Let’s consider light amphibious aircraft – the boathull variety, not floatplanes
– but including both freshly designed, fully built light sport aircraft
along with kit aircraft born of the ultralight heritage.
In the last year, the exceedingly handsome Icon A5 has made quite a splash, literally
and figuratively. However, the A5 is more than a year away from first deliveries
and an order placed today might not be delivered until 2011 or later. Another LSA
amphibian called the Mermaid was designed and introduced by Czech Aircraft
Works of SportCruiser fame. Although five are available in the country, sales have
yet to take off.
Another popular American seaplane, the SeaRey, is moving toward ASTM
approval but remains a kit that asks several hundred hours of a builder’s time. The
simpler and faster-build Aventura models also remain available; this design has
been on the market for many years. Either kit is less costly than a fully built aircraft,
but all seaplanes have loftier price tags to cover their ability to operate on land
or water. Let’s put the cost of LSA amphibians in perspective: The cost of adding amphibious floats to a certified 4-seat general aviation aircraft can be greater than
the price of an entire Light-Sport Aircraft amphibian.
Somewhat behind the scenes compared to the A5 or Mermaid, the little SeaMax
M-22 has won its Special Light-Sport Aircraft approval and started making sales.
With the sleek looks of modern composite LSA, the SeaMax is sized and shaped closer
to ultralight dimensions. The A5 and Mermaid are each pushing against the top
of the allowed weight range of 1,430 pounds for seaplane LSA, while the SeaMax
weighs significantly less. In light aircraft a significant weight difference can bestow
handling and performance advantages.
Light on Its Sponsons
Compared to the A5, Mermaid or SeaRey for that matter, the SeaMax is remarkably
light. When it first arrived in the USA, the SeaMax weighed in at a positively
diminutive 1,144 pounds gross, an unheard-of low weight for a deluxe,
fully enclosed amphibian that looks this good. As it won approval under the ASTM standards for
Light-Sport Aircraft, SeaMax increased capacity to 1,320 pounds. However, since
LSA floatplanes are allowed to weigh 1,430 pounds, the SeaMax still comes in 110
pounds lighter at gross and does even better in empty weight comparison. All this
makes for more useful load.
The amphibious SeaMax tips the scales empty at 750 pounds, giving it a 570-
pound useful load. Even with a full load of 25 gallons of fuel, the SeaMax still boasts
a payload of 420 pounds, enough for two beefy 200-pound occupants plus 20 pounds
of carry-on gear.
The SeaMax M-22 appears physically small from the outside.With the wing chesthigh
for most people, the SeaMax looks tinier than it is and the light weight surely
contributes much to the relative high performance of this flying boat. Light and
small it may seem, but when you step inside, you’ll find the interior to be surprisingly
Created by Brazil’s AirMax Construcoes Aeronaticas, the SeaMax is designer
Miguel Rosario’s 22nd design and his experience shows. The M-22 is very well
thought out with many details not present in other LSA. Rosario,
whom I met at Sun ‘n Fun ’07, said that it was first designed for a
wealthy Brazilian businessman and that man wanted it to be a
Since its introduction, SeaMax sales have reached 90 units flying
worldwide, mostly in Europe where government approval was possible
some years ago. An established dealer in Norway sells the most
but units presently in the U.S. are available for quick delivery. Five
SeaMax LSA are registered in the U.S.
The AirMax’s work to meet ASTM standards relied on Rosario’s
long design history, but he received engineering assistance from a Mr.
DeCastro, widely revered as one of the greatest aeronautical engineers
in Brazil. Rosario also had a serious and talented U.S.-based
partner in Carlos Bessa – who conveniently speaks Portuguese, thereby
aiding communications with AirMax on a daily basis. Bessa is the
quality control manager in the USA for AirMax and sources parts
from Aircraft Spruce, Warp Drive, Lockwood Aviation, Gulf Coast
Avionics and similar suppliers.
The more closely you examine the SeaMax, the more you realize
how well thought out and well finished it is. A technically astute
friend, Matt Taber, observed how small and efficient the landing gear
is, a marvel of few parts that helps restrain weight. Taber also noticed
the numerous stainless steel components used, among other applications,
to secure the horizontal tail plane after shipping. All work
appears beautifully executed.
