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larry(at)macsmachine.com
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 Posted: Sat Aug 30, 2008 7:57 am Post subject: Kit Planes accident and reliability article |
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Hi Guys,
The October issue of Kit Planes has a fine article on accidents and
compares a rather large cross section of aircraft and engine types to
the statistical records over several years. Very good read! I was
surprised to find that automotive conversions held up better internally
than the type certified aircraft engines. Problems with automotive
conversions were mostly associated with ignition, fuel system, cooling
systems or the re-drive. When people take the time to do correct
installation and maintenance in these areas, the automotive conversion
will easily match or exceed performance and economy of the
type-certified aircraft engines.
Larry McFarland 601HDS at www.macsmachine.com
do not archive
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frank.hinde(at)hp.com
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| Posted: Sun Aug 31, 2008 9:22 am Post subject: Kit Planes accident and reliability article |
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Hmmmm.....
I think that's a little bit of a sweeping statement there Larry..If you remember I suffered three valve guide failurs in my Subaru conversion..I would say that as I had only 400 hours that was an appalling failure rate..Fourtunately I was able to re-engineer the package and fix a fundamental flaw in the suppliers product, but that's only because I have a lot of experience in this area.
Most folks I fear have little clue about such things, or about killer vapour lock, how to engineer a cooling system etc.
If somebody with my experience can have such troubles (and who bought an engine package to avoid having to mess with the conversion itself) then the average Joe has no chance.
I would be interested to read the article because anecdotal evidence would appear to dissagree with your statement.
Hopefully the market will weed out poor engine conversions...But at a potentially great cost.
Don't get me wrong there are one or two really good auto conversions, but they certainly are not cheaper on the initial installation cost (comparing an Eggenfelner Soob with an experimantal Lycoming clone) and if you add the extra cooling drag of a water cooled engine vs an aircooled (at least on a fast airplane) then fuel consumption is going to be worse....Ok that last statement is fiercely debated...
Where auto conversions really shine is in rebuild costs are much less..But is that really a big factor in the overall cost of an airplane?..I personally doubt it.
Frank
601 HDS Soob 400 hours
RV7a 330 hours IO360 WAAY faster and better MPG than the Zodiac....Also runs on pump gas
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bryanmmartin
Joined: 10 Jan 2006
Posts: 1018
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| Posted: Sun Aug 31, 2008 1:13 pm Post subject: Kit Planes accident and reliability article |
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A properly engineered water cooled installation should have
considerably less cooling drag than an air-cooled installation. North
American was able to get enough thrust out of the cooling system for
the P-51 to almost cancel out the cooling drag. Other manufacturers
who just slapped a big radiator behind the prop didn't fare nearly as
well. Another example of good cooling design is the Spitfire. Neither
the Spitfire nor the Mustang ever had any problems with overheating in
flight. The problem is that most aircraft aren't designed around a
water cooled engine so compromises have to be made to get adequate
cooling.
On Aug 31, 2008, at 1:21 PM, Hinde, Frank George (Corvallis) wrote:
| Quote: |
(Corvallis)" <frank.hinde(at)hp.com>
Don't get me wrong there are one or two really good auto
conversions, but they certainly are not cheaper on the initial
installation cost (comparing an Eggenfelner Soob with an
experimantal Lycoming clone) and if you add the extra cooling drag
of a water cooled engine vs an aircooled (at least on a fast
airplane) then fuel consumption is going to be worse....Ok that last
statement is fiercely debated...
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Bryan Martin
N61BM, CH 601 XL,
RAM Subaru, Stratus redrive.
do not archive.
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Bryan Martin
N61BM, CH 601 XL, Stratus Subaru.
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frank.hinde(at)hp.com
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| Posted: Tue Sep 02, 2008 7:17 am Post subject: Kit Planes accident and reliability article |
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Bryan,
You are talking about 400mph airplanes here (and as A Brit I am very proud you guys chose to use OUR engine in YOUR airplane....). This is VERY different to a 100mph Zodiac.
But also, those radiator installs had thousands of hours of development work behind them. Sure, we MAYBE able to improve the drag characteristics of a radiator but the plain fact is nobody has done it.
There is not one properly engineered radator install out there that you can buy. Now part of this is the design of the airplane itself..Generalll you need a long duct both in front and behind the rad..The engine placed on the nose of the airplane is not conjucive to this.
In the Zodiac its probably a moot point, a little bit of extra drag is not going to make much difference, but a fast airplane like a an RV or Lanceair that extra drag will be significant.
So not arguing improvements could be made, but automotive suppliers have very little incentive to do so.
Personally I would love to see automotive conversions on faster airplanes, but right now for that particular application it really offers no clear advantage over a Lycosaurus.
Frank
Do not archive
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