New meaning to the phrase 'Ready to fly'
Piston-engine aircraft maintenance requirements are relatively simple: Change the oil, comply with an occasional airworthiness directive, get an annual, and fix it when it breaks. But with turbine-powered aircraft the requirements are a bit more demanding and detailed. Multiengine turbine-powered airplanes are subject to different rules for inspections and for tracking life-limited items. Because of the additional maintenance required for turbine-powered aircraft, it is important to understand the concept of airworthiness and who is responsible for ensuring it.
The FAA does not define the word airworthy in FAR Part 1 where all the other definitions are located. Instead, it has chosen to submerge the definition of this key term within the Airworthiness Inspector's Handbook, legal opinions, and a very useful document, the FAA's Plane Sense. The definition provided below may seem a bit obscure, but it is quite significant. It means that the aircraft must conform to its originally certified design, as modified by supplemental type certificates and authorized field-approved modifications.
Affording It
Perhaps the most surprising difference between piston and turbine aircraft maintenance is the costs. While labor on a piston twin may run $60 per hour, a twin turboprop may cost $130 per hour. A $35,000 piston engine overhaul becomes $180,000 for a turboprop powerplant, and don't forget the required midlife turbine inspection at $30,000. Worse still, what happens if the engine decides to eat itself internally or is mortally wounded by an errant bird?
Maintenance insurance or cost management programs tend to reduce the shock value of major maintenance expenses by spreading them over the life of the airframe and engine. For a premium of about $80 per hour on a turboprop airframe, and a similar amount for an engine, many parts, labor, and overhaul costs are covered. While these maintenance expense accrual programs permit more rational financial planning, they all contain exclusions and conditions that should be carefully examined. — JJS
The second provision, regarding condition for safe operation, refers to the aircraft's (and its components') state of wear, tear, and conformance to maintenance regulations. While this second condition may seem a bit fuzzy, its intent should be clear: Minor dents, dings, and drips are OK; beyond that, everything's got to work and be properly inspected and maintained. More later on the concept of everything in the aircraft working.
Responsibility
While most of us are aware of Federal Aviation Regulation 91.403(a), it bears repeating: "The owner or operator of an aircraft is primarily responsible for maintaining that aircraft in an airworthy condition...." Many pilots mistakenly assign the responsibility for airworthiness to aircraft mechanics; yet, under the regulations, they are only responsible for performing their maintenance duties in conformance with prescribed methods and for approving the work performed for return to service. While most mechanics would not knowingly release an aircraft that was clearly unairworthy to an operator, their legal responsibility ends with ensuring that the performance of their work is in accordance with "methods, techniques and practices acceptable to the Administrator."
In practice, ensuring airworthiness requires a knowledgeable owner or operator working in concert with a mechanic who knows the aircraft in question. Yet, mechanics seldom see an aircraft between inspections and are therefore hardly in a position to know its condition; the burden for airworthiness clearly rests with the owner or operator. Ultimately, it is the pilot in command's responsibility to determine whether an aircraft is in condition for safe flight and therefore airworthy.
Maintenance records are also a shared responsibility. Each mechanic performing maintenance or an inspection must make appropriate entries called for in FAR Part 43. Part 91 also requires the owner or operator to ensure that maintenance personnel have made record entries after maintenance has been performed. Further, the owner or operator is required to keep some of the maintenance records for specified periods of time.
Care should be taken to ensure that required records are complete, correct, and neat. This is not for the benefit of any FAA inspector who may possibly see the records but for the owner to prove to the next owner that all required actions have been accomplished. If an owner cannot prove compliance with a particular airworthiness directive, inspection segment, service bulletin, or life-limited item requirement, the value of the aircraft is reduced because the missing item has to be redone. Similarily, sloppy or incomplete records also reduce the resale value of an aircraft. Therefore, a periodic review of the aircraft maintenance records by both owner and mechanic is an essential element of airworthiness and ensuring the resale value of the aircraft. And, since aircraft maintenance records are so important, keeping them in a safe place and even duplicating them makes good sense.
What's different?
Because of the complexity of turbine-powered aircraft they require more frequent inspections and preventive maintenance than do their piston-powered brethren. Therefore, the FAA requires compliance with replacement times for life-limited parts and a specific inspection program for multiengine turbine-powered airplanes. Several options are available to comply with this inspection requirement; however, most operators select an inspection program recommended by the manufacturer. While an operator may devise a program unique to a specific aircraft, the time and experience required to do so probably outweigh the benefit.
Chapter five of the manufacturer's maintenance manual specifies the maintenance and inspection schedule required for your aircraft, its engines, and component parts and appliances. This document provides a detailed description of the actions and intervals between those requirements. The intervals are expressed as hours of time in service, calendar intervals, or cycles, and are designated as Phase or Type inspections, normally occurring at 100- to 300-hour intervals. Because some of the intervals are based on the calendar it is important to note that maintenance may be required whether the airplane flies or not. Also important, the airplane may become unairworthy by just sitting in a hangar if required maintenance is not performed.
Go/No-Go Items
The following items must be complied with before the aircraft can be considered airworthy:
- No outstanding aircraft discrepancies unless deferred via an MEL.
- All required inspection items complied with.
- Life-limited items within limits.
- Airworthiness directives current.
- Manufacturer's mandatory service bulletins complied with (if manufacturer's maintenance and inspection program used).
Some airframe manufacturers offer several inspection programs designed to suit operators who use the aircraft either a lot or just a little. This is done to reduce the possibility of over-maintaining a little-used airplane or under-maintaining an aircraft that flies more than a normal amount, usually 400 to 600 hours per year. A number of manufacturers have instituted airline-style progressive inspections that permit blocks of inspection and maintenance items to be performed within a period of time while the airplane remains in service. This is done to minimize downtime on an airplane previously required to have these items accomplished while the aircraft was not in service for extended periods.
