Acrolite 1T Triplane

What are the advantages and disadvantages of a triplane?

Disadvantages;


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.

Advantages;


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 biplane

Supply full size patterns for all the fittings, controls, ribs, panels and bulkheads to make layout work faster and easier for the builder.

Comments:


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 aircraft.

General:


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 rudder and it will do a 120 degree flat turn in the blink of an eye.

Present Status

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.
 

specifications
 
powerplant
propeller
length
height
wing span
wing area
seats
empty weight
useful load
gross weight
fuel capacity
range
50 bhp Rotax 503
x
15.5 ft
x
Top wing span 18.5 ft -  Bottom wing span 18.5 ft
111 sq. ft
1
450 lbs
x

700 lbs
x
x

performance

takeoff distance, ground roll
rate of climb
max speed
cruise speed
landing distance, ground roll
service ceiling
x
805 fpm
93 mph.
80 mph
x
x

limiting and recommended speeds

design manoeuvring speed (Va)
never exceed speed (Vne)
stall, power off (Vsl)
landing approach speed
75 mph
120 mph
44 mph

x

All specifications are based on manufacturer's calculations