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80-19-11 R1: 80-19-11 R1 GATES LEARJET: Amendment 39-3932 as amended by Amendment 39-5039. Applies to the following models and serial number airplanes, unless noted:
MODEL
SERIAL NUMBERS
23
23-003 through 23-099
24, 24A
24-100 through 24-180
24B, 24B-A
24-181 through 24-217
24-219 through 24-229
24C, 24D, 24D-A
24-218, 24-230 through 24-328
24E, 24F, 24F-A
24-329 and subsequent
25, 25A
25-003 through 25-060
25B, 25C
25-061, 25-067 through 25-201,
25-204, 25-205
25D, 25F
25-206 and subsequent
28, 29
28-001 and subsequent
29-001 and subsequent
35, 36, 35A, 36A
35-001 and subsequent
36-001 and subsequent
COMPLIANCE: Required as indicated, unless previously accomplished.
To assure that the crew is provided additional instructions for the safe operation of the airplane and that the airplane's automatic flight control and stall warning systems are properly adjusted, 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 insertions:
1. In Section 1, LIMITATIONS, adjacent to AIRSPEED LIMITS, MAXIMUM OPERATING SPEED VMO/MMO:
a. Delete any procedures relative to exceeding VMO or MMO.
b. Add the following limitation:
WARNING: Do not extend the spoilers, or operate with the spoilers deployed, at speeds above VMO/MMO due to the significant nose down pitching moment associated with spoiler deployment.
2. In Section 1, LIMITATIONS, add a new limitation:
TRIM SYSTEMS
a. To assure proper trim systems operations, the BEFORE STARTING ENGINES trim system checks must be successfully completed before each flight.
WARNING: Failure to conduct a complete pitch trim preflight check prior to each flight increases the probability of an undetected system failure. An additional single failure in the trim system could result in a runaway. In certain critical flight conditions an unrestrained runaway could result in high speeds, severe buffet, wing roll off, loads in excess of structural limit and extremely high forces necessary for recovery.
b. Pitch trim system runaway training that actually involves running the trim in flight to simulate malfunctions is prohibited.
3. In Section 1, LIMITATIONS, adjacent to STALL WARNING SYSTEM, add the following:
On Models 23, 24, 24A, 24B, 24B-A, 24D, 24D-A, 25, 25A, 25B, and 25C with unmodified wings, and the same models with Howard/Raisbeck Mark II wings:
WARNING: Do not intentionally fly the airplane slower than initial stall warning (shaker) onset.
4. In Section 1, LIMITATIONS, adjacent to YAW DAMPER:
a. Delete any references to disengaging the yaw damper before landing, or landing with the yaw damper engaged.
b. Add the following yaw damper requirements:
On landing, the following yaw damper disengage procedures shall apply:
(1) The airplane shall be configured forlanding at least 500 ft. AGL for normal landing:
(2) The yaw damper shall be disengaged during the landing flare.
CAUTION: If landings are attempted in turbulent air conditions with the yaw damper OFF, the airplane may exhibit undesirable lateral-directional (Dutch-Roll) characteristics. These characteristics are improved as the wing/tip fuel is consumed. The pilot shall observe the NOTE relative to turbulence contained in the BEFORE LANDING section of Section II of the Airplane Flight Manual and increase airspeed as required.
5. In Section II, NORMAL OPERATION PROCEDURES, adjacent to BEFORE STARTING ENGINES Procedures:
a. Delete current preflight procedures on all trim systems.
b. Add the following new trim system preflight checks:
NOTE: Some early Model 23, 24 airplanes incorporate a cutoff button that interrupts pitch, roll and yaw axes.
(1) Pitch Trim Selector Switch--EMER (or SEC).
(2) Operate EMERGENCY (or SEC) pitch trim switch NOSE UP and NOSE DOWN and check for stabilizer movement. Stabilizer movement will be approximately one-half of the rate of primary trim.
(3) Either Control Wheel Trim Switch - Operate NOSE UP and NOSE DOWN. Trim motion shall not occur.
(4) Pitch Trim Selector Switch - OFF.
(5) Actuate pilot's and copilot's Control Wheel Trim and Trim Arming Switches (if applicable) and pedestal EMERGENCY (or SEC) Pitch Trim Switch. Trim motion shall not occur.
(6) Pitch Trim Selector Switch - NORM (or PRI).
(7) EMERGENCY (or SEC) Pitch Trim Switch - Operate NOSE UP and NOSE DOWN. Trim motion shall not occur.
NOTE: On all Model 23 airplanes and Model 24 (Serial Number 24-100 through 24-169) airplanes, except for those incorporating Accessory Kit AAK70-3, trim motion will occur.
