Statistical Analysis of Homebuilt Aircraft Engines

[Auburntsts]

Here's a quick data point. My engine is a Superior XP-360. I just looked up my info on the FAA site. They have it listed as AMA/EXPR.

Mine too. I have a BPE IO-540-X which is really a Lycoming IO-540-C4B5 with an uncertificated fuel injection system and a BPE data plate. In the database it's listed as AMA/EXPR and model UNKWN.

[martymayes]

Mine too. I have a BPE IO-540-X which is really a Lycoming IO-540-C4B5 with an uncertificated fuel injection system and a BPE data plate. In the database it's listed as AMA/EXPR and model UNKWN.

So is the problem with the FAA database fields? Are builders disclosing the nature of their experimental/unknown engine and the registry doesn't have the ability to enter that information so it defaults to AMA/EXPR and model UNKWN ??

[rwanttaja]

So is the problem with the FAA database fields? Are builders disclosing the nature of their experimental/unknown engine and the registry doesn't have the ability to enter that information so it defaults to AMA/EXPR and model UNKWN ??

The FAA database designates both engine make and model with a field that runs from 0 to 99999 (0 is none, and 99999 is the code for AMA/EXP). The 100,000 spaces are nowhere near fully occupied.

There might be a desire by some FAA types to not use up slots in the table with non-production-type engines. But there are a lot of production engines included as well.

I suspect it's a combination of laziness by the FAA/DARs and builders' desire to avoid AD traceability. If they issue an AD for a Continental O-200 and yours is officially "AMA/EXP", the FAA doesn't know it applies to you.

Ron Wanttaja

[Auburntsts]

So is the problem with the FAA database fields? Are builders disclosing the nature of their experimental/unknown engine and the registry doesn't have the ability to enter that information so it defaults to AMA/EXPR and model UNKWN ??

Well I can only speak for myself but my 8130 identified my motor as a Barrett Precision Engine IO-540-X and my AWC inspection was performed by a FSDO inspector who looked at it closely so nothing was hidden from him-- got a 40 hr Phase1 to prove it.

i can only assume Ron is on the right track with his answer.

[Anymouse]

So is the problem with the FAA database fields? Are builders disclosing the nature of their experimental/unknown engine and the registry doesn't have the ability to enter that information so it defaults to AMA/EXPR and model UNKWN ??

My Tango has been flying for just over 11 years. Quite frankly, I can't remember how I filled out the form, but I'm pretty sure I listed the engine as a Superior model.

I can only assume Ron is on the right track with his answer.

Me too!

[Frank Giger]

In the FAA's defense, we don't know how clunky their software is. This is an organization that still has forms with Ye Olde black carbon paper between sheets (!), and I can imagine the data entry stuff could well be the same one from 15 years ago in a DOS box.

Misplace the binder that has the ancient sheet of engine codes in it and "EXP OTHER" will do in a pinch.



Frank "Data Entry Monkey" Giger

[SamP]

Hi Ron and Frank,
Forgive me as I try to understand the dataset. As a very rough reliability factor, would you divide the "In compare AMA set" column by the "Registry" column?

If only there was a way to dive just a little deeper. I know some people in the VW community are adamant against shrink fit prop hubs. Comparing the reliability of the Aerovee to the GP might be a rough way of seeing if those fears are founded.

[rwanttaja]

Hi Ron and Frank,
Forgive me as I try to understand the dataset. As a very rough reliability factor, would you divide the "In compare AMA set" column by the "Registry" column?

No, the "In AMA Compare Set" column in the number of aircraft registered with "Ama/EXP" engines I was able to determine had a particular engine type. Nominally, one would divide the number of accidents involving that engine type by the "Total" column. The problem is, I don't really like doing that when the fleet size is partially based on an estimate. I do it in categories (e.g., Certified engines vs. auto engines, etc.) but hate to point fingers at any particular engine based on deriving the fleet size.

If only there was a way to dive just a little deeper. I know some people in the VW community are adamant against shrink fit prop hubs. Comparing the reliability of the Aerovee to the GP might be a rough way of seeing if those fears are founded.

Ultimately, that would be my goal, but specifics about the engine are not always provided. If the NTSB says "VW", there are a lot of possible sub-types.

Ron Wanttaja