CanadianNorth
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ELT Question (737)

Wed Jun 27, 2007 11:04 am

Well today during the turn we were giving one of our 737-200s a quick groom, and it was just us groomers in the rear cabin and some rampers down on the ground, as well as a mechanic in the bridge.

So we were working away and out of nowhere off goes an alarm type thing. The mechanic ran into the flt deck and turned it off, and the started yelling out the door at the ramp folks if they hit the plane. They said nobody hit anything that they know of, and then the mechanic came back and asked us if we saw/heard anything hit the plane, as the ELT had gone off and it is only designed to do that if the plane hits something hard enough.

He figured the only thing it could be was the jet beside us (a Jazz CRJ705 departing for Vancouver) that turned out from the terminal and gave us a good jetblast (I did feel the plane shake slightly and it was easily heard via the open door nearby). But I was thinking, I've never heard of an ELT going off on a hard landing, so how would some jetblast set it off? The jet did leave pretty much on time so I guess it was true that nobody hit the plane with any ramp vehicles or anything, atleast not hard enough to break anything...

Anyhow, long enough post. Looking forward to any replies from anyone with ELT and/or 737 experience...


CanadianNorth
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KELPkid
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RE: ELT Question (737)

Wed Jun 27, 2007 1:18 pm

ELT's (at least the ones in GA planes  Wink ) go off far more often than the general public realizes...hard landings, people being careless with the ELT on the ground, etc. etc. Usually, the only audible sign of an ELT activation is when one tunes an air band radio to 121.5. Quite a few amateur radio 2-meter repeaters are also programmed to detect an ELT activation, and one that I know of even triangulates the signal and broadcasts a bearing to the ELT when it happens. Apart from that, you would have to have some sort of triangulation equipment (like the Swivel Chair Patrol, err, Civil Air Patrol) does to find it.
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HAWK21M
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RE: ELT Question (737)

Wed Jun 27, 2007 7:16 pm

Impact type ELT needs a felt impact to trigger if in Arm position.The Water activated needs to be immersed in water/liquid.

I don't know how a jet blast or a loading movement can trigger the ELT.Makes no sense.Unless someone triggered the ELT sw in the Flt deck.

regds
MEL
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KELPkid
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RE: ELT Question (737)

Thu Jun 28, 2007 2:03 am

Quoting HAWK21M (Reply 2):
mpact type ELT needs a felt impact to trigger if in Arm position.The Water activated needs to be immersed in water/liquid.

I don't know how a jet blast or a loading movement can trigger the ELT.Makes no sense.Unless someone triggered the ELT sw in the Flt deck.

Hi MEL, in regards to the original poster's question: are the evacuation alarm and ELT in any way interconnected in the 737?
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Ralgha
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RE: ELT Question (737)

Thu Jun 28, 2007 2:15 am

Quoting KELPkid (Reply 1):
Apart from that, you would have to have some sort of triangulation equipment (like the Swivel Chair Patrol, err, Civil Air Patrol) does to find it.

Not really, all you need is a hand held receiver, hold it up against your body, and turn around in circles. When the signal is quietest, its source is behind you. When I was an instructor at a small FBO I used this method to successfully find ELTs on the airport that had been accidentaly activated.
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KELPkid
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RE: ELT Question (737)

Thu Jun 28, 2007 2:44 am

Quoting Ralgha (Reply 4):
Not really, all you need is a hand held receiver, hold it up against your body, and turn around in circles. When the signal is quietest, its source is behind you. When I was an instructor at a small FBO I used this method to successfully find ELTs on the airport that had been accidentaly activated.

"Hi Bob, what you doing? It looks quite foolish..."

"Well John, it's called the ELT dance. We do it at this field anytime an ELT goes off to try to locate the source..."  laughing 
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Ralgha
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RE: ELT Question (737)

Thu Jun 28, 2007 3:48 am

So you would rather we wasted the taxpayer's money by doing nothing and waiting for the CAP or sheriff to drag themselves out there with DF gear to find something that we found in ~5 minutes? I'll keep that in mind next time. I'll ask them to send the bill to you instead of drawing on their normal funding to cover it if you like.
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CanadianNorth
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RE: ELT Question (737)

Thu Jun 28, 2007 3:57 am

Quoting HAWK21M (Reply 2):
Unless someone triggered the ELT sw in the Flt deck.

