Altitude deviation altitude excursion after receiving TCASII RA.

Attributes
ACN	247746
Time
Date	199307
Day	Sat
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : obk
State Reference	IL
Altitude	msl bound lower : 10000 msl bound upper : 10350
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tower : cle
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Navigation In Use	Other Other
Flight Phase	cruise other
Route In Use	arrival other arrival star : star enroute airway : ord
Flight Plan	IFR
Aircraft 2
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Flight Phase	climbout : intermediate altitude
Route In Use	enroute : direct
Flight Plan	VFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : flight engineer pilot : cfi pilot : atp
Experience	flight time last 90 days : 175 flight time total : 14500 flight time type : 2025
ASRS Report	247746
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Events
Anomaly	altitude deviation : excursion from assigned altitude conflict : airborne less severe non adherence : clearance other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : unspecified
Resolutory Action	flight crew : returned to intended course or assigned course flight crew : took evasive action
Consequence	Other
Miss Distance	horizontal : 3000 vertical : 600
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

At 10000 ft MSL and 250 KTS, 3 NM west of pivot intersection on v- 84 to pappi intersection (PMM2 arrival to ord) we had a TCASII RA 'climb, climb, climb.' a climb was immediately initiated as TCASII VFR traffic was noted on TCASII at 9500 ft MSL and climbing slowly on a southeast heading. The VFR traffic was at 9800 ft MLS and we were at 10350 ft MSL when we received a 'monitor vertical speed' from TCASII and clear of conflict annunciation as traffic passed underneath us but never in visual contact. We descended smoothly back to 10000 ft MSL and then to 8000 ft MSL as directed by ord approach control for a normal landing at ord. Even though the VFR traffic was legal to be 9500 ft MSL sebound in that area, was he/she wise to be transiting a main terminal arrival route with highspd jet traffic at 10000 ft MSL down to 7000 ft MSL? Perhaps an FAA advisory safety letter should be published reference this problem.

Original NASA ASRS Text

Title: ALTDEV ALT EXCURSION AFTER RECEIVING TCASII RA.

Narrative: AT 10000 FT MSL AND 250 KTS, 3 NM W OF PIVOT INTXN ON V- 84 TO PAPPI INTXN (PMM2 ARR TO ORD) WE HAD A TCASII RA 'CLB, CLB, CLB.' A CLB WAS IMMEDIATELY INITIATED AS TCASII VFR TFC WAS NOTED ON TCASII AT 9500 FT MSL AND CLBING SLOWLY ON A SE HDG. THE VFR TFC WAS AT 9800 FT MLS AND WE WERE AT 10350 FT MSL WHEN WE RECEIVED A 'MONITOR VERT SPD' FROM TCASII AND CLR OF CONFLICT ANNUNCIATION AS TFC PASSED UNDERNEATH US BUT NEVER IN VISUAL CONTACT. WE DSNDED SMOOTHLY BACK TO 10000 FT MSL AND THEN TO 8000 FT MSL AS DIRECTED BY ORD APCH CTL FOR A NORMAL LNDG AT ORD. EVEN THOUGH THE VFR TFC WAS LEGAL TO BE 9500 FT MSL SEBOUND IN THAT AREA, WAS HE/SHE WISE TO BE TRANSITING A MAIN TERMINAL ARR RTE WITH HIGHSPD JET TFC AT 10000 FT MSL DOWN TO 7000 FT MSL? PERHAPS AN FAA ADVISORY SAFETY LETTER SHOULD BE PUBLISHED REF THIS PROB.

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.