Controller supervisor report reference clearance confusion. Altitude deviation and TCASII RA.

Attributes
ACN	291847
Time
Date	199412
Day	Sun
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : iiu
State Reference	KY
Altitude	msl bound lower : 25300 msl bound upper : 25600
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zid
Operator	common carrier : air carrier
Make Model Name	DC-9 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	climbout : intermediate altitude
Route In Use	enroute : direct
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	B737 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	descent other
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	oversight : supervisor
Qualification	controller : radar
Experience	controller radar : 3 controller supervisory : 5
ASRS Report	291847
Person 2
Affiliation	government : faa
Function	controller : departure
Qualification	controller : radar
Events
Anomaly	altitude deviation : overshoot conflict : airborne less severe non adherence : clearance non adherence : required legal separation other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : unspecified
Resolutory Action	flight crew : took evasive action
Consequence	faa : reviewed incident with flight crew
Miss Distance	horizontal : 18000 vertical : 700
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error Pilot Deviation

Narrative:

An operational error occurred due to misunderstood clearance by a pilot, and a missed readback by the controller. Aircraft was issued a climb to FL250. The pilot acknowledged. The controller issued a turn 'fly heading 270, direct pxv when able, rest of route unchanged.' the pilot readback 'climb to 270, direct pxv.' the aircraft then continued through FL250, TCASII initiated an RA. Aircraft 1 descended back to FL250. Aircraft 2 climbed to FL265. Aedp activated approximately 2 seconds prior to aci reporting level. Although the controller did not hear the readback 'climb' by the pilot, the pilot did not understand or follow the controller's clearance. If the pilot of aircraft 1 had used the 'flight level' in his readback, this would have triggered the controller's ear to the misunderstanding.

Original NASA ASRS Text

Title: CTLR SUPVR RPT REF CLRNC CONFUSION. ALTDEV AND TCASII RA.

Narrative: AN OPERROR OCCURRED DUE TO MISUNDERSTOOD CLRNC BY A PLT, AND A MISSED READBACK BY THE CTLR. ACFT WAS ISSUED A CLB TO FL250. THE PLT ACKNOWLEDGED. THE CTLR ISSUED A TURN 'FLY HDG 270, DIRECT PXV WHEN ABLE, REST OF RTE UNCHANGED.' THE PLT READBACK 'CLB TO 270, DIRECT PXV.' THE ACFT THEN CONTINUED THROUGH FL250, TCASII INITIATED AN RA. ACFT 1 DSNDED BACK TO FL250. ACFT 2 CLBED TO FL265. AEDP ACTIVATED APPROX 2 SECONDS PRIOR TO ACI RPTING LEVEL. ALTHOUGH THE CTLR DID NOT HEAR THE READBACK 'CLB' BY THE PLT, THE PLT DID NOT UNDERSTAND OR FOLLOW THE CTLR'S CLRNC. IF THE PLT OF ACFT 1 HAD USED THE 'FLT LEVEL' IN HIS READBACK, THIS WOULD HAVE TRIGGERED THE CTLR'S EAR TO THE MISUNDERSTANDING.

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.