Caravan Undifferentiated
Flight Crew Instrument; Flight Crew Multiengine; Flight Crew Commercial
Flight Crew Last 90 Days 85; Flight Crew Total 500; Flight Crew Type 120
Situational Awareness; Communication Breakdown; Fatigue
Conflict Ground Conflict; Less Severe; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter CFTT / CFIT
Air Traffic Control Issued Advisory / Alert; Flight Crew FLC complied w / Automation / Advisory
Airspace Structure; Human Factors
The Captain was pilot flying; I was pilot monitoring. The Captain began his initial climb out normally but within thirty seconds he attempted to gain more airspeed on climb most likely to achieve a shorter en route time. His airspeed was about ~140 KTS; [which is] much too far above the Caravan's recommended climb speed; which slowed the vertical speed down to only about ~200-300 feet per minute. I let him know that his climb rate was too slow but he assured me that it would be OK. He attempted to correct this with a slightly higher pitch attitude; however; it wasn't a large enough correction to fix the problem and it wasn't applied quickly enough. Within a few minutes after takeoff; approach advised us that we were below the minimum safe altitude for the sector and that we were getting far too close to a tall obstacle. I called on the radio that we were going to expedite the climb. We ended up avoiding the obstacle with enough safe altitude separation. I believe my Captain was tired or fatigued; as our shift began early in the morning and he seemed to act more lethargic than normal. I don't remember the specifics of the altitudes and exact location. To note; I had written the local time of the incident down; however; that may only be accurate to plus or minus one hour.
C208 First Officer reported a fatigued Captain's failure to maintain proper climb profile to reach safe altitude.