The following is only my opinion so please take it as such since I am not a lawyer. It depends is the correct answer. I presume that you will be operating under part 135. Does the companies ops specs require a SIC in the C90 for these trips? If so then yes you can log it. It the SIC is other there because of insurance requirements (or whatever) then I might be dubious about logging that time. We need a little more info from you before we can be certain. There are many good discussions about this very topic here if you do a search for logging SIC time or something along those lines you will find much useful information. Hope it helps.
I agree with the above. I assume this is a real job and am assuming, too, that this is 135. Absent these conditions, you cannot log all the time but you can log only the time that you are actually flying the airplane AS SOLE MANIPULATOR of the controls as multi, turbine, PIC, night and whatever. You cannot log the time that you are warming the right seat while the other pilot flies. The FARs and not insurance control.
I was in your shoes a few years ago when I was hired by a group flying a C-90 part 91. There inshurance did require 2 pilots but I was still unsure how to log time in this aircraft as it is a single pilot airplane. To add insult to injury they did not give me any formal traing so all I recieved way my 3 takeoff and landings.
It is my understanding that reguardless of insurance requirements there is no legal sic time that you can log. 91 or 135. From talking to my 135 friends in similar situation, they were told to sit there with their hands in there lap when on 135 legs, but were allowed to particapate on 91 legs. You can as a multi commercial pilot log pic time any time you are actually flying. Part 91 flights only, if you have your 3 take off's and landings.
Having said that, I have addvised people to use their log books to try and paint a picture for any prospective interviewer. So for example if you show up and have 500 pic in the aircraft, no formal training or sign off it raises questions if you try and pass your self off as the captian of the aircraft. If you have 250 pic and 250 as sic or other, to me it paints a better picture of your actual role at the job.
Having said that, if you are going to the airlines they could care less about any thing but pic time requardless of the reason. But if your going to be corperate sometimes this other time can be applied towards total time in type.
This may or may not be right but its how we do it.
Our company ops specs do not require a SIC be on board however it is an Insurance requirement and also a company policy so all people who fly in the right seat whether it be the C90B, B100, B200 are given the formal ground school, flight training, and SIC check ride even though the ops specs says we don't require one..... BUT just because we have SIC authorization does not allow us to log SIC time, the only thing it allows us to do is the fly the 135 legs "legally" since we are now authorized to manipulate the flight controls under part 135.
Be very very careful with regards to how you are logging flight time while in the right seat since its the ops specs that are dictating whether a SIC is required NOT the insurance reqt's. Most airlines are going to laugh if they see SIC time in a C90......
If you are acting as PIC on the part 91 legs then you can log PIC, multi, and turbine time- On the part 135 legs IF you are not required on board as a SIC I probably would have the PIC endorse your log book as "dual received" as long as he/she is a MEI or ATP since this is probably the only "legal" way for you to log the flight time. As the other post said you need to "paint" a picture of yourself and be able to justify your actions to a flight department one day down the line as to "why" and "how" you were logging turbine time...
May be another way to log the 135 legs BUT dunno if it would be "legal"- this is just how we do things
Here's another perspective: I have worked as DO with several 135 operations and in all cases, an SIC was required for any IFR operation unless the aircraft had a functioning autopilot, and the PIC had successfully demonstrated on his FAA check ride that he was capable of using the A/P "in lieu of an SIC" and that authorization was noted in his record. The POI also informed me that even then the PIC had the option of using the A/P in lieu of an SIC or using an SIC. The SIC also needs the check ride with the FAA and appropriate ratings. One new startup that I worked , drafting the manuals etc., on which I was to be the DO, (I no longer had any desire to be a charter pilot), I took the SIC ride so that operations could be conducted when A/P was inop. Unfortunately on the ride, PIC in left seat, me in right acting as SIC, PIO behind us, the PIC was busting an NDB approach, I reached over and pointed to ADF needle to warn the PIC; a little later on a single-engine circle-to-land he was about to bust an altitude, and I tapped on the altimeter. In short - he passed his check ride but the POI said he would've busted it if he hadn't had an SIC and wouldn't give the A/P in lieu authorization.
Reuslt: I had to ride along until his next check ride, and I did log the SIC time as well as PIC for time "manipulating'.