Narrative:

I entered the phx TCA at casa grande airport approximately 30 mi south of phx at 4500 ft. I was cleared into the TCA and told to maintain 3500 ft. I asked for an altimeter setting and received 29.92. When I was approaching memorial airport, approach advised of traffic flying west to east at 3100 ft (traffic was not in contact with approach control). As the traffic approached I was advised by approach control of a TA. By this time traffic was in sight and flew under me. As I got closer to ahwatukee (town) I was again advised of an small transport crossing my flight path at 3100 ft. The small transport was advised that I was at 3500 ft. I saw the small transport and no conflict occurred. I was then handed off to approach on 120.7 and given a new altimeter setting of 29.84. As I was putting in the new setting I was advised of an small aircraft at 3100 ft opposite direction. The controller then told me I was showing 3400 ft on his scope. I assume that was caused by me changing at that time to 29.84 from 29.92. I then called him back and he said I was now indicating 3500 ft. He also said that at one time the reading was as low as 3300 ft, and remarked I was within tolerance, and said no more until he terminated control. I am concerned with why 2 different altimeter settings in less than 25 NM, and why they had me at 3500 ft, 30 NM out when they normally have you at 4500-6500 ft. I should have questioned the altitude, since I have had 2 near misses at the same locations before, when under their control, requiring extreme evasive maneuvers. The traffic both times were not talking to phx approach and approach did not advise me of their presence.

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Original NASA ASRS Text

Title: SMA PLT USES ALTIMETER SETTING GIVEN BUT IS BELOW ASSIGNED ALT AND RECEIVES CHANGE OF ALTIMETER SETTING WITHIN 25 MI. HAS NMAC.

Narrative: I ENTERED THE PHX TCA AT CASA GRANDE ARPT APPROX 30 MI S OF PHX AT 4500 FT. I WAS CLRED INTO THE TCA AND TOLD TO MAINTAIN 3500 FT. I ASKED FOR AN ALTIMETER SETTING AND RECEIVED 29.92. WHEN I WAS APCHING MEMORIAL ARPT, APCH ADVISED OF TFC FLYING W TO E AT 3100 FT (TFC WAS NOT IN CONTACT WITH APCH CTL). AS THE TFC APCHED I WAS ADVISED BY APCH CTL OF A TA. BY THIS TIME TFC WAS IN SIGHT AND FLEW UNDER ME. AS I GOT CLOSER TO AHWATUKEE (TOWN) I WAS AGAIN ADVISED OF AN SMT XING MY FLT PATH AT 3100 FT. THE SMT WAS ADVISED THAT I WAS AT 3500 FT. I SAW THE SMT AND NO CONFLICT OCCURRED. I WAS THEN HANDED OFF TO APCH ON 120.7 AND GIVEN A NEW ALTIMETER SETTING OF 29.84. AS I WAS PUTTING IN THE NEW SETTING I WAS ADVISED OF AN SMA AT 3100 FT OPPOSITE DIRECTION. THE CTLR THEN TOLD ME I WAS SHOWING 3400 FT ON HIS SCOPE. I ASSUME THAT WAS CAUSED BY ME CHANGING AT THAT TIME TO 29.84 FROM 29.92. I THEN CALLED HIM BACK AND HE SAID I WAS NOW INDICATING 3500 FT. HE ALSO SAID THAT AT ONE TIME THE READING WAS AS LOW AS 3300 FT, AND REMARKED I WAS WITHIN TOLERANCE, AND SAID NO MORE UNTIL HE TERMINATED CTL. I AM CONCERNED WITH WHY 2 DIFFERENT ALTIMETER SETTINGS IN LESS THAN 25 NM, AND WHY THEY HAD ME AT 3500 FT, 30 NM OUT WHEN THEY NORMALLY HAVE YOU AT 4500-6500 FT. I SHOULD HAVE QUESTIONED THE ALT, SINCE I HAVE HAD 2 NEAR MISSES AT THE SAME LOCATIONS BEFORE, WHEN UNDER THEIR CTL, REQUIRING EXTREME EVASIVE MANEUVERS. THE TFC BOTH TIMES WERE NOT TALKING TO PHX APCH AND APCH DID NOT ADVISE ME OF THEIR PRESENCE.

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.