Sauer flight test - sprite aviation services ltd

Variety is the spice of life according to
William Cowper but you might wonder where
modern day pilots get their ration of variety .
Of course we have any number of different
aircraft but just look under the bonnet and
you will find one powerplant dominates. Not
only is the Rotax 912 series the most
successful aircraft engine ever, it has
reached monopoly status and as we all know
that can be bad for the consumer. A good
healthy market with competition keeps
everybody on their toes and a bit of choice
for the consumer means that customer
service and support might influence the final
decision on engine selection rather than
effectively having no choice and no where
else to go. Enter “The People’s Engine”. Ok
so we’re pushing it a bit . The Sauer is not a
VW (Well not 100%) but there are some
similarities with the Trail/ Sauer philosophy.
Volkswagen was originally founded in 1937.
In the early 1930s German auto industry was
still largely composed of luxury models, and
the average German rarely could afford
anything more than a motorcycle. As a result
only one German out of 50 owned a car.
Can you see where I am going with this?
Nando Groppo conceived the Trail out of a
desire to produce something good but
affordable and so we have a dilemma. A
radically different aircraft with the focus on
flying qualities and economy but with only the
option of the technically brilliant but
massively overpriced standard fit motors.
Surely an imbalance and one that needed
sorting out if Mr Groppo’s masterpiece was
to make it out of prototype numbers and into
serious production. The AeroVee was
considered but quickly discarded. A customer
survey showed that the thought of self
assembly engines was scaring them stupid.
The message came over loud and clear. The
customer wants a factory assembled engine
which has been professionally built and
tested at a reasonable cost.
Sauer to
the People
By Graham Smith
Francis Donaldson was the first person to
see the imbalance needed sorting and
suggested having a look at Sauer. The
S2200UL and S2400UL seemed ideally
suited but the cost was still too high. After a
good deal of negotiating Sauer agreed to
supply the engines at a price which gives us
a chance of achieving our goal. The first
motor was ordered (S2200UL 85 bhp) and
Nando agreed to design the mount and
cowls.
Step forward one year. Nando emails to
advise the Sauer Trail is ready for testing. He
has completed 4 hours flying and has made
some modifications to the cooling baffles and
added an oil cooler- an option we will not
need in the UK. Sue and I travel to Mezanna
and arrive 9.30 in the morning, its already 30
degrees and not a cloud in the sky or a hint
of wind. We start with a detailed look at the
aircraft. It’s new but not the first time I have
seen it. Nando took it to Aero
Friedrichschafen and although the public
were buzzing around it in numbers for the
whole period of the show, it was almost
ignored by the press who like fast, shiny and
expensive. The Trail is none of these things.
The people’s plane will have to fight for every
scrap of publicity.
Cowls removed the innards are exposed.
The installation is neat but minimal. The first
ignition system is driven by a slick magneto
mounted on the rear of the crankshaft. The
second is electronic with coils fixed to the
firewall. A Facet back up fuel pump is in
series with the engine driven unit. All the
hoses are fireproofed. The inlet manifold is
heated by oil to prevent carburettor icing.
Nando has custom built the exhaust to
Sauer’s spec. It all looks tidy- Not a drop of
oil in sight. The wire locking is immaculate.
The propeller of choice in Italy is a GT
Diameter 166 cm. Pitch 145 cm. Nando tells
me it is a cruise prop. I don’t know what right
I have to disagree with a 20000 hour pilot but
he is wrong. More on that later. No ballistic
chute on this one. It looks like it was fitted
and then removed. The weight certificate
says 318 kg empty but we argue about this
as the bush wheels had been removed and
replaced with the standard 8 inch wheels.
There is a 19 kg penalty for the giant
wheels so possibly this plane is around 300
kg. Thats lighter than our demo plane but we
have all the LAA mods installed which could
account for 5 or 6 kg Nando advises me that
the Sauer is similar in weight to the Rotax
although Sauer say it is about 4.5 kg lighter..
Confused? A kilo here or there is academic
until you get to the microlight version. In my
opinion this is a fairly standard weight
aircraft.
