30 Airworthiness Directives: 23 airplane, 2 rotorcraft, 3 engine, 1 appliance, 1 glider.
AD 97-14-01 · published Jul 2, 1997, effective Aug 18, 1997
Pilatus Britten-Norman Ltd. BN-2A and BN-2A Mk 111 Series Airplanes
This amendment supersedes Airworthiness Directive (AD) 75-24- 07 R1, which currently requires repetitively inspecting the left-hand (LH) rudder bar assembly for cracks and loose fasteners on certain Pilatus Britten-Norman Ltd. BN-2A and BN-2A Mk 111 series airplanes, and replacing any cracked part. The superseding action requires inspecting the LH rudder bar assembly and determining the wall thickness of the slider tube unit. This action also would require modifying the rudder bar assembly by replacing the LH slider tube with a new strengthened slider tube unit as terminating action for the repetitive inspections currently required by AD 75-24-07 R1. The development of a modification to the rudder bar assembly, which terminates the repetitive inspections required by AD 75-24-07 R1, prompted this AD. The actions specified by this AD are intended to prevent failure of the pilot's rudder bar assembly, which could result in loss of control of the airplane during landing operations.
AD 97-13-02 · published Jul 3, 1997, effective Jul 14, 1997
Diamond Aircraft Industries, Inc. Model DA 20-A1 Airplanes, Serial Numbers 10002 Through 10287
This document publishes in the Federal Register an amendment adopting Airworthiness Directive (AD) 97-13-02, which was sent previously to all known U.S. owners and operators of Diamond Aircraft Industries, Inc. (Diamond) Model DA 20-A1 airplanes. This AD requires fabricating and installing a placard and inserting limitations into the airplane's flight manual limitations section prohibiting spin maneuvers until a modification is installed. This AD results from an occurrence where a pilot's shoe jammed between the rudder control pedal and the firewall during a spin recovery in a Canadian registered HOAC-Austria Model DV 20 KATANA airplane. The actions specified by this AD are intended to prevent the pilot's shoe from becoming jammed between the rudder pedal and firewall which could result in loss of control of the airplane.
AD 97-14-06 · published Jul 3, 1997, effective Jul 18, 1997
Boeing Model 747 Series Airplanes, Excluding Airplanes Equipped With Pratt & Whitney PW4000 and General Electric CF6-80C2 Series Engines
This amendment supersedes an existing airworthiness directive (AD), applicable to certain Boeing 747 series airplanes, that currently requires replacement of certain fuse pins on the upper link of the inboard and outboard struts. That AD also requires inspections to detect corrosion or cracks of certain fuse pins, and replacement, if necessary. This amendment reduces the compliance times of actions associated with certain fuse pins and provides for optional terminating action for the requirements of this AD. This amendment is prompted by a report of fracturing of a bulkhead style fuse pin located in the inboard strut at the forward end of the upper link. The actions specified in this AD are intended to prevent failure of the strut and separation of an engine from the airplane due to fracturing of the fuse pins.
AD 97-14-07 · published Jul 3, 1997, effective Aug 7, 1997
Lockheed Model L-1011 Series Airplanes Equipped With Rolls-Royce Model RB211-524 Series Engines
This amendment supersedes an existing airworthiness directive (AD), applicable to certain Lockheed Model L-1011 series airplanes, that currently requires several modifications of the engine high speed gearboxes. This amendment requires that a new modification be installed in lieu of one of those previously required. This amendment is prompted by a report indicating that one of the currently required modifications is not completely effective because it can create interference problems between the fireloop and a fuel line. The actions specified by this AD are intended to reduce the possibility of a fire in the high speed gear boxes, and to ensure that any fire which may occur is readily detected by the flight crew.
AD 97-14-08 · published Jul 3, 1997, effective Aug 7, 1997
Gulfstream Aerospace Corporation Model G-159 (G-I) Airplanes
This amendment supersedes an existing airworthiness directive (AD), applicable to certain Gulfstream Model G-159 (G-I) airplanes, that currently requires repetitive inspections to detect cracks and loose rivets in the forward brackets for the main landing gear (MLG) uplock beam assembly, and replacement of the brackets, if necessary. This amendment requires installation of redesigned brackets that preclude the potential for cracking and loose rivets, when accomplished, this installation constitutes terminating action for the currently required inspections. This amendment is prompted by the development of an installation that will positively address the identified unsafe condition. The actions specified by this AD are intended to prevent failure of the bracket for the MLG uplock beam assembly due to cracking and loose rivets; such failure could result in the inability to retract the MLG.
