Air carrier large transport altitude deviation on approach into bos in response to TCASII RA.

Attributes
ACN	190500
Time
Date	199109
Day	Mon
Local Time Of Day	1801 To 2400
Place
Locale Reference	airport : bos
State Reference	MA
Altitude	msl bound lower : 2400 msl bound upper : 2900
Environment
Flight Conditions	VMC
Light	Dusk
Aircraft 1
Controlling Facilities	tower : bos
Operator	common carrier : air carrier
Make Model Name	Large Transport, Low Wing, 3 Turbojet Eng
Flight Phase	descent : approach descent other landing other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : instrument pilot : commercial pilot : atp
Experience	flight time last 90 days : 193 flight time total : 19723
ASRS Report	190500
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument pilot : atp
Events
Anomaly	altitude deviation : excursion from assigned altitude conflict : airborne less severe non adherence : clearance
Independent Detector	aircraft equipment other aircraft equipment : unspecified
Resolutory Action	flight crew : returned to intended course or assigned course
Consequence	Other
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	Pilot Deviation

Narrative:

The pilot flying this aircraft responded to a TCASII 'climb, climb' RA. The aircraft climbed 500 ft above the glide path before the RA announced 'clear of traffic'. Boston logan tower was notified of the deviation. The aircraft was able to return to the glide path for a normal landing. A commuter aircraft was on an approach to runway 4L, 3 1/2 mi ahead of this aircraft. It was idented on the radar screen and was not responsible for the RA. Logan tower advised this crew that no aircraft were in their vicinity at the time of the RA and the crew saw no other traffic. It was speculated that perhaps the TCASII system was responding to ship traffic in boston harbor.

Original NASA ASRS Text

Title: ACR LGT ALT DEV ON APCH INTO BOS IN RESPONSE TO TCASII RA.

Narrative: THE PLT FLYING THIS ACFT RESPONDED TO A TCASII 'CLB, CLB' RA. THE ACFT CLBED 500 FT ABOVE THE GLIDE PATH BEFORE THE RA ANNOUNCED 'CLR OF TFC'. BOSTON LOGAN TWR WAS NOTIFIED OF THE DEV. THE ACFT WAS ABLE TO RETURN TO THE GLIDE PATH FOR A NORMAL LNDG. A COMMUTER ACFT WAS ON AN APCH TO RWY 4L, 3 1/2 MI AHEAD OF THIS ACFT. IT WAS IDENTED ON THE RADAR SCREEN AND WAS NOT RESPONSIBLE FOR THE RA. LOGAN TWR ADVISED THIS CREW THAT NO ACFT WERE IN THEIR VICINITY AT THE TIME OF THE RA AND THE CREW SAW NO OTHER TFC. IT WAS SPECULATED THAT PERHAPS THE TCASII SYS WAS RESPONDING TO SHIP TFC IN BOSTON HARBOR.

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.