Merlin engine rebuild cost

[Paul Draper]

i heard that roush was going to make new castings of major components eg heads blocks and other ancillary parts but ran into a brick wall with RR who refused to grant the rights to reproduce they're designs don,t patents run out?

We (Roush) did look at casting new cylinder heads in the past, however at this time it is not economically feasible due to the cost of the castings and all the parts that are incorporated into them. Meaning, we can make them, however nobody would buy them for the price we would have to sell them for. We can repair original castings for a lot less than making new castings.

Our estimate is that there are approximately 5 engines for every flying Merlin powered aircraft. With that many cores available, there is no market for new castings.

There is no brick wall with Rolls Royce, Packard, or the FAA. We have a large library of original drawings, manuals, repair specifications, mod notes, and tech orders for the Packard and Rolls Royce Merlin Engines. This provides us with the necessary information to reproduce and re-design/re-engineer (improve) parts for the Merlin Engine, and obtain FAA approval. Many of our FAA PMA parts are manufactured exactly to original specifications, as no improvements are needed, just a supply of new parts.

Last edited by Paul Draper on Wed Sep 05, 2012 8:06 pm, edited 1 time in total.

[51fixer]

I am still not a firm believer in all of the "upgrades" and new manufactured parts. In my experience there seems to be as many (or more) problems with the "new and improved" models. As an example (this is just an example, so please no flaming), one kind of "Merlin fingers" has a slight issue with the pads falling off. There are other issues though, and not just with the Merlin (Air Tractor crank anyone?). I will not delve into them here because I do not want to start a flame war.

It is not limited to just the Warbird stuff either. Lycoming has been building the same basic flat motor since the earth cooled, and the new ones seem to have more AD's against them than the old ones do. Come to think of it, that may apply to Cessna 172's as well.

Engineers..... You can tell them from 20 feet, but up close, you can't tell them anything.

Get back to me in 70 years and if these upgrades are still in reliable use, I might be convinced that they are ok.

Many of the Roush parts are improvements, not so much a mod. They are also getting engines to the 1000 hr mark.

[shrike]

It is not limited to just the Warbird stuff either. Lycoming has been building the same basic flat motor since the earth cooled, and the new ones seem to have more AD's against them than the old ones do. Come to think of it, that may apply to Cessna 172's as well.

It's more a matter of the FAA being more willing to knee-jerk an AD now than they were 'back in the day'. Ex.-Eismann had exactly one AD on all of their magnetos - one batch of bad coils - but if they have such great quality control, why can't you buy one new?

[JDK]

Very interesting post from Mike, and a few thoughts occur, as this is a general discussion... These are by way of looking at general factors, expectation and analysis, not specific or engineering comment (which I'm not qualified or knowledgeable about!) and a riff on, not a criticism of Mike's comments.

I am still not a firm believer in all of the "upgrades" and new manufactured parts. In my experience there seems to be as many (or more) problems with the "new and improved" models.

That's an interesting thought, but if it's subjective, of no value (you've got to quantify it, for the comparison to have any value, rather than being a variation of "the new stuff's not as good as old stuff..." twitch. But can you? I don't believe the data field is big enough or reliable enough.)

Also, more critically, there are a couple of changing vectors here - i.e. the expectation and performances then are not the same as now - they've developed in a direction over the time elapsed.

Firstly W.W.II era kit was not designed for longevity or low intensity long-term ops, but since then, stuff is being expected to perform for a long time - many, many more cycles, but at lower power, weights and altitudes. Hence failures the original designers would have been wrong to have designed for, like aged magnesium casting failures.

The second vector is that the expectation of reliable performance from W.W.II to the present has radically changed (car servicing and regular maintenance is the good comparison for that, from regular owner participation and care to no-touch today). Looking at that, it's clear that W.W.II (or 1950s) expectations of reliability are well below modern benchmarks.

That said it depends on data. Talking to someone responsible for a Merlin recently, he said that some information is shared readily, some not. I expect that data of old originated and mod-originated failure rates are too patchy to really draw meaningful conclusions from in general.

It is not limited to just the Warbird stuff either. Lycoming has been building the same basic flat motor since the earth cooled, and the new ones seem to have more AD's against them than the old ones do. Come to think of it, that may apply to Cessna 172's as well.

An obvious though that pops up here is that even without the greater, modern risk aversion culture (which is another way of saying failures are less expected or allowed now) the expectation we all carry is not actually an accurate memory of the performance that old engines gave.

In short, what used to be "Oh, they do that." is now "There's an AD for that."

Engineers..... You can tell them from 20 feet, but up close, you can't tell them anything.

Generally asking questions and listening to what's left out as what you're told is well worthwhile, I've found, albeit on a non-decisive active engineering basis.

But the shocking report on the Thunder City EE Lightning accident and a recent example of a warbird being engine run on stands for retraction tests shows that self-confidence still often exceeds training, laws, sense and good practice.

Get back to me in 70 years and if these upgrades are still in reliable use, I might be convinced that they are ok.

Good historical principle; that's certainly one way of testing what music's of merit! However it's of little use in a practical way, now, as we know. Whether you are talking engineering, aircraft colour schemes or publishing an article, sooner or later you have to commit to a decision, and handle the results, with a degree of honesty and humbly, being prepared to revise your practice from criticism or (hopefully minor) failures. Of course the engineering choices are potentially dangerous, while the paint and articles are unlikely to let someone down fatally.

And that's another crunch. With something like the Merlin engine, running a design like that today is a very different set of parameters than its design. It's a 1930s engine, with 1930s expectations built in, and consequences refined out over the following years. You can change nothing, or undertake RR suggested changes or even add modifications beyond that; in all cases there are risks to do with the complex interactions of those elements with other elements. You are, however giving it all lots of the fourth dimension - time - to bite you in, and given long enough, everything will go wrong. Generally, that should be a long time after the engine is checked over or rebuilt.

Just a few thoughts,

Regards,

[Sabremech]

All the numbers posted so far seem inline with what we paid for the engine O/H in Baby Duck. We've had good reliability so far and are pleased with it's performance. As Rich said, I've started a business to manufacture obsolete parts from Vintage aircraft to Jet warbirds. If anyone wants to see what projects are in work, my website is http://www.vintageairworks.com. I recently finished crankshaft and camshaft gear bolts for the Continental 0-470-11 which is in the Birddog. Support for this engine is no longer offered by Continental, so here I go!
David

[Ryan Harris]

I've seen 2 Roush motors make it past 1000 hours and both were running like sowing machines when removed. A 3rd is now installed and is well on it's way to 1000 hours as well. I'm a believer...