Narrative:

Our flight number was air carrier cg. Heavy departing jfk for lax. Air carrier east heavy, another large transport was the next flight behind us going to sfo. Runway 4R in use as takeoff runway. Initial heading 100 degrees, jfk departure turned us to 270 degrees with a climb to 11000'. Flight east behind us was informed by jfk departure that his transponder was inoperative. He cycled his transponder, no change. Then jkd departure informed us that our transponder was also inoperative. We also cycled between the two transponders and no change. At this point jfk departure called traffic at 3 O'clock at 10500' crossing under us also swbnd. His heading was probably 200 degrees plus or minus. We had no visibility contact since we were still in our turn to 240 degrees and the traffic was right rear of our field of vision. When we spotted the traffic we were at 10200' climbing. The traffic was closer than I expected due to delayed calls from jfk departure due to transmissions being covered. I told my copilot to increase his rate of climb immediately and level at 11000'. Due to the increased rate of climb he overshot by 200'-300'. At this time the traffic passed under us on a perfect collision heading. Also at this time jfk departure called and ask if we were maintaining 11000'. We replied in the affirmative. I questioned him about the possibility that his equipment was inoperative. No reply. He switched us over to ZNY. I asked ZNY if our transponder was working ok and the answer was yes. It appears that jfk departure had an equipment failure and did not realize it. I requested that ZNY pass on the information to him that our transponder was ok.

Related reports:

Google
 

Original NASA ASRS Text

Title: ACR LGT ALT DEVIATION OVERSHOT. CREW DISTR BY REPORTED MODE 'C' INOP.

Narrative: OUR FLT NUMBER WAS ACR CG. HEAVY DEPARTING JFK FOR LAX. ACR E HEAVY, ANOTHER LGT WAS THE NEXT FLT BEHIND US GOING TO SFO. RWY 4R IN USE AS TKOF RWY. INITIAL HDG 100 DEGS, JFK DEP TURNED US TO 270 DEGS WITH A CLB TO 11000'. FLT E BEHIND US WAS INFORMED BY JFK DEP THAT HIS TRANSPONDER WAS INOP. HE CYCLED HIS TRANSPONDER, NO CHANGE. THEN JKD DEP INFORMED US THAT OUR TRANSPONDER WAS ALSO INOP. WE ALSO CYCLED BTWN THE TWO TRANSPONDERS AND NO CHANGE. AT THIS POINT JFK DEP CALLED TFC AT 3 O'CLOCK AT 10500' XING UNDER US ALSO SWBND. HIS HDG WAS PROBABLY 200 DEGS PLUS OR MINUS. WE HAD NO VIS CONTACT SINCE WE WERE STILL IN OUR TURN TO 240 DEGS AND THE TFC WAS R REAR OF OUR FIELD OF VISION. WHEN WE SPOTTED THE TFC WE WERE AT 10200' CLBING. THE TFC WAS CLOSER THAN I EXPECTED DUE TO DELAYED CALLS FROM JFK DEP DUE TO TRANSMISSIONS BEING COVERED. I TOLD MY COPLT TO INCREASE HIS RATE OF CLB IMMEDIATELY AND LEVEL AT 11000'. DUE TO THE INCREASED RATE OF CLB HE OVERSHOT BY 200'-300'. AT THIS TIME THE TFC PASSED UNDER US ON A PERFECT COLLISION HDG. ALSO AT THIS TIME JFK DEP CALLED AND ASK IF WE WERE MAINTAINING 11000'. WE REPLIED IN THE AFFIRMATIVE. I QUESTIONED HIM ABOUT THE POSSIBILITY THAT HIS EQUIP WAS INOP. NO REPLY. HE SWITCHED US OVER TO ZNY. I ASKED ZNY IF OUR TRANSPONDER WAS WORKING OK AND THE ANSWER WAS YES. IT APPEARS THAT JFK DEP HAD AN EQUIP FAILURE AND DID NOT REALIZE IT. I REQUESTED THAT ZNY PASS ON THE INFO TO HIM THAT OUR TRANSPONDER WAS OK.

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.