My understanding of Part 91 (.409) for not "large" aircraft, is that multi-engine turbines, but not turbine singles, are required to abide by manufacturers' calendar as well as hourly limits, correct? Not a problem for 500 hour a year corporate owners, but when age brings those planes within reach of a a 100-hour a year individual, that means that the cost of those items accrues much faster for a twin turbine than a single. For example, a "3,000 hours or 5 years" item costing $15K would add $5 per flight hour for the single but effectively $30/hr. for the twin. And even the hourly limits are advisory, not regulatory, under Part 91 for a single turbine, IIReadingCorrectly.

Thats the way I understand it, and it's a real shame. It effectively puts a lot of decent older King Airs out of the reach of the 100 hour per year owner flown crowd.

There are some twins that don't have such drastic calendar requirements such as the MU-2. Furthermore there is some wording in the regs on twin turbine maintenance that states something along the lines of "maintain according to manufacturers specs or other program acceptable to the administrator", so you could always in theory get an alternate maintenance program approved by the administrator, but I wouldn't hold my breath.

There are also some interesting debates about twin turbine maintenance in regards to piston twins converted to turbine power. Does compliance with the original maintenance manual then become a regulatory requirement, or must you comply with the requirements of whoever did the conversion? I would assume that in such a case, like the Royal Turbine Duke, the maintenance regs would be set by STC holder but I could be wrong.

That's an interesting point. Bonanza and Baron have many "mandatory" items, like the wing attach bolts, that are widely ignored as useless in Part 91. If somebody does a turbine conversion Baron, do those things having nothing to do with the new engines suddenly all become mandatory? Or can the holder of the STC that puts on the new turbine engines decide to delete those "mandatory" requirements?

Can of worms, indeed.

Correct, BUT...

Read 91.409's various clauses carefully. Most people just accept the default manufacturer's program as spelled out in 91.409(f)(3). But you can go get your own maintenance program approved and use it under 91.409(f)(4). Now, the FSDO has to approve it, so you can't just say something like you'll never do maintenance, it'd have to be based on some kind of realistic logic. But people have been able to get modified calendar times and such that are justifiable.

Is there some obvious reason nobody has STC an alternate maintenance program foot king airs? Maybe something more like the mu2 program- geared towards lower utilization?

What is the incentive to spend the money to develop such a program? Further, Beech is not likely to share data with you, that means extensive R&D to build the data required....

Tim

What is the incentive to spend the money to develop such a program? Further, Beech is not likely to share data with you, that means extensive R&D to build the data required....

Tim

I think its a growing market since the airframe values are getting low enough to make them attractive to low utilization owners. It would take a really sharp DER (or a team of them) who already enjoys a very good relationship with the FAA to pull it off without digging a huge financial hole. Good luck to whoever tries it.

I have been wondering if NEXTANT is going to STC a new maintenance program to address this with its C90 refurb.

If you could could do it as a standalone STC it seems like it would breath economic life back into many older KA air frames.

There is a low utilization program built into the phase program for the less than 100hr/yr club. The mx is the same just deferred slightly. The first year is an Interim inspection which takes about 6 hours to do (mostly functional tests and exterior visuals), the second year you do a complete, which is all 4 phases at once.

I don't think that program will help your $/hr cost but would probsbly be calculated as more of a fixed cost.