aircraft inspection
aircraft inspection

One key feature of proper aircraft safety is routine maintenance. Keeping all aircraft – from commercial airplanes to private jets – airworthy is a multistep process, and because of this, the 100-hour aircraft inspection is one of the most important routine checks that an aircraft undergoes. 

This essential inspection is typically done, as its name suggests, after every 100 hours of flight time. However, the time can vary by the aircraft’s make and model. The aircraft inspection is performed to make sure that the aircraft is airworthy for the next 100 hours of flight time. 

The inspection itself includes a thorough examination of the entire aircraft, from top to bottom, including its:

  • Engines
  • Propellers
  • Fuel system
  • Hydraulic systems
  • Interior
  • Exterior
  • Tires

To keep everyone safe, both the flight personnel and the passengers aboard the aircraft, the 100-hour inspection aviation companies and other aircraft owners follow is a standard that everybody needs to know. 

To help better shed some light on this rigorous but much-needed process, here’s a guide to teach you everything you need to know about what happens during a 100-hour inspection and an annual inspection!

What is the difference between a 100-hour aircraft inspection and annual aircraft inspection? 

In practice, both annual and 100-hour inspections are almost the same. For the most part, they check for the same things, and what happens in a 100 hour aircraft inspection also usually happens in annual inspections.

However, there are two key differences:

  1. How often they’re done
  2. Who does them

As far as how often they’re performed, their names give them away. A 100-hour inspection happens after every hundred hours of flight time, whereas an annual inspection occurs once a year. 

And who does them? An A&P (airframe and powerplant mechanic) is authorized to perform a 100-hour inspection, but to do an annual inspection, the A&P needs a specific type of certification called Inspection Authorization (IA) to complete the inspection.

Guide to 100-Hour and Annual Aircraft Inspections 

Both 100-hour and annual inspections are required by the Federal Aviation Administration (FAA) for most types of aircraft. Whether they’re commercial airliners or small hobbyist planes for practice, they all need to be checked regularly.

These regulations, however, do not apply to any turbine-powered rotorcraft, like helicopters. Nor do they apply to certain types of larger commercial aircraft. These have a different set of needs. In fact, helicopters are even more maintenance-hungry than most other smaller aircraft.


100-Hour Inspection Requirements

An aircraft inspection is extremely exhaustive and time-consuming, and it covers everything from the interior of the aircraft to the exterior. Here are a few important things you should know about what happens during a 100-hour inspection.

Who performs the inspection?

For 100-hour inspections, any certified aircraft or mechanic can do it, just as long as they have the right tools and space. Or, conversely, the aircraft may be sent to the manufacturer so they could do their own 100-hour inspection themselves.

When is the aircraft inspected? 

The 100-hour inspection needs to be performed on aircraft after every 100 flight hours. This means that any aircraft that sees a lot of use would often have multiple 100-hour inspections in a year.

Examples of these heavy-use aircraft are:

  • Company transport aircraft
  • Pilot school practice aircraft
  • Passenger and cargo aircraft

For owners who do use their aircraft more often, they may opt for a progressive inspection to reduce their downtime. That way, they get their aircraft checked more often but in less long inspection times. A progressive inspection can be done during an aircraft’s normal downtime, like between take-offs or after a flight session.

What does the 100-hour inspection cover? 


So when the plane has been brought to the hangar for checking, what happens in a 100 hour aircraft inspection? Here’s an aircraft’s 100-hour inspection checklist that mechanics typically check:

  • Inspection plates and access doors
  • Fairings, airframe, and cowlings
  • Fuselage and hull
  • Cabin and cockpit
  • Engine and nacelle
  • Landing gear
  • Wings
  • Center section
  • Fabrics
  • Empennage assembly
  • Propeller
  • Radio
  • The transponder
  • And other miscellaneous items

In a way, 100-hour inspections check for all parts of the aircraft, both inside and outside – the seats, the radio, the frames, everything. This is all to make sure that nothing that may have broken down in the past 100 hours goes unrepaired or unreplaced.

Annual Inspection Requirements

In many ways, what happens in an annual inspection is much more important than a 100-hour inspection. While both are unquestionably needed, annual inspections are checked by better-certified mechanics.

Who performs the inspection? 

Not all A&P mechanics can do an annual inspection. Only those with an Inspection Authorization (IA) from the Federal Aviation Administration can perform an annual inspection.

To get an IA, an aircraft mechanic should have the following:

  • A mechanic certificate that has been active for at least 3 years
  • At least 2 years of active aircraft maintenance service
  • Has a fixed base of operations and a telephone number to be contacted during workdays
  • Passes the exam for IAs

But of course, if a pilot or owner also holds an IA, then they could do their own annual inspections anytime they like.

