Lancair 320 ram air?

Few weeks ago, 2 Lancair 320/360s stopped at my airport. I went over to get a
better look and found their engine air intake does not have any air filter.

Are they designed this way?

Would bugs be a problem?

Does it shorten the TBO?

On 25 Dec 2003 02:06:02 GMT, (ROBIN FLY) wrote:

Few weeks ago, 2 Lancair 320/360s stopped at my airport. I went over to get a
better look and found their engine air intake does not have any air filter.

Are they designed this way?

Would bugs be a problem?

Does it shorten the TBO?
+++++++++++++++++++++++++

I can't address what Lancair is doing, but....
my early RV-3 has UNFILTERED RAM AIR.

However, when carb heat is applied....
the alternate air path is through a filter
setup under the cowl.

All is still going well after 700+ hours.
Oil consumption is a quart in 15-20 hours.

To date, bugs have not been a problem.
There is an inlet screen and I'd guess the
occasional small bug just gets sliced, diced
and digested uneventfully. A swarm of locusts
could be a different story. g

The only thing I have discovered so far is that the
ram air path, as originally implemented, affected fuel
distribution to the cylinders somewhat negatively.
The cure is vane(s) properly positioned in the air
path or just use Van's later style intake air setup.
[I have a MM-1 buddy with a similar ram air setup
with the same damn fuel distribution issue.]


Barnyard BOb -- over 50 years of successful flight

On Wed, 24 Dec 2003 23:56:38 -0600, RR Urban wrote:


I can't address what Lancair is doing, but....
my early RV-3 has UNFILTERED RAM AIR.

However, when carb heat is applied....
the alternate air path is through a filter
setup under the cowl.

All is still going well after 700+ hours.
Oil consumption is a quart in 15-20 hours.

To date, bugs have not been a problem.
There is an inlet screen and I'd guess the
occasional small bug just gets sliced, diced
and digested uneventfully. A swarm of locusts
could be a different story. g

The only thing I have discovered so far is that the
ram air path, as originally implemented, affected fuel
distribution to the cylinders somewhat negatively.
The cure is vane(s) properly positioned in the air
path or just use Van's later style intake air setup.
[I have a MM-1 buddy with a similar ram air setup
with the same damn fuel distribution issue.]


Barnyard BOb -- over 50 years of successful flight


that is most curious bob. my aircraft has a brackett foam airfilter
(replaced annually) on the air inlet and none on the carby heat. the
reasoning is that carby heat is only applied when well off the ground
and the risk of contamination is small.

the problem is not bugs imho the problem is grains of sand.

you sure the builder didnt rig it up backwards?
Stealth Pilot

that is most curious bob. my aircraft has a brackett foam airfilter
(replaced annually) on the air inlet and none on the carby heat. the
reasoning is that carby heat is only applied when well off the ground
and the risk of contamination is small.

the problem is not bugs imho the problem is grains of sand.

you sure the builder didnt rig it up backwards?
Stealth Pilot
+++++++++++++++++++++++

It is neither curious nor backwards.

The few RAM AIR designs I have encountered,
ALL do WITHOUT the filter for max ram effect - even the
certified Mooney. However, Mooney does have a mode
that employs a filter when RAM AIR MODE is not desired.
In effect, I do the equivalent with carb heat mode.

FWIW....
Loss through the filter appears to be unacceptable to those
engineers that care to max performance with RAM AIR designs.
Perhaps those more knowledgeable will add their 2 cents???

P.S.
The RAM AIR topic has been addressed here in the past.
I'm surprised you are not somewhat familiar with the topic.


Barnyard BOb --

On Thu, 25 Dec 2003 12:15:46 -0600, RR Urban wrote:



that is most curious bob. my aircraft has a brackett foam airfilter
(replaced annually) on the air inlet and none on the carby heat. the
reasoning is that carby heat is only applied when well off the ground
and the risk of contamination is small.

the problem is not bugs imho the problem is grains of sand.

you sure the builder didnt rig it up backwards? Stealth Pilot
+++++++++++++++++++++++

It is neither curious nor backwards.

The few RAM AIR designs I have encountered, ALL do WITHOUT the filter
for max ram effect - even the certified Mooney. However, Mooney does
have a mode that employs a filter when RAM AIR MODE is not desired. In
effect, I do the equivalent with carb heat mode.

FWIW....
Loss through the filter appears to be unacceptable to those engineers
that care to max performance with RAM AIR designs. Perhaps those more
knowledgeable will add their 2 cents???

P.S.
The RAM AIR topic has been addressed here in the past. I'm surprised you
are not somewhat familiar with the topic.


Barnyard BOb --

I'm not sure how much manifold pressure is lost going through a well
designed filter. But, for the sake of argument, if we assume a loss of
0.5" HG manifold pressure, my O-360 power spreadsheet tells me that would
be about a 4 hp loss at a 75% cruise condition at 7500 ft, or about 3% of
the power. A 3% power loss would give about a 1% speed loss. If you want
to compensate for the loss in power by increasing the rpm, you need about
a 150 rpm increase to get the same power you would have had with no air
filter losses.

