Lancair 320 ram air?

[ROBIN FLY]

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?

[RR Urban]

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

[Stealth Pilot]

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

[RR Urban]

>
>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 --

[Kevin Horton]

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

[Jerry Springer]

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.
>

[RR Urban]

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 --

[RR Urban]

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 --

[RR Urban]

"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

[Michael Pilla]

"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

[Larry Smith]

"Michael Pilla" > wrote in message
...
[...]>[flush BYB] ===========
> 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

At altitude no big worry about dust and bugs, I wouldn't think. However, in
Missouri where there's lots of particulates and airborne effluvia and
pestilence, I would always filter the air.

[Morgans]

"RR Urban" > 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 ;-)
--
Jim in NC

[Morgans]

"RR Urban" > wrote
>
> Ponder this perplexing question, Sir Morgans...
>
> Is the glass half full or half empty?
>
>
>
> Barnyard BOb - the half fast curmudgeon

Tis easy! Neither half full or half empty!

Jim ( pessimism are us ) in NC

[Dave Hyde]

RR Urban wrote:

> Ponder this perplexing question, Sir Morgans...
>
> Is the glass half full or half empty?

It's twice as big as it needs to be.

Dave 'overdesign' Hyde

[richard riley]

On Sun, 28 Dec 2003 05:03:54 GMT, Dave Hyde > wrote:

:RR Urban wrote:
:
:> Ponder this perplexing question, Sir Morgans...
:>
:> Is the glass half full or half empty?
:
:It's twice as big as it needs to be.
:
:Dave 'overdesign' Hyde


The other half is stored in a redundant, damage resistant container in
a secure location.

[Ray Toews]

On cars,,,of which I had some experience in the decade of the 80's
many cars had very poor positive crankcase ventilation filters.
To my simple mind it always seemed more important to filter the air
going into the crankcase where dust must be removed by the oil filter
as compared to the intake air which spends a VERY short time in the
combustion chamber.
As for me and my airplane we filter the carb heated air and taxi on a
dusty strip with the carb heat ON thus making sure the carb is always
nice and warm and then shortly after applying full throttle on take
off I close the carb heat and I KNOW it will not ice up for a least a
few minutes until I am safely in the air.
Now of course this is all contrary to what I was taught by the flying
club,,,but what do I know.

Ray Toews

On Fri, 26 Dec 2003 22:50:47 -0500, "Morgans"
> wrote:

>
>"RR Urban" > wrote
>>
>> Ponder this perplexing question, Sir Morgans...
>>
>> Is the glass half full or half empty?
>>
>>
>>
>> Barnyard BOb - the half fast curmudgeon
>
>Tis easy! Neither half full or half empty!
>
>Jim ( pessimism are us ) in NC
>
>

[B2431]

>From: richard riley

>On Sun, 28 Dec 2003 05:03:54 GMT, Dave Hyde > wrote:
>
>:RR Urban wrote:
>:
>:> Ponder this perplexing question, Sir Morgans...
>:>
>:> Is the glass half full or half empty?
>:
>:It's twice as big as it needs to be.
>:
>:Dave 'overdesign' Hyde

>
>The other half is stored in a redundant, damage resistant container in
>a secure location.
>
>

Actually due to the capitalistic greed of the Yankee running dog imperialists
only half the water needed by the ever suffering workers.

I couldn't quite work "hegemonists" into that.

Dan, U. S. Air Force, retired

[Craig Morton]

(ROBIN FLY) wrote in message >...
> 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 built a Lancair 320 back in '91. It was the 16th "fast-build" kit
shipped from the factory. As I recall, the builder's manual for these
early models had few details regarding engine installation. They had
a diagram of a simple airbox that could be constructed out of
fiberglass (which suggested incorporating a foam air filter), but no
other specifics. I ended up making one from sheet aluminum with a
ram-air inlet (unfiltered).

I think there is now a factory built airbox for the plane, but early
examples will vary (it's a homebuilt after all).

Yes, the lack of a filter will probably shorten the TBO, but plenty of
people go without 'em.

Craig.