to lay out the considerable cash for a welded metal one by a
commercial outfit.
However, I was seriously concerned after looking at Victor’s
design that it might lead to some unfortunate accident.
Not all Cessna flat-spring gear legs are at the angle in
the picture accompanying the article, where it appears
that a majority of the plane’s weight will bear on the
“wedge block.” If the angle is steeper, and the “wedge
block” has a low coefficient of friction, a large majority
of the aircraft’s weight (on the side being jacked up)
will bear on the two smaller angled blocks of wood. In
Victor’s design, these are only glued and screwed with
1.25-inch screws, indicating a screw penetration into the
wedge block only about 1/2 inch.
I suspect that Victor’s blocks have served him well on
his Cessna 150, but if someone makes a similar device for
a Cessna 185 and doesn’t use hardwood and doesn’t glue
the blocks, those two small screws are going to tear out
and the plane will come crashing off the jack stand.
I made some quick calculations based on simple
assumptions—one-third of an 1,800-pound aircraft weight
is on the jacked up leg; one-half of that is on the wedge
block; the other one-half is held by the angled blocks; and
the taper on the legs is about 3 degrees—and I calculate
that each of the two angled blocks will have to hold 3,000
pounds of side force. Some glue and two small screws is
not enough!
The jacking blocks that I made had a wooden wedge
block like Victor’s (made of oak), but for the angled side
blocks, I attached a 4-inch-long piece of 3/4-inch by 3/4-
inch angle iron, by bolting it completely through the
wedge block with a single 5/16-inch bolt. A pair of these
angle-iron side-pieces spaced several inches apart would
“automatically” align to the taper on the gear leg.
Please understand that I’m not criticizing Victor’s
ingenuity, but I’m worrying that his design is just not
strong enough. To illustrate just how strong that wedging
action is on the side blocks, I know of a Cessna 172 that
was jacked up with one of the commercial all-metal
jack pads, and after the annual inspection the pad was
inadvertently left in place. The plane was flown on a
2,000-mile trip soon after, and upon return, the metal
pad was still in place—requiring a hammer to remove it
from the gear leg. (Of course, this doesn’t say much for the
preflight inspections done during that weeklong trip, but
that is another story.)
Thank you for considering my concern.
Rick Putnam, EAA 545457
Redmond, Washington
Regarding Fuels for the Future
I read the article “Fuels for the Future” in your February
2009 issue with interest. I own a 1946 Aeronca Chief
with an autogas STC that would run just fine on regular
New Lifetime Members
Stein Bruch (EAA 643063), Rosemount, Minnesota
Joe Cobb (EAA 423867), Nashville, Tennessee
Michael Coster (EAA 328430), McLean, Virginia
Stacey Lohr Graves (EAA 879945), St. Louis, Missouri
Jed Gregson (EAA 517516), Rosemount, Minnesota
Timothy Kent (EAA 585161), San Antonio, Texas
Sabrina Lohr (EAA 879948), St. Louis, Missouri
John Roach (EAA 729220), Minneapolis, Minnesota
Douglas Willey (EAA 601384), Chicago, Illinois
autogas, if it did not contain ethanol. There are thousands
of airplanes out here, from Piper Cubs to Cessna 182s,
that could also use autofuel with the proper STC, were it
not for its ethanol content.
Why not just draw off sufficient fuel at the refinery to
supply the aviation market before adding ethanol for the
automotive market? Then, with our autogas STCs in hand,
we could all fill up with ethanol-free autogas and go fly!
Greg Harris, EAA 224811
Kirkland, Washington
Earl Lawrence Responds…
Thank you for reading the article and for your insightful
question.
Like many things in life your simple suggestion gets
complicated when one attempts to put it into practice
because of economics, various laws, and the ever-present
legal system.
On the economic front, the price to deliver fuel as you
suggest is prohibited because of the very small market; 80
percent of the gasoline used in aircraft, autogas or avgas, is
used by less than 10 percent of the aircraft. The vast majority
needs 100-plus octane fuel.
EAA looked into facilitating supply just as you suggest in
Wisconsin as a test case. The price per gallon, because of
the extra costs for storage and distribution for such a small
amount of fuel, exceeded the cost of 100LL. So, one can do
it, but because you have to have a segregated storage tank
and then truck it separately from the normal distribution
process, which incurs special handling fees, the cost goes up
to more than 100LL. Also you would need a company who is
willing to take on the project. Even with EAA paying for the
storage and gathering all the orders, it just did not work out
economically.
