Practical Project Stations — ACS Task Performance
Objective. Learners will safely and correctly perform hands-on maintenance tasks drawn from the FAA Airframe and Powerplant ACS practical task lists, completing all required maintenance record entries to airworthy standards.
This lesson, its worked examples and its practice questions has not yet been verified by a certified examiner or master technician in the trade or by a certification or approval body. It is a study draft and may contain errors. Do not use it as instructions for work on a job site or on live equipment. Always follow your instructor, your supervising professional, and current official references and regulations.
VoTechWorks program approval and accreditation are still in progress. Credentials are issued only by the certifying bodies named in each program, after their own exams.
Purpose of ACS Practical Project Stations
The FAA Airman Certification Standards (ACS) for the Aviation Mechanic certificate define exactly what a Designated Mechanic Examiner (DME) will ask you to do and the standards you must meet. These lab stations replicate that environment before your actual practical test. Every station is built around a real ACS task reference so you practice the same sequence — identify the job, gather the data, perform the work safely, and document it correctly — that you will repeat on test day.
Safety First: Pre-Task Requirements
Before touching any aircraft system or component, complete these steps every time.
- Assess the hazard. Identify energy sources (electrical, hydraulic, pneumatic, spring-loaded) and chemical hazards (fuel, hydraulic fluid, cleaning solvents).
- Apply Lockout/Tagout (LOTO). Any maintenance that exposes you to unexpected energy release requires LOTO per established procedure. Verify that energy is isolated before beginning work.
- Select PPE for the task. Safety glasses are minimum at every station. Add hearing protection when operating rivet guns or running engine trainers. Wear chemical-resistant gloves when handling hydraulic fluid, fuel, or solvents. Never substitute one type of glove for another without checking chemical compatibility.
- Clear the work area. Remove tools, hardware, and rags from the work surface and verify no FOD (foreign object debris) is left in an open assembly.
- Have the correct manual open. You must work from the applicable manufacturer maintenance manual (AMM) or Instructions for Continued Airworthiness (ICA). Doing a task from memory alone is not acceptable practice and is not acceptable to a DME.
Rotating Through the Stations
Each station card lists the ACS task reference, the tools required, the manual and page you must use, and the pass/fail criteria an instructor will apply. Work independently. When you believe the task is complete and the work area is safe, call the instructor or qualified evaluator for the go/no-go assessment. Do not move to documentation until the physical work is accepted.
Sheet metal repair and inspection: Select the correct rivet type, diameter, and material per the AMM or FAA-H-8083-31. Drill, countersink or dimple as required, drive rivets without head cracks or die marks, and inspect the finished repair. Rivet spacing and edge distance must meet the applicable data.
Control cable rigging and tension measurement: After rigging, use a calibrated tensiometer (cable tension meter) and the correct adapter for cable diameter. Read tension at the mid-span of the cable away from pulleys. Compare the reading to the placard or manual value corrected for ambient temperature using the chart supplied. Re-rig if out of tolerance.
Compression test (reciprocating engine cylinder): Use a differential compression tester. Apply shop air to the approved pressure. Measure the differential between input and cylinder pressure. Know the general guidance that a significant pressure drop indicates leakage, and note where the air escapes (intake, exhaust, or crankcase) to identify the failed component. Record actual readings.
Magneto timing check: Use a timing light or buzz-box method per the AMM. Identify the correct crankshaft position (usually top dead center or the specified advance position) using the timing marks. Verify internal and external timing. Incorrect ignition timing is a safety-of-flight critical item; any error here results in immediate station failure.
Spark plug inspection and gapping: Clean plugs per the manufacturer's procedure. Inspect electrodes for erosion, lead fouling, and cracked insulators. Set the gap with a wire-type gap gauge to the dimension in the AMM. Install plugs to the correct torque using a calibrated torque wrench; overtorquing damages cylinder threads, a safety-critical error.
Hydraulic system servicing: Identify the correct fluid type from the aircraft data plate or AMM — mixing incompatible fluids destroys seals. Wear chemical-resistant gloves. Service to the indicated level. Inspect for leaks after servicing. Depressurize the system per LOTO procedure before opening any hydraulic line.
Landing gear operational check: Follow the AMM sequence exactly. Verify gear-down and gear-up indicator lights, retraction time if specified, and door sequencing. Never place any part of your body in the path of moving gear components during an operational check.
