|
Well said Thomas. I'm with you on filters.
Georges B.
-------Original
Message-------
Date: 02/15/06
10:51:52
Subject: [FlyRotary]
Re: Need for air filters
Al,
It is not the percentage of time you spend in
(possible) dusty conditions versus clear, but about the split-second
your istallation ingests the small piece that will wedge between the
seals and the housing and kill the engine in short order ( ..... though
it won't throw a rod or valve .)
I think it was recently mentioned, that this is
one of the few things where the rotary is less forgiving than a piston -
A piston might pop the FO around for a while and then spit it out. In
the Rotary you have a high chance to wedge ity on the first half
rotation (centrifugal force will urge the FO to the
outside....)
I flew most of my flying hours in front of an
airfilter on a piston. Power was never a question - the particular
engine installation is over dimensioned, so there is always excess-power
available.....
remember that altitude is not always clean either:
Volcanic ash clouds, desert dust/sand reaches very high!!
FWIW,
Thomas J.
8500 hrs and counting....
----- Original Message -----
Sent: Wednesday, February 15, 2006
12:05 PM
Subject: [FlyRotary] Need for air
filters
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.
|