Results
93-24-16: 93-24-16 PURITAN BENNETT AERO SYSTEMS: Amendment 39-8765; Docket No. 93-CE-36-AD. Applicability: Crewmember Protective Breathing Equipment (PBE), 119003 and 119003-01 Units, that are installed on, but not limited to the following airplanes (all serial numbers), certificated in any category: \n\n\nManufacturer\nModels \nAirbus Industries\nA300, A310, and A320 \nBoeing\n727, 737, 747, 757, and 767 \nMcDonnell Douglas\nDC8, DC9, DC10, MD11, MD80, MD81, MD82, and MD83 \nde Havilland\nDHC-8 \nBritish Aerospace\nBAe 146 and BAe 31 \nLockheed\nL1011 \nFokker\n100 \nSAAB\nSF340 \nAerospatiale\nATR42 and ATR72 \nCanadair\nRJ \nShorts\n360\n\n\tCompliance: Required within the next 24 calendar months after the effective date of this AD, unless already accomplished. \n\n\tTo prevent failure of a PBE unit because of a deteriorated neck seal, accomplish the following: \n\n\t(a)\tInspect the affected PBE unit for existence of a yellow label attached to the red rip tag. Remove from service any unitthat does not have this yellow label. \n\n\tNOTE 1: Figure 1 of Puritan Bennett Aero Systems SB No. 119003-35-1, dated February 15, 1993, illustrates the location of this yellow label. \n\n\tNOTE 2: PBE units not having a yellow tag may be shipped to the manufacturer at the address specified in paragraph (d) of this AD. The unit will then be modified and shipped back with a yellow tag attached to the red rip tag. \n\n\t(b)\tSpecial flight permits may be issued in accordance with FAR 21.197 and 21.199 to operate the airplane to a location where the requirements of this AD can be accomplished. \n\n\t(c)\tAn alternative method of compliance or adjustment of the compliance time that provides an equivalent level of safety may be approved by the Manager, Wichita Aircraft Certification Office, FAA, 1801 Airport Road, Room 100, Wichita, Kansas 67209. The request shall be forwarded through an appropriate FAA Maintenance Inspector, who may add comments and send it to the Manager, Wichita Aircraft Certification Office. \n\n\tNOTE 3: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Wichita Aircraft Certification Office. \n\n\t(d)\tAll persons affected by this directive may obtain copies of the document referred to herein upon request to Puritan Bennett Aero Systems Company, Attention: Customer Service Department, 10800 Pflumm Road, Lenexa, Kansas 66215; or may examine this document at the FAA, Central Region, Office of the Assistant Chief Counsel, Room 1558, 601 E. 12th Street, Kansas City, Missouri 64106. \n\n\t(e)\tThis amendment (39-8765) becomes effective on February 4, 1994.
2005-11-13: The FAA is adopting a new airworthiness directive (AD) for certain BAE Systems (Operations) Limited Model BAe 146 airplanes. This AD requires repetitive inspections for cracks of the fuselage pressure skin above the left and right main landing gear (MLG) bay. This AD also requires corrective action, including related investigative actions, if leaks are found. This AD is prompted by reports of cracks in the fuselage pressure skin above the left and right MLG bay. We are issuing this AD to detect and correct fatigue cracking in the fuselage pressure skin above the left and right MLG bay; such fatigue cracking could adversely affect the structural integrity of the fuselage and its ability to maintain pressure differential.
62-16-04: 62-16-04 PIAGGIO: Amdt. 463 Part 507 Federal Register July 13, 1962. Applies to Model P.166 Aircraft, Serial Numbers 341 to 403 Inclusive. Compliance required as indicated. In order to preclude failure of the frame 20 angle bar at the attachment of the elevator control sector bracket, accomplish the following: (a) Within the next 10 hours' time in service after the effective date of this AD and thereafter within each 20 hours' time in service, inspect the frame 20 angle bar for cracks in the area of the elevator control sector bracket attachment. (b) If cracks are found, repair in accordance with the procedures specified under Second Assumption in Piaggio Service Bulletin 166-16, or FAA approved equivalent prior to further flight. When this has been accomplished the inspections required in (a) may be discontinued. (c) The inspections required in (a) may be discontinued after incorporating the reinforcement specified under First Assumption in Piaggio Service Bulletin 106-16 or FAA approved equivalent. This directive effective July 20, 1962.
