Mutter, mutter, mutter - normally I'd charge large sums of money for this sort of advice, but since it's for a good cause (either creating a graduate who actually understands certification, or the MAF) I suppose I can offer a few words.
The approval of a modification to an aeroplane is the responsibility of the national authority in the country of registration, if it's an MAF aircraft then the odds are that this is either the CAA or FAA.
The standard against which the modification needs to be approved is likely to be FAR-23 if it's American registered, JAR-23 if it's under 10 years old and British Registered, or BCAR Section K if it's British and older than that. The manufacturer or authority will be able to tell you which - as (may) the POH.
It will be the responsibility of the "applicant" (presumably you) to produce clear documentary evidence that all relevant parts of the airworthiness standards are met and all parts and materials come from certified aviation sources. Obviously absolutely everything going on the aircraft needs to be clearly documented
The difficult part of this is likely to be the engine which must be certified if it is going on an aircraft with a C of A - if it's not then there's going to be a need for some serious negotiation with the CAA / FAA powerplant department but even then they'll probably say a very clear "NO".
Flight testing a new engine type is a very specialist job and you'll need to find a TP or FTE with the relevant specialist experience. In essence the following need to be addressed: -
- Lateral and normal g effects of fuel and oil systems.
- Basic reliability in the specific configuration
- Propeller matching
- LSS effects.
- Lat-dir effects.
- All the aircraft performance data will need repeating (the standard textbook on this is FAA AC23-8 but John Lowry's book "performance of light aircraft" is well with a look as well)
- Engine handling for documentation in the POH
- A new engine manual and servicing schedule needs appending to the POH / maintenance schedule.
Don't even think about trying to change the MTOW of a certified aircraft, it's not worth the trouble - if you really can't cope sell the aeroplane and buy something with a greater MTOW. However if the empty W&CG change (which is inevitable) then this is not a problem, just re-weigh the aeroplane and append a new W&CG report to the logbook.
In the UK, all the above would be dealt with by a competent E1 or JAR-21-JA approved company, with testing carried out under their F2 B-conditions, although for a one-off you might get F3 B-conditions to permit this in a non-approved company. (BCAR Section A part A8-9 covers this). In the USA, a company approval is not required, by an FAA permit to test (or whatever they call it) would be. Typical companies doing this sort of work commercially would be FRA, B-N, Marshalls, or DERA.
Then all the relevant reports are submitted to the authority, who will inevitably come back for more information first, but ultimately issue you with either an AAN (Airworthiness Approval Note - issued by UK CAA) or STC (Supplementary Type Certificate - issued by the FAA). The FAA don't, I believe, charge for this but the CAA charge £98/hour for their time, with a minimum charge of £296.
One the AAN / STC are issued, the aircraft's C of A is restored in the modified state, and the aircraft can then be used for the purpose intended.
If you asked me to do it, I'd probably estimate about £50 - £100,000 for the task, and 6 - 9 months. Having said that, the engine manufacturer may have a lot of data available to simplify this task, but in my experience suppliers of uncertified or new concept engines seem to have a very tenuous grasp of the requirements of certification.
Genghis CEng MRAeS
[This message has been edited by Genghis the Engineer (edited 28 January 2001).]