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72-06-02: 72-06-02 GRUMMAN-AMERICAN AVIATION CORPORATION: Formerly American Aviation. Amendment 39-1400 as amended by Amendment 39-1467 and 39-1887 is further amended by Amendment 39-1934. Applies to American Aviation (presently Grumman- American Aviation Corporation) all Models AA-1 and AA-1A, only Models AA-1B S/N's 0001 thru 0049, and only Models AA-5 S/N's 0001 thru 0209 certified in all categories. To detect worn and broken rudder aileron and elevator control cables and pulleys control cables, accomplish the following prior to the next flight after the effective date of this A.D. unless already accomplished within the last 75 hours and thereafter at intervals not to exceed 100 hours in service from the last inspection. a. Thoroughly clean and inspect all rudder aileron and elevator control pulleys and cables where the cables pass under the pulley grouping forward of the wing center spar. Worn control cables or cables with more than four (4) internal or external broken wires orpulleys indicating wear must be replaced with an unused part of the same part number or an equivalent part prior to next flight. b. Upon submission of substantiating data by an owner or operator through an FAA Maintenance Inspector, the Chief, Engineering and Manufacturing Branch, FAA, Great Lakes Region, may adjust the repetitive inspection interval specified in this Airworthiness Directive. Equivalent parts and inspections must be approved by the Chief, Engineering and Manufacturing Branch, FAA, Great Lakes Region. Amendment 39-1400 was effective March 14, 1972, or was effective for all recipients of the airmail dispatches of February 2 and February 10, 1972 which contained this amendment. Amendment 39-1467 was effective June 27, 1972. Amendment 39-1887 became effective July 7, 1974. This Amendment 39-1934 becomes effective August 29, 1974.
2013-13-14: We are adopting a new airworthiness directive (AD) for various restricted category Model HH-1K, TH-1F, TH-1L, UH-1A, UH-1B, UH-1E, UH- 1F, UH-1H, UH-1L, and UH-1P helicopters with certain main rotor hub inboard strap fittings (fittings) installed. This AD requires a magnetic particle inspection (MPI) of the fittings for a crack, and if there is a crack, replacing the fitting with an airworthy fitting. This AD is prompted by reports of cracked fittings on Bell model helicopters and the determination that these same part-numbered fittings may be installed on various restricted category helicopters. These actions are intended to detect a crack in a fitting, which may lead to failure of a fitting, loss of a main rotor blade, and subsequent loss of helicopter control.
74-23-01: 74-23-01 GATES LEARJET: Amendment 39-2000. Applies to Model 23 (Serial Numbers 23-003, 23-005, 23-006, and 23-008 through 23-099) and Model 24 (Serial Numbers 24-100 through 24-134) airplanes. Compliance: Required within the next 10 hours' time in service after the effective date of this AD, unless already accomplished. To prevent possible shorting of the external power receptacle terminals and battery positive terminal to adjacent structure, control cables and equipment, accomplish the following: A) On Model 23 (Serial Numbers 23-003, 23-005, 23-006, 23-008 and 23-009) airplanes, check to determine if the battery quick disconnects are installed and visually inspect the external power receptacle terminals for sealing and if not installed and/or properly sealed, prior to further flight, comply with Gates Learjet Service Bulletin No. SB-23/24-258, or later approved revisions. B) On Model 23 (Serial Numbers 23-010 thru 23-099) and Model 24 (Special Numbers 24-100thru 24-134) airplanes, visually inspect the external power receptacle terminals for sealing and if not properly sealed, prior to further flight, insulate the terminals in accordance with Gates Learjet Service Bulletin SB-23/24-258 or later approved revisions. C) Any equivalent method of compliance with this AD must be approved by the Chief, Engineering and Manufacturing Branch, FAA, Central Region. This amendment becomes effective November 5, 1974.
2013-13-02: We are adopting a new airworthiness directive (AD) for all B-N Group Ltd. Models BN-2, BN-2A, BN2A MK. III, BN2A MK. III-2, BN2A MK. III-3, BN-2A-2, BN-2A-20, BN-2A-21, BN-2A-26, BN-2A-27, BN-2A-3, BN-2A- 6, BN-2A-8, BN-2A-9, BN-2B-20, BN-2B-21, BN-2B-26, BN-2B-27, BN-2T, and BN-2T-4R 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 inadequate sealing of the fuel filler cap (fuel tank cap) and the fuel filler receptacle (fuel tank opening), which could lead to contaminated fuel and result in in-flight shutdown of the engine. We are issuing this AD to require actions to address the unsafe condition on these products.
