Date: 201505
Local time of day: 1201-1800
Location: ACK.Airport, MA
Flight conditions: IMC
Weather elements / visibility: Fog; 10
Light: Daylight
Aircraft: Small Transport; Low Wing; 2 Turboprop Eng
Operator: Air Carrier
Operating under: Part 135
Flight plan: IFR
Mission: Passenger
Flight phase: Initial Climb
Airspace: Class D ACK
ATC / advisory: Tower ACK
Reporter organization: Air Carrier
Reporter function: Pilot Flying; Captain
Reporter qualification: Flight Crew Commercial; Flight Crew Instrument; Flight Crew Multiengine
Human factors: Troubleshooting; Time Pressure; Situational Awareness; Distraction; Confusion; Workload; Communication Breakdown
Anomaly: ATC Issue All Types; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance
Detector: Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Issued New Clearance; Flight Crew Returned To Clearance; Flight Crew Took Evasive Action
Contributing factors: Human Factors; Procedure
Primary problem: Procedure

Narrative: As part of our takeoff clearance from runway 06 at Nantucket (ACK); tower issued us a left turn to 010.  While we were climbing out; tower again directed us to turn left to 010.  I was flying the leg; and initiated a left turn to 010 (around 400 feet MSL).  At this point; my first officer also placed his hands on the controls and began forcing the aircraft back to runway heading while demanding that we remain on runway heading until 800 feet MSL as stated in the obstacle departure procedure.  Because we were already IMC and I wasn't 100 percent sure that the tower controller's instruction overrode the Obstacle Departure Procedure (ODP); I told him to get off the controls while I turned back to 060.  While doing so; I asked the first officer to confirm with tower that they had given us a heading of 010; but he refused to do so and again stated the ODP runway heading requirements; so I made the radio call myself.  By the time tower confirmed that she did in fact want us to turn to 010; we had already reached 800 feet MSL so I began the turn to 010 again.  We continued the flight to our destination without further incident and debriefed on the ground. At the time; I was convinced that my first officer had been correct that an ODP took priority over a tower-issued heading that wasn't preceded by the words 'radar contact'; but as I researched the topic; I began to be less sure that was the case.  I decided to file this report since I'm now unsure which action would have been procedurally correct; and believe that while what we did was the safest with respect to obstacle clearance; it might not have been the correct IFR procedure.  I intend to continue researching the situation until I find a definitive answer.




Synopsis: A pilot departing ACK reports the Tower Controller told him to turn left to 010 heading. In doing so; the co-pilot then gets control of the aircraft and attempts to turn the aircraft to the runway heading because of the Obstacle Departure Procedure (ODP) 800 foot restriction. The pilot regains control of aircraft and turns to a heading of 010 and at that time the aircraft is at 800 feet. The pilot is not sure if the 010 heading should have been followed until he was at 800 feet; like the co-pilot was trying to do.