LR60 flight crew under control of A90 at 5700 ft, experienced TCASII RA with unknown aircraft.

Attributes
ACN	618340
Time
Date	200405
Day	Thu
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : mht.airport
State Reference	NH
Altitude	msl single value : 5700
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : a90.tracon
Operator	general aviation : corporate
Make Model Name	Learjet 60
Operating Under FAR Part	Part 91
Flight Phase	cruise : level
Flight Plan	None
Aircraft 2
Operator	general aviation : personal
Make Model Name	Cessna Single Piston Undifferentiated or Other Model
Person 1
Affiliation	company : corporate
Function	flight crew : captain oversight : pic
Qualification	pilot : atp pilot : multi engine
Experience	flight time last 90 days : 100 flight time total : 12700 flight time type : 1200
ASRS Report	618340
Person 2
Affiliation	company : corporate
Function	flight crew : first officer
Events
Anomaly	conflict : airborne critical
Independent Detector	aircraft equipment : tcas other controllera other flight crewa other flight crewb
Resolutory Action	controller : issued alert flight crew : took evasive action
Miss Distance	horizontal : 3000 vertical : 100
Supplementary
Problem Areas	Flight Crew Human Performance
Primary Problem	Flight Crew Human Performance

Narrative:

While maneuvering, my flight had a pop-up RA on a cessna 100 ft below. The PF followed the RA and I obtained a visual on the other aircraft coming out beneath our 10:30 O'clock position. TCASII and radar advisories were being used to assist visual scanning. This target was not displayed on either my TCASII or TRACON's radar until the RA. Bos approach promptly issued a TA at the same time as our initial RA (excellent controling). The other aircraft was obscured behind my nose during a turning maneuver and did not become visible until the rollout climb.

Original NASA ASRS Text

Title: LR60 FLT CREW UNDER CTL OF A90 AT 5700 FT, EXPERIENCED TCASII RA WITH UNKNOWN ACFT.

Narrative: WHILE MANEUVERING, MY FLT HAD A POP-UP RA ON A CESSNA 100 FT BELOW. THE PF FOLLOWED THE RA AND I OBTAINED A VISUAL ON THE OTHER ACFT COMING OUT BENEATH OUR 10:30 O'CLOCK POS. TCASII AND RADAR ADVISORIES WERE BEING USED TO ASSIST VISUAL SCANNING. THIS TARGET WAS NOT DISPLAYED ON EITHER MY TCASII OR TRACON'S RADAR UNTIL THE RA. BOS APCH PROMPTLY ISSUED A TA AT THE SAME TIME AS OUR INITIAL RA (EXCELLENT CTLING). THE OTHER ACFT WAS OBSCURED BEHIND MY NOSE DURING A TURNING MANEUVER AND DID NOT BECOME VISIBLE UNTIL THE ROLLOUT CLB.

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.