Scratch building

[asherrockhome]

I'm looking at some point in the future of scratch building an aircraft, and I've been looking though all the legal stuff around it and haven't really been able to find some clear info. Would anyone be able to tell me anything about licenses required, where and when it could be flown, weight and size limits etc. Any info would be helpful.

Cheers!

[Peter Lewis]

Ask Bruce Cooke.

[madmac]

The SAA website FAQ is a good place to start

saa.org.nz/aircraft-building/faq/

There is also the RAANZ website
raanz.org.nz/wiki/pmwiki.php

[asherrockhome]

Feb 22, 2021 8:18:31 GMT 12 madmac said:

The SAA website FAQ is a good place to start

saa.org.nz/aircraft-building/faq/

There is also the RAANZ website
raanz.org.nz/wiki/pmwiki.php

thanks for that

[Bruce]

Hi asherrockhome,
I'm the Vice president of SAA and I have also designed and built my own aircraft. I assume when you refer to "scratch building" youu are meaning your own design, as many amateur built aircraft can be built from scratch from purchased plan sets.
In New Zealand we have a very simple and permissive set of rules for building aircraft. There are two main streams you can go down and they both have common stages anyway. If the aircraft is under 600kg and stalls below 45kts you can consider it a microlight, or, for heavier aircraft, it comes under Special Category. Amateur built aircraft all start out as "Special Category - Experimental" during the flight testing phase, then become "Special category - Amateur Built" once this is completed. Dont confuse this with American terms such as "experimental" and "Light Sport". Microlights only require a Microlight certificate to fly, Special Category require at least an RPL / PPL.
You can essentially build anything you like in the Special category, so long as it conforms to best aircraft practice. The builder takes all responsibility for the structural safety and handling, and its airworthiness is confirmed by demonstration and the flight test programme. You do not have to have the design checked by an engineer or approved in any way - its all at builders risk. CAA will issue a certificate of Airworthiness based on this, and impose restrictions as required to ensure the safety of 3rd parties. For own - designs, this means no flight over populated areas.
The flight testing of an own-design is critical. the test pilot will need approval and CAA has guidance on this. You will need to provide a test programme which will sufficiently define the operating limitations and demonstrate the safety of the aircraft. this is more complex than testing a known type such as a kit aircraft, where testing essentially just determines that the aircraft behaves within the the existing flight limitations. testing an own design actually has to define those limits, and there is a degree of added danger to this. Once testing is complete, the permanent "Special category - experimental" airworthiness certificate is issued, and the design is effectively "frozen". Major changes after this point are documented as modifications and further test flying may be required.
A strong word of warning however!...From my own experience I can advise that building your own design is very difficult and I do not recommend it unless you are ready for an extreme challenge and have a very valid, specific reason to do so. Do not underestimate the difficulty! In NZ, only 5 or 6 such aircraft have flown in the last 20 years. The most successful have been derived closely from existing designs. Those "clean sheet" designs such as mine, have often proven to be somewhat disappointing due to compromises that are required in the design process. Invariably own-design aircraft come out heavy, as it is almost impossible to accurately estimate the weight of most structural components, and the tendency is to over-build to provide a safety margin. the result is disappointing performance or operational limitations. It is certainly not any cheaper than building from existing plans, and the emotional strain is quite hard - especially if / when it fails to perform quite as expected. You really also need aviation engineering experience to understand why things need to be done a specific way, it definitely is not something an inexperienced aircraft builder should be attempting. To overcome the many challenges and successfully build an own design is extremely rewarding, but be prepared for the cost - in many forms. My project motto was "If it was supposed to be easy, everyone would be doing it".
In summary, yes, our regulatory environment makes it very easy to build an own design aircraft in New Zealand, but thats the easy bit in a very difficult undertaking. Go in with your eyes open.

[asherrockhome]

thanks, that's quite helpful, off I don't currently have any of the expertise to do so, nor the money required, but it just more of a thought of 'could it be done'.

[Dave Homewood]

It can be done, and the Sport Aircraft Association people, like Bruce, are the ones who can advise and help.