How to inspect an aircraft engine with a borescope

Inspect an aircraft engine with a borescope by following the engine manufacturer's maintenance procedure: prepare and secure the engine, enter through the designated access point, examine the required surfaces, record identifiable views, and assess findings against the applicable limits. A clear image is only part of the job. The probe must reach the prescribed inspection area, and the record must show exactly which component and surface you examined.

Start with the engine model, inspection task, access dimensions and required viewing direction. Under 14 CFR 43.13(a), maintenance methods must follow the current manufacturer's maintenance manual or Instructions for Continued Airworthiness, or other methods acceptable to the FAA. Fiberscope.net sells professional inspection equipment and services it in-house.

How to inspect an aircraft engine with a borescope

Use the engine-specific inspection procedure to control access, coverage and acceptance. Under 14 CFR 43.13(a), the applicable maintenance instructions govern the work; camera controls alone cannot establish the inspection method.

The practical sequence is:

1. Identify the engine and the exact inspection task.
2. Review preparation, access and inspection requirements.
3. Match the probe and optics to the prescribed route.
4. Secure the engine and establish foreign-object control.
5. Inspect each required surface systematically.
6. Record findings with component identification and orientation.
7. Evaluate indications, restore access points and complete the maintenance record.

Piston and turbine engines require different routes and coverage. A piston-cylinder inspection can involve viewing through a spark-plug opening; turbine procedures can specify dedicated inspection ports and particular rotor positions. Use the route assigned to the engine and task.

For equipment selection beyond this procedure, the guide to industrial borescopes covers the broader equipment category.

Establish the inspection task before choosing equipment

14 CFR 43.13(a) makes the maintenance method the starting point. Identify whether you are performing a scheduled inspection, investigating a reported condition, or examining a particular component after an event.

Write down the engine model and serial number, the applicable maintenance-document reference and revision, and the required inspection area. Include the reported symptom or event when relevant. This gives the technician interpreting the images a defined question to answer.

For a piston engine, the task might concern a cylinder wall, piston crown or valve face. For a turbine engine, it might concern compressor blades, combustor surfaces or turbine components. Each task needs its own coverage plan and applicable limits.

Gather the documentation before opening the engine:

• The applicable maintenance procedure and illustrated access information.
• Required inspection tools, adapters and positioning equipment.
• Relevant service information and applicable airworthiness directives.
• Previous inspection images and maintenance history, when available.
• The recording and reporting requirements for the task.

Choose the inspection system after you understand the required view. A convenient access opening has value only when it leads to the surfaces the procedure requires.

Match the probe to the access and required view

Probe outside diameter, working length and viewing direction determine whether you can complete the inspection. Outside diameter, or OD, is the probe's external size; working length is the insertion length available to reach the target.

Measure the usable access passage and account for fittings, guides and restrictions along the route. Then establish the distance and direction from that opening to the inspection surface. An articulating tip changes viewing direction, but the insertion tube still needs a suitable path.

Use this decision table when defining the equipment requirement:

Inspection constraint	Equipment characteristic to evaluate	Practical benefit	Boundary to account for
Restricted access	Probe OD and tip dimensions	Allows entry through the prescribed passage	Clearance throughout the route matters
Straight, direct route	Rigid optical access	Supports a controlled view along a straight passage	The shaft follows a straight path
Turning route	Flexible insertion tube	Follows an accessible curved passage	Bend geometry and insertion handling matter
Surface behind the tip	Articulation or suitable side-view optics	Directs the view toward the required surface	Viewing clearance remains necessary
Deep inspection area	Working length	Reaches the assigned component	Excess insertion tube needs controlled handling
Small indication	Appropriate optics and measurement capability	Supports detailed examination	Acceptance depends on the required method

Rigid borescopes use rod-lens relay optics and require illumination through a light guide or handle. Fiberscopes transmit an image through a coherent fiber bundle. Videoscopes use an imaging sensor at the distal end of the probe.

The guide to inspection cameras by probe diameter addresses access sizing. Treat clearance, reach and viewing geometry as separate requirements.

Prepare the engine and establish tool control

Complete the engine-specific shutdown, cooling, isolation and access instructions before inserting the probe. Under 14 CFR 43.13(b), maintenance work must leave the engine at least equal to its original or properly altered condition in the qualities affecting airworthiness.

Assign responsibility for engine positioning and borescope handling. Where the procedure requires rotor or crankshaft movement, establish the approved sequence and clear communication between the people performing those tasks.

Prepare a clean work area and account for everything introduced near an opening:

• Removed plugs, covers, fasteners and sealing components.
• Probe guides and access adapters.
• Detachable optical tips and their retention arrangements.
• Cleaning materials and protective covers.
• Tools used for access and restoration.

Inspect the probe exterior, distal tip and articulation function before entry. Check the lens and make a trial recording outside the engine. Open that recording to check focus, exposure and file capture before starting the inspection.

Arrange the insertion tube so its weight stays supported and its route remains controlled. Keep the display visible to the person directing the tip. Good positioning reduces the temptation to advance the probe while watching the access opening instead of the inspection image.

Inspect a piston engine cylinder systematically

Use the piston-engine maintenance procedure to establish access, piston position and required coverage. A cylinder bore is straight; viewing the cylinder wall, piston crown and valve surfaces requires suitable viewing geometry through the authorized opening.

