Aviation is one of the most regulated industries on the planet. The FAA has numerous different certificates covering almost every aspect of aviation, among them being the Part 145. So what exactly is a Part 145 in aviation?

A Part 145 in aviation is a certificate that enables an organization (referred to as a Part 145 organization) to carry out certain maintenance on FAA-registered aircraft. 

The work that can be carried out depends on the General Maintenance Ratings granted by the FAA, and different Part 145 organizations often specialize on different aircraft types, much like some auto mechanics do.

What is A Part 145 in Aviation?

Due to the controlled nature of the aviation industry, a part 145 organization can’t just do any work they please on an aircraft. There are requirements that must be met, as defined by 14 CFR Part 145. 

Due to the sensitive nature of aircraft maintenance, the organization applying for a Part 145 certificate must satisfy the FAA that they meet the standards laid out in the regulation. There are many things the FAA must consider when granting a Part 145 Certificate.

Part 145 organizations often handle not only strictly regulated aircraft parts but dangerous goods as well. Aircraft batteries, paints, solvents, and high-pressure gasses are a few examples. For this reason, the organization must have all the right safety checks and balances in place.

Maintenance events often happen during operation – the pilot may notice an engine’s performance deteriorate, and bird strikes are also common occurrences. The maintenance team must be called in to assess the situation, and determine whether the aircraft is still safe.

What Does A Part 145 Organization Do?

As a passenger, you might worry when you see a technician busying himself around your ride. He might just be there to ensure the aircraft is in a safe condition for flight, and will usually keep a watchful eye until the aircraft taxis off to the runway.

Airplane inspection in Melbourne Australia
Yay Airplane inspection in Melbourne, Australia

The technician is essentially representative of Part 145. To be present at the aircraft, he must be working under the approval of the Part 145 organization maintaining that aircraft and be carefully vetted with the appropriate FAA license to do his job.

A technician will communicate with the flight deck and cabin crew, and resolve any defects recorded in the aircraft technical logs using their feedback and his own knowledge. Many small problems can be resolved between flights without causing any delays.

Bigger problems might necessitate returning the aircraft to a maintenance facility, and it’s usually the technician that makes this call.

The pilot has the final say, in the end – if they do not feel the aircraft is safe, they can legally refuse to accept the aircraft, even if the technician disagrees with that assessment.

What Are General Maintenance Ratings?

General maintenance ratings granted by the FAA are Airframe, Power plant, Radio, Instrument, Propeller, and Accessory. There are further subdivisions within these ratings, ensuring that Part 145 organizations do not attempt work that they are not equipped for.

airline mechanic working
Yay Airline mechanic working

Some of the larger operations handling large commercial fleets may have a much wider range of capabilities due to the fact that they have access to advanced specialized equipment and processes, often through agreements with manufacturers.

A smaller company might only hold approval to carry out the overhaul of a specific component. Someone who exclusively overhauls hydraulic pumps isn’t going to need a propeller or instrument rating.

The regulations are written to accommodate companies and operations of every size.

What Are Part 145 General Maintenance Ratings?

To simplify things, you will find a brief summary of each maintenance rating and its subdivisions. For more detailed information, you can look at the relevant regulation.

Airframe Ratings: There are 4 different airframe classes. Classes 1 and 2 are for light and heavy composite aircraft, while classes 3 and 4 are for light and heavy airplanes constructed out of metal. The weight ratings are defined in 14 CFR 145, the Federal regulation that governs maintenance organizations.

Powerplant Ratings: There are 2 classes for reciprocating engines – Class 1 below 400HP and class 2 above 400HP. Turbine engines have their own rating, Class 3.

Propeller Ratings: Aircraft propellers are complex, critical components and as such require their own rating. Class 1 for fixed pitch, ground adjustable propellers. Class 2 is for variable pitch propellers.