AD 97-14-09 · published Jul 3, 1997, effective Aug 7, 1997
Gulfstream Aerospace Corporation Model G-159 (G-I) Airplanes
This amendment supersedes an existing airworthiness directive (AD), applicable to certain Gulfstream Model G-159 (G-I) airplanes, that currently requires repetitive inspections to detect cracking in the mounting lugs of the elevator trim tab actuators, and replacement, if necessary. This amendment requires the installation of improved elevator trim tab actuators that are not susceptible to the subject cracking. This amendment is prompted by the development of a modification that positively addresses the identified unsafe condition. The actions specified by this AD are intended to prevent failure of the mounting lugs on the elevator trim tab actuator due to cracking; such failure could result in severe vibration during flight and/or reduction or loss of elevator trim tab capability, which could lead to reduced controllability of the airplane.
AD 97-14-10 · published Jul 3, 1997, effective Aug 7, 1997
Gulfstream Aerospace Corporation Model G-159 (G-I) Airplanes
This amendment supersedes an existing airworthiness directive (AD), applicable to certain Gulfstream Model G-159 (G-I) airplanes, that currently requires modification and repetitive inspections for cracks in the main landing gear (MLG) retract cylinder attachment fittings. This amendment requires installation of improved attachment fittings which, when accomplished, terminates the requirement for the repetitive inspections. This amendment is prompted by the development of a modification that positively addresses the identified unsafe condition. The actions specified by this AD are intended to prevent failure of the MLG retract cylinder attachment fitting due to fatigue cracking. This condition, if not corrected, could result in the inability to retract the MLG.
AD 97-14-14 · published Jul 8, 1997, effective Aug 29, 1997
Industrie Aeronautiche E Meccaniche Model Piaggio P-180 Airplanes
This amendment adopts a new airworthiness directive (AD) that applies to certain Industrie Aeronautiche E Meccaniche (I.A.M.) Model Piaggio P-180 airplanes that are equipped with a certain freon air conditioning system. This AD requires inspecting the baggage compartment for stringer or air cycle machine (ACM) by-pass duct damage, repairing any damage found, and modifying the freon air inlet duct and electrical wiring. This AD results from trim system malfunction on one of the affected airplanes, resulting from contact between the freon air inlet duct and the electrical wiring. The actions specified by this AD are intended to prevent trim system malfunction caused by contact between the freon air inlet duct and electrical wiring, which could result in loss of control of the airplane.
AD 97-12-06 · published Jul 9, 1997, effective Jul 15, 1997
Cessna Aircraft Company Model 172R Airplanes
This document publishes in the Federal Register an amendment adopting Airworthiness Directive (AD) 97-12-06, which was sent previously to known U.S. owners and operators of certain Cessna Aircraft Company (Cessna) Model 172R airplanes. This AD requires checking the clearance between both the gascolator and cowling area and the tailpipe and cowling area, and modifying these areas immediately if any evidence of rubbing at either location is found or modifying the gascolator to cowling area within a certain time period if no evidence of rubbing at either location is found. This AD results from an occurrence of fuel loss on a Cessna Model 172R airplane, which was severe enough to force an emergency landing. Investigation of the occurrence reveals that the cowling knocked the gascolator drain valve off the gascolator. The actions specified by this AD are intended to prevent the cowling from rubbing against the gascolator drain valve or the tailpipe, which could result in fuel loss and engine stoppage.
AD 97-13-11 · published Jul 10, 1997, effective Jul 23, 1997
Ayres Corporation S2R Series Airplanes
This document publishes in the Federal Register an amendment adopting Airworthiness Directive (AD) 97-13-11, which was sent previously to known U.S. owners and operators of certain Ayres Corporation (Ayres) S2R series airplanes. This AD requires inspecting the \1/4\-inch and \5/16\-inch bolt hole areas on the lower spar caps for fatigue cracking, and replacing any lower spar cap if fatigue cracking is found. This AD results from an accident on an Ayres S2R series airplane where the wing separated from the airplane in flight. The actions specified by this AD are intended to prevent fatigue cracking of the lower spar caps, which, if not detected and corrected, could result in the wing separating from the airplane with consequent loss of control of the airplane.
