AD 80-19-09 R1

80-19-09 R1 GATES LEARJET: Amendment 39-3913 as amended by Amendment 39-3998. Applies to the following Model 23, 24, 25, 28, 29, 35 and 36 series airplanes certificated in all categories:

Model Serial Numbers *23 (equipped with jet pumps) 23-003 thru 23-099 24 24-100 thru 24-357 25 25-003 thru 25-319 28 28-001 thru 28-005 29 29-001 and 29-002 35 35-001 thru 35-348 36 36-001 thru 36-045 *NOTE: Model 23 airplanes were not equipped with jet pumps when manufactured. Model 23 airplanes which have been retrofitted with jet pumps in the field will be so identified on the title page of the Airplane Flight Manual.

COMPLIANCE: Required as indicated unless already accomplished.

To reduce the possibility of fuel contamination and/or the presence of ignition sources in the tailcone service area, accomplish the following:

A) Within the next 25 hours time-in-service after May 8, 1980:

1. Run each engine to takeoff thrust momentarily, shut downand immediately open the access cover under the tailcone service area and make the following visual inspections:

a. Inspect the fuel and hydraulic system components for deterioration or damage, leakage and stains indicating leakage, paying particular attention to the exterior of the P/N AV16E1182 motive flow shutoff valves.

b. Inspect the batteries and electrical equipment for deterioration or damage and conditions which may cause arcing.

c. Inspect all vents and drains for obstruction or blockage.

d. Before further flight, correct any of the above-noted unsatisfactory conditions. Do not disassemble or reassemble motive flow shutoff valves in the field. Replace leaking valves with a new or factory rebuilt part.

2. Remove the Temporary Airplane Flight Manual Supplement, included in AD 80-09-06 as Figure 1, in the existing Airplane Flight Manual and in place thereof, install Temporary Airplane Flight Manual Supplement, included in this AD as Figure 1A, and comply with its instructions.

B) On or before February 13, 1981, install Gates Learjet motive flow valve shrouds and drain lines per Modification Kit No. AMK 80-7. After accomplishing this modification, remove the Temporary Airplane Flight Manual Supplement required by Paragraph A)2.

C) Airplanes may be flown in accordance with FAR 21.197 to a location where the provisions of this AD can be accomplished.

D) Any equivalent method of compliance with this AD must be approved by the Chief, Aircraft Certification Program Office, Room 238, Terminal Building 2299, Mid-Continent Airport, Wichita, Kansas 67209; Telephone (316) 942-4285.

This AD supersedes AD 80-09-06, Amendment 39-3764. Amendment 39-3913 became effective September 15, 1980. This amendment 39-3998 becomes effective December 11, 1980.

FIGURE 1A TEMPORARY AIRPLANE FLIGHT MANUAL SUPPLEMENT FOR GATES LEARJET MODELS 23, 24, 25 , 28, 29, 35 AND 36 SERIES AIRPLANES

(AD 80-19-09 requires this supplement to remain in the below designated Airplane Flight Manual until replaced by an equivalent Gates Learjet Company Flight Manual Supplement.)

Model ________ N ________ S/N ________

In addition to the presently specified post-flight procedures, immediately after the engines are shut down, open the access cover under the tailcone service area and accomplish the following, using a flashlight or supplemental light as necessary for adequate illumination.

1. Check the motive flow valves for leaks or stains indicating leaks.

2. Check all vents and drains to assure that they are clean and free from obstruction.

3. Any leaking motive flow valve must be replaced with a new or factory rebuilt part prior to further flight.

4. Secure access cover.