The only ones in the plane at the time were us in the back and the mechanic around the front door or on the bridge, so the flt deck was unoccupied at the time.

Quoting KELPkid (Reply 3):
Hi MEL, in regards to the original poster's question: are the evacuation alarm and ELT in any way interconnected in the 737?

Never thought of an evacuation alarm, but when the ELT supposedly went off an alarm could be heard reasonably loud in the last few rows where I was, and I'm assuming at the front as well by the immediate reaction of the mechanic...

Thanks for all the replies sofar...


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KELPkid
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RE: ELT Question (737)

Thu Jun 28, 2007 4:23 am

Quoting Ralgha (Reply 6):
So you would rather we wasted the taxpayer's money by doing nothing and waiting for the CAP or sheriff to drag themselves out there with DF gear to find something that we found in ~5 minutes? I'll keep that in mind next time. I'll ask them to send the bill to you instead of drawing on their normal funding to cover it if you like.

Not what I said at all. I just found some humor in the situation Big grin
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Markhkg
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RE: ELT Question (737)

Thu Jun 28, 2007 4:31 am

Quoting KELPkid (Reply 3):
are the evacuation alarm and ELT in any way interconnected in the 737?

No, they are not interconnected.

Quoting CanadianNorth (Reply 7):
Never thought of an evacuation alarm, but when the ELT supposedly went off an alarm could be heard reasonably loud in the last few rows where I was

The 737 is not typically equipped with an evacuation alarm, but it is a customer option. Typically, evacuations on board 737s are initiated with the flight deck providing a verbal command over the PA.
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avt007
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RE: ELT Question (737)

Thu Jun 28, 2007 6:01 am

Some of the newer ELTs have a speaker mounted next to the unit, so you can tell when it goes off. It's also used for testing the ELT. The number of beeps indicate a good or bad unit.
 
AirframeAS
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RE: ELT Question (737)

Thu Jun 28, 2007 11:03 am

Excuse my ignorance, being an A&P student in my final semseter....but what the heck does ELT stand for? The A&P program didn't cover this in Airframe Electronics.
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CanadianNorth
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RE: ELT Question (737)

Thu Jun 28, 2007 11:13 am

Quoting AirframeAS (Reply 11):
but what the heck does ELT stand for

Emergency Locator Transmitter or something along those lines. Basically it gets installed on most aircraft and what it's supposed to do is be triggered by the plane crashing, and it sends out a signal so the search and rescue people can pick up the signal and use it to locate the aircraft.


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AirframeAS
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RE: ELT Question (737)

Thu Jun 28, 2007 11:20 am

Quoting CanadianNorth (Reply 12):
Emergency Locator Transmitter

Ok, I am a moron! I should HAVE known that! They did teach that in the program, but only applied it to a Cessna.
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CanadianNorth
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RE: ELT Question (737)

Thu Jun 28, 2007 1:37 pm

Quoting AirframeAS (Reply 13):
They did teach that in the program, but only applied it to a Cessna.

They can be put on pretty much any aircraft type as far as I know, I've personally seen them on Cessnas, Helicopters and 737s.


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united757
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RE: ELT Question (737)

Thu Jun 28, 2007 1:41 pm

Just the other day one went off at my flight school, we were taxing out when one of the fire trucks stopped us, and had us check our ELT. After that we kept tuning into 121.5 to see if they had found which plane it was. They were also making anouncments from time to time on the ground frequency asking people to check their ELT's.
 
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HAWK21M
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RE: ELT Question (737)

Thu Jun 28, 2007 4:20 pm

Quoting KELPkid (Reply 3):
Hi MEL, in regards to the original poster's question: are the evacuation alarm and ELT in any way interconnected in the 737

There is No connection.