69-15-09: 69-15-09 CESSNA: Amdt. 39-797 applies to Models 310, 310A thru 310F, 320 and 320-1 Airplanes (All Serial Numbers). Compliance: Required as indicated, unless already accomplished. To prevent fuel starvation during high angle descent, accomplish the following: (A) Effective immediately, operation of the airplane with less than five (5) gallons of fuel in each main tank is prohibited. (B) Prior to further flight on all models listed above, install a permanent type placard in full view of the pilot as near as possible to the main fuel quantity indicator with the following wording: "OPERATION WITH LESS THAN FIVE (5) GALLONS OF FUEL IN EACH MAIN TANK IS PROHIBITED. USABLE FUEL IN EACH MAIN TANK IS 45 GALLONS." (C) Prior to further flight on all models listed above, install a permanent type placard in full view of the pilot as near as possible to the manifold pressure gauge with the following wording: "MAINTAIN POWER WITHIN GREEN ARCS DURING DESCENT" NOTE:The operator may make and install the above placards. Minimum 1/8 inch high letters must be used. This amendment becomes effective July 25, 1969, for all persons except those to whom it was made effective by letters dated July 9 and July 15, 1969.
70-15-09: 70-15-09 BRITISH AIRCRAFT CORPORATION: Amdt. 39-1038. Applies to Model BAC 1-11 200 and 400 series airplanes. Compliance is required as indicated. (a) Within the next 750 hours' time in service after the effective date of this AD, unless already accomplished, replace the existing 200 ampere fuse in the APU starter motor circuit with a 150 ampere fuse in accordance with British Aircraft Corporation Model BAC 1-11 Service Bulletin No. 49-PM4480 dated November 10, 1969, or later ARB-approved issue, or an FAA-approved equivalent. (b) For airplanes which have not incorporated BAC 1-11 Modification PM2518 on or before the effective date of this AD, within the next 750 hours' time in service after the effective date of this AD, unless already accomplished, modify the APU starting system as follows: (1) Incorporate a second power relay in accordance with British Aircraft Corporation Model BAC 1-11 Service Bulletin No. 49-PM2429, Revision 4, dated June 1, 1967, or later ARB-approved issue, or an FAA- approved equivalent. (2) Incorporate a separate APU start control in accordance with British Aircraft Corporation Model BAC 1-11 Service Bulletin No. 49-PM2891, Revision 5 dated December 15, 1969, or later ARB-approved issue, or an FAA-approved equivalent. (c) For airplanes which have incorporated BAC 1-11 Modification PM2518 on or before the effective date of this AD, within the next 1500 hours' time in service after the effective date of this AD unless already accomplished, modify the APU starting system in accordance with paragraphs (b)(1) and (b)(2) of this AD. (British Aircraft Corporation Model BAC 1-11 Alert Service Bulletin No. 49-A-PM4480 covers this subject.) This amendment becomes effective August 16, 1970.
2013-01-01: We are superseding an existing airworthiness directive (AD) for certain Bombardier, Inc. Model CL-600-2B19 (Regional Jet Series 100 & 440) airplanes. That AD currently requires revising the airplane flight manual, deactivating and removing certain hydraulic accumulators, inspecting for cracks on accumulators and screw caps, and replacing certain accumulators. For certain airplanes, this new AD reduces the compliance time for a certain replacement. This AD was prompted by reports of on-ground hydraulic accumulator screw cap/end cap failure. We are issuing this AD to detect and correct hydraulic accumulator screw cap/end cap failure, which could result in the loss of the associated hydraulic system and high-energy impact damage to adjacent systems and structure, and consequent loss of control of the airplane.
