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Is Your Airplane IFR Legal?

by H. Dean Chamberlain
Reprinted with permission from FAA Aviation News

How do you know? In today's GPS world, do you still think about using the VOR navigation system anymore? Most IFR approved GPS systems installed today were approved under Technical Standard Order (TSO)-C129a for supplemental use. This supplement use limitation requires alternate navigation equipment to be available onboard the aircraft. As noted in the Aeronautical Information Manual (AIM), as long as your GPS uses RAIM for integrity monitoring, you don't have to be actively monitoring your alternate navigation equipment, but if you lose RAIM or if RAIM is predicted to be lost, you must use your alternate equipment. That other equipment might be your VOR. If you have VOR capability, and most airplanes that file instrument flight rules (IFR), probably have at least one onboard, when was the last time you checked its accuracy? More importantly, if you did check its accuracy, did you enter the required check correctly in a reliable record? Of if someone else made the entry, is it correct? If you rent the aircraft you fly, do you routinely check its paperwork for currency? No, I am not talking about the required 24-month checks for its transponder and static system, as appropriate. Nor am I talking about the annual inspection of its emergency locator transmitter (ELT), if so equipped. I am asking if you check that its annual inspection is current. Do you know if the aircraft has to have a 100-hour inspection? If so, is the 100-hour inspection current? Can a 100-hour inspection cover a 105-hour period? Is so, how? If the aircraft has an FAA-approved IFR GPS installed, does it have a current database if you use it IFR? If so, was a proper record made of the data base installation? Finally, if the aircraft is legal, are you legal to be pilot in command?

These are important questions. I think most of us tend to forget the important issues involved in these questions. Obviously, flight safety is the most important. However, failure to properly record the results of these inspections can result in enforcement actions against the pilot in command for operating a non-airworthy airplane, as well as exposing the aircraft owner or operator to possible enforcement action as well as possible insurance problems in the event of an accident.

In researching the proper format for recording a VOR operational check, which is found in Title 14 Code of Federal Regulations (14 CFR) '91.171, VOR equipment check for IFR operations, I thought this would be a good time to review the VOR requirements for operating a civil aircraft under IFR using the VOR navigational system. In describing how a VOR system can be checked, subsection (2) of that regulation states, 'Has been operationally checked within the preceding 30 days, and was found to be within the limits of the permissible indicated bearing error set forth in paragraph (b) or (c) of this section.'

The rule then lists the permissible errors. In summarizing those errors, at the departure airport using an approved radiated VOR test signal or designated ground test point, a maximum error of plus or minus four degrees. A maximum of plus or minus six degrees of error is permissible using an airborne procedure as outlined in the rule. Using the procedure outlined in the regulation for checking one independent VOR receiver against a second unit in the aircraft permits a maximum of plus or minus four degrees as acceptable. The regulation provides complete details for doing the respective type of tests. [The appropriate FAA Airport/Facility Directory for your area lists VOR receiver checkpoints and VOR Test Facilities (VOT) you can use for the checks.]

The key to your use of an aircraft using a VOR system for IFR flight is contained in subsection (d) of the rule. That subsection states in part, 'Each person making the VOR operational check, as specified in paragraph (b) or (c) of this section, shall enter the date, place, bearing error, and sign the aircraft log or other record.' If a test signal is used as part of the test, there is a record requirement for the test signal.

If there is an FAA-approved IFR GPS installed in the aircraft, do you know who is authorized to update the database? Are you? Once the database is updated, do you know how to check if the signoff was done correctly? If not, you might want to review 14 CFR parts 43. The authority to update the GPS data base is contained in Appendix A to Part 43, Major alterations, major repairs, and preventive maintenance, subsection (c) Preventive maintenance (32). Subsection 32 says, 'Updating self-contained, front instrument panel-mounted Air Traffic Control (ATC) navigational software data bases (excluding those of automatic flight control systems, transponders, and microwave frequency distance measuring equipment (DME)) provided no disassembly of the unit is required and pertinent instructions are provided. Prior to the unit's intended use, an operational check must be performed in accordance with applicable sections of part 91 of this chapter.'

Part 43 explains who may conduct the operational check and how the results of that check must be recorded.  The following are excerpts from part 43. Anyone interested in performing any of work outlined in part 43 must review the entire contents of the rule to ensure compliance. These excerpts are only intended to provide a quick overview of the rule. If you are a sport pilot or the work involves a light-sport category aircraft, you need to review the rules that apply to sport pilots or light-sport aircraft.

Q. Can a pilot perform preventive maintenance?

A. Yes. 'The holder of a pilot certificate issued under Part 61 may perform preventive maintenance on any aircraft owned or operated by that pilot which is not used under Part 121, 129, or 135.'

Q. What is involved in approving an aircraft for return to service after performing preventive maintenance?

A. Section 43.5, Approval for return to service after maintenance, preventive maintenance, rebuilding, or alteration, states in part, 'No person may approve for return to service any aircraft, airframe, aircraft engine, propeller, or appliance, that has undergone maintenance, preventive maintenance, rebuilding, or alteration unless' (a) The maintenance record entry required by Sec. 43.9 or Sec. 43.11, as appropriate, has been made.'

Q. Who can approve an aircraft to return it to service?

A. Sec. 43.7, Persons authorized to approve aircraft, airframes, aircraft engines, propellers, appliances, or component parts for return to service after maintenance, preventive maintenance, rebuilding, or alteration, states in part, 'A person holding at least a private pilot certificate may approve an aircraft for return to service after performing preventive maintenance under the provisions of Sec. 43.3(g).' Section 43.7(g) and (h) explain what sport pilots and holders of a repairman certificate (light-sport aircraft) with a maintenance rating may do concerning light-sport aircraft.

Q. What must the required record contain?

A. Sec. 43.9, Content, form, and disposition of maintenance, preventive maintenance, rebuilding, and alteration records (except inspections performed in accordance with part 91, part 123, part 125, Sec. 135.411(a)(1), and Sec. 135.419 of this chapter), states in part, (a) Maintenance record entries. Except as provided in paragraphs (b) and (c) of this section, each person who maintains, performs preventive maintenance, rebuilds, or alters an aircraft, airframe, aircraft engine, propeller, appliance, or component part shall make an entry in the maintenance record of that equipment containing the following information: (1) A description (or reference to data acceptable to the Administrator) of work performed. (2) The date of completion of the work performed. (3) The name of the person performing the work if other than the person specified in paragraph (a)(4) of this section. (4) If the work performed on the aircraft, airframe, aircraft engine, propeller, appliance, or component part has been performed satisfactorily, the signature, certificate number, and kind of certificate held by the person approving the work. The signature constitutes the approval for return to service only for the work performed.

Although the above information may be more than you wanted to read, the information provides the regulatory basis for performing the required operational checks for VOR and installing a data update to a GPS system.

For more information about all types of repairs, you should check the various appendixes to part 43, which define what are major repairs, major alterations, preventive maintenance, and the various types of inspections. Part 43 also provides definitions of the various types of maintenance and who is authorized to perform that maintenance.