2008-24-07: The FAA is adopting a new airworthiness directive (AD) for certain Eclipse Aviation Corporation (Eclipse) Model EA500 airplanes equipped with a Pratt and Whitney Canada, Corp. (PWC) PW610F-A engine. This AD requires you to incorporate operating limitations into Section 2, Limitations, of the airplane flight manual (AFM). This AD results from several incidents of engine surge. We are issuing this AD to prevent hard carbon buildup on the static vane, which could result in engine surges. Engine surges may result in a necessary reduction in thrust and decreased power for the affected engine. In some cases, this could result in flight and landing under single-engine conditions.
80-01-04: 80-01-04 TELEDYNE CONTINENTAL MOTORS: Amendment 39-3647. Applies to Continental IO-520 and TSIO-520 series engines incorporating cylinder assemblies which have been rebarrelled by Airmotive Engineering Corporation. Compliance is required within the next 50 hours time in service after the effective date of this AD, unless already accomplished, except aircraft may be flown in accordance with FAR 21.197 to a base where the maintenance required by this AD may be performed. To prevent failure of cylinder holddown flanges, accomplish the following: Inspect to determine if Airmotive Engineering Corporation rebarreled cylinders, Part Numbers AE-C- 631397 T.T., AE-C-639272 T.T., and AE-C-639274 T.T., are installed. If installed, inspect cylinders for .050 inch minimum corner radius in the area spot faced for installation of holddown nuts. Airmotive Engineering Corporation Service Alert dated September 28, 1979, covers this also. Replace all cylinders found without the proper radius. The cylinder part numbers are marked on the flat area of the cylinder holddown flanges on the intake valve side. These cylinder assemblies may have been installed during overhaul or unscheduled maintenance. Airmotive Engineering Corporation Service Alert dated September 28, 1979, pertains to and provides instructions for accomplishing the intent of this AD. The manufacturer's 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 Airmotive Engineering Corporation, 9131 Directors Row, Dallas, Texas 75247. These documents may also be examined at Office of the Regional Counsel, Southwest Region, Federal Aviation Administration, 4400 Blue Mound Road, Fort Worth, Texas. Equivalent means of compliance with the modification prescribed by this AD may be approved by the Chief, Engineering and Manufacturing Branch, Flight Standards Division, Southwest Region, Federal Aviation Administration, Post Office Box 1689, Fort Worth, Texas 76101. This amendment becomes effective January 25, 1980.
98-13-16: This amendment adopts a new airworthiness directive (AD), applicable to certain EMBRAER Model EMB-145 series airplanes, that requires replacement of the horizontal stabilizer anti-icing valve with a new anti-icing valve. This amendment also requires reinforcement of the insulation over the anti-icing ducts of the horizontal stabilizer thermal anti-icing system. This amendment is prompted by issuance of mandatory continuing airworthiness information by a foreign civil airworthiness authority. The actions specified by this AD are intended to prevent failure of the horizontal stabilizer anti-icing valve, which could cause the horizontal stabilizer thermal anti-icing system to be inoperative, and could result in reduced controllability of the airplane.
2005-09-51: This document publishes in the Federal Register an amendment adopting emergency airworthiness directive (AD) 2005-09-51 that we sent previously to all known U.S. owners and operators of certain Turbomeca Arrius 2F turboshaft engines. This AD requires before further flight, replacing the Module 2 on certain engines listed by serial number (SN) in this AD. This AD results from a report of the failure of a high pressure turbine (HPT) blade and damage to two other HPT blades in a Turbomeca Arrius 2F turboshaft engine. We are issuing this AD to prevent failure of the engine and subsequent loss of power.
60-07-08: 60-07-08 WRIGHT: Amdt. 121 Part 507 Federal Register March 29, 1960. Applies to All R-1820-103 Engines Installed In Helicopters. Compliance required at first engine overhaul after June 1, 1960, but not later than December 31, 1960. To alleviate failures of the master rod assemblies, strengthened master and articulating rods with associated parts must be installed in accordance with the instructions contained in Wright Aeronautical Division Service Bulletin No. C9-353.
