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Aircraft Maintenance B Check

Updated: Jan 11, 2022

Aircraft Maintenance B Check

Scheduled B Checks for Aircraft Airworthiness

As aircraft designs and manufacturing capabilities have improved, inspection frequency has decreased. Aircraft undergo constant inspections beginning with the walk around before each flight to the increasingly more in-depth and scheduled inspections known as Checks. These checks are commonly known as A, B, C, and D Checks. An A Check is a relatively small step up from a preflight walk around but a D Check requires a thorough tear down of the aircraft to inspect every fastener and component.

As an example of how reliability and airworthiness has dramatically improved over the years, the new Boeing 787 is scheduled for a D Check approximately every 12 years compared to every 6 years for older aircraft. Likewise, many current aircraft no longer require a B Check.

Not All Aircraft Require a B Check

Airlines are diligent about maintaining aircraft both for the flying public’s safety and to assure these complex and expensive machines are profitably reliable. Each airline develops an FAA approved Continuous Airworthiness Maintenance Program (CAMP). These programs (frequency and inspection details) are developed based on recommendations (and directives) created by maintenance steering groups (MSG) and industry steering committees (ISC) that are submitted to the maintenance review board (MRB). In turn, the MRB makes final recommendations to the manufacturer that provides airlines with maintenance planning documents. Clearly, a lot of people and knowledge goes into the CAMP.

A Checks are performed relatively frequently (every 500FH). Because of the frequency and different tasks performed, these are commonly known as A1, A2, A3, etc. Like the A Check, the B Check is mostly routine maintenance but expanded to include a more thorough inspection and maintenance of some engine components, aircraft part replacements, and more. B Checks that were common for older aircraft such as the B737-300, -400, -500, L1011, and MD80 have mostly been incorporated into Checks A1 through A10 (or A12).

Newer models such as the Boeing B737-700 through -900, A319, A320, ATR42-300, and many more have never required a B Check separate from what was incorporated into A Checks.

This saves cost to the airlines by reducing aircraft down time, improving manpower usage, improved maintenance scheduling, and better usage of resources such as hangars and test equipment. By carefully reviewing scheduling, this has been accomplished while maintaining aircraft safety and reliability.

Boeing Divisions

Boeing Commercial -

Boeing Defense -

Older B Check Procedures

B Checks were performed every 6 to 8 months or 400 to 900 flight hours. Single aisle planes required 120 to 150 man hours but twin aisle planes could take 300 man hours. Most were done at an airport hangars rather than at maintenance facilities. Compared to the lighter A check, the more extensive B Check includes torque tests and flight control tests.

As an example, an A Check typically involves lubricating the nose gear actuator. A more extensive B check would include inspecting the wheel well hydraulic tubing for condition, corrosion, and fluid leakage. It would also include checking alignment and torqueing of the nose landing gear spot light. B Checks would also check uplock and downlock proximity sensors as well as wheel well door linkages, springs, stop cables, drive rods, and hinges. As part of cost and time savings, these inspections and any needed repairs have been incorporated into the proper A Check sequence.

At approximately the same time as B Checks were phased out, the experience and knowledge levels of inspectors and mechanics was declining due to older people retiring and being replaced by younger people. It also coincides with a shift from on-the-job-training to more computer-based training. Besides conducting training, the computer software measures other factors involved with aircraft inspections such as recognizing a known number of defects shown in the training images and how time constraints affect quality. Technology in the form of training, better designs, manufacturing capabilities, and other enhancements continues playing a prominent role in the safety, reliability, and cost of operating aircraft.

Many parts are needed for checks, therefore we recommend AeroBase Group for the material needed to maintain your aircraft.

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