73-19-04: 73-19-04 BELL: Amdt. 39-1711. Applies to Model 47 series helicopters certificated in all categories that are equipped with main rotor blade grips, P/N 47-120-135-1, -2, -3 or P/N 47- 120-252-1, -3. Compliance required within the next 100 hours' time in service after the effective date of this A.D., unless already accomplished. To prevent possible fatigue cracks from developing, accomplish the following for each main rotor blade grip: (a) Inspect the grip thread relief fillet. The inboard radius and bottom of the fillet must have a smooth finish and be free of nicks or sharp tool marks (Ref. Figure 1-22 of Bell 47D- 1, 47G and 47G-2 Maintenance and Overhaul Instructions). (b) Inspect the root radius of the 4 1/2 inch diameter threads for sharp notches. The root radius must be smooth and free of sharp notches or grooves. (c) If the grip thread relief fillet is not as specified in subparagraph (a) or has nicks or sharp tool marks, or if the thread root radius has a sharp notch or groove, replace the affected grip prior to next flight, except the helicopter may be flown in accordance with FAR 21.197 to a base where the grip may be replaced. This amendment becomes effective October 10, 1973.
2013-11-09: We are superseding an existing airworthiness directive (AD) for Turbomeca S.A. Arrius 2B, 2B1, and 2F turboshaft engines. That AD currently requires replacement of injector manifolds and borescope- inspection of the flame tube and the high-pressure (HP) turbine area for possible damage. This new AD requires, depending on the engine model, repetitive replacements of fuel injection manifolds and the privilege injector, or, repetitive replacements of the privilege injector. This AD was prompted by a report that the corrective actions of the existing AD were insufficient to eliminate the unsafe condition. We are issuing this AD to prevent an uncommanded in-flight shutdown of Arrius 2B1 and 2F turboshaft engines and damage to the helicopter.
2013-10-06: We are adopting a new airworthiness directive (AD) for all Airbus Model A330-200 Freighter, A330-200, A330-300, A340-200, A340- 300, A340-500, and A340-600 series airplanes. This AD was prompted by several reports of a burning smell and/or smoke in the cockpit during cruise phase leading, in some cases, to diversion to alternate airports. This AD requires an inspection to identify the installed windshields and replacement of any affected windshield. We are issuing this AD to prevent significantly increased workload for the flightcrew, which could, under some flight phases and/or circumstances, constitute an unsafe condition.
71-24-01: 71-24-01 MCDONNELL DOUGLAS: Amdt. 39-1336 as amended by Amendment 39-1413. Applies to all DC-9 Series (except All-freighter) certified in all categories. \n\n\tCompliance required within the next 100 hours' time in service after the effective date of this AD, unless already accomplished. \n\n\tTo prevent failure of the cabin ceiling lights rotary switch and circuit, accomplish the following: \n\n\tModify the ceiling light control wiring in accordance with either Douglas Aircraft Company Alert Service Bulletin A33-55, dated October 8, 1971, or later FAA-approved revisions, or Douglas Aircraft Company Service Bulletin No. 33-56, dated February 25, 1972, or later FAA-approved revisions, or other modification approved by the Chief, Aircraft Engineering Division, FAA Western Region. \n\n\tAmendment 39-1336 was effective November 20, 1971. \n\n\tThis amendment 39-1413 is effective March 24, 1972.
2013-08-17: We are adopting a new airworthiness directive (AD) for Eurocopter France (Eurocopter) Model SA-365N, SA-365N1, AS-365N2, AS 365 N3, and SA-366G1 helicopters. This AD requires an initial and recurring inspection of the 9-degree frame for a crack, and repair of the frame if there is a crack. This AD was prompted by the discovery of a crack in the 9-degree frame of a Eurocopter Model AS-365N2 helicopter, and these cracks could develop on the other specified model helicopters because they contain the same 9-degree frame. The actions specified by this AD are intended to detect a crack in the 9-degree frame to prevent loss of structural integrity and subsequent loss of control of the helicopter.
