Sponsor Message:
Aviation Technical / Operations Forum
My Starred Topics | Profile | New Topic | Forum Index | Help | Search 
Transponder Question  
User currently offlineCOrocks From United States of America, joined Feb 2001, 1215 posts, RR: 0
Posted (5 years 6 months 3 weeks 14 hours ago) and read 4117 times:

I was watching an documentary on 9/11 yesterday and they were talking about how the hijackers turned of the transponders which made it more difficult to track them. Dumb question: Why do pilots even have the option of turning this off? Why would there ever be a legitimate reason to turn it off? I would think you would always want to know where a commercial jet was.

13 replies: All unread, jump to last
 
User currently offlineN353SK From United States of America, joined Jun 2006, 833 posts, RR: 0
Reply 1, posted (5 years 6 months 3 weeks 14 hours ago) and read 4118 times:

Transponders are turned off while on the ground (at most airports) and in the case of faulty equipment.

User currently offlineTinpusher007 From United States of America, joined Feb 2005, 983 posts, RR: 1
Reply 2, posted (5 years 6 months 3 weeks 14 hours ago) and read 4108 times:

On the ground, the transponder is turned off or put in standby mode. However, at most big airports, it is commonplace for aircraft to taxi with their transponders on.


"Flying isn't inherently dangerous...but very unforgiving of carelessness, incapacity or neglect."
User currently offlineSCCutler From United States of America, joined Jan 2000, 5615 posts, RR: 28
Reply 3, posted (5 years 6 months 3 weeks 14 hours ago) and read 4108 times:

In addition, of course, a transponder can provide faulty information such as in accurate altitude or improper "squawk code," or could fail in some other way. Like most every other functional device on the aircraft, the transponder can be switched on or off, and controlled, byth epilots.

Which, of course, is as it should be.



...three miles from BRONS, clear for the ILS one five approach...
User currently offlineFLY2HMO From , joined Dec 1969, posts, RR:
Reply 4, posted (5 years 6 months 3 weeks 14 hours ago) and read 4098 times:



Quoting COrocks (Thread starter):
I would think you would always want to know where a commercial jet was.

Controllers can still see primary (non-transponder) targets on their radar scopes.


User currently offlineFuturePilot16 From United States of America, joined Mar 2007, 2035 posts, RR: 0
Reply 5, posted (5 years 6 months 3 weeks 14 hours ago) and read 4086 times:



Quoting SCCutler (Reply 3):
In addition, of course, a transponder can provide faulty information such as in accurate altitude or improper "squawk code," or could fail in some other way. Like most every other functional device on the aircraft, the transponder can be switched on or off, and controlled, byth epilots.

Which, of course, is as it should be.

That's another thing I don't understand, why do they make it that everything can be turned on and off. I was watching a documentary about a fedex flight that was attacked by a pilot who was jumpseating. The documentary stated that the man turned off the CVR/FDR prior to starting the attack. Why should there even be an option to turn off something so vital?



"The brave don't live forever, but the cautious don't live at all."
User currently offlineFLY2HMO From , joined Dec 1969, posts, RR:
Reply 6, posted (5 years 6 months 3 weeks 14 hours ago) and read 4065 times:



Quoting FuturePilot16 (Reply 5):
Why should there even be an option to turn off something so vital?

Because sometimes what happens in the cockpit stays in the cockpit  Wink  duck 


User currently offlineThePinnacleKid From United States of America, joined Feb 2005, 731 posts, RR: 8
Reply 7, posted (5 years 6 months 3 weeks 11 hours ago) and read 4007 times:



Quoting FuturePilot16 (Reply 5):
That's another thing I don't understand, why do they make it that everything can be turned on and off. I was watching a documentary about a fedex flight that was attacked by a pilot who was jumpseating. The documentary stated that the man turned off the CVR/FDR prior to starting the attack. Why should there even be an option to turn off something so vital?

They're not with an On/Off switch... at least not in most aircraft... esp. not in the one I fly... but, you have the ability to turn it off thanks to the handy gadget called a Circuit Breaker... and you have to have them and they have to be accessible to the flight crew... so yeah, in a way it's required that we have the ability to turn them off...



"Sonny, did we land? or were we shot down?"
User currently offlineChrisjw From United States of America, joined Jan 2009, 123 posts, RR: 0
Reply 8, posted (5 years 6 months 3 weeks 10 hours ago) and read 3989 times:



Quoting FLY2HMO (Reply 6):
The documentary stated that the man turned off the CVR/FDR prior to starting the attack. Why should there even be an option to turn off something so vital?

I know the exact documentary your talking about, it was a good one.

Problem is what happens if the CVR/FDR shorts out and theres no circuit breaker for it. You would have to shut down the entire electrical system for the plane to avoid a fire vs simply pulling the circuit breaker for it. As we all know, fire and aircraft don't get along to well.