(8) Pilot's Control Wheel Trim Switch - Without depressing arming button (if applicable), move switch to LWD, RWD, NOSE UP, and NOSE DOWN; trim motion shall not occur. Depress
arming button (if applicable); trim motion shall not occur. Then depress arming button (if applicable) and move switch to LWD, RWD, NOSE UP and NOSE DOWN; trim motion shall occur.
(9) Repeat Step (8) for Copilot's Control Wheel Trim Switch.
(10) Trim by positioning Copilot's Control Wheel Trim Switch in one direction; then trim in opposite direction using the Pilot's Control Wheel Trim Switch. Pilot's trim shall override the Copilot's trim. Repeat for all lateral and pitch trim positions.
(11) Pilot's Control Wheel Trim Switch - NOSE UP. While trimming, depress Control Wheel Master Switch (if applicable) or Cutoff Button (if applicable); trim motion shall stop when the Control Wheel Master Switch is held. Repeat procedure for NOSE DN condition; trim motion shall stop. Repeat procedure for LWD & RWD lateral trim on airplanes equipped with Cutoff Button. (The procedures in this paragraph are not applicable to Model 25, S.N. 25-003 through 25-205 and Model 24, S.N. 24-170 through 24-328, except those airplanes modified by AAK76-4A.)
(12) Repeat Step (11) using copilot's Control Wheel Trim Switch, and Control Wheel Master Switch (if applicable), or Cutoff Button (if applicable).
(13) YAW TRIM Switch - Operate each half separately (if installed); trim motion shall not occur.
(14) YAW TRIM Switch - Operate both halves simultaneously; trim motion shall occur. On aircraft with Cutoff Button, check that the Cutoff Button stops the trim.
(15) Trim - Set all axes for takeoff.
6. In Section III, EMERGENCY PROCEDURES, add a new PITCH UPSET (NOSE-UP or NOSE-DOWN) Emergency Procedure:
A nose-up pitch axis malfunction or nose-up pitch trim system runaway can result in extremely high pitch attitudes, heavy airframe buffet, and require control forces in excess of 75 pounds for recovery. A nose-down pitch axis malfunction, nose-down pitch trim system runaway, or nose-down overspeed can result in extremely high airspeeds and require control forces in excess of 75 pounds for recovery.
WARNING: Do not extend spoilers on any nose-down pitch upset at any speed due to significant nose-down pitching moment associated with spoiler deployment.
NOTE: Control pressures may be heavy. Copilot assistance is recommended with this procedure.
IMMEDIATELY:
a. Attitude Control - As required to maintain aircraft control.
- If in nose-up attitude, roll into bank or maintain existing bank until the aircraft nose passes through the horizon.
- If in nose-down attitude, level the wings before pulling the nose up.
b. Thrust levers - As required. (If in nose-down attitude, immediately reduce thrust levers to IDLE position.)
c. Control Wheel Master Switch or Cutoff Button - Depress and hold until step g. is accomplished.
d. PITCH TRIM Selector Switch - OFF.
e. STALL WARNING Switches - OFF.
WARNING: On any speed excursions beyond MMO, the elevator control must be smoothly and steadily applied to prevent encountering excessive aileron activity and airframe buffet. Beyond .85 M1, a 1.5 g pull-up may be sufficient to excite aileron activity and the g level must be limited to that required to maintain lateral control.
AFTER AIRCRAFT CONTROL IS REGAINED:
f. Spoilers - Check retracted.
g. Autopilot's Pitch Circuit Breaker - Pull.
h. If control force continues, select other trim system and retrim the aircraft.
i. Isolate malfunctioning system by switching systems ON one at a time. Pause between activating each system to determine the defective system.
7. In Section IV, PERFORMANCE DATA, adjacent to the appropriate takeoff charts, add the following:
Increase all Chart V1, VR and V2 speeds by:
a. Model 23, 24, 24A, 24B, 24B-A, 24D, 24D-A, 25, 25A, 25B, 25C, with unmodified wings, plus 5 KNOTS Indicated Airspeed.
b. Model 23, 24, 24A, 24B, 24B-A, 24D, 24D-A, 25, 25A, 25B, 25C, with Howard/Raisbeck Mark II wings, plus 5 KNOTS Indicated Airspeed. (Increase applies to FLAP 10 and FLAP 20 charts, and is not applicable to FLAP 10 OVERSPEED chart.)
8. In Section IV, PERFORMANCE DATA, adjacent to each TAKEOFF DISTANCE CHART, add the following:
Increase all chart takeoff distances by:
a. Model 23, 24, 24A, 24B, 24B-A, 24D, 24D-A, 25, 25A, 25B, 25C, with unmodified wings, plus 10 percent.
b. Model 23, 24, 24A, 24B, 24B-A, 24D, 24D-A, 25, 25A, 25B, 25C, with Howard/Raisbeck Mark II wings, plus 10 percent. (Increase applies to FLAP 10 and FLAP 20 charts, and is not applicable to FLAP 10 OVERSPEED chart.)
