wireweinie
FOUNDER
Palmer, AK
We are all familiar (or should be) with FAR 91.207 (d) (1) through (4)
(d) Each emergency locator transmitter required by paragraph (a) of this section must be inspected within 12 calendar months after the last inspection for--
(1) Proper installation;
(2) Battery corrosion;
(3) Operation of the controls and crash sensor; and
(4) The presence of a sufficient signal radiated from its antenna.
(1) Proper installation is pretty straight forward. Is the unit installed as per the manufacturer's instructions. If you need the manual, most are available on line for free. The only thing I would caution is that the 'stiffness' requirements for the tray mount is more than what has been previously acceptable.
(2) Battery corrosion. Again, very straight forward. Evidence of water intrusion? Green or white crusty stuff growing? Especially from the units battery compartment.
Before we get to lines (3) and (4) look back at how we tested the 121.5 mhz ELT's. We took them out of the tray. smacked them and checked to see if the signal bled over onto an am radio next to the antenna. Reset, re install, and done. And it actually worked well! These older units used g-switches for activation. They tripped when an impact of a high enough amplitude was sensed from the front of the unit. As for the signal strength, if a 121.5 mhz signal can be heard on an am radio, when it its tuned off station, that signal will measure strong enough to pass a measured test.
Now for testing these parameters in a 406 mhz ELT.
(3) Operation of controls and crash sensors. The new ELT's use accelerometers, not g-switches as crash sensors. These are designed circuits, not a one off item. And they are designed to trip when they sense a rapid deceleration instead of a high amplitude impact. It means that you can hit it with your hand, a rubber hammer, or bang it on the bench and it won't set the unit off. To set it off, you need to hold the unit in both hands, the forward portion (the arrow) facing away. Without letting go, 'throw' the unit away from you and jerk it back quickly. That motion will trip the accelerometer(s). then reset the unit as per the manuals instructions. This will test the sensors and controls on the unit. The cockpit switch can be tested after the unit is re installed.
(4) The presence of a sufficient signal radiated from it's antenna. Power out. Remember checking for 121.5 mhz with the am radio? It doesn't work for 406 mhz. While a 406 ELT does piggyback a 121.5 mhz signal along with a 406 mhz signal, 406 will not bleed over onto an am radio. To high a freq and most 406 signals are a 'blip' about a second in duration, every 40 to 60 seconds.
This will make some customers howl. The only way to comply with line (4) is with a dedicated test set. This is the rundown on how it's done.
The unit can be tested in the aircraft or on the bench (preferred). On the aircraft, the test set is set up with it's own antenna. The ELT is removed from the tray and power is measured on 121.5 and 406 mhz while the sensors and controls are tested. Read the manual for your exact model. On the bench, the ELT is connected directly to the test set, through an attenuator. A big advantage is that the test may be conducted at any time without pinging the SAR guys. Once again the unit is tested as per the manual for that model.
With either method, signal strength (power out) is actually measured and the controls and sensors are tested. Signal strength is usually given in dbm. For example Artex requires 37 dbm, +/-2 for 406 mhz and 20 dbm minimum for 121.5 mhz. Also all country, hex I.D. and aircraft codes are verified. Without a test set none of these things are possible. Just bought an aircraft? What codes are programmed into the ELT? I've come across wrong country codes and wrong aircraft codes (wrong N numbers) for example. I've also come across units that tested for good power on 121.5 and low power on 406 mhz. And I have not found a manual yet that did not call out a test set/service for the annual inspections.
If the unit was tested on the bench, the antenna (and only the antenna) can be tested by the old am radio test. If you have already bench tested for good signal strength, then if 121.5 mhz goes out over the antenna, 406 mhz will also be good. The antenna is just a piece of wire, after all.
Self test functions tell such info as correct wiring and connections and if the battery has low voltage. But it will not tell you of correct signal strength or codes. If someone relies on the am radio test and self test functions they are not in compliance with 91.207 (d).
