HELP certification of light a/c engine change
 

Hi all,
I am searching for information on the processes involved in re-certification of a light a/c with an aero-diesel engine installed in place of a piston engine, as part of my final year project.
This would be carried out for MAF (Mission Aviation Fellowship) a/c operating in E-Africa.

For example:

1 There are a few instrument and control changes to be made in the cockpit

2 The MTOW may change

Any advice or contact info would be very much appreciated - I am unsure if it is the CAA (JAA) only who have control over a/c in that part of the world?

Thank-You

Lady Heath

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).]

If its's going on an east african register,
they work fairly closely with the UK CAA.
So it's likely that UK regulations will have to be met.

If this is an practical, rather than academic exercise, then you have received very sound advice here already.

I can't imagine undertaking a major recertification project for a product of US origin outside the FAA system; for reasons of cost and practicality. The reason for this, is the simplicity of the system and the cost effectiveness of access to individual FAA designees for every discipline required for the complete certification package.

The aero-diesel engines that are currently in test, will never be a viable proposition until they have recieved certification for the entire package to be installed in the aircraft, essentially as a turn-key modification. Unless there is potentially a large production run to absorb the certification costs, a mod of this nature is (generally) prohibitively expensive. This indicates that the initial installation efforts will be aimed at models with large fleet numbers, and particularly commercial and training operators.

I have been involved in a large number of mods including re-engining piston and turboprop aircraft and some very big helicopter programmes. The initial planning and co-ordination between the engineers performing the certification functions and the certifying agency is perhaps the most important part of the whole project.

If this were to be an academic exercise, then it is worth looking closely at the FAA system, as all the data you could require is available on the Internet (FAR's, Advisory Circulars, etc).

Not an insurmountable problem, simply an expensive one!

Well, this sounds like rocket science to me, i.e. very complicated but I still would like to ask a question that might cost me.
There are rumours that AVGAS 100LL will not be available as of 2004/2005, what then? The low compression, low power engines will be able to fly on water but what about the high power engines like the IO540, IO550 etc? What about the Turbo engines? The world-wide GA fleet will be grounded within a day.
I know that Continental and a French company are in process of developing Diesel engines. The French should get the FAA approval this year while Continental is well behind. The engines are rated at 200, 235 and 250 HP, yet a very small segment of the market.


[This message has been edited by AC-DC (edited 29 January 2001).]

Gentlemen,

Thank-you very much for the advice esp Genghis :)

AC-DC - Yes there are rumours of avgas running out, in fact in some remote areas of the world, esp the African bush in which MAF operate, avgas is not available whereas diesel fuel is. This is the main driving factor behind the production of aero-diesels. These diesel engines have many advantages over the current piston engines which are using 1930's technology, the main advantage being the 30% reduction in fuel consumption. With diesel fuel being cheaper as well, the cost savings are very attractive :)

There are currently 7 manufacturers of diesel engines for light aircraft and my project involves a performance comparison of these against the piston engine on certain aircraft.

Lady Heath


[This message has been edited by Lady Heath (edited 29 January 2001).]

I think that the new engines will use JETA1 not diesel.

Cyclic hotline makes a good point about FAA certification. MAF would probably be better off soldiering on with the avgas guzzlers until Cessna or similar start producing a diesel engined production aircraft. I do not think this is that far away. At least then you will get a new airframe as well as the engine.
The cost of mods to CAA standards has to be seen to be believed. In the early 80's a simple long range tank installation which already had an FAA STC cost over £5000 to certify. Those index linked pensions have to be paid for somehow!!!!!!!!!!!!!

AC-DC

Aero-Diesel engines such as the ones being developed by Wilksch Airmotive and Deltahawk can run on JetA, JetA1, JP5, JP8, Diesel 1 and Diesel 2

These fuels are all kerosene based and part of the same family. The fuel system is designed so that Jet fuel and diesel can also be mixed in the fuel tank when changing fuels.

There exists a fuel recirculation system which warms the fuel and fuel filter so that water precipitates out in cold weather.

:)

Lady Heath

Lady H.
Can you give us a quick review of the market/development situation?
I was aware of only 3 companies in the business. If AVGAS will not be available as of 2004/2005 many people will find themselves with obsolete power plants.
My engine is just over 2500h (500 over TBO) and according to the latest checks can run another 500h to 3000h if all is fine, that means another 5 years.
I don't like to pay £17k for an engine and use it as paperweight after 6 months (the desk might break), a point that many should think about.
Thanks

AC-DC

The market/development situation for these engines are as follows:

1 SMA-Morane-Renault have stated that production should start in 2001, the engines are fully developed but certification process is still ongoing and pricing has not been fixed. They will be looking for opertators who do a lot of hrs each yr and who are prepared to help with further testing of engines under actual operating conditions (flt schools or freight operators) - MAF would be ideal in this case as they are seeking those working in difficult conditions such as extreme hot or sold climates.

2 Wilksch Airmotive (UK) - http://www.wilksch.com have taken deposits for 2001 production bookings - they want to gain experience in the homebuilt market (e.g the PFA) before tackling certification in order to have something far better and more thoroughly tested than regulations require.

3 Diesel Air (UK) http://www.dair.co.uk have no date for production but have stated that the public category engines will have to be replaced with zero-timed engines at TBO - initially recommending 1000hrs between strip and interval but hope to achieve 3000 hrs TBO eventually

4 Teledyne Continental (NASA) http://www.tcmlink.com/about/briefs.html have stated their engines will be available for production in 2003

5 Textron Lycomming & Detroit diesel http://www.lycoming.textron.com/pres...diesel_jv.html claimed that (after contact) additional development and improvement is needed.

6 Deltahawk http://www.deltahawkengines.com will start production in 2003

7 Zoche http://www.zoche.de/diesels.htm will start production in 2003

The main problem facing the manufacturers is that of certification this is because of the lack of any magnetos or spark plugs. The FAA are working closely with JAA to write new regulations to cover these engines with no ignition system and with ECUs as well as the single lever control.

The initial price will be expensive and the TBO low until experience is gained which can take years. This is a risk that MAF may not want to take as the piston engines they are currently operating have well proven reliability.

Hi there
Have you seen the Opel-based diesel,with a turbo,fitted to a small,two-seat composite homebuilt.It was built in France and attended the PFA Rally last year.Apparently,the Wilkisch people were a tad miffed at the whole simplicity of the set-up.
Lady Heath,perhaps those who need to certify single-lever operation should refer to the FW190 and see how the BMW engine was set up.
regards
TDD

L.H
You put the smile back on my face. I will have to o/h or replace around 2005. I hope that the diesel engines will be ready by then.
Thanks for your reply.

The Slingsby T67M260 Firefly has single lever operation on a Lycoming, might be worth finding out what the certification basis was for that.

G