What Is a 100 Hour Inspection: A Comprehensive Guide for Aviation Mechanic Students

For aircraft used in commercial operations, regular maintenance inspections are crucial for ensuring safety and regulatory compliance. One of the most important maintenance requirements is the 100 hour inspection. At Hillsboro Aero Academy, we understand the importance of aircraft safety and proper maintenance to provide our students with reliable training aircraft. This guide explains what a 100 hour inspection is, when it's required, and what it involves.

Key Points: 100 Hour Inspections

• 100 hour inspections are FAA-mandated safety checks required for aircraft used in commercial operations, including flight instruction.
• These inspections must be performed by certified A&P mechanics after every 100 hours of flight time.
• The inspection covers all major aircraft systems including the airframe, engine, flight controls, and avionics.
• Unlike annual inspections, 100 hour inspections don't require an IA mechanic but are required more frequently.
  
  

Understanding the 100 Hour Inspection

A 100 hour inspection is a detailed examination of an aircraft that must be conducted after every 100 hours of flight time for certain aircraft operations. This inspection is mandated by the Federal Aviation Administration (FAA) under Federal Aviation Regulation (FAR) 91.409(b) to ensure continued airworthiness and safety for aircraft used in specific commercial operations.

Unlike the annual inspection required for all aircraft regardless of use, the 100 hour inspection applies specifically to aircraft that are:

• Used for carrying persons for hire (such as charter operations)
• Used for flight instruction when the instructor provides the aircraft

These regulations are in place so that aircraft engaged in commercial operations, which typically see more frequent use and wear, undergo regular safety checks to maintain their airworthiness certificate and operational safety.

At Hillsboro Aero Academy, these inspections are a regular part of our aircraft maintenance routine since our fleet is used extensively for flight instruction.

Who Can Perform a 100 Hour Inspection?

A 100 hour inspection must be performed by a qualified aviation maintenance technician holding an Airframe and Powerplant (A&P) certificate. Unlike an annual inspection, which requires an A&P mechanic with Inspection Authorization (IA), the 100 hour inspection can be performed by any certified A&P mechanic.

At Hillsboro Aero Academy, our maintenance team consists of experienced A&P mechanics who thoroughly understand the requirements of these inspections and maintain our fleet to the highest standards for the safety of our students and instructors during flight instruction.

What's Included in a Complete Inspection?

A 100 hour inspection is a comprehensive examination of virtually every system and component of the aircraft. The inspection includes but is not limited to:

Airframe

• Inspection of the fuselage, wings, empennage, and all inspection panels
• Checking for structural integrity, corrosion, and proper operation of all doors and windows
• Examination of landing gear systems and components

Engine and Propeller

• Detailed inspection of the engine, including compression checks
• Examination of engine mounts, cowlings, and baffles
• Inspection of the propeller, spinner, and associated components
• Performing an aircraft run up to check engine parameters

Flight Controls

• Inspection of all flight controls for proper operation and security
• Checking control cables, pulleys, and attachments
• Verification of control surface travel and rigging

Systems

• Inspection of fuel, hydraulic, and electrical systems
• Checking avionics and instruments
• Verifying compliance with all applicable airworthiness directives

100 Hour Inspection vs. Annual Inspection

While the 100 hour inspection and annual inspection cover similar ground, there are key differences between them:

An annual inspection can serve as a 100 hour inspection, but a 100 hour inspection cannot replace an annual inspection.

Progressive Inspection Programs

For aircraft that are used heavily, such as those in our airplane and helicopter fleets at Hillsboro Aero Academy, the FAA allows for progressive inspection programs. These programs break down the complete inspection into smaller segments that can be completed at shorter intervals.

For example, instead of performing one large inspection every 100 hours, the inspection tasks might be divided into four segments performed every 25 hours. This approach can help minimize aircraft downtime while still maintaining the same level of safety and thoroughness.

