ELT alarm - Clarification?

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skipone

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skipone
I wondered if someone might clarify this.

I was watching a video of a guy testing a 121.5 ELT device which is activated either by impact or by manually activating it remotely on a panel ( on the way down or upon landing ).

In the video, it let off this audible alarm that could be heard coming out this remote radio tuned into the frequency.

My question is this: If the audible signal is ONLY heard over the frequency by those monitoring ( people who can help ) how does the pilot who has activated manually or hoped it activated upon crash know that it's working? I mean there is no speaker on the ELT so its not like the one who has crashed can hear the audible alert unless their radio is working and they are also tuned in.

Am I understanding this correctly that only those tuned in hear the audible alert, and those in the crashed plane can't hear it but have to assume it's working?
 
tune your com to 121.5 and listen to the signal

edit the 406 ELT is the way to go. 121.5 ELTs are not normally monitored anymore
 
Only the very old installations do not have an remote indicator on the instrument panel that indicates it is going off. Usually an LED, I believe it usually flashes, but not sure.
All installations after a certain date are required to have the remote indicator, which also allow the ELT to be remotely activated and deactivated from the cockpit. Maybe somebody here know about what date that became a requirement.

Brian
 
AKBill said:
tune your com to 121.5 and listen to the signal

edit the 406 ELT is the way to go. 121.5 ELTs are not normally monitored anymore
Click to expand...
Okay, so that does confirm it.

The audible alert is ONLY heard by those tuned into the frequency and not by the pilot or passengers in the crash, so there would be no real way for them to know if it worked or not unless help showed up. ( and as you said, 121.5 isn't monitored as much or not at all anymore). Or an LED was flashing.

So is 406Mhz the new emergency broadcast frequency? and what happens to PLBS which use 121.5?
 
i've been monitoring 121.5 in a scanner at home since, well, forever. i've heard the occasional voice traffic and once two pilots yakking back and forth but never an actual alarm...until last week. it sounded like a high pitched foghorn or the alarm in the 007 movies that sounds when Blofeld's secret bunker was about to blow up. it started strong but slowly faded out. the closest field to me is KDPA but it's too far to hear ground comms. either the pilot tripped it by accident or there was a hard touch n go.
 
rk911 said:
i've been monitoring 121.5 in a scanner at home since, well, forever. i've heard the occasional voice traffic and once two pilots yakking back and forth but never an actual alarm...until last week. it sounded like a high pitched foghorn or the alarm in the 007 movies that sounds when Blofeld's secret bunker was about to blow up. it started strong but slowly faded out. the closest field to me is KDPA but it's too far to hear ground comms. either the pilot tripped it by accident or there was a hard touch n go.
Click to expand...
I wonder how they will deal with pilots who still have 121.5 ELTs in their bush planes? And how does this effect PLBs which run on that frequency?
 
skipone said:
So is 406Mhz the new emergency broadcast frequency? and what happens to PLBS which use 121.5?
Click to expand...
The 406 is a GPS/satellite based system. Most 406 ELTs will broadcast on 121.5 for a period of time but the 406 reduces the search radius from miles to feet. I thought PLB's were a satellite based system also
 
skipone said:
I wonder how they will deal with pilots who still have 121.5 ELTs in their bush planes? And how does this effect PLBs which run on that frequency?
Click to expand...
121.5 ELT is 1950’s tech. The FAA stopped allowing the manufacturer of them a few years back. No requirement to remove them by a certain date. Mine works fine but in the interest of safety/modernization, I have a 406 on the shelf in the hangar for the annual.

ATC and airliners (Others SHOULD as well) still monitor guard. We catch them, report them, triangulate via solicited reports and eventually they find them. Much prefer my exact coordinates being beamed up.
 
Radar Contact said:
121.5 ELT is 1950’s tech. The FAA stopped allowing the manufacturer of them a few years back. No requirement to remove them by a certain date. Mine works fine but in the interest of safety/modernization, I have a 406 on the shelf in the hangar for the annual.

ATC and airliners (Others SHOULD as well) still monitor guard. We catch them, report them, triangulate via solicited reports and eventually they find them. Much prefer my exact coordinates being beamed up.
Click to expand...

Does the 406 broadcast on BOTH frequencies ( i.e it will try 121.5 then go to 406 or only on 406)?

And if the antenna was not attached when you activated it would the LED light up but there would be no audible alert sent out?
 
AKBill said:
The 406 is a GPS/satellite based system. Most 406 ELTs will broadcast on 121.5 for a period of time but the 406 reduces the search radius from miles to feet. I thought PLB's were a satellite based system also
Click to expand...

Just to make sure I understand you.

