There is plenty of room in the
fuselage for the electronics
and the fuel tank.
The PTE 72 engine is installed
on the firewall. The spark plug
caps and mufflers easily fit
inside the large cowling.
The PTE 72 engine comes in a heavy-duty cardboard box that is encased in
soft foam rubber. Included with the
engine is a template for drilling the
mounting holes in the aircraft’s firewall.
The engine uses the same four-bolt
propeller spacing as the DA-50R, DA-
60, and DLE-55/61 engines. Propeller
drilling jigs designed for those engines
will also work for the PTE 72.
The ignition unit is designed to
function with a 4.8- to 7.2-volt battery,
and no regulator is needed if using
A123 or two-cell LiPo ignition batteries.
The choke and throttle arms come
preinstalled on the carburetor.
I used the supplied standoffs and
hardware to mount the engine on
the Redwing RC 50cc Extra 330SC.
Make sure to apply some medium
threadlocker to the mounting bolts. A
Redwing RC adjustable pushrod and
two ball links were used to connect the
throttle arm to the throttle servo. The
ignition unit was mounted inside the
airplane’s motor box. Attaching the fuel
line to the engine completed the engine
The airplane was fueled and secured
with a restraining device before its first
run. As an additional safely measure, I
had a helper hold the aircraft. With the
ignition turned off and the choke on, I
flipped the engine 10 or 12 times to get
fuel to the carburetor. I then turned the
ignition on and flipped the propeller
a handful of times until the engine
The choke was opened, and a few
flips later the engine was running. The
engine idled smoothly and quietly. After
letting the engine warm up, I advanced
the throttle to half and kept it there
for a couple of minutes. I repeated this
process a few times before advancing
the throttle to full power. The engine’s
throttle response was excellent. I found
no need to adjust the needle valves.
I shut off the engine and inspected
the airplane for fuel leaks and to make
sure that all of the mounting hardware
was secure. Everything looked great so I
refueled the airplane for its first flight.
After taxiing the airplane into place
on the runway, I advanced the throttle
and the Extra was airborne in a short
distance. It had more than enough
power for every aerobatic maneuver
that was flown.
The owner’s manual recommends
either a 23 x 8 or a 24 x 10 propeller.
Both propeller sizes were tested on
the engine. The engine turned each
propeller at more than 6,000 rpm, and
both performed well in the air. For a
mix of 3-D and precision flying, I prefer
the 24 x 10 propeller.
The PTE 72 engine flew the 17-plus-
pound Extra easily and had more power
than necessary. The included mufflers do
a good job of keeping the engine noise
down and they sound great.
I am happy with the PTE 72. It is
the smoothest-running gas engine that
I have owned—it’s very powerful and
to realize that the PTE 72 provided
more than enough power. All that was
required to get the Extra trimmed was
one click of right aileron and a couple of
clicks of up-elevator trim.
With the CG at the recommended
setting, a slight amount of forward
stick was required for inverted flight.
I found no need to do any mixing in
the transmitter. Knife-edge in both
directions was straight and aileron rolls
were axial with no aileron differential
The rudder is large and powerful so
merely a slight amount of rudder input
is needed to maintain altitude while in
75 Model Aviation SEP TEMBER 2015 www.ModelAviation.com