Other clever ideas include an intake at a wing leading edge opening
that directs air to the hull’s step location to help “unstuck” from
the water’s surface. When the canopy is open, you can remove the
instrument panel top for easy access to the instrument wiring and
plumbing. Further, when that canopy is open, you can see an aluminum
tube perhaps a foot long well forward in front of the passenger.
This allows placement of some lead for additional weight should
the pilot not weigh enough. The Sea Max has a minimum pilot weight of 140 pounds;
lighter solo pilots would add ballast weight. Once the tinted canopy is closed, you no
longer see the tube.
An amphibian is more complex than a landplane, period. Retractable gear, water
rudder, a bilge pump and sponsons result in more to manage along with considerations
of hydrodynamics in addition to aerodynamics. Yet many pilots enjoy the task
and thrive on the added freedom amphibious flying can bring.
Electromechanical landing gear takes about 9 seconds to fully retract. Lights illuminate
the gear position and strategically placed convex mirrors can provide visual
confirmation. SeaMax provides a digital flap position indicator, digital trim position
indicator, electrical fuel boost pump, dual wing landing lights, plus dual throttle
levers and brakes.
The SeaMax’s interior comfort is excellent, with a
slick, speedboat-like finish. Cabin width also belies
the diminutive-appearing exterior; at 47 inches, the
SeaMax is half a foot wider than a Cessna 172. The
canopy optics are excellent and you have 45° aft visibility
through quarter windows.
Leveraged door latches move in a small range and
are therefore firmer to operate and latch with a very
secure feel and sound. The door lever hardware is a
simple and light system with an added little touch –
the interior portion of the door handle has a pointyend,
which is thoughtfully bent inwards so you don’t
snag your clothes on it.
In addition to air vents in the canopy — the common
half-cup-shaped, flip-out ones – the SeaMax has
a second set near your head, tucked away in the
wing root area. The interior ones resemble those on
I found the seat belts challenging to adjust; the
adjustment buckles are too close to the seat sides.
This wouldn’t matter if you sit in the same seat all
the time, but it’s awkward when a different-sized
person tries to tighten or loosen the belts. Since my
flight, the company has found a domestic source for
seat belt systems and reports buckle access problems
When taxiing on land with the canopy open, the
hinge components proved robust; even on a bumpy
turf runway, the canopy moved very little. This provides
plenty of airflow for warm days.
However, the reach to pull the canopy
down requires you to loosen or slip off
your shoulder belts. Alternatively, Bessa
said you could add a strap to the canopy
for easier use.
The 100-hp Rotax 912S easily powered
the SeaMax on land or water.With Bessa
flying, we zipped around on the water at
45 mph. The SeaMax makes a great little
speedboat using only 2,800 rpm to
sustain a brisk pace. Turning in this configuration,
a pilot would employ the
water rudder — which extends from
inside the air rudder (the same as it does
on the Mermaid) – and demands opposite
aileron to keep from sticking a sponson
too deeply in the water.
Rising Off the Water
On full application of power some
water spray may contact the prop so the AirMax utilizes
a Warp Drive metal-reinforced leading edge on
the propeller. Because the SeaMax is a small airplane,
when sitting still in the water, the cockpit side
rails are only inches above the water line, and the
bottoms of the occupant seats are below the water
line. Therefore, while it may be possible to fly in
some waves with experience and good technique, I
consider this a smooth-water airplane. I heard
reports of operations in 1-foot waves, but I believe it
would be uncomfortable when you slowed to idle
speeds in such swells unless you have considerable
experience with the SeaMax.
Using Bessa’s takeoff technique I applied full
power and held the stick full aft until breaking
ground. As the nosewheel lifts, you relax the backpressure
and let the plane fly itself off the surface.
Rotation occurs at about 45 mph indicated on the
Dynon digital PFD. Climbout at 70 mph produced
about 1,000 fpm initially. The SeaMax sustained
climb at about 700 fpm with 10° of flaps.
Repeating the land takeoff on water was similar
except you let it fly off the water with such vigorous
control. The SeaMax’s hull gets on the step in about
100 feet, says AirMax. With continued acceleration,
takeoff follows in another 200 feet when flying solo,
or another 400 feet when flying dual.
