This crash is a mystery and may remain so. There are a few things that don't add up.
Based upon the information that the NTSB has published so far, I suspect they will come out with a probable cause of "Loss of control due to spatial disorientation due to continued VFR flight into IMC" or some variant thereof. It's looking that way at the moment.
There is no indication thus far of any mechanical malfunction. Of course, that doesn't mean that there wasn't a malfunction. One thing is for sure: Having a malfunction IMC in a helicopter in close proximity to terrain would be a serious situation.
My view is that the pilot never should have taken off in the first place. But having flown traffic watch in the wee hours around the San Francisco Bay Area, the word "marginal" gets interpreted pretty loosely if you want the broadcaster to be able to get their reports in. When the sun comes over the horizon and the ceiling drops, you start hearing a lot of special VFR requests. I think chopper pilots take a few liberties with that one due to the capability of their aircraft over the limitations of fixed wing.
But IMC is IMC for all. Therein lies the question: How did the pilot figure he was going to get all the way from John Wayne to Camarillo via 101 VFR in those conditions? Hope? We all know that in flying, hope is not a strategy. And I am really surprised that such an experienced pilot hoped for that. Maybe he knew something we didn't about the weather over there that morning.
The METAR on departure was 1000 feet overcast. Marginal right there. Burbank was IFR. Van Nuys 1000 overcast and then he was heading for the mountains. My daughter goes to college in Thousand Oaks, which is just to the East of Camarillo, which I fly into to visit coming down from the Bay Area. You drive up over a mountain pass between CMA and Thousand Oaks. Definitely over 1000'. It's mountains everywhere. Sure he might have been able to skirt around LA following the freeways (Which he did), but once West of Van Nuys, he had to climb. And climb he did.
The NTSB photo taken from a mountain top in the update report show cloud tops at approx. 2400 at the time and location of the accident. He flew past VNY at 1500, right at the cloud level the tower reported. When he was with SoCal he said he was going to climb through layers to 4000. Right at that point, if you look at the photo, you know he's deliberately gone VFR into IMC. So that was the big rules violation.
But as to why he crashed, well, it is still a mystery. He followed 101, climbed to 2300, then for an unknown reason, began a left turn. Then he started descending and by the time the turn had gone through 180 degrees, he was descending at 160 knots and 4000fpm into the mountain.
Why did he turn?
a) Maybe he figured that the VFR into IMC was a bad idea, that he would later get busted for it decided to come back, pretend he never went IMC and just land back at VNY and have the passengers driven the rest of the way.
b) Maybe he became spatially disorientated and lost control.
c) Maybe he had a mechanical problem, or an instrument problem during the climb and decided to turn back and try and get back down to VMC ASAP.
d) Maybe he experienced a serious medical problem.
We may never know the answer. As I said, I suspect the NTSB will probably go for (b). But I really do wonder about this. He was an experienced pilot, an IFR instructor. The year before he completed VFR into IMC and upset training in the helicopter satisfactorily. 8000 hours total time. 1000 in that make and model. 10 years with the company. And the helicopter had a four axis autopilot. He was following 101, he had a plan to go VFR into IMC (Against the rules, yes, but it was still a plan), he climbed and came oh so close to VFR on top at 2400, but only made it to 2300 before starting that left hand turn. He was probably only IMC for a minute or two. Plenty long enough for an inexperienced non-instrument pilot (let alone helicopter pilot) to lose control, but for a pilot with his qualifications and experience? I would be surprised if that was the cause.
But again, it's a mystery. All four reasons are quite plausible. The tragic part is that the pilot and aircraft were both qualified for flight in IMC conditions, but the operator was not. So he did not have the option of filing. And the passengers were not to know that of course.
Like many have said, the biggest mistake was the decision to take off in the first place. I suspect that would have crossed his mind as he was circling outside Burbank for 15 minutes, again when he flew past Van Nuys, and almost certainly as he began the climb towards the mountains.
Very sad. A lesson for all.