In article , Corky Scott
wrote:


FAR 33.43 is also relevant here. It requires a torsional and bending
vibration survey, using a prop (and of course a PSRU if applicable) at
up to 110% of max continuous rpm.

The requirement to test the PSRU is important, as they can be the
weakest link in the power chain.

It is difficult to compare the aviation engine type certification tests
with the automotive durability tests, as the two tests are doing
different things. The automotive test is trying to find problems that
will cause the manufacturer grief in automotive service.
Unfortunately, the configuration tested may be quite different from the
one we would use in an aircraft, as there is no PSRU, and there may be
substantial differences in ignition and fuel delivery systems. The
aviation engine test is supposed to test the whole engine, PSRU, etc,
in a configuration that is suitable for airborne use.

Continuing airworthiness issues also come into play here. The aviation
engine manufacturers are required to inform us about any major problems
they learn about. For automotive engines you may only learn about
problems and fixes through the grapevine (e.g. Ford V-6 coolant leaks
into the oil system).

So, in the end, the only way to figure out whether a given automotive
conversion will work is do fly it and find out. Eventually we'll have
enough service history to know what works, and what doesn't.

I'm not anti-automotive conversion - I'm considering a Mazda conversion
for my next project (please don't tell my wife I'm considering another
project - she still expects to get the garage back once my RV-8 is
flying).

======================

Section 33.43: Vibration test.

(a) Each engine must undergo a vibration survey to establish the
torsional and bending vibration characteristics of the crankshaft and
the propeller shaft or other output shaft, over the range of crankshaft
speed and engine power, under steady state and transient conditions,
from idling speed to either 110 percent of the desired maximum
continuous speed rating or 103 percent of the maximum desired takeoff
speed rating, whichever is higher. The survey must be conducted using,
for airplane engines, the same configuration of the propeller type
which is used for the endurance test, and using, for other engines, the
same configuration of the loading device type which is used for the
endurance test.

(b) The torsional and bending vibration stresses of the crankshaft and
the propeller shaft or other output shaft may not exceed the endurance
limit stress of the material from which the shaft is made. If the
maximum stress in the shaft cannot be shown to be below the endurance
limit by measurement, the vibration frequency and amplitude must be
measured. The peak amplitude must be shown to produce a stress below
the endurance limit; if not, the engine must be run at the condition
producing the peak amplitude until, for steel shafts, 10 million stress
reversals have been sustained without fatigue failure and, for other
shafts, until it is shown that fatigue will not occur within the
endurance limit stress of the material.

(c) Each accessory drive and mounting attachment must be loaded, with
the loads imposed by each accessory used only for an aircraft service
being the limit load specified by the applicant for the drive or
attachment point.

(d) The vibration survey described in paragraph (a) of this section
must be repeated with that cylinder not firing which has the most
adverse vibration effect, in order to establish the conditions under
which the engine can be operated safely in that abnormal state.
However, for this vibration survey, the engine speed range need only
extend from idle to the maximum desired takeoff speed, and compliance
with paragraph (b) of this section need not be shown.

--
Kevin Horton - RV-8
Ottawa, Canada
http://go.phpwebhosting.com/~khorton/rv8/