Narrative:

On jul/xx/96, I flew 6 passenger from boulder city to marble canyon. 3 other pilots and myself then returned to boulder city with zero passenger. The following statements are a description of the flight. Since I fly this area and route often, I was aware of forest fires in the area along our route. The fires had been burning for quite a few days. I knew restr airspace had been implemented for the area. We checked the NOTAM with FSS. The restr area designated r- 4806 covered this area of the kaibab national forest. It was my understanding the restr area was 2000 ft AGL and below. The way we interpreted the surface map, the fire seemed to be at an elevation of slightly lower than 6500 ft MSL. Therefore, the 3 pilots and myself believed 8500 ft MSL would keep us clear of the restr airspace R-4806. As we flew across this area, at approximately 8500 ft MSL, we monitored the air recon frequency of 123.05. Our company had been communicating with the forestry service in the area the previous days of the fire. On this day, there seemed to be no one on frequency, or in the area. Just after we cleared the area, a cessna 340 began weaving in and out of our 4 planes. I would estimate it crossed front of my flight path by a distance of 80-90 ft horizontal. It was close enough for my aircraft to fly through its wake turbulence. He then proceeded to pull up to my 8 O'clock position at a distance of approximately 40-50 ft. This is when I realized I had probably intruded on R-4806. Upon returning to boulder city, my company informed me of my violation. My error is in the interpretation of the R-4806. I did not realize 2000 ft AGL included the rising terrain of the kaibab plateau which rises up to approximately 8300 ft MSL. Had I realized this, I would have flown at 10500 ft MSL and there would have been no problem. Callback conversation with reporter revealed the following information: the rptrs were all flying cessna 207 aircraft in a very loose formation. The FAA gave each of them a letter of warning. Most of the rptrs have moved on to other jobs. Supplemental information from acn 340293: a NOTAM had been issued stating R-4806 was located at the gcn VOR 332 degree radial 42 DME position from the surface to 2000 ft AGL, then out to a radius of 15 mi. I had then found the approximately location of the center of R-4806 and determined the elevation to be roughly 6500 ft MSL. I measured 2000 ft AGL above the center and determined that an altitude of approximately 8500 ft MSL would be sufficient to remain clear of the area. A twin cessna settled less than 20 ft off my left wing. Supplemental information from acn 340128: I departed the marble canyon airport (L41) #3 of 5 aircraft.

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Original NASA ASRS Text

Title: A FORMATION OF 5 SMA FLEW THROUGH A TEMPORARY RESTR AREA WITHOUT CLRNC. ERROR ADMITTED. DESIGNATED MOUNTAINOUS TERRAIN. NMAC BY INTERCEPT ACFT WITH RPTRS.

Narrative: ON JUL/XX/96, I FLEW 6 PAX FROM BOULDER CITY TO MARBLE CANYON. 3 OTHER PLTS AND MYSELF THEN RETURNED TO BOULDER CITY WITH ZERO PAX. THE FOLLOWING STATEMENTS ARE A DESCRIPTION OF THE FLT. SINCE I FLY THIS AREA AND RTE OFTEN, I WAS AWARE OF FOREST FIRES IN THE AREA ALONG OUR RTE. THE FIRES HAD BEEN BURNING FOR QUITE A FEW DAYS. I KNEW RESTR AIRSPACE HAD BEEN IMPLEMENTED FOR THE AREA. WE CHKED THE NOTAM WITH FSS. THE RESTR AREA DESIGNATED R- 4806 COVERED THIS AREA OF THE KAIBAB NATIONAL FOREST. IT WAS MY UNDERSTANDING THE RESTR AREA WAS 2000 FT AGL AND BELOW. THE WAY WE INTERPRETED THE SURFACE MAP, THE FIRE SEEMED TO BE AT AN ELEVATION OF SLIGHTLY LOWER THAN 6500 FT MSL. THEREFORE, THE 3 PLTS AND MYSELF BELIEVED 8500 FT MSL WOULD KEEP US CLR OF THE RESTR AIRSPACE R-4806. AS WE FLEW ACROSS THIS AREA, AT APPROX 8500 FT MSL, WE MONITORED THE AIR RECON FREQ OF 123.05. OUR COMPANY HAD BEEN COMMUNICATING WITH THE FORESTRY SVC IN THE AREA THE PREVIOUS DAYS OF THE FIRE. ON THIS DAY, THERE SEEMED TO BE NO ONE ON FREQ, OR IN THE AREA. JUST AFTER WE CLRED THE AREA, A CESSNA 340 BEGAN WEAVING IN AND OUT OF OUR 4 PLANES. I WOULD ESTIMATE IT CROSSED FRONT OF MY FLT PATH BY A DISTANCE OF 80-90 FT HORIZ. IT WAS CLOSE ENOUGH FOR MY ACFT TO FLY THROUGH ITS WAKE TURB. HE THEN PROCEEDED TO PULL UP TO MY 8 O'CLOCK POS AT A DISTANCE OF APPROX 40-50 FT. THIS IS WHEN I REALIZED I HAD PROBABLY INTRUDED ON R-4806. UPON RETURNING TO BOULDER CITY, MY COMPANY INFORMED ME OF MY VIOLATION. MY ERROR IS IN THE INTERP OF THE R-4806. I DID NOT REALIZE 2000 FT AGL INCLUDED THE RISING TERRAIN OF THE KAIBAB PLATEAU WHICH RISES UP TO APPROX 8300 FT MSL. HAD I REALIZED THIS, I WOULD HAVE FLOWN AT 10500 FT MSL AND THERE WOULD HAVE BEEN NO PROB. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTRS WERE ALL FLYING CESSNA 207 ACFT IN A VERY LOOSE FORMATION. THE FAA GAVE EACH OF THEM A LETTER OF WARNING. MOST OF THE RPTRS HAVE MOVED ON TO OTHER JOBS. SUPPLEMENTAL INFO FROM ACN 340293: A NOTAM HAD BEEN ISSUED STATING R-4806 WAS LOCATED AT THE GCN VOR 332 DEG RADIAL 42 DME POS FROM THE SURFACE TO 2000 FT AGL, THEN OUT TO A RADIUS OF 15 MI. I HAD THEN FOUND THE APPROX LOCATION OF THE CTR OF R-4806 AND DETERMINED THE ELEVATION TO BE ROUGHLY 6500 FT MSL. I MEASURED 2000 FT AGL ABOVE THE CTR AND DETERMINED THAT AN ALT OF APPROX 8500 FT MSL WOULD BE SUFFICIENT TO REMAIN CLR OF THE AREA. A TWIN CESSNA SETTLED LESS THAN 20 FT OFF MY L WING. SUPPLEMENTAL INFO FROM ACN 340128: I DEPARTED THE MARBLE CANYON ARPT (L41) #3 OF 5 ACFT.

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.