Inspect a cooled engine under the applicable preparation instructions. Remove the designated spark plug using the prescribed maintenance method, and protect the opening and surrounding area from contamination.

Orient the image before collecting close-ups. Identify recognizable features, then follow a repeatable route through the required surfaces. Keep cylinder identification attached to every image sequence so that a later reviewer can associate each finding with the correct location.

Record an overview before moving closer to an area of interest. For example, a cylinder-wall indication needs enough surrounding structure to show its position, followed by a detail view that shows its visible characteristics.

Lighting and angle affect interpretation. Move the view deliberately to distinguish surface texture from glare and to inspect the same area from another useful direction. Compare findings with the applicable manufacturer guidance and previous records when available.

Maintain the distinction between observation and diagnosis. Describe visible scoring, deposits, discoloration or material damage accurately, then use the prescribed evaluation process to determine the maintenance action.

Inspect turbine components through the prescribed ports

A turbine-engine borescope inspection follows the manufacturer's specified ports, component sequence and positioning method. Under 14 CFR 43.13(a), the procedure also governs the equipment and techniques used to examine the required areas.

Establish the component reference before advancing: engine section, stage, blade or vane identification, and the inspection surface required by the task. An isolated close-up becomes useful when its location can be recovered from the record.

Follow the prescribed sequence for accessible airfoils, platforms, combustor surfaces and other assigned components. Track coverage as you work. If the procedure calls for particular edges, faces or attachment areas, record completion against those requirements.

Coordinate any engine movement with probe position. Use the manufacturer's instructions for withdrawal, clearance and repositioning, with one person clearly controlling the movement command.

For indications such as cracking, erosion, impact damage or coating distress, capture the surrounding component and the detailed area. Where dimensional assessment is required, use the prescribed measurement equipment and method. The acceptance decision belongs to the applicable limits and authorized maintenance process.

Record evidence that another technician can interpret

Under 14 CFR 43.9, maintenance records require specified information about the work performed and its approval. Inspection images support that record when their identity, location and relationship to the inspection task remain clear.

Use a consistent evidence structure:

Record element	What to capture	Why it helps
Engine identity	Model, serial number and relevant aircraft identification	Associates evidence with the correct asset
Procedure reference	Task and revision used	Establishes the inspection basis
Component location	Cylinder, stage, blade or other applicable identifier	Makes the finding traceable
Orientation	Recognizable features and viewing direction	Allows another reviewer to understand the view
Overview	Component and surrounding structure	Establishes context
Detail	The indication at a useful angle and focus	Supports evaluation
Disposition	Applicable limit and maintenance action	Connects evidence to the decision

Keep original files and preserve the relationship between images, notes and component identifiers. Use the organization's approved storage and retention process.

A useful finding description separates observation from evaluation. Record what is visible, where it appears and which reference governs its assessment. Add measurements only when the required measurement method supports them.

Resolve poor images and incomplete coverage

Troubleshoot image quality before interpreting an indication. Under 14 CFR 43.13(a), the inspection still needs to meet the applicable maintenance method, including its required coverage and equipment.

Problem	First action	Next decision
Bright glare	Adjust illumination and viewing angle	Re-examine the surface with useful detail visible
Soft image	Check lens cleanliness and working distance	Restore a focused view before recording evidence
Uncertain orientation	Return to a recognizable feature	Re-establish the component reference
Restricted movement	Stop advancing and assess the route	Follow the approved withdrawal or repositioning method
Missing surface coverage	Review the task and access arrangement	Use the prescribed additional access or equipment
Apparent dimensional defect	Identify the required measurement method	Obtain the measurement needed for disposition

Forcing a probe risks both the equipment and the engine. Stop when movement becomes restricted, maintain control of the insertion tube and use the approved recovery procedure.

Working length also deserves attention during troubleshooting. The guide to borescope working length for industrial access explains reach as an equipment-selection factor.

Restore the engine and complete the record

Finish with probe and tool accountability, access restoration and the applicable maintenance entry. Under 14 CFR 43.9, record the work description or acceptable reference, completion date and required identification and approval information.

Withdraw the probe under control and inspect it for damage or missing parts. Reconcile detachable tips, adapters, tools and removed hardware with the pre-inspection inventory.

Restore plugs, covers, seals and other access components using the prescribed installation requirements. Complete any required follow-on checks before the engine returns to service.

Report inspection coverage as carefully as findings. If a required area remains unexamined, resolve that task through the maintenance procedure and responsible personnel. Save the final evidence package with the corresponding maintenance documentation.

FAQ

Define the camera requirement from the inspection task

Build the equipment request around access opening, straight or turning route, insertion length, viewing direction, environment and recording needs. Include any measurement requirement from the engine procedure.

Send those details to a Fiberscope.net technical specialist, together with the engine model and inspection task, or call 1-877-613-2210. Fiberscope.net matches professional inspection equipment to the access and evidence required for the job.

Related guides

• Articulating borescopes and viewing control

Author: Vladimir Khubiryants

Founder & President, Fiberscope.net (MEDIT Inc.)

Vladimir Khubiryants founded Fiberscope.net to give professionals access to reliable video inspection equipment without enterprise pricing. For over 20 years he has sourced and tested borescopes, sewer cameras and fiberscopes in Fiberscope.net's in-house test and repair facility, helping plumbers, pipeline engineers, aviation and military teams choose the right tool for the job.