IFR PA28 arrow with ilm TRACON climbs above assigned altitude because of tcad alert.

Attributes
ACN	616083
Time
Date	200404
Day	Thu
Local Time Of Day	0601 To 1200
Place
Locale Reference	navaid : ilm.vortac
State Reference	NC
Altitude	msl bound lower : 5000 msl bound upper : 3500
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : ilm.tracon
Operator	general aviation : instructional
Make Model Name	PA-28 Cherokee Arrow IV
Operating Under FAR Part	Part 91
Navigation In Use	other vortac
Flight Phase	cruise : level
Flight Plan	IFR
Aircraft 2
Controlling Facilities	tracon : ilm.tracon
Operator	general aviation : personal
Make Model Name	Skyhawk 172/Cutlass 172
Operating Under FAR Part	Part 91
Flight Phase	cruise : level
Person 1
Affiliation	other
Function	instruction : instructor
Qualification	pilot : cfi pilot : commercial pilot : instrument pilot : multi engine pilot : atp
Experience	flight time last 90 days : 100 flight time total : 1750 flight time type : 450
ASRS Report	616083
Person 2
Affiliation	other
Function	instruction : trainee
Qualification	pilot : student
Events
Anomaly	altitude deviation : excursion from assigned altitude conflict : airborne less severe non adherence : clearance
Independent Detector	other flight crewa
Resolutory Action	controller : issued new clearance flight crew : took evasive action
Consequence	faa : reviewed incident with flight crew
Miss Distance	horizontal : 6000 vertical : 500
Supplementary
Problem Areas	Flight Crew Human Performance ATC Human Performance
Primary Problem	Ambiguous

Narrative:

On apr/thu/04, while on IFR flight plan in VFR conditions, our tcad went off and shortly afterward I was informed by the controller of traffic at 1 O'clock position. The wilmington, nc, approach controller informed me that they were not talking with the aircraft. It appeared that we were almost level with the C172 as we continued to close in. I informed the controller that I was going to climb from 3000 ft to 3500 ft for traffic separation. The controller informed me that I could not climb without controller's authority/authorized. I immediately informed the controller that I was climbing for traffic separation. The controller was initially short (disturbed that I told him that I was climbing), but then came back with clearance to 3500 ft. Based upon VFR conditions and proximity to the other traffic, I felt I took the appropriate actions to avoid a possible midair collision.

Original NASA ASRS Text

Title: IFR PA28 ARROW WITH ILM TRACON CLBS ABOVE ASSIGNED ALT BECAUSE OF TCAD ALERT.

Narrative: ON APR/THU/04, WHILE ON IFR FLT PLAN IN VFR CONDITIONS, OUR TCAD WENT OFF AND SHORTLY AFTERWARD I WAS INFORMED BY THE CTLR OF TFC AT 1 O'CLOCK POS. THE WILMINGTON, NC, APCH CTLR INFORMED ME THAT THEY WERE NOT TALKING WITH THE ACFT. IT APPEARED THAT WE WERE ALMOST LEVEL WITH THE C172 AS WE CONTINUED TO CLOSE IN. I INFORMED THE CTLR THAT I WAS GOING TO CLB FROM 3000 FT TO 3500 FT FOR TFC SEPARATION. THE CTLR INFORMED ME THAT I COULD NOT CLB WITHOUT CTLR'S AUTH. I IMMEDIATELY INFORMED THE CTLR THAT I WAS CLBING FOR TFC SEPARATION. THE CTLR WAS INITIALLY SHORT (DISTURBED THAT I TOLD HIM THAT I WAS CLBING), BUT THEN CAME BACK WITH CLRNC TO 3500 FT. BASED UPON VFR CONDITIONS AND PROX TO THE OTHER TFC, I FELT I TOOK THE APPROPRIATE ACTIONS TO AVOID A POSSIBLE MIDAIR COLLISION.

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.