When a person decides to buy a general aviation aircraft it is a very good idea to get a "prebuy" done before any money changes hands. The "prebuy" is one of the duties of the general aviation maintenance technician, although the technician is putting his or her neck way out on the line whenever accomplishing this task. The seller of the aircraft usually believes that the machine is in perfect condition and the buyer of the aircraft wants any discrepancies found in order to negotiate a better price. The general aviation maintenance technician's customer is the buyer and is charged to find any problems that exist or may exist in the near future.
We do not identify this as an inspection, as the FAA has no definition of a "prebuy inspection". There are annual inspections, 100 hour inspections, progressive inspections, 50 hour inspections but no prebuy inspection. There have been litigations against general aviation maintenance technicians for performing a prebuy inspection and missing something that showed up at a later date after the aircraft was purchased that cost the new owner more money than he expected. The prebuy is an abbreviated "lookover" of the aircraft and usually the buyer & seller are anxious to have the results quickly. There is a lot of pressure on the general aviation maintenance technician. The process is identified as a "prepurchase evaluation" since there is no published definition that can be used in a lawsuit. The best way to ensure an aircraft is airworthy is to accomplish an annual inspection and repair any unairworthy items.
We start the "prebuy" by walking around the aircraft and noting anything that is unusual: deteriorated paint, foggy windows, wrinkles in flight controls, hail damage, stange patches, torn or worn upholstery, etc. Next step is to run the engine to check the engine, radios and instruments operation. A cylinders compression test will give an indication of how strong the engine is and check for cracks, piston rings condition, exhaust and intake valves condition. The oil filter is removed, cut open and visually inspected for signs of oil contamination. With experience, much can be identified by what is in an oil filter-aluminum, brass, iron, carbon all tell a story of what is happening inside of the motor. Usually by now, one can tell if the "prebuy" should continue. If too many problems have been seen at this point, it is better to stop, tell the buyer that this is going to be a "project" airplane and to find another aircraft to evaluate. We have had to do this many times. The buyer thanks us and the seller condemns us for being too picky.
If the aircraft looks promising, the engine is visually checked for leaks, chafes, controls rigging, exhaust leaks, etc. The airframe is checked for fuel leaks, hydraulic leaks, lights are checked along with other systems such as pitot heat, stall warning, etc. Tires and brakes are looked at for wear. If the landing gear is retractable, the aircraft is jacked and the landing gear operation is checked. Flight controls hinges are checked for excessive wear and controls movement is checked. Key inspection panels are removed for evaluation of structure for internal corrosion.
Instruments faces and indicators will be looked at and under the instrument panel will be checked for any obvious defects. Is there any corrosion around the aircraft battery and battery box? Do ventilation and avionics cooling fans operate normally? Does the magnetic compass have any air inside and is the deviation card current? Are the Pilot's Operating Handbook, Airworthiness & Registration Certificates present? Do the brake master cylinders have any leaks?
The aircraft records are checked to determine if there is any record of major repairs that have been made (damage history), is the total time of the aircraft, engine and propeller correct and are all of the applicable Airworthiness Directives current? If any modifications have been made to the aircraft, were they properly documented with appropriate weight & balance calculations?
The annual inspection includes all of the items described above and is much more detailed in scope and detail. Due to time and money constraints, an annual inspection is not normally complied with as a prepurchase evaluation although the buyer often requests the "prebuy" be extended into a full annual inspection if he decides to purchase the aircraft.
Once the evaluation is complete, both the buyer and seller are normally informed of the results. The buyer will undoubtly want a dollar amount to repair any "airworthy" discrepancies. The buyer then takes this dollar amount to the seller for price negotiations.
The general aviation maintenance technician must stress to the buyer that there are no guarantees as to the results of the prepurchase evaluation as a complete inspection has not been performed. An experienced technician can normally tell if a particular aircraft is a "good one" pretty quickly. Buying a general aviation aircraft is usually an emotional event, especially for a person who just got his pilot's license. There have been people that have disregarded our advice, purchased an inferior aircraft and their wallets have suffered as a consequence.