Narrative:

A piper cherokee 235, plted by the reporter of this safety report, was cleared to enter a right downwind for runway 23 at bed, ma, but instead inadvertently initially set up for a left downwind. Upon insistence to use right downwind by the tower controller, who appeared unaware of my actual position, I made an unintended poor decision to cross in front of departing traffic, along the upwind leg. Departing traffic, a piper warrior, was close but never on a collision course and was fully in sight at all times. The sequence of events is described here. At 9 mi ssw of hanscom field, heading approximately 030 degrees, bos approach control ceased radar services and advised me to contact hanscom tower. Due to extreme congestion on the tower frequency, the initial call to hanscom tower was made very brief 'hanscom tower, n-number, 7 mi southwest, ATIS information.' tower replied, '...enter right downwind runway 23.' at this point, in spite of great visibility and clear afternoon skies, I could not see the departure end of runway 23. The departure end was obscured by trees I would later figure out. I was not aware at first that I was on the left downwind side of the extended centerline. Using the airport diagram of the terminal procedure for orientation (reference 1) provided further confusion as I did not realize immediately that north is not aligned with the top of the page. It is aligned to the left of the page. Therefore, I expected to see runway 5/23 in a different position relative to the tower and terminal building that were visible to me. I am not very familiar with hanscom field, having been there only 3 or 4 times, always under IFR guidance to the runway. No terrain features exist for orientation southwest of hanscom as it is wooded over a large area. Additionally, no VOR or ADF navigation is present on the field for directional orientation. But a large factor in me not turning north early on to enter the traffic pattern of runway 23 from the west on right downwind was worse than expected pilot fatigue. For several preceding nights, minimal sleep was had. There was present enough information, compass heading of 030 degrees, to realize that I was on the wrong side of the centerline for right downwind. At 3 mi from the airport, still not able to see the departure end, I did figure out based on heading that I was on the wrong side of the centerline to enter right downwind. But now a steady stream of departing aircraft prevented the turn to the north. And the tower frequency was so busy that I was unable to request a left downwind until about 1 mi from the departure end. The tower controller, not anticipating my actual position, insisted on a right downwind as previously cleared. At this point I determined, in haste, that I could squeeze between a departing C152 and an in-trail piper warrior. A better plan, given a moment to think about it, would have been to do a 180 degree turn out of the area or just enter the left downwind, thus not requiring a maneuver between departing traffic. Understand though that at that moment either of those options would have required further pilot/controller interaction on already congested frequency. The remainder of the landing was uneventful beside the continued extreme frequency congestion. See the attached diagram for further detail. Possible corrective actions, besides human performance lessons well learned by the reporting pilot, are increased controllers and/or airspace restrs at extremely busy class D airports such at pal-waukee, teterboro, and hanscom. I almost consider these locations to be unsafe on clear VFR days as there are so many aircraft in the class D airspace.

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Original NASA ASRS Text

Title: PA28 PLT DID NOT FOLLOW TWR INSTRUCTIONS FOR PATTERN ENTRY AT BED.