Radio Ratings: These ratings allow a part 145 organization to carry out work on aircraft communication, radar, and navigational systems. These systems are essential so airplanes can talk to each other as well as to air traffic control. They also assist the pilot in maintaining a true flight path.

Instrument Ratings: Aircraft instrument systems are highly complex, giving the pilot essential information to ensure safe aircraft operation. There are 4 classes – mechanical, electrical, gyroscopic, and electronic. Each of these different systems requires specific expertise and often highly specialized equipment.

Accessory Ratings: Accessory is a catch-all phrase for a number of complex aircraft components. These can be mechanical, electrical, or electronic in nature and, as such, Accessory ratings have 3 separate classes. These can be electrically or mechanically driven pumps, valves, fuel control units, and a seemingly endless amount of other items.

Part 145 Organizations Handling Dangerous Goods

Aircraft batteries, solvents, hydraulics, and paints are all examples of dangerous goods. In Part 145 organizations, dangerous goods are often referred to simply as DG. A Part 145 maintenance organization is likely to require several kinds of DG for its operation. 

There are countless other goods that can be defined as dangerous in some way or another – some can even be radioactive! Part 145 organizations are responsible for training their personnel to handle any DG they might encounter.

Radiation warning sign on the Dangerous goods transport
Yay Radiation warning sign on dangerous goods transport

Where applicable, the FAA will assess the organization’s capabilities and procedures when dealing with dangerous goods. They must be stored, used, and disposed of in a safe manner. 

The FAA is invested in the safety of personnel, civilians, and the environment. As such, the procedures for handling dangerous goods will be closely scrutinized. Personnel need to be appropriately trained and must have the correct equipment. 

What Are Dangerous Goods Used For In Aviation?

It might surprise you just how many different kinds of dangerous goods there are. You are likely to encounter a variety of them in even a modest aircraft operation.

High-pressure nitrogen inflates tires and shock struts, oxygen for emergency systems, hydraulic fluids used by the landing gear and flight controls, oils lubricating the engines, and even the Jet-A1 or Avgas fuel used to power airplanes are commonly used aviation consumables that are considered dangerous goods.

All dangerous goods have to be treated and stored according to their specifications. They might require a controlled temperature, ventilation, and fire protection to be stored safely.

A Part 145 organization will have to prove that they are trained and equipped to handle and store any DG required for their operation.

Contrary to what many believe, a Part 145 organization does not have to be equipped to deal with all types of DG.

For the most part, organizations need to be equipped to handle the dangerous goods they will be using on a regular basis, and at least have procedures for identifying and reporting anything outside of their capabilities.

How Are Dangerous Goods Handled In Aviation?

Safety is a concern not just for part 145 organizations, but for everyone in aviation.

Within Part 145 organizations, it is generally seem as everyone’s responsibility to be alert and report anything they think is out of place.

This is especially true where dangerous goods are concerned because they can be used in attacks on airplanes, passengers, and personnel, or could lead to other aviation-related incidents if not properly reported.

Each of the 9 classes of dangerous goods has its own handling, shipping, and storage requirements. It can even be dangerous to store some items together, so special care must be taken to follow manufacturer storage instructions.

Chemical reactions might occur between improperly stored goods, and can release poisonous gasses, and cause fires and even explosions.

The general rule among most Part 145 mechanics is that if you don’t know what it is or how to handle it – do not touch it and report it instead.

Repair Station and Quality Control Manuals for Part 145

Each aspiring Part 145 organization is required to have various internal documents outlining its processes and procedures across the operation. FAA AC-145-9A guides operators in creating their manuals.

Every Repair Station Manual and Quality Control Manual will be as unique as the organization. These documents are submitted to the FAA for approval when applying for the Part 145 certificate.

Repair Station Manual

Repair Station Manuals are intended to outline all the processes and procedures relating to the maintenance and repair of aircraft and aircraft components. It will be tailored to the company’s needs – there is no one-size-fits-all approach due to the diverse nature of these organizations.

