Servicing an Air/Oil Shock Strut for the A&P Practical

October 20, 2026 · Primary sources checked October 20, 2026

For the Airframe and Powerplant (A&P) oral and practical (O&P), this A&P practical shock strut servicing guide separates pressure release, fluid level, valve installation, and inflation. Use this guide alongside supervised hands-on work as you prepare to discuss the assigned procedure.

What does this O&P project evaluate?

For this strut rehearsal, read the Federal Aviation Administration (FAA) Airman Certification Standards (ACS) skills listed below.

A practical project pairs one skill with two practical questions.

FAA Order 8900.1, Vol. 5, Ch. 5, Sec. 11, CHG 929, printed 16, PDF 16, 5-5-11-7C3)c)

The references available for the project may also be used to answer its practical questions.

FAA Order 8900.1, Vol. 5, Ch. 5, Sec. 11, CHG 929, printed 16, PDF 16, 5-5-11-7C3)c)

The project receives a pass or fail result.

FAA Order 8900.1, Vol. 5, Ch. 5, Sec. 11, CHG 929, printed 16, PDF 16, 5-5-11-7C3)f)

To pass that project, you must demonstrate the skill successfully on the first attempt and answer both questions successfully.

FAA Order 8900.1, Vol. 5, Ch. 5, Sec. 11, CHG 929, printed 16, PDF 16, 5-5-11-7C3)f)

You must complete the project to the required performance standard to pass, and the examiner can find that standard in the downloaded test. The Mechanic Test Generator (MTG) FAQ says each practical project stands alone.

FAA Order 8900.1, Vol. 5, Ch. 5, Sec. 11, CHG 929, printed 16, PDF 16, 5-5-11-7C3)g) · FAA Mechanic Test Generator FAQs, updated May 22, 2023, unnumbered page, PDF 4

The FAA sample marks its example projects as practice material only. Our study advice: rehearse the service sequence against the assigned strut’s instructions.

FAA sample oral and practical test, unnumbered page, PDF 6

FAA-S-ACS-1, printed 26, PDF 31 · FAA-S-ACS-1, printed 27, PDF 32

Find the instructions before releasing pressure

The instruction plate on the strut specifies the hydraulic fluid type and inflation pressure. The handbook calls it of utmost importance to become familiar with those instructions before adding fluid or inflating the strut with air or nitrogen.

FAA-H-8083-31B, Airframe, printed 13-10, PDF 741

Our preparation advice: use the current manufacturer procedure and any required approved data for the assigned strut; the following sequence is a handbook example, not a universal service instruction.

Risks to control before strut servicing

The ACS safety appendix lists use of current maintenance and overhaul publications and procedures among the safety precautions the evaluator ensures you follow.

FAA-S-ACS-1, printed A-3, PDF 67

Observation of safety precautions includes wearing safety glasses, hearing protection, and any other required personal protective equipment (PPE).

FAA-S-ACS-1, printed A-3, PDF 67

Disregarding safety will cause a failed result. For a project action that would jeopardize safety, the evaluator will ask for that portion to be simulated.

FAA-S-ACS-1, printed A-3, PDF 67

• The ACS identifies high-pressure fluids and gases, storage and handling of hydraulic fluids, aircraft jacks, and high-pressure strut disassembly as landing-gear risks.
• The handbook warns that deflating a shock strut can be a dangerous operation. The technician must be thoroughly familiar with the high-pressure service valve’s operation before deflating the strut.
• Follow the manufacturer’s deflation technique and all necessary safety precautions.
• Keep people, work stands, and other obstructions clear of the aircraft.
• Securely jack the aircraft if the maintenance procedure requires it.
• Jacks should always be placed under the prescribed points.

FAA-H-8083-31B, Airframe, printed 13-10, PDF 741 · FAA-S-ACS-1, printed 26, PDF 31, AM.II.E.R2–R5 · FAA-H-8083-31B, Airframe, printed 13-12, PDF 743

• Always wear the proper gloves and eye protection when handling hydraulic fluid.
• A respirator capable of removing organic vapors and mists must be worn when phosphate ester mist or vapor exposure is possible.
• Repeated or prolonged phosphate ester exposure may dry the skin and, if unattended, could lead to dermatitis or secondary infection.
• Ingestion of hydraulic fluid should be avoided.
• Our setup advice: check the fluid’s Safety Data Sheet (SDS), spill controls, and exposure response before servicing.

FAA-H-8083-31B, Airframe, printed 12-5, PDF 684

• Replace an unsafe air hose immediately after inspection reveals breaks or worn spots.
• Keep compressed-air connections free of leaks.
• Never use compressed air to clean hands or clothing; pressure can force debris into the flesh, leading to infection.
• Never spray compressed air toward other personnel.
• Coil and store unused air hoses properly after straightening them.

FAA-H-8083-30B, General, printed 1-2, PDF 23

For any significant amount swallowed, the handbook says it should be tested in accordance with the manufacturer’s direction, followed with hospital-supervised stomach treatment.

