Subject:
[FlyRotary] Re: Engine failures, Rotary or otherwise
To
clarify the air filter issue. I seem to remember someone posting a page from
the mazda manual regarding apex seal tolerances after Ed's failure and
later confirmed the slot was out of spec. I remember the manual said to check
the air filter. Mazda seems to think running without a filter or (dirty
filter?) will cause rotor apex seal slots wear. Is this
correct?
Bobby
I don’t think there
is any doubt that every ‘terrestrial’ vehicle needs an air filter. They
run on dust laden surfaces, and, at times, on unpaved surfaces which
themselves are dust; resulting in the ingestion of a lot of abrasive
material.
The rational (at
least mine) for not using a filter on an aircraft is that, a) it spends little
of its time on a surface, and then on one that is paved a periodically blown
off by other aircraft, and b) the amount of particulates above a few hundred
feet (and certainly at a few thousand feet) is very low; probably similar to
what goes through a filter in dusty conditions.
If my flights
averaged something like a couple of hours each, there is about 15 minutes on a
relatively clean surface for every 2 hours up in clean air. If the rpm
in the air is 5500 and that on the surface is 1800, then the fraction of air
volume used where there may be some fine particulates of concern is about
4%.
So I’m willing to
accept that in exchange for keeping the ram air manifold pressure increase of
about 1.5” Hg that I can get when cruising close to 200 mph for the 2 hours
that I’m not on the surface. A compact filter is going to eat most if
not all that ram pressure. If you aren’t concerned about the pressure
loss, or you can include a sufficiently large filter enclosure, and not lose
too much of the ram pressure in expansion, contraction and friction losses;
then it makes sense to include an air filter.
I am definitely not
advocating not using a filter. Just giving you my rational, however
faulted, for going without one. (BTW, I do have a screen at the largest
diameter in the intake duct to prevent anything bigger than about 1/32” from
getting through).
FWIW,
Al
With
all due respect; I don’t disagree with what you’re saying here, but I do take
offense at you calling Tracy, myself, and others “idiots” because we have
chosen to run without an air filter. My intake is in front of the prop
and above the wing strake. Anyway, why climb on that issue? There
has not been a single aircraft incident that I am aware of that has resulted
from not using an air filter. Let’s pick an issue which has
caused a failure.
I
won’t argue that running without a filter may reduce the engine life; and I
may consider one later. And yes, the engine would eventually fail; every
engine will – filter or no filter - if you run it long
enough.
Al (I
guess it’s past my bedtime)
Rusty,
and Group,
I
understand your comments Rusty, and think you are both right and wrong. I
believe it is easier, for most people, to be successful with a standard
aircraft engine. I DO NOT believe this is because the Lyc, Conti, or whatever
is inherently more reliable. I do believe that the ancillaries are better
developed for "conventional" aircraft engines.
Because
we [FlyRotary or ACRE] are rotary
enthusiasts we hear about EVERY rotary problem. If we heard about every Lyc
problem caused on a daily basis we might never fly spam again! I am not trying
to offer so anecdote to soothe the rotary faithful, as all failures are just
that, failures. I would remind everyone that ALL Lyc installs in certified
aircraft now come with AIR FILTERS!
I'LL
SAY THIS FLAT OUT, IF YOU DON'T RUN A FILTER YOU WILL HAVE A FAILURE! I don't
care if your running a conventional aircraft engine or conversion. Running
unfiltered is simple idiocy.
It
should also be said that for Lycoming to be having crankshaft failures, and a
significant number of them to initiate an AD is not only sad but smacks
of reckless disregard. So saying that the aircooled aircraft engine is super
reliable is simply setting yourself up for a fall. If you look at the
statistics most of the engine failures are "certified" engines simply because
there are more of them!
ANY
ENGINE properly maintained and not operated outside it's normal limits will
work just fine thank you, provided it is not a deficient design to begin with.
The rotary requires a GOOD water and oil cooling system. If you aren't willing
to work on that, stop now and don't hurt the reputation of the rest of us and
go buy a Lycoming. The rewards for a GOOD installation are many but won't
"just happen." As Tracy said you must go in
with the knowledge of the needed systems or you will fail. If you do slipshod
work, Rotary or Lycoming, YOU WILL FAIL. Someone put the old saying on the
site, "How do you eat an elephant?" "One bite at a time!" This is the proper
way of looking at the jobs needed to be successful. You MUST do all the jobs.
(eat every bite) And most importantly you must do all the jobs well. Safety
wire everything even though it's a pain in the ass. If you can't do all the
jobs yourself it's no crime. Get HELP! Buy the redrive from
Tracy. Or buy from
Mistral, or buy them from Marcotte. Build your system up and test it on the
ground. If you overheat your system on the ground don't assume it will be
better in the air! (It might be, but also might not be!) Plan for an adequate
sized radiator. That would be a MINIMUM of 2 cubic inches pre HP, and that
only if you have PERFECT ducting. (3 c.i. per HP would be a safer bet) Don't
expect you are the miracle guy that can change physics for your own
project. Rusty has brought up some good points in pointing out that if
you want to fly soonest buy conventional. Bernie, you can probably rebuild
your system from all new parts for less than the cost of two Lyc cylinders. As
an older guy facing family pressures I can understand how you might not want
to though. This is no crime. Your needs are your own, though I would prefer to
see you go back to the rotary and succeed. We all need to go in with our eyes
open. When setting up race cars and motorcycles I would look at every part
from the stand point what will happen if this part breaks? If the result would
be a crash I would redesign the part until I was SURE it wouldn't break. If
you don't think a part is adequate DON'T USE IT! Your responsibility is to
find a part that IS good enough. Don't just hope that everything will be OK.
Work it out. Run your system enough to be sure of it in the
air. I hope everyone takes this in the spirit intended which is to
have us all come home safe.