CL604 first officer reported an airborne conflict resulted when he overshot the cleared altitude in ...

Attributes
ACN	1365774
Time
Date	201606
Local Time Of Day	0601-1200
Place
Locale Reference	ZLA.ARTCC
State Reference	CA
Environment
Light	Daylight
Aircraft 1
Make Model Name	Challenger CL604
Operating Under FAR Part	Part 91
Flight Phase	Descent
Route In Use	Vectors
Flight Plan	IFR
Person 1
Function	First Officer Pilot Flying
Qualification	Flight Crew Multiengine Flight Crew Instrument Flight Crew Flight Instructor Flight Crew Air Transport Pilot (ATP)
Experience	Flight Crew Last 90 Days 125 Flight Crew Total 9500 Flight Crew Type 320
Events
Anomaly	Conflict Airborne Conflict Deviation - Altitude Overshoot Deviation - Procedural Clearance

Narrative:

After finishing our maintenance checks; we were returning to home base. Descending from FL300 to FL250 ATC assigned a left (200 degrees - long way) turn direct to pmd; and asked for 'a tight turn if able'. Having only crew onboard; I elected to disconnect the auto pilot and perform a steep turn. I also reduced power/speed to minimize the radius of the turn. As I approached FL250; I didn't completely arrest the descent; and descended below assigned altitude. Also; while in the turn ATC advised of traffic climbing to FL240 (gulfstream) perhaps 9 o'clock out of the turn. I saw and reported the traffic; but was later informed that I didn't quite maintain 5 miles (4.7) and 1;000 (700) vertical feet.in retrospect; I had no need to perform a steep turn; or disengage the auto pilot in a airspace. Even if I had elected to do so; a more timely response would have been to terminate the steep turn; to make the altitude capture easier.

Original NASA ASRS Text

Title: CL604 First Officer reported an airborne conflict resulted when he overshot the cleared altitude in descent.

Narrative: After finishing our maintenance checks; we were returning to home base. Descending from FL300 to FL250 ATC assigned a left (200 degrees - long way) turn direct to PMD; and asked for 'a tight turn if able'. Having only crew onboard; I elected to disconnect the auto pilot and perform a steep turn. I also reduced power/speed to minimize the radius of the turn. As I approached FL250; I didn't completely arrest the descent; and descended below assigned altitude. Also; while in the turn ATC advised of traffic climbing to FL240 (Gulfstream) perhaps 9 o'clock out of the turn. I saw and reported the traffic; but was later informed that I didn't quite maintain 5 miles (4.7) and 1;000 (700) vertical feet.In retrospect; I had no need to perform a steep turn; or disengage the auto pilot in A airspace. Even if I had elected to do so; a more timely response would have been to terminate the steep turn; to make the altitude capture easier.

Data retrieved from NASA's ASRS site 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.

CL604 first officer reported an airborne conflict resulted when he overshot the cleared altitude in descent.