2005-10-14: This amendment supersedes an existing airworthiness directive (AD) for the specified Eurocopter France (ECF) model helicopters. That AD currently requires replacing certain main or combiner gearboxes with airworthy gearboxes. Further investigation has shown that the main gearbox is not affected, and this amendment requires replacing a certain combiner gearbox with a modified airworthy gearbox. This amendment is prompted by a report of a freewheel unit slipping resulting in an engine overspeed and shutdown. Also, this amendment is prompted by the conclusion of the investigation, which finds the freewheel slippage is due to the surface treatment applied to certain freewheel rollers in the combiner gearbox. The actions specified by this AD are intended to prevent an engine overspeed, an engine shutdown, and subsequent loss of control of the helicopter.
2005-10-07: The FAA is adopting a new airworthiness directive (AD) for all Fokker Model F.28 series airplanes. This AD requires a one-time inspection of the area underneath the auxiliary power unit (APU) enclosure to determine if drain tubes in the area are correctly installed and to detect damaged wiring, and corrective action if necessary. This AD is prompted by a report of a fire under the APU enclosure. We are issuing this AD to prevent fuel from accumulating under the APU enclosure, which, in the presence of an ignition source, could result in a fire.
2009-16-07: The FAA is superseding an existing airworthiness directive (AD), which applies to certain Boeing Model 737-600, -700, -700C, -800, and -900 series airplanes. That AD currently requires replacing brackets that hold the P5 panel to the airplane structure, the standby compass bracket assembly, the generator drive and standby power module, and the air conditioning module, as applicable. The existing AD also currently requires, among other actions, inspecting for wire length and for damage of the connectors and the wire bundles, and doing applicable corrective actions if necessary. This new AD requires an additional operational test of the P5-14 panel. This AD results from a report of an electrical burning smell in the flight compartment. We are issuing this AD to prevent wire bundles from contacting the overhead dripshield panel and modules in the P5 overhead panel, which could result in electrical arcing and shorting of the electrical connector and consequent loss of several critical systems essential for safe flight; and to ensure proper operation of the passenger oxygen system. If an improperly functioning passenger oxygen system goes undetected, the passenger oxygen mask could fail to deploy and result in possible incapacitation of passengers during a depressurization event. \n\n\nDATES: This AD becomes effective September 22, 2009. \n\tThe Director of the Federal Register approved the incorporation by reference of a certain publication listed in the AD as of September 22, 2009. \n\tOn June 22, 2006 (71 FR 28766, May 18, 2006), the Director of the Federal Register approved the incorporation by reference of certain other publications listed in the AD.
95-10-14: This amendment adopts a new airworthiness directive (AD), applicable to all Airbus Model A300, A310, and A300-600 series airplanes, that requires repetitive mechanical and electrical inspections to detect chafing of electrical wiring; and repair or replacement of discrepant parts, and repositioning the looms. This amendment is prompted by reports of wire chafing in the forward avionic compartment. The actions specified by this AD are intended to prevent such chafing, which may lead to a short in the electrical circuits at the 104VU panel; this condition could result in unwanted depressurization, loss of wing de-icing, and loss of in-flight engine restart capability.
2005-09-07: This amendment adopts a new airworthiness directive (AD) for Agusta S.p.A. (Agusta) Model A109E helicopters that requires visually inspecting each main transmission support fitting (fitting) attachment bolt (bolt) for a fracture, a crack, or looseness, and verifying the torque on each fitting bolt. This amendment is prompted by two incidents of fatigue failure of the bolts that secure the transmission rear support fittings to the helicopter. The actions specified by this AD are intended to detect a fracture, a crack, or looseness of a fitting bolt, and prevent fatigue failure of a fitting bolt and subsequent loss of control of the helicopter.
2005-09-06: This amendment adopts a new airworthiness directive (AD) for Agusta S.p.A. (Agusta) Model A119 helicopters that requires visually inspecting each main transmission support fitting (fitting) attachment bolt (bolt) for a fracture, a crack, or looseness, and verifying the torque on each fitting bolt. This amendment is prompted by two incidents of fatigue failure of the bolts that secure the transmission rear support fittings to the helicopter. The actions specified by this AD are intended to detect a fracture, a crack, or looseness of a fitting bolt, and prevent fatigue failure of a fitting bolt and subsequent loss of control of the helicopter.
