NGT 9000 Transponder: Ext. Fail

[byrdflyr]

I had a new L3 LYNX NGT 9000 installed in February.  On a recent trip from Durango to Colorado Springs, everything went perfectly with ATC - had radar services, until passing Pikes Peak and getting handed off from Denver Ctr to Springs Appch, who told me "you need a transponder to enter Class Charlie" and I said, uh, I have one, a new one.  Hmmm.  When I got on the ground, I did a system test and it passed.  A week later, I was about to depart and the NGT 9000 system test failed, giving me this transponder error message:  Ext. Fail (looked it up in the pilot guide, p. 2-12, says: "If a "Fail" or "External Fail" is shown for any of the system functions, then the message "Self-Test Failure" is shown . . . (yep, that message does appear). Page 5-4 of the pilots guide says: An "External Fail" message is caused by a problem with the external equipment input signals.  The unit continues to attempt to acquire the signal without rebooting. These message will automatically clear once communications has been restored to the external equipment."  What are the external equipment input signals?  The antenna?  Have you ever had an transponder antenna go bad?  I called L3 and spoke to someone (yesterday), who said they were going to call Russ Meyers.  I had a GTX327 for 10 years, never a problem, but it didn't have anywhere near the NGT 9000's capabilities or complexity. The jury is out on the L3 and whether this will be resolved quickly, and under warranty (it might not be a problem with the NGT 9000 at all).  I'll keep you posted. 

[jamesm]

I haven't seen that  before. Hopefully it is a cheap and easy fix

[byrdflyr]

The problem was me - I didn't have the Aspen PFD on, and that is the source of External Data required for the NGT 9000 to get baro pressure, which is required for the transponder to send the complete package of data to ATC.  So the lesson learned is that before doing a system test, turn on all of the interconnected and interdependent devices, let them spool up completely, and preferably, be outside in the clear so you can confirm all the GPS and other signals are being received and transmitted -- then, run systems tests.   The disappointing thing is that when I called L3 support, they didn't recognize the fail and make this simple diagnosis.  Should have gone like this:  Do you have a glass PFD (Aspen, Dynan, Garmin) as source of baro pressure?  If so, was that on when you ran the system test?  No, then go turn that on and try it again.  I spoke to L3 technical support and gave them this input.  

[LANCECASPER]

12 hours ago, byrdflyr said:

 The disappointing thing is that when I called L3 support, they didn't recognize the fail and make this simple diagnosis.  Should have gone like this:  Do you have a glass PFD (Aspen, Dynan, Garmin) as source of baro pressure?  If so, was that on when you ran the system test?  No, then go turn that on and try it again.  I spoke to L3 technical support and gave them this input.  

I think they gave you the benefit of the doubt and couldn’t have imagined anyone flying without their primary flight display turned on. Was your Aspen out of the airplane for the MAX upgrade?

[carusoam]

Great detailed follow-up Byrd!

The interconnections between boxes have increasing a ton since the early 90s...

Some connected boxes aren’t even in the panel...

POHs are going to need a logic map to follow... indicating sources of data, location of sensors, and where the data gets used...

Thanks for sharing the details.

Best regards,

-a-

[larrynimmo]

I too have both an Aspen & L3….when you look at your L3 it displays your pressure altitude on it....if there are - - - - where the altitude is usually listed, it means your not getting the baro input.