So 406 is GPS satellite that is monitored by military and SAR aircraft (Search-and-Rescue Satellite-Aided Tracking System)

And 121.5 is not GPS satellite and is radio-tower-based ( yes?) and that is still monitored by pilots ( airliners) and by pretty much every ATC facility, military and civilian.

Correct?
 
406 talks to satellites. The satellite system tells the searchers where you are.
121.5 may or may not be heard by anyone. ATC won't hear it, they are typically not line of site. Someone flying over will if they are monitoring that frequency.
 
Capt. Geoffrey Thorpe said:
406 talks to satellites. The satellite system tells the searchers where you are.
121.5 may or may not be heard by anyone. ATC won't hear it, they are typically not line of site. Someone flying over will if they are monitoring that frequency.
Click to expand...
Ah, understood. So if the antenna was broken or not attached would I be correct in saying that when you flip that switch on the panel it might light up but no broadcast would be sent out because there is no antenna? ( hence the need to check before each flight)

And interesting video i came across on 406 and 121.5 video was quite an eye opener. So many folks thinking these are bulletproof, think again.

 
Last edited:
skipone said:
Ah, understood. So if the antenna was broken or not attached would I be correct in saying that when you flip that switch on the panel it might light up but no broadcast would be sent out because there is no antenna? ( hence the need to check before each flight)
Click to expand...
No. Don't check it before each flight. That runs the battery down, and most ELTs have a limit on such testing because of that. Moreover, testing an ELT is only legal if the thing is connected to a ballast instead of an antenna and is inside an RF box so ATC doesn't hear anything. Mechanics often test an ELT but only between the hour and five after the hour, such as 11:00 and 11:05, and the transmission has to be limited to just a few seconds. There are fines for operating one illegally. It's not ok to be testing it in flight, either. And running a transmitter without an antenna load can damage it.

From https://www.cfinotebook.net/notebook/avionics-and-instruments/emergency-locator-transmitter We read:

Testing Emergency Locator Transmitters:

  • ELTs should be tested in accordance with the manufacturer's instructions, preferably in a shielded or screened room or specially designed test container to prevent the broadcast of signals which could trigger a false alert
  • When this cannot be done, aircraft operational testing is authorized as follows:
    • Analog 121.5/243 MHz ELTs should only be tested during the first 5 minutes after any hour. If operational tests must be made outside of this period, they should be coordinated with the nearest FAA Control Tower. Tests should be no longer than three audible sweeps. If the antenna is removable, a dummy load should be substituted during test procedures
    • Digital 406 MHz ELTs should only be tested in accordance with the unit's manufacturer's instructions
    • Airborne tests are not authorized
False Signals:

  • Caution should be exercised to prevent the inadvertent activation of ELTs in the air or while they are being handled on the ground. Accidental or unauthorized activation will generate an emergency signal that cannot be distinguished from the real thing, leading to expensive and frustrating searches. A false ELT signal could also interfere with genuine emergency transmissions and hinder or prevent the timely location of crash sites. Frequent false alarms could also result in complacency and decrease the vigorous reaction that must be attached to all ELT signals
  • Numerous cases of inadvertent activation have occurred as a result of aerobatics, hard landings, movement by ground crews and aircraft maintenance
  • These false alarms can be minimized by monitoring 121.5 MHz and/or 243.0 MHz as follows:
    • In flight when a receiver is available
    • Before engine shut down at the end of each flight
    • When the ELT is handled during installation or maintenance
    • When maintenance is being performed near the ELT
    • When a ground crew moves the aircraft
    • If an ELT signal is heard, turn off the aircraft's ELT to determine if it is transmitting. If it has been activated, maintenance might be required before the unit is returned to the "ARMED" position. You should contact the nearest Air Traffic facility and notify it of the inadvertent activation

Inspections & Tests:

  • An emergency locator transmitter (ELT) is required by 14 CFR, part 91, section 91.207, and must be inspected within 12 calendar months after the last inspection for the following:
    • Proper installation
    • Battery corrosion
    • Operation of the controls and crash sensor
    • The presence of a sufficient signal radiated from its antenna
  • 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. Batteries used in the ELTs must be replaced (or recharged, if the batteries are rechargeable):
    • When the transmitter has been in use for more than 1 cumulative hour
    • When 50 percent of the battery useful life or, for rechargeable batteries, 50 percent of useful life of the charge has expired
  • An expiration date for replacing (or recharging) the battery must be legibly marked on the outside of the transmitter and entered in the aircraft maintenance record
  • This does not apply to batteries that are essentially unaffected during storage intervals, such as water-activated batteries
 
The TSO was updated to require a remote indicator to let you know IF it is going off.
As other pointed out, you have to at least once a year, test to see if you can hear it going off.
 
