Ad: This forum contains affiliate links to products on Amazon and eBay. More information in Terms and rules
"Forget"? Blast air injection diesel was the tecnology that didn't work well (even for economic reasons obviously) for small engines, and led to the predominance of the prechamber for about 60 years.Dogwalker, you forget that diesels employed blast air injection
And so? It was a prechamber diesel, it worked with low pressure injection.As for injection pressure, I have driven a 1980s Fiat Ritmo diesel that was of prechamber design, yet the injection pressure was some 150 bars even though some sources claim that as low as 70 or so bars is possible.
Right. Apply a sufficient amount of money, and problems will be solved. Today as in the '30s. But that not means that there are/were no problems to adress.As for why wasn't direct injection diesels adopted in automobiles in wide scale until quite late: cost.
I think one major problem with many small aircraft diesels today is that they attempt too much with odd solutions like that Zoche design. Another question is that where is a modern (=not decades old) small 250-300 hp class simple low-cost turboprop? I don't refer to Allison 250 and likes.
EDit: There is the RR300, but its sfc figures are not too attractive.
Don't forget the certification process. The Feds in many cases make profitable engine development very difficult.
eCFR — Code of Federal Regulations
While regulation is required, there is no doubt that because of the way its interpreted (and the way its enforced) it limits development and in my 35 years in this business I've seen dozens of bureaucrats being extremely obstructive as there are many people in MIDOs that don't know what they are doing and know little about new technologies; that's why you have seen little in recip engine development during the past 40 years.Yes, the certification costs aren't cheap, but the regs are there because of past manufacturer screw-ups, not just because bureaucrats are being obstructive.
The FAA - the compassion of the IRS combined with the efficiency of the US Post Office...
Well, there are ways of saving money. GE skipped the bird shots on their CF6, certifying it by similarity with the TF39s, which was a massive cheat (as in, imho, fraud)
Just an after thought on this - who from the FAA or what DAR/DIMR signed the final certification paperwork? I've seen certifications like this happen and off the cuff I don't think there's a whole lot of difference between the two (I do know the CF6 was developed from the TF39 and they are very similar). If the Feds allowed this to happen its on them and my previous point well proven. If GE did this without FAA approval, the ones responsible for this should be in jail - just wondering!
The TF39 has a completely different fan assembly than the CF6: the TF39 has a two-stage fan; the CF6 has a single stage fan. Trying to get it certified by similarity was a bald-faced lie; as I said, the feeling at Lycoming was that if we or Pratt (a lot of people I worked with there were ex-Pratt) had tried the same thing, we'd have lost the type certificate, not just have the engine grounded.
In general, the FAA seems to do remarkably little vetting of manufacturer claims, until something goes wrong. We had our designated engineering rep, but he was a company, not FAA, employee. I don't remember hearing of an FAA employee ever witnessing a test. Certainly, none did on my watch.
Well apparently someone sold this to the Feds when they issued the TC, lie or not. It shows the incompetency at MIDOs. I've seen it flow the other way as well where a simple field approval wouldn't be approved because of a typo on the TC data sheet. Why fines and criminal charges didn't fly on this one beats me, probably because someone at the agency bought in on it and MIDO would get a bunch of egg on its face, the best thing to do is to just ground the fleet and make the mfg do a "do-over," the easiest way to make it go away.
I do know that there seemed to be a lot of CF6 failures due to hydrogen embrittlement, many ADs written against CF6s (from what I remember from my short DC-10 days)