Once in a while you have
an experience that so
opens your eyes you
suddenly realize how
little you know about
certain segments of
aviation. And its
exciting! It's damned
exciting to suddenly be
soaking up raw knowledge
in the form of equally raw
experiences which add so
much to your understanding
that the effect is
immeasurable.
I just
had one of those
experiences and it kept me
awake for days designing
airplanes in my dreams.
What has me so fired up?
I just
flew the Sherpa! You
know...that humungous bush
bird which showed up at
Oshkosh last year and
looks like a Super Cub on
steroids. It's the one
with a severe foot
condition.
More
than just flying it, I was
forcefully inserted into
the world of hard core
bush flying for which the
Sherpa was designed. When
I returned home I babbled
on like an idiot about the
experience for hours but
found my tales were split
and focused on two
different subjects: The
first was the Sherpa
itself, but I found it did
no good to speak of the
airplane without putting
it in context. It does no
good to talk about a bush
or utility airplane
without truly
understanding the world in
which it lives because
very few of us really know
what that world consists
of. We may think we know
about bush flying but
believe me, we don't.
I
learned how little I knew
about bush flying and what
it demanded as soon as I
walked up to the Sherpa's
birthplace and company
headquarters; Byron Root's
hangar complex, which was
located mid-field on his
private strip in the
suburbs of Portland,
Oregon. There was maybe
350 feet of runway
extending past the hangars
in both directions with
tall trees at one end
while the last 100 feet at
the other end dropped off
at a steep angle before
disappearing entirely at a
small cliff. The surface
snaked through the trees,
bucking, twisting and
turning as it went, and
had water standing in the
low spots. And this was
their main airport!
Byron
has been building super
bush planes as a side line
(he's actually a real
estate developer) for
years because that's what
he and his friends do.
They jump into their
airplanes and disappear
into the Oregon wilderness
hunting and fishing in
places which have never
seen a road. That means
landing where you possibly
can which in turn means
accepting runway lengths
and surfaces which are an
accident of nature, not
the result of planning or
preparation. Both the
pilot and the airplane
have to be able to handle
what nature hands out. The
only absolute known in
those situations is that
there will never be enough
runway and what there is
will be really rough. As I
found out, sometimes it is
rough beyond the
imagination.
In all
his years bouncing in and
out of river beds and
canyons, Byron learned
from experience what it
takes in terms of the
hardware to both get in
and not break. More than
once he's had to walk
many, many miles for help
after landing somewhere
and having the airplane
break. In conversations
with him certain subjects
continually resurface and
those are what formed the
seeds for the Sherpa
development.
His
list of "musts" for a
serious bush plane
include:
· Lots of power
· Lots of wing
· Lots of flap
· Lots and lots of
structural durability
He
arrived at these through
continually flying
airplanes deemed to be
bush planes and finding
what doesn't work and what
breaks.
For
instance, he doesn't like
spring gear and aluminium
airplanes because the gear
throws up rocks which tear
up the tail and the gear
is too easily eaten by
hidden rocks and holes. He
prefers rag and tube
because it is less likely
to suffer unflyable damage
(duct tape is great
stuff!) and is easier to
repair and beef up.
In his
continual upgrading of his
own Super Cub, he kept
breaking parts and beefing
them up, changing and
evolving the airplane
until today it boasts a
six cylinder, 0-540
Lycoming and what is
essentially a redesigned,
beefed up fuselage.
He and
his friends take their
flying so seriously
they've enlisted the aid
of a radar gun to evaluate
aircraft slow speed
performance. Using the
radar gun they determined
that many of the much
vaunted short field
airplanes, like the Helio
Courier, may be able to
fly really slowly across
the airport, but when it
comes time to land on an
extremely short strip,
they have to come in 5-7
knots faster because they
have to put the nose down
to see the end of the
runway.
As I
was to find out myself,
the ability to see the
exact spot you want to hit
is paramount to short,
rough field work. And you
have to use both words
together, "short" and
"rough" because that's
what defines most bush
strips for the airplanes
that utilize them on a
regular basis.
A few
hours after hooking up
with Byron we were
somewhere out in the
eastern Oregon wilderness
which looks surprisingly
like a desert, but after
drenching rains, it was
all mud. We were sitting
on top a small mesa with
the engine idling and out
in front of me, maybe 250
feet away, was a distinct
semi-ditch where an old
stock road had eroded into
sharp edges. Half way to
the ditch was a narrow
swale I'd have to ride
through. The entire
undulating surface was low
sage brush and mud. Lots
of mud.
Byron was sitting in
the back seat with no
control stick and no
throttle. He had no way to
correct if I screwed up.
The best he could do was
scream into the intercom.
