AD 84-17-02

84-17-02 GATES LEARJET: Amendment 39-4902. Applies to Gates Learjet Model 24 series airplanes certificated in all categories. Compliance required within eighteen (18) months after effective date unless previously accomplished or prior compliance with AD 81-16-08, Amendment 39-4546.

Accomplish the requirements of this AD at an FAA approved repair station. The modification and inspection of the horizontal stabilizer trim actuator must be performed by an FAA certificated repair agency authorized to overhaul and test the Gates Learjet Horizontal Stabilizer Trim Actuator. The necessary shop equipment or the equivalent, as referenced in Learjet Repair Manual Number 1711-9, is listed in Attachment I hereto.

A. Modify Learjet Model 24 airplane flight control systems, stall warning, and control wheel by incorporating the airplane modification kit listed in Table I.

Table I MODIFICATION KIT MODEL AMK 82-5 24, 24A AMK 82-1 24B, 24B-A AMK 81-18 24D, 24D-A AMK81-13 24E, 24F, 24F-A

NOTE: Modification of JET Autopilot Controllers and Computers as required by the instructions in the above kits must be performed in an FAA approved facility for maintenance of the JET FC-110 autopilot.

B. Required Airplane Maintenance Record entry must be accomplished by the facility performing its portion of the AD as prescribed in paragraph A. of this AD.

C. After airplane modification, verify that the Airplane Flight Manual (AFM) contains the revision/change listed in Table II, below, or later FAA approved revision/change. Upon completion of the modifications required by paragraph A. of this AD, the more restrictive paragraphs A.2., A.5., and A.6. of AD 80-19-11 are no longer applicable.

Table II Gates Learjet Airplane Flight Manual/Supplement

Revision/Change

Modification kit 1. 24 AFM, FM- 004 Revision 32 AMK82-5 2. 24 RAS AFM, W0159 Revision 4 AMK82-5 3. 24A AFM, FM-005 Revision 18 AMK82-5 4. 24E CR 736 AFM, FM-008 Revision 7 AMK82-5 5. FC-110 Autopilot, W1037 New AMK82-5 6. 24B AFM, FM-006 Revision 21 AMK82-1 7. 24B-A AFM, FM-007 Revision 21 to 24B AMK82-1 8. 24B RAS AFM, W0157 Revision 3 AMK82-1 9. FC-110 Autopilot, W1041 New AMK82-1 10. 24D AFM, FM-009 Change 18 AMK81-18 11. 24D-A AFM, FM-010 Change 18 to 24D AMK81-18 12. 24D RAS AFM, W-0119 Change 3 AMK81-18 13. FC-110 Autopilot, W1030 New AMK81-18 14. 24E AFM, FM-011 Change 9 AMK81-13 15. 24F AFM, FM-012 Change 7 AMK81-13 16. FC-110 Autopilot, W1018 New AMK81-13

D. Prior to accomplishing the modification required by paragraph A. of this AD, contact the Wichita Aircraft Certification Office, FAA, Central Region, telephone (316) 269- 7008, if any modification or alteration has been performed on the affected airplane systems, for further instruction relative to the compatibility of the modification and this AD.

E. Alternate methods of compliance with this AD may be used if they are approved by the Manager, Wichita Aircraft Certification Office, FAA, Central Region.

This amendment becomes effective October 5, 1984.

ATTACHMENT I

The stabilizer actuator test stand (P/N ST-00463) is used to functionally test the stabilizer actuator after overhaul. The physical structure of the test stand must be capable of withstanding a minimum load of 2500 lbs. without any bending or deformation.

The stabilizer actuator is vertically mounted on the test stand with one end stationary and the other end movable through a hydraulic actuator. The test stand consists of the following components:

a. Hydraulic Actuator - The hydraulic actuator is capable of applying a regulated load of 0 to 2500 lbs. on the stabilizer actuator during the entire extend or retract cycles.

b. Hydraulic Pressure Regulator - The pressure regulator is used to select hydraulic pressures applied to the stabilizer actuator during the functional test.

c. Hydraulic Pressure Gauge - The hydraulic pressure gauge is used to monitor hydraulic pressure applied to the stabilizer actuator. The gauge must be certified at least monthly.

d. Digital Position Readout - The digital position readout indicator is used to monitor the travel of the stabilizer actuator. Signals to the indicator are picked up from a rigid mounted linear potentiometer and movable wiper attached to the hydraulic actuator. The digital readout is accurate to 1/1000th of an inch.

e. Linear Scale - A linear scale, graduated in 100th of an inch, is permanently mounted on the test stand to verify the digital readout. A tool of known length is used to verify the linear scale and digital readout before the stabilizer actuator functional test is performed. The tool length must be certified at least yearly.

f. Lapse Timer - A lapse timer is coupled to the control switches and the stabilizer actuator to monitor travel time during the extend and retract cycles. The lapse timer must measure seconds to beaccurate to 1/100th of a second.

g. Trim Controller - The trim controller is used to simulate two-speed input to the stabilizer actuator primary motor. The trim controller part number is EM 2079-6.

h. Pre-Select Timer - The pre-select timer is used to check stabilizer actuator travel vs. time, voltage, and amperage inputs in accordance with the functional test.

i. Power Supply - The power supply is variable through 0-30 volts DC and 0-30 amperes DC.

j. DC Voltmeter - The DC voltmeter must be capable of measuring 0-30 volts DC and must be certified at least yearly. The voltmeter is used to monitor the voltage inputs to the stabilizer actuator in accordance with the functional test.

k. DC Ammeter - The DC ammeter must be capable of measuring 0-30 amperes DC and must be certified at least yearly. The ammeter is used to monitor the amperes inputs to the stabilizer actuator in accordance with the functional test.

l. Millivolt Meter - The millivolt meter is used to monitor the stabilizer actuator linear potentiometer for a smooth and steady signal output. The meter is 0-50 volts graduated in 100 mv increments.

m. Switches - Necessary switches installed to operate the stabilizer actuator primary and secondary motors to extend or retract.

n. A digital or Simpson 260 meter, not a part of the test stand, is used to verify the resistance of the stabilizer actuator linear potentiometer. The digital or Simpson 260 meter must be certified at least every 90 working days.