Maintenance Record Entries
After every completed station task you write either a logbook entry or a simulated FAA Form 337 entry, depending on the type of work. Every entry must contain:
1. Date of work and aircraft registration (or trainer identifier).
2. Description of work performed — specific, not vague.
3. Data used: manual title, revision level, and page or figure number.
4. Part numbers and material specifications for any part installed.
5. Return-to-service statement referencing 14 CFR Part 43.
6. Mechanic's name, certificate number, and signature.
An incomplete entry is a regulatory violation. Your instructor reviews entries against 14 CFR Part 43 requirements. An entry that omits the data reference or the return-to-service statement fails.
Full-Cycle Scenario Exercises
In the two full-cycle scenarios the instructor presents a written squawk (discrepancy) as a DME would. You must: (1) interpret the squawk, (2) locate the relevant section of the AMM, (3) troubleshoot using the manual's fault-isolation procedure, (4) perform the corrective maintenance at the appropriate station, and (5) present completed documentation for final acceptance. The instructor acting as DME makes a final accept/reject call. This replicates the practical test flow exactly.
Pass Criteria
You must earn a go rating on at least 80% of all stations attempted. Any safety-of-flight critical error — incorrect torque on a flight-control fastener, incorrect ignition timing, FOD left in a closed assembly, or hydraulic fluid misidentification — results in immediate station failure and a mandatory repeat of that station before credit is awarded. Zero uncorrected safety-critical errors are permitted.
Key terms10
Worked examples4
- Confirm the tensiometer adapter matches the cable diameter — the #2 adapter is correct for this cable.
- Note ambient temperature: 70 °F. Because the temperature matches the reference temperature given in the rigging chart, no temperature correction is needed.
- Compare the measured tension (52 lb) to the specified tension (70 lb).
- Calculate the difference: 70 lb − 52 lb = 18 lb below the specified value.
- Determine acceptability: the cable is 18 lb low. Unless the AMM specifies a tolerance band that includes 52 lb, this is out of tolerance and requires re-rigging to bring tension to the specified value.
- Identify input pressure: 80 psi.
- Identify cylinder (downstream) pressure: 64 psi.
- Calculate pressure drop (leakage in psi): 80 psi − 64 psi = 16 psi.
- Calculate leakage as a percentage of input: (16 ÷ 80) × 100 = 20%.
- Note the location where escaping air is heard (intake, exhaust stack, or oil filler) to identify the leaking component — this directs further troubleshooting.
- Recall the conversion: 1 foot-pound = 12 inch-pounds.
- Divide the required inch-pound value by 12: 300 in-lb ÷ 12 = 25 ft-lb.
- Set the foot-pound torque wrench to 25 ft-lb.
- Torque the spark plug to 25 ft-lb, which equals the required 300 in-lb.
- Identify the shank diameter: 3/32 inch = 0.094 inch.
- Apply the formula: minimum head diameter = 1.5 × shank diameter.
- Calculate: 1.5 × 0.094 inch = 0.141 inch.
- Round to a practical shop measurement: the manufactured rivet head should be no less than approximately 0.141 inch (roughly 9/64 inch) in diameter.
- Measure the actual driven head and compare; if the head is smaller, the rivet must be drilled out and replaced.
The math in this lesson1
Materials: Training airframe (or representative airframe section), training reciprocating engine or engine trainer, sheet metal tools (rivet gun, bucking bars, drills, dimple dies), fabric inspection tools, compression tester, timing light, spark plug gap gauge and cleaner, cable tension meter (tensiometer), torque wrenches (inch-pound and foot-pound), safety wire pliers, hydraulic service equipment, multimeter, applicable manufacturer maintenance manuals, FAA Form 337 blank copies, maintenance logbook entry forms, PPE (safety glasses, hearing protection, chemical-resistant gloves as task requires), LOTO equipment, FAA-H-8083-31 and -32.
Check: Instructor scores each station task on an ACS-aligned practical evaluation form with go/no-go criteria matching those a DME would apply; maintenance record entries are graded for regulatory completeness; learners must earn a 'go' rating on at least 80% of all stations attempted, with any safety-of-flight critical error resulting in immediate station failure and mandatory repeat. Pass mark: 80% or higher go-rating across all stations; zero uncorrected safety-critical errors.
Practice check8
Answer each question, then check it. Nothing is recorded; this is your own practice.