I was going to have to get
off on what was in front
of me and then come back
around and land on what
was behind me. The 150
feet or so behind me
started at a sheer cliff,
went up hill for 30 or 40
feet, and then plateaued
with the ditch at the far
end. We had about 400-500
feet of runway, mud for a
braking surface, and very
little wind on the nose to
help.
Was I
nervous? Surprisingly, no,
I wasn't. I'd seen Byron
make three approaches and
landings and for some
reason, the airplane gave
me so much confidence I
wasn't worried. Byron must
have felt the same way
because I was the first
person outside his company
to occupy the sole pilot
seat and he was turning me
loose in what I thought
was a marginal situation.
Later I was to find that
wasn't the case. 500 feet
wasn't even close to being
marginal.
Byron's
voice was somewhere in the
back of the Bose headsets
(which are an absolute
necessity!) but I wasn't
hearing it. As the
throttle went in, I was
listening to my own voice
inside my head coaching me
as if I was a student.
With 400 horses streaming
out of the IO-720 Lycoming
and over the tail, I just
held on and tried to hold
the tail wheel just barely
out of the mud.
There
is no way you can imagine
what it feels like to be
bounding over rocks and
sage brush and down into a
swale, while hanging on to
a raging bull. My mind was
speaking to my right hand,
asking it to keep gently
applying back pressure,
while willing the airplane
off the ground and away
from the awful beating we
were taking.
The big
tires soaked up an amazing
amount of what I knew were
airplane destroying
impacts, then we bounced
once and were airborne. I
held that attitude for a
second, letting the
airplane accelerate until
it felt as solid as it had
at cruise, before banking
steeply around as we came
out over the yawning edge
of a small canyon. As I
banked I glanced at the
airspeed for the first
time. 55 knots! I thumbed
the electric trim on the
stick forward for a second
and grinned. At that speed
the airplane felt
absolutely stone solid.
The
confidence the Sherpa gave
in that situation was
truly awe-inspiring. I
don't ever remember an
airplane that felt that
good that slow or that
early in a flight It just
seemed so right that I
immediately felt
comfortable, which is not
the way I usually feel
before even making the
first landing. I'm not one
of those super pilots who
are good in every airplane
and this airplane couldn't
have been further removed
from my usual mount, a
Pitts Special, if it
tried. Here I was, 55
knots, 100 feet over a
desolate wilderness in a
30 degree bank in a
machine that weighed
nearly two and a half
times what my Pitts does
and I felt good about it.
Really good. That says
something for the
airplane.
I
stayed low and bent it
around in a tight pattern
heading for the other end
of our so-called runway,
which was nothing more
than a piece of raw
wilderness. I punched the
rest of the flaps out
(40°, slotted-Fowlers) and
trimmed for 50 knots as I
turned final.
The
vertical edge of the mesa
and the short, up-hill
ramp which was my intended
touch down spot was well
up in the windshield. It
was as if the airplane had
no nose the visibility was
so good. Also, the
airplane was so speed
stable, I found cross
checking the airspeed was
a waste of time. As long
as I didn't move the nose,
the needle stayed stuck in
one place. I trimmed it
back to 45 knots, licked
my lips and visually
fixated on my landing
stop.
Not
once in my entire life
have I ever been in that
type of situation, one
which demanded the
airplane hit exactly where
I wanted and for which the
consequences of failure
were so great. Land short
and we'd be a jumbled pile
of junk on the edge of the
mesa (or so I thought at
the time) and the
multi-million dollar
investment of Byron Root
and his partner Glen
Gordon would be gone. Land
long and I'd go slithering
through the mud into the
road/ditch unable to stop
(or so I thought at the
time).
I flew
an abbreviated final but
it took only a few seconds
to realize the airplane
absolutely followed the
throttle, what little I
was using of it. We
weren't grinding along
nose high, with the power
screaming to keep us in
the air. Rather, we were
simply in what would have
been a steep glide but we
were using just a little
power to flatten it out
and overcome the drag.
At 45
knots everything is
happening in slow motion
and it seemed as if I had
all day to gently move the
power in and out to draw a
straight line to my
landing spot. Then,
suddenly we were there and
the spot loomed large in
the windshield. I gently
brought the nose up and
eased the power off (Byron
had demonstrated it needed
just a bit of power to
flair). We flopped into
the mud with me sucking
the stick into my gut and
the airplane had nearly
stopped rolling before it
dawned on me to get on the
brakes.
I let
out the breath I had taken
on downwind and grinned
about as wide as I believe
I have ever grinned. What
an absolute, positive,
unqualified blast! I
looked ahead at the
road/ditch I was worried
about and realized I had
more distance left to
takeoff than I had the
first time. We hadn't used
much over 150 feet on
landing and I didn't know
what I was doing! That
says a lot for the
airplane.
