SHOP TALK

DECEMBER 2016

“Here I am!” - ELT Testing

by Kerry McIntyre

This month’s ShopTalk will update the reader on ELT testing that is required under FAR 91.207(d) every twelve calendar months and/or during an annual or 100-hour inspection (they may coincide). Over the years, ShopTalk has harped on the fact that you, the airplane owner, are responsible for the airworthiness of your aircraft, so compliance with the FARs is pretty important. Also see FAA Advisory Circulars, AC43.13-1B Pages 12-606 & 607 and AC 91-44A. We last wrote about ELTs in the January 2009 MAPA Log (Help, I’ve crashed and I have no TV reception!).

Back then, 406 MHz ELTs were just becoming available; only three were approved and the purchase prices exceeded $850. Today there are ten U.S. manufacturers providing multiple models with prices starting around $500 and General Aviation maintenance shops are seeing more and more 406 MHz installations.

406 MHz ELTs communicate with the COSPAS-SARSAT Internation Satellite System for search and rescue (SAR). Twelve satellites are operational with more being added. There are more than 1.6 million 406 MHz beacon sets worldwide. As of the end of 2014, this system has responded to over 11,000 incidents and assisted in rescuing over 39,000 persons worldwide. Aviation accounts for about 16% of SAR events.

FAR 91.207 doesn’t get into specific detail about maintaining ELTs; the detail comes from the manufacturer’s manual(s). Once testing and any maintenance are complete, the aircraft must be returned to service by a certified A&P or FAA Approved Repair Station. Here is what is pertinent:

Read the manual! Each ELT model has specific operations, procedures and controls. Before doing any disassembly, run a test of the ELT system. This will confirm that components are operable. If the test fails, then troubleshooting is in order.

Battery life: FAR 91.207(c)(1 & 2) Replace (or recharge) when the transmitter has been used for more than one cumulative hour; or when 50 percent of the battery’s useful life has expired. ELT tests add to the cumulative time. Most newer ELTs keep track of this.

FAR 91.207(d) states that each 12 months the ELT must be inspected for:

    (1) Proper installation- see FAR 91.207(b) and manufacturer’s manual.

    (2) Battery corrosion.

    (3) Proper operation of controls and crash sensor – see the manufacturer’s manual.

   (4) The presence of a sufficient signal radiated from its antenna – again see the manufacturer’s manual.

Next remove the ELT and disassemble it to check for corrosion. Note the expiration date on the battery and replace it as necessary. Make a record of the expiration date.

Reassembled the ELT and verify (on the bench) that the controls and crash sensor are working per 91.207(d)(3). For the 121.5 MHz transmitter, this is a simple test. Remember, perform this test within the first five minutes after any hour (FCC requirement). Use an AM radio tuned to between stations (static) placed within 6 inches of the ELT antenna. With the ELT in the ARM position with a remote antenna connected, apply a quick fwd and aft jerking motion to the ELT along the longitudinal mounting axis. This should set off the crash sensor and you should clearly hear the alarm sweep over the AM radio. Limit this test duration to a second or two, just enough to hear three sweeps of the signal. This test is one the FAA came up with and is acceptable for 121.5 MHz ELTs.

If you have a 406 MHz ELT this test is similar but a 406 MHz ELT tester is utilized. Only do this test inside a closed metal building as to not send a distress signal to the satellite. The metal building must act as a Faraday shield to block the transmitted signal. Windows, skylights and non-metal doors are areas that could allow a signal to leak to a satelite. Remember we are setting off the ELT and the satellite can’t tell a functional test from a crash. Keep these tests to a minimum of time. Deactivate or reset the ELT when the tests are complete. No one wants search and rescue showing up unannounced.

There is another way to test the signal sufficiency for a 406 MHz ELT without having to purchase a $2800 ELT tester and that is to register with www.406test.com and pay a one-time registration fee and a per-event testing fee. Follow the instructions and you will get a report e-mailed back on the results. Unfortunately this test will not comply with the test of the crash sensor. FAR 43.13(a) requires one to have the proper equipment as per the manual: a 406 MHz tester.

At this point we have checked the battery and the controls and crash sensor for proper operation. Reinstall the ELT in the plane and test the rest of the system.

With the ELT reinstalled and all the wiring/antenna connections complete, let’s look at the cockpit switch. Not all 121.5 ELTs have a cockpit switch but all 406 MHz ELTs do. Some switches have a battery in them with an expiration date. Replace this battery if it is expired or its date is unknown. Record the switch battery expiration date just as you have for the ELT battery.

Now set the ELT to ARM and place your AM radio set to any AM station next to the ELT antenna on the plane. Activate the ELT using the remote switch and verify that the alert signal sweep can be heard over the AM radio. Again, if you are testing a 406 MHz ELT then this test must be done in a closed metal building. During the 406 MHz test, listen for the Sonalert buzzer (121.5 MHz only ELTs do not have a buzzer). Once the tester has captured the data, reset the ELT to stop the test. Verify the ELT is no longer transmitting.

This will complete FAR 91.207(d)(4) - sufficient signal strength. One nice feature on the 406 MHz tester is the data it gets from the ELT shows its ID and serial number. This data allows the mechanic to verify that this 406 MHz ELT is registered to this airplane and owner. Remember that 406 MHz ELTs are registered through NOAA and that registration data helps search and rescue do their job. If 406 MHz ELTs are swapped out you must re-register the new one and deactivate the old one as not to confuse search and rescue.

Last, but not least, record in the airframe log book that FAR 91.207(d) has been complied with and the expiration dates of all the batteries in the system.

As always