# AD 64-06-01: Cabin Heater/Muffler Weld Assembly

- Type: Airworthiness directive
- Status: Current
- Products: Textron 23
- Effective: March 17, 1964
- Published: March 11, 1964
- Superseded by: Nothing supersedes this AD
- Product type: Aircraft, Small airplane
- Registered aircraft: 147 may be affected, by airframe or engine model (OpenAirDocs)
- FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/C95021119A2255DB86256A08007236B3.0001
- DRS record last changed: January 21, 2026
- Page: https://openairdocs.org/ad/64-06-01

## The airworthiness directive

64-06-01 BEECH: Amdt. 703 Part 507 Federal Register March 11, 1964. Applies to All Model 23 Aircraft Prior to Serial Number M-555 Except Serial Number M-1.

Compliance required within 10 hours' time in service after the effective date of this AD, unless already accomplished.

Failures of the cabin heater/muffler weld assembly, Beech P/N 169-950010-21, have occurred. Such failures can cause hazardous quantities of carbon monoxide to enter the cabin when cabin heat is used. To preclude carbon monoxide contamination of cabin air, accomplish either of the following:

  (a) Install a stainless steel dam around the exhaust tube between the muffler assembly and heater shroud assembly in accordance with Beechcraft Service Bulletin No. 64-1 dated January 13, 1964; or

  (b) Render the cabin heat and windshield defrost system inoperative by positively securing in the closed position the sliding doors of both the cabin heat and the defrost valves in the airplane firewall.

This directive effective March 17, 1964.

## Affected data sheets (1) (OpenAirDocs)

The type certificate data sheets whose models the AD names.

- [TCDS A1CE](https://openairdocs.org/tcds/A1CE): Textron Aviation Inc.; names 1 of 14 models: 23

## 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: 147 (147 by airframe model, 0 by engine model)
- Makers: Beech 147

Models with the most aircraft:

- [Beech 23](https://openairdocs.org/model/beech-23): 147 aircraft (airframe model)

All 1 models: https://openairdocs.org/ad/64-06-01/models.md
Every aircraft: https://openairdocs.org/ad/64-06-01/aircraft.md

Its text cites no advisory circulars or STCs.

## NTSB investigations that cite this AD (1)

From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model.

- [NTSB CHI01FA052](https://openairdocs.org/ntsb/CHI01FA052), Dec 18, 2000: Beech BE-23 (N2324J), Rolla, MO, destroyed, 1 fatal. Probable cause: The pilot's inadequate preflight during the pre-buy inspection, the pilot's incapacitation due to carbon monoxide, and the fractured muffler.

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