Baron B55's fitted with the ubiquitous IO470-L
engine have been known to have a fair amount of vibration issues. Ever seen a
40-50 year old B55 air box? Well then you know what I mean.
During my 2016 annual, I discovered a failed Delco
alternator bracket in my 1965 B55. My IA has repaired it by welding it back
together, however, I'm going to go with the new design and sell the original
repaired bracket on eBay. Give this area a good look during your annual
inspections if you suspect you have the earlier bracket design. Oh yeah, you
will get to find an engine hoist to lift the engine up enough to remove the rear
motor mount to remove the bracket for repair or replacement
Below is the alternator mount IPC extract.
Click the image for the IPC page extract.
See image below of the early un-reinforced
bracket design, which is Item #4 in the above IPC:
Below is the same bracket 10 years and about
1100-1200 hours prior in pristine condition.
Fortunately, I was able to source a
replacement for my early Delco alternator bracket from
ENPARTS in Dallas, with
what appears to be a later design with gusseted reinforcing members. Beech must
have learned that this area was prone to vibration fatigue and implemented a
redesign of the bracket. The reinforced bracket is shown below:
According to an excellent starter and
alternator rebuilder, Modified Aircraft
Accessories, another watch out for those of us B55 owners with engines
fitted with Delco alternators is the fact that brushes are NLA (No Longer
Available) for these alternators, so we are SOL on overhauling these units if
you need brushes. If you have a Delco Alternator,
HERE is a
repair work order which lists all the parts for a Delco Alternator rebuild, if
you can find them
These are the Delco PNs affected:
However, Modified advises that a replacement
option that will fit into the existing bracketry is out there in the form of the
Cessna 310 Alternator, Ford DOFF-10300B, a 60 Amp unit (which is a nice
performance boost). The Cessna 310 used the same IO470 engine for quite some
time as well as the Baron B55.
Big thanks to Jimmy at Modified for bringing
this alternative solution to our attention. Of course you're on your own for the
paperwork on doing this. You can spend your way out of the problem by changing
to a Prestolite bracket and sourcing that alternator, but that will require
sourcing the bracket, lifting the engine and removing the motor mount support in
front of the bracket. If you're going to go through all of that you may as well
change at least your rear engine mounts. Here are some of the Prestolite PNs
that I think are applicable to the B55 w/IO470L engine (check the TCDS and your
IPC to be sure):
Or you can spend mega bucks and go with a
Plane Power conversion. You and your mechanic make the choices here.
Good Luck in whatever way you choose to deal
with the Delco alternator obsolescence.