98-06-08: This amendment adopts a new airworthiness directive (AD), applicable to certain Airbus Model A300, A310, and A300-600 series airplanes, that requires inspections to detect defects of the flanges of the bleed air ducts of the auxiliary power unit (APU), and to measure the material thickness of the flanges; and repair, replacement of the duct with a new or serviceable duct, or operation of the airplane with the bleed air system of the APU inoperative, if necessary. For certain airplanes, the amendment also requires an inspection to detect cracks of the flanges, and follow-on actions. This amendment is prompted by issuance of mandatory continued airworthiness information by a foreign civil airworthiness authority. The actions specified by this AD are intended to prevent rupturing and cracking of the flanges of the bleed air ducts, which could damage the elevator control system and consequently reduce the controllability of the airplane.
86-21-05: 86-21-05 BRITISH AEROSPACE: Amendment 39-5418. Applies to BAe Models DH/HS/BH 125 series airplanes equipped with Garrett TFE 731-3R-1H engines, certificated in any category. Compliance is required within 60 days after the effective date of this AD. To prevent failure of the forward engine mounts, accomplish the following, unless previously accomplished: A. Inspect the forward engine mounts and repair, if necessary, in accordance with BAe Service Bulletin 71-38, Revision 1, dated October 4, 1985. B. An alternate means of compliance or adjustment of the compliance time, which provides an acceptable level of safety, may be used when approved by the Manager, Standardization Branch, ANM-113, FAA, Northwest Mountain Region. C. Special flight permits may be issued in accordance with FAR 21.197 and 21.199 to operate airplanes to a base for the accomplishment of the inspections and/or modifications required by this AD. All persons affected by this directive, who have notalready received the appropriate service document from the manufacturer may obtain copies upon request to British Aerospace, Inc., Librarian, Box 17414, Dulles International Airport, Washington, D.C. 20041. This document may be examined at FAA, Northwest Mountain Region, 17900 Pacific Highway South, Seattle, Washington, or the Seattle Aircraft Certification Office, 9010 East Marginal Way South, Seattle, Washington. This Amendment becomes effective October 20, 1986.
93-18-01: 93-18-01 JETSTREAM AIRCRAFT LIMITED: Amendment 39-8701. Docket 93-NM-155-AD. Applicability: All Model 4101 series airplanes, certificated in any category. Compliance: Required as indicated, unless accomplished previously. To prevent the migration of the aileron trim tab hinge pins out of the hinge, which could impede the movement of the aileron control system and cause reduced controllability of the airplane, accomplish the following: (a) Within 25 hours time-in-service after the effective date of this AD, conduct a visual inspection of the inboard and outboard ends of the hinge pin (wire) of the trim tab on the aileron to determine if the pin has moved or can be moved out of the hinge, in accordance with "Part 1 - Initial Inspection Left and Right," of the Accomplishment Instructions of Jetstream Alert Service Bulletin J41-A27-020, dated August 13, 1993. (b) If the pin has moved, or if the pin moves out of the hinge when the end of the wire is tapped, prior to further flight, accomplish the corrective procedures specified in "Part 3, Rectification, Left and Right," of the Accomplishment Instructions of Jetstream Alert Service Bulletin J41-A27-020, dated August 13, 1993. After accomplishment of this corrective action, no further action is required by this AD. (c) If the pin is correctly positioned, within 50 hours time-in- service, conduct a visual inspection of the inboard and outboard ends of the hinge pin (wire) of the trim tab on the aileron to assure reliability, in accordance with "Part 2 - Repeat Inspection Left and Right," of the Accomplishment Instructions of Jetstream Alert Service Bulletin J41-A27-020, dated August 13, 1993. (1) If the pin is correctly positioned, no further action is required by this AD. (2) If the pin has moved, or if the pin moves out of the hinge when the end of the wire is tapped, prior to further flight, accomplish the corrective procedures specified in "Part 3 - Rectification, Leftand Right," of the Accomplishment Instructions of the service bulletin. After accomplishment of this corrective action, no further action is required by this AD. (d) An alternative method of compliance or adjustment of the compliance time that provides an acceptable level of safety may be used if approved by the Manager, Standardization Branch, ANM-113, FAA, Transport Airplane Directorate. Operators shall submit their requests through an appropriate FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, Standardization Branch, ANM-113. NOTE: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Standardization Branch, ANM-113. (e) Special flight permits may be issued in accordance with FAR 21.197 and 21.199 to operate the airplane to a location where the requirements of this AD can be accomplished. (f) The inspections and corrective procedures shall be done in accordance with Jetstream Alert Service Bulletin J41-A27-020, dated August 13, 1993. This incorporation by reference was approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR Part 51. Copies may be obtained from Jetstream Aircraft, Inc., P.O. Box 16029, Dulles International Airport, Washington, DC 20041-6029. Copies may be inspected at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC. (g) This amendment becomes effective on November 9, 1993, to all persons except those persons to whom it was made immediately effective by priority letter AD 93-18-01, issued on September 7, 1993, which contained the requirements of this amendment.
