MD88 vacates assigned altitude during TCASII RA resolution N90.

Attributes
ACN	439130
Time
Date	199906
Day	Sun
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : lga.airport
State Reference	NY
Altitude	msl bound lower : 3000 msl bound upper : 3300
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : n90.tracon
Operator	common carrier : air carrier
Make Model Name	MD-88
Operating Under FAR Part	Part 121
Navigation In Use	other
Flight Phase	descent : intermediate altitude
Route In Use	arrival : on vectors
Flight Plan	IFR
Aircraft 2
Controlling Facilities	tracon : n90.tracon
Make Model Name	Small Transport, Low Wing, 2 Recip Eng
Flight Phase	descent : vacating altitude
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp pilot : cfi
Experience	flight time last 90 days : 275 flight time total : 4000 flight time type : 420
ASRS Report	439130
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	altitude deviation : excursion from assigned altitude conflict : airborne less severe other anomaly other
Independent Detector	aircraft equipment : tcas other flight crewa other flight crewb
Resolutory Action	flight crew : took precautionary avoidance action
Miss Distance	horizontal : 0 vertical : 500
Supplementary
Problem Areas	Environmental Factor ATC Human Performance
Primary Problem	Ambiguous

Narrative:

During vectors for visual approach to lga, eastbound, 3000 ft, TCASII RA indicated climb for a target at 2 mi, -200 ft. Target was not previously on scope (pop-up). PF (captain) disconnected autoplt/throttles, advanced throttles and climbed to 3300 ft. At 3300 ft TCASII annunciated 'clear of conflict.' PF leveled at 3300 ft. PNF saw a light colored light twin on right side of aircraft, 500 ft low and wbound. TCASII advisory was reported to approach, as was the other aircraft. No TA was issued by approach. PF called approach control after landing, they did not have target aircraft on radar.

Original NASA ASRS Text

Title: MD88 VACATES ASSIGNED ALT DURING TCASII RA RESOLUTION N90.

Narrative: DURING VECTORS FOR VISUAL APCH TO LGA, EBOUND, 3000 FT, TCASII RA INDICATED CLB FOR A TARGET AT 2 MI, -200 FT. TARGET WAS NOT PREVIOUSLY ON SCOPE (POP-UP). PF (CAPT) DISCONNECTED AUTOPLT/THROTTLES, ADVANCED THROTTLES AND CLBED TO 3300 FT. AT 3300 FT TCASII ANNUNCIATED 'CLR OF CONFLICT.' PF LEVELED AT 3300 FT. PNF SAW A LIGHT COLORED LIGHT TWIN ON R SIDE OF ACFT, 500 FT LOW AND WBOUND. TCASII ADVISORY WAS RPTED TO APCH, AS WAS THE OTHER ACFT. NO TA WAS ISSUED BY APCH. PF CALLED APCH CTL AFTER LNDG, THEY DID NOT HAVE TARGET ACFT ON RADAR.

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.