# AD 68-21-04: Ice Damage to Engine

- Type: Airworthiness directive
- Status: Current
- Products: Textron 65-90, 65-A90, 65-A90-1 and B90
- Effective: October 17, 1968
- Superseded by: Nothing supersedes this AD
- Product type: Aircraft, Small airplane
- Amendment: 39-668
- Registered aircraft: 161 may be affected, by airframe or engine model (OpenAirDocs)
- FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/098A3817BA59C46186256A08006C48DA.0001
- DRS record last changed: January 21, 2026
- Page: https://openairdocs.org/ad/68-21-04

## The airworthiness directive

68-21-04 BEECHCRAFT: Amendment 39-668. Applies to Models 65-90, 65-A90 and 65-B90 aircraft (Serial Numbers LJ-1 through LJ-406) and 65-A90-1 aircraft (Serial Numbers LM-1 through LM-129).

Compliance required as indicated.

To reduce the possibility of engine damage and malfunction while operating in icing conditions above 15,000 feet MSL, within one year after the effective date of this Airworthiness Directive, unless already accomplished, accomplish the following:

      (A) Install seal strips and a spring lockdown assembly on the Inertial Separator Vane and an automatic ignition (re-light) system in accordance with the method outlined in Beechcraft Service Instructions #0115-010 dated October 1, 1968.

      (B) Equip the airplane with the applicable FAA Flight Manual as set forth in Beechcraft Service Instructions #0115-010 dated October 1, 1968.

      (C) The Emergency Order Amending Type Certificate No. 3A20 dated May 24, 1968, as amended September 19, 1968, shall remainin force and effect as to each individual aircraft covered by this Airworthiness Directive until paragraphs (A) and (B) have been accomplished.

This amendment becomes effective October 17, 1968.

## Affected data sheets (1) (OpenAirDocs)

The type certificate data sheets whose models the AD names.

- [TCDS 3A20](https://openairdocs.org/tcds/3A20): Textron Aviation Inc.; names 4 of 22 models: B90, 65-A90-1, 65-A90, 65-90

## 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: 161 (161 by airframe model, 0 by engine model)
- Makers: Beech 161

Models with the most aircraft:

- [Beech 65-A90-1](https://openairdocs.org/model/beech-65-a90-1): 90 aircraft (airframe model)
- [Beech 65-A90](https://openairdocs.org/model/beech-65-a90): 34 aircraft (airframe model)
- [Beech B90](https://openairdocs.org/model/beech-b90): 29 aircraft (airframe model)
- [Beech 65-90](https://openairdocs.org/model/beech-65-90): 7 aircraft (airframe model)
- [Beech 65-A90-1 (U-21A)](https://openairdocs.org/model/beech-65-a90-1-u-21a): 1 aircraft (airframe model)

All 5 models: https://openairdocs.org/ad/68-21-04/models.md
Every aircraft: https://openairdocs.org/ad/68-21-04/aircraft.md

Its text cites no advisory circulars or STCs.

---
OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.