Stupid transponder question, or, stumped by the wife

[John Kirksey]

So we were watching "Seconds From Disaster" on NGC last night, which
happened to be on AA 77. When they mentioned that seconds after gaining
control of the aircraft the hijackers turned off the transponder (along with
a brief explanation of what the transponder does), my wife simply says:

"That's stupid, why does something like that even have an on/off switch?"

I honestly never thought about it and couldn't answer her question. Does
anyone know?

Regards,

John K.

[Steve Foley]

Can you picture the radar screen in Boston/New York/Chicago/LAX when all the
planes on the ground are showing up? The radar sweeps by and shows 23 planes
lines up for the departure runway, superimposed on whoever is flying
overhead.



"John Kirksey" > wrote in message
news:_0YVe.24770$8h6.7135@trnddc09...
> So we were watching "Seconds From Disaster" on NGC last night, which
> happened to be on AA 77. When they mentioned that seconds after gaining
> control of the aircraft the hijackers turned off the transponder (along
with
> a brief explanation of what the transponder does), my wife simply says:
>
> "That's stupid, why does something like that even have an on/off switch?"
>
> I honestly never thought about it and couldn't answer her question. Does
> anyone know?
>
> Regards,
>
> John K.
>
>
>

[[email protected]]

Or what Chicago center sees in east central Wisconsin the last week of
July, first week of August.....

Only 10.5 months until the next bash!

[Paul kgyy]

When diagnosing electrical problems, it's helpful to be able to
selectively turn things off.

When I'm downloading data from my EDM, I turn all the radio gear off to
avoid unnecessary battery drain.

[[email protected]]

On Wed, 14 Sep 2005 16:15:54 GMT, "John Kirksey"
> wrote:

>So we were watching "Seconds From Disaster" on NGC last night, which
>happened to be on AA 77. When they mentioned that seconds after gaining
>control of the aircraft the hijackers turned off the transponder (along with
>a brief explanation of what the transponder does), my wife simply says:
>
>"That's stupid, why does something like that even have an on/off switch?"
>
>I honestly never thought about it and couldn't answer her question. Does
>anyone know?
>
>Regards,
>
>John K.
>
>

You need the ability to turn off the xponder inflight. One day I was
flying along and ATC called and asked me if anything was wrong. I said
everything is fine, why do you ask? They told me my xponder was
transmitting 7700. I looked at the xponder and confirmed that was NOT
what I have set - they said please turn it off - so I did.

When I'm on the ground, I set my xponder to standby, not off.

Ralph

[Mortimer Schnerd, RN]

wrote:
> You need the ability to turn off the xponder inflight. One day I was
> flying along and ATC called and asked me if anything was wrong. I said
> everything is fine, why do you ask? They told me my xponder was
> transmitting 7700. I looked at the xponder and confirmed that was NOT
> what I have set - they said please turn it off - so I did.
>
> When I'm on the ground, I set my xponder to standby, not off.


One other possible scenario: what if the transponder develops a short? Unless
you have a dedicated circuit breaker, you've got to have a way to take it our of
the loop.... otherwise it's fly around without ANY electrical device (turn off
the master).

Every electric device needs an on-off switch.



--
Mortimer Schnerd, RN

[sfb]

In military formation flying, only 1 plane has a transponder turned on.

"John Kirksey" > wrote in message
news:_0YVe.24770$8h6.7135@trnddc09...
> So we were watching "Seconds From Disaster" on NGC last night, which
> happened to be on AA 77. When they mentioned that seconds after
> gaining
> control of the aircraft the hijackers turned off the transponder
> (along with
> a brief explanation of what the transponder does), my wife simply
> says:
>
> "That's stupid, why does something like that even have an on/off
> switch?"
>
> I honestly never thought about it and couldn't answer her question.
> Does
> anyone know?
>
> Regards,
>
> John K.
>
>
>

[Peter R.]

sfb > wrote:

> In military formation flying, only 1 plane has a transponder turned on.

Isn't this true with GA formation flying as well?

--
Peter
























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[RK Henry]

On Wed, 14 Sep 2005 10:36:16 -0700, wrote:

>On Wed, 14 Sep 2005 16:15:54 GMT, "John Kirksey"
> wrote:


>When I'm on the ground, I set my xponder to standby, not off.

I've often wished my transponder had a standby position. It's either
on or off. And when I turn it off, it forgets the squawk code and I
have to reset it. It's a bit of a pain.

RK Henry

[JohnH]

> "That's stupid, why does something like that even have an on/off
> switch?"

For the very reason many men wished thier wives had one.

