unsafe condition. * * * * * We are issuing this AD to require actions to correct the unsafe condition on these products.
66-04-03: 66-04-03 SIKORSKY: Amdt. 39-194 Part 39 Federal Register February 12, 1966, as amended by Amendment 39-1563 is further amended by Amendment 39-2577. Applies to Models S-55 Series and S-62A Helicopters. Compliance required as indicated. To prevent operation with fatigue cracks in the spar of a main rotor blade, accomplish the following: (a) Except as provided in (e), remove from service S14-10-2100 series main rotor blades with 2,225 or more hours' time in service on the effective date of this AD within the next 25 hours' time in service. (b) Except as provided in (e), remove from service S14-10-2100 series main rotor blades with less than 2,225 hours' time in service on the effective date of this AD before the accumulation of 2,250 hours' time in service. (c) Except as provided in (e), remove from service S14-10-2201 series main rotor blades with 2,100 or more hours' time in service on the effective date of this AD within the next 150 hours' time in service. (d) Except as provided in (e), remove from service S14-10-2201 series main rotor blades with less than 2,100 hours' time in service on the effective date of this AD before the accumulation of 2,250 hours' time in service. (e) The service life limits specified in (a), (b), (c), and (d) may be extended to 6,000 hours' total time in service for S14-10-2201-9 main rotor blades and S14-10-2100 series and S14- 10-2201 series blades modified to S14-10-2201-9 blades, provided the blades are inspected at the times and in the manner set forth in Sikorsky Service Bulletin No. 55B10-7E dated March 26, 1976 or No. 62B10-6E dated March 26, 1976 or later FAA approved revisions, as applicable, and, if low pressure is indicated, the cause is determined and corrected before further flight in accordance with the applicable service bulletin. Amendment 39-194 became effective February 12, 1966. Amendment 39-1563 became effective November 30, 1972. This Amendment 39-2577 becomeseffective April 27, 1976.
2011-06-06 R1: We are revising an existing airworthiness directive (AD) that applies to all Eclipse Aerospace, Inc. Model EA500 airplanes equipped with Pratt & Whitney Canada, Corp. (P&WC) Model PW610F-A engines. The existing AD currently requires incorporating an operating limitation of a maximum operating altitude of 30,000 feet into Section 2, Limitations, of the airplane flight manual (AFM). Since we issued that AD, P&WC has developed a design change for the combustion chamber liner assembly. This new AD retains the requirements of the current AD, clarifies the engine applicability, and allows the option of incorporating the design change to terminate the current operating limitation and restore the original certificated maximum operating altitude of 41,000 feet. We are issuing this AD to correct the unsafe condition on these products.
2011-26-03: We are superseding an existing airworthiness directive (AD) for certain Model 777-200, -300, and -300ER series airplanes. That AD currently requires installing Teflon sleeving under the clamps of certain wire bundles routed along the fuel tank boundary structure, and cap sealing certain penetrating fasteners of the main and center fuel tanks. This AD expands the applicability in the existing AD. This AD was prompted by fuel system reviews conducted by the manufacturer, which determined that electrical arcing on the fuel tank boundary structure or inside the fuel tanks could result in a fire or explosion. We are issuing this AD to correct the unsafe condition on these products.
52-01-02: 52-01-02 BELL: Applies to All Models 47B, and 47B3 Helicopters and to Model 47D Helicopters Serial Numbers 1 to 79, Inclusive. Compliance required at next 300-hour overhaul, but not later than March 1, 1952. To increase the safety of the main rotor blade equalizer horns and drag brace fittings, which have failed in accidents involving damage to the main rotor, replace the existing equalizer horn (P/N 47-120-027-2) and drag brace fitting (P/N 47-110-145-2) with revised parts P/N 47- 120-167-1 and P/N 47-110-235-1, respectively. (Bell Service Bulletin No. 77 covers this same subject.)