September 2005- The federal requirement for ELTs started out as a Congressional amendment to the OSHA act of 1970. A group of Senators were lost in an aircraft accident in Alaska and this was the catalyst for this amendment. The FAA was required by Congress to add to the FARs a requirement that most aircraft have ELTs installed by June of 1974.
Additional types of aircraft were recently added (effective January 1, 2004) to include turbojet aircraft. The original ELT specification was TSO C-9 1, updated to the current TSO C-91A.
During the early 1970s, there was a rush to manufacture ELTs and in the haste, a variety of problems were created by such causes as poor workmanship, substandard materials, improper testing and batteries of poor design and construction.
The biggest problem was that of batteries that caused fires and/or explosions due to shorted or leaking batteries. Faulty batteries led to additional problems of corrosive gas and or liquids spilling into the ELT, and onto aircraft structure.
As a stopgap measure several AD notes were issued in the 1972 to 1975 timeframe to cover different models of ELTs requiring battery replacements, or modifications or even replacements of some ELTs.
Many of the earlier ELTs were just plain unreliable. With this unreliable nature of the early ELTs and the availability of advanced electronics, reliable batteries and improved construction materials, the FAA issued a new TSO-C-91A in 1986 to address these problems.
This new TSO required the following improvements (a partial listing here): more reliable G switches, remote switches with a system of allowing the pilot to monitor ELT operations, more stringent environmental testing to include salt water spray and water immersion, crash resistance, vibration tolerance, and tighter frequency requirements for transmitters.
This new TSO has gone a long way to improving the reliability of ELTs. In accordance with FAR 9 1-207, after June 21, 1995 all newly installed or replacement ELTs must meet this new TSO standard. Older TSO C-9 1 units may still be repaired subject to parts availability but may not be installed as a new installation.
Without repeating FAR 91-207, I will attempt to highlight the main points: ELTs must be attached to the airplane in such a manner that the probability of damage to the transmitter in the event of crash impact is minimized. ELTs must be attached to the airplane as far aft as practicable.
Most General Aviation aircraft must now have an operating ELT. A few exceptions (not a complete listing) are made for aircraft equipped to carry not more than one person, and “Aircraft while engaged in training operations conducted entirely within a 50 nautical mile radius of the airport from which such local flight operations began.”
In addition to several other exceptions there is also a provision for aircraft operation (up to 90 days) with an ELT removed for maintenance. A logbook entry stating the removal date, make model, serial number, reason for removal and a placard on the instrument panel stating, “ELT not installed” is required.
Requirements for battery replacement are as follows: replace when the transmitter has been in use for more than 1 cumulative hour, or when 50 percent of the useful life has expired. When a battery is replaced the new expiration date must be marked on the transmitter itself, and be entered in the aircraft maintenance records (logbook).
In addition to these general requirements of FAR 91-207 is the specific requirement for an annual inspection of the ELT in addition to any other inspection requirement for the aircraft as a whole. This annual inspection requires checking for: proper installation, battery corrosion, operation of the controls and sensor, and presence of a sufficient signal radiated from its antenna.
Preventive maintenance is an important function in dealing with ELTs and can not only save your life, it can save you money by correcting small problems before they require replacement of the ELT.
Corrosion is the biggest problem with ELTs. Keep all water out of the area where the ELT is mounted as well as antennas, antenna wiring (coax) connections and mounting points. Do not spray or allow aircraft cleaners, solvents, and harsh soaps into or on ELTs, antennas, or connections. Never use chemicals to clean ELTs unless it is known without a doubt no damage will be done to plastic materials, circuit boards, etc.
Check the batteries (including D Cell installations) for leaks, corrosion, and expiration.
Check that the antenna is in fact installed and connected to the ELT. Check that the ELT is mounted properly—installations on hat racks, upholstery material and plastic interior panels are definitely improper, and in the event of a crash could cause injury by flying around the cabin. ELTs held on by zip ties, safety wire or hose clamps are also improperly installed.
In all cases a certified mechanic must install the ELT properly by using approved parts, attaching it to a metal airframe structure and making the proper record entry.
