Slick Magnetos: Overhauled vs. Rebuilt
Rebuild and overhaul are two terms frequently used to describe the condition of an aircraft part. In fact, the two are often used interchangeably. Because of this, people see rebuilt parts and overhauled parts as the same, and find themselves wondering why rebuilt units cost more. However, the truth of the matter is that rebuilt and overhauled parts are different, and refer to different levels of work performed. If a part is ‘overhauled,’ it means that it has been completely disassembled, examined, and parts have been replaced as necessary according to the manufacturer’s overhaul manual. If a part is ‘rebuilt’ it means that the part has been brought back to factory new conditions as per the manufacturer.
To further highlight the differences between an overhauled and rebuilt part, let’s examine a specific part: the slick magneto. There are certain components of a magneto that must be replaced during both the overhaul and rebuild process. These include the points, capacitor, oil seal, rotor gear, and impulse spring. However, the differences begin with the coil, impulse coupling assembly, block, and gear. During a rebuild, all of these items must be replaced with new parts in every single rebuild. However, during an overhaul, additional parts may require replacement depending on conditions as determined during inspection of the magneto.
For the coil, the extent of inspection is checking for visible radial cracks and testing for primary and secondary circuit resistance and continuity in accordance with the manufacturer’s part manual. Testing the resistance and continuity of the coil is both objective and easy to see when the part is outside the acceptable range. However, visual inspection of a part for cracks ultimately comes down to a subjective judgement call, making things more difficult. The same issues arise when inspecting the impulse coupling assembly, block, and gear. These inspections are based on a human technician visually checking for cracks, rust, pitting, damage, or loose parts using procedures set forth by the part’s manual. As such, they ultimately rely on the technician’s opinion and insert subjectivity into the overhaul process of the magneto.
Further complicating the overhaul process is when the manual states that all parts removed for overhaul replacement should be discarded and replaced with new parts. This can make the process more difficult because different vendors use different manuals, some of which allow for the use of serviceable parts rather than new. This can be problematic, as serviceable parts cannot always be authenticated and may have been subjected to unacceptable conditions despite still being considered serviceable. When unsure about the condition of the parts being used in the magneto, the best solution is to go with a rebuilt magneto. That way, you can be certain you are getting a product with brand new parts.
In conclusion, the differences between the rebuild and overhaul process are clear. In a rebuild, the magneto is replaced with new parts no matter the situation. The overhaul process allows for interpretation and is often replaced with serviceable parts rather than brand new. To determine the ideal process for your situation, consult the part’s manufacturer manual, and when buying parts, ensure you are getting them from a reputable source.
For overhauled & rebuilt parts and much more, look no further than ASAP Aviation Unlimited, a trusted supplier of parts for a wide range of industries. Owned and operated by ASAP Semiconductor, we are an online distributor of aircraft parts as well as parts pertaining to the aerospace, civil aviation, defense, electronics, and IT hardware markets. We’re always available and ready to help you find all the parts and equipment you need, 24/7-365. For a quick and competitive quote, call us at 1-714-705-4780 or email us at sales@asapaviationunlimited.com.
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