VFR helicopter departure from bfi experienced near midair collision with high wing traffic that was ...

Attributes
ACN	839117
Time
Date	200906
Local Time Of Day	1201-1800
Place
Locale Reference	BFI.Airport
State Reference	WA
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	Helicopter
Operating Under FAR Part	Part 91
Flight Phase	Climb
Route In Use	Other Departure
Flight Plan	VFR
Aircraft 2
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Flight Phase	Final Approach
Route In Use	Visual Approach
Person 1
Function	Single Pilot Pilot Flying
Qualification	Flight Crew Instrument Flight Crew Multiengine Flight Crew Flight Instructor Flight Crew Air Transport Pilot (ATP)
Experience	Flight Crew Last 90 Days 150 Flight Crew Total 14000 Flight Crew Type 300
Events
Anomaly	Conflict NMAC
Miss Distance	Horizontal 200 Vertical 200

Narrative:

I was making a west departure from boeing field seattle VFR. The base of the overlying seattle class B is 1100 ft. The west departure route takes you over west seattle at low altitude. Tower called VFR traffic to me inbound from the west. Expecting an airplane at my 12 o'clock; I began a shallow descent so he would pass overhead. I was surprised to see a high wing airplane ahead and below me. I called tower and advised I had the traffic in sight and started a left hand climbing turn to avoid the other aircraft. He passed below and to my right. At no time did I fly into class B airspace. The west arrival and departure routes are published by boeing field tower and distributed locally. With a south flow aircraft pass to the north of the west seattle reservoir westbound. Due to the class B airspace overhead the airspace is compressed and conflicts can be rather common. Vigilance is required. I expected the airplane to pass overhead and was surprised that he may have been trying to pass underneath me. It is common for helicopter pilots to assume that airplanes will stay high and above helicopter operations. One cannot always assume that airplanes will remain in higher patterns especially when the airspace is compressed vertically.

Original NASA ASRS Text

Title: VFR helicopter departure from BFI experienced NMAC with high wing traffic that was issued traffic by ATC; reporter citing overhead Class B airspace and compressed VFR routes as contributory.

Narrative: I was making a west departure from Boeing Field Seattle VFR. The base of the overlying Seattle Class B is 1100 FT. The west departure route takes you over West Seattle at low altitude. Tower called VFR traffic to me inbound from the west. Expecting an airplane at my 12 o'clock; I began a shallow descent so he would pass overhead. I was surprised to see a high wing airplane ahead and below me. I called Tower and advised I had the traffic in sight and started a left hand climbing turn to avoid the other aircraft. He passed below and to my right. At no time did I fly into Class B airspace. The west arrival and departure routes are published by Boeing Field Tower and distributed locally. With a south flow aircraft pass to the north of the West Seattle reservoir westbound. Due to the Class B airspace overhead the airspace is compressed and conflicts can be rather common. Vigilance is required. I expected the airplane to pass overhead and was surprised that he may have been trying to pass underneath me. It is common for helicopter pilots to assume that airplanes will stay high and above helicopter operations. One cannot always assume that airplanes will remain in higher patterns especially when the airspace is compressed vertically.

Data retrieved from NASA's ASRS site as of April 2012 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.

VFR helicopter departure from bfi experienced near midair collision with high wing traffic that was issued traffic by ATC; reporter citing overhead class B airspace and compressed VFR routes as contributory.