Pilots may preflight check ELT operation occasionally within the first five minutes of any hour by using the test switch, and tuning your Com radio to 121.5 with the speaker volume up. Keep tests brief (10 sec max) and be sure to reset the switch to arm when done. As a pre-shutdown check, tune 121.5 on your aircraft com radio and listen to see if your ELT is transmitting (malfunctioning); shut if off if it is on, and have the unit repaired promptly.
Keep in mind that the batteries must be replaced when used for one cumulative hour. Battery replacements are fairly simple but be certain that the battery you are installing is in fact approved for the ELT you are installing it into. Use care in connecting the battery to the ELT; reverse polarity can destroy an ELT.
Those with the new style ELTs that use D Cells must use batteries that all have the same manufacture date. In addition the actual expiration date of the battery is governed by the 50 percent useful life rule as specified in the FAR (91.207).
In communicating with Duracell, I was informed that the manufacture month/year can be identified on back of the battery package with a six-digit alpha numeric code. The first number is the year of manufacture and the first letter corresponds to the month – “A” being January, “B” being February, etc.
In years past there was some confusion as to the specific brand of replacement ELT battery; with only one exception (Narco 910 units require factory service) all batteries that are FAA/PMA approved batteries for the intended unit are approved.
Repairs, installations and required inspections to ELTs must be done by FAA/ FCC “authorized persons” and may not be done by an aircraft owner as preventive maintenance.
Repairs to many units can be made by the manufacturer and other approved facilities, if the parts are available, however many parts are no longer made and spare parts supplies have been exhausted. Some manufacturers may accept their older C-9 1 units in trade for their newest models.
In addition to spare parts availability, the older C-91 units require part number specific antennas, as the antennas were a part of the original design, installation and certification of the unit. If you have a broken or missing antenna, or damaged coax cable for the C-9 1 unit, be sure that you replace these with the EXACT part as other brand antennas and coax cables render the ELT use less or unreliable. The newer C-9 1A units are not so specific but check your parts/owner’s manual for the details concerning replacement parts.
As with all electronic systems, change is always in the “air” and ELTs are no exception in that the newest type of ELT incorporates the 406 MHZ frequency. While this may seem unimportant, the current satellite system capable of receiving the 121.5 and 243.0 ELT signals (usually 50 milliwatt of power) is scheduled to be decommissioned in 2009.
The newest 406 MHz ELT units transmit a five-watt burst signal along with a digital identification code unique to each unit.
In the case of aircraft, (marine and personnel units are also available) the code includes the identification of the plane by specific license number and if interfaced to the GPS can also include the exact coordinates of the position of the aircraft.
Each unit must be registered and with this registration is included specific information regarding the aircraft, including a telephone contact number and home base information. This information can cut down on false alarms, and assist rescuers with important information. With this new system a search can be initiated within minutes instead of hours.
As an interesting note several manufacturers now offer personal locater beacons that operate on 406 MHz frequency and are advertised and displayed to the aviation public. While these may save your life and are cheaper to purchase, the aviation units are much better and you stand a better chance of rescue especially if one or more people are injured or the personal unit is not able to be located to be activated or is damaged in a crash.
With the older satellite system that uses the 121.5 and 243.0 signals a minimum of two passes of the satellite is required to get a “fix” on the position of the ELT, (which may take six hours or more). A study done by a state aviation department determined that the average time required for locating an aircraft with a properly operating TSO C-91 or 91a beacon was 22 hours.
If the beacon was not working or none was installed, average time was 131 hours. In addition to this long wait time it also was determined by spot inspections of supposedly properly operating and installed ELT’s only 50 percent were actually found to be fully functional—some with batteries expired, broken antennas etc. Some aircraft were found after days of searching that had an ELT installed, but the switch was in the OFF position!
As with all aircraft components, ELT systems require proper installation, regular inspections and maintenance. Make sure your ELT is in good operating condition and insist on more than the minimum maintenance.
In recent years many pilots and passengers have survived aircraft accidents only to perish when rescue operations were hampered by an inoperative ELT. When replacing your ELT, consider the benefits of the newest style 3 frequency ELT including 406 Mhz. Also consider a survival/first aid kit as with the present system it may be many hours before you are rescued. A properly installed and fully functional ELT may save your life!
