person must have an ELT attached to the airplane. 14 CFR  part 91, section 91.207 defines the requirements of what type  aircraft and when the ELT must be installed. It also states that  an ELT that meets the requirements of Technical Standard  Order (TSO)-C91 may not be used for new installations. The pilot in command of an aircraft equipped with an ELT is  responsible for its operation and, prior to engine shutdown at  the end of each flight, should tune the VHF receiver to 121.5  MHz and listen for ELT activations. Maintenance personnel  are responsible for accidental activation during the actual  period of their work. Maintenance of ELTs is subject to 14 CFR part 43 and  part 91, section 91.413 and should be included in the  required inspections. It is essential that the impact switch  operation and the transmitter output be checked using the  manufacturer’s instructions. Testing of an ELT prior to  installation or for maintenance reasons, should be conducted  in a metal enclosure in order to avoid outside radiation by the  transmitter. If this is not possible, the test should be conducted  only within the first 5 minutes after any hour. Manufacturers of ELTs are required to mark the expiration  date of the battery, based on 50 percent of the useful life, on  the outside of the transmitter. The batteries are required to be  replaced on that date or when the transmitter has been in use  for more than 1 cumulative hour. Water activated batteries,  have virtually unlimited shelf life. They are not usually  marked with an expiration date. They must be replaced after  activation regardless of how long they were in service. The battery replacement can be accomplished by a pilot on  a portable type ELT that is readily accessible and can be  removed and reinstalled in the aircraft by a simple operation.  That would be considered preventive maintenance under  14 CFR part 43, section 43.3(g). Replacement batteries  should be approved for the specific model of ELT and the  installation performed in accordance with section 43.13.  AC 91-44 also contains additional information on: Although there is no regulatory requirement to install a 406  ELT, the benefits are numerous, regardless of regulatory  minimums. All new installations must be a 406 MHz digital  ELT. It must meet the standards of TSO C126. When  installed, the new 406 MHz ELT should be registered so that  if the aircraft were to go down, search and rescue could take  full advantage of the benefits the system offers. The digital  circuitry of the 406 ELT can be coded with information about  the aircraft type, base location, ownership, etc. This coding  allows the search and rescue (SAR) coordinating centers to  contact the registered owner or operator if a signal is detected  to determine if the aircraft is flying or parked. This type of  identification permits a rapid SAR response in the event of  an accident, and will save valuable resources from a false  alarm search. An owner/operator bringing an aircraft into a maintenance  facility for an annual or 100-hour inspection may not know  what is involved in the process. This is the point at which  the person who performs the inspection sits down with the  customer to review the records and discuss any maintenance  issues, repairs needed, or additional work the customer may  want done. Moreover, the time spent on these items before  starting the inspection usually saves time and money before  the work is completed.  The work order describes the work that will be performed  and the fee that the owner pays for the service. It is a contract  that includes the parts, materials, and labor to complete the  inspection. It may also include additional maintenance and  repairs requested by the owner or found during the inspection.  Additional materials such as ADs, manufacturer’s service  bulletins and letters, and vendor service information must be  researched to include the avionics and emergency equipment  on the aircraft. The TCDS provides all the components  eligible for installation on the aircraft. The review of the aircraft records is one of the most important  parts of any inspection. Those records provide the history  of the aircraft. The records to be kept and how they are to  be maintained are listed in 14 CFR part 91, section 91.417.  Among those records that must be tracked are records of  maintenance, preventive maintenance, and alteration, records  of the last 100-hour, annual, or other required or approved  inspections for the airframe, engine propeller, rotor, and  appliances of an aircraft. The records must include: •  Airborne homing and alerting equipment for use with  ELTs. •  Search and rescue responsibility. •  Alert and search procedures including various flight  procedures for locating an ELT. •  The FAA Frequency Management Offices, for  contacting by manufacturers when they are  demonstrating and testing ELTs. •  A description (or reference to data acceptable to the  FAA) of the work performed.  •  The date of completion of the work performed and  the signature and certificate number of the person  approving the aircraft for return to service. 2-63 Annual and 100-Hour Inspections Preparation 