During landings with full flaps the aircraft
approaches at 50 mph. A good downwind speed is 75
to 80 mph; this produces about 500 fpm down with
the throttle at idle thrust or about 2,500 rpm.
Water touchdowns proved very straightforward.
The SeaMax responds very well as a boat.
Touchdown was at about 60 mph and it immediately
started tracking straight and true. As I slowed
down, Bessa advised me to pay attention to the transition
from airplane to boat. He says it is essential to
keep the stick full aft to prevent porpoising and possible
Other pilots who have flown the SeaMax believe
takeoff and landing operations are easier on water.
Maybe that’s because of the openness of landing on
lakes compared to the constraints of hard-surface
landings with fixed boundaries.
Landing on land means you have to make sure the
wheels are down, of course. The action is easy in the
SeaMax, thanks to electromechanical gear using an
overhead-retracting knob. Three green lights at the
top of the panel confirm what you can also visually
check in small convex mirrors on the sponsons, though
you may have to raise a wing to have the
reflection of wheels against the sky and not obscured
by ground clutter.
For water landings, it appears best to use an attitude
landing technique where you establish a speed
via angle of attack and wait for contact. Certainly
this is the advised method when landing on glassy
water where reflection makes it very difficult to see
precisely when to flare. The steady descent to touchdown
feels quite firm on the boathull, but Bessa indicates
the structure easily stands up to the job.
Let’s face it. Seaplanes often become more sluggish
than their land-based siblings because of a considerable
extra weight hanging well below vertical center
of mass. Light-Sport Aircraft amphibians will be better
than heavier general aviation seaplanes, but the
SeaMax is above average in its class.
In a general way, the SeaMax reminded me a lot of
the Flight Design CT series (or several other
high-end LSA) in that each machine is a “performance
LSA.” My analogy of a Cessna 172
being a “sedan” and the CT being a sports car
brings nods of agreement from others with
experience in both. Flying a SeaMax evokes a
Like any vehicle in the “performance class,”
it may take a bit longer to handle it masterfully.
After my first two flights in the SeaMax,
I was not comfortable enough to take a passenger
in the airplane. Bessa’s partner,
Malcolm Jones, an experienced pilot himself,
said he felt similarly at first. Yet after my
third flight and accumulating nearly 4 hours
I began to feel much more comfortable in the
SeaMax. Given insurance industry requirements
to get at least 5 hours time in type,
most experienced pilots would become comfortable
with the SeaMax in that time.
The SeaMax joystick is nice and light. I
wandered a bit as ailerons and elevator were easier
than the rudder. My initial efforts at mild Dutch rolls
were sloppy, suggesting handling that takes acclimatization.
Rudder control posed some challenge. It has
some momentum that I suspect may have been
induced by the large cabin, a pusher engine, and
closely coupled tail. You need to use the rudder, but
bumping motions of the pedals seemed best.
To smoothen airflow around the large cabin,
designer Rosario put in a long investigation into the
vortex generator tabs seen in many locations. Such
an advanced investigation into airflows is another
example of the thorough approach by the designer.
Bessa likes to use 4,800 rpm on the 100-hp Rotax
912S for normal cruise and that produces about 100
mph. I noted that at 4,600 rpm we showed slightly less than
100 mph. The SeaMax has a negative or reflex position
on the flaps, which adds a few knots to cruise speed.When
we reflexed the flaps, speed crept up another 3 to 5 mph. At
such a lower power setting fuel burn would be quite reasonable,
in the range of 3.5 gallons per hour.
Stalls were modest and came at surprisingly slow speeds. In
my experience, using installed instruments that sometimes
have lower-speed-range error, stall happened at about 43 mph.
Even with a few miles an hour of error, this qualifies as a very
slow stall. Stall recovery qualities were mild with full control
and fast results.
SeaMax in Your Future?
Fully built seaplanes are not your lowest cost options to fly,
but they offer enviable versatility and the LSA seaplane versions
cost far less than their general aviation counterparts.
The whole amphibian LSA costs less than amphibious floats
alone for a general aviation airplane.
