TCASII RA resolution by a B737-400 in ZLA airspace caused by F18.

Attributes
ACN	436837
Time
Date	199905
Day	Sat
Local Time Of Day	1201 To 1800
Place
Locale Reference	navaid : ehf.vortac
State Reference	CA
Altitude	msl single value : 25000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zla.artcc
Operator	common carrier : air carrier
Make Model Name	B737-400
Operating Under FAR Part	Part 121
Navigation In Use	other
Flight Phase	cruise : level
Route In Use	enroute : direct
Flight Plan	IFR
Aircraft 2
Controlling Facilities	artcc : zla.artcc
Operator	other
Make Model Name	Hornet (F-18)
Operating Under FAR Part	Part 91
Navigation In Use	other
Flight Phase	cruise : level cruise : enroute altitude change
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 250 flight time total : 5900 flight time type : 450
ASRS Report	436837
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 : far non adherence : clearance non adherence : published procedure
Independent Detector	other flight crewa
Resolutory Action	flight crew : took precautionary avoidance action flight crew : took evasive action
Miss Distance	vertical : 1000
Supplementary
Problem Areas	Flight Crew Human Performance
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

While cruising at FL250 between lax and yvr, TCASII advisory for traffic approximately 2000 ft below and climbing rapidly. We then got an RA so I disconnected the autoplt and climbed about 600 ft (following TCASII RA) until we got the clear of conflict. It turns out that the aircraft which gave us the RA was a military F18 according to the center controller. The controller also told us that he did not observe any change in altitude from the F18 military aircraft. We were surprised to see the TCASII TA appear so rapidly and then an RA to follow. It appeared from our observations that the F18 was climbing extremely rapidly up towards us. I believe we did the correct thing in responding to the RA since we had not seen the intruding aircraft. We think that the military aircraft may have been using our flight as a practice intercept.

Original NASA ASRS Text

Title: TCASII RA RESOLUTION BY A B737-400 IN ZLA AIRSPACE CAUSED BY F18.

Narrative: WHILE CRUISING AT FL250 BTWN LAX AND YVR, TCASII ADVISORY FOR TFC APPROX 2000 FT BELOW AND CLBING RAPIDLY. WE THEN GOT AN RA SO I DISCONNECTED THE AUTOPLT AND CLBED ABOUT 600 FT (FOLLOWING TCASII RA) UNTIL WE GOT THE CLR OF CONFLICT. IT TURNS OUT THAT THE ACFT WHICH GAVE US THE RA WAS A MIL F18 ACCORDING TO THE CTR CTLR. THE CTLR ALSO TOLD US THAT HE DID NOT OBSERVE ANY CHANGE IN ALT FROM THE F18 MIL ACFT. WE WERE SURPRISED TO SEE THE TCASII TA APPEAR SO RAPIDLY AND THEN AN RA TO FOLLOW. IT APPEARED FROM OUR OBSERVATIONS THAT THE F18 WAS CLBING EXTREMELY RAPIDLY UP TOWARDS US. I BELIEVE WE DID THE CORRECT THING IN RESPONDING TO THE RA SINCE WE HAD NOT SEEN THE INTRUDING ACFT. WE THINK THAT THE MIL ACFT MAY HAVE BEEN USING OUR FLT AS A PRACTICE INTERCEPT.

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.