PA28 pilot on a right dowinwind reports a near midair collision in the pattern at mvy with an aircra...

Narrative:

I was working cape approach while enroute to mvy from the southwest. Cape handed me off to the tower who advised me to report a right downwind entry. From my direction of flight a right base would have been a better line up. I requested a right base and was granted same. There were multiple aircraft in the area to both land and takeoff. It became clear as I approached that a right base would put me in conflict with another aircraft on a right base further out to my left. I advised the tower that I thought a right downwind would in fact be better and he concurred and I altered course for the right downwind. While on approach and established parallel to the runway on the right downwind at or near pattern altitude the tower controller requested I extend my downwind for other aircraft. I acknowledged same. In a split second out of the corner of my eye I saw another aircraft to my left (aircraft Y) on a right base. Aircraft Y passed underneath me by a very slim margin; less than 200 feet; perhaps less than 100 feet. It was very quick. If we had been at the same altitude we would have collided. I advised the tower controller of the event and the only response was 'that's why I told you to extend the downwind' the airport went from quiet to extremely busy in a very short period of time. I am not sure if the controller did not know of aircraft Y's position or if I misinterpreted my instructions but if the latter I did repeat everything and I believe the controller acknowledged same. I was expecting aircraft Y to be inside my position and not outside my position. My attention was focused towards the airport with only occasional glances to my left. I was asked once again to extend the downwind and continued the downwind to fall in behind a pc-12 on final; the rest of the flight was uneventful. I don't know how the pilot of aircraft Y could have missed me; I was right in front of him. My only explanation is that he may have been looking to his right for me; thinking I was more abeam the tower area on the right downwind.

Original NASA ASRS Text

Title: PA28 pilot on a right dowinwind reports a NMAC in the pattern at MVY with an aircraft crossing on a right base. The Tower did not advise either pilot of the impending conflict.

Narrative: I was working Cape Approach while enroute to MVY from the southwest. Cape handed me off to the tower who advised me to report a right downwind entry. From my direction of flight a right base would have been a better line up. I requested a right base and was granted same. There were multiple aircraft in the area to both land and takeoff. It became clear as I approached that a right base would put me in conflict with another aircraft on a right base further out to my left. I advised the tower that I thought a right downwind would in fact be better and he concurred and I altered course for the right downwind. While on approach and established parallel to the runway on the right downwind at or near pattern altitude the tower controller requested I extend my downwind for other aircraft. I acknowledged same. In a split second out of the corner of my eye I saw another aircraft to my left (Aircraft Y) on a right base. Aircraft Y passed underneath me by a very slim margin; less than 200 feet; perhaps less than 100 feet. It was very quick. If we had been at the same altitude we would have collided. I advised the tower controller of the event and the only response was 'that's why I told you to extend the downwind' The airport went from quiet to extremely busy in a very short period of time. I am not sure if the controller did not know of Aircraft Y's position or if I misinterpreted my instructions but if the latter I did repeat everything and I believe the controller acknowledged same. I was expecting Aircraft Y to be inside my position and not outside my position. My attention was focused towards the airport with only occasional glances to my left. I was asked once again to extend the downwind and continued the downwind to fall in behind a PC-12 on final; the rest of the flight was uneventful. I don't know how the pilot of Aircraft Y could have missed me; I was right in front of him. My only explanation is that he may have been looking to his right for me; thinking I was more abeam the tower area on the right downwind.

Data retrieved from NASA's ASRS site 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.

Attributes
ACN	1208013
Time
Date	201409
Local Time Of Day	0601-1200
Place
Locale Reference	MVY.Airport
State Reference	MA
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	PA-28R Cherokee Arrow All Series
Operating Under FAR Part	Part 91
Flight Phase	Descent
Route In Use	Direct
Flight Plan	VFR
Aircraft 2
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Flight Phase	Descent
Person 1
Function	Single Pilot Pilot Flying
Qualification	Flight Crew Commercial Flight Crew Instrument Flight Crew Multiengine
Experience	Flight Crew Last 90 Days 15 Flight Crew Total 1700 Flight Crew Type 700
Events
Anomaly	Conflict NMAC
Miss Distance	Horizontal 0 Vertical 100

PA28 pilot on a right dowinwind reports a near midair collision in the pattern at mvy with an aircraft crossing on a right base. The tower did not advise either pilot of the impending conflict.