AD 81-16-08 R3

81-16-08 R3 GATES LEARJET: Amendment 39-4184 as amended by Amendment 39-4295 and 39-4338 is further amended by Amendment 39-4546. Applies to the following models and serial number airplanes certificated in any category:

MODELS SERIAL NUMBERS LEARJET AFM DESIGNATION 24E, 24F 350, 352, 353, 354, 356, and subsequent 24-350, 24-352, 24-353, 24-354, 24-356 and subsequent 25D, 25F 206 thru 336 338 thru 341 25-206 thru 25-336, 25-338 thru 25-341

COMPLIANCE: Required as indicated, unless previously accomplished. To assure that the crew is provided with limitations for the safe operation of the airplane and to reduce the possibility of an unsafe condition resulting from a system's malfunction, accomplish the following:

A) Before further flight, insert the following information in the FAA Approved Airplane Flight Manual and operate the airplane in accordance with these limitations:

1. In Section 1, LIMITATIONS, adjacent to MAXIMUM OPERATING ALTITUDE:a. Delete any procedures relative to maximum operation altitudes of 51,000 feet.

b. Add the following limitation for Model 25D/F: Aircraft 25-230 and subsequent: "The maximum operating altitude is 45,000 feet. This is the highest altitude for which acceptable flight characteristics and systems operation have been demonstrated."

c. Add the following limitation for Model 24E: Aircraft 24-350, 24-352 and subsequent, except 24-355: "The maximum operating altitude is 45,000 feet. This is the highest altitude for which acceptable flight characteristics and systems operation have been demonstrated."

d. Add the following limitation for Model 24F: Aircraft 24-350 and subsequent when CJ610-8A engines are installed: "The maximum operating altitude is 45,000 feet. This is the highest altitude for which acceptable flight characteristics and systems operation have been demonstrated."

B) In order to comply with the requirements of paragraph A) of this Airworthiness Directive, this AD, or a duplicate thereof, may be used as a temporary amendment to the Airplane Flight Manual and carried in the aircraft as part of the Airplane Flight Manual until replaced by revisions to the Airplane Flight Manual provided by the manufacturer and approved by the FAA. The Airplane Flight Manual changes required by paragraph A) of this AD may be accomplished by the holder of at least a private pilot certificate issued under Part 61 of the Federal Aviation Regulations on any airplane owned or operated by that person who must make the prescribed entry in the Airplane Maintenance Records indicating compliance with paragraph A) of this AD.

C) Prior to accomplishing the modification required by paragraph D) of this AD, contact the FAA office noted in paragraph F) if any modification or alteration has been performed on the affected airplane for further instruction relative to the compatibility of the modification of this AD.

D) On or before May 31, 1982, accomplish the following requirements of this paragraph at an FAA certificated maintenance repair agency. However, the modification and inspection of the horizontal stabilizer trim actuator as required in the airplane modification kits referenced in subparagraph 1 below may be performed by another FAA certificated repair agency utilizing qualified technicians who must have recent accessory overhaul experience performing the overhaul and test of the Gates Learjet Horizontal Stabilizer Trim Actuator with the necessary shop equipment (Attachment I hereto) as referenced in Learjet Repair Manual Number 1711-9, or the equivalent equipment.

1. Modify-Learjet Model 25D and 25F flight control systems, stall warning system and control wheel in accordance with Gates Learjet Airplane Modification Kits AMK 81- 7, AMK 81-8 and AMK 80-13, Change 3, respectively.

2. Insert in the appropriate sections of the existing Airplane Flight Manual (AFM), the FAA-approved temporary Airplane Flight Manual Change dated June 8, 1981, or equivalent permanent AFM revision pertaining to procedures required as a result of the modification of the flight control system in accordance with Airplane Modification Kit AMK 81- 7 and delete superseded AFM revisions previously required by paragraphs A)2, A)5 and A)6 of AD 80-19-11.

E) Operators of Model 24E, and 24F, S/N 350, 352, 353, 354, 356, and subsequent, desiring to remove the 45,000 feet limitation of paragraph A), above, may do so by accomplishing the following requirements of this paragraph at a FAA certified maintenance repair agency. However, the modification and inspection of the horizontal stabilizer trim actuator as required in the airplane modification kits referenced in subparagraph 1 below may be performed by another FAA certificated repair agency utilizing qualified technicians who must have recent accessory overhaul experience performing the overhaul and test of the Gates Learjet Horizontal Stabilizer Trim Actuator with the necessary shop equipment (Attachment I hereto) as referenced in Learjet Repair Manual Number 1711-9, or the equivalent equipment.

1. Install AMK 82-6, Engine Stall Warning System, and concurrently required kits called out in "PARTS REQUIRED," namely: AMK 81-13, Horizontal Stabilizer Trim and Autopilot Improvement, AMK 82-4 Autopilot Pitch Nose Down Limiter, and AAK 82- 5 Autopilot Roll Rate Limiter.

2. Incorporate FAA approved Airplane Flight Manual (AFM) Change 9 for Model 24E and Change 7 for Model 24F, which supersedes AFM revisions previously required by paragraph A), above, and delete superseded AFM revisions previously required by paragraphs A)2, A)5, and A)6 of AD 80-19-11.

3. Insert FAA approved AFM Supplement AFMS: W1018, which supersedes previous AFM supplements for FC-110 autopilot.

F) Operators of Model 25D and 25F, S/N 230 thru 341, and 343 thru 362, desiring to remove the 45,000 feet limitation of paragraph A), above, may do so by accomplishingthe following requirements at an FAA certificated maintenance repair agency

1. Install AMK 81-12 Engine Stall Warning System, and concurrently required kits called out in "PARTS REQUIRED," namely: AMK 82-4 Autopilot pitch nose down limiter and AAK 82-5 Autopilot Roll Rate Limiter.

2. Incorporate FAA approved Airplane Flight Manual (AFM) Change 8 to the FAA approved Airplane Flight Manual which supersedes AFM revisions previously required by paragraph A), above.

3. Insert FAA approved AFM Supplement AFMS: WI008, Change 1, which supersedes previous AFM supplements for FC-110 autopilot.

G) The modifications described above have been incorporated by the manufacturer on airplanes Model 25D and 25F, S/N 342, 363, and subsequent.

H) Airplanes may be flown in accordance with FAR 21.197 to a location where modifications required by this AD can be accomplished.

I) Any equivalent method of compliance with this AD must be approved by the Manager, Wichita AircraftCertification Office, FAA, Central Region, Room 238, Terminal Building No. 2299, Mid-Continent Airport, Wichita, Kansas 67209.

The manufacturer's specifications and procedures identified and described in this directive are incorporated herein and made a part hereof pursuant to 5 U.S.C. 552(a)(1). All persons affected by this directive who have not already received these documents from the manufacturer may obtain copies upon request from Gates Learjet corporation, P.O. Box 7707, Wichita, Kansas 67277. These documents may also be examined at FAA, Central Region, Wichita Aircraft Certification Office, Room 238, Terminal Building 2299, Mid-Continent Airport, Wichita, Kansas 67209.

Amendment 39-4184 became effective on July 31, 1981.

Amendment 39-4295 became effective January 21, 1982.

Amendment 39-4338 became effective on February 27, 1982.

This Amendment 39-4546 becomes effective February 7, 1983

ATTACHMENT I

The stabilizer actuator test stand (P/NST-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 readoutindicator 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 and be accurate 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. Pe-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 operatethe 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.