I made
a bunch more take-offs and
landings on top that mesa
before trading places with
Byron so he could show me
how the airplane really
flew.
I was feeling like a bush
pilot until we dropped
down into a canyon and
started buzzing along
right over a serpentine
river 1,000 feet below the
rim. We did our eagle
routine and twisted and
turned right along with
the river. As we did,
Byron was pointing out
gravel bars and small
spaces along the bank they
used as landing spots
while fishing. That's when
I knew I was no bush pilot
and why Byron was so
willing to let me flop
around in the mud on top
the mesa...the spots he
was pointing out weren't
large enough or smooth
enough to orchestrate a
crash, much less a
landing. At least that's
what I thought.
Just to
prove a point, Byron
pointed out a small speck
of gravel sticking out of
the water and said that
was a good spot for
steelhead fishing. He ran
out all the flaps, pulled
up over a rock ledge
sticking out of the side
of the canyon, floated
around in a tight turn and
dropped down close to the
surface of the water. From
the back seat, I never saw
the gravel bar until our
big baloney tires crunched
onto it at the edge of the
water. We bounded along
over the incredibly rough
surface for less than half
the length of the gravel
bar. I paced off our
landing roll as 110 feet.
We were two people, 85
gallons of gas, 65° F and
3,500 ft MSL. I had
trouble pacing off the
distance because the
surface was comprised
entirely of water-worn
rocks the size of
cantaloupes and I was
afraid I was going to
break an ankle!
This
was the kind of surface
that, according to Byron,
eats stock Super Cub
structure and it was easy
to see why. Even with fat
tires, the Cub's structure
just wasn't designed for
those kinds of loads,
especially around the tail
post.
Byron
also says fully loaded to
4,750 pounds (2,200 pounds
usable) the airplane will
still get into or out of
anywhere you'd dream of
putting a Super Cub and
loaded to lower weights
can go places you wouldn't
dare take a stock Super
Cub. In most situations it
will even out fly his big
engine Cub.
Undoubtedly the most
impressive part about the
airplane is the ease with
which a pilot could learn
to handle it in the bush
environment. The controls
are very normal feeling,
meaning neither light nor
heavy and the airplane
responds surprisingly
quickly for an airplane
that size. They have a
number of aerodynamic
changes in the works to be
completed before
certification which
include a longer tail
moment to take care of the
reduced tail efficiency at
full flap extension and a
larger wing with more
flap. Their aerodynamicist
says they will trim
another 6 knots off the
stall speed with the new
wing. Considering they
have radared the airplane
as flying 34 mph
(power-on), a 6 knot speed
reduction would make the
airplane even easier to
get in and out. In fact it
would be the next best
thing to a helicopter,
which it is already. Byron
says their goal is an
airplane that can get off
in less than 100 feet,
zero wind with 500 pounds
on board. As it is, with a
ten mph wind they can do
that in 72 feet!
It's
this last point, the
comparing of the
airplane's utility with
that of a helicopter, that
continually bounced
through my mind during the
day. With the possible
exception of landing on
roof tops and tennis
courts, the Sherpa could
do probably 80% of what a
helicopter does with a
fraction of the purchase
and maintenance cost and
with much less chance of
equipment breakage in the
field.
When we
were enroute back to home
base I noticed a curious
change had taken place in
my mind. I found myself
thinking like I used to
when flying a Super Cub on
skis after a major snow
storm. In that situation,
with skis and lots of
snow, everything flat is a
runway. You can land
everywhere. On the way
back with the Sherpa, I'd
look down and see a small
flat spot and think,
"...we can land in that
easy..." It was a very
comforting feeling.
And
when I saw a small remote
town without a runway, I
realized it didn't need a
runway for emergency
medivac situations. There
were a dozen flat spots
within city limits where
the Sherpa could land with
no sweat. A football field
becomes an
airport...literally!
The
Sherpa is also faster than
all but the most exotic
choppers. We were showing
120 knots, which at that
altitude and temperature
was a shade over 140 knots
true. Incidentally, while
we were cruising along at
altitude, the visibility
in all directions was
amazing. The nose is way,
way down and the glass
doors let you look
straight down. Byron said
the fish and wild life
boys who were evaluating
the airplane would go for
the standard 29 x 11 x 10
tires because they
wouldn't block as much of
their view. He also said
they were working on a
curtain/shade for over the
pilot's head because he is
out in the Plexiglas and
gets pretty hot.
