ZLA controller described a TCAS RA event when a VFR military flight at 16;500 initiated a TCAS respo...

Narrative:

I was working a kc-135 out of a MOA. The kc-135 was level at 17;000 ft. I was also working a flight of 3 av-8s; en route to the MOA the kc-135 just departed. Wake was level at 16;500 VFR with the blh altimeter. The kc-135 was level at 17;000 with the eed altimeter. The difference of altimeter was .01 at the time. Traffic was issued to each aircraft at 6 miles and a wake turbulence advisory was give to the flight of 3 av-8s. The flight of 3 av-8s reported the kc-135 in sight. As the kc-135 approached the av-8s; about 12 o'clock and 1 mile; he said he was responding to a RA. I rogered him; as I had no other traffic in his vicinity. He then said the traffic looked more like 300 ft below. After the traffic passed; I shipped the kc-135 to yuma approach and cleared the flight of 3 av-8s into the MOA. Recommendation; ensure covering aircraft are on the same altimeter setting.

Original NASA ASRS Text

Title: ZLA Controller described a TCAS RA event when a VFR military flight at 16;500 initiated a TCAS response to IFR traffic at 17;000; the reported noting the aircraft were operating on different altimeter settings.

Narrative: I was working a KC-135 out of a MOA. The KC-135 was level at 17;000 FT. I was also working a flight of 3 AV-8s; en route to the MOA the KC-135 just departed. Wake was level at 16;500 VFR with the BLH altimeter. The KC-135 was level at 17;000 with the EED altimeter. The difference of altimeter was .01 at the time. Traffic was issued to each aircraft at 6 miles and a wake turbulence advisory was give to the flight of 3 AV-8s. The flight of 3 AV-8s reported the KC-135 in sight. As the KC-135 approached the AV-8s; about 12 o'clock and 1 mile; he said he was responding to a RA. I rogered him; as I had no other traffic in his vicinity. He then said the traffic looked more like 300 FT below. After the traffic passed; I shipped the KC-135 to Yuma Approach and cleared the flight of 3 AV-8s into the MOA. Recommendation; ensure covering aircraft are on the same altimeter setting.

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	922728
Time
Date	201012
Local Time Of Day	1801-2400
Place
Locale Reference	ZLA.ARTCC
State Reference	CA
Aircraft 1
Make Model Name	Stratolifter (C-135)/Stratotanker (KC-135)
Operating Under FAR Part	Part 91
Flight Phase	Cruise
Route In Use	None
Aircraft 2
Make Model Name	AV8B Harrier II
Operating Under FAR Part	Part 91
Flight Phase	Cruise
Person 1
Function	Enroute
Qualification	Air Traffic Control Fully Certified
Events
Anomaly	ATC Issue All Types

ZLA controller described a TCAS RA event when a VFR military flight at 16;500 initiated a TCAS response to IFR traffic at 17;000; the reported noting the aircraft were operating on different altimeter settings.