You may fire when ready, Gridley
Web
(d) Each emergency locator transmitter required by paragraph (a) of this section must be inspected within 12 calendar months after the last inspection for--
(1) Proper installation;
(2) Battery corrosion;
(3) Operation of the controls and crash sensor; and
(4) The presence of a sufficient signal radiated from its antenna.
(1) Proper installation is pretty straight forward. Is the unit installed as per the manufacturer's instructions. If you need the manual, most are available on line for free. The only thing I would caution is that the 'stiffness' requirements for the tray mount is more than what has been previously acceptable.
(2) Battery corrosion. Again, very straight forward. Evidence of water intrusion? Green or white crusty stuff growing? Especially from the units battery compartment.
Before we get to lines (3) and (4) look back at how we tested the 121.5 mhz ELT's. We took them out of the tray. smacked them and checked to see if the signal bled over onto an am radio next to the antenna. Reset, re install, and done. And it actually worked well! These older units used g-switches for activation. They tripped when an impact of a high enough amplitude was sensed from the front of the unit. As for the signal strength, if a 121.5 mhz signal can be heard on an am radio, when it its tuned off station, that signal will measure strong enough to pass a measured test.
Now for testing these parameters in a 406 mhz ELT.
(3) Operation of controls and crash sensors. The new ELT's use accelerometers, not g-switches as crash sensors. These are designed circuits, not a one off item. And they are designed to trip when they sense a rapid deceleration instead of a high amplitude impact. It means that you can hit it with your hand, a rubber hammer, or bang it on the bench and it won't set the unit off. To set it off, you need to hold the unit in both hands, the forward portion (the arrow) facing away. Without letting go, 'throw' the unit away from you and jerk it back quickly. That motion will trip the accelerometer(s). then reset the unit as per the manuals instructions. This will test the sensors and controls on the unit. The cockpit switch can be tested after the unit is re installed.
(4) The presence of a sufficient signal radiated from it's antenna. Power out. Remember checking for 121.5 mhz with the am radio? It doesn't work for 406 mhz. While a 406 ELT does piggyback a 121.5 mhz signal along with a 406 mhz signal, 406 will not bleed over onto an am radio. To high a freq and most 406 signals are a 'blip' about a second in duration, every 40 to 60 seconds.
This will make some customers howl. The only way to comply with line (4) is with a dedicated test set. This is the rundown on how it's done.
The unit can be tested in the aircraft or on the bench (preferred). On the aircraft, the test set is set up with it's own antenna. The ELT is removed from the tray and power is measured on 121.5 and 406 mhz while the sensors and controls are tested. Read the manual for your exact model. On the bench, the ELT is connected directly to the test set, through an attenuator. A big advantage is that the test may be conducted at any time without pinging the SAR guys. Once again the unit is tested as per the manual for that model.
With either method, signal strength (power out) is actually measured and the controls and sensors are tested. Signal strength is usually given in dbm. For example Artex requires 37 dbm, +/-2 for 406 mhz and 20 dbm minimum for 121.5 mhz. Also all country, hex I.D. and aircraft codes are verified. Without a test set none of these things are possible. Just bought an aircraft? What codes are programmed into the ELT? I've come across wrong country codes and wrong aircraft codes (wrong N numbers) for example. I've also come across units that tested for good power on 121.5 and low power on 406 mhz. And I have not found a manual yet that did not call out a test set/service for the annual inspections.
If the unit was tested on the bench, the antenna (and only the antenna) can be tested by the old am radio test. If you have already bench tested for good signal strength, then if 121.5 mhz goes out over the antenna, 406 mhz will also be good. The antenna is just a piece of wire, after all.
Self test functions tell such info as correct wiring and connections and if the battery has low voltage. But it will not tell you of correct signal strength or codes. If someone relies on the am radio test and self test functions they are not in compliance with 91.207 (d).
You may fire when ready, Gridley
Web