94-20-12: This amendment adopts a new airworthiness directive (AD), applicable to certain IAI Model 1125 Westwind Astra airplanes, that requires relocation of the ground cable in the slat power drive unit. This amendment is prompted by a report that the drive system for the leading edge slat stopped in transit during flight on a Model 1125 Westwind Astra airplane. This incident was caused by an improper ground connection for the electric motor of the slat drive system, which resulted in arcing and an open electrical circuit. The actions specified by this AD are intended to prevent possible fuel vapor fire due to electrical arcing in an area where fuel vapors might be present and the inability to move the slats during flight due to an open electrical circuit.
80-08-12: 80-08-12 PRATT & WHITNEY AIRCRAFT OF CANADA, LIMITED: Amendment 39-3748. Applies to Pratt & Whitney Aircraft of Canada, Limited PT6A-6, -6A, -6B, -6/C20, -11, -15AG, -20, -20A, -20B, -21, -25, -25A, -27, -28, -34, -34B, -34AG, -36, -41, -45A, -45B, -112, -135 turboprop engines and Pratt & Whitney Aircraft PT6A-20A, -25, -27, -28, -34 turboprop engines incorporating Part Number 02-14910-01 fuel pump coupling. Compliance required as indicated unless previously accomplished. To preclude wear of the fuel pump drive coupling splines which results in an engine flameout condition, accomplish the following: a. Within the next 50 hours in service after the effective date of this AD for engines which have had a fuel pump removed within the last 200 hours in service, inspect 02-14910-01 fuel pump drive coupling for wear or damage. If the fuel pump drive coupling is worn or damaged replace the fuel pump drive coupling with a new coupling with the same part number or 5006050 coupling assembly in accordance with Paragraph 2, Accomplishment Instructions, in Pratt & Whitney Aircraft of Canada, Limited Service Bulletin Nos. 1316, 3139 or 12025 as applicable or an approved equivalent inspection and parts. If 02-14910-01 coupling is installed repeat above inspection each 200 hours in service thereafter until Paragraph b is accomplished. b. For all engines, prior to July 1, 1981, replace 02-14910-01 fuel pump drive coupling with 5006050 coupling assembly in accordance with Paragraph 2, Accomplishment Instructions in Pratt & Whitney Aircraft of Canada, Limited Service Bulletin Nos. 1316, 3139 or 12025 as applicable or approved equivalent inspection and parts. When 5006050 coupling assembly is installed, the inspection requirements of this AD no longer apply. Aircraft may be flown to a base for performance of maintenance required by this AD per FAR 21.197 or FAR 21.199. All equivalent inspections and parts must be approved by the Chief, Engineering & Manufacturing Branch, of the Eastern Region of the FAA. (Pratt & Whitney Aircraft of Canada, Limited Service Bulletin Nos. 1316, 3139 or 12025 pertain to this subject.) This amendment is effective April 18, 1980.
2005-08-11: This amendment adopts a new airworthiness directive (AD), applicable to certain Saab Model SAAB SF340A and SAAB 340B series airplanes, that requires replacement of certain hydraulic hoses with new hydraulic hoses. This action is necessary to prevent cracking and/ or rupture and subsequent failure of hydraulic hoses. Such failure could result in loss of hydraulic pressure and fluid quantity, and consequent reduced controllability of the airplane. This action is intended to address the identified unsafe condition.
