C172 instructor and student have an near midair collision on final approach.

Attributes
ACN	726823
Time
Date	200702
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : zzz.airport
State Reference	US
Altitude	agl single value : 300
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Operator	general aviation : instructional
Make Model Name	Skyhawk 172/Cutlass 172
Operating Under FAR Part	Part 91
Flight Phase	descent : approach
Flight Plan	None
Aircraft 2
Operator	general aviation : personal
Make Model Name	Robinson R22
Operating Under FAR Part	Part 91
Flight Phase	descent : approach
Person 1
Affiliation	other
Function	instruction : instructor
Qualification	pilot : cfi pilot : instrument
Experience	flight time last 90 days : 30 flight time total : 980 flight time type : 500
ASRS Report	726823
Person 2
Affiliation	other
Function	flight crew : single pilot
Events
Anomaly	conflict : nmac other spatial deviation
Independent Detector	other flight crewa
Resolutory Action	flight crew : took evasive action
Miss Distance	horizontal : 50 vertical : 200
Supplementary
Problem Areas	Flight Crew Human Performance
Primary Problem	Flight Crew Human Performance

Narrative:

I was instructing a private pilot student; remaining in the conventional l-hand traffic pattern for runway xx. Traffic had varied between runway yy and runway xx throughout the day with winds somewhat in between. The student was making most of the radio calls but I was helping out at the time because another airplane was in the pattern to land on runway yy. We clearly communicated with that pilot and seemed to have no problems getting good radio reception from him; we visually ascertained each others' whereabouts; and were no factor with him. Upon turning base for the next landing; I noticed the helicopter operating to the right side of runway xx. I had heard no radio calls from him; and because I know the flight school that operates this helicopter and know that they are typically very good at communicating intentions when getting close to fixed wing traffic; I assumed that they must just be maneuvering to the side of the airport but were not inbound for landing. This is a common practice for them; and I have gotten used to seeing them off to the side of the runway. I made sure my student made a radio call 'turning base to final' just to ensure they knew we were there. After a few more seconds; the helicopter seemed to be converging with us approaching a final path for runway xx. Just to be safe; I then made a radio call announcing short final for runway xx. Since there was no response from the helicopter; I assumed they knew they were not a factor and I continued. I should probably have maneuvered clear at that point since I had no confirmation of their intentions or their knowledge of my whereabouts; but was stuck in my assumption that they must be planning to remain clear. After a few seconds it was clear that we were overtaking them underneath; but at that point a turn seemed like a worse choice than simply accelerating our descent to put more vertical distance between us. We flew underneath the descending helicopter and landed.

Original NASA ASRS Text

Title: C172 INSTRUCTOR AND STUDENT HAVE AN NMAC ON FINAL APCH.

Narrative: I WAS INSTRUCTING A PVT PLT STUDENT; REMAINING IN THE CONVENTIONAL L-HAND TFC PATTERN FOR RWY XX. TFC HAD VARIED BTWN RWY YY AND RWY XX THROUGHOUT THE DAY WITH WINDS SOMEWHAT IN BTWN. THE STUDENT WAS MAKING MOST OF THE RADIO CALLS BUT I WAS HELPING OUT AT THE TIME BECAUSE ANOTHER AIRPLANE WAS IN THE PATTERN TO LAND ON RWY YY. WE CLRLY COMMUNICATED WITH THAT PLT AND SEEMED TO HAVE NO PROBS GETTING GOOD RADIO RECEPTION FROM HIM; WE VISUALLY ASCERTAINED EACH OTHERS' WHEREABOUTS; AND WERE NO FACTOR WITH HIM. UPON TURNING BASE FOR THE NEXT LNDG; I NOTICED THE HELI OPERATING TO THE R SIDE OF RWY XX. I HAD HEARD NO RADIO CALLS FROM HIM; AND BECAUSE I KNOW THE FLT SCHOOL THAT OPERATES THIS HELI AND KNOW THAT THEY ARE TYPICALLY VERY GOOD AT COMMUNICATING INTENTIONS WHEN GETTING CLOSE TO FIXED WING TFC; I ASSUMED THAT THEY MUST JUST BE MANEUVERING TO THE SIDE OF THE ARPT BUT WERE NOT INBOUND FOR LNDG. THIS IS A COMMON PRACTICE FOR THEM; AND I HAVE GOTTEN USED TO SEEING THEM OFF TO THE SIDE OF THE RWY. I MADE SURE MY STUDENT MADE A RADIO CALL 'TURNING BASE TO FINAL' JUST TO ENSURE THEY KNEW WE WERE THERE. AFTER A FEW MORE SECONDS; THE HELI SEEMED TO BE CONVERGING WITH US APCHING A FINAL PATH FOR RWY XX. JUST TO BE SAFE; I THEN MADE A RADIO CALL ANNOUNCING SHORT FINAL FOR RWY XX. SINCE THERE WAS NO RESPONSE FROM THE HELI; I ASSUMED THEY KNEW THEY WERE NOT A FACTOR AND I CONTINUED. I SHOULD PROBABLY HAVE MANEUVERED CLR AT THAT POINT SINCE I HAD NO CONFIRMATION OF THEIR INTENTIONS OR THEIR KNOWLEDGE OF MY WHEREABOUTS; BUT WAS STUCK IN MY ASSUMPTION THAT THEY MUST BE PLANNING TO REMAIN CLR. AFTER A FEW SECONDS IT WAS CLR THAT WE WERE OVERTAKING THEM UNDERNEATH; BUT AT THAT POINT A TURN SEEMED LIKE A WORSE CHOICE THAN SIMPLY ACCELERATING OUR DSCNT TO PUT MORE VERT DISTANCE BTWN US. WE FLEW UNDERNEATH THE DSNDING HELI AND LANDED.

Data retrieved from NASA's ASRS site as of January 2009 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.