Budget Retracts - Anyone own a Sierra or Comanche 180?

wrote:
John Theune wrote:
: I'd really like to see some number to support your conclusion. By my
: estimates 100 hrs * 11 gals per hour = 1100 gal per year. RG decreases
: fuel need by 5% or 55 gal * $3.50 = 192.50 per year in fuel savings.
: From the numbers throw about by my aircraft owning buddies the delta in
: ownership costs for a retract are much more then that.

: Assumptions in above: Fuel burn is about the same for 180HP engines in
: Comanche 180 and 172s with 180HP engine. Increased speed reduces need
: for fuel by 5% by higher speed in cruise, climb fuel burn is the same.
: Big YMMV is added

Not to be too argumentative, but 5% might not be the right number. A quick
example:
http://www.risingup.com/planespecs/i...plane432.shtml
http://www.risingup.com/planespecs/i...plane427.shtml

That's a PA-28-180 vs. a PA-28-180R. Cruise of 119 kts vs. 141 kts. That's
18% improvement in speed. Others are similar around 15%. So, multiply your fuel
savings by a factor of 3 and you get $600/year. That's starting to sound more in line
with the additional costs of a gear swing every year, some more lube, and a
replacement part averaging every 5 or so.

Just food for thought.

-Cory

--

************************************************** ***********************
* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
************************************************** ***********************

Very good, I was hoping somebody could come up with better numbers then
I had. It looks like from your numbers the fuel savings come close to
the extra maintenance costs so the insurance costs would swing the
balance toward the FG model cost wise. I think the extra "sex appeal"
of the RG might swing it back toward the RG side, but bottom line you
can't argue for the RG just on cost savings over FG.

Very good, I was hoping somebody could come up with better numbers then I
had. It looks like from your numbers the fuel savings come close to the
extra maintenance costs so the insurance costs would swing the balance
toward the FG model cost wise. I think the extra "sex appeal" of the RG
might swing it back toward the RG side, but bottom line you can't argue
for the RG just on cost savings over FG.

Sorry, I'm late to this thread, but it's an interesting point you bring up.

However, it's only applicable to what we might call "legacy aircraft" --
Pipers, Cessnas, Beechcraft, Navions, etc. All of the "modern" aircraft
(Cirrus, Lancair, Diamond) are going with stiff legs, and don't appear to be
paying much of a price penalty for doing so.

Anyone care to venture a guess as to how much faster an SR-22 (for example)
would go with retractable gear?
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

In article u9%Lf.822635$xm3.75681@attbi_s21,
"Jay Honeck" wrote:

Sorry, I'm late to this thread, but it's an interesting point you bring up.

However, it's only applicable to what we might call "legacy aircraft" --
Pipers, Cessnas, Beechcraft, Navions, etc. All of the "modern" aircraft
(Cirrus, Lancair, Diamond) are going with stiff legs, and don't appear to be
paying much of a price penalty for doing so.

Anyone care to venture a guess as to how much faster an SR-22 (for example)
would go with retractable gear?


Consider the lancair aircraft.

The ES, with 210hp will supposedly do 200mph at 8000'
The ES with 310hp will do 225 mph at 8000'
Both of these are fixed-gear.

The lancair legacy, with the 310hp and retract will supposedly do 276mph at 8000'
The fixed-gear legacy, with 200hp will supposedly do 210 mph at 8000'

so, maybe the SR-22 would gain 30mph or so with a retractable...

--
Bob Noel
Looking for a sig the
lawyers will hate

The lancair legacy, with the 310hp and retract will supposedly do 276mph
at 8000'
The fixed-gear legacy, with 200hp will supposedly do 210 mph at 8000'

so, maybe the SR-22 would gain 30mph or so with a retractable...

That's pretty significant. I suppose liability concerns are preventing them
from considering folding gear?
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

Jay Honeck wrote:
The lancair legacy, with the 310hp and retract will supposedly do 276mph
at 8000'
The fixed-gear legacy, with 200hp will supposedly do 210 mph at 8000'

so, maybe the SR-22 would gain 30mph or so with a retractable...


That's pretty significant. I suppose liability concerns are preventing them
from considering folding gear?

I'd think the concerns about their customers affording insurance would
be greater than any concerns about manufacturers liability.


Matt

With the old fixed gear setup 30mph for gear might be about it. With
the newer more streamline gear, it is less. Retractable gear is an
anethema. It needs to be tested, annualed and repaired and the pilot
needs to remember to deploy it. It's unavoidable on some planes, but if
you can get by without it, do so. Your life will be a lot easier. The
faster you go, the more retract will gain you, that is true. On a slow
airplane it's not much.

On 2006-02-25, Jay Honeck wrote:
Pipers, Cessnas, Beechcraft, Navions, etc. All of the "modern" aircraft
(Cirrus, Lancair, Diamond) are going with stiff legs, and don't appear to be
paying much of a price penalty for doing so.

Well, apart from the Diamon Twin Star which has wobbly wheels.

--
Dylan Smith, Port St Mary, Isle of Man
Flying: http://www.dylansmith.net
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