Altitude deviation altitude excursion due to a TCASII RA on unknown VFR traffic in area.

Attributes
ACN	269506
Time
Date	199404
Day	Thu
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : tfd airport : phk
State Reference	AZ
Altitude	msl bound lower : 17000 msl bound upper : 18000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tower : dca
Operator	common carrier : air carrier
Make Model Name	B737-300
Operating Under FAR Part	Part 121
Flight Phase	cruise other cruise other
Route In Use	enroute airway : zab
Flight Plan	IFR
Aircraft 2
Operator	general aviation : corporate
Make Model Name	Twin Otter DHC-6
Operating Under FAR Part	other : unknown
Flight Phase	cruise other
Flight Plan	VFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 230 flight time total : 10500 flight time type : 1500
ASRS Report	269506
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	altitude deviation : excursion from assigned altitude conflict : airborne less severe inflight encounter other non adherence : clearance other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : unspecified
Resolutory Action	flight crew : took evasive action
Consequence	faa : reviewed incident with flight crew
Miss Distance	horizontal : 3000 vertical : 400
Supplementary
Air Traffic Incident	Pilot Deviation

Narrative:

During a phx-tus flight we were in level cruise at 17000 when we had a TCASII advisory of traffic at 10-11 O'clock and 400 below. The captain initiated an immediate climb and I advised ATC immediately that we were in a climb for conflicting traffic. The frequency was busy and it was necessary to call at least twice to ensure that we were acknowledged. We climbed approximately 1000 ft in a left turn to keep the traffic in sight, which was a twin otter parachute jump aircraft. We gradually returned to our assigned altitude, departure said they saw the traffic on radar at 500 below our assigned altitude. We later were requested to correct our heading as the turn we had used to keep the aircraft in sight had diverted us off course. I assume the jump plane had been working that area for some time that day as this is an active jump zone, but at our cruise speed, 500 ft is not enough separation to be safe, and the TCASII performed and demanded an immediate climb as it is supposed to. We should have been warned about the traffic and/or the jump aircraft kept to a lower altitude.

Original NASA ASRS Text

Title: ALTDEV ALT EXCURSION DUE TO A TCASII RA ON UNKNOWN VFR TFC IN AREA.

Narrative: DURING A PHX-TUS FLT WE WERE IN LEVEL CRUISE AT 17000 WHEN WE HAD A TCASII ADVISORY OF TFC AT 10-11 O'CLOCK AND 400 BELOW. THE CAPT INITIATED AN IMMEDIATE CLB AND I ADVISED ATC IMMEDIATELY THAT WE WERE IN A CLB FOR CONFLICTING TFC. THE FREQ WAS BUSY AND IT WAS NECESSARY TO CALL AT LEAST TWICE TO ENSURE THAT WE WERE ACKNOWLEDGED. WE CLIMBED APPROX 1000 FT IN A L TURN TO KEEP THE TFC IN SIGHT, WHICH WAS A TWIN OTTER PARACHUTE JUMP ACFT. WE GRADUALLY RETURNED TO OUR ASSIGNED ALT, DEP SAID THEY SAW THE TFC ON RADAR AT 500 BELOW OUR ASSIGNED ALT. WE LATER WERE REQUESTED TO CORRECT OUR HDG AS THE TURN WE HAD USED TO KEEP THE ACFT IN SIGHT HAD DIVERTED US OFF COURSE. I ASSUME THE JUMP PLANE HAD BEEN WORKING THAT AREA FOR SOME TIME THAT DAY AS THIS IS AN ACTIVE JUMP ZONE, BUT AT OUR CRUISE SPD, 500 FT IS NOT ENOUGH SEPARATION TO BE SAFE, AND THE TCASII PERFORMED AND DEMANDED AN IMMEDIATE CLB AS IT IS SUPPOSED TO. WE SHOULD HAVE BEEN WARNED ABOUT THE TFC AND/OR THE JUMP ACFT KEPT TO A LOWER ALT.

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.