What are the advantages
and disadvantages of a triplane?
High drag from wing interference and lift loss from six wing tips.
The extra work required to build six wings.
Loss of visibility due to the location of the centre and lower wings
blocking the line of sight to the front and down.
The high aspect ratio of the wings allows an excellent rate of climb
and a good glide ratio if the wing interference drag can be reduced.
High roll rate from the short span wings.
Good longitudinal stability due to the extra lift centres.
Unusual and eye catching aircraft that will attract attention no
matter where it is flown.
How do we maximize the advantages and minimize the disadvantages?
By utilizing a modern airfoil, narrow wing chord, lots of wing
stagger and properly shaped wingtips we can reduce the interference
drag and the tip loss.
Create "quick build" wings using common wood working tools that most
builders have on hand. The wings would be built much the same way as
a model airplane.
By using a light 2 stroke engine the wings can be mounted further
back than they would have to be for a conventional aircraft engine
thereby keeping them out of the field of view, also the narrow chord
wings do not block the vision the way the wide chord wings do in a
Supply full size patterns for all the fittings, controls, ribs,
panels and bulkheads to make layout work faster and easier for the
While it is always a good idea to minimize drag and maximize
efficiency these factors are not as critical to an airplane that has
a cruise and top speed of less than 100 mph. Maximum efficiency is
not all that important to the recreational flyer that just fly's on
a weekend for enjoyment and relaxation. The 2 stroke engine that is
typically used in this type of aircraft is not known for its fuel
efficiency, which is the primary reason for having low drag in an
The Triplane construction is identical to the 1B biplane except that
on the prototype we used a fibreglass skin for the wings instead of
plywood. This gave a much smoother surface to the wing than the
plywood. The wings for the triplane are made with a wooden frame and
covered with fibreglass or plywood. The remainder of the
construction methods are the same as the biplanes.
Flying the Acrolite 1T Aircraft
The aircraft accelerates and lifts off the ground very quickly and
climbout is exceptional. We were concerned that with the ailerons on
only the centre wing that the roll rate would not be adequate but
this was not the case. Aileron response is just a bit sluggish
initially but once it starts moving it is quite good. It does not
roll as fast as the biplanes but the turning radius is a lot smaller
so I think it may just out turn the biplanes. The stall is more
pronounced in the triplane and unlike the biplane that will fly
itself out of a stall even with full back stick. the triplane
requires proper stall recovery technique. In a 1000 ft climb out
contest with the 80 hp biplane the triplane lagged only slightly
behind. A full throttle, level flight, speed run showed 115 mph
indicated at 6800 rpm. The triplane flew hands off on the first
flight with no changes required in trim and it is very stable in
pitch. Visibility is very good, especially on approach and it feels
easier to land than the biplanes because it does not seem to float
as much at touchdown. Rudder authority is very good and it will make
a really neat flat turn, just cut the throttle back to half, give it
about ¾ rudder and it will do a 120 degree flat turn in the blink of
The Triplane presently has just over 50 hours on it, flight testing
has been completed and the aircraft sports a new shiny polyurethane
finish. We are very pleased with its flight characteristics and its
performance and reliability. This aircraft required no changes and
had no problems at all during its flight testing. Other than trying
a couple of different props (we finally ended up with a two blade
GCS ground adjustable so the blades from the Warp Drive prop will go
into a new 3 blade hub for the Acrolite 1C.) we made no changes to
the airplane at all. The construction drawings and builders manual
are completed and are now available. Please see the ordering page
for more information.
50 bhp Rotax 503
Top wing span 18.5 ft - Bottom wing span 18.5 ft
111 sq. ft
rate of climb
landing distance, ground roll
limiting and recommended speeds
design manoeuvring speed (Va)
never exceed speed (Vne)
stall, power off (Vsl)
landing approach speed
All specifications are based on manufacturer's