I came across this youtube video on 406 man was it an eye opener. He really talks about how so many bush pilots are still using 121.5 ELts, and that 406 works better but it also has its flaws.
Dan Thomas said:
No. Don't check it before each flight. That runs the battery down, and most ELTs have a limit on such testing because of that. Moreover, testing an ELT is only legal if the thing is connected to a ballast instead of an antenna and is inside an RF box so ATC doesn't hear anything. Mechanics often test an ELT but only between the hour and five after the hour, such as 11:00 and 11:05, and the transmission has to be limited to just a few seconds. There are fines for operating one illegally. It's not ok to be testing it in flight, either. And running a transmitter without an antenna load can damage it.

From https://www.cfinotebook.net/notebook/avionics-and-instruments/emergency-locator-transmitter We read:

Testing Emergency Locator Transmitters:

  • ELTs should be tested in accordance with the manufacturer's instructions, preferably in a shielded or screened room or specially designed test container to prevent the broadcast of signals which could trigger a false alert
  • When this cannot be done, aircraft operational testing is authorized as follows:
    • Analog 121.5/243 MHz ELTs should only be tested during the first 5 minutes after any hour. If operational tests must be made outside of this period, they should be coordinated with the nearest FAA Control Tower. Tests should be no longer than three audible sweeps. If the antenna is removable, a dummy load should be substituted during test procedures
    • Digital 406 MHz ELTs should only be tested in accordance with the unit's manufacturer's instructions
    • Airborne tests are not authorized
False Signals:

  • Caution should be exercised to prevent the inadvertent activation of ELTs in the air or while they are being handled on the ground. Accidental or unauthorized activation will generate an emergency signal that cannot be distinguished from the real thing, leading to expensive and frustrating searches. A false ELT signal could also interfere with genuine emergency transmissions and hinder or prevent the timely location of crash sites. Frequent false alarms could also result in complacency and decrease the vigorous reaction that must be attached to all ELT signals
  • Numerous cases of inadvertent activation have occurred as a result of aerobatics, hard landings, movement by ground crews and aircraft maintenance
  • These false alarms can be minimized by monitoring 121.5 MHz and/or 243.0 MHz as follows:
    • In flight when a receiver is available
    • Before engine shut down at the end of each flight
    • When the ELT is handled during installation or maintenance
    • When maintenance is being performed near the ELT
    • When a ground crew moves the aircraft
    • If an ELT signal is heard, turn off the aircraft's ELT to determine if it is transmitting. If it has been activated, maintenance might be required before the unit is returned to the "ARMED" position. You should contact the nearest Air Traffic facility and notify it of the inadvertent activation
Inspections & Tests:

  • An emergency locator transmitter (ELT) is required by 14 CFR, part 91, section 91.207, and must be inspected within 12 calendar months after the last inspection for the following:
    • Proper installation
    • Battery corrosion
    • Operation of the controls and crash sensor
    • The presence of a sufficient signal radiated from its antenna
  • 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. Batteries used in the ELTs must be replaced (or recharged, if the batteries are rechargeable):
    • When the transmitter has been in use for more than 1 cumulative hour
    • When 50 percent of the battery useful life or, for rechargeable batteries, 50 percent of useful life of the charge has expired
  • An expiration date for replacing (or recharging) the battery must be legibly marked on the outside of the transmitter and entered in the aircraft maintenance record
  • This does not apply to batteries that are essentially unaffected during storage intervals, such as water-activated batteries
Click to expand...

Ah I meant to say, check the antenna in preflight. No antenna or if it suffers from having being severed that device isn't going to be much use. It might light up when you activate it on the way down but no signal would go out right without a working antenna.
 
skipone said:
how does the pilot who has activated manually or hoped it activated upon crash know that it's working?
Click to expand...
FYI: some of the newer 406 ELTs have aux speakers options that will provide audible sound when the ELT transmits either during testing or actual activation. And while I don't quite follow the context of your questions if you have a fear of being left in the boonies there are other products out there that provide real time flight following and can pinpoint your location even without ELT activation.
 
Bell206 said:
there are other products out there that provide real time flight following and can pinpoint your location even without ELT activation.
Click to expand...

Do you mean SPOT tracker, InReach and PLB?
 
flyingron said:
The TSO was updated to require a remote indicator to let you know IF it is going off.
As other pointed out, you have to at least once a year, test to see if you can hear it going off.
Click to expand...
More than that. Annually, and fairly thoroughly too. An inspection for battery corrosion and G-switch operation means the ELT must come out and get opened up. "Sufficient signal" means a strength test. Avionics shops are normally the places that do this stuff.

