What is an engine borescope inspection?
An engine borescope inspection (BSI) is a visual inspection of the inside of a gas turbine engine, done with a camera probe inserted through access ports instead of taking the engine apart. Operators and MROs use it to check compressor, combustor and turbine hardware for damage without removing the engine.
By InspectView · Published October 1, 2026 · Updated October 1, 2026
When an engine gets one
| Trigger | Examples |
|---|---|
| Scheduled maintenance | Intervals set by the maintenance program and the engine manual |
| Airworthiness directives and service bulletins | Repetitive checks of a specific part, such as the proposed CFM56 HPT front seal inspections in FAA-2026-8803 |
| Events | Bird strike, foreign object ingestion, over-temperature, surge or stall |
| Trend monitoring | A shift in exhaust gas temperature or vibration that needs a closer look |
| Transactions | Lease return, redelivery and pre-purchase |
| Troubleshooting | Deciding whether an engine needs to come off the wing |
What it checks, module by module
| Module | What inspectors look for |
|---|---|
| Fan and booster | Nicks, dents, tears and erosion on blades |
| High-pressure compressor | Nicks, dents, tip curl, erosion and missing material on blades and vanes |
| Combustor | Cracks, burning and coating loss on the liner, and the condition of the fuel nozzles |
| High-pressure turbine | Coating loss, burning, cracks, erosion and missing material on nozzle guide vanes and blades |
| Low-pressure turbine | Cracks, burning and other damage on blades and vanes |
| Exhaust | Cracks, damage and debris |
The engine manual sets which ports, stages and areas each task covers, and the limit each finding is checked against.
How it's done
- Access. The probe goes in through dedicated borescope ports and, for some tasks, through igniter or fuel nozzle openings, as the manual directs.
- Rotation. The inspector turns the compressor or turbine slowly, by hand or with a drive tool on the gearbox, so each blade passes the camera.
- Imaging. Videoscopes articulate their tip, record video and stills, and on many models measure findings in 3D.
- Assessment. Each finding is compared with the manual's limits for that location.
- Reporting. Findings, images and dispositions go into a signed report.
Borescope, fiberscope or videoscope?
Strictly, a borescope is a rigid optical tube for straight-line access, a fiberscope is flexible and carries the image through fiber-optic bundles, and a videoscope puts a camera at the tip. In aviation, "borescope" covers all three, and videoscopes are now the standard tool for engine work.
Who can perform and sign it
- United States: maintenance on US-registered aircraft must be done by persons authorized under 14 CFR Part 43, such as certificated mechanics with a powerplant rating, certificated repair stations and air carriers under their own maintenance programs. The same rules govern who approves the engine for return to service.
- European Union: the work is performed under an EASA Part-145 approved maintenance organisation, and the release is signed by certifying staff holding the appropriate Part-66 licence.
- Software: AI can support the inspection, but a certificated person makes the airworthiness call and signs. See AI in borescope inspection.
How long it takes
It depends on the engine and the task. A targeted check of one area can take a few hours, while a full gas-path inspection takes longer. For one specific task, the HPT front seal inspection proposed in FAA-2026-8803, the FAA estimates 8 work-hours.
What drives the cost
The engine type and the scope of the task, whether the engine is on wing or in a shop, travel and AOG urgency, measurement needs, and the report format your customer requires. Request an inspection for a quote.
What the report should contain
Engine identity, the reason for the inspection, references, equipment, a status for each module, findings by stage with images and measurements, and the inspector's sign-off. See the full checklist or download the free template.
A common finding
Coating loss on hot-section parts is a common finding. See TBC spallation: what it looks like on a borescope.
Where AirCheck fits
AirCheck reviews borescope video frame by frame, flags possible damage by stage, cites the manual on every finding and drafts the report your inspector signs. Book a demo.
Frequently asked questions
Is a borescope inspection non-destructive testing?
Yes. It's a visual inspection method, used in engine maintenance alongside other non-destructive methods such as eddy current, ultrasonic and penetrant inspection.
Can it be done on wing?
Yes. Most engine borescope inspections are done with the engine installed, which is why they help avoid unnecessary removals.
How often is an engine borescoped?
As often as the maintenance program, airworthiness directives and events require. Intervals vary by engine, operator and earlier findings.
What happens if damage is found?
The inspector checks it against the manual's limits. Within limits, the engine stays in service; some findings call for a repeat inspection at a shorter interval; findings beyond limits need repair or removal before further flight.