H25 inbound to esn descends below assigned altitude to remain VFR and avoid aerobatic aircraft.

Attributes
ACN	585504
Time
Date	200306
Day	Sun
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : esn.airport
State Reference	MD
Altitude	msl single value : 3000
Environment
Flight Conditions	Marginal
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : pct.tracon
Operator	common carrier : air taxi
Operating Under FAR Part	Part 91
Flight Phase	descent : approach descent : intermediate altitude
Route In Use	arrival : on vectors
Flight Plan	IFR
Aircraft 2
Controlling Facilities	tracon : pct.tracon
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Flight Phase	climbout : intermediate altitude climbout : vacating altitude
Person 1
Affiliation	company : air taxi
Function	flight crew : captain oversight : pic
Qualification	pilot : atp pilot : commercial pilot : multi engine pilot : instrument
Experience	flight time last 90 days : 100 flight time total : 7500 flight time type : 110
ASRS Report	585504
Person 2
Affiliation	company : air taxi
Function	flight crew : first officer
Qualification	pilot : multi engine pilot : cfi pilot : atp
Experience	flight time last 90 days : 100 flight time total : 3700 flight time type : 190
ASRS Report	585506
Events
Anomaly	altitude deviation : excursion from assigned altitude conflict : airborne less severe non adherence : clearance
Independent Detector	other flight crewa other flight crewb
Resolutory Action	flight crew : returned to assigned altitude
Consequence	faa : reviewed incident with flight crew
Miss Distance	horizontal : 2000 vertical : 500
Supplementary
Problem Areas	Flight Crew Human Performance
Primary Problem	Flight Crew Human Performance

Narrative:

During a descent into kesn, potomac approach controller cleared us to 3000 ft with an expedite through 4000 ft. At about 3500 ft the first officer and I observed an aerobatic aircraft, performing a hammer head, pop up through a hole in the clouds. Potomac advised us of the traffic. But as he was in an aggressive maneuver, his altitude was changing rapidly. We received 2 TA's and an RA. As the aircraft was exiting the hammer head, he turned towards us. As the first officer saw the traffic to the right of our aircraft, the first officer was maintaining a visual on the traffic and descended about 400 ft below our assigned altitude to remain VFR to avoid the traffic. IFR was cancelled and a visual approach was made to kesn.

Original NASA ASRS Text

Title: H25 INBOUND TO ESN DSNDS BELOW ASSIGNED ALT TO REMAIN VFR AND AVOID AEROBATIC ACFT.

Narrative: DURING A DSCNT INTO KESN, POTOMAC APCH CTLR CLRED US TO 3000 FT WITH AN EXPEDITE THROUGH 4000 FT. AT ABOUT 3500 FT THE FO AND I OBSERVED AN AEROBATIC ACFT, PERFORMING A HAMMER HEAD, POP UP THROUGH A HOLE IN THE CLOUDS. POTOMAC ADVISED US OF THE TFC. BUT AS HE WAS IN AN AGGRESSIVE MANEUVER, HIS ALT WAS CHANGING RAPIDLY. WE RECEIVED 2 TA'S AND AN RA. AS THE ACFT WAS EXITING THE HAMMER HEAD, HE TURNED TOWARDS US. AS THE FO SAW THE TFC TO THE R OF OUR ACFT, THE FO WAS MAINTAINING A VISUAL ON THE TFC AND DSNDED ABOUT 400 FT BELOW OUR ASSIGNED ALT TO REMAIN VFR TO AVOID THE TFC. IFR WAS CANCELLED AND A VISUAL APCH WAS MADE TO KESN.

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.