The Importance of Proper Documentation

Proper documentation is crucial for 100 hour inspections. The mechanic must make an entry in the aircraft's maintenance records including:

1. The type of inspection (100 hour)
2. The date of the inspection
3. Aircraft total time in service
4. The signature, certificate number, and type of certificate held by the person approving or disapproving the aircraft for return to service

These records are essential for proving regulatory compliance and are carefully maintained as part of our safety protocols at Hillsboro Aero Academy.

The "Grace Period" for 100 Hour Inspections

The FAA provides a small "grace period" of up to 10 hours beyond the 100-hour mark, but only for the purpose of reaching a location where the inspection can be performed. This is not an extension of the inspection interval but rather a practical allowance for aircraft that may not be near maintenance facilities when they reach the 100-hour mark. 

Any time used during this grace period must be subtracted from the hours available before the next 100 hour inspection is due. The 100-hour limitation may be exceeded by not more than 10 hours while en route to reach a place where the inspection can be done. The excess time used to reach a place where the inspection can be done must be included in computing the next 100 hours of time in service.

Why 100 Hour Inspections Matter for Flight Training

For aspiring pilots in our professional pilot programs, understanding maintenance requirements is an important part of developing a comprehensive knowledge of aviation operations. These inspections directly impact flight training in several ways:

1. They uphold the safety of training aircraft
2. They minimize unexpected maintenance issues that could disrupt training schedules
3. They provide real-world examples of the regulatory compliance pilots can encounter throughout their careers
4. They demonstrate the industry's commitment to safety standards

At Hillsboro Aero Academy, we believe that familiarity with these maintenance requirements helps train pilots who are more knowledgeable about all aspects of aircraft operations.

Ready to Start Your Aviation Journey?

At Hillsboro Aero Academy, we maintain our training fleet to the highest standards, so you can train in safe, well-maintained aircraft. Our commitment to proper maintenance and safety is just one aspect of our comprehensive approach to flight training.

Whether you're interested in becoming a professional pilot or just curious about aviation maintenance requirements, we're here to help. Contact us today to learn more about our programs and how we can help you achieve your aviation goals.

Frequently Asked Questions About Aircraft Inspections

How do mechanics perform annual inspections?

Annual inspections are performed by A&P mechanics who hold an Inspection Authorization (IA) credential. These inspections follow the same basic checklist as 100 hour inspections but are required regardless of how the aircraft is used. The IA must thoroughly inspect the aircraft according to the manufacturer's recommendations and FAA regulations, then document and certify the results.

What is a provisional airworthiness certificate?

A provisional airworthiness certificate is a temporary certificate issued by the FAA for specific purposes, such as production flight testing of new aircraft designs. Unlike a standard airworthiness certificate, provisional certificates have significant limitations on the operations permitted and are not typically relevant for training aircraft or private aircraft.

Do private aircraft require 100 hour inspections?

No, private aircraft used solely for personal flying do not require 100 hour inspections. They only need annual inspections. However, if a private aircraft is occasionally used for commercial purposes like flight instruction, then 100 hour inspections would be required during those periods of commercial use.

When is a special flight permit required?

A special flight permit, sometimes called a "ferry permit," is required when an aircraft needs to be flown even though it may not meet applicable airworthiness requirements. Common scenarios include flying an aircraft to a maintenance facility for repairs, evacuating from dangerous weather, or conducting flight tests after repairs. These permits provide limited authorization for specific flights under restricted conditions.

What is a current experimental certificate?

A current experimental certificate is an airworthiness certificate issued for aircraft in the experimental category. These certificates are typically issued for amateur-built aircraft, research and development, exhibition, or air racing. Aircraft with experimental certificates operate under different regulations than standard category aircraft and have specific limitations on their operations.

This article presents a general overview of the field of aviation, including job opportunities within that field; it does not describe the educational objectives or expected employment outcomes of a particular Hillsboro Aero Academy program.  Hillsboro Aero Academy does not guarantee that students will obtain employment or any particular job. Some positions may require licensure or other certifications. We encourage you to research the requirements for the particular career you desire.