Among LSA boathull amphibians, the SeaMax is comparably
priced to other offerings with a current quote of $137,000
base price for a nicely equipped aircraft. And this amphibian
is available on short notice. Some of the SeaMax price is due
to relatively small production, and complexities like
retractable gear that adds cost no matter how efficient the
Fortunately for the SeaMax, the perceived value may also
be higher due to its versatility, its highly engineered design,
and the deluxe speedboat-like finish. The high quality of
building execution helps justify the asking price, but it’s hard
to put a price on the pleasure a true amphibian like the
SeaMax can provide.
|Empty weight||750 pounds|
|Gross weight||1,320 pounds|
|Wingspan||20 feet 8 inches|
|Wing area||130 square feet|
|Wing loading||10.2 pounds per square foot|
|Useful Load||570 pounds|
|Length||18 feet 6 inches|
|Payload (with full fuel)||420 pounds|
|Cabin Interior||46.9 inches|
|Fuel Capacity||25 gallons/150 pounds|
|Standard engine||Rotax 912S|
|Prop Diameter||3-blade composite|
|Power loading||13.2 pounds per hp|
|Cruise speed||100 kts/115 mph|
|Stall Speed||36 kts/41 mph|
|Never exceed speed||139 kts/160 mph|
|Rate of climb at gross||1,500 fpm|
|Takeoff distance at gross||300 feet (350 feet on water)|
|Landing distance at gross||300 feet (350 feet on water)|
|Range (powered)||500+ miles, 4.5 hrs.|
|Fuel Consumption||about 5.6 gph|
|Standard Features||Boathull amphibian with electromechanical
retractable gear, Rotax 912S in pusher configuration,
3-blade Warp Drive composite prop, brakes, in-flight trim,
25-gallon fuel tank, forward hinged canopy, 4-point belt seat
restraint, overhead switch panel, communications radio and
transponder, all standard engine and flight instruments.
|Options||Additional instruments including digital glass, additional
radio and navigation equipment including GPS, turn
coordinator, artificial horizon, autopilot.
|Construction||Entire airframe made of composite materials
including fiberglass, carbon fiber, and Kevlar; steel or stainless
steel landing gear and other components; made in Brazil with
numerous parts American sourced; distributed in American by
Cosmetic appearance, structural integrity, achievement of design goals, effectiveness of aerodynamics, ergonomics.
Pros – The SeaMax was first LSA amphibian
delivered to a U.S. customer, SeaMax USA believes.
The 22nd design of its developer Miguel Rosario, the
SeaMax is cleverly engineered in numerous ways
(details in article). More useful load/payload than
other boathull amphibians. Solid technical documentation
helped gain SLSA approval.
Cons – Measured against Wet Aero’s Mermaid or
Icon’s A5, the SeaMax has strong competition (though
it compares well and is already on the market). Some
people dismiss the SeaMax because it “looks” too small
(you should try it on before deciding).
Subsystems available to pilot such as: Flaps; Fuel sources; Electric start; In-air restart; Brakes; Engine controls; Navigations; Radio; (items covered may be optional).
Pros – Lots of systems, starting with retractable
landing gear and retractable water rudder, which
hides inside the air rudder, and uncommon things like
a bilge pump. Also electric trim and flaps. Fuel tanks
are easily accessed as wings are about chest-high.
Engine is also easily reached once cowling is removed.
Cons – More systems to manage means more
chance for error. For example, you must be certain you
have the gear in the right position for land vs. water
landings. If a pilot weighs less than 140 pounds, you
must add weight to a designated location.
Instrumentation; Ergonomics of controls; Creature comforts; (items covered may be optional).
Pros – Wide 47-inch cabin surprises those who see
a small airplane from the exterior. You can literally
step into SeaMax and stand on the floor before seating
yourself. Once inside, most occupant sizes will fit well.
Radios and navigation gear are within easy reach of
both occupants. Overhead switch panel also convenient.
Cons – The step in is easy, but getting into or out
of the seat may prove challenging for less flexible
pilots; the seats are low on the airframe. Seat belts
were clumsy to tighten/loosen. (Since my flight evaluation,
the seat belt was changed to one manufactured in
the USA, apparently curing the problem).
Taxi visibility; Steering; Turn radius; Shock absorption; Stance/Stability; Braking.
Pros – Taxiing on land is highly controllable; it
also is in water, thanks to a retractable water rudder
that is located well aft, giving a good lever arm.
