AIR CRASH: DO EMERGENCY LOCATOR TRANSMITTER (ELT) STILL TRANSMIT?

(article was written June 2007)

Emergency Locator Transmitters are emergency devices carried aboard most general aviation aircraft. They are designed to transmit a distress signal on 121.5MHz, 243.0MHz and for newer ELTs, 406MHz frequencies in the event of an aircraft accident. Currently, ELTs are required to be installed in almost all registered civil aircraft, including general aviation aircraft. There are three groups of transmitters, Emergency Position-Indicating Radio Beacons (EPIRBs), Emergency Locator Transmitters (ELTs) and Personal Locator Beacons (PLBs). These are tracking transmitters that operate as part of the Cospas-Sarsat satellite system. When activated, the beacons send out distress signals that allow them to be located by the satellite system and search and rescue aircraft to locate the people, boats and aircraft needing rescue. EPIRBs are used for maritime emergency, ELTs for aircraft and PLBs for personal use.

History & Evolution

ELTs were introduced to general aviation as a result of a US Congressional Mandate. The mandate was a result of the 1972 loss of U.S. Representatives Hale Boggs and Nick Begich in Alaska after their aircraft crashed and was never found.

Most beacons are brightly colored, waterproof, fit in a cube about 30 cm on a side, and weigh 2-5 kg. The units have a useful life of 10 years, operate across a range of conditions (-40°C to 40°C), and transmit for 24 to 48 hours. The cost varies from US$139 to US$3000 with varying performance. The older ELTs are manually activated when inserted in water, which dissolves a vecro band attached to the antenna. This action releases the spring-loaded antenna for transmition to begin. The batteries are also water activated. Although modern systems are significantly superior to older ones, the older systems still provide an immense improvement in safety, compared to not having a beacon.

The older, cheaper beacons send an anonymous warble at 121.5MHz. They can be detected by satellite over only 60% of the earth, require up to 6 hours for notification, locate within 20 km (search area of 1214 km²) and are anonymous. Coverage is partial because the satellite has to be in view of both the beacon and a ground station at the same time - the satellites do not store and forward the beacon's position. Coverage in polar and south-hemisphere areas is poor. The frequency is the standard aviation emergency frequency and there is interference from other electronic and electrical systems, so false alarms are common.

By international agreement, these original 121.5MHz (civil) and 243MHz (military) beacons will no longer be sensed by satellites starting in 2009. They will be replaced by automatic ELTs operating simultaneously on 406MHz and on 121.5MHz. However, pilots and ground stations are encouraged to continue to monitor for transmissions on the emergency frequencies. ELTs were originally intended for use on the 121.5MHz frequency to alert air traffic control and aircraft monitoring the frequency.
In 1982, a satellite-based monitoring system, COSPAS-SARSAT was implemented to provide a better receiving source for these signals. As from the 1st of February 2009, the international COSPAS-SARSAT satellite system will discontinue satellite-based monitoring of the 121.5MHz and 243MHz frequencies, in part because of a high number of false signals attributed with these frequencies.

After this date, 121.5/243MHz distress signals transmitted from ELTs operating on the lower frequency will only be detected by ground-based receivers such as local airport facilities and air traffic control facilities or by over flying aircraft. It is important to note that after 2009, existing 121.5MHz ELTs, though still legal from the FAA's perspective, will provide extremely limited assistance if an aircraft crashes, especially in a remote location.

What The Law Says?

International Civil Aviation Organization (ICAO) legislation requires all aircraft flying with more than 19 seats to carry at least two emergency locator transmitters (ELTs), which are either fixed or portable. ICAO Annex 6 goes further to state that these must be automatic, operating simultaneously on 406MHz and 121.5MHz and carried by airplanes operating long-range flights, over-water and over designated land areas. This was adopted by the ICAO Council on 15th March 1999, with an applicability date of 1st January 2002 for all new aircrafts (for which the Certificate of Airworthiness was first issued after that date) and 1st January 2008 for all aircraft. The Federal Aviation Authority (FAA) of America has a similar law with an addition. It stipulates that the “ELT 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. Fixed and deployable automatic type transmitters must be attached to the airplane as far aft as practicable”. It must be inspected within 12 calendar months after the last inspection for proper installation, battery corrosion, operation of the controls, crash sensor and for presence of a sufficient signal radiating from its antenna.

ELTs and Recent Crashes

On the 5th of May 2007, Kenya Airways Flight KQ507 operated by a six-month old Boeing 737-800 carrying 114 passengers crashed into a marshy jungle with less than a minute after take-off and was not found till after 36 hours. Adam Air Flight 574 operated by a fourteen-year old Boeing 737-400 disappeared into the sea off the South-West Coast of Sulawesi Island in Indonesia on the 1st of January 2007 with 102 passengers. Despite all the flurry, experts, gadgets and support from different organizations and countries, only a tiny fragment of the aircraft, found by a local fisherman is available for us to see today after combing the area for over six weeks. Gol Airlines Flight 1907 operated by a seventeen-day(17days) old Boeing 737-800 aircraft with only 200hrs flying time, on the 29th of September 2006 and carrying 154 passengers tipped the wing of a Legacy business jet mid-air and headed for the Amazon jungle. It took precisely six days for the aircraft to be located and rescue started two days after.

Coming closer home, in November 2006, Bellview Airlines Boeing 737-200, Flight B3201, carrying 117 passengers took off from Lagos, crashed and was entombed somewhere in Ifo, Ogun State. The aircraft was discovered by a young farmer who called his father and they went to AIT Office in Alagbado about 24hours after the crash.

The basic purpose of the ELT is to get people rescued by facilitating location of crash site within the "golden day" when the majority of survivors can still be saved.

ELTs and Recent Crashes

Two ELTs were placed on board each of the aircraft referred to above, but were unable able to facilitate location of the aircraft, even though they are meant to start transmitting automatically in an emergency. For Kenya Airways and Gol Airline crashes, the aircrafts are brand new and complimented with fixed & deployable automatic type transmitters. The hulls (aircraft) and bodies (passengers) were recovered from the crash sites. There is a probability that some survivors died due to late recovery. Now if the ELTs were destroyed or damaged in these crashes, isn’t it imperative for manufacturers of this important safety device to start a process of redesigning it so it can activate and transmit to the required frequencies and expedite rescue in an emergency.

Recently, a call for 406MHz emergency locator transmitters (ELTs) to be carried on all aircraft that fly internationally is being challenged by the International Council of Aircraft Owner and Pilot Associations (IAOPA). The Council says it “has concerns about the reliability of 406MHz ELTs”, and suggests an alternative, such as a personal locator beacon (PLB), should be permitted in light general aviation aircraft.

IAOPA wants the proposal shelved until the reliability of 406MHz ELTs is better researched using search-and-rescue satellite statistics not only for the incidence of successful locations, but the numbers of events “in which either equipment or systems did not perform satisfactorily”. I totally agree with IAOPA, in addition, ELTs should be redesigned and strengthen to survive crashes

Also quoting an official of Kenya Civil Aviation Authority (KCAA) on the recent Kenya Airways crash, "inbuilt devices sent out distress signal which was picked up along the West African Coast around the time it went missing but emergency and automatic locational devices did not perform as expected", collaborating this view, the Head of Cameroun Civil Aviation Authority Sam Juma, told Radio France International that “the automatic distress beacon (ELT) stopped transmitting after take off and I think it was immediately destroyed, because it made precise location difficult.

Do I need to say I am not alone in my doubts? ICAO in my opinion should suspend the 1st July 2008 deadline for the implementation of the 406MHz ELTs for airlines and rather set up a team to look into the inadequacies of ELTs.