Service Memo No. 4
Piper PA-14 Family Cruiser · Systems Description
Overview
This Service Memo No. 4 provides critical information regarding the brake and oleo strut system fluid usage for various Piper aircraft, including the Piper PA-14 Family Cruiser. It outlines the types of brake fluids compatible with different models and emphasizes the importance of using the correct fluid to avoid damage to the brake expander tubes. The memo also includes identification markings for fluid compatibility and recommendations for maintenance practices. This document is essential for maintenance personnel and pilots to ensure the safe operation of the aircraft's braking system.
- Use Lockheed #21 fluid (blue) for pre-1942 models with brakes; Univis #40 fluid (red or amber) for models from 1942 onwards.
- Identification markings on expander tubes are crucial: red for mineral/petroleum fluids, blue for vegetable fluids.
- Unmarked tubes should be treated as compatible with Lockheed #21 fluid to avoid damage.
- Master cylinders may have synthetic rubber cups requiring Univis #40 fluid; ensure compatibility before use.
- Using the wrong fluid can damage brake expander tubes, leading to safety hazards.
Document
Source
Originally published by www.univair.com. Sprinkle hosts a reference copy with an added summary, specifications and searchable full text.
Document details
- Type
- Systems Description
- Pages
- 2
- File size
- 121 KB
- Publisher
- www.univair.com
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In this document
Brake Fluid Recommendations
The memo specifies that Lockheed #21 (blue) fluid is recommended for airplanes built with brakes as standard equipment through 1941, while Univis #40 (red or amber) fluid has been used from 1942 onwards. It is crucial to continue using the same type of fluid that has been previously used to prevent damage to the brake system.
Fluid Identification Markings
Identification markings on expander tubes are critical for determining the appropriate fluid to use. Tubes with a red stripe are suitable for mineral or petroleum base fluids, while those with a blue stripe are for vegetable base fluids. Tubes without markings should be treated as compatible with Lockheed #21 fluid.
Master Cylinder Fluid Compatibility
The memo notes that brake master cylinders may have either natural or synthetic rubber cups. Since natural rubber cups have not been used since 1941, it is assumed that synthetic cups are in place, which require the use of Univis #40 fluid. This highlights the importance of using the correct fluid to maintain system integrity.
Safety notes
- Using the incorrect brake fluid can cause damage to the brake expander tubes.
- Always verify the type of fluid used in the system to prevent operational failures.
Full document text
SERVICE MEMO Service Memo No. 4 BRAKE AND OLEO STRUT SYSTEM FLUID USAGE NOTICE: The table below shows the type of brake fluid used in airplanes manufactured by the Piper Aircraft Corporation, however, due to airplanes being manufactured both with and without brakes and field installation and conversions being made to different type brake units, we recommend that if blue fluid (which has a vegetable or castor oil base), has been used in the system, it is safer to continue its use, to avoid the possibility of damage to the brake expander tubes, which will occur if red or amber fluid (mineral or petroleum base) is used with an expander tube not intended for this type of fluid. (See below for identification markings of different types of expander tubes.) Army Navy Fluid Fluid Name Model Designation Designati::m Brake System Oleo Struts Cou12e [4 L4-D None • Houdaille Trainer [3 L4-A, B, H, l NE-1 ** None Trainer PA-ll None None •• None Vag!!bond PA-15 None None ** None Vag<! bond PA-17 None None ** None Cruiser [5 None None * None Cruiser 5-C None AE-1 •• None Su12er Cruiser PA-12 None None •• None Family Cruiser PA-14 None None •• None Su12er Cub PA-18 -18A None None ** None Pacer - Tri -Pacer PA-20-22 None None •• ** AJ2ache PA-23 None None •• ** BRAKE FLUID OLEO FLUID • Lockheed #21 (Color-blue) Piper No. (Qt.) -750 209, (Gal.)-750 210 Qt. Piper No. 750 212 ** Univis #40 (Co1or-red)(or amber) Piper No. (Qt. )-750 874, (Gal. )-750 875 Gal. Piper No. 750 213 SPECIAL REMARKS: -DRY OR FLUSHED SYSTEM * Our records show Lockheed #21 fluid used in all airplanes built with brakes as standard equipment through 1941. ** Our records show Univis #40 fluid used approximately from 1942 on. Service Memo No. 4 - continued Brake master cylinders, (other than the Scott Model B-711 single unit type for which either mineral or petroleum base fluid is recommended), could have either natural or synthetic rubber cups. However, since the natural rubber cups have been extinct since 1941, it is assumed that they have been replaced with synthetic cups which would require the use of Univis #40 fluid. Considering the above, plus the fact that master cylinder cups are less expensive than are expander tubes, it is suggested that fluid recommended for use with the expander tubes be used in unmarked expander tubes, or those bearing blue identification explained below. BRAKE SHOE -EXPANDER TUBE FLUID IDENTIFICATION MARKING According to information received from the B. F. Goodrich Company, manufacturer of the expander tubes, approximately November 1943 all expander tubes were painted with a red or blue stripe on the 0. D. directly over the nozzle. The red stripe signified tubes suitable for use with mineral or petroleum base fluid, or Univis #40, and the blue stripe signified tubes suitable for use with vegetable base or Lockheed #21 fluid. Lockheed #21 fluid, only, should be used with natural rubber expander tubes. Tubes that do not have any painted stripes on the 0. D. should be used with Lockheed #21 to be safe. Approximately January 1, 1945, a silver stripe was added to show that the tube was suitable for operation down to -65° F., and could be used with mineral or petroleum base fluid to specification AN-VV0-866 (Univis #40).