75-18-05: 75-18-05 TAYLORCRAFT AVIATION CORPORATION: Amendment 39-2344. Applies to Model F19, all serial numbers. Before further flight, unless already accomplished: 1. Remove engine mount bolts (P/N AN6-44), spacer (P/N 530627), hose (P/N AN8848-6), bushings (P/N 53074), cup washers (P/N 530741), nut (P/N AN310-6), pin (P/N AN380-3-3), and engine mount seats (P/N 530626) on each of four (4) bolt assemblies, and inspect for damages. (Note: The AN6-44 bolt strength is suspect.) Remove any burr and sharp edges on engine mount and engine bosses. Replace bolt, spacer, and cup washers with those supplied by Taylorcraft Kit #SK75-001 dated May 15, 1975, or subsequent FAA approved parts. Replace other parts found defective with parts supplied by Taylorcraft or subsequent FAA approved parts. Taylorcraft Service Bulletin #75-002 dated March 20, 1975, or subsequent FAA approved revisions, concerns this same subject. Torque bolts to 180-190 inch-lb by tightening nut. Do not overtorque. Caution: Do not apply torque wrench on bolt head. Tightening bolt head will give incorrect value of torque due to presence of shank friction. Also turning of bolt may scratch the bolt shank, causing stress riser and premature failure. 2. Check after torquing for proper alignment of rubber (shock) bushing. 3. Between twenty-five (25) and fifty (50) hours time in service after initial accomplishment of Items 1 and 2, remove engine mount bolts, spacer, hose, bushings, cup washers, nut, pin, and engine mount seats on each of four (4) bolt assemblies and inspect for any signs of wear and deterioration. If evidence of such is found, replace with parts furnished by Taylorcraft. Reassemble using the procedures of Items 1 and 2. 4. Every one hundred (100) hours time in service after accomplishment of Item 3, repeat the actions required in Item 3. 5. A special flight permit per FAR 21.197 may be issued to allow ferrying of the aircraft to a qualified inspection and repair facility. This amendment is effective August 25, 1975, and was effective upon receipt for all recipients of the air mail letter dated May 19, 1975, which contained this amendment.
2013-08-05: We are adopting a new airworthiness directive (AD) for certain Cessna Aircraft Company (Cessna) Model 525 airplanes equipped with certain part number (P/N) air conditioning (A/C) compressor motors. This AD was prompted by reports of smoke and/or fire in the tailcone caused by brushes wearing beyond their limits on the A/C motor. This AD requires inspection of the number of hours on the A/C compressor hour meter, inspection of the logbook, replacement of the brushes on certain P/N A/C compressor motors or deactivation of the A/C system until replacement of the brushes, and reporting of airplane information related to the replacement of the brushes. We are issuing this AD to correct the unsafe condition on these products.
75-15-06: 75-15-06 GATES LEARJET: Amendment 39-2267. Applies to 23 (Serial Numbers 23- 003 thru 23-099); 24 (Serial Numbers 24-100 thru 24-297); and 25 (Serial Numbers 25-003 thru 25-182) series airplanes. Compliance: Required as indicated, unless already accomplished in accordance with Gates Learjet Service Bulletin No. SB 23/24/25-259A or later approved revisions. To check for flaws in the upper main landing gear struts, accomplish the following: A) Within the next 600 hours' time in service after the effective date of this AD, but not later than September 30, 1976, using eddy current or ultrasonic inspection equipment and procedures, inspect the left and right upper main landing gear struts for flaws in accordance with the instructions and sketches outlined in Gates Learjet Service Bulletin No. SB 23/24/25-259A or later approved revisions, or alternatively, remove the left and right upper landing gear struts from the airplane, disassemble, clean, and inspect the struts forflaws in accordance with the aforementioned Service Bulletin. B) If, as a result of the inspections referred to in Paragraph A, flaws are detected, within the next 50 hours' time in service, accomplish the following: 1. Remove any flaw in an upper main landing gear strut with a depth less than .025 inches in accordance with the procedures outlined in the aforementioned Service Bulletin. a. After flaw removal, reinspect using eddy current or ultrasonic methods to assure complete removal of the flaw and then treat and paint the affected area in accordance with the aforementioned Service Bulletin. 2. For flaws that exceed a depth of .025 inches, modify the upper main landing gear strut in accordance with instructions provided by the manufacturer or alternatively, replace with an airworthy part. C) Any equivalent method of compliance with this AD must be approved by the Chief, Engineering and Manufacturing Branch, FAA, Central Region. NOTE: Aircraft inspected and in compliance with Gates Learjet Service Bulletin SB 23/24/25-259 (i.e., the original Service Bulletin on this subject) are considered to have complied with the requirements of this AD. This amendment becomes effective July 25, 1975.
