46-38-01: Vacuum System Tubing

FAA order 46-38-01 is an airworthiness directive. The FAA's subject line: Vacuum System Tubing. It names Grumman G-21: about 35 aircraft on the U.S. register today, though an order usually covers particular versions or serial numbers rather than every one. System: heating, ice protection and utility systems.

What it applies to as the FAA lists it

Kind of product: Aircraft
Makes: Grumman American Aviation Corporation
Models: G-21, G-21A (Army OA-9, Navy JRF-1, -2, -3, -4, -5, and -6B)
On this site: Grumman G-21 35 registered

Dates and paperwork

Docket: Unknown
Status: Current
The FAA's document: Read the order on the FAA's site

The order itself the regulatory text, as published

Show the full text (715 characters)

46-38-01   GRUMMAN:  (Was Mandatory Note 4 of AD-654-1.)  Applies to G-21 and G- 21A Aircraft. 

	Compliance required prior to November 1, 1946. 

	Reroute to vacuum system tubing in the engine compartments to prevent raw fuel from lodging in the check valve, thus deteriorating the valve and possible seeping through.  The flap system storage tank should be inspected and if fuel is found it should be thoroughly flushed.  The check valves in the vacuum system are to be removed and inspected for wear and deterioration. Presence of fuel in the flap system storage tank is sufficient cause for the replacement of the check valves. 

	(Grumman Service Bulletin No. 19 dated July 18, 1946, covers this same subject.)

Source: FAA Dynamic Regulatory System, airworthiness directives. The FAA's document is the authority; the register counts are this site's, from the FAA register of November 6, 2026. Connections as data: /graph/directive/46-38-01.json · aircraft systems.