From storage procedures like shipping, handling, and receiving of parts, to maintenance procedures such as raising defects, ordering spares, and carrying out maintenance, this document will have all procedures relating to the Repair Station’s operations. 

The Repair Station Manual will be available to all personnel at the Repair Station and is usually an internal document for use exclusively by that company. No matter where a technician is working, they will know to refer to the Repair Station Manual to guide them in their work.

These documents tend to change over time. Regulations can sometimes change, and these changes need to be incorporated by companies into their documentation. 

A company might also wish to change its processes and will need to have any amendments to these manuals approved by the FAA to ensure that they continue to meet the standards laid out in the regulations.

Quality Control Manual

Quality Control is such a vital component of maintaining aircraft that each Repair Station is required to have its own FAA-approved Quality Control Manual.

There is more to quality control than double-checking people’s work and ensuring it meets a standard. Defects and faults must be reported and tracked. The correct tooling, consumables, and equipment must be used, with no exceptions.

aviation maintenance technician working on engine
Yay Aviation maintenance technician working on engine

A Quality Control manual is another essential document that codifies an organization’s response to any maintenance concerns, be it sloppy paperwork or a recurring problem. 

There are often separate safety management systems and manuals that tie in with Quality Control, but in the context of Part 145 QC is mainly concerned with trends and patterns. 

A Quality Control person might recommend training for individuals that are not meeting the work standards, keeping them in line with company and federal standards. This all goes towards ensuring that aircraft are safe to fly.

Safety Reporting

Safety Reporting is something that is discussed tirelessly in the context of aviation. It is roughly defined as communicating absolutely any hazard or threat to others.

Each company is required to have a safety management system so that employees know exactly what to do when they identify a hazard. There is usually a carefully defined system with either an individual or a team responsible for monitoring it, depending on the size and complexity of the operation.


Related Article:
Safety Management Systems (SMS) in Aviation

What Is A Hazard

A hazard can be anything that has the potential to cause harm to people or property. A slippery floor, exposed electrical cables, and even risky yet seemingly innocent behavior like horseplay and pranks in and around an aircraft are examples.

Even small hazards should be reported because it’s usually a combination of small factors that leads to accidents and incidents occurring in aviation.

The Difference Between an Incident and an Accident

When encountering safety management systems in aviation, one might get confused by all the different types of events, namely accidents and incidents. 

An incident is any unexpected event that threatens the safety of personnel, equipment, or airplanes. An accident is when the event causes harm or loss and is considered more severe than an incident.

Why Is Reporting Important?

The FAA and its regulations are intended to maintain safety in the skies. This is what all the regulations come back to, in a sense. To fly an aircraft safely, you must first have a safe aircraft. This is why Part 145 is so critical in aviation.

There are many cautionary tales, some well-publicized, about poor maintenance causing incidents and accidents in the world of aviation. Some of these examples are unspeakable tragedies, sometimes caused by negligence and more often than not caused by human error.

It all comes back to safety. Incidents do not usually occur in isolation. They need to be reported, communicated, analyzed, and dealt with. A seemingly minor problem can have far-reaching consequences.

Do Other Countries Have Part 145?

The regulations surrounding aircraft maintenance in the form of the Part 145 is not something unique to the US or the FAA. In fact, most countries have some equivalent of the Part 145.

In Europe, the EASA awards it own Part 145 certificate, which follows regulations nearly identical to those enforced by the FAA, albeit for aircraft registered in countries regulated by the EASA.

Likewise, the UK, through the CAA, issues a Part 145 certificate (historically acquired and issued in tandem with the EASA, owing to overlapping regulatory zones) which concerns the mainland UK and Channel Islands.

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About the Author

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Salomon Marco
Salomon has been interested in aviation ever since his parents took him on a Boeing 720 to see his relatives. When he’s not writing his latest aviation article, he can be found planespotting, reading up on on aviation news or in the cockpit of his favorite aircraft!