I applaud your efforts, and I always enjoy reading your posts here.
STC does seem to be a reasonable path, given me limited knowledge of that arena. I do know it would take a ton of time and money to get there.
Curious if there is any close analog that could give you an idea of the time and money required for STC certification? I don't believe anyone has ever STC'd an auto engine into a plane, but maybe one of the piston to turboprop conversion STCs would be give you an order-of-magnitude idea of how much time and money would be required (assuming the STC holders would be willing to give that info).
thanks, mostly get same annoying contrarians commenting-pontificating-opining on my posts about this.
. cost of a major stc can vary immensely, and can take hundreds of paths to show compliance. typically a DER will work to find quickest and cheapest method acceptable to FAA to demonstrate your atticle meets the certification basis, such as part 23. this is a huge part of the process in determining what cost will likely be....so one applicant that say uses tradional methods, such as physically bending wings using large hydraulic presses (destroying the sample aircraft in the process and hoping you don't need to repeat it with another plane) to show the wings don't fail under the load required, will cost more than applicant that uses computer analysis software to do the same.
the agreed upon or required methods of demonstrating your stuff must do to be certified is documented in a paper called a g1 issue paper or similar (it's essentially what you and faa agree must and how to do for certification), with that you then have a plan you can calculate what your budget ....but as with all budgets, you will go over it.
our initial G1 basis was a deal killer due to the faa required software and hardware analysis basis which would have cost well over $2M for different reasons even though we used well proven DELPHI GM computers and software modified for part 33 redundancy by the GM engineer that worked on the exact computers (EEC) we used....this was due to a 1980s policy written when such computers were being introduced in the automotive world and there was little known about reliability....When faa allowed other means of compliance about 4 ish years ago we restarted the project with current c172 design (2nd plane, the first being one developed by a FL company called quiet aviation).
Most such programs get the FAA to approve use of designated engineering reps (DER) that can approve parts or all of the data and compliance, rather than the applicant submitting it directly to faa, which can take way longer and not normally the method for most larger projects. DERs are essentially your personal faa rep that you pay directly so they work for you, but you may need different DERs for different specialties such as electrical, structural, software, ect. they are basically like a DPE and sign off on your testing (there also companies made up of different DERs that can handle the entire cert called ODA but typically much more $)...so you need a big budget and the GA ROI isn't likely to make investment sense, and thus, fewer applicants do bigger projects. an example would be EPS Diesel engine that was developing a clean sheet aircraft engine but went bankrupt after close to $60M invested...they succomed to a dark horse takeover by Chinese investor..their primary target was GA but also drone market. Red Hawk diesels have been at their STC for well over a decade and can only imagine what they have into it. at osh last year they estimated their c172 conversion would be about same as continental diesel conversion., about $105k. our v8 conversion would have been about $30-35k with far less operating costs, as comparison (we were not starting a new design, so time lines and cost were less than such a certified project, but exemplifies the high cost of bringing new things to ga market and many end up not making financial sense for most average GA owners).
there are other companies that have certified car engines, both certified diesels, for example, both of which went BK along the way and acquired thru BK sale to move on to certification which likely due to aquiring assets at fire sale prices. a Canadian company developed a V8 engine for installation on king airs and dehavulends turbo props touring cost and performance benefits..., I think name was something like Orlendo, that got stc certified, that also went BK (I seem to think they launched sales right after 911 when economies were in the tank) and later bought by a usa company and renamed Trace (or something similar). ..like many aero companies that take a long time to make such complicated stuff, the market and economy was bad when they were finally ready to sell it and the debt caught up, and they went away but not sure what ever happened to them. I think it was a TX company ...maybe some here knows and add comment. again, a new design from scratch cost a lot of $ and takes long time to reach market, but they did it and it was supposed to be a good refit option, but timing is everything.
when we restarted the c172 v8 project after part 23 rewrite with current design, we believed we could now show compliance without full software analysis and had a significant software DER that would advocate for our what's called equivalent level of safety finding.(elos)....this would have reduced our cert cost to what we could well afford without need for substantial outside investment, at least early on. with most of the work already done, and our inhouse ability with former DER and engineers and G1 paper, we tried working directly with faa cert office to reduce DER typical costs, but they made it clear over years they did not want it and did nothing, including taking years to respond to required written requests systemically.
I've out lined some of this on our website and done rehashing it. their latest now harassment came days from leaving for OSH last year when 2 faa inspectors were sent by Washington DC national office to try to revoke our AWC (they knew we were going to osh from our program letter and our plane draws a lot of attention, and it was this type of attention that put us on faa policy LEADERSHIP radar in the first place)..without getting into the technicaties of a multi purpose AWC..we argued the technicality and able to get new AWC from local FSDO and a couple of days later and local time-building CFIs flew it to OSH and camped under its wing for 4 days....we occasionally lend the plane out to local money strapped time builders and even let some train and do check rides in it (they buy their own gas). it's pretty cheap to own and fly and it needs to fly more than I have time to.... may put it into a local exp flying club that starting at a neighboring airport.
so to better try answer your question about cost, you see how figuring it is dependent on many levels. its more complicated as well in that it's just not having an article made and ready for certification, but you must also show the means it will be manufactured and tooling to do it....for example. we had to make our own engine mount...so we needed to first design it, show it meets structural requirements for twisting and G loading (through either actually physically bending it around or by soft ware process called finite element analysis, which is what we did.), and have a jig and process to make it....so not only do we need the mount, but the tooling to show we can make the same mount each time. our first few props were hand carved and reshaped with simple wood working tools to dial in the design for best performance and lower noise; we could not make the same exact prop for production so we sent all our flight testing data and specs of the final version of our hand carved prop to a certified prop company that was able to make it the same using a known and approved process to meet our FAA G1 requirement...props have their own type cert.
So I'm watering the process down here, but needless to say theres a lot of stuff that has to happen to even begin testing which must be budgeted for, and a lot of curve balls.
hope this somewhat answers your question and thanks for stating interest in my posts.
