Narrative:

We were on IFR flight plan and receiving radar vectors for the airport descending through 2700 ft MSL when I noticed an aircraft low at our 11 - 11:30 O'clock position. The aircraft started coming up hard. I then turned the autoplt off and watched as he did a snap roll of some sort which caused him to change directions and come straight toward our flight path. I rolled right to approximately 60 degrees or so to lose altitude fast and keep positive G's on our 6 passenger. When I rolled back to see the aircraft I recognized it as a pitts. He then rolled inverted which caused him to come down at us, so I pitched up hard. He rolled right side up, then inverted and passed right behind us at our altitude and just missed the tail. I reported this near miss with the ATC controller. The ATC controller asked, 'you say a pitts?' we responded yes. I then asked for a phone number to call back on. I apologized to the passenger for the maneuvers, and they understood. Once on the ground, I called ATC and completed the report. I was on speaker phone and all the ATC controllers agreed that the pitts was at fault, but there would be in investigation. The pilot of the pitts told me that he saw us at the last moment when he rolled to avoid us. He then went on to tell me that he was doing a loop with a snap roll on top, but it messed up which caused him to change directions. He then said he went inverted to go back to 2000 ft MSL. That is when he came back at us again. He saw us when he rolled right side up and then rolled inverted to miss us. I told him that I did not want to talk to him, and that I did file an near midair collision report with ATC. The pitts was VFR and did not tell the tower he would be doing aerobatics as he usually did. We were IFR, but in VMC obviously. We did see the aircraft and did avoid a conflict of airspace. If experimental aircraft had xponders it would be a big help to everyone. It was not a factor in our case, but it could be to other aircraft in similar sits had they not seen the conflicting aircraft. Luckily, we were looking outside and saw the pitts, otherwise it would have been awful. Thanks to sterile cockpit below 10000 ft and VMC, this accident was avoided.

Related reports:

Google
 

Original NASA ASRS Text

Title: LJ31 CREW HAD NMAC WITH PITTS DOING AEROBATICS 5-10 MI S OF OWB ON THE ILS TO RWY 36 IN OWB CLASS D AIRSPACE.

Narrative: WE WERE ON IFR FLT PLAN AND RECEIVING RADAR VECTORS FOR THE ARPT DSNDING THROUGH 2700 FT MSL WHEN I NOTICED AN ACFT LOW AT OUR 11 - 11:30 O'CLOCK POS. THE ACFT STARTED COMING UP HARD. I THEN TURNED THE AUTOPLT OFF AND WATCHED AS HE DID A SNAP ROLL OF SOME SORT WHICH CAUSED HIM TO CHANGE DIRECTIONS AND COME STRAIGHT TOWARD OUR FLT PATH. I ROLLED R TO APPROX 60 DEGS OR SO TO LOSE ALT FAST AND KEEP POSITIVE G'S ON OUR 6 PAX. WHEN I ROLLED BACK TO SEE THE ACFT I RECOGNIZED IT AS A PITTS. HE THEN ROLLED INVERTED WHICH CAUSED HIM TO COME DOWN AT US, SO I PITCHED UP HARD. HE ROLLED RIGHT SIDE UP, THEN INVERTED AND PASSED RIGHT BEHIND US AT OUR ALT AND JUST MISSED THE TAIL. I RPTED THIS NEAR MISS WITH THE ATC CTLR. THE ATC CTLR ASKED, 'YOU SAY A PITTS?' WE RESPONDED YES. I THEN ASKED FOR A PHONE NUMBER TO CALL BACK ON. I APOLOGIZED TO THE PAX FOR THE MANEUVERS, AND THEY UNDERSTOOD. ONCE ON THE GND, I CALLED ATC AND COMPLETED THE RPT. I WAS ON SPEAKER PHONE AND ALL THE ATC CTLRS AGREED THAT THE PITTS WAS AT FAULT, BUT THERE WOULD BE IN INVESTIGATION. THE PLT OF THE PITTS TOLD ME THAT HE SAW US AT THE LAST MOMENT WHEN HE ROLLED TO AVOID US. HE THEN WENT ON TO TELL ME THAT HE WAS DOING A LOOP WITH A SNAP ROLL ON TOP, BUT IT MESSED UP WHICH CAUSED HIM TO CHANGE DIRECTIONS. HE THEN SAID HE WENT INVERTED TO GO BACK TO 2000 FT MSL. THAT IS WHEN HE CAME BACK AT US AGAIN. HE SAW US WHEN HE ROLLED RIGHT SIDE UP AND THEN ROLLED INVERTED TO MISS US. I TOLD HIM THAT I DID NOT WANT TO TALK TO HIM, AND THAT I DID FILE AN NMAC RPT WITH ATC. THE PITTS WAS VFR AND DID NOT TELL THE TWR HE WOULD BE DOING AEROBATICS AS HE USUALLY DID. WE WERE IFR, BUT IN VMC OBVIOUSLY. WE DID SEE THE ACFT AND DID AVOID A CONFLICT OF AIRSPACE. IF EXPERIMENTAL ACFT HAD XPONDERS IT WOULD BE A BIG HELP TO EVERYONE. IT WAS NOT A FACTOR IN OUR CASE, BUT IT COULD BE TO OTHER ACFT IN SIMILAR SITS HAD THEY NOT SEEN THE CONFLICTING ACFT. LUCKILY, WE WERE LOOKING OUTSIDE AND SAW THE PITTS, OTHERWISE IT WOULD HAVE BEEN AWFUL. THANKS TO STERILE COCKPIT BELOW 10000 FT AND VMC, THIS ACCIDENT WAS AVOIDED.

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.