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When you take an IO-550 with a 10:1 compression ratio and then install a
supercharger without an intercooler you are asking for problems. My TSIO-550
has a 7.5:1 compression ratio and two intercoolers. I also have two
temperature probes in the induction system to monitor the induction air
temperature. While my turbos are capable of producing 75" of MP at sea level
I would never attempt to run that kind of power without the use of ADI and
very high octane aviation fuel.
I think that Shannon probably failed to take into consideration that if you
put a supercharger on an engine with a 10:1 compression ratio (and no
intercoolers) it would not be prudent to not boost the engine above normal
MP. I expect he used the increased power that was available often and this
resulted in the engine damage that eventually caused the engine to quit. I
think he would have been OK if he would have used the supercharger to
normalize the engine. I did have conversations with Shannon about his
airplane while mine was going together, and was sad when he was killed.
As far as Rick is concerned, I believe he flew (was the race pilot) his
supercharged Legacy at Reno at least once. He lost to Darryl Greenamyer who
was flying his own TSIO-550 powered Super Legacy. If I remember correctly
their race speeds that year were in the 325 to 330 MPH range. Since that
time the Super Legacy race speeds at Reno have increased to the 370 to 380
MPH range.
A cruise true airspeed in the 260 to 275 knot speed range at 16,500 to
17,500 with manifold pressures of 27" to 28" is realistic.
But over boosting an IO-550 with a 10:1 compression ratio is not wise, IMO.
Lynn Farnsworth
Super Legacy #235
TSIO-55- Powered MMO .6 Mach
Race #44 -----Original Message-----
From: Lancair Mailing List [mailto:lml@lancaironline.net] On Behalf Of Skip
Slater
Sent: Monday, June 10, 2013 12:44 AM
To: lml@lancaironline.net
Subject: [LML] Re: Experience with supercharged Legacy?
Rick Shrameck (who founded Epic Aircraft and had a lot of experience in auto
racing before he got into aviation), built one of the first Legacys and
developed a supercharging mod for the IO-550. His company was called Aero
Supercharger Solutions and was based in North Las Vegas. His Legacy, which
was flown by a race pilot, had a supercharger on it and was entered in the
Reno Air Races for a few years.
Rick's most notorious supercharged installation was in a Legacy built by
Shannon Knoepflein . For those not familiar with him, Shannon was an
electrical engineer and had about every gadget known to man in his plane. He'd reported persistent problems with high oil temps and a couple of
particularly hot cylinders for several months after his engine mod, but kept
flying anyway. He took his plane to Oshkosh in 2004 and mentioned his
overheating issues to several people there. He was advised by some of them
not to fly again until he figured out the problem, but he decided to fly the
plane home anyway. Witnesses said his engine was missing badly on the
takeoff roll, but he continued on anyway. A few minutes after takeoff his
engine suffered a catastrophic failure when an apparent case of pre-ignition
caused the number three piston to suffer a burn through. Shannon passed by
one airport in an attempt to deadstick his plane into Madison County. He
didn't make it to the runway and was sadly killed in the subsequent crash. Metal was found throughout the engine and there was a large hole at the top
of the crankcase. There was also evidence of overheating damage to several
other engine components. I recall that almost anyone who had an opinion at
the time felt the supercharger was the root cause of the problems that
Shannon had. I'm not aware of anyone who installed another supercharger
after that and Aero Supercharger Solutions closed up shop soon thereafter
for lack of business.
For anyone interested, this link is to the accident report:
http://www.ntsb.gov/aviationquery/brief2.aspx?ev_id=20040804X01144&ntsbno=CH
I04FA203&akey=1
Skip Slater --
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