[Steven P. McNicoll]

"John Kirksey" > wrote in message
news:_0YVe.24770$8h6.7135@trnddc09...
>
> So we were watching "Seconds From Disaster" on NGC last night, which
> happened to be on AA 77. When they mentioned that seconds after gaining
> control of the aircraft the hijackers turned off the transponder (along
> with
> a brief explanation of what the transponder does), my wife simply says:
>
> "That's stupid, why does something like that even have an on/off switch?"
>
> I honestly never thought about it and couldn't answer her question. Does
> anyone know?
>

So it can be turned off when need be, like when it's providing erroneous
information.

[Steven P. McNicoll]

"Peter R." > wrote in message
...
>
> Isn't this true with GA formation flying as well?
>

Yes.

[Newps]

Steve Foley wrote:
> Can you picture the radar screen in Boston/New York/Chicago/LAX when all the
> planes on the ground are showing up? The radar sweeps by and shows 23 planes
> lines up for the departure runway, superimposed on whoever is flying
> overhead.

Irrelavant. The radar computer has software that will not show any
target within the user specified distance from the radar antenna. We
set ours to 1 mile. There are also altitude filters that can be set.
There is no good reason to ever turn your transponder off or to STBY
unless ATC asks you to or you somehow know it's not working properly.

[Steven P. McNicoll]

"Newps" > wrote in message
...
>
> Irrelavant. The radar computer has software that will not show any target
> within the user specified distance from the radar antenna. We set ours to
> 1 mile. There are also altitude filters that can be set.

Facilities that do radar approaches don't tend to filter out these targets.


>
> There is no good reason to ever turn your transponder off or to STBY
> unless ATC asks you to or you somehow know it's not working properly.
>

ASR on the field is good reason to turn your transponder off or to STBY
without ATC request.

[kontiki]

JohnH wrote:

>>"That's stupid, why does something like that even have an on/off
>>switch?"
>
>
> For the very reason many men wished thier wives had one.
>
>

Oh man... that's brutal.

[Dave]

But oh so true in some cases. (we love our wives)

"kontiki" > wrote in message
...
> JohnH wrote:
>
>>>"That's stupid, why does something like that even have an on/off
>>>switch?"
>>
>>
>> For the very reason many men wished thier wives had one.
>
> Oh man... that's brutal.
>

[Frank Ch. Eigler]

Newps > writes:

> > Can you picture the radar screen in Boston/New York/Chicago/LAX
> > when all the planes on the ground are showing up? The radar sweeps
> > by and shows 23 planes lines up for the departure runway,
> > superimposed on whoever is flying overhead.

> Irrelavant. The radar computer has software that will not show any
> target within the user specified distance from the radar antenna.
> [...]

Maybe, but it is still a problem for aircraft with TCAS, who
receive false alarms due to the ground traffic.

- FChE

[RST Engineering]

Then why doesn't the stall warning horn have one?

Jim

> Every electric device needs an on-off switch.

[Bob Noel]

In article >,
(Frank Ch. Eigler) wrote:

>
> Maybe, but it is still a problem for aircraft with TCAS, who
> receive false alarms due to the ground traffic.

not if their radio altimeter is working.

--
Bob Noel
no one likes an educated mule

[Blueskies]

"RST Engineering" > wrote in message ...
> Then why doesn't the stall warning horn have one?
>
> Jim
>
>> Every electric device needs an on-off switch.
>
>

Isn't it good to have these electronic devices turned off when the plane is started to save them from all the surges on
the DC buss?

[Newps]

Frank Ch. Eigler wrote:

> Newps > writes:
>
>
>>>Can you picture the radar screen in Boston/New York/Chicago/LAX
>>>when all the planes on the ground are showing up? The radar sweeps
>>>by and shows 23 planes lines up for the departure runway,
>>>superimposed on whoever is flying overhead.
>
>
>>Irrelavant. The radar computer has software that will not show any
>>target within the user specified distance from the radar antenna.
>>[...]
>
>
> Maybe, but it is still a problem for aircraft with TCAS, who
> receive false alarms due to the ground traffic.
>

Then their TCAS has problems. Properly operating TCAS knows the
aircraft is stationary plus below a certain altitude it is advisory in
nature. If this were a problem I would hear about it from aircraft with
TCAS. Not once in the last 17 years has an aircraft with TCAS so much
as mentioned they were receiving an alert from an aircraft holding short
of the runway.

[Mortimer Schnerd, RN]

JohnH wrote:
>> "That's stupid, why does something like that even have an on/off
>> switch?"
>
> For the very reason many men wished thier wives had one.



Oh, but they do. My ex-wife had hers turned off for weeks at a time.



--
Mortimer Schnerd, RN

[Chris Kennedy]

RST Engineering wrote:

> Then why doesn't the stall warning horn have one?

The stall warning horn in all of my aircraft have two: The CB and the
one labeled "master".

[Mortimer Schnerd, RN]

RST Engineering wrote:
>> Every electric device needs an on-off switch.
>
> Then why doesn't the stall warning horn have one?