2008-16-09 R1: We are revising an existing airworthiness directive (AD) for the products listed above. 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: There have been several occurrences of cracked elevator trim tab balance weight attachment brackets, on one occasion, the elevator trim tab mass balance weight bracket separated from the aircraft. The loss of an elevator trim tab mass balance weight bracket has the potential to cause damage to an aircraft, or cause serious injury to personnel. * * * * * We are issuing this AD to require actions to correct the unsafe condition on these products. DATES: This AD becomes effective September 16, 2009. The Director of the Federal Register previously approved the incorporation by reference of certain publications listed in this AD as of September 15, 2008 (73 FR 46543, August 11, 2008). The Director of the Federal Register previously approved the incorporation by reference of a certain publication listed in this AD as of March 14, 2005 (70 FR 9212, February 25, 2005). The Director of the Federal Register previously approved the incorporation by reference of a certain other publication listed in this AD as of September August 3, 2004 (69 FR 38813, June 29, 2004).
51-10-02: 51-10-02 LUSCOMBE: Applies to All Model 8 Series Aircraft. Compliance required by the next periodic inspection, but not later than June 1, 1951, and at each annual recertification thereafter. Due to recurring failures of the control cables, all cables should be carefully inspected at each section which passes either over a pulley or through a fairlead. To properly inspect the cables, they should be removed from the airplane to the extent necessary to expose the sections to be inspected. Care should be taken that the method of inspection is not damaging to the cable; i.e., do not sharply bend any strand or the whole cable and do not "bird-cage" the cable to the extent of putting permanent set in the strands or the whole cable. Any unairworthy cables must be replaced. In reinstalling the control cables, the rigging of the entire control system should be checked and properly adjusted. The control surface travels may be obtained from Aircraft Specification A-694. Care should be taken that none of the cables drag across or rub against any structure or equipment due to misalignment of the fairleads. Luscombe Airplane Corp. Service Bulletin No. 1-51 furnishes further information on this subject and Luscombe Airplane Corp., Garland, Texas, should be contacted for further information, if needed, in rigging controls.
2021-19-11: The FAA is adopting a new airworthiness directive (AD) for certain De Havilland Aircraft of Canada Limited Model DHC-8-102, -103, and -106 airplanes; Model DHC-8-201 and -202 airplanes; Model DHC-8- 301, -311, and -315 airplanes; and Model DHC-8-400, -401, and -402 airplanes. This AD was prompted by reports that mounting nuts attaching the rudder actuator bracket to the vertical stabilizer have been found cracked or missing due to hydrogen embrittlement. This AD requires a one-time inspection of the rudder actuator bracket mounting nuts, and corrective actions if necessary. The FAA is issuing this AD to address the unsafe condition on these products.
2021-20-07: The FAA is adopting a new airworthiness directive (AD) for certain Airbus Canada Limited Partnership Model BD-500-1A10 and BD-500- 1A11 airplanes. This AD was prompted by a report that following an in- service engine shutdown during taxi, water was found to be dripping into the forward avionics bay; the water caused a short circuit and tripped a circuit breaker. This AD requires replacing the forward galley slotted drain covers with solid blanking plates and modifying the associated drain tubing to block water. The FAA is issuing this AD to address the unsafe condition on these products.
2009-17-01: We are adopting a new airworthiness directive (AD) for certain Gulfstream Model G-IV, GIV-X, GV-SP series airplanes and Model GV airplanes. This AD requires, for certain airplanes, a one-time inspection for sealant applied to the exterior of the auxiliary power unit (APU) enclosure (firewall), and, for airplanes with the subject sealant and certain other airplanes, a revision of the airplane flight manual to prohibit operation of the APU during certain ground and flight operations. This AD results from notification from the airplane manufacturer that an improper, flammable sealant was used on the interior and exterior of the APU enclosure (firewall). We are issuing this AD to prevent this flammable sealant from igniting the exterior surfaces of the APU enclosure (firewall) under certain anomalous conditions such as an APU failure/APU compartment fire, which could result in propagation of an uncontained fire to other critical areas of the airplane.