Date: 201306
Local time of day: 0601-1200
Location: VNY.Airport, CA
Flight conditions: IMC
Weather elements / visibility: Turbulence; 5
Light: Daylight
Aircraft: Gulfstream II (G1159)
Operator: Fractional
Operating under: Part 91
Flight plan: IFR
Mission: Ferry / Re-Positioning
Flight phase: Final Approach
Airspace: Class D VNY
ATC / advisory: TRACON SCT
Reporter organization: Fractional
Reporter function: First Officer; Pilot Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Flight Instructor
Human factors: Communication Breakdown; Confusion; Situational Awareness
Anomaly: Deviation - Altitude Crossing Restriction Not Met; Deviation - Altitude Excursion From Assigned Altitude; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter CFTT / CFIT
Detector: Automation Aircraft Terrain Warning
When detected: In-flight
Result: Flight Crew Became Reoriented; Flight Crew Took Evasive Action
Contributing factors: Human Factors
Primary problem: Human Factors

Narrative: This was a Part 91 positioning leg; so the Captain gave me this empty leg to VNY. A weather system had moved into the western region and ATC had given us a number of heading a speed changes as we descended into VNY. During this time the Captain (Pilot Not Flying) had setup the FMS for the VOR/DME or GPS-B approach into VNY. At this point we were Flaps 20 and the Approach in Range Checklist had been completed. ATC gave us a vector onto the approach; instructed us to descend and maintain 4;900 [FT] and cleared us for the approach. I called for the Gear Down Before Landing Checklist. At that time I had the autopilot engaged as we were encountering turbulence and IMC. About 200 FT before our assigned altitude; I looked to confirm that the autopilot was about to capture; but the altitude select (ALT SEL) had kicked off. I pressed ALT SEL again but it would not engage. I disconnected the autopilot and called autopilot disengaged and maintained 4;900 and was hand flying the approach. The Captain (pilot not flying) was finishing the Gear Down Before Landing Checklist. The Captain (pilot not flying) bugged 3;400 [FT] and I began a descent. After leveling off I asked how far to the final approach fix. He did not respond. I asked again he did not respond as he was busy with his duty. Finally I ask him what was our next altitude he said 2;500 and I asked if we were clear to descend and I thought I heard; 'Yes.' I began a descent to 2;500 and we broke out of IMC around 3;300 and realized we descended just before the final approach fix. We received a terrain warning and immediately initiated a climb back to 3;400. We were in VMC during the climb and were able to maintain visual separation; so we requested a visual approach to the airport. Once we were on the ground we discussed our breakdown in communication and situational awareness. We discussed the event with our Chief Pilot and I have also reviewed our company's Standard Operating Procedures for non precision approaches.




Synopsis: G1159 First Officer reports descending early on the VOR DME or GPS-B approach to VNY; resulting in an EGPWS terrain warning.