Canada has DADs (delegates within a DAO) and DARs (independent delegates, or "one man DAO").

another day in paradise, or is paradise one day closer ?

An ODA is generally an organization rather than a single person, and will often times have even more authority to approve engineering data. Some ODAs have the authority granted to approve STCs. So depending on the type of change people want, an ODA can be beneficial.

You can see the current list of FAA designated ODAs here: https://www.faa.gov/other_visit/aviation_industry/...

Definition and background info:
https://www.faa.gov/other_visit/aviation_industry/....

These are generally bigger companies with large staff and proven track record.

Usually for something like an STC there are a couple different routes. You can have it designed and substantiated by one or several engineering groups, who prepare the total package, and then send it to an FAA ACO for approval. Or you might use an ODA who have approval authority and can usually design and substantiate in-house. But the second option might cost more.

Keep em' Flying
//Fight Corrosion!

For Canada's engineering delegation rules:
https://tc.canada.ca/en/corporate-services/acts-re...

Let me start by offering you a generic catch-all term that isn't accurate but allows you to speak to others in Canada and they'll understand you: we call each other "delegates" because we have been delegated some authority by Transport Canada.

RB1957 is correct, Canada does not use the same terminology as the FAA or EASA. There are also differences in scope and meaning of some responsibilities, that can be subtle at times. My nitpick about what RB said: A Canadian DOA can manage its delegates as it chooses as long as it's in line with the regulations I posted above. One company may call them "DAD=Design Approval Delegate" another may call them "AP=Authorized Person" and another may call them "UM=Unit Member" (which borrows from the FAA terminology for ODA's).

Quote:

So today, I would like to understand what could bring an aircraft/rotorcraft operator to contract an ODA instead of DER-T for the certification of a modification ?

One distinguishing factor is scope of the project.
If you need to swap the audio panel from the original installed by the OEM to another TSO'd unit, then a DAR can help you with a wiring diagram and an few test plans.
On the other hand, if you want to replace the primary displays from the antiquated cathode-ray tubes to LCD types, then the project is going to need a lot of designers and engineers to integrate a huge number of systems, and one DAR alone isn't going to get you to the finish line.

You could transpose the same logic into the USA, using a DER for a small-scope project and an ODA for a larger project. In Europe, I think there aren't any indpendents any more, so you don't have the choice. Other things are broken in the EU system, and many EU aircraft operators get their mod work done in Canada or the USA.

Also note that many DAO/ODA will contract independent DAR/DER as needed with specific skills to fill gaps on a project here and there.

Among these organizations (DAO / ODA / DOA) the composition of the company matters, too. It is possible for several delegated engineers to work together as an organization but not have any employees and work entirely as consultants. That would make them a lot like independent DAR/DERs. In other organizations, the DAO may be just a part of the larger engineering department, employing many other engineers and technicians, or an airline operator. Such an organization would have much more ability to do complicated projects, but if you ask them to do a simple part swap, they may turn the work down because it's not worth their time.

I will attempt to provide useful information, but keep in mind my experience with the national authorities is primarily in the US (FAA only) and on aircraft in the Part 25 Transport Aircraft category, typically operated by an airline organization. I work for an ODA and hold some delegations as a Unit Member under our ODA. Almost every project we take on is an STC program. Our ODA has delegated authority to issue an STC and also to issue FAA-PMA.

The reason most other posters are stating (correctly) that an ODA is normally contracted for projects of a larger scope is the range of capability typically available in an ODA. A typical ODA like ours will often have either on staff or under contract persons with either DER or UM delegations for:

1. Structures engineering
2. Systems and Equipment - Mechanical
3. Systems and Equipment - Electrical
4. Flight Test
5. Inspection

The first four are the major engineering disciplines. Some of them also have sub-disciplines that are quite specialized and often treated somewhat like a separate discipline such as flammability, fatigue analysis, cabin interior safety, noise abatement, functional hazard assessment, etc.

The fifth is the inspection discipline that conforms the prototype parts and the prototype installation, and can issue the experimental certificate for flight test.

Not sure if this provides any useful information for you but feel free to ask questions if you need more clarification.

Dear All,

I would like to thank you for all you answers which help me to better understand the design organisation differences.
So, the main reason for an operator to call a DOA/ODA is mainly dependant of the "size" of the project.

The size of the project is defined by the criticity of the system (avionic for exemple) installed (Classification).
In DOA world (Europe), depending of the classification of the modifification (Major, Minor) you have the possibility to perform the modification by your own, which mean that the DOA is able to provide the entire package and deliver the approval without the involvement of the authority (EASA). But if the modification is considered as Major, the EASA will automatically be involved (depending of LOI- Level of Involvement).

How does it work it TCCA world ? And in FAA world ?

I heard that in TCCA world all modification were supposed to be performed with the involvement of the TCCA (Equivalent to Major for EASA). I don't know if TCCA have the same way to classify modifications the same way than in Europe. Do you confirm ?

I think that it is a very interested topics, thank you again for your participation.

In Canada the dividing lines are quite different from Europe. And the same words are used differently.

In Canada we permit different authority to the mechanics (AME) who are licensed to maintain the airworthiness of the aircraft by signing the maintenance logbook. While that part is not too different from Europe, the scope of control that an AME in Canada or USA has is greater than in Europe. A licensed AME in Canada can sign for maintenance work done on an aircraft using approved data (by the DAR/DAO/TCCA) or acceptable data (by the aircraft OEM, usually or published guidance from Transport Canada) or specified data (by the equipment manufacturer, usually).

From that, the AME has control over many modification programs, and can determine if the scope is minor (and can be done using acceptable data) or if the change is major, meaning approved data must be used. Once they make that choice, then a DAR/DAO should be involved. In practice, a licensed AME is usually consulted only when the proposed change is relatively limited, to one aircraft or one piece of equipment. When the modification is more complex, people don't usually bother with the minor/major distinction because it becomes obvious that approved data will be needed. That said, I find that a licensed AME is an valuable stakeholder in a modification project, since they have to sign out the installation after the design is done. Never forget that the boffins in the engineering department can only approve a design. The installation is always signed out by a licensee.

Some DAR's and DAO's in Canada will assist with preparing designs that only use acceptable data, as a service to organize the documents for the licensed AME. We're good with paperwork, here in the engineering department, you see, and we draw good too.

The level of involvement in the Canadian context is a project-by-project decision, and it is made by TC when we present them with a certification plan. I don't know if Europe is the same.

You know, you can learn all this stuff (and lots more) in a course given by Transport Canada every year, often twice per year. The last one was in April, so maybe you only have to wait until autumn for the next.

https://tc.canada.ca/en/aviation/aircraft-airworth...