Narrative:

I was approaching the ash airport from the north, receiving advisories and class C service from mht. I was kept higher than usual (4500 ft versus 2500 ft typically) probably due to the use of a new ILS approach to mht runway 6. Mht approach instructed me to descend (from 4500 ft to the 1200 ft ash pattern altitude) approximately 7 mi north of ash and contact ash tower. I started a descent and attempted to contact nashua tower on 133.2 MHZ but was unable due to frequency congestion. I circled for descent outside of nashua's class D airspace 5 mi to the north. I started inbound to the field after establishing communications with ash tower and notifying them of my position 5 mi to the north on a '45 degree entry to right downwind runway 32.' the tower later asked my distance from the field, to which I responded '2.5 mi north.' they assigned me to 'enter left downwind for runway 32 and report midfield.' I accepted this clearance but quickly realized this would cause me to cross the departure end of runway 32, about 1 mi off the departure end, where I could see one aircraft approaching the 1200 ft pattern altitude and had knowledge of another aircraft departing. I attempted to raise the tower to request a right downwind but was unable due to frequency congestion. I continued toward the airport while attempting to raise the tower. I was able to talk to the tower upon reaching 'midfield of the right downwind.' my appearing on the right downwind upset the tower's sequencing plan of a twin on the right downwind and single engine aircraft on the left downwind. This forced a twin to fly a wide pattern as it caught up to me. I chose to continue to the right downwind while attempting to communicate with the tower after assessing the following options: 1) cross the extended centerline to get to the left downwind thus creating a conflict with departing aircraft at the same altitude that I would be crossing. 2) circle 2 mi north of the airport at pattern altitude while attempting to communicate (while this is probably the best option from a regulation point of view, I assessed this as not very safe knowing there were arriving aircraft behind me). 3) climbing circle to the north to depart the area. Climbing in this area would put me back into the class C airspace of mht before being able to establish communication with mht approach. 4) continuing toward the right side of the runway, where there was no other traffic in front of me while sorting things out with the tower. Contributing factors: higher than normal approach speed due to steep descent angle from approach control. Being assigned an unexpected left downwind entry that would require me to cross the extended centerline with traffic departing along centerline at same altitude. Accepting the left downwind entry before realizing that this would create a traffic conflict. Continuing toward the right downwind while attempting to communicate with the tower. Significant congestion on the tower frequency delaying re-communication.

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Original NASA ASRS Text

Title: A R DOWNWIND IS FLOWN AFTER A L IS ASSIGNED CAUSING A TFC CONFLICT AND A NEED FOR A NEW PLAN FROM THE TWR CTLR.

Narrative: I WAS APCHING THE ASH ARPT FROM THE N, RECEIVING ADVISORIES AND CLASS C SVC FROM MHT. I WAS KEPT HIGHER THAN USUAL (4500 FT VERSUS 2500 FT TYPICALLY) PROBABLY DUE TO THE USE OF A NEW ILS APCH TO MHT RWY 6. MHT APCH INSTRUCTED ME TO DSND (FROM 4500 FT TO THE 1200 FT ASH PATTERN ALT) APPROX 7 MI N OF ASH AND CONTACT ASH TWR. I STARTED A DSCNT AND ATTEMPTED TO CONTACT NASHUA TWR ON 133.2 MHZ BUT WAS UNABLE DUE TO FREQ CONGESTION. I CIRCLED FOR DSCNT OUTSIDE OF NASHUA'S CLASS D AIRSPACE 5 MI TO THE N. I STARTED INBOUND TO THE FIELD AFTER ESTABLISHING COMS WITH ASH TWR AND NOTIFYING THEM OF MY POS 5 MI TO THE N ON A '45 DEG ENTRY TO R DOWNWIND RWY 32.' THE TWR LATER ASKED MY DISTANCE FROM THE FIELD, TO WHICH I RESPONDED '2.5 MI N.' THEY ASSIGNED ME TO 'ENTER L DOWNWIND FOR RWY 32 AND RPT MIDFIELD.' I ACCEPTED THIS CLRNC BUT QUICKLY REALIZED THIS WOULD CAUSE ME TO CROSS THE DEP END OF RWY 32, ABOUT 1 MI OFF THE DEP END, WHERE I COULD SEE ONE ACFT APCHING THE 1200 FT PATTERN ALT AND HAD KNOWLEDGE OF ANOTHER ACFT DEPARTING. I ATTEMPTED TO RAISE THE TWR TO REQUEST A R DOWNWIND BUT WAS UNABLE DUE TO FREQ CONGESTION. I CONTINUED TOWARD THE ARPT WHILE ATTEMPTING TO RAISE THE TWR. I WAS ABLE TO TALK TO THE TWR UPON REACHING 'MIDFIELD OF THE R DOWNWIND.' MY APPEARING ON THE R DOWNWIND UPSET THE TWR'S SEQUENCING PLAN OF A TWIN ON THE R DOWNWIND AND SINGLE ENG ACFT ON THE L DOWNWIND. THIS FORCED A TWIN TO FLY A WIDE PATTERN AS IT CAUGHT UP TO ME. I CHOSE TO CONTINUE TO THE R DOWNWIND WHILE ATTEMPTING TO COMMUNICATE WITH THE TWR AFTER ASSESSING THE FOLLOWING OPTIONS: 1) CROSS THE EXTENDED CTRLINE TO GET TO THE L DOWNWIND THUS CREATING A CONFLICT WITH DEPARTING ACFT AT THE SAME ALT THAT I WOULD BE XING. 2) CIRCLE 2 MI N OF THE ARPT AT PATTERN ALT WHILE ATTEMPTING TO COMMUNICATE (WHILE THIS IS PROBABLY THE BEST OPTION FROM A REG POINT OF VIEW, I ASSESSED THIS AS NOT VERY SAFE KNOWING THERE WERE ARRIVING ACFT BEHIND ME). 3) CLBING CIRCLE TO THE N TO DEPART THE AREA. CLBING IN THIS AREA WOULD PUT ME BACK INTO THE CLASS C AIRSPACE OF MHT BEFORE BEING ABLE TO ESTABLISH COM WITH MHT APCH. 4) CONTINUING TOWARD THE R SIDE OF THE RWY, WHERE THERE WAS NO OTHER TFC IN FRONT OF ME WHILE SORTING THINGS OUT WITH THE TWR. CONTRIBUTING FACTORS: HIGHER THAN NORMAL APCH SPD DUE TO STEEP DSCNT ANGLE FROM APCH CTL. BEING ASSIGNED AN UNEXPECTED L DOWNWIND ENTRY THAT WOULD REQUIRE ME TO CROSS THE EXTENDED CTRLINE WITH TFC DEPARTING ALONG CTRLINE AT SAME ALT. ACCEPTING THE L DOWNWIND ENTRY BEFORE REALIZING THAT THIS WOULD CREATE A TFC CONFLICT. CONTINUING TOWARD THE R DOWNWIND WHILE ATTEMPTING TO COMMUNICATE WITH THE TWR. SIGNIFICANT CONGESTION ON THE TWR FREQ DELAYING RE-COM.

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.