9. In Section IV, PERFORMANCE DATA, adjacent to each TAKEOFF WEIGHT LIMITS chart, add the following:
a. Reduce the Limiting Weight-Brake Energy takeoff weights for Model 23, 24, 24A, 24B, 24B-A, 24D, 24D-A, 25, 25A, 25B, 25C, with unmodified wings, 500 lbs.
b. Reduce the FLAP 10 and FLAP 20 takeoff weight limits for Model 23, 24, 24A, 24B, 24B-A, 24D, 24D-A, 25, 25A, 25B, 25C, with Howard/Raisbeck Mark II wings, 500 lbs, if the airplane is at climb limited gross weight and if takeoff weight is above 14,500 lbs. For takeoff weights above 14,000 lbs. and below 14,500 lbs., reduce the weight to 14,000 lbs. Takeoff weight reduction not applicable to FLAP 10 OVERSPEED.
10. In Section IV PERFORMANCE DATA, adjacent to LANDING APPROACH SPEEDS chart, add the following:
Increase all chart Landing Approach Speeds by:
a. Model 23, 24, 24A, with unmodified wings, plus 8 KNOTS Indicated Airspeed.
b. Model 23, 24, 24A with ECR 736 (CJ610-6 engines and increased gross weight), and Model 24B, 24B-A, 24D, 24D-A, with unmodified wings, plus 4 KNOTS Indicated Airspeed.
c. Model 25, 25A, with unmodified wings, plus 3 KNOTS Indicated Airspeed.
d. Model 25, 25A, with unmodified wings with ECR 936 (AAK 70-5), plus 5 KNOTS Indicated Airspeed.
e. Model 25B, 25C, with unmodified wings, plus 5 KNOTS Indicated Airspeed.
f. Model 23, 24, 24A, 24B, 24B-A, 24D, 24D-A, 25, 25A, 25B, 25C, with Howard/Raisbeck Mark II wings, plus 5 KNOTS Indicated Airspeed.
11. In Section IV, PERFORMANCE DATA, adjacent to each LANDING DISTANCE CHART, add the following:
Increase all chart landing distances by:
a. Model 23, 24 and 24A, with unmodified wings, plus 10 percent.
b. Model 23, 24, 24A with ECR 736 (CJ610-6 engines and increased gross weight) and Model 24B, 24B-A, 24D, 24D-A, with unmodified wings, plus 5 percent.
c. Model 25, 25A, with unmodified wings, plus 4 percent.
d. Model 25, 25A, with unmodified wings with ECR 936, (AAK70-5) plus 7 percent.
e. Model 25B, 25C, with unmodified wings, plus 7 percent.
f. Model 23, 24, 24A, 24B, 24B-A, 24D, 24D-A, 25, 25A, 25B, 25C, with Howard/Raisbeck Mark II wings, plus 7 percent.
12. In Section IV, PERFORMANCE DATA, adjacent to the LANDING WEIGHT LIMITS CHART, add the following:
Reduce the LimitingWeight-Brake Energy landing weights as follows:
a. Model 23, 24, 24A, with unmodified wings, 800 lbs.
b. Model 23, 24, 24A, with ECR 736 (CJ610-6 engines and increased gross weight), and Model 24B, 24B-A, 24D, 24D-A with unmodified wings, 400 lbs.
c. Model 25, 25A, with unmodified wings, 300 lbs.
d. Model 25, 25A, with unmodified wings with ECR 936 (AAK70-5), 500 lbs.
e. Model 25B, 25C, with unmodified wings, 500 lbs.
f. Model 23, 24, 24A, 24B, 24B-A, 24D, 24D-A, 25, 25A, 25B, 25C, with Howard/Raisbeck Mark II wings, 500 lbs.
NOTE: 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 the identical revisions to the Airplane Flight Manual provided by the manufacturer and approved by the FAA. The temporary 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.
B) Except for the roll axis of the FC-200 autopilot installed on Model 35, 35A, 36 and 36A airplanes, within the next 75 flight hours, conduct the following inspections to assure capability of manually overriding the Automatic Flight Control Systems:
1. Energize the airplane electrical system by applying 28 VDC electrical power.
2. Roll Axis
a. On airplanes equipped with FC-110 autopilot, remove the electrical power from the FC-110 Autopilot Computer. Open the computer and identify the Roll Calibration Board. On the Roll Calibration Board, temporarily install, in parallel with R18 (82 ohm) resistor, a 39 ohm, one watt resistor. Restore the electrical power and engage the Autopilot with the control wheel centered and verify that the roll slip clutch breakaway occurs by rotating the control wheel briskly (45 degrees per second) in both directions. If slippage is not verified, remove the capstan and adjust to proper torque per the appropriate Gates Learjet Service Manual. Return Autopilot Computer to original configuration and accomplish a functional check of the autopilot.
