Near midair collision between 2 smas in traffic pattern.

Attributes
ACN	188471
Time
Date	199109
Day	Sat
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : sdl
State Reference	AZ
Altitude	msl bound lower : 2000 msl bound upper : 2000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tower : sdl
Operator	general aviation : instructional
Make Model Name	Small Aircraft, High Wing, 1 Eng, Fixed Gear
Flight Phase	descent : approach landing : go around other
Route In Use	approach : straight in approach : visual
Flight Plan	VFR
Aircraft 2
Make Model Name	Small Aircraft
Flight Phase	descent : approach other
Route In Use	approach : visual
Flight Plan	VFR
Person 1
Affiliation	Other
Function	flight crew : single pilot
Qualification	pilot : private
Experience	flight time last 90 days : 30 flight time total : 120 flight time type : 100
ASRS Report	188471
Person 2
Affiliation	Other
Function	flight crew : single pilot
Events
Anomaly	conflict : nmac non adherence : far non adherence : clearance
Independent Detector	other flight crewa
Resolutory Action	controller : issued new clearance other
Consequence	Other
Miss Distance	horizontal : 0 vertical : 200
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

We reported as requested 3 mi final for straight in runway 21. Tower cleared us to land. Traffic (small aircraft Y) reported turning base leg 1/2 mi to our right side, below us. They (small aircraft Y) reported as traffic turning final and ATC instructed them to follow traffic. We saw plane #2 (small aircraft Y) pass under us at 200 ft vertical separation. We reported to tower plane #2 was below us on final as well. Tower instructed us to initiate a 180 degree turn to the right and follow traffic on downwind and were #4 to land. We believe ATC failed to monitor the position of aircraft in the pattern and allowed 2 planes on final at the same distance. Although it's the VFR pilot's responsibility to maintain separation it was impossible to see traffic directly below us and would expect tower to mention the imminent conflict. Traffic at sdl training or otherwise should be monitored more closely.

Original NASA ASRS Text

Title: NMAC BTWN 2 SMAS IN TFC PATTERN.

Narrative: WE RPTED AS REQUESTED 3 MI FINAL FOR STRAIGHT IN RWY 21. TWR CLRED US TO LAND. TFC (SMA Y) RPTED TURNING BASE LEG 1/2 MI TO OUR R SIDE, BELOW US. THEY (SMA Y) RPTED AS TFC TURNING FINAL AND ATC INSTRUCTED THEM TO FOLLOW TFC. WE SAW PLANE #2 (SMA Y) PASS UNDER US AT 200 FT VERT SEPARATION. WE RPTED TO TWR PLANE #2 WAS BELOW US ON FINAL AS WELL. TWR INSTRUCTED US TO INITIATE A 180 DEG TURN TO THE R AND FOLLOW TFC ON DOWNWIND AND WERE #4 TO LAND. WE BELIEVE ATC FAILED TO MONITOR THE POS OF ACFT IN THE PATTERN AND ALLOWED 2 PLANES ON FINAL AT THE SAME DISTANCE. ALTHOUGH IT'S THE VFR PLT'S RESPONSIBILITY TO MAINTAIN SEPARATION IT WAS IMPOSSIBLE TO SEE TFC DIRECTLY BELOW US AND WOULD EXPECT TWR TO MENTION THE IMMINENT CONFLICT. TFC AT SDL TRAINING OR OTHERWISE SHOULD BE MONITORED MORE CLOSELY.

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.