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Hydrostatic Testing And Requalification Requirements

March 2020

20200302_095308Hydrostatic testing is often required at certain intervals for aircraft oxygen cylinders, fire extinguishers and pneumatic bottles. The interval at which these are due and what is to be done is sometimes confusing.

Some aircraft maintenance schedules require hydrostatic testing at five years while others at 10 years, and some reference all the back to the DOT (Department Of Transportation) specification for the interval.

PLEASE NOTE: While these cylinders, extinguishers, and bottles are installed on the aircraft, the aircraft schedule takes precedence over the DOT requirements. 

Valve Inspection

It’s not only important to know when these are due but also what is to be done. Many units have valves attached that also require maintenance to be performed during the hydrostatic test. This could be anything from a function test up to a complete overhaul. To comply with the scheduled task, all of the requirements must be met.

DOT Certified and FAA Certified

There are a lot of DOT-Certified hydrostatic testing facilities but not all of them are FAA-Certified 145 repair stations. Since units installed on an aircraft are both FAA-Certified as well as DOT certified, it is best to use a vendor that has both certifications, like Duncan Aviation. Be sure to communicate with your chosen vendor what your expectations are and what maintenance is required.


When you receive your units back, double check the paperwork that is returned to ensure all tasks were completed. At a minimum you should receive an FAA 8130-3 for the assembly and a DOT Certificate of Conformance for the hydrostatic test. The Hydrostatic test is covered by 49 CFR and not 14 CFR; there for it should not be documented on FAA 8130-3. In addition, you may have an 8130-3 for the valves or other associated equipment requiring maintenance.

If the aircraft scheduled maintenance does not list an interval for Hydrostatic test, the 49 CFR 180.209 details the DOT required interval.

Specification under which
cylinder was made

Minimum test pressure

Requalification period


3000 psig



5/3 times service pressure, except noncorrosive service (see §180.209(g))

5, 10, or 12 (see §180.209(b), (e), (f), (h), and (j).


5/3 times service pressure

5, 10 or 12 (see §180.209(e), (j) and §180.209(m)3).


5/3 times service pressure

5, 10 (see §180.209(e).

3B, 3BN

2 times service pressure (see §180.209(g))

5 or 10 (see §180.209(e), (f)).


Test not required.



5/3 times service pressure

3 (see §§180.209(k) and 180.213(c)).


5/3 times service pressure



2 times service pressure (see §180.209(g))

5 or 10 (see §180.209(e) or (h)).

4B, 4BA, 4BW, 4B-240ET

2 times service pressure, except non-corrosive service (see §180.209(g))

5, 10, or 12 (see §180.209(e), (f), and (j)).

4D, 4DA, 4DS

2 times service



2 times service pressure, except non-corrosive (see §180.209(g))

5 or 10 (see §180.209(e)).


Test not required.


8, 8AL


10 or 20 (see §180.209(i)).

Exemption or special permit cylinder

See current exemption or special permit

See current exemption or special permit.

Foreign cylinder (see §173.301(j) of this subchapter for restrictions on use)

As marked on cylinder, but not less than 5/3 of any service or working pressure marking

5 (see §§180.209(l) and 180.213(d)(2)).


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