Flight crew of a dehavilland DH8 experienced problem with their transponder en route and was not unt...

Attributes
ACN	420788
Time
Date	199811
Day	Sat
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : ank airport : anc
State Reference	AK
Altitude	msl bound lower : 5000 msl bound upper : 5000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : anc
Operator	common carrier : air carrier
Make Model Name	Dash 8-100
Operating Under FAR Part	Part 121
Navigation In Use	Other
Flight Phase	cruise other descent : approach
Route In Use	enroute airway : v456
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 100 flight time total : 18000 flight time type : 4000
ASRS Report	420788
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : cfi pilot : atp
Experience	flight time last 90 days : 150 flight time total : 2700 flight time type : 300
ASRS Report	421410
Events
Anomaly	aircraft equipment problem : less severe other anomaly other
Independent Detector	other controllera
Resolutory Action	flight crew : overcame equipment problem other
Consequence	Other
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	other

Narrative:

Departed kenai on IFR clearance V456, 5000 ft to anc. Checked in with center, leveled off at 5000 ft MSL. 15 NM south of anc, realized we should have been handed off, so called approach on communication #2 while monitoring center on communication #1. (Center was talking constantly, couldn't get a word in edgewise.) approach controller said he had a primary target in my position. Checked transponder control head, noted it flashing 'standby' indicating that the transponder had lost power at some point (flashing) and was not transmitting (standby). Turned control knob slowly through 5 clicks and changed xponders as a precaution. Approach then vectored and sequenced us for ILS to runway 6R at anc without further problems. I suspect one of 2 things happened -- either the first officer moved through the 5 clicks too fast from 'standby' to 'TA/RA' (in which case the transponder initially indicates TA/RA, but after a time delay, goes back to its previous mode) on the before takeoff checklist at kenai, or the transponder lost power en route and went to standby, which would explain the flashing annunciation. I don't remember whether center ever positively had us idented, but we didn't hear from them as far as we know -- the leg is very short (43 NM) -- about not getting our transponder. This particular transponder head is peculiar about how fast you move the function switch -- other crews have had similar problems.

Original NASA ASRS Text

Title: FLC OF A DEHAVILLAND DH8 EXPERIENCED PROB WITH THEIR XPONDER ENRTE AND WAS NOT UNTIL APCH CTLR ADVISED THAT HE HAD A PRIMARY TARGET ONLY THAT THEY WERE AWARE OF THE PROB. THEY CYCLED THROUGH THE MODES AND IT THEN STARTED WORKING OK.

Narrative: DEPARTED KENAI ON IFR CLRNC V456, 5000 FT TO ANC. CHKED IN WITH CTR, LEVELED OFF AT 5000 FT MSL. 15 NM S OF ANC, REALIZED WE SHOULD HAVE BEEN HANDED OFF, SO CALLED APCH ON COM #2 WHILE MONITORING CTR ON COM #1. (CTR WAS TALKING CONSTANTLY, COULDN'T GET A WORD IN EDGEWISE.) APCH CTLR SAID HE HAD A PRIMARY TARGET IN MY POS. CHKED XPONDER CTL HEAD, NOTED IT FLASHING 'STANDBY' INDICATING THAT THE XPONDER HAD LOST PWR AT SOME POINT (FLASHING) AND WAS NOT XMITTING (STANDBY). TURNED CTL KNOB SLOWLY THROUGH 5 CLICKS AND CHANGED XPONDERS AS A PRECAUTION. APCH THEN VECTORED AND SEQUENCED US FOR ILS TO RWY 6R AT ANC WITHOUT FURTHER PROBS. I SUSPECT ONE OF 2 THINGS HAPPENED -- EITHER THE FO MOVED THROUGH THE 5 CLICKS TOO FAST FROM 'STANDBY' TO 'TA/RA' (IN WHICH CASE THE XPONDER INITIALLY INDICATES TA/RA, BUT AFTER A TIME DELAY, GOES BACK TO ITS PREVIOUS MODE) ON THE BEFORE TKOF CHKLIST AT KENAI, OR THE XPONDER LOST PWR ENRTE AND WENT TO STANDBY, WHICH WOULD EXPLAIN THE FLASHING ANNUNCIATION. I DON'T REMEMBER WHETHER CTR EVER POSITIVELY HAD US IDENTED, BUT WE DIDN'T HEAR FROM THEM AS FAR AS WE KNOW -- THE LEG IS VERY SHORT (43 NM) -- ABOUT NOT GETTING OUR XPONDER. THIS PARTICULAR XPONDER HEAD IS PECULIAR ABOUT HOW FAST YOU MOVE THE FUNCTION SWITCH -- OTHER CREWS HAVE HAD SIMILAR PROBS.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.

Flight crew of a dehavilland DH8 experienced problem with their transponder en route and was not until approach controller advised that he had a primary target only that they were aware of the problem. They cycled through the modes and it then started working ok.