CAA Legislates to Make ELTs Mandatory

At risk too are the SAR crews and their aircraft, who are required to fly at low level and low speed, usually over hostile terrain and quite often in poor weather conditions. SAR aircraft have crashed in the past, often killing crew members. Not only is the human cost of prolonged searches great though, it is very easy for an extended search to cost hun- dreds of thousands or even millions of dollars, particularly when types such as expensive to operate and maintain twin engined rescue helos answer the request for help.

While the CAA stresses that ELTs are not the miracle cure, when activated correctly they do dramatically reduce search times from days to hours, search costs from millions to thousands, and most importantly can save lives.

In basic terms ELTs are small emergency beacons that activate on impact of a crash to send a distress signal which is relayed by satellites. The satellite receives the signal and retransmits it to a ground station where the distress signal can then be acted upon. The advantage of ELTs though is not only do they alert that an accident has occurred almost immediately, they can tell exactly where the aircraft is, down to an accuracy of 1km for ELT’s broadcasting on 406mHz, and 10km for 121. 5mHz ELTs – saving valuable time and effort in locating the crash site. This is the major benefit of ELTs. In an ideal world, the ELT would, having survived the force of impact, begin transmitting to the nearest SARSAT or COSPAS satellite immediately while various airborne and ground based receivers capable of homing on the signal help to pinpoint the location of the source of the ELT transmissions. The satellite, having received the transmission from the ELT then relays it to a ground station if one is in view. In the case of 406mHz ELTs the satellites will store transmissions until a ground station comes into view, and then download it. An ELT activated by a crash near Cooktown, for example, may not be received by the Australian ground station because the antenna is aimed at a satellite over Port Hedland. In this case the data could be downloaded to a ground station at Hong Kong for relay back to Australia. In almost all cases in Australia, this information is passed through the ground station in Alice Springs (another station is in Wellington, New Zealand) and relayed to the Australian Maritime Safety Authority centre in Canberra for processing within half an hour. For more remote locations the alert is received within 1. 5 hours. In ideal conditions the beacon need only transmit for 90 seconds to be effective, but in most cases a transmission time of a few minutes will give an accurate location reading.

In the real world though there have been problems with ELTS. Most problems stem from the fact that many early generation ELTs simply do not survive the impact and fail to begin transmitting once an accident has occurred. The failures are usually associated with ELTs compliant with the US Federal Aviation Administration’s Technical Standard Order (TSO) C91. ELTs compliant with this TSO are only designed to withstand crash loads of 50G, while if they do survive they often fail to function and also have a high false alarm rate. While the CAA will regulate to ensure ELTs fitted are of the more capable TSO C9la standard, many aircraft flying in Australia at the moment are fitted with ELTs compliant with the old standard. Of even more concern are aircraft carrying maritime ELTs. As they are designed to operate in a maritime environment they have poor chances of surviving an aircraft crash and are not impact activated. (Aircraft fitted with marine ELTs or those which only comply to TSO C91 will need to be retrofitted to the new standard. ) Poor maintenance is also a major factor in many ELTs’ failure to operate, the batteries in particular need to be checked at regular intervals to ensure they are able to provide the necessary power. While it goes without saying that an ELT without an operational battery is useless, it appears that few pilots and operators regularly check to make sure they are in a working condition.

Another problem is the ELT’s positioning in the aircraft. The ELT unit needs to be positioned as far away from the nose, in almost all accidents the major point of impact, as possible. In some light aircraft though this can present prob- lems associated with the centre of gravity given that an ELT unit weighs about three kilogrammes.

In regulating to make ELT’s mandatory, the CAA has taken account of these factors. With the exceptions mentioned, all Australian registered aircraft will have to be fitted with an ELT authorised by the FAA to be compliant with its TSO C91a or higher. These ELTs broadcast on 121. 5 and 243mHz (as do C91 ELTs) but are designed to withstand impacts of up to 500G. These ELTs also have a degree of fire resistance.

The most capable current standard of ELT is the TSO C126. ELTs to this standard operate on 406mHz in addition to 121. 5 and 243mHz. These have been designed to give greater signal margin, better position accuracy, global coverage and are less susceptible to interference. The major benefit of 406mHz ELTS though is that the satellites will store the transmission if they cannot download to the Australian ground station, which could be monitoring another satellite, or be down for maintenance. Another benefit is that the transmission signal is encoded with specific aircraft data including the owner’s name, address and telephone number, aircraft type and registration. In the future 406mHz ELTs will be able to transmit to geostationary satellites, with the benefit of immediate data relay. One geostationary satellite capable of processing 406mHz ELTs is already in place over the Atlantic. Fitment of C126 standard ELTs will probably become compulsory from 2000.

Not only will the CAA regulate to make the C91a standard of ELT mandatory, a number of other regulations will be in place to ensure their proper installation and upkeep. All will have to be fitted by a Licenced Aircraft Maintenance Engineer, under the supervision of a qualified instrument approval holder. In addition it must be strictly maintained to the manufacturer’s instructions and undergo regular checking.

While the mandatory fitment of ELTs is bound to come under criticism because of its representing yet another cost on an already overburdened GA industry, a basic TSO C91a ELT unit retails at around $300, with installation estimated to be about the same amount again. A small price to pay if it saves your life or those of your passengers.