Turbine-powered aircraft usually contain a larger number of life-limited components that require some form of ongoing maintenance or inspection. Starter generators, landing gear components, flap drive gearboxes, oxygen bottles, and more may be subject to time limits. The turbine engine itself has a large number of life-limited components, mainly turbine and compressor disks. The service limits for these items may be found in chapter four or five of the associated maintenance manual.
Staying ahead
Since there are a number of interlocking maintenance, inspection, and replacement schedules to track, many operators subscribe to a maintenance record tracking service that provides a fully sequenced view of upcoming requirements. These systems are custom-tailored to your aircraft to provide exact intervals between required events. In addition to providing a "due" list for these events, they contain a database of installed major components, providing an installation history, serial number, and maintenance requirements. These services also keep their subscriber's database current with respect to the manufacturer's inspection and maintenance and FAA airworthiness directive requirements.
This tracking system is not the same as the aircraft and powerplant maintenance records required by the FAA; the system, however, may be used to satisfy the regulatory requirement that life-limited part replacement times are complied with.
A word of caution about maintenance record tracking systems: They are only as good as the information supplied to them. The data must be regularly updated as maintenance actions are performed, either via a local database or submissions to a remote database. The timeliness and accuracy of these inputs can mean the success or failure of the system; whoever keeps yours up to date must be conscientious enough to ensure its accuracy. Which brings us to who should work on your aircraft.
Getting it done
Because of the complexity of turbine aircraft systems and advanced troubleshooting techniques, knowledge and experience are important prerequisites for the individuals working on your aircraft. While some minor servicing and inspection items may be performed by many general aviation mechanics, most turbine aircraft maintenance tasks require experience with those aircraft and, in most cases, your specific type of aircraft. So, unless you are lucky enough to have a service center or repair station at your home base experienced with your aircraft, you may have to go elsewhere for maintenance.
Alternatively, you can invest in a local mechanic whom you trust by sending him or her to the manufacturer's maintenance school for your aircraft (normally five days for smaller turbine aircraft). While this does not qualify a mechanic to perform all required maintenance actions on your aircraft it cuts down on the number of trips to the aircraft service center. And a good mechanic can save big bucks on parts and other maintenance items by exercising a bit of curiosity and enterprise (see " Affording It," page 145).
Paperwork
All aircraft must be maintained using the methods, techniques, and practices prescribed in the current manufacturer's maintenance manual; this is especially true for turbine aircraft. Their complexity often requires unique maintenance methods and practices that are subject to change. Therefore, anyone who maintains your aircraft must subscribe to the manufacturer's maintenance manuals or to an information service that replicates them. This requirement is valid for the airframe, powerplant, and appliances supplied as original equipment and added afterward under a supplemental type certificate or field-approved modification.
Airworthiness directives and mandatory service bulletins for the aircraft and its installed components must be complied with as well. While maintenance record tracking systems are supposed to incorporate these requirements, some of these systems have been known to either overlook the inclusion of individual elements or not apply them in a timely manner. Compliance with required directives is the responsibility of the owner or operator, not the maintenance record tracker. Having a trusted mechanic to look after these details will pay dividends in the long run.
Discrepancies
When something breaks it must be fixed before the aircraft can legally fly again. While passenger convenience items may be left inoperative, virtually everything else in the aircraft must operate correctly for the aircraft to remain airworthy. The FAA has devised a minimum equipment list (MEL) for most turbine-powered airplanes that permits operation of the aircraft with some inoperative elements. For instance, under an MEL if the flap position indicator is inoperative the flight may be conducted if special flap operation and visual inspection procedures are followed. Or, if the airplane is to be operated below a specified altitude or airspeed the yaw damper may be inoperative. However, a specific letter of authorization must be obtained from the FAA in order to take advantage of an MEL.
All aircraft faults discovered by pilots should be written down in a discrepancy log and provided to the mechanic who corrects the discrepancy. When the mechanic repairs the fault the discrepancy log should reflect this action in order to inform the pilot of the corrective action taken. (The mechanic must also make a record entry in the FAA-required aircraft log stating the maintenance performed.)
Is it airworthy?
It's time to go fly; is the aircraft really airworthy? Determining this may seem complicated but it need not be. For the aircraft to conform to its type design and be in a safe condition to fly, three basic conditions must be met:
- All installed instruments and equipment (operational items) must be operable.
- All required maintenance, inspection, and life-limited items must be complied with.
- A visual inspection of the aircraft must verify that no defects exist.
While this may sound simple, the first two statements contain a number of elements. The first statement really means that the aircraft must operate as it did the day it received an airworthiness certificate; no outstanding or deferred discrepancies are permitted that would affect operation of the essential elements of the aircraft. If the elements noted above are complied with and a careful preflight conducted, the aircraft is about as airworthy as it will ever be.
While additional requirements are levied on turbine-powered aircraft owners, good recordkeeping and tracking systems provide the basis for demonstrating airworthiness. Concerned owners should understand both the FAA regulations and manufacturer's maintenance requirements to ensure a safe and legal operation. This is difficult to accomplish unless an experienced and conscientious mechanic, repair station, or service center is available to provide advice and counsel regarding these complexities.
John J. Sheehan is president of Professional Aviation Inc., which assists companies with air transportation analyses and flight departments with safety, management, and training issues. This article is based on a part of his new book, Business and Corporate Aviation Management, McGraw-Hill, New York. He holds an airline transport pilot certificate and an MBA degree. E-mail the author at [email protected].
