My Personal Experience With Hoses
I purchased a 1968 Cessna172I in October 2009 from an individual in Illinois. Annuals were completed in 2007 and 2008 by shops in Illinois. As an A&P, I personally completed the annual in March 2010. During the annual inspection, it was discovered that all engine and fuel hoses in the engine compartment were the original hoses, dated 1968. I was very surprised by this discovery. In reviewing the previous aircraft logs, there were no entries of hoses being replaced. This indicates that hoses may have been overlooked during required annual or 100-hour inspections. During the annual inspection on my aircraft in 2010, all hoses were replaced, along with some oil-soaked fire sleeves. Surprisingly, the original hoses were in service as oil and fuel lines, undamaged and still somewhat pliable.
Careful inspection and replacement of hoses, as necessary, will reduce the risk of an inflight emergency. This article is aimed toward pilots’ and owners’ understanding of uses and applications of aircraft hoses in GA aircraft with reciprocating engines. Aircraft with turbine engines are not included in this discussion.
14 CFR, Part 43, Appendix A, Section (c), Preventive Maintenance (c21), (c22). Provides guidance for the owner/operator replacing hoses.
(c) 21 The owner/operator may replace any hose connection except hydraulic connections (brake hoses or hydraulic landing gear hoses).
(c) 22 The owner/operator may replace only prefabricated fuel lines.
The preventive maintenance described in (c 21) and (c 22) must be performed by the holder of at least a private pilot certificate issued under Part 61 who is the registered owner or co-owner of the aircraft and holds a certificate of competency for the aircraft.
Note: The written statements in FAA c21 and c22 above are a gray area and are not clearly defined. The statements are intended as guidance for an owner/operator. Any hose installed on an aircraft is a critical part of the aircraft and requires knowledge, experience, and special tools to deal with any issue with them. Replacing or repairing of any hose should be completed and signed off by a certificated A&P mechanic.
An aircraft logbook entry is required for all work completed on the aircraft.
The log entry includes:
- The date the work was completed.
- Description of the work completed.
- Description of the items repaired or replaced.
- Total airframe time when work was copleted.
- Signature of the person completing the work, including their FAA certificate number.
Types of Aircraft Hoses
Aircraft hoses are manufactured under the requirements of FAA TSO (Technical Standard Order), which is the Technical Standard for Materials, Processes, and Appliances used on all certified aircraft.
Aircraft hoses are covered under TSO C53a “Fuel and Oil System Hose Assemblies” and TSO C75 “Hydraulic Hose Assemblies.” Each TSO contains minimum performance standards for materials, parts, and processes for hose components used in aircraft.
Each TSO contains several types of hose, each of which has specific pressure ratings and operating temperatures.
Determining Hose Life
The FAA information regarding hose life is very limited and does not address in-service life of elastomeric hose. The only reference to hose is shown below.
Reference FAA AC43.13 -1B “Acceptable Methods, Techniques, and Practices — Inspection and Repair, Paragraph 6-73 PG 6-16
6-73. Flexible Hose Assemblies.
- Inspect hose assemblies for chafing, weather-checking, hardening, discoloration, evidence of fungus, torn weather protective coatings or sleeves, and corrosion of fittings.
- Replace any defective, damaged, twisted, or bulging hoses.
General interpretation: Replace the hose if any damage is found.
Service Life of Aircraft Hoses
MIL-STD-1523A, dated Sept. 1973, Paragraph 5.2, The maximum age for elastomeric hoses is 32 quarters (eight years) after the cure date, which is printed on the hose and engraved on the metal ID tag attached to the hose assembly.
Parker Aerospace Publication 106-SG1, “Safety Guide for Selecting and Using Parker Aerospace Hose, Fittings, and Related Accessories,” dated January 2010. This publication references FAA AC20-7A (cancelled) and SAE Aerospace Standard 1933, which states hose should not be placed in service after 32 quarters (eight years) after the cure date, which is printed on the hose and engraved on the metal ID tag attached to the hose assembly.
Inspection of Hoses “On Condition”
- Check the Aircraft Maintenance Manual or engine manufacturers manual for any requirements for hose replacement.
- Follow the recommendations of Parker Aerospace Publication 106-SG1 for conducting a visual inspection of all hose assemblies forward of the firewall.
- The Parker publication recommends immediate replacement of the hose assembly if any defects listed are found during the visual inspection.
Requirements for Fire Protection
The requirements for fire protection of fuel and oil hose assemblies are stated in 14 CFR, Part 33, Subpart C, 33.17 Fire Protection, (b)
(b) Each external line, fitting, and other component, which contains or conveys flammable fluid during normal engine operation, must be fire resistant or fireproof, as determined by the Administrator. Components must be shielded or located to safeguard against the ignition of leaking flammable fluid.
The fire sleeve is commonly used for fire protection on certificated aircraft. The fire sleeve is manufactured under FAA TSO C53a or TSO-C75. It also meets the specifications of SAE AS 1072f (latest revision). The fire sleeve will be identified with manufacturer, AS 1072 and will be sized in 1/16” increments. For example: -16 = 1” ID, -6 = 3/8” ID.
Fire Sleeve Inspection
Fire sleeve condition is critical to survivability of hose assemblies in case of engine compartment fire. Fire sleeves should be visually inspected for the following conditions and repaired or replaced immediately.
- Damaged or loose fire sleeve.
- Loose or damaged band clamp.
- Fire sleeve not covering the socket of the end fitting.
- Fire sleeve with an ID soaked with oil or fuel.