A corporate jet captain reported an near midair collision with an L-39 shortly after takeoff from ne...

Narrative:

Our aircraft was cleared by ATC to takeoff and assigned to maintain runway heading and 2;000 ft. Immediately after takeoff; while level at 2;000 ft; within three miles of the airport; ATC instructed an 'experimental' L-39 jet aircraft to maintain 3;000 ft and proceed to the airport. At that time; our crew had visual contact with the L-39 aircraft at our 12 o'clock and above position. Immediately thereafter; our aircraft TCAS reported the L-39 was descending from 800 ft above our assigned altitude of 2;000 ft. As the L-39 flew directly overhead our position; our TCAS issued a RA that the aircraft was descending from +800 ft through +400 ft. There was insufficient time to accomplish an evasive maneuver before the L-39 aircraft passed directly overhead and behind our position and the RA was dismissed by our TCAS. I advised ATC of the L-39's close proximity and mentioned that it was too close! I also advised ATC that our TCAS reported a RA but we were unable to react quickly enough before the alert passed and the situation was again safe. ATC reported for a second time that the L-39 was assigned to maintain 3;000 ft. When questioned by ATC; I heard the L-39 pilot advise the controller that he had descended to remain clear of the cloud base along the L-39's ATC assigned routing. The remainder of the flight was uneventful.

Original NASA ASRS Text

Title: A corporate jet Captain reported an NMAC with an L-39 shortly after takeoff from NEW when the L-39 descended below his cleared altitude to avoid a cloud base.

Narrative: Our aircraft was cleared by ATC to takeoff and assigned to maintain runway heading and 2;000 FT. Immediately after takeoff; while level at 2;000 FT; within three miles of the airport; ATC instructed an 'experimental' L-39 jet aircraft to maintain 3;000 FT and proceed to the airport. At that time; our crew had visual contact with the L-39 aircraft at our 12 o'clock and above position. Immediately thereafter; our aircraft TCAS reported the L-39 was descending from 800 FT above our assigned altitude of 2;000 FT. As the L-39 flew directly overhead our position; our TCAS issued a RA that the aircraft was descending from +800 FT through +400 FT. There was insufficient time to accomplish an evasive maneuver before the L-39 aircraft passed directly overhead and behind our position and the RA was dismissed by our TCAS. I advised ATC of the L-39's close proximity and mentioned that it was too close! I also advised ATC that our TCAS reported a RA but we were unable to react quickly enough before the alert passed and the situation was again safe. ATC reported for a second time that the L-39 was assigned to maintain 3;000 FT. When questioned by ATC; I heard the L-39 pilot advise the Controller that he had descended to remain clear of the cloud base along the L-39's ATC assigned routing. The remainder of the flight was uneventful.

Data retrieved from NASA's ASRS site as of April 2012 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.

Attributes
ACN	942954
Time
Date	201104
Local Time Of Day	1801-2400
Place
Locale Reference	NEW.Airport
State Reference	LA
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	Medium Large Transport Low Wing 2 Turbojet Eng
Operating Under FAR Part	Part 135
Flight Phase	Climb
Flight Plan	IFR
Aircraft 2
Make Model Name	Albatros (L39)
Operating Under FAR Part	Part 91
Flight Phase	Descent
Route In Use	Direct
Person 1
Function	Check Pilot Pilot Flying Captain
Qualification	Flight Crew Multiengine Flight Crew Flight Instructor Flight Crew Air Transport Pilot (ATP)
Experience	Flight Crew Last 90 Days 120 Flight Crew Total 16850 Flight Crew Type 1300
Events
Anomaly	Conflict NMAC
Miss Distance	Horizontal 0 Vertical 400

A corporate jet captain reported an near midair collision with an L-39 shortly after takeoff from new when the L-39 descended below his cleared altitude to avoid a cloud base.