Here are two interesting posts from Beech talk by Karl Beutner:
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I have an IO-550 built in 1993 with its original cam gear. I recently found out that my cam gear is P/N 631845. I am not certain but I think that this is the predominant PN for cam gears prior to 1999. In at least one of the cam gear related threads at this site it is claimed that this PN gear has “never failed”, with no mention of the basis for this claim? I went to the FAA site and searched for SDRs with PN 631845 and the search yielded only one cracked gear report:http://av-info.faa.gov/sdrx/Query.aspxIn search of more data I Googled SDR and found this database site:http://www.aviationdb.com/index.shtmI did a search of SDRs with PN 631845 which yielded 14 SDRs which by my tally included 8 reports of broken teeth and 6 engine failures. So unless I am missing something it appears that this gear has failed and has resulted in engine failures?
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I went back and looked at some details it looks like 8 or 9 of the reports were from twins and none in Bonanzas? Could just be small sample size but the high proportion in twins is at least interesting?Also 14 events in over 40 year does make it a rare eventOnly 2 in the past 17 yearsAnd 10 of the 14 were prior to 1994Date Of Report Operator Control Number Date Of Occurrence Aircraft Manufacturer Aircraft Group Code Aircraft Registration1 Details 1975-06-05 Z197515600059 BEECH 55 69SF2 Details 1977-03-09 Z197706800069 CESSNA 340 7622Q3 Details 1977-05-18 Z197713800089 CESSNA 206 866424 Details 1978-09-21 Z197826400077 CESSNA 210 732BP5 Details 1980-09-29 CE65198079337 BEECH 58 444SB6 Details 1980-12-02 CE65198082489 BEECH 58 444SB7 Details 1987-03-17 WP138773458 1987-01-27 CESSNA 402 444028 Details 1988-02-24 NE638874375 1988-01-21 CESSNA 210 7326A9 Details 1989-02-23 WP258975440 1989-01-31 CESSNA 210 3599P10 Details 1992-11-04 92ZZZX10210 1992-10-12 11 Details 1994-05-23 94ZZZW1891 1994-04-11 CESSNA 402 4055Q12 Details 2000-11-29 20000831SH017 2000-08-10 BEECH 95 22EW13 Details 2000-12-07 AU000756 2000-08-29 CESSNA 206 14 Details 2010-12-15 2010FA0001173 2010-10-11 BEECH 55 9580Q