AD 97-14-13 · published Jul 11, 1997, effective Aug 15, 1997
Gulfstream Aerospace Corporation Model G-159 (G-I) Airplanes
This amendment supersedes an existing airworthiness directive (AD), applicable to certain Gulfstream Model G-159 (G-I) airplanes, that currently requires repetitive inspections to detect chafe wear on the upper diagonal engine mount tube, and replacement or repair, if necessary. This amendment requires the installation of chafe guards at the engine mounts, which terminates the currently required inspections. It also requires that the chafe guards then be repetitively inspected for chafe wear. This amendment is prompted by the development of a modification that will provide better protection of the subject area against future chafe wear. The actions specified by this AD are intended to prevent excessive chafe wear in the area of the upper diagonal engine mount tubes and trusses; if not detected and corrected, such wear could result in failure of the engine mount assembly and possible separation of the engine from the airplane.
AD 97-14-16 · published Jul 11, 1997, effective Aug 4, 1997
Raytheon Aircraft Company (Formerly Beech Aircraft Corporation) Model 1900 Series Airplanes
This amendment adopts a new airworthiness directive (AD) that applies to all Raytheon Aircraft Company (Raytheon) 1900 series airplanes. This action requires repetitively inspecting the flap aft roller bearings and flap attachment brackets for indications of contact (wear), inspecting for elongation of the holes in the flap attachment brackets, and repairing or replacing any part showing wear. The actions specified by this AD are intended to prevent interference between the flap and the aileron which could inhibit aileron movement and result in possible loss of control of the airplane.
AD 97-15-02 · published Jul 15, 1997, effective Jul 30, 1997
Aerospatiale Model ATR42 and ATR72 Series Airplanes
This amendment adopts a new airworthiness directive (AD), applicable to all Aerospatiale Model ATR42 and ATR72 series airplanes, that requires replacement of the attachment clips on the wing-to- fuselage fairings and on the upper cowlings of the engine nacelle with new improved attachment clips, and adding cup washers on the wing-to- fuselage fairing panels on certain airplanes. This amendment also requires a one-time inspection of certain fairings and the upper cowlings of the engine nacelle to detect discrepancies of the attachment hardware and the fairing panel; and replacement of the panel with a serviceable panel, if necessary. This amendment is prompted by a report of deformed attachment clips found on the wing-to-fuselage fairings and on the upper cowlings of the engine nacelle, and by a report of severe inflight vibration due to a loose wing/body fairing panel. The actions specified by this AD are intended to prevent deformation of the attachment clips due to insufficient strength of the attachment clip material. Such deformation of the attachment clips could result in the fairings and cowlings detaching from the airplane during flight and subsequently causing damage to the empennage or posing a hazard to persons or property on the ground.
AD 97-15-05 · published Jul 16, 1997, effective Jul 31, 1997
British Aerospace (Jetstream) Model 4101 Airplanes
This amendment adopts a new airworthiness directive (AD) that is applicable to certain British Aerospace (Jetstream) Model 4101 airplanes. This action requires an inspection to determine the data on the label of certain hose assemblies, and replacement of all hose assemblies from any discrepant batch with certain new hose assemblies. This amendment is prompted by a report of failure of a hose assembly in the fire extinguisher system of the engine nacelle due to cracks, caused during manfacture of the hose assemblies, in the swaged ferrule that attaches the hose to the end fitting. The actions specified in this AD are intended to ensure that such discrepant hose assemblies are replaced. Discrepant hose assemblies could fail and consequently prevent the proper distribution of fire extinguishing agent within the engine nacelle in the event of a fire.
AD 97-15-06 · published Jul 16, 1997, effective Jul 31, 1997
Boeing Model 737, 747, 757, and 767 Series Airplanes
This amendment adopts a new airworthiness directive (AD) that is applicable to certain Boeing Model 737, 747, 757, and 767 series airplanes. This action requires a one-time operational test of the pilots' seat locks and the seat tracks to ensure that the seats lock in position and the seat tracks are aligned correctly; and re-alignment of the seat tracks, if necessary. This amendment is prompted by reports indicating that a pilot's seat slid from the forward position to the aft-most position during acceleration and take-off of the airplane due to misalignment of the seat tracks. The actions specified in this AD are intended to prevent uncommanded movement of the pilots' seats during acceleration and take-off of the airplane, and consequent reduced controllability of the airplane.