Moving to the inside of the aircraft it feels
familiar. The seats are a bit harder than mine
without the luxury covers and the floor minus
carpets gives the plane a spartan feel. Once
I am seated and belted in it could be the
same plane. A quick look around the panel
and I notice the magneto switches are wired
upside down. (Must be a continental thing)
Quite bizzarre as all the other switches are
correct. The ASI is in kph so I make a mental
note. Climb at 90 kph (normally 50 kts for
me) and approach just below 90 (Normally
40 kts for me solo or 45 dual). Fuel is 20
litres per side and switched on. Mags both on
with a small amount of choke. Fuel pump on
and I hit the starter, the engine instantly
bursts into life. First thing I notice is the lack
of Rotax shudder . The Trail being
constructed of thin skins and large thin
sheets of perspex tends to shake on startup
due to the gearbox effect. I spent a lot of time
reducing the panel vibration on my Rotax
demo plane. Totally not necessary with the
Sauer. Tickover initially is 1200 rpm and a
very different feel to the Rotax. The oil
pressure is rising so I sit there and listen to
the sound of the engine. Its a beautiful even
beat. Sounds a bit lazy - almost relaxing. A
complete culture shock. I realise that if there
was something wrong with the engine I
would have no idea. It’s that different from
the high revving motor that has faithfully
served me for the last 500 hours of flying.
The cylinder temps are moving off the stops
so its time to taxi. I am still struck by the
different feel of the motor. It responds crisply
but not frantically. It is very deliberate and
purposeful. The tailwheel steering is geared
lower than on my plane. I seem to remember
that mine is on the middle setting (out of 3) I
forget to check to see what setting this has
but it makes no difference. The ground
handling is as easy as it gets with a
tailwheel. Time for power checks and again I
am struggling to remember the rpm to carry
out the mag checks. I guess at 2000 rpm and
switch the mags off one at a time. There is a
slight falter in the engine but not enough to
measure the mag drop. The oil temp is now
above 50 degrees so its time to go. A quick
check of the cylinder head temps which have
reached 180 degrees. The red line is 200 but
they never went above 180 during the whole
flight. Flaps to 20 and full power. The engine
goes straight to 2800 rpm and I can feel the
acceleration. My foot is instinctively twitching
over the right rudder pedal waiting for the
time to feed in the control but of course this
engine turns the other way. I feed in a little
left rudder and I hold the centerline. The
OAT is 30 degrees and there is no breeze to
help but in no time I am climbing at 90 kph.
A test at maximum weight showed that
0-500ft the climb rate was 800fpm dropping
to 700fpm between 500-1000ft. My eyes are
glued to the cylinder temps but they never
move away from 180 until the power came
off for the descent back to the circuit. I am
guessing that in the UK the temps could well
be around 160 which would be ideal. The oil
temps never went above 80 which is a bit
short of the ideal but I am sure without the oil
cooler and our post climate change summers
it will all work out. First test was to try wide
open throttle straight and level. The rpm’s go
to 3200 which is the red line. I would prefer
(and I guess the LAA would also insist) that
is was not possible to overspeed the motor in
level flight. It is a slightly debatable point
because the rev counter was jumping around
a bit so maybe a better more accurate check
is needed. I was so tied up with checking the
rpm’s that I forgot to record the maximum
speed but I expect it was around 160 kph.
Bearing in mind this is the smaller motor
and a touch under pitched a good
result. I expect cooler temps and
an S2400 combined with a
slightly bigger prop will give
the 80 kts cruise
everyone wants.
Throttling back to 2800 rpm I saw 140 kph
and 2600 rpm gave 120 kph. All the time the
airframe resonance and noise levels were
low. Fuel consumption overall is around 12
lit/hr according to Nando.
Dropping back into the circuit the engine
was eased back to 1800 rpm with full flap at
90 kph on short final. This proved to be
slightly too fast with an extended flair but
even so it was down and stopped in around
100 meters.
Something I was really keen on trying was
hand swinging the motor. Just by chance the
prop had been fitted in the right place with
the compression falling exactly where I like it.
I thought it would be best to let the motor
cool for an hour so later I went back to see
how the Sauer responds to hand starting. It
was too easy. It started 2nd pull every time.
What a joy and a really useful feature, not
possible with the Rotax or Jabiru. Another
victory for utility over complication - Just like
the original people’s car.