Speedy ops on water are fun and easily achieved with
practice. Ground handling is good; canopy hinge is
strong enough to remain open for ventilation during
taxi. Differential hydraulic toe brakes.
Cons – Cockpit side rails are only inches above the
water line at rest; unless you are experienced at flying
in wave conditions, you may be limited to calmer water
like lakes. Gear stance places hull low to ground
(though in an emergency landing on the hull may be a
good idea anyway). Turn radius was fairly wide.
Qualities; Efficiency; Ease; Comparative values.
Pros – Water landings may be the easiest and
work well. Suggested technique is an attitude landing
(hold a speed and wait for contact), a simple way to
handle water landings. Excellent wide and aft visibility
through large canopy. Short water runs in the 300-
to 500-foot range, depending on loading.
Cons – Transition from airplane to boat as the
SeaMax slows demands that you keep the stick full aft
to prevent porpoising and upset. Developing techniques
for good land or water landings will take some
practice, in my experience. Did not attempt a beaching,
however the U.S. rep says, “We park on the beach all
Quality and quantity for: Coordination; Authority; Pressures; Response; and Coupling.
Pros – Light, responsive, predictable controls will
please pilots who take the time to get used to them.
Roll rate was medium to somewhat fast. You rarely
have to land crosswind on the water in a seaplane, but
on land, the SeaMax has all the control authority it
Cons – Handling takes some acclimatization; my
Dutch rolls were rather sloppy at first. Harmony isn’t
perfectly balanced between all controls; a few hours
are needed to optimize (not uncommon on “performance
designs”). Rudder control required attention due
to some momentum in response. (Since my review,
AirMax added a fin on the stabilator to help a pilot to
get used to the controls faster.)
Climb; Glide; Sink; Cruise/stall/max speeds; Endurance; Range; Maneuverability.
Pros – Water runs are relatively short (300 feet
solo), and climb is brisk at 1,000 fpm for a few minutes
after takeoff (later settling at 700 fpm). Landings are
also rather short. Efficient airframe/airfoil, requiring
less than 4,600 rpm to maintain altitude at 50 to 60
pounds under gross. Slow flight went well with flaps
Cons – Even with retracting landing gear, no
amphibian will be as fast as a land speedster; cruise is
about 115 mph (100 kts). Sink rate is slightly on the
high side of average when compared to all LSA.
Stall recovery and characteristics; Dampening; Spiral stability; Adverse yaw qualities.
Pros – Stalls were mild in all my experiences.
Stalls appeared to break benignly in the low 40-mph
range though the factory says 36 mph with optimal
flaps; regardless, stalls come at slow speeds.
Longitudinal stability checks and power changes
showed the SeaMax to be a generally stable aircraft.
Cons – Water ops require attention when slowing
from airplane to boat. The SeaMax is clean and builds
up speed quickly in a dive. High thrust line compared
to most land LSA means powering up will push the
nose downward at first (though the effect was modest
Addresses the questions: “Will a buyer get what he/she expects to buy, and did the designer/builder achieve the chosen goal?”
Pros – With about 90 flying, the SeaMax is the
most successful flying boat in the light-sport sector.
Compared to all other LSA boathull amphibians, the
SeaMax has by far the most units flying worldwide.
U.S. support is good even for a small organization;
base in Florida assures a long demo flying season.
Smooth, pretty airplane built beautifully.
Cons – Smaller service organization that may
cause minor delays in repairs or parts needed. Very
limited number in American customers’ hands.
Brazilian manufacturing may limit resale value
(though SeaMax USA uses U.S. sources for many items
on the SeaMax).
Dimitar STOYANOV says
Dear Mr. Shalom, Wesley, Dan,
Thank you for the quick response, the attention you paid me and the SeaMax brochure you sent me. Thanks for the advice you offered me in answering my questions. If I can be useful as a pilot with aviation experience or other information, you can write to me without hesitation. Can I count on contact with your constructors or plant in my future work on my amphibious hobby project such as sharing ideas and specific activities? .
I wish you health and success in your work
O.r. col D. Stoyanov
PS – Excuse me for sending my letter via this Email, but I have been trying for 2 days to send it to Mr Wesley Queiroz unsuccessfully.