AD 97-14-11 · published Jul 17, 1997
Bombardier Model CL-600-2B19 (Regional Jet Series 100 and 200) Series Airplanes
This document publishes in the Federal Register an amendment adopting airworthiness directive (AD) 97-14-11 that was sent previously to all known U.S. owners and operators of certain Bombardier Model CL- 600-2B19 (Regional Jet Series 100 and 200) series airplanes by individual notices. This AD requires repetitive inspections to detect cracks of a certain bulkhead web of the fuselage at certain locations, and repair, if necessary. This action is prompted by a report of a pressurization problem during flight, which was caused by fatigue cracking in the underfloor pressure bulkhead of the fuselage. The actions specified by this AD are intended to detect and correct such fatigue cracking, which could result in uncontrolled depressurization of the airplane and/or reduced structural integrity of the fuselage.
AD 97-15-09 · published Jul 17, 1997, effective Aug 1, 1997
Boeing Model 757 and 767 Series Airplanes
This amendment adopts a new airworthiness directive (AD) that is applicable to all Boeing Model 757 and 767 series airplanes. This action requires repetitive inspections to detect damage and to verify proper configuration of the battery ground terminations of the auxiliary power unit (APU) at the battery and connected structure; and removal, replacement, and repair of the battery ground termination, if necessary. This amendment is prompted by reports of smoke or fire coming from the APU due to battery grounds that were not installed/ maintained properly. The actions specified in this AD are intended to detect and correct such APU battery grounds, which could result in heat damage and consequent smoke/fire on the airplane.
AD 97-14-05 · published Jul 18, 1997, effective Aug 25, 1997
Air Tractor Incorporated Models AT-301, AT-302, AT-400, AT-400A, AT-401, AT-402, AT-501, and AT-502 Airplanes
This amendment supersedes Airworthiness Directive AD 95-20-06, which applies to certain Air Tractor Incorporated (Air Tractor) Models AT-301, AT-302, AT-400, AT-400A, AT-401, AT-402, AT-501, and AT-502 airplanes and currently requires repetitively inspecting the front spar attachment lugs and the rear spar for fatigue cracks, and modifying the vertical fin if cracks are found. The modification terminates the repetitive inspection requirement of AD 95-20-06 and may be incorporated at any time, if cracks are not found. The FAA has determined that the Air Tractor Models mentioned above with a \1/4\- inch fin front spar fitting installed should be exempt from the AD. The AD will retain the requirements of AD 95-20-06 for all Air Tractor airplanes that have a \3/16\-inch fin front spar fitting. The actions specified by this AD are intended to prevent in-flight vertical fin cracking, which, if not detected and corrected, could result in structural failure of the front spar attachments and eventually the rear spar attachment and cause loss of directional control of the airplane.
AD 97-14-15 · published Jul 21, 1997, effective Sep 2, 1997
Raytheon Aircraft Company (Formerly Known as Beech Aircraft Corporation) Models E33, F33, G33, E33A, F33A, E33C, F33C, C35, D35, E35, F35, G35, H35, J35, K35, M35, N35, P35, S35, V35, V35A, V35B, V35TC, V35ATC, V35BTC, 36, A36, A36TC, B36TC, 50, B50, C50, 95-55, 95A55, 95B55, 95C55, D55, E55, 56TC, A56TC, 58, 58TC, 95, B95, B95A, D95A, and E95 Airplanes
This amendment adopts a new airworthiness directive (AD) that applies to Raytheon Aircraft Company (formerly known as Beech Aircraft Corporation) Models E33, F33, G33, E33A, F33A, E33C, F33C, C35, D35, E35, F35, G35, H35, J35, K35, M35, N35, P35, S35, V35, V35A, V35B, V35TC, V35ATC, V35BTC, 36, A36, A36TC, B36TC, 50, B50, C50, 95-55, 95A55, 95B55, 95C55, D55, E55, 56TC, A56TC, 58, 58TC, 95, B95, B95A, D95A, and E95 airplanes. This action requires checking the cabin side door handle and the utility door handle from the interior of the airplane for proper locking. If the door handles do not lock, the proposed AD would require reinstalling the door handles correctly for the lock to engage. Nine reports of the utility and cabin door handle opening from the interior of the airplane without depressing the lock release button prompted this action. The actions specified by this AD are intended to prevent unintentional opening of the cabin side door and the utility door from the interior of the airplane, which, if not detected and corrected, could result in loss of control of the airplane.