Narrative: A PIPER CHEROKEE 235, PLTED BY THE RPTR OF THIS SAFETY RPT, WAS CLRED TO ENTER A R DOWNWIND FOR RWY 23 AT BED, MA, BUT INSTEAD INADVERTENTLY INITIALLY SET UP FOR A L DOWNWIND. UPON INSISTENCE TO USE R DOWNWIND BY THE TWR CTLR, WHO APPEARED UNAWARE OF MY ACTUAL POS, I MADE AN UNINTENDED POOR DECISION TO CROSS IN FRONT OF DEPARTING TFC, ALONG THE UPWIND LEG. DEPARTING TFC, A PIPER WARRIOR, WAS CLOSE BUT NEVER ON A COLLISION COURSE AND WAS FULLY IN SIGHT AT ALL TIMES. THE SEQUENCE OF EVENTS IS DESCRIBED HERE. AT 9 MI SSW OF HANSCOM FIELD, HDG APPROX 030 DEGS, BOS APCH CTL CEASED RADAR SVCS AND ADVISED ME TO CONTACT HANSCOM TWR. DUE TO EXTREME CONGESTION ON THE TWR FREQ, THE INITIAL CALL TO HANSCOM TWR WAS MADE VERY BRIEF 'HANSCOM TWR, N-NUMBER, 7 MI SW, ATIS INFO.' TWR REPLIED, '...ENTER R DOWNWIND RWY 23.' AT THIS POINT, IN SPITE OF GREAT VISIBILITY AND CLR AFTERNOON SKIES, I COULD NOT SEE THE DEP END OF RWY 23. THE DEP END WAS OBSCURED BY TREES I WOULD LATER FIGURE OUT. I WAS NOT AWARE AT FIRST THAT I WAS ON THE L DOWNWIND SIDE OF THE EXTENDED CTRLINE. USING THE ARPT DIAGRAM OF THE TERMINAL PROC FOR ORIENTATION (REF 1) PROVIDED FURTHER CONFUSION AS I DID NOT REALIZE IMMEDIATELY THAT N IS NOT ALIGNED WITH THE TOP OF THE PAGE. IT IS ALIGNED TO THE L OF THE PAGE. THEREFORE, I EXPECTED TO SEE RWY 5/23 IN A DIFFERENT POS RELATIVE TO THE TWR AND TERMINAL BUILDING THAT WERE VISIBLE TO ME. I AM NOT VERY FAMILIAR WITH HANSCOM FIELD, HAVING BEEN THERE ONLY 3 OR 4 TIMES, ALWAYS UNDER IFR GUIDANCE TO THE RWY. NO TERRAIN FEATURES EXIST FOR ORIENTATION SW OF HANSCOM AS IT IS WOODED OVER A LARGE AREA. ADDITIONALLY, NO VOR OR ADF NAV IS PRESENT ON THE FIELD FOR DIRECTIONAL ORIENTATION. BUT A LARGE FACTOR IN ME NOT TURNING N EARLY ON TO ENTER THE TFC PATTERN OF RWY 23 FROM THE W ON R DOWNWIND WAS WORSE THAN EXPECTED PLT FATIGUE. FOR SEVERAL PRECEDING NIGHTS, MINIMAL SLEEP WAS HAD. THERE WAS PRESENT ENOUGH INFO, COMPASS HDG OF 030 DEGS, TO REALIZE THAT I WAS ON THE WRONG SIDE OF THE CTRLINE FOR R DOWNWIND. AT 3 MI FROM THE ARPT, STILL NOT ABLE TO SEE THE DEP END, I DID FIGURE OUT BASED ON HDG THAT I WAS ON THE WRONG SIDE OF THE CTRLINE TO ENTER R DOWNWIND. BUT NOW A STEADY STREAM OF DEPARTING ACFT PREVENTED THE TURN TO THE N. AND THE TWR FREQ WAS SO BUSY THAT I WAS UNABLE TO REQUEST A L DOWNWIND UNTIL ABOUT 1 MI FROM THE DEP END. THE TWR CTLR, NOT ANTICIPATING MY ACTUAL POS, INSISTED ON A R DOWNWIND AS PREVIOUSLY CLRED. AT THIS POINT I DETERMINED, IN HASTE, THAT I COULD SQUEEZE BTWN A DEPARTING C152 AND AN IN-TRAIL PIPER WARRIOR. A BETTER PLAN, GIVEN A MOMENT TO THINK ABOUT IT, WOULD HAVE BEEN TO DO A 180 DEG TURN OUT OF THE AREA OR JUST ENTER THE L DOWNWIND, THUS NOT REQUIRING A MANEUVER BTWN DEPARTING TFC. UNDERSTAND THOUGH THAT AT THAT MOMENT EITHER OF THOSE OPTIONS WOULD HAVE REQUIRED FURTHER PLT/CTLR INTERACTION ON ALREADY CONGESTED FREQ. THE REMAINDER OF THE LNDG WAS UNEVENTFUL BESIDE THE CONTINUED EXTREME FREQ CONGESTION. SEE THE ATTACHED DIAGRAM FOR FURTHER DETAIL. POSSIBLE CORRECTIVE ACTIONS, BESIDES HUMAN PERFORMANCE LESSONS WELL LEARNED BY THE RPTING PLT, ARE INCREASED CTLRS AND/OR AIRSPACE RESTRS AT EXTREMELY BUSY CLASS D ARPTS SUCH AT PAL-WAUKEE, TETERBORO, AND HANSCOM. I ALMOST CONSIDER THESE LOCATIONS TO BE UNSAFE ON CLR VFR DAYS AS THERE ARE SO MANY ACFT IN THE CLASS D AIRSPACE.

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.