A PA28 CFI reported an near midair collision in N90's airspace.

Attributes
ACN	588816
Time
Date	200307
Day	Tue
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : isp.airport
State Reference	NY
Altitude	msl single value : 1700
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Operator	general aviation : instructional
Make Model Name	PA-28 Cherokee/Archer II/Dakota/Pillan/Warrior
Operating Under FAR Part	Part 91
Flight Phase	cruise : level
Flight Plan	None
Aircraft 2
Operator	general aviation : personal
Make Model Name	Skyhawk 172/Cutlass 172
Operating Under FAR Part	Part 91
Flight Phase	cruise : level
Person 1
Affiliation	other
Function	flight crew : single pilot instruction : instructor oversight : pic
Qualification	pilot : commercial pilot : instrument pilot : multi engine pilot : cfi
Experience	flight time last 90 days : 100 flight time total : 600 flight time type : 150
ASRS Report	588816
Person 2
Affiliation	other
Function	flight crew : single pilot instruction : trainee
Events
Anomaly	conflict : nmac
Independent Detector	other flight crewa
Resolutory Action	flight crew : took evasive action
Miss Distance	horizontal : 100 vertical : 10
Supplementary
Problem Areas	Flight Crew Human Performance
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Our low wing cherokee almost collided with a high wing cessna along the southern coast of long island. We had just leveled off from a descent as we traveled east along the coast. We saw a northbound cessna at our 3 O'clock about 100 ft away from us at or slightly below our altitude. We executed a climbing left turn, while the cessna executed a descending turn to its left. We failed to see the cessna, because he was below our wing. I am not sure why he did not see our cherokee. Approach was not providing advisories, because their radar was inoperative.

Original NASA ASRS Text

Title: A PA28 CFI RPTED AN NMAC IN N90'S AIRSPACE.

Narrative: OUR LOW WING CHEROKEE ALMOST COLLIDED WITH A HIGH WING CESSNA ALONG THE SOUTHERN COAST OF LONG ISLAND. WE HAD JUST LEVELED OFF FROM A DSCNT AS WE TRAVELED E ALONG THE COAST. WE SAW A NBOUND CESSNA AT OUR 3 O'CLOCK ABOUT 100 FT AWAY FROM US AT OR SLIGHTLY BELOW OUR ALT. WE EXECUTED A CLBING L TURN, WHILE THE CESSNA EXECUTED A DSNDING TURN TO ITS L. WE FAILED TO SEE THE CESSNA, BECAUSE HE WAS BELOW OUR WING. I AM NOT SURE WHY HE DID NOT SEE OUR CHEROKEE. APCH WAS NOT PROVIDING ADVISORIES, BECAUSE THEIR RADAR WAS INOP.

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.