Nobody except pilots and maybe an FA has access to the circuit breakers (the guy in the documentary was a pilot for Fedex).


User currently offlineHAWK21M From India, joined Jan 2001, 31712 posts, RR: 56
Reply 9, posted (5 years 6 months 3 weeks 9 hours ago) and read 3959 times:



Quoting Chrisjw (Reply 8):
Problem is what happens if the CVR/FDR shorts out and theres no circuit breaker for it. You would have to shut down the entire electrical system for the plane to avoid a fire vs simply pulling the circuit breaker for it.

You don't pull a CB in flight,The CB is supposed to trip.
regds
MEL.



Think of the brighter side!
User currently offlineMir From United States of America, joined Jan 2004, 21864 posts, RR: 55
Reply 10, posted (5 years 6 months 3 weeks 9 hours ago) and read 3942 times:



Quoting HAWK21M (Reply 9):
You don't pull a CB in flight,The CB is supposed to trip.

In an ideal world, yes. But if you've got a component that's producing an electrical fire and the CB isn't tripping, it's time to pull it.

-Mir



7 billion, one nation, imagination...it's a beautiful day
User currently offlinePER744 From Australia, joined Mar 2003, 405 posts, RR: 2
Reply 11, posted (5 years 6 months 3 weeks 9 hours ago) and read 3941 times:

I understand that on more modern aircraft, the CVR breaker works in conjunction with a fuse, so simply pulling the breaker won't disable the CVR unless the fuse also burns out, although I can't find a reference for this.

And a faulty transponder can definitely cause problems for ATC, better to use a flight plan track and procedural sep standards than an inaccurate radar track.


User currently offlineUAXDXer From United States of America, joined Jul 2004, 765 posts, RR: 3
Reply 12, posted (5 years 6 months 3 weeks 8 hours ago) and read 3916 times:



Quoting PER744 (Reply 11):
I understand that on more modern aircraft, the CVR breaker works in conjunction with a fuse, so simply pulling the breaker won't disable the CVR unless the fuse also burns out, although I can't find a reference for this.

Simply pulling a circuit breaker will disable whatever system it is associated with on modern aircraft. Ever notice on the circuit breaker panels on a/c? The are all on a grid so they can easily be found incase the CB needs to be pulled.


View Large View Medium
Click here for bigger photo!

Photo © Stil



Quoting PER744 (Reply 11):
And a faulty transponder can definitely cause problems for ATC, better to use a flight plan track and procedural sep standards than an inaccurate radar track.

ATC Radar can still track an aircraft when the transponder is turned off. It just does not receive information specific to that target such as altitude and speed.



It takes a bug to hit a windsheild but it takes guts to stick
User currently offlinePhilSquares From , joined Dec 1969, posts, RR:
Reply 13, posted (5 years 6 months 3 weeks 4 hours ago) and read 3871 times:



Quoting PER744 (Reply 11):
I understand that on more modern aircraft, the CVR breaker works in conjunction with a fuse, so simply pulling the breaker won't disable the CVR unless the fuse also burns out, although I can't find a reference for this.

What you're talking about is a RCCB, Remote Controlled Circuit Breaker. Those are generally used for high amp items. For the CVR and DFDR the CBs are in the cockpit and pulling a CB like that will cut the power from the unit.


Top Of Page
Forum Index

Reply To This Topic Transponder Question
Username:
No username? Sign up now!
Password: 


Forgot Password? Be reminded.
Remember me on this computer (uses cookies)
  • Tech/Ops related posts only!
  • Not Tech/Ops related? Use the other forums
  • No adverts of any kind. This includes web pages.
  • No hostile language or criticizing of others.
  • Do not post copyright protected material.
  • Use relevant and describing topics.
  • Check if your post already been discussed.
  • Check your spelling!
  • DETAILED RULES
Add Images Add SmiliesPosting Help

Please check your spelling (press "Check Spelling" above)


Similar topics:More similar topics...
TWA800 Fuel Tank Question posted Tue Jun 2 2009 00:22:26 by AAden
ERJ Steering Question posted Sun May 31 2009 15:49:06 by Mycrj17
Technical Question About Cockpit In General posted Mon May 25 2009 10:40:50 by Flaps30
Question About 727 Nose posted Wed May 20 2009 19:32:18 by DreamsUnited
Question About A320 Series Wing posted Tue May 19 2009 19:20:41 by Teo747
Quad Double Engine Failure Question posted Thu May 14 2009 07:42:09 by ZBBYLW
Question About SQC7334 ORD-DFW 09MAY09 posted Sat May 9 2009 20:59:03 by DescendVia
Aircraft Leasing Question posted Fri May 8 2009 15:22:39 by DreamsUnited
Question About The Thrust Reverse posted Wed May 6 2009 20:10:24 by Vietsky
A Question For A Pilot About Mach posted Mon May 4 2009 15:14:17 by Ozark1

Sponsor Message:
Printer friendly format