When is the aircraft inspected? 

In an annual inspection, the aircraft is inspected once per year. More precisely, it has to be done every 12 calendar months or sooner. If an aircraft has not been given an annual inspection after this time, then it is no longer considered airworthy and not allowed to leave the ground on its own.

There are, however, legal ways to fly an aircraft with an expired annual inspection. For instance, if the aircraft has a special flight permit (also known as a Ferry Permit) or a provisional airworthiness certificate, then they may be flown within the limits of their permits. The same goes for those with experimental certificates.

What does the annual inspection cover?

The annual inspection covers the same things as the 100-hour inspection does. In fact, the annual inspection can also cover for the 100-hour inspection when it’s due. When an aircraft has completed its annual inspection, the next inspection should be after the next 100 hours. That is, unless it won’t be flying much for the next 12 months.

Other Aircraft Inspections


In addition to these two and progressive inspections, there are also other kinds of aircraft inspections:

  • 50-hour inspections
  • Pre-flight checks
  • Post-flight checks
  • ABCD check system
  • Progressive inspections
  • Flight inspections

These are all important inspections that every aircraft owner should know.

What is a 50-hour inspection?

A 50-hour inspection, like a 100-hour inspection, is done every 50 flight hours. But unlike the latter, this kind of inspection mainly checks the engines. This is also when the oil should be changed.

However, this is largely an optional inspection in legalese. 100-hour inspections are required by the FAA, but 50-hour inspections are not.

There is also something called a 25-hour inspection for some aircraft like the Flugzeugbau EA 300, which require more frequent servicing if used more often. This inspection is basically the same as the 50-hour inspection, but done in more frequent intervals.


What is a pre-flight check?

Pre-flight checks are performed every time before the aircraft takes flight. This is mainly a visual inspection on the aircraft’s parts to ensure that it can fly safely without anything failing mid flight.

This also includes:

  • An inspection of the aircraft’s controls
  • Examining the fuel tanks for any issues
  • Making sure all important flight documents are inside the cockpit

Pre-flight checks are taught in pilot school. Furthermore, anyone who can fly a plane must do their own checks in order to keep them safe.


What is a post-flight check?

When the plane has touched down, stopped, and the engines asleep from all the flying, pilots should do their post-flight checks on their aircraft. Like the pre-flight check, this is a visual inspection of parts and components that might have broken down while flying. 

Exteriors should be checked, with special attention for things like whether they have new holes, or insects or other debris that might be hard to wash off the day after. This also makes the pre-flight check much easier come the next flight.

What is an ABCD check system?

The ABCD check system, unlike the others, is actually a series of checks on larger aircraft. This is usually reserved for the huge commercial planes and turbine-powered rotorcraft that go under MRO sites.

MRO stands for:

  • Maintenance
  • Repair
  • Overhaul

Aircraft can be sent to these sites to get new parts installed and old parts repaired whenever needed. They usually form as a part of an aircraft maintenance company, unless they operate as their own MRO site.

What are progressive inspections?

A practical alternative to 100-hour inspections, progressive inspections are basically 100-hour inspections done in phases. Mechanics can make a plan for a specific aircraft, detailing which parts will be checked and when.

When all parts of the aircraft have been inspected, the progressive inspection will be marked as accomplished. Then the next set of progressive inspections will begin.

However, progressive inspections are non-transferrable. If you happen to sell your aircraft to someone else, that aircraft will be subject to the 100-hour inspection requirement all over again.

What are flight inspections?

Flight inspections, unlike the other aircraft inspections in this list, are inspections on the things that help guide the aircraft as it goes around in the air. This includes the air traffic control towers that keep the things in the air from crashing into each other.

This type of inspection also includes flight instruments, like the landing aids pilots use to see the runway at night. There is less of a focus on the aircraft itself in this and more on the things that help it fly safely.


Conclusion: What to do after your annual aircraft inspection 

Flying an aircraft is not all just about getting up there in the sky among the clouds and the stars. It is also about making sure that the aircraft is perfectly safe and airworthy. 

Broken parts should be replaced. Flight systems must be calibrated. Anything that might cause an emergency breakdown in the middle of a flight should be made in a way that they never do – or at least, not while flying.

But then, after all has been done and inspected, you might want to upgrade your aircraft’s interior design. Being safe is one thing, but being comfortable is another. Southern Air Custom Interiors has all of the safest, top-of-the-line interior designs for all things aircraft.
Whether it’s the tight seat that doesn’t fit right or the lack of design making everything bland, there’s always a solution for you. To learn more about how we can help maintain your plane’s airworthiness, please feel free to contact us anytime to get a quote for its next thorough inspection!

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