  • An emergency locator transmitter (ELT) is required by 14 CFR, part 91, section 91.207, and must be inspected within 12 calendar months after the last inspection for the following:
    • Proper installation
    • Battery corrosion
    • Operation of the controls and crash sensor
    • The presence of a sufficient signal radiated from its antenna
 
skipone said:
Do you mean SPOT tracker, InReach and PLB?
Click to expand...
On the low end yes. Then there's SkyConnect, SpiderTrax, BlueSky, OuterLink, etc on the mid/high end of price.
 
skipone said:
Do you mean SPOT tracker, InReach and PLB?
Click to expand...
Please don't take offence in my questions. Are you a journalist writing about ELTs and PLBs? A student pilot or student looking for information. You obviously have little to no knowledge about the subject. There is a lot of documented information on this subject that would be easier and quicker to get than a POA forum.
 
Bell206 said:
FYI: some of the newer 406 ELTs have aux speakers options that will provide audible sound when the ELT transmits either during testing or actual activation. And while I don't quite follow the context of your questions if you have a fear of being left in the boonies there are other products out there that provide real time flight following and can pinpoint your location even without ELT activation.
Click to expand...
The aural warning was a requirement of the TSO that certifies 406s. From the Artex ME406 manual:

6)A warning buzzer is required under C126 TSO approval. The buzzer is powered by the ELT and therefore not dependent upon the aircraft battery for operation. It is not designed to operate continuously, but sounds at predetermined intervals and runs for shorter periods toward the end of ELT battery life.

The Manual: https://avsport.org/acft/Artex/ME406_manual.pdf

I usually found buzzers installed and working, but often found the mounting nowhere near compliance with this:

SUBTASK 25-62-30-990-006

F. RTCA DO-204, § 3.1.8 guidelines for mounting a ELT: a) The ELT shall be mounted to primary aircraft load carrying structures, such as trusses, bulkheads, longerons, spars, or floor beams. b) The mounts shall have a maximum static local deflection no greater than 0.1 inches (2.5 mm) when a force of 100 lbs (450 newtons) is applied to the mount in the most flexible direction. Deflection measurements shall be made with reference to another part of the aircraft not less than 1 foot (0.3 meters) nor more than 3 feet (1.0 meters) from the mounting location.

A. Location CAUTION: MANY ORIGINAL ELT INSTALLATIONS ARE INADEQUATE AS FAR AS UNIT LOCATION AND SURFACE RIGIDITY ARE CONCERNED. BECAUSE OF THE CRITICAL FUNCTION AN ELT PERFORMS, IT IS IMPORTANT THE INSTALLATION FOLLOWS THE INSTRUCTIONS AND RECOMMENDATIONS HEREIN.CAUTION: THE MOUNTING SURFACE MUST BE EXTREMELY RIGID; THEREFORE, MOUNTING AN ELT DIRECTLY TO THE AIRCRAFT SKIN IS UNACCEPTABLE. MOUNTING THE ELT DIRECTLY TO THE AIRCRAFT SKIN INDUCES “CRASH HIDING” VIBRATIONS AND PROVIDES A VERY POOR MOUNTING SURFACE.
 
Dan Thomas said:
"Sufficient signal" means a strength test. Avionics shops are normall
Click to expand...
FYI: only Canada and a few other countries require a measured signal trength test and special test equipment. In US no performance requirement and can be performed by AP.
 
Dan Thomas said:
I usually found buzzers installed and working, but often found the mounting nowhere near compliance with this:
Click to expand...
I agree with this. I have questioned several friends about the way they mounted their 406. I also feel the way they mounted the ELT would not stand up to the mounting requirements..:(
 
Dan Thomas said:
More than that. Annually, and fairly thoroughly too. An inspection for battery corrosion and G-switch operation means the ELT must come out and get opened up. "Sufficient signal" means a strength test. Avionics shops are normally the places that do this stuff.

  • An emergency locator transmitter (ELT) is required by 14 CFR, part 91, section 91.207, and must be inspected within 12 calendar months after the last inspection for the following:
    • Proper installation
    • Battery corrosion
    • Operation of the controls and crash sensor
    • The presence of a sufficient signal radiated from its antenna
Click to expand...
Yes, I was simplifying it. But depending on which ELT you have, it probably isn't done at an avionics shop, but by your IA doing the annual. The 121.5 ELTS are tested early by visual inspection and pushing the buttons and testing the G switch with the "whip" motion. The signal strength is tested by listening to it on another radio.
 
rk911 said:
the closest field to me is KDPA but it's too far to hear ground comms. either the pilot tripped it by accident or there was a hard touch n go.
Click to expand...
I would say that was me since I am based out of DPA, but I ripped out my 121 for a 406 2 years ago...
 
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