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61-21-03: Hydraulic Fluid Gage

FAA order 61-21-03 is an airworthiness directive in force since October 13, 1961. The FAA's subject line: Hydraulic Fluid Gage. It names Douglas DC-8: about 6 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
The Boeing Company
Models
DC-8-11, DC-8-12, DC-8-21, DC-8-31, DC-8-32, DC-8-33, DC-8-41, DC-8-42, DC-8-43, DC-8-51, DC-8-52, DC-8-53, DC-8-55, DC-8-61, DC-8-61F, DC-8-62, DC-8-62F, DC-8-63, DC-8-63F, DC-8-71, DC-8-71F, DC-8-72, DC-8-72F, DC-8-73, DC-8-73F, DC-8F-54, DC-8F-55
On this site
Douglas DC-8 6 registered

Dates and paperwork

In force since
October 13, 1961
Published
October 13, 1961
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 (1,602 characters)
61-21-03 DOUGLAS: Amdt. 346 Part 507 Federal Register October 13, 1961. Applies to All DC-8 Series Aircraft. \n\n\tCompliance required within the next 150 hours' time in service after the effective date of this AD. \n\n\tAs a result of recent incidents which have shown the need for effective quantity indication of "reserve" hydraulic fluid in the system reservoir, the following must be accomplished: \n\n\tUnless already accomplished in accordance with FAA approved technical data, replace or modify in accordance with Douglas Service Bulletin No. DC-8 A29-40 (Reissue No. 1 or later) or FAA approved equivalent, the existing hydraulic quantity gage in the cockpit and the quantity transmitter in the fluid reservoir, to provide a system which will indicate the quantity of reserve hydraulic fluid in the reservoir down to approximately one gallon. The system indication error shall not exceed 10 percent. The dial on the quantity gage shall be marked in a manner which divides the total indicator range into three segments and identifies the three segments, as follows: \n\n\nSegment\nReserve Fluid Quantity in Reservoir\nNORMAL\nFull (11.5 gal.) to 4.9 gal.\nAUX.\n4.9 gal. to 1.5 gal.\nEMER.\n1.5 gal. to approx. 1.0 gal.\n\t\n\tThe exact quantities in gallons need not be marked on the quality indicator. "EMER." need not be shown provided that this segment is otherwise marked in a manner distinctly different from the other segments. \n\n\t(Douglas Service Bulletin No. DC-8 A29-40 (Reissue No. 1 or later) pertains to this same subject.) \n\n\tThis directive effective October 13, 1961.

Related safety bulletins advice on the same designs, not orders

2019-02-19NE-19-03 · Escape Slide Maintenance Tasks and Intervals - JASC 2565
2014-11-24NM-15-03 · Flight Controls
2008-12-11NM-09-03 · Engine Fuel and Control - Implementing Fuel Tank System Airworthiness Limitations
2006-07-27NM-06-57 · Reports of damage to airplanes and to property on the ground caused by blue or clear ice falling from airplanes.

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/61-21-03.json · aircraft systems.