Deployable Elts... Doable?

[SJESOFFICER]

If the topic of automated deployment is about, how about this; the ELT deploys during rapid loss of altitude.

Good luck when you practice stalls.  Wouldnt work.  If you do a stall, or hit an air pocket, the ELT would deploy even though its not an emergency.  Not to mention if you have to do a rapid drop to get  below closing cloud cover.  Then you would have a box on a tether dangling off your plane until you can make it back to an airport. Then it would be dragged across the ground on landing, leaving parts and FOD strewn about the runway where other aircraft can suck it into their engines, or hit it as they land/takeoff.

could always deactivate automous alt release while practicing those things... just like they put safeties on ejection seats on the ground.  If your practicing those maneuvers  just bypass the alt. and let the other senors like the manual activation or hard (or crash landing) activate it ... food for thought

[lordmonar]

The problem now then....you are making a fail safe device more complicated.

The point is to make it simple, reliable and survivable.  If you start putting automatic deployment equipment on it...you are adding more points of failure into the system.

Bottom line....if you break your plane so bad that your ELT is broken....you probably did not survive the crash.  While it would still be nice to be able to find the wreckage so we can get the body back to the family....it would be better to find ways to make the antenna/transmitter more survivable instead of looking for ways to deploy it.

As it was pointed out....what happens if you get an unintentional deployment?  Now you got an ELT going off...not on some nice airport but in a tree 10 miles from the field.  Or you now have to pull off a landing with with 30 feet of cable dragging behind you.  Not to mention how much drag you will be adding to the plane.

For the ELT to be useful it needs to be near/on the plane when it crashes not 10 miles away where you engine cut out, or you hit that pocket of turbulence that ripped up your wing.

If the ELT deploys and it is on a tether....now you got a radio being slammed into the ground at landing speeds with out the benefit of the airframe to help protect it.

If the ELT deploys and you make it back to the airport or and off field landing you got the added drag, the possibility that it will entangle with the ILS, runway lights, the fence at the end of the runway or some other obstacle in the approach path.

So...while doable....it does not really improve the reliability of the system and introduces a lot more failure points and other hazards to flight safety to offset the benefits.

[Pumbaa]

Correct me if I am wrong but the "Black boxes" on commercial and military a/c have an underwater radio locator beacon.  These devices have an internal antenna.  They have enough power to transmit for 30 days @37.5 Khz (1 pulse per second) from as deep as 14k feet.  Thus some of the BBs that have been underwater have been found as well.... I would think and internal antenna would be the best option.  Harden the case a little more to survive impact.

[SarDragon]

Correct me if I am wrong but the "Black boxes" on commercial and military a/c have an underwater radio locator beacon.  These devices have an internal antenna.  They have enough power to transmit for 30 days @37.5 Khz (1 pulse per second) from as deep as 14k feet.  Thus some of the BBs that have been underwater have been found as well.... I would think and internal antenna would be the best option.  Harden the case a little more to survive impact.

Well, if you got your info from here, you didn't read the whole thing carefully. For underwater detection, the commercial a/c units transmits an ultrasonic (not radio) signal. They don't use an antenna at all, just a ceramic transducer to convert the electronic impulse into sound. RF doesn't travel well under, so normal transmitters are useless.

[Pumbaa]

Like I said.. correct me if I am wrong...

Still an internal coil antenna would be nice as a primary or even as a backup to an external antenna. 

[lordmonar]

Like I said.. correct me if I am wrong...

Still an internal coil antenna would be nice as a primary or even as a backup to an external antenna. 

Won't work unless it is outside the body of the aircraft.

Just like when we put foil around an ELT antenna to block the signal...the skin of the aircraft would block any signal coming from an internal antenna.

Hence the reason why the antenna is the weak point.  The ELT must be inside the aircraft for any chance of it surviving the crash but the antenna must be on the outside....and it is sometimes the first thing to go.

[♠SARKID♠]

could always deactivate automous alt release while practicing those things... just like they put safeties on ejection seats on the ground.  If your practicing those maneuvers  just bypass the alt. and let the other senors like the manual activation or hard (or crash landing) activate it ... food for thought

That would totally defeat the purpose.  Its times when your practicing stalls and all that when accidents happen.  If your engine cuts out, you can glide to a field, but if you get stuck in a death spin out of a stall, thats when you want that ELT deployed.  But believe me, when you are falling in a stall, the last thing you will be worried about is deploying that ELT.  Even in practice, your full concentration is on your controls trying to pull out, I know from expierience.  You aren't going to have the time, the mind, or ability to flip that switch to deploy the ELT.