A version of this article first appeared in the March 2019 edition of our free newsletter, to subscribe click here
We are working with an established OEM on a significant aircraft engineering program (how’s that for honoring the NDA we have with our valued client?)
They have been allowed to use MMPDS-06 for their program. For those of you who do not know MMPDS is the commercial publication than follows on from where the now discontinued Mil-Handbook-5 left off.
I will omit my feelings about the removal of data from the public domain and the commercialization of what used to be freely available. You can guess what my feelings are.
The other problem that is becoming more and more pressing is the effect of the ‘sunset review’. For the uninitiated amongst us a sunset review is where the MMPDS consider data that reaches a certain age to be no longer valid with some confirmation.
Details can be found here: https://www.mmpds.org/sunset-review-for-joint-allowables/
In practise this sounds reasonable ish.
The result has been the large scale removal of fastener strength data from MMPDS. It is not clear that this fastener strength data has been shown to be inaccurate or invalid.
There is an in depth analysis of reasons for potential inaccuracies http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.545.9914&rep=rep1&type=pdf
I have no reason to believe the conclusions drawn regarding the potential inaccuracy of data are incorrect.
These are reasons why potential inaccuracies could exist but this is not evidence of inaccuracy.
The process retain to this potentially invalid data is as follows:
“To maintain a table in MMPDS, additional test data of approximately 25% of the number of specimens originally submitted with the data package, is required in order to perform a sunset review.”
The process is better defined in MMDPS Section 18.104.22.168:
Extract from MMPDS-10, shown under “fair use”
The key passage is “Published tables for which confirmatory data is not provided will be removed from the handbook at the next change notice or revision…….”
Sure – this all sounds reasonable so far. So there is a manual that used to be issued by the US government without charge. This data has been licensed to a commercial (although non profit) entity.
Great, this renowned organization, The Battelle Memorial Institute, who charge $919.00 (https://www.mmpds.org/wp-content/uploads/2017/09/2017-ISH-Order-Form.pdf) for this formerly public domain document are going to spend some of the revenue generated on providing even better data.
This is what we have been waiting for – it rankled to have formerly free data put behind a paywall (and what a paywall!) but now this makes sense.
Hold on, reading the MMPDS explanation of the process the world renowned Battelle Memorial Institute will not be doing the testing.
“ Confirmatory test data shall be generated by the original data supplier(s), or other interested parties, and reviewed by the Fastener Task Group, (FTG),”
This looks like the Battelle Memorial Institute is relying on industry, the same industry that pays $919 per copy of the MMPDS, to do the testing for them.
Maybe the Battelle Memorial Institute can’t afford to do the testing, being a non-profit must be a fine balance between profit and non-profit.
You can review the latest issues financial statements from The Battelle Memorial Institute here:
In 2016, this organization, who need you to buy their MMPDS and do the testing for them managed to struggle by on a revenue of US$4,801,753,000 (Page 5) and have net equity (assets) of SU$1,138,054,000 (Page 4).
Clearly they need my help, how can I expect an organization with that value of revenue and assets, who charge such a high price for data mostly created by an industry and a government before they got ownership to do their own testing?
The question is rhetorical.
So to summarize
- There is a concern that some of the fastener data in the MMPDS has the potential to be non-conservative
- This is because either the original testing was not adequate or because of a nebulous change in “fabrication methods”
Note that not a single example of inadequate quality fastener strength data from the MMPDS leading to any incident in qualification or service is cited.
- Because of this all fastener data will be reviewed every 10 years (It is not clear if ‘review’ means ‘remove’ in this context, reading the latest edition of MMPDS it appears that ‘remove’ is probably the correct interpretation)
- Data will be reinstituted in the MMPDS only if testing is done by somebody else
When the Mil-Handbook 5 was cancelled, responsibility for the management of the materials database was assumed by the FAA. The FAA decided that the MMPDS would be created and managed by the Battelle Memorial Institute.
The FAA mission statement (https://www.faa.gov/about/mission/) lets is know that:
“Our continuing mission is to provide the safest, most efficient aerospace system in the world.”
Considering the recent change to the part 23 regulations and this sunset clause for previously widely used material data, apparently they think the best way to do this is to make the aerospace product qualification and certification process increasingly expensive and absurd.