Quoting CanadianNorth (Reply 7):
The only ones in the plane at the time were us in the back and the mechanic around the front door or on the bridge, so the flt deck was unoccupied at the time.

Probably Malfunction.

Quoting Avt007 (Reply 10):
Some of the newer ELTs have a speaker mounted next to the unit, so you can tell when it goes off. It's also used for testing the ELT. The number of beeps indicate a good or bad unit.

The Unit [Impact type] is located at the Aft near the Empennage on a B737.The Speaker & Test/On switch is wirelocked in On position & located on P5 overhead panel.

Quoting AirframeAS (Reply 11):
Excuse my ignorance, being an A&P student in my final semseter....but what the heck does ELT stand for

http://en.wikipedia.org/wiki/Emergen...y_Position-Indicating_Radio_Beacon

regds
MEL
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AirframeAS
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RE: ELT Question (737)

Fri Jun 29, 2007 12:22 pm

Quoting HAWK21M (Reply 16):
http://en.wikipedia.org/wiki/Emergen...y_Position-Indicating_Radio_Beacon

Thanks for the link, Hawk. But I never use wikipedia for obvious reasons.
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troubleshooter
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RE: ELT Question (737)

Fri Jun 29, 2007 1:46 pm

Quoting HAWK21M (Reply 2):
Impact type ELT needs a felt impact to trigger if in Arm position.The Water activated needs to be immersed in water/liquid.

I' ve never seen a "water activated" ELT. Not on the B737 and not on a lot of other types I' ve worked on. ELTs can be activated either manually or automatically by the internal g-switch.

Are you sure you don' t mix it with the CVR and FDR???
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Markhkg
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RE: ELT Question (737)

Fri Jun 29, 2007 2:01 pm

Quoting Troubleshooter (Reply 18):

I' ve never seen a "water activated" ELT.

The cabin portable ELTs (the ones the flight attendants are meant to take with them) are frequently water activated. One of the more popular one requires the placement of the unit into an electrolyte solution (sea water or thin soup, urine, etc.). If you put it into the sea (like tying it to a raft) the tape automatically comes undone to deploy the antennae.

http://www.acrelectronics.com/pdfs/Y1-03-0090-2D.pdf
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HAWK21M
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RE: ELT Question (737)

Fri Jun 29, 2007 9:30 pm

Quoting AirframeAS (Reply 17):
Thanks for the link, Hawk. But I never use wikipedia for obvious reasons

True.But some things are believable.

Quoting Troubleshooter (Reply 18):
I' ve never seen a "water activated" ELT. Not on the B737 and not on a lot of other types I' ve worked on. ELTs can be activated either manually or automatically by the internal g-switch.Are you sure you don' t mix it with the CVR and FDR???



Water Activated ELT is a portable unit.Our B737 Freighters have them.On ctc with water the cord holding the Antenna loosens & the Antenna goes to a vertical position as its spring loaded.There is a Water activating device that supplies charge to the ELT for transmission.


regds
MEL
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troubleshooter
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RE: ELT Question (737)

Sat Jun 30, 2007 2:03 am

Quoting MarkHKG (Reply 19):
The cabin portable ELTs (the ones the flight attendants are meant to take with them) are frequently water activated. One of the more popular one requires the placement of the unit into an electrolyte solution (sea water or thin soup, urine, etc.). If you put it into the sea (like tying it to a raft) the tape automatically comes undone to deploy the antennae.



Quoting HAWK21M (Reply 20):
Water Activated ELT is a portable unit.Our B737 Freighters have them.On ctc with water the cord holding the Antenna loosens & the Antenna goes to a vertical position as its spring loaded.There is a Water activating device that supplies charge to the ELT for transmission.

Thanks guys! I've never seen that type of ELT. Our aircrafts have all a fixed ELT installed.
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HAWK21M
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RE: ELT Question (737)

Mon Jul 02, 2007 10:35 pm

Quoting Troubleshooter (Reply 21):
Our aircrafts have all a fixed ELT installed

Our Freighter use both the Impact Type & water Activated type.
regds
MEL
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