75-12-02: 75-12-02 CANADAIR: Amendment 39-2220. Applies to Canadair CL-215-1A10 airplanes certificated in all categories. Compliance required with the next twenty-five hours' time in service after the effective date of this AD unless already accomplished. To preclude the possibility of incorrect connection being made to the engine Firex bottles, accomplish the following: Modify the routing of the wire harness to the engine Firex bottles in accordance with Canadair Service Information Circular No. 66-CL-215, Revision A, dated August 13, 1974, or an equivalent modification approved by Chief, Engineering and Manufacturing Branch, FAA, Eastern Region. This amendment is effective May 30, 1975.
2013-08-07: We are adopting a new airworthiness directive (AD) for Eurocopter France (ECF) Model AS332C, L, and L1 helicopters to require an initial and repetitive inspections of the outer skin, butt strap, and fuselage frame for a crack and modification of the helicopter. This AD was prompted by an AD issued by the [[Page 23108]] European Aviation Safety Agency (EASA), which is the Technical Agent for the Member States of the European Union, which states that a crack was discovered in a fuselage frame during a daily check. The actions of this AD are intended to detect a crack, to prevent loss of airframe structural integrity and subsequent loss of control of the helicopter.
75-26-17: 75-26-17 PILATUS AIRCRAFT LTD: Amendment 39-2466. Applies to Pilatus Model PC-6/A airplanes up to and including S/N 659 (all variants) with Astazou engine installations manufactured by Pilatus Aircraft Ltd. NOTE: This AD does not apply to Pilatus Model PC-6/A airplanes manufactured by Fairchild Hiller. Compliance required within the next 100 hours' time in service after the effective date of this AD, unless already accomplished. To prevent failure of the engine mount to fuselage attachment, reinforce the U-channel, P/N 6201.992, by installing a steel plate, P/N 112.35.06.337, to each U-channel lug and rework the engine strut heads, P/N 6501.106, in accordance with paragraph 2.2 of Pilatus Aircraft Ltd. Service Bulletin No. 83A dated February 1971, or an FAA-approved equivalent. This amendment becomes effective on January 17, 1976.
75-27-04: 75-27-04 SOCIETE NATIONALE INDUSTRIELLE AEROSPATIALE: Amendment 39- 2476. Applies to Model SA-341G "Gazelle" helicopters, certificated in all categories, serial numbers 1062 and lower, incorporating standard fuel tank P/N 341A.55.1065.1065.20, or .22, or .24. Compliance is required within the next 100 hours' time in service after the effective date of this AD, unless already accomplished in accordance with Gazelle Service Bulletin No. 28.01. To prevent interruption of fuel flow to the engine during execution of approved flight maneuvers, modify the fuel system to provide for increased fuel sump capacity and an improved booster pump location in accordance with subparagraph 2(B) of Gazelle Service Bulletin No. 28.01, as revised November 21, 1973, or an FAA-approved equivalent. This amendment becomes effective on January 19, 1976.
2013-07-07: 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 an incorrect procedure used to apply the wear and corrosion protective surface coating to attach pins of the horizontal stabilizer rear spar. This AD requires inspecting to determine the part number of the attach pins of the horizontal stabilizer rear spar, and replacing certain attach pins with new, improved attach pins. We are issuing this AD to prevent premature failure of the attach pins, which could cause reduced structural integrity of the horizontal stabilizer to fuselage attachment, resulting in loss of control of the airplane.
74-20-04: 74-20-04 HUGHES HELICOPTERS: Amendment 39-1968. Applies to Hughes Model 369, 369A, 369H, 369HE, 369HS and 369HM helicopters certificated in all categories. Compliance required within the next 25 hours' of helicopter operation after the effective date of this AD, unless already accomplished within the last 75 hours' of helicopter operation, and thereafter at intervals not to exceed 100 hours' of helicopter operation from the last inspection. To detect cracks, gouges, nicks and scratches in the main rotor blade trailing edge, accomplish the following: (a) Inspect the main rotor blade trailing edge in accordance with Hughes Service Information Notice. No. HN-73, dated August 19, 1974, or later FAA-approved revisions. (1) If cracks are found remove blade from service prior to further flight. (2) If gouges, nicks and/or scratches are found replace or repair blade prior to further flight in accordance with Hughes Service Information Notice, No. HN-73. (b)Equivalent inspection and repair procedures may be approved by the Chief, Aircraft Engineering Division, FAA Western Region upon submittal of adequate substantiating data. (c) Aircraft may be flown to a base for performance of the inspections required by this AD per FAR's 21.197 and 21.199. This amendment becomes effective September 25, 1974.
