Early in training a pilot learns to check an airplane's paperwork during the preflight inspection. The mnemonic checklist AROWS is a good reminder of the four essential documents that must be current and in the airplane - Airworthiness certificate, Registration, Operating limitations, Weight and balance data, and Supplemental type certificates (STCs), if applicable. If any of these documents are missing, the airplane is not legally airworthy, but the real issue is whether a problem that affects the safety of flight might be lurking in the dark recesses of the aircraft.
Airworthiness, Annuals, and ADs
An airworthiness certificate displayed prominently in the cockpit doesn't guarantee the airplane is truly airworthy and safe to fly. For the certificate to be valid the airplane must have at least a valid (current) annual inspection.
An airframe and powerplant mechanic with an inspection authorization (A) inspects the airframe, engine, propellers, controls, wings, brakes, hoses, accessories, etc., thoroughly and signs off the inspection, which is valid for 12 calendar months. If the airplane flies for compensation or hire, it must have a valid 100-hour inspection within the past (you guessed it) 100 operating hours. An A can perform this inspection, which is similar to an annual but not as comprehensive.
Like a pilot's medical certificate, the annual and 100-hour inspections are a snapshot of the airworthiness picture taken at the time of the inspection. The mechanic endorsing the inspection in the airplane's logbook certifies that the aircraft is airworthy at that time. Like a human, an airplane's health can change from day to day, or even hour to hour. In part, this is one reason why we perform the preflight inspection, but we should be aware that the airplane needs other, specific maintenance actions.
One way the FAA keeps owners, mechanics, and pilots current on required maintenance issues is with the Airworthiness Directive, or AD. It's important and has its own part in the FARs, which usually isn't included in commercial compilations of the regulations. Briefly, Part 39 says that we can't operate an aircraft to which an AD applies unless we comply with the requirements of that AD.
ADs differ significantly. Some require a one-time inspection or modification. Others require a periodic inspection or part replacement. An AD might apply to all aircraft of a certain make or model, or only certain aircraft within a range of serial numbers. It may apply to all aircraft that have a certain component, such as a particular engine, propeller, or accessory. The point is, just because an aircraft has a valid annual inspection doesn't mean it's airworthy today. For example, if the deadline for a recurring AD passes without compliance six months after the airplane's annual inspection, the airplane isn't airworthy.
Checking an airplane's compliance with its ADs isn't something a pilot normally does, especially if renting airplanes. But it's not a bad idea to confer with the owner or a mechanic about ADs that apply to the aircraft you fly periodically. Often, an AD compliance table is part of the aircraft maintenance records, and you can get an idea about when recurring ADs are due by studying the table. Many flight schools keep a table that lists the required inspections, maintenance, and ADs, when they were completed - and when they are due - in their aircraft.
Additional Inspections
To fly IFR, above 10,000 feet MSL, within 30 miles of a Class B airport, or in Class A, B, and C airspace, an aircraft must have some additional inspections. To fly IFR, the airplane's VOR receivers must have been checked for accuracy within the past 30 days in accordance with FAR 91.171, "VOR Equipment Check for IFR Operations." To fly in airspace where a transponder and/or Mode C altitude-reporting equipment is needed, within the preceding 24 months the transponder and pitot-static system must have been tested and certified in accordance with FAR 91.411, "Altimeter Systems and Altitude Reporting Equipment Tests and Inspections," and FAR 91.413, "ATC Transponder Tests and Inspections."
Finally, unless the aircraft is used for training only within a 50-mile radius of the airport, it must have an emergency locator transmitter, and the ELT's battery must meet the requirements spelled out in FAR 91.207, "Emergency Locator Transmitters." In addition, this regulation requires an ELT to be inspected every 12 months for proper installation, battery corrosion, proper operation, and that it transmits an adequate signal from the antenna.
Maintenance Records
Now that we've sorted through the inspection requirements, how do we know whether they've been done? The answers are in the aircraft maintenance logs. FAR 91.405(b) requires each owner or operator to "ensure that maintenance personnel make appropriate entries in the aircraft maintenance records indicating the aircraft has been approved for return to service." Any maintenance performed on an aircraft must be documented in the appropriate aircraft logbook.
A particular airplane may have several logs such as aircraft, airframe, engine, or propeller. Within their pages, we find the endorsements, which include the date the work was performed, certifying the required inspections and ADs were completed. The VOR check is a notable exception. Pilots check the VORs and this record often is kept in the cockpit.
Who's Responsible?
It's easy for pilots to believe that the owner, operator, or mechanic is responsible for ensuring an aircraft airworthiness. But FAR 91.7, "Civil Aircraft Airworthiness," says otherwise - "No person may operate a civil aircraft unless it is in an airworthy condition" and "the pilot in command of a civil aircraft is responsible for determining whether that aircraft is in condition for safe flight."
"Far too often, pilots get upset when we try to explain their responsibility with regard to airworthiness, but nobody has more to lose than the pilot if an aircraft is poorly maintained," says Bob Martens, Aviation Safety Program Manager at the Bradley, Connecticut, Flight Standards District Office.
First, the FAA can violate a pilot for not complying with regulations, an action that puts a hard-earned pilot certificate on the line. More significant is the liability issue. Often, an airplane's insurance policy stipulates that it will provide "no coverage if the aircraft is operated in-flight with your knowledge and consent, knowing its airworthiness certificate is not in full force." In other words, if an airplane has an accident and it's not airworthy, the policy holder might be left holding the financial bag.
Finally, we have the safety issue. Regulations and airworthiness requirements are written in blood, based primarily on the conclusions drawn from accident investigations. An unairworthy aircraft may well be an unsafe aircraft.
"There is some good news," says Martens. "Maintenance-related causes of aircraft accidents are way down." Still, with the legal, financial, and liability issues surrounding the topic of airworthiness, we can't afford to ignore our responsibility to ensure our aircraft is truly airworthy every time we fly.
