On 20 Nov 2003 07:36:47 -0800, (Rick Durden)
wrote:

TC,

The AT-10 you mentioned did ring a few bells. Talk about an
incredibly rare airplane that wasn't built to last...wooden fuel tanks
wrapped in rubber, amazing. I wonder if any are in existence outside
of museums, they'd be even more costly to keep flying than a Cessna
T-50.

I've flown the 300 hp Boeing Stearmans and have always thought that
was the correct engine for that airframe as the original 220 hp
version is pretty badly underpowered. I had no idea that the engine
mod was essentially a bolt on from the AT-10. I had a vague
understanding that a lot of BT-13s gave their all for the R-985 mount
so the Boeings could become crop dusters.

So, AT-10s from Beech live on (in part) on Boeings built about five
miles southeast...

Now, as to putting an R-680 on a Beech 18 airframe that wasn't
originally designed for the small engines....well there are
'interesting' ideas all the time in aviation. Just yesterday I got
word of a guy who droped a Chevy V8 into a Cessna 150, used rubber
hoses for the fuel lines and couldn't seem to understand why the FAA
was a little less than understanding about the whole thing. Just
because he hadn't sought to get any sort of approval before deciding
to fly it...

sig snip

I'm one of those picky IA's that thinks "An aircraft or part is in an
Airworthy condition if it conforms/meets its type certificate data
sheet or proper altered condition" isn't an optional kind of
statement.

So when I dug into the maintenance records of a 300 hp Stearman at
annual time, the aforementioned STC got my attention. Thought the
AT-10 designation was vaguely familiar, dug out my dog-eared copy of
the The Immortal Twin Beech (Larry Ball) when I got home and found a
reference to it.

Have spent a lot more time working on the R985-AN14B than I have on
the 300 hp R680(don't remember the suffix). The R680 on the Stearman
wasn't exactly my favorite engine. I enjoyed driving it around, but
spent too much time working on it.

The R680 wasn't originally a top-oiled engine, instead had hollow
rocker shafts equipped with grease zerks. The 300 horse version I
worked on had an internal orifice that had to be inspected/cleaned
regularly to ensure/insure said top-oiling was present.

The valve train required frequent inspection/adjustment/rocker bearing
replacement (200 hours/annually tops). Was never sure whether this was
a lubrication issue, or an issue with the replacement parts that were
available.

The upper cylinder castings were kinda scary. Again, not sure if this
wasn't in part due to the "parts" available. All I know is that I blew
the sidewalls out of several of them while carefully r/r'ing the
rocker assemblies.

Contacted the guy that had overhauled the engine I was working on, he
told me in regards to TBO "if you think it's getting shaky, yank that
bitch-it will come apart on ya"-to paraphrase slightly.

Can't compare the 300 hp Stearman to any others, it was the only one
I've ever had the pleasure of flying. Couldn't get it to snap to save
my life, later found out that the military added extended stall/spin
strips on the bottom wing to aid the airflow in leaving the wing when
desired. Have looked at a bunch of other examples, have yet to come
across one with the strips installed.

Worked on "Super" 18's in the early 80's, performed all the
maintenance related to about 12,000 operating hours hauling auto
parts. Wish I had one to play with now...

Regards;

TC