Thanks Ian for your insights and concerns. Regarding ferrell cracks, are you able to identify them without disassembly during your inspections? Or are they being found during overhaul?
Best, Michael Stockhill Polson, MT On Sat, Jun 3, 2023 at 3:51 AM Ian Williams <i...@agcon.co.nz> wrote: > Hi All, > Could you read below and comment. I would be very interested in any > suggestions or comments about this issue. > Basically trying to address a solution to some pretty significant issues I > am having with Hoffmann. I really dont know exactly what is happening … > have heard a few slightly different stories but fundamentally they appear > to no longer be interested in supporting our HO-V62 props. > So I have been looking at alternatives. > Some background > I am the maintaining engineer here in New Zealand for 2 H36’s and 2 Grob > 109A’s. > Hoffmann produced an SB regarding a 6 year Calendar life for these props > (and were quite anal about that) > So as I had 3 props that were basically overdue, I organised a calendar > service. Of the 3 props only one was serviceable, the others had cracked > ferrells .. one a hairline radial crack which was not easy to see and the > others had very significant vertical cracks and significant damage to the > ferrells between the 2 halves of the counterweight clamps. Basically the > blades are unserviceable. > THere is a lot of other background detail here, but to keep this > discussion short that could be discussed later.. > The problem is that Hoffmann seem unable (OR UNWILLING) to provide any > technical support in terms of Acceptable Technical Data (ATD) to even > their Hoffmann approved service dealer ( Australia and New Zealand). THat > company has indicated to me that they have been so frustrated with lack of > support they have terminated their relationship with Hoffmann. > SO WHAT TO DO. > Consider that the HO-V62 props and their mechanical pitch change have been > around for a very long time in fact since the late 1970’s. Apart from the > P mod (8mm rods) and various SB’s plus the BT blades, there has been no > significant design change over those years (40 plus). I guess being type > certified there is no real incentive to change owing to litigation > vulnerability.maybe. > I have no operational issue with these props .. have many hundreds of > hours behind them over the years and while there has been some minor > glitches , fundamentally they have been quite OK. And if supported by > Hoffmann , OK into the future as well. > However with an apparent communication and support brick wall from > HOFFMANN I think a modern alternative is needed. > Seems there are 2 > One is the MT prop ( electric version). The other is the Airmaster prop > from down here in New Zealand (electric constant speed with feather) > Obviously I am following up the Airmaster being Local. The issue is of > course that the Airmaster prop is not TSO’d so a little tricky to install > on a type certified aircraft. > There is a lot of detail about Airmaster props on YouTube if you want more > information. Yesterday I had a meeting with their chief engineer (and > owner) who gave me a very detailed tour of their facility. on a scale of 1 > to 10, it would be 100. They make full use of CNC machining equipment and > up to date design systems. All the hub engineering design and manufacture > is carried out in house. Only the blades are externally sourced ( > Sensnich). They are composite and are a slightly different shape than the > Hoffmann blades. IMy suggestion would be 2 blades. So at first glance would > look the same as the Hoffmann > So to cut a long story short, I am following up. ( Note in New Zealand) > * A change from a standard category C of A fo a Special Catagory C of A. > * Ordering a set of blades for rh rotation designed specifically for the > L2000 engine and speed range for the H36. > * if all OK, installing prop on our H36 flight testing etc and flying > happily ever after. > > THe constant speed facility would be a real plus especially on take off > where the engine RPM increases significantly with speed. THe time from > feather to full fine is around 20 seconds (which we can live with) > > So. That do you think. ,, am I going in the right direction > > Best regards > > Ian Williams > ZK GCB > New Zealand > > --------------------------------------------------------------------- > You are subscribed to the Dimona Owners Group mailing list. > This list is archived in public. http://waikeriegliding.com/dog/ > To unsubscribe, send email to: dog-unsubscr...@lists.riverland.net.au > >
