Scheduled Duty Period  

Twelve scheduled consecutive hours that my be continued to 14 hours

Duty Assignment           

A revenue flight which may contain multiple legs planned to be completed during the scheduled duty period

that has nothing to do with flight and rest time. it could say 500 hours and it wouldn't make any difference. try again. lol

that should be in the employee handbook, not a gom. the FAA could not possibly care less how long your shift is. it could say 15 minutes or a million hours. the FAA does not regulate the length of your shift, only the flight time and rest. your company could say you're on duty until a week from tuesday but if they want you to fly, they need to send you home for 10 hours. this is so not complicated if you have an IQ higher than room temperture. This did not come from a gom.

Duty period

Duty period means the period of elapsed time between reporting for an assignment involving flight time and release from that assignment by the certificate holder. The time is calculated using either Coordinated Universal Time or local time to reflect the total elapsed time.

Since the time after 14 hours does not require flight time (have you have been released from the assignment involving flight time? I say yes), you may work beyond the duty period so long as it does not involve flight time but you must get the required 10 hours uninterrupted rest before the next duty period. 

§ 135.261 Applicability.

Sections 135.263 through 135.273 of this part prescribe flight time limitations, duty period limitations, and rest requirements for operations conducted under this part as follows:

(e)( Section 135.273 prescribes duty period limitations and rest requirements for flight attendants in all operations conducted under this part.

§ 135.273 Duty period limitations and rest time requirements.

Assign you report to that could include part 135 flight duties. 

FAR 135.267 limits your duty period to 14 hours if you are on a regularly assigned schedule that doesn't change.  Can't think of ANY operation (except maybe Gas and Oil work, a slim maybe) that uses such a schedule!   Nobody in HAA/HEMS does since virtually ALL schedules go from day to night weekly.   That sort of schedule demands (by FAR) the use of 135.267(b)&(d), not 135.267(c).

Your GOM will specifically tell you if you are using 135.267(b) & (d), or 135 267(c).

12 hour duty periods that are a "regularly" and "normally" assigned schedule according to  the FAA. Your point is wrong again mr Maaaayorrrrs

You are not on a regurlarly assigned flight schedule.   The FAA made that clear in a 2017 legal intepretation to Moody-Seven Bar Aviation:

The FAA allows infrequent deviations from a regularly assigned work schedule conducted under§ 135.267(c). However, "iftbe pilot's schedule has intermittent periods where the duty time fluctuates from day to day or week to week, the operator is not maintaining a regular work pattern." In such case, the operation should be conducted under§ 135.267(b). Therefore we must stress that if the flight crew's duty time fluctuates on a regular basis, it would not be able to operate under 135.267(c). See Legal Interpretation to Doug Holee, from Donald Byrne, Acting Assistant Chief Counsel, Regulations and Enforcement Division (July 22, 1989).

https://www.faa.gov/about/office_org/headquarters_offices/agc/practice_areas/regulations/interpretations/Data/interps/2017/Moody-SevenBar_Aviation_2017_Legal_Interpretation.pdf

Additionally, it is not you who makes such decisions, it is your certificate holder.  And, they clearly determined themselves to be operating under 135.267(b) and (d), not (c).   Just look at your GOM (cited above) to confirm such important details!

Sounds like you are not on a regurlarly assigned duty schedule if you go from days to night in the middle of your "hitch" each week.

https://www.faa.gov/about/office_org/headquarters_offices/agc/practice_areas/regulations/interpretations/Data/interps/2013/New_2013_Legal_Interpretation.pdf

And, it makes perfect sense, if you understood why FAR 135.267(c) was even instituted.

... two reasons.   They had just started a new payroll system and it was easier for that computerized system to be set up if pilot's had a steady schedule in the bi-weekly pay cycle.   But, they also claimed that having every pilot on a "standard schedule" would make it easier to cover open shifts for sick callouts and vacation.   Their idea was that everyone would be starting/ending on common days, easing the effort to find coverage.

But, they also  said the FAA was on their back because the randomness of schedules made it difficult to track pilots duty periods.  This was not backed-up with any logical support, since the FAA deals with hundreds of operators who have random pilot schedules, including airlines where every line is different duty periods.

Well, at least that was the reasons the union's non-elected appointed trustee who never flew a day of HAA/HEMS in his entire career.

The duty period has not maximum.  Just that if you are going to operate an aircraft under Part 135, you must be able to show 10 hrs of rest (requred rest) before you plan to complete the flight time of that assignment (i.e., land by that time).  Your duty period can go far past that requirement, as long as you are not planning to fly.

We tend to think of it as a 14 hour maximum in practicality, but it isn't!   There is no requirement to end your actual duty period by the 14th hour.  

The FAA has consistently interpreted duty to mean "actual work for a certificate holder, or the present responsibility for work should the occasion arise."   Meaning, it is not rest!   Your rest starts once you no longer are on duty!   That's when you can start your rest timer for the required rest of 10 hours!

Yoh might think 2.22 should be in the employee handbooI, but the fact of the matter it is in the GOM. If you think the ops manual is optional, then you are a special kind of stupid. If you want to exceed your duty period then go ahead.

not everything you need to know is in the ops and manual, chief

assignment, not duty assignment.