AD 97-15-13 · published Jul 25, 1997, effective Sep 5, 1997
Raytheon Aircraft Company (Formerly Beech Aircraft Corporation) Models 1900, 1900C, and 1900D Airplanes
This amendment adopts a new airworthiness directive (AD) that applies to certain Raytheon Aircraft Company (Raytheon) Models 1900, 1900C, and 1900D airplanes (formerly referred to as Beech Models 1900, 1900C, and 1900D airplanes). This action requires installing lubrication fittings in the airstair door handle and latch housing mechanisms. The AD results from reports of the airstair door not opening because the door was frozen shut. The actions specified by this AD are intended to prevent moisture from accumulating and freezing in the airstair door handle and latch housing, which could result in the door freezing shut and passengers not being able to evacuate the airplane in an emergency situation.
AD 97-15-14 · published Jul 28, 1997, effective Sep 19, 1997
Industrie Aeronautiche e Meccaniche Rinaldo Piaggio S.p.A. Model P-180 Airplanes
This amendment adopts a new airworthiness directive (AD) that applies to Industrie Aeronautiche e Meccaniche Rinaldo Piaggio S.p.A. (Piaggio) Model P-180 airplanes. This action requires inspecting for cracks around the vertical pin and the torque tube bottom flange of the rudder, and the fasteners that connect the torque tube to the bottom flange (torque tube bottom flange assembly). If cracks are not found, repetitively inspect until cracks are visible. If cracks are evident, this action requires modifying the rudder torque tube bottom flange assembly by replacing the cracked part with a part of improved design, which terminates the repetitive inspection. This AD is the result of several reports of fatigue cracks around the pin that vertically supports the rudder axle. The actions specified by this AD are intended to prevent fatigue cracks in the rudder torque tube bottom flange, which could result in loss of rudder control and possible loss of the airplane.
AD 97-15-17 · published Jul 28, 1997, effective Sep 2, 1997
Saab Model SAAB 2000 Series Airplanes
This amendment adopts a new airworthiness directive (AD), applicable to certain Saab Model SAAB 2000 series airplanes, that requires replacing the Abex alternating current (AC) electric motor with a new modified Abex AC electric motor having an improved fan. This amendment is prompted by reports indicating that the integrated hydraulic package (IHP) unit stopped functioning during flight because the fan on the AC electric motor came into contact with the housing of the motor due to inadequate clearance. The actions specified by this AD are intended to prevent loss of IHP function, which, if combined with other hydraulic system failures, could result in reduced controllability of the airplane.
AD 97-16-01 · published Jul 28, 1997, effective Aug 12, 1997
British Aerospace (Jetstream) Model 4101 Airplanes
This amendment adopts a new airworthiness directive (AD) that is applicable to certain British Aerospace (Jetstream) Model 4101 airplanes. This action requires repetitive detailed visual inspections to detect cracks of the shear cleats of the roller guide structural support of the passenger door, and replacement of any cracked shear cleat with a new shear cleat. This action also provides for an optional terminating modification that constitutes terminating action for the repetitive inspections. This amendment is prompted by a report indicating that fatigue cracking was found in the roller guide shear cleats of the passenger door. The actions specified in this AD are intended to detect and correct such fatigue-related cracking, which could result in structural failure of the passenger door, and consequent rapid depressurization of the airplane or loss of the passenger door while the airplane is in flight.
AD 97-15-04 · published Jul 15, 1997, effective Aug 19, 1997
Bell Helicopter Textron, Inc. Model 214B, 214B-1, and 214ST Helicopters
This amendment supersedes an existing airworthiness directive (AD), applicable to Bell Helicopter Textron, Inc. (BHTI) Model 214B, 214B-1, and 214ST helicopters, that currently establishes a mandatory retirement life of 60,000 high-power events for the main transmission upper planetary carrier (carrier). This amendment requires changing the method of calculating retirement life for the carrier from high-power events to a maximum accumulated Retirement Index Number (RIN) of 120,000. This amendment is prompted by fatigue analyses and tests that show certain carriers fail sooner than originally anticipated because of the unanticipated high number of lifts or takeoffs (torque events) performed with those carriers in addition to the time-in-service (TIS) accrued under other operating conditions. The actions specified by this AD are intended to prevent fatigue failure of the carrier, which could result in failure of the main transmission and subsequent loss of control of the helicopter.