FAA-H-8083-31B, Airframe, printed 12-5, PDF 684

Release all air before removing the core or valve

In the handbook’s typical sequence, the aircraft starts with the struts in their normal ground position. Remove the servicing-valve cap and check the swivel nut for tightness.

FAA-H-8083-31B, Airframe, printed 13-12, PDF 743, steps 1–3

For a core-equipped valve, first depress the core to release pressure trapped under it in the valve body. Always stand to the side of a possible valve-core trajectory. A core propelled by strut pressure could cause serious injury. In the handbook’s valve examples, the core-type valve is rated to 3,000 pounds per square inch (psi), but the core itself is only rated to 2,000 psi; the core-free valve is rated to 5,000 psi.

FAA-H-8083-31B, Airframe, printed 13-12, PDF 743

Next, loosen the swivel nut: for a valve with a valve core, the handbook says to rotate the swivel nut one turn counterclockwise and then depress the valve core with a tool designed for the purpose to release all of the air in the strut. For the core-free valve in the example, loosen the swivel nut sufficiently to let the air escape. After all air has escaped, the strut should be compressed completely. An aircraft on jacks may need an exerciser jack under the lower strut to achieve full compression. Only after all air has been released and the strut compressed does the example remove the valve core with a valve core removal tool and then unscrew the entire service valve from the strut.

FAA-H-8083-31B, Airframe, printed 13-12, PDF 743 · FAA-H-8083-31B, Airframe, printed 13-12–13-13, PDF 743, 744

Set fluid level, reinstall the valve, and inflate

The example fills the compressed strut to the service-valve port with approved hydraulic fluid. The example then reinstalls the air service valve assembly with a new O-ring packing and torques it according to the applicable manufacturer’s specifications. The core-equipped valve in that sequence receives a new core.

FAA-H-8083-31B, Airframe, printed 13-13, PDF 744

A threaded fitting from a controlled high-pressure air or nitrogen source should be screwed onto the servicing valve. Use the service-valve swivel nut to control flow. On some struts, the correct amount of inflation is measured in psi; other manufacturers specify inflating until the lower strut extends to a certain measurement. Follow the manufacturer’s instructions. Struts should always be inflated slowly to avoid excess heating and overinflation.

FAA-H-8083-31B, Airframe, printed 13-13, PDF 744

After inflation, tighten the swivel nut and apply the specified torque. Remove the fill-hose fitting and finger-tighten the valve cap.

FAA-H-8083-31B, Airframe, printed 13-13, PDF 744

If the assigned service includes bleeding the strut

Air trapped in the hydraulic fluid may make bleeding necessary. The handbook’s bleeding example uses a bleed hose with a fitting that makes an airtight connection at the service valve port, long enough to reach the ground while the aircraft is on jacks. The aircraft is jacked until the shock struts are fully extended. Any air pressure in the strut is released before the air service valve is removed, and the strut is filled to the level of the service port with approved hydraulic fluid. With the bleed hose attached to the service port, its free end goes into a container of clean hydraulic fluid, and the hose end must remain below the surface of the fluid.

FAA-H-8083-31B, Airframe, printed 13-14, PDF 745

With an exerciser jack or other suitable jack under the shock strut jacking point, compress and extend the strut fully by raising and lowering the jack. Compress the strut slowly and let it extend by its own weight. Continue until bubbles stop forming, and verify the appropriate fluid level before the next step. The example then removes the jacks, removes the bleed hose, and installs, torques, and inflates the service valve to manufacturer specifications.

FAA-H-8083-31B, Airframe, printed 13-14, PDF 745

Common mistakes to catch in rehearsal

Our review checklist: distinguish pressure trapped under a core from the pressure stored in the strut; keep clear of the core trajectory; verify full pressure release before either core or valve removal; use the specified fluid, level, valve parts, torque, and inflation target.

Practice the oral explanation separately

DMEReady provides an artificial intelligence (AI) voice examiner for oral A&P rehearsal in a phone or computer browser. The AI asks follow-up questions in the style of a Designated Mechanic Examiner (DME). This is oral rehearsal, not hands-on practical training. Your first drill is free and requires no sign-up. DMEReady is an AI examiner, not a human DME, and it is independent and not affiliated with or endorsed by the FAA.

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Related guides

• Landing Gear Oral Exam Questions and Answers
• Hydraulic and Pneumatic Systems Oral Exam Questions and Answers
• A&P Practical Projects: What the DME Evaluates on the O&P
• Aircraft Tire and Wheel Inspection for the A&P Practical
• Bleeding Hydraulic Brakes for the A&P Practical

Sources

Primary sources checked October 20, 2026.

• FAA-S-ACS-1
• FAA-H-8083-31B, Airframe
• FAA-H-8083-30B, General
• FAA Mechanic Test Generator FAQs, updated May 22, 2023
• FAA Order 8900.1, Vol. 5, Ch. 5, Sec. 11, CHG 929
• FAA sample oral and practical test

About this guide: drafted with AI from the FAA sources listed on this page and checked claim by claim against them. Not reviewed by an A&P mechanic or DME. How we make our guides