Ignoring the airplane's
ability to work in the
bush, I'd be very
surprised if government
agencies, both ours and
other country's, didn't
jump on this bird as one
which could replace
helicopters and other
fixed wing airplanes for a
lot of use where
ultra-short runways aren't
even a factor. At 45 knots
it is slow enough to do
bird counts, pipeline
patrol, border
surveillance and on and
on. It is also an airplane
almost anyone can fly
easily since its ground
handling is so benign.
I think
these guys are really onto
something!
Sherpa Tech Specs
Structurally the Sherpa is
a rag and tube fuselage
and metal wings (airfoil
43015A Modified) with 120
gallon (to be increased to
180 gallon!) fuel tanks.
But this is a serious tube
fuselage...the longerons,
for instance, top and
bottom are 1 1/4 "x .058".
Everything about the
airplane is built tough to
take a beating.
The
landing gear, besides
being massive, utilizes a
shock absorber along with
the bungees to dampen
rebound. This shock is not
an air/oil oleo because
that wouldn't let the gear
come back to rest quickly
enough after hitting a
rock. The gear might still
be partial extended when
it hit the next one. The
Sherpa shock uses urethane
washers which have a more
immediate response.
The
elevator trim is electric
utilizing dual screw jacks
and the flap motor looks
big enough to move a
house. It takes about 9
seconds for extension and
ten to retract them.
The
Lycoming IO-720 engine is
an enigma to most of us
because most of our
knowledge of it comes from
its use in the Commache
400. There it had a less
than enviable reputation
largely because it was
tightly cowled and prone
to over heating. The
Sherpa team has utilized
the experience of numerous
Piper Brave ag operators
in the area which swear by
the engine. They say they
go to 2,000 hr TBO will
few problems. While we
were flying the airplane,
in ten hot-starts, it
never hesitated.
They
have gone through a number
of propellers and have yet
to finalize the selection.
The four-blade they had on
the airplane during our
evaluation wasn't putting
out as much thrust as
their earlier Hartzell
three-blade had.
Some
foreign governments have
expressed an interest in a
turbine installation, but
no one at Sherpa is wild
about the idea. Besides
doubling the cost of the
airplane, they say its not
going to improve its
performance enough to
justify the cost except
possibly on floats.
The
tires can be either the
standard 29 inch, aircraft
versions or the baloney
skin tundra tires like we
flew. Those are actually
four-wheel truck tires
with the tread ground off
mounted on 15 inch
aluminum, one-ton Chevy
truck rims. They say they
have been flying that type
of tire for nearly 15
years with little or no
problems. The brakes are
two, three-spot calipers
on each wheel.
The
tailwheel is a standard
500 x 5 main gear unit and
the tailwheel assembly is
something that is
undergoing continual
revision. Because of the
airplane's weight and the
surfaces they intend to
work off of, nothing
commercial has stood up so
they've left a lot of
tailwheels up in the
canyons. Presently they
are testing their own
assembly which utilizes a
CNC'd 7075 pivot with a
4130 weldment fork.
The
airplane is currently
configured for a 1-2-2
seating arrangement but
the seats are actually
wide enough for three
across in a tight squeeze.
The single front seat will
be changed to a side by
side arrangement for those
who want it along with a
sliding, side opening door
in the rear of the
fuselage for passengers,
cargo or litter cases.
Knowing what little I know
about bush flying at this
point, I'd rather have the
single pilot seat so both
sides of the nose are
visible on landing.
The
floors are a honeycomb
sandwich and production
airplanes will have a
multi-use track system
which would allow easy
removal or repositioning
of seats as well as cargo
tie down. The cargo space
aft of the pilot's seat
will accept the equivalent
of five 55 gallon drums.
Useful load is just short
of 2,200 pounds!
It's
some kind of hoss!
Wing
Span 42.6' (present wing)
Wing Area 258 (to be
increased)
Fuel Capcity 121 Gal (180
in production)
Empty Weight 2585 lbs
(includes survival gear,
tools, etc)
Gross Weight 4750 lbs
Useful Load 2165 lbs
Performance
Takeoff roll (3,000 lbs.,
0 mph wind) 135'
Landing roll (3,000 lbs.,
0 mph wind) 145'
Takeoff roll (3,000 lbs.,
10 mph wind) 72
Landing roll (3,000 lbs.,
10 mph wind) 77'
Takeoff roll (4,750 lbs.,
0 mph wind) 396'
Landing roll (4,750 lbs.,
0 mph wind) 282'
Takeoff roll (4,750 lbs.,
10 mph wind) 272
Landing roll (4,750 lbs.,
10 mph wind) 191'
Cruise speed, 75% 160 mph
Fuel burn, 75% 20.1 gph
Economy cruise 15.5 gph