AD 97-15-08 · published Jul 18, 1997, effective Aug 4, 1997
McDonnell Douglas Helicopter Systems Model 369D, E, F, FF, 500N, AH-6, and MH-6 Helicopters
This amendment adopts a new airworthiness directive (AD) that is applicable to McDonnell Douglas Helicopter Systems (MDHS) Model 369D, E, F, FF, 500N, AH-6, and MH-6 helicopters. This action requires replacement of certain transmission output drive gears (gears). This amendment is prompted by several reports of spalled or fractured gear teeth, most of which occurred during high-power or external-lift operations. The actions specified in this AD are intended to prevent failure of the gear, which could result in loss of main rotor control and subsequent loss of control of the helicopter.
AD 97-15-10 · published Jul 23, 1997, effective Sep 22, 1997
AlliedSignal Inc. TPE331 Series Turboprop Engines
This amendment adopts a new airworthiness directive (AD), applicable to AlliedSignal Inc. (formerly Garrett Engine Division and Garrett Turbine Engine Company) TPE331 series turboprop engines equipped with Woodward fuel controls, that requires revising the applicable Emergency Procedures or Abnormal Procedures Section of the applicable Federal Aviation Administration (FAA)-approved Airplane Flight Manual (AFM) or Pilot's Operating Handbook (POH) to include a paragraph relating to a non-responsive power lever. In addition, this AD requires replacing or reworking orifice fittings and restrictors, which would constitute terminating action to the requirement to revise the applicable AFM. This amendment is prompted by reports of occasional icing of the inlet Pt2 sensor, which can produce an erroneous (high) pressure signal to the fuel control, causing little or no response to power lever movement. The actions specified by this AD are intended to prevent a non-responsive power lever and lack of control of engine power.
AD 97-15-11 · published Jul 28, 1997, effective Aug 12, 1997
Avco Lycoming and Textron Lycoming Reciprocating Engines
This amendment supersedes an existing airworthiness directive (AD), applicable to Avco Lycoming and Textron Lycoming reciprocating engines, that currently requires removal from service of defective piston pins, and replacement with serviceable parts. This amendment adds additional affected engine models that may have defective piston pins installed, and references a revised service bulletin. This amendment is prompted by the determination that additional engine models may have defective piston pins installed. The actions specified by this AD are intended to prevent piston pin failure, which could result in engine failure.
AD 97-08-06 R1 · published Jul 22, 1997, effective Aug 1, 1997
Alexander Schleicher GmbH & Co., Burkhart Grob Luft-Und, Centrair, DG Flugzeugbau GmbH, Eiriavion Oy, Glaser-Dirks Flugzeugbau GmbH, GROB-WERKE GMBH & CO KG, Intreprinderea De Constructii Aeronautice, L'Hotellier, Louis, Rolladen-Schneider Flugzeugbau GmbH, Schempp-Hirth Flugzeugbau Appliances
This document clarifies information in Airworthiness Directive (AD) 97-08-06 that applies to Louis L'Hotellier S.A. (L'Hotellier) ball and swivel joint quick connectors installed on gliders and sailplanes that are not equipped with a "Uerling" sleeve or an LS-safety sleeve. These connectors allow the operator of the gliders and sailplanes to quickly connect and disconnect the control systems during assembly and disassembly for storage purposes. AD 97-08-06 currently requires enlarging the safety pin guide hole diameter, and fabricating and installing a placard that specifies the requirement of securing the control system connectors with safety wire, pins, or safety sleeves prior to each flight. The actions specified in that AD are intended to prevent the connectors from becoming inadvertently disconnected, which could result in loss of control of the sailplane or glider. This document clarifies the applicability and modification instructions of AD 97-08-06 by including additional instructions to accomplish the same actions. This correction of the AD results from several operators expressing uncertainty about the applicability and modification instructions.
AD 97-15-12 · published Jul 23, 1997, effective Sep 19, 1997
Burkhart Grob, Luft- und Raumfahrt, Model G 109 Sailplanes
This amendment adopts a new airworthiness directive (AD) that applies to certain Burkhart Grob, Luft- und Raumfahrt (Grob) Model G 109 sailplanes. This action requires installing a damper and new bell crank lever on the rudder, in addition to adjusting the weight and balance of the sailplane, to correct the tendency of flutter at specific excitation frequencies. For those Grob Model G 109 sailplanes that have previously accomplished this installation, a modification to the damper and bell crank lever, and adjustment to the weight and balance is required. These actions are prompted by the discovery of rudder vibration problems during testing of two Grob Model G 109 sailplanes. The actions specified by this AD are intended to prevent vibration of the rudder, which could result in structural damage and eventual loss of control of the sailplane.