3. Yaw Axis
a. Effective on all models:
(1) Check and adjust the yaw capstan slip clutch torque (primary and secondary where applicable) in accordance with the appropriate Gates Learjet Service Manual.
4. Pitch Axis
a. Effective on Models 24D, 24D-A, 24E, 24F, 24F-A, 25B, 25C, 25D, 25F, 28, 29, 35, 35A, 36 and 36A airplanes and airplanes incorporating Gates Learjet Kits AAK71-12 or AMK80-3 (torquers):
(1) With the Autopilot disengaged, turn on both stall warning switches and move the control wheel forward and aft at a rapid rate (one second - stop to stop). Note the drag associated with control movement. Turn off the stall warning switches and repeat the rapid fore and aft movement. Note the decrease in drag, which is an indication that the electric disconnect clutch functions properly by disconnecting the drag of the pitch servo (torquer) from the control system.
b. Effective on Models 23, 24, 24B, 24B-A, 24C, 25 and 25A airplanes except airplanes incorporating Gates Learjet Kits AAK71-12 or AMK80-3:
(1) Check and adjust the pitch capstan slip clutch for proper torque in accordance with the appropriate Gates Learjet Service Manual.
C) On airplane Models 35, 35A, 36 and 36A, within the next 150 flight hours conduct the following inspection of the FC-200 autopilot roll axis to assure capability of manually overriding that axis of Automatic Flight Control Systems:
1. Energize the airplane electrical system by applying 28 VDC electrical power.
2. Check andadjust the roll capstan slip clutch for proper torque in accordance with the appropriate Gates Learjet Service Manual.
D) Submit a written report of any out of tolerance roll, yaw, or pitch axis capstan slip torque to the Federal Aviation Administration (FAA), Aircraft Certification Program, Room 238, Terminal Building 2299, Mid-Continent Airport, Wichita, Kansas 67209. (Reporting approved by the Office of Management and Budget Order OMB No. 04-R0174.)
E) To assure proper operation of the Stall Warning Accelerometer Unit, perform, within the next 25 flight hours, inspection of the Stall Warning Accelerometer in accordance with appropriate Gates Learjet Service Bulletin SB 23, 24, 25-301A, SB 28, 29-27-3A, or SB 35, 36-27-12A. Submit a written report on any discrepancy discovered during this inspection to FAA, Aircraft Certification Program, Room 238, Terminal Building 2299, Mid-Continent Airport, Wichita, Kansas 67209. (Reporting approved by Office of Management and Budget Order OMB No. 04-R0174.)
NOTE: The owner/operator is responsible for submitting reports required by this AD.
F) Airplanes may be flown in accordance with FAR 21.197 to a location where alterations and inspections required by this AD can be accomplished.
G) Any equivalent method of compliance with this AD must be approved by the Manager, Aircraft Certification Program, FAA, Room 238, Terminal Building No. 2299, Mid-Continent Airport, Wichita, Kansas 67209. Telephone: (316) 942-4285.
H) On or before October 1, 1986, accomplish the requirements of paragraphs 1. or 2., below, on Learjet Models 23, 24, 24A, 24B, 24B-A, 24D, 24D-A, 25, 25A, 25B, 25C, with unmodified wings, at an FAA certificated maintenance repair station, and insert in the appropriate sections of the Airplane Flight Manual (AFM) the permanent AFM revision pertaining to procedures and performance associated with Airplane Modification Kit (AMK) 83-4 or 84-5. The limitations and performance information required paragraphs A)3., A)7., A)8., A)9., A)10., A)11., and A)12. of this AD are superseded by the AFM revision included with these kits.
1. Incorporate AMK 83-4 to improve airplane handling qualities and aerodynamic stall characteristics, or
2. Incorporate AMK 84-5 to make the stall prevention system (pusher) operation consistent with the airplane performance and limitations.
All persons affected by this proposal who have not already received these documents from the manufacturer may obtain copies upon request to the Gates Learjet Corporation, P.O. Box 7707, Wichita, Kansas 67277. This information may be examined at the FAA, Northwest Mountain Region, 17900 Pacific Highway South, Seattle, Washington, or at the FAA, Central Region, Room 100, 1801 Airport Road, Mid-Continent Airport, Wichita, Kansas.
This AD supersedes the airmail letter AD on the same subject issued August 4, 1980, and identified as AD 80-16-06.
Amendment 39-3932 became effective on October 9, 1980,to all persons except those to whom it has already been made effective by an airmail letter from the FAA dated September 4, 1980.
This amendment 39-5039 becomes effective May 20, 1985.
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