Helicopter instructor pilot reports a near midair collision with a RV4 that had preformed a touch an...

Narrative:

Experimental RV4 flew straight in to S50 making only a single radio call ('final 34; touch and go; helicopter in pattern say position'). Proceeded to enter the traffic pattern by flying directly over the runway south to north over slower departing traffic; without having the traffic in sight; and turning crosswind in front of that traffic. Since we were able; we slowed and stopped climbing (an airplane would have had to slow below stall speed). After landing; the RV4 took off again; passed downwind traffic at a higher rate of speed and descended in front of them to enter a base turn and land again (once again requiring us to slow to <50 KIAS). S50 is used for flight training by multiple flight schools; and non-standard traffic pattern entries by general aviation traffic puts all pilots here at risk for mac. This risk is heightened when low-experience instructors; low-time students; or solo students encounter this erratic behavior. Auburn and the area between S50 and bfi are due for a mac between airplane traffic not using the CTAF; not reporting or coordinating with other traffic; flying at a higher rate of speed than flight training aircraft; and at low altitudes.

Original NASA ASRS Text

Title: Helicopter instructor pilot reports a NMAC with a RV4 that had preformed a touch and go behind the helicopter then over flew the helicopter on the upwind.

Narrative: Experimental RV4 flew straight in to S50 making only a single radio call ('Final 34; touch and go; helicopter in pattern say position'). Proceeded to enter the traffic pattern by flying directly over the runway south to north over slower departing traffic; without having the traffic in sight; and turning crosswind in front of that traffic. Since we were able; we slowed and stopped climbing (an airplane would have had to slow below stall speed). After landing; the RV4 took off again; passed downwind traffic at a higher rate of speed and descended in front of them to enter a base turn and land again (once again requiring us to slow to <50 KIAS). S50 is used for flight training by multiple flight schools; and non-standard traffic pattern entries by general aviation traffic puts all pilots here at risk for MAC. This risk is heightened when low-experience instructors; low-time students; or solo students encounter this erratic behavior. Auburn and the area between S50 and BFI are due for a MAC between airplane traffic not using the CTAF; not reporting or coordinating with other traffic; flying at a higher rate of speed than flight training aircraft; and at low altitudes.

Data retrieved from NASA's ASRS site as of July 2013 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	1078338
Time
Date	201304
Place
Locale Reference	S50.Airport
State Reference	WA
Environment
Flight Conditions	Marginal
Light	Daylight
Aircraft 1
Make Model Name	Helicopter
Operating Under FAR Part	Part 91
Flight Phase	Climb
Aircraft 2
Make Model Name	RV-4
Operating Under FAR Part	Part 91
Flight Phase	Initial Approach
Person 1
Function	Instructor
Qualification	Flight Crew Commercial Flight Crew Flight Instructor
Experience	Flight Crew Last 90 Days 199 Flight Crew Total 1084 Flight Crew Type 980
Events
Anomaly	Conflict NMAC

Helicopter instructor pilot reports a near midair collision with a RV4 that had preformed a touch and go behind the helicopter then over flew the helicopter on the upwind.