These numbers are specific to the Lycoming O-360A series engines, but I
would expect similar percent power losses for the same MP loss for any
normally aspirated engine. The power loss would be roughly linear to the
amount of MP loss.

--
Kevin Horton RV-8 (finishing kit)
Ottawa, Canada
http://go.phpwebhosting.com/~khorton/rv8/
e-mail: khorton02(_at_)rogers(_dot_)com

The Mooney I flew would gain 1" using the ram air feature. I don't
know if that is standard or how accurate the gauges are but that is what we
always showed.

Jerry

Kevin Horton wrote:
On Thu, 25 Dec 2003 12:15:46 -0600, RR Urban wrote:



that is most curious bob. my aircraft has a brackett foam airfilter
(replaced annually) on the air inlet and none on the carby heat. the
reasoning is that carby heat is only applied when well off the ground
and the risk of contamination is small.

the problem is not bugs imho the problem is grains of sand.

you sure the builder didnt rig it up backwards? Stealth Pilot

+++++++++++++++++++++++

It is neither curious nor backwards.

The few RAM AIR designs I have encountered, ALL do WITHOUT the filter
for max ram effect - even the certified Mooney. However, Mooney does
have a mode that employs a filter when RAM AIR MODE is not desired. In
effect, I do the equivalent with carb heat mode.

FWIW....
Loss through the filter appears to be unacceptable to those engineers
that care to max performance with RAM AIR designs. Perhaps those more
knowledgeable will add their 2 cents???

P.S.
The RAM AIR topic has been addressed here in the past. I'm surprised you
are not somewhat familiar with the topic.


Barnyard BOb --


I'm not sure how much manifold pressure is lost going through a well
designed filter. But, for the sake of argument, if we assume a loss of
0.5" HG manifold pressure, my O-360 power spreadsheet tells me that would
be about a 4 hp loss at a 75% cruise condition at 7500 ft, or about 3% of
the power. A 3% power loss would give about a 1% speed loss. If you want
to compensate for the loss in power by increasing the rpm, you need about
a 150 rpm increase to get the same power you would have had with no air
filter losses.

These numbers are specific to the Lycoming O-360A series engines, but I
would expect similar percent power losses for the same MP loss for any
normally aspirated engine. The power loss would be roughly linear to the
amount of MP loss.

Kevin Hortonwrote:

I'm not sure how much manifold pressure is lost going through a well
designed filter. But, for the sake of argument, if we assume a loss of
0.5" HG manifold pressure, my O-360 power spreadsheet tells me that would
be about a 4 hp loss at a 75% cruise condition at 7500 ft, or about 3% of
the power. A 3% power loss would give about a 1% speed loss. If you want
to compensate for the loss in power by increasing the rpm, you need about
a 150 rpm increase to get the same power you would have had with no air
filter losses.
++++++++++++++++++++++++++++++++++++++++

For the sake of argument, if we assume...
My *RAM AIR* only yields 0.75" HG with NO filter...
it's not difficult to understand why a filter is anathema
to the designed RAM AIR system.


Barnyard BOb --

Jerry Springer wrote:

The Mooney I flew would gain 1" using the ram air feature. I don't
know if that is standard or how accurate the gauges are but that is what we
always showed.

Jerry
+++++++++++++++++++++++++++++++++++

I'm no expert, but that's probably pretty close.

Dunno about accuracy, but my RV-3
displayed somewhat less. For me...
it's all much ado about nothing since it
has little bearing on any practical ETA.

Barnyard BOb --

"Morgans"wrote:

For the sake of argument, if we assume...
My *RAM AIR* only yields 0.75" HG with NO filter...
it's not difficult to understand why a filter is anathema
to the designed RAM AIR system.


Barnyard BOb --

OTOH, you could take the stance that the ram air is there to negate the
effect of having a filter, if you wanted to view the presence of a filter as
a mandatory option.

OTOH, I could be wrong, or mistaken.

Naah ;-)
+++++++++++++++++++++++++++++++++++++++

Ponder this perplexing question, Sir Morgans...

Is the glass half full or half empty?



Barnyard BOb - the half fast curmudgeon

"RR Urban" wrote in message
...

Jerry Springer wrote:

The Mooney I flew would gain 1" using the ram air feature. I don't
know if that is standard or how accurate the gauges are but that is what we
always showed.

Jerry
+++++++++++++++++++++++++++++++++++

I'm no expert, but that's probably pretty close.

Dunno about accuracy, but my RV-3
displayed somewhat less. For me...
it's all much ado about nothing since it
has little bearing on any practical ETA.

Barnyard BOb --

===========
Every Mooney I have flown has always gained an inch with filter bypassed. I
don't have my manuals or logbook handy, but I recall that the POH indicated
an inch gain. The models were older Mooneys: M20(F?, don't recall) and
M20J.

YMMV.

Michael Pilla