The stall warning horn more than likely has a circuit breaker. And some stall
horns, like on the C-152, are pneumatic.



--
Mortimer Schnerd, RN

[Dave Stadt]

"RST Engineering" > wrote in message
...
> Then why doesn't the stall warning horn have one?

Cause nobody has yet found a way to turn off a butt which is what real
airplanes have for stall warning indicators. :-)

> Jim
>
> > Every electric device needs an on-off switch.
>
>

[Dave Stadt]

"Peter R." > wrote in message
...
> sfb > wrote:
>
> > In military formation flying, only 1 plane has a transponder turned on.
>
> Isn't this true with GA formation flying as well?

Yes, and ATC will let you know if more that one in the formation has their
transponder on.

> --
> Peter
>
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[RST Engineering]

In most Cessnas with electric horns, the CB is a hidden "auto-reset" device
that you can't pull. The master doesn't count.

Jim


"Chris Kennedy" > wrote in message
...
> RST Engineering wrote:
>
>> Then why doesn't the stall warning horn have one?
>
> The stall warning horn in all of my aircraft have two: The CB and the
> one labeled "master".
>

[RST Engineering]

"Mortimer Schnerd, RN" > wrote in message
...
> RST Engineering wrote:
>>> Every electric device needs an on-off switch.
>>
>> Then why doesn't the stall warning horn have one?
>
>
>
> The stall warning horn more than likely has a circuit breaker.

See my reply to Chris Kennedy


And some stall
> horns, like on the C-152, are pneumatic.

That's rather gratuitous of you.

Jim

[Steven P. McNicoll]

"RST Engineering" > wrote in message
...
>
> Then why doesn't the stall warning horn have one?
>

It does. You'll find it in the wing leading edge.

[Chris Kennedy]

RST Engineering wrote:

> In most Cessnas with electric horns, the CB is a hidden "auto-reset" device
> that you can't pull. The master doesn't count.

Fair enough. The fact that most Cessnas don't have a CB that you can
pull doesn't change the fact that my aircraft do. Perhaps that's a bit
pedantic, but it remains a valid response to the question you posed.

[Steven P. McNicoll]

"RST Engineering" > wrote in message
...
>
> In most Cessnas with electric horns, the CB is a hidden "auto-reset"
> device that you can't pull. The master doesn't count.
>

Does the lift detector count?

[BTIZ]

no electronic horn.. no way to turn it off.. as in the light weight
cessnas..

"Chris Kennedy" > wrote in message
...
> RST Engineering wrote:
>
>> Then why doesn't the stall warning horn have one?
>
> The stall warning horn in all of my aircraft have two: The CB and the
> one labeled "master".
>

[Thomas Borchert]

John,

> I honestly never thought about it and couldn't answer her question. Does
> anyone know?
>

Heard twice within the last two months on ATC:

N12345, your transponder is indicating FL240, say altitude.
N12345, altitude 3000 feet
N12345, in that case, please turn off your transponder and have it
repaired

or words to that effect.

--
Thomas Borchert (EDDH)

[Stefan]

Newps wrote:

> Irrelavant. The radar computer has software that will not show any
> target within the user specified distance from the radar antenna. We
> set ours to 1 mile. There are also altitude filters that can be set.
> There is no good reason to ever turn your transponder off or to STBY
> unless ATC asks you to or you somehow know it's not working properly.

There's still another problem called FRUIT (False Replies Unsynchronised
in Time). The radar bean has a width of about 3 degrees. All the
transponders in this small area respond with their code as soon as the
radar beam hits them. A major installation can handle up to ten codes
simultaneously. But if on a nice Sunday several hundred VFR air planes
are about the situation has arisen where the targets could no longer be
properly separated, with the result that the important echoes of
commercial traffic disappeared in the maze.

The controller can erase the VFR echoes, but when the radar con not read
them anymore the legibility of the remaining echoes is not improved.
Actually, this is one of the reasons why mode S is introduced.

Stefan

[Steven P. McNicoll]

"Thomas Borchert" > wrote in message
...
>
> Heard twice within the last two months on ATC:
>
> N12345, your transponder is indicating FL240, say altitude.
> N12345, altitude 3000 feet
> N12345, in that case, please turn off your transponder and have it
> repaired
>
> or words to that effect.
>

The words should have been "stop altitude squawk."

[Peter R.]

Thomas Borchert > wrote:

> Heard twice within the last two months on ATC:
>
> N12345, your transponder is indicating FL240, say altitude.
> N12345, altitude 3000 feet
> N12345, in that case, please turn off your transponder and have it
> repaired
>
> or words to that effect.

I am surprised that ATC would have the pilot turn off the transponder. Why
wouldn't they simply ask to stop squawking altitude (switch to Mode A)?

--
Peter
























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