# AD 80-17-11: Airspeed Warning Placard

- Type: Airworthiness directive
- Status: Current
- Products: Learjet 35, 35A (C-21A), 36 and 36A
- Effective: August 28, 1980
- Superseded by: Nothing supersedes this AD
- Product type: Aircraft, Small/large airplane
- Amendment: 39-3888
- Registered aircraft: 211 may be affected, by airframe or engine model (OpenAirDocs)
- FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/368689A35402DE32862569880075C44C.0001
- DRS record last changed: May 30, 2024
- Page: https://openairdocs.org/ad/80-17-11

## The airworthiness directive

80-17-11 GATES LEARJET: Amendment 39-3888. Applies to the following model and serial number airplanes:

Model 35 Series Serial Number 35-050 through 35-339 except 35-054 and 35-065 Model 36 Series Serial Number 36-017 through 36-045

COMPLIANCE: Required as indicated unless already accomplished.

To prevent encountering a possible overload flight condition that could fail the forward engine mount, accomplish the following:

A) Within the next 75 hours time-in-service after the effective date of this AD, in accordance with Gates Learjet Corporation Service Bulletin 35/36-11-3, dated July 28, 1980:

1. Install airspeed warning placards and modify the Mach/overspeed switch circuit to effect a reduced maximum operating airspeed (VMO) of 307 KIAS, from sea level to 31,100 feet altitude.

2. Insert in the existing Airplane Flight Manual the temporary Airplane Flight Manual Supplement included in Service Bulletin 35/36-11-3.

B) Within the next 600 hours' time-in-service after the effective date of this AD, replace or re-age both forward engine mounts in accordance with Gates Learjet Corporation Airplane Modification Kit AMK 80-6. Accomplish the removal and installation of the engine mounts at authorized Gates Learjet Service Centers and the nondestructive testing and heat treating at appropriately rated FAA certified repair stations.

C) Upon compliance with Paragraph B above, the requirements of Paragraph A of this AD are no longer applicable.

D) Issuance of a Special Flight Permit in accordance with FAR 21.197 is permitted for the purpose of moving the affected airplanes to a location where the modifications required by this AD can be accomplished.

E) Any equivalent means of compliance with this AD must be approved by the Chief, Aircraft Certification Program, Federal Aviation Administration, Room 238, Terminal Building No. 2299, Mid-Continent Airport, Wichita, Kansas 67209.

This amendment becomes effective August 28, 1980.

## Affected data sheets (1) (OpenAirDocs)

The type certificate data sheets whose models the AD names.

- [TCDS A10CE](https://openairdocs.org/tcds/A10CE): Learjet Inc.; names 4 of 29 models: 35, 35A (C-21A), 36, 36A

## Registered aircraft it may apply to (OpenAirDocs)

Matched by airframe and engine model; the AD's applicability may narrow it by serial number, part number or equipment.

- Aircraft: 211 (211 by airframe model, 0 by engine model)
- Makers: Gates Learjet 136, Gates Lear Jet 50, Learjet 25

Models with the most aircraft:

- [Gates Learjet 35A](https://openairdocs.org/model/gates-learjet-35a): 135 aircraft (airframe model)
- [Learjet 35A](https://openairdocs.org/model/learjet-35a): 24 aircraft (airframe model)
- [Gates Lear Jet 36A](https://openairdocs.org/model/gates-lear-jet-36a): 21 aircraft (airframe model)
- [Gates Lear Jet 35](https://openairdocs.org/model/gates-lear-jet-35): 16 aircraft (airframe model)
- [Gates Lear Jet 36](https://openairdocs.org/model/gates-lear-jet-36): 13 aircraft (airframe model)
- [Learjet 35](https://openairdocs.org/model/learjet-35): 1 aircraft (airframe model)
- [Gates Learjet 35A (C-21A)](https://openairdocs.org/model/gates-learjet-35a-c-21a): 1 aircraft (airframe model)

All 8 models: https://openairdocs.org/ad/80-17-11/models.md
Every aircraft: https://openairdocs.org/ad/80-17-11/aircraft.md

Its text cites no advisory circulars or STCs.

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