The FAA has issued an Airworthiness Concern on STC SE4985NM. They are asking for information from users about which crankshaft is in their engine due to a crankshaft fracturing on a modified engine.

Question # 3 is the important one we Pponk owners need to address.

3) If you have an engine with either STC SE4985NM, SE10233SC or both installed, please confirm whether
your crankshaft was manufactured using the Airmelt process or the Vacuum Arc Remelt (VAR) forging
process (please refer to CSB96-8 for guidance on how to identify your type of crankshaft). If you do not
know which process was used for your crankshaft and are unable to determine it, please respond to this
question with ‘Unknown’.

You can view the document at:

https://www.faasafety.gov/files/notices ... nental.pdf

Thanks. Sent a completed form in.

I just came across this as well.

It looks like a key point is the starting point of the your particular O-470-50. Many were built from 520’s(a TSIO-520 in my case, if I recall correctly). The document specifies O-470’s that were modified, unless I’m missing something.

Aqua

You are correct about the modification. I got some clarity from Norma Knopp as follows:

STC SE4985NM does not require installation of a VAR crankshaft. The concern is for O-470 engines modified under SE4985NM that have been further modified by installing a supercharger.

Rich

rfinkle wrote:Aqua

You are correct about the modification. I got some clarity from Norma Knopp as follows:

STC SE4985NM does not require installation of a VAR crankshaft. The concern is for O-470 engines modified under SE4985NM that have been further modified by installing a supercharger.

Rich

From my understanding, while they arent required to use a VAR crank, the FAA is curious if this is part of the reason for failure as the non VAR cranks may not be strong enough to handle the extra power. Tue super charger doesnt help, but I do have to wonder a bit if they aren't onto something with the VAR crank issue as well.

Wouldn't you know it, my 470K is torn apart with a .010 undersize crank from the 1950's. Might make a call to the shop and find out what they think even though I talked to them yesterday and they didn't mention this deal.