2013-07-05: We are adopting a new airworthiness directive (AD) for Eurocopter France EC130B4 helicopters. This AD requires visually checking the center windscreen panel (center windscreen) for a crack and replacing the center windscreen if there is a crack, if the windscreen distorts during flight, or within 12 months. This AD was prompted by in-flight cracking and failure of a center windscreen. The actions of this AD are intended to detect a crack in the blending radii of the center windscreen to prevent failure of the windscreen, injury to the flight crew, and subsequent loss of control of the helicopter.
72-16-08: 72-16-08 SOCIETE NATIONALE INDUSTRIELLE AEROSPATIALE: (S.N.I.A.S.) formerly Sud Aviation): Amendment 39-1490. Applies to Alouette Astazou SA3180, SA318B, and SA318C helicopters which have not been modified in accordance with Aerospatiale Service Bulletin No. 65.82 dated October 25, 1971, or an FAA-approved equivalent. Compliance required as indicated. To prevent possible cracks or failures of the half sleeves fitted on the flexirac unions on the main gear box to cooler oil line, accomplish the following in accordance with Aerospatiale Service Bulletin No. 05.39, amended November 10, 1971, or an FAA-approved equivalent. (a) For helicopters fitted with half sleeves, P/N L.16.06, on-flexirac union assemblies, P/N L.16.03, before further flight unless already accomplished within the last 100 hours' time in service, and thereafter at intervals not to exceed 100 hours' time in service on the half sleeves, replace the half sleeves, P/N L.16.06, by replacing the assembly, P/N L.16.03, with a new assembly of the same part number. (b) For helicopters fitted with half sleeves, P/N LS.16.06, on flexirac union assemblies, P/N LS.16.03, before further flight unless already accomplished within the last 800 hours' time in service, and thereafter at intervals not to exceed 800 hours' time in service on the half sleeves, replace the half sleeves, P/N LS.16.06, by replacing the assembly, P/N LS.16.03, with a new assembly of the same part number. (c) Replacement of the half sleeves in accordance with paragraphs (a) and (b) may be discontinued when the flexirac union on the main gear box oil pump is reinforced in accordance with Aerospatiale Service Bulletin No. 65.82 dated October 25, 1971, or an FAA- approved equivalent. This amendment is effective upon publication in the Federal Register as to all persons except those persons to whom it was made immediately effective upon receipt of the telegram dated June 15, 1972, which contained this amendment.
2013-05-14: We are adopting a new airworthiness directive (AD) for Bell Helicopter Textron, Inc. (Bell), Model 412 and 412EP helicopters. This AD requires establishing a lower life limit on certain swashplate outer ring assemblies (outer ring), revising the retirement life on the components' history card or equivalent record, and revising the maintenance manual or Instructions for Continued Airworthiness (ICA). This AD also prohibits installing these outer rings on any helicopter. This AD was prompted by reports of cracking in the outer rings. The actions are intended to prevent failure of an outer ring because of cracking, which could lead to the loss of main rotor (M/R) blade pitch control and subsequent loss of helicopter control.
70-08-03: 70-08-03 SIKORSKY: Amdt. 39-974. Applies to Sikorsky type S-61A/L/N/R helicopters certificated in all categories. Accomplish the following within the next 10 heater hours in service, unless already accomplished, and every 15 heater hours in service thereafter: A. Remove and inspect combustion air inlet duct backfire check valve Bobrick Co. P/N 9660-1-1 or 40064-32 for distortion, missing flappers, or other obvious damage. B. Replace defective valves before further operation of the heater with a part inspected in accordance with paragraph A above. Upon replacement inspect all heater inlet air ducting for evidence of fuel contamination. Any fuel contamination must be eliminated before further heater operation. C. Upon submission of substantiating data through an FAA maintenance inspector, the Chief, Engineering and Manufacturing Branch, FAA Eastern Region may adjust the repetitive inspection intervals specified in this AD to permit compliance at an established inspection period of the operator. D. For the purpose of this AD, compliance time may be based on helicopter hours in service if the owner or operator cannot document heater operating time. This amendment is effective April 23, 1970, and was effective March 17, 1970 for all recipients of the telegram dated March 17, 1970 which contained this amendment.