The Best Aviation Borescopes for Aircraft Engines

What the engine makers and the FAA ask for

Continental makes the borescope part of the routine. Its Standard Practice Maintenance Manual (M-0), which absorbed service bulletin SB03-3, calls for a cylinder borescope inspection at every 100-hour or annual inspection, when oil consumption is excessive, after an overspeed and whenever an anomaly is suspected. It says the inspection "must be used in conjunction with" the differential pressure test, with the probe through the upper spark plug hole.

Lycoming's newer engine manuals, such as those for the IO-360-P1A and YO-233-B2A, call for a cylinder borescope inspection at 400 hours, and the YO-233's also at its 25-hour check if oil consumption has increased. Lycoming's long-standing compression guidance, SI 1191A, doesn't mention a borescope, and we found no Lycoming bulletin setting borescope criteria for older engines.

The FAA's annual-inspection checklist, Part 43 Appendix D, asks only for a cylinder compression check; the word borescope doesn't appear in it. Savvy Aviation argues that isn't enough: it recommends borescoping every cylinder every 100 hours, or every 50 on turbocharged engines.

The probe: rigid, 8.5 mm, and a tip that looks back

Aviation spark plugs traditionally use an 18 mm thread, where car plugs use 14 mm, so the size limits that shape car scopes don't apply. AVweb's March 2025 report on Savvy Aviation's borescope program goes the other way: "Choose a rigid probe with an articulating tip. Next best is a semi-rigid unit," at least 8.5 mm across, and stay away from flexible scopes, "as they tend to flop around."

The tip matters as much as the probe. Savvy's inspection checklist views the exhaust valve head with the piston at bottom dead center and the tip bent about 180° back toward the cylinder head, and the valve seat with the valve open and the tip at about 90°, just inside the plug hole. A scope that only looks straight ahead can't take either view. One Van's Air Force member who owns a non-articulating scope finds looking back at exhaust valves "difficult to impossible".

In our search of current Amazon listings, only Vividia's VA-400 family combined a rigid 8.5 mm probe with a 180° tip. Several other 8–8.5 mm articulating scopes, such as SATA's 359570, use what their listings call semi-rigid gooseneck cables, the class AVweb rates next best. We haven't picked one, because we couldn't check those listings against maker specifications; SATA's US website, for one, doesn't list its scope. The other two picks are joystick scopes for airframes. Our articulating borescope guide covers the wider field.

Which one: cylinders, airframes or both

If you only inspect cylinders, buy the VA-400 v5 if you'll use a laptop, a Chromebook or an Android phone, and the VA-400i if you use an iPhone or iPad. Both carry the same rigid probe and 180° tip.

If you also inspect airframes, you need a second kind of scope, because a rigid tube can't follow a path through a wing. Choose the ME-610i if a phone suits you, or the Teslong TF600 for its own screen and longer reach. No single scope here does both jobs well, and the guidance above advises against a flexible scope in a cylinder.

Reading an exhaust valve

The exhaust valve is the part most worth seeing. Mike Busch describes a healthy valve's deposits as "almost perfectly symmetrical, similar to a bull's-eye," and a failing valve's as highly asymmetrical, with a hot spot on one side of the face.

Continental's list of abnormal conditions is short and specific. On the exhaust valve it lists "localized discoloration on the valve face circumference", "minute cracks" and "erosion (missing material)". In the bore it lists heavy scoring or piston rub, piston pin rub, corrosion, and excessive oil or heavy carbon, and on the piston crown, erosion, missing material and damage from foreign debris. It also notes that an upper bore with no visible hone pattern is normal in a cylinder that has been in service.

Savvy's analysts reviewed 1,550 sets of borescope images and found at least one distressed exhaust valve in 27% of them, and 85% of those valves were at an early stage. Read what you see alongside the differential pressure result, and take anything doubtful to your mechanic; our engine inspection guide covers the method step by step.

Turbines and the PT6: a different class of tool

A PT6 borescope inspection is not a plug-hole job. Pratt & Whitney Canada ties it to fuel-nozzle maintenance, which Covington Aircraft puts at every 200 to 400 hours, and the probe typically goes in through a fuel manifold adapter port, inside an engine-specific P&WC guide tube. On some engines it has been mandated: FAA AD 2014-17-08 called for repeat borescope inspections of the compressor-turbine blades on PT6A-114 and -114A engines.

The scope is specified too. P&WC's 2011 service information letter on PT6A borescope equipment called for a probe no thicker than 4.5 mm, at least 1,300 mm long, that steers at least 120° in all four directions. None of the scopes on this page meets that, and nor does the two-way Vividia D3245 that Vividia's US brand-holder markets for PT6 engines, which is why it isn't a pick.

The bigger gap is measurement. The engine manual sets limits, and a professional videoscope measures a nick or crack to compare against them; Duncan Aviation's Shawn Schmitz has described measuring a nick's depth to decide whether a blade is still airworthy. A consumer scope can't do that, because the scale of the image changes with the tip's distance from the part. It can show you that something is there. Deciding what it means takes the professional tool and the people trained to use it.

Looking is not signing off

Under the FAA's definitions, inspection is maintenance (14 CFR 1.1). An owner-pilot may do only preventive maintenance. Part 43 Appendix A lists examples, which the FAA says aren't all-inclusive, and a borescope inspection isn't among them. We found no FAA ruling on whether an owner's own look inside a cylinder counts as maintenance.

So treat your own pictures as information for your mechanic, not as a finding. The inspection that goes in the logbook, and any decision about a cylinder's airworthiness, belongs to an A&P, an IA or a repair station. A good set of photos, taken at the same angles every time, is still worth having: it makes that conversation shorter, and it lets you watch a valve change between annuals.

Where the guidance comes from

The maintenance guidance on this page comes from these documents. Product sources are listed under each pick.

• Continental Standard Practice Maintenance Manual M-0, section 6-4.11.3, Cylinder Borescope Inspection (formerly SB03-3).
• Lycoming engine maintenance manuals for the IO-360-P1A and YO-233-B2A, and Service Instruction 1191A, Cylinder Compression.
• 14 CFR 1.1, 43.3 and 43.7, Part 43 Appendices A and D, and the FAA's 2009 Coleal legal interpretation on preventive maintenance.
• Mike Busch, EAA Sport Aviation, August 2010, on exhaust valve failures; AOPA Pilot, May 2017, March 2024 and June 2025; Savvy Aviation's Cylinder Borescope Inspection Checklist.
• AVweb, March 2025, on Savvy's borescope initiative.
• KITPLANES, 2023, on aviation and automotive spark plugs.
• Pratt & Whitney Canada, SIL GEN-PT6-029, Borescope Equipment (2011), its Airtime blog on PT6A line maintenance (2018), and its PT6A-60 series training manual; Covington Aircraft, Understanding a Borescope Inspection (2022); FAA AD 2014-17-08.
• Aviation Maintenance magazine, July 2017, interviewing Duncan Aviation's Shawn Schmitz; Waygate Technologies patent US7170677, on stereo measurement.
• Van's Air Force forum, 2021–2022, borescope recommendation thread.