King Air Inspections and How to Budget for Them

King Air 350 Cockpit

Purchasing a King Air 200 or 300 series is an exciting venture. A top-of-the-line business turboprop, the King Air boasts a powerful engine and is capable of flying over 1,000 miles with a full payload of fuel. It’s easy to see why it’s one of the most popular 6-10 passenger aircraft in history. As you prepare to purchase a King Air, you’ll start to consider the overall cost of inspections. Keep in mind that annual and per flight hour maintenance costs may vary depending on the number of hours flown per year. In this article, we will break down the key King Air inspection milestones and everything you need to know about labor costs so you can budget accordingly.

King Air Phased Inspections

Winner Aviation Infographic
It’s important to understand King Air inspections and how they are broken down. With King Air phased inspections, four critical inspections occur at intervals determined by the annual use of the aircraft. The complete phase cycle consists of 4 separate events, typically combined into a Phase 1 and 2, or a Phase 3 and 4. No matter how much or how little the aircraft is utilized, Textron’s phase programs assure that no King Air exceeds 12 months or 200 +/- 20 flight hours without completing at least one Phase inspection. A typical phased inspection covers:

  • Landing gear visual and operational checks
  • Engine visual inspections and servicing
  • Cabin section visual and structural inspections
  • Wing visual and structural inspections
  • Aircraft systems operational inspections
  • Empennage visual and structural inspections

Labor Costs: 90 hours of labor per combined phase*

*There are some MROs who will quote 75-80 hours of labor per phased inspection. In our experience, those estimates should be reviewed very critically as either the attention to detail will suffer, or your King Air may experience longer downtime.

Wing Bolt Inspections

Every five years, a wing bolt inspection must be performed on your King Air. A wing bolt inspection includes both a magnified visual inspection of the wing bolts and nuts, as well as a fluorescent liquid penetrant inspection. All flat surfaces, depressions, counterbores, and bolt bores at the upper forward, upper, and lower aft wing attach points are non-destructively inspected with a calibrated eddy current instrument. Also, due to loading factors and tendency to wear, the lower forward wing bolts and nuts are replaced during each 5 year inspection.

Additionally, every 20 years, all wing bolts must be replaced.

Labor Costs: 35 to 40 hours of labor for a wing bolt inspection

Parts Costs: ~$2,700 for wing bolt replacements* ~$275 for the lower forward bolts and nuts*

*Note: Because this replacement occurs every 20 years, parts costs are subject to inflation or changes.

King Air Propeller Overhauls

King Air propellers are overhauled every 4,000 flight hours (or 3,000 fight hours depending on propeller hub model) or every 6 years, whichever comes first. During a propeller overhaul, an operator has the option of overhauling their existing propellers (for a current estimated price of around $8000), purchasing exchange propellers, or upgrading to entirely new propellers.

During a prop overhaul, propellers are completely disassembled and inspected. During the inspection, all parts are refurbished back to their original standard or, when needed, parts are replaced. During the overhaul, it’s common that issues will be found with the prop hub or dome, so plan for an additional $2,000 to $3,000 on top of the prop overhaul costs. If the blades are worn out and need replacing, estimate an additional $12,000 on top of labor costs.

After re-installation of overhauled propellers or installation of new propellers, the assemblies are then dynamically balanced on the aircraft using a spectrum analyzer to assure continued smooth operation.

Labor Costs: 8 hours for dual propeller R+R, 8-10 hours for balancing

Landing Gear Inspection

Also at the 6 year mark is the landing gear inspection. The landing gear assembly takes a considerable amount of abuse throughout the life of the aircraft. Thousands of pounds of pressure bear down on the struts at each landing, and the dirt and debris encountered on aging and unimproved runways can damage dust seals and bushings. It’s critical that landing gear stays properly maintained and is inspected often. During this inspection, the landing gear is stripped, repainted, a service/leak check is performed, and the following components are often replaced:

  • Seals
  • Bearings
  • Bushings
  • Applicable placards
  • Hardware as required

During your 6 year landing gear inspection, all the associated equipment, such as wiring, lights, drag braces, actuators, and shimmy damper are inspected and dimensionally checked for wear to assure continued reliability in the air and on the ground.

Labor Costs: 150 hours*

*Because landing gear inspections typically include parts replacements (as mentioned above), there are additional parts costs considerations you’ll need to account for that will add at least $2,000 to $3,500.

Engine Hot Section Inspections

Hot sections are due every 1,800 hours and overhauls are due at every 3,600 hours. During a hot section inspection, the shroud segments, combustion chamber, and turbine blades are assessed to ensure the engine will safely and efficiently generate power.

During an engine overhaul, however, all engine components are disassembled, cleaned, inspected, reassembled, and tested. Everything from the gearbox and gas generator to the power section and reduction gearbox is overhauled.

In lieu of overhaul, operators also have the option to upgrade the engine and propeller package, which could offer them faster speeds and a reduction in time to climb.

Hot Section Costs: ~$40,000 – $80,000 per engine plus an additional 20-30 hours labor to facilitate airframe disassembly

Overhaul Costs: ~$350,000 – $450,000 per engine plus an additional 60-80 labor hours to facilitate engine removal and re-installation

How often do you have to overhaul an aircraft engine?

The timespan for an aircraft engine is roughly 1,500 to 2,500 hours, and there’s generally a year-based calendar factor of 12 years. If the aircraft is used for commercial purposes, a TBO is required. If it’s not a commercially used plane and it’s well cared for, the engine may have the ability to last longer than the TBO suggests.

Oxygen Bottle Hydrostatic Check


An oxygen bottle hydrostatic test is due at 36 or 60 months depending on the bottle. This test is mandated by both the King Air Airworthiness Limitations Manual and current DOT regulations. During a hydrostatic test, the strength and integrity of the oxygen bottle is determined. Over time, the oxygen bottle material can deteriorate, which would cause it to weaken and become susceptible to failure.

While this is a lower-cost inspection, it’s a vital one.

Labor Costs: 6 hours

Budgeting for your King Air Inspections

Every six years, aim to prepare for large expenditures to keep your King Air safe and compliant with FAA regulations. If you’re currently in the market for a King Air, use the six year milestone as a negotiating tactic—if someone is selling their King Air without at least the landing gear inspection and the prop overhaul being completed, you will know that you are looking at a $30,000 – $40,000 expense and you should work to negotiate that off of the purchase price.

After you’ve purchased your King Air, we’re here to help. Winner Aviation’s Maintenance Manager will walk you through how to combine inspection efforts to save on labor costs and help you plan the best schedule for your King Air inspections and maintenance. Contact us today with any questions you may have.


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