Dual Xpndr

[Kream926]

just seen an airplane with dual transponders, why? what the point

 

[SPBRIAN]

Typicaly because it's a piece of operating equipment, and we all know that things never break. Also for the aircraft that have dual transponders (pressurized, flown high or into high density airspace) there's too many restrictions imposed upon aircraft without a mode C.

 

[Godvek]

Transponders are like women, two are better than one.

 

[nosehair]

I remember when I first saw two radios or two vor's in an airplane. Had the same question...why?

 

[MD11Drvr]

2 Of everything is one more than you need, but just what you need when Mr. Murphy shows up...........

 

[GravityHater]

here's my guess:
Money.
Txpdr inop? No go! Wait we have 130 pax in the back, waiting to get somewhere. Thats a costly problem, fixed with a $5K box of redundancy.
My guess is predicated on what I think a typical MEL would say.

 

[Kawasumi_Kichou]

What kind of aircraft was it?

I seem to recall many Beech Starships having two transponders. Something about them being rather stealthy on primary radar returns--very little skin paint.

Or maybe that memory was from all that Guinness I surrounded back in the day...

 

[FN FAL]

There must a be a difference between our two transponders...atc has written our management and asked that when we depart class c airspace that we use tx #2 and when we arrive we should use tx #1.

Sometimes when one of our pilots has a problem with a transponder, they'll ask which one he is using.

 

[Lead Sled]

There must a be a difference between our two transponders...atc has written our management and asked that when we depart class c airspace that we use tx #2 and when we arrive we should use tx #1.

Sometimes when one of our pilots has a problem with a transponder, they'll ask which one he is using.

Dual transponders are installed for precisely the reason the Spbrian mentioned. As far as FN Fal's comments go how would ATC even know which transponder you're using? They're 100% identical and interchangeable in every aircraft I've ever flown. What he's probably dealing with is a certain controller who's thinking outside the box. I've flown airplanes that are capable of outclimbing the altitude reporting capibility of the encoder. This can be caused by various things and sometimes geometry between the deck angle, aircraft antenna location and location of the ground station can all interact to block the signal. We used to fly out of an airport in the Pacific Northwest in a Gulfstream G-100 where this happened all of the time. Simply switching the transponders (changing the antenna) normally got things working again.

'Sled

 

[Kream926]

it was a cardinal 177

 

[urflyingme?!]

The REAL reason is that you're flying a 1900 with no autopilot and you GASP find yourself 600 feet off altitude. When ATC asks, you simply say ya we'll switch to #2xpndr. Then you climb and cycle baby!

 

[Lead Sled]

The REAL reason is that you're flying a 1900 with no autopilot and you GASP find yourself 600 feet off altitude. When ATC asks, you simply say ya we'll switch to #2xpndr. Then you climb and cycle baby!

Naw, that NEVER happens.

'Sled

 

[Kream926]

The REAL reason is that you're flying a 1900 with no autopilot and you GASP find yourself 600 feet off altitude. When ATC asks, you simply say ya we'll switch to #2xpndr. Then you climb and cycle baby!

wouldnt it still send back 600' off since its reading pressure altitude?

 

[A1FlyBoy]

Piper Mirage & Meridian now come with dual xpdrs as standard equipment...

 

[FN FAL]

As far as FN Fal's comments go how would ATC even know which transponder you're using? They're 100% identical and interchangeable in every aircraft I've ever flown. What he's probably dealing with is a certain controller who's thinking outside the box. 'Sled

That's a negative, ATC has had communication with our management. DO says...transponder two for departure, transponder one for arrivals.

When there is problem, the controllers will ask which transponder we are using. Sometimes the pilot staff forgets the rule.

We have two different kind of transponders...I'll ask tomorrow why the ATC has made the request for specific transponder usage. I believe our aircraft is set up with one Mode-S transponder and one regular Mode-C transponder.

There is a difficulty issue and I don't believe our caravans are out climbing ATC's radar capability. IF anything, we might be sending their radar equipment into an ADD mode.

 

[jknight8907]

No. What you do is tell them you'll switch to the second transponder, then turn it off. While it's off get back on your altitude, then turn it back on. Makes it look like it was an xpndr problem.

 

[ISaidRightTurns]

I can't figure out why any controller would care about which transponder you were on. I don't think our system gets any mode S info. Just the code and altitude information.

Is this out of a small approach control that they ask for it? Does it happen often?

That's a negative, ATC has had communication with our management. DO says...transponder two for departure, transponder one for arrivals.

When there is problem, the controllers will ask which transponder we are using. Sometimes the pilot staff forgets the rule.

We have two different kind of transponders...I'll ask tomorrow why the ATC has made the request for specific transponder usage. I believe our aircraft is set up with one Mode-S transponder and one regular Mode-C transponder.

There is a difficulty issue and I don't believe our caravans are out climbing ATC's radar capability. IF anything, we might be sending their radar equipment into an ADD mode.

 

[WMUSIGPI]

In the Lear 31a #1 is used when the left seater is flying #2 when the right seater is. It's for RVSM because each is tied to its side's air data computer (altimeter)
Of course the two altimeters are never supposed to be reading far enough apart to make a difference but who knows.