Definition
A borescope inspection is a non-disassembly visual examination performed by inserting a rigid, flexible, or digital-video optical probe through an existing access port or borescope plug into the interior of an aircraft component. The most common application is the turbine engine hot-section inspection — combustion liner, turbine nozzle guide vanes, high-pressure turbine (HPT) blades, low-pressure turbine (LPT) blades, and in some designs the combustor can or annular combustion chamber. A secondary set of applications covers compressor blade inspection, propeller blade internal inspection, and airframe structural cavities where visual confirmation of crack initiation is specified by the Structural Repair Manual or Airworthiness Directive.
Equipment has evolved through three generations. Rigid borescopes are straight-line optical tubes appropriate for access ports aligned with the inspection zone; they provide excellent optical resolution but cannot navigate corners. Flexible fiberscopes use a bundle of optical fibers around an articulating distal tip and dominated turbine inspection until the late 1990s. Modern videoscopes (digital video borescopes) replace the fiberscope's optical bundle with a miniature CCD or CMOS sensor at the probe tip, transmitting digital video at resolutions that permit measurement overlays and high-magnification still capture. Commercial leaders in aviation-grade videoscopes include Olympus IPLEX series, Karl Storz rigid systems, Waygate Technologies (formerly GE Inspection Technologies) Everest VideoProbe, and Yateks MV series. Most modern videoscopes record images and video files for attachment to the maintenance record, satisfying 14 CFR §43.9 documentation requirements with an objective visual record rather than a technician's written description alone.
Required inspection intervals are established by each engine manufacturer's Maintenance Planning Document (MPD) or Engine Shop Manual (ESM) and are model-specific. The CFM56-7B (Boeing 737 NG) HPT blade inspection is specified in the CFM56-7B MPD at intervals ranging from 3,000 cycles on high-cycle operations to 5,000 hours on low-cycle corporate operations, with borescope access via dedicated ports on the combustor casing. The CFM LEAP-1A/1B specifies HPT blade inspections with specific video-capture requirements per the GE/CFM MPD. Pratt & Whitney PW100 and PW150 turboprop families (ATR, Q400) require borescope inspections at intervals of 600–1,000 hours for the gas generator section, with inspection zones specified in the PW Aircraft Maintenance Manual (AMM) Chapter 72. The IAE V2500 (A320 family) and CFM56-5B both include hot-section borescope intervals in their MSG-3-derived MPD task structures. GEnx (B787/B747-8) and CF6 (wide-body legacy) families have programmatic borescope intervals published in the OEM MPD and, for airline operators, reflected in the Approved Maintenance Programme filed with the regulatory authority.
Personnel qualification requirements vary by jurisdiction and operator. Under 14 CFR Part 43, an Airframe and Powerplant (A&P) mechanic may perform and approve borescope inspections that fall within the scope of maintenance authorized by their certificate and within the limitations of the approved data (AMM, MPD). A Part 145 Repair Station quality manual may impose supplemental qualification requirements — a formal borescope certification course, a defined number of supervised inspections, and a written authorization in the quality manual's Authorized Inspector list. Under EASA Part-145, the Continuing Airworthiness Management Organisation (CAMO) or Part-145 organisation's Maintenance Organisation Exposition (MOE) defines the competence requirements for NDT and visual inspection tasks; AMC 145.A.35 establishes that personnel performing borescope inspections have received training applicable to the type and methods used.
Findings from a borescope inspection are categorized using manufacturer-provided serviceable limits and disposition criteria: findings within limits allow continued service; findings requiring monitoring and re-inspection are documented with a specific re-inspection interval; findings exceeding limits require removal from service for repair or replacement. The mandatory documentation under §43.9 must include the date, aircraft make, model, and serial number, the work performed in sufficient detail, and the signature and certificate number of the approving individual. Attachment of videoscope still images or video clips to the maintenance entry — linked by work order or squawk number — constitutes the objective evidence standard increasingly required by insurance underwriters and OEM warranty programs.
Why It Matters for Flight Schools
For flight training organizations operating turbine aircraft — multi-engine cadet programs on Beechcraft King Air variants, DA42/DA62 diesel twin fleets, or Part 141 programs that include turboprop or jet type rating endorsements — borescope inspection intervals can become a dominant maintenance scheduling constraint. A turboprop engine with a 600-hour borescope inspection interval on a training fleet flying 400 hours per aircraft per year produces a mandatory unscheduled maintenance event roughly every 18 months per aircraft, coinciding unpredictably with student schedules unless planned proactively. The cost of the inspection — labor plus videoscope rental or technician travel if the organization lacks in-house capability — is material, and the opportunity cost of a grounded aircraft during a peak training period is higher still.
The documentation discipline around borescope findings also matters at aircraft sale or re-lease. A prospective buyer or lessor performing a records review will look for borescope inspection entries at the correct intervals with legible findings documentation, and the absence of a scheduled borescope entry or a vague entry without finding details creates a negotiation issue or deal delay. Operators who maintain clean, digitally-referenced borescope records with attached videoscope imagery tend to realize better residual values on aircraft disposals.
How Aviatize Handles This
Aviatize's maintenance control module tracks borescope inspection intervals as scheduled maintenance tasks linked to each engine's time and cycle totals, distinct from airframe hours. When the MPD specifies a borescope inspection interval, the task is configured in the maintenance program with the correct threshold and repeat interval in hours, cycles, or calendar time, and the platform provides advance notice based on the configurable alert lead time — typically 50 hours before the due point. This prevents the scenario where a borescope inspection comes due inside a busy student scheduling week with no advance procurement of technician time or videoscope equipment.
When the inspection is completed, the maintenance execution module captures the findings entry with a structured disposition field — serviceable, monitor/re-inspect, or remove from service — along with the ability to attach videoscope image files directly to the digital maintenance record. The resulting record satisfies §43.9 documentation requirements and provides the objective evidence trail that supports aircraft re-lease, sale, and insurance renewal. For operators running multiple turbine aircraft, the maintenance control dashboard shows all upcoming borescope inspections across the fleet on a single timeline, enabling batch scheduling of inspections when a visiting borescope technician is on site.