73 Model Aviation AUGUS T 2012 www.ModelAviation.com
THE ENGINE SHOP
Testing your engine’s performance
What really goes on with engines when they are tearing around the skies? I have always wondered. Have you? For more years than I want to reveal, I have read
the various “engine columns” of my heroes, many of whom I
consider to be legends in their own time. When I was asked
to do “The Engine Shop,” I was uncertain whether I could
meet their levels of excellence and technical knowledge about
things such as metallurgy. I was sure I couldn’t replicate their
I started thinking about what the new generation of RC
pilots wants or needs to know and maybe things they might
not yet know. When it comes to engines, there is much
misunderstanding about propellers, airspeed, climb rates, etc.
I see it regularly. I visit a large number of flying sites in my
travels and see engine/fuel/propeller “folklore” in action.
This gave me the idea of testing engines in a slightly
different manner than the customary bench-running method.
There is no doubt that running engines on test stands with
different propellers satisfies a certain appetite for information,
but does it really tell you what will happen in the air?
Airborne performance has been difficult to measure
and the data equally hard to collect. There are some good
systems available, but none are as easy to use as the Spektrum
telemetry system. This new technology became a game
changer when it came with the DX8.
Spektrum and its telemetry have now made it easy to set
up and capture data while you fly. Throw in an iPhone with a
plug-in Spektrum receiver module, and the Spektrum STi app,
and it becomes cool indeed. Not only cool, but you can use
any JR or Spektrum transmitter and receiver with a data-port
Some of you may have read about the engine test that I did
on the O.S. FS-95V. It was cold at that time of the year, so I
rigged the engine test stand with a DX8, a throttle servo, a
receiver, and a telemetry module. This allowed me to monitor
all of the necessary bench-run data from the warmth of my van!
The free Spektrum STi iPhone app is easy to read and records
data that you can review later. For what I had in mind, I snagged
a volunteer to write down all of the data as it happened on the
ground, and as I flew certain speed and climb tests.
The basic plan was to read engine-performance data on the
ground and in the air. This was later expanded to include flight
performance such as airspeed and altitude change.
The main idea was to see the difference in engine
behavior between running on the ground and
running in the air.
I am inviting RC pilots to try this at home by
explaining how easy it is! The equipment is readily
available and easy to set up.
The Mintor 33-powered Redwing MXSR is loaded with telemetry
instruments for ground performance and air performance
The package comes with a computerized ignition system with auto-advance stando;s
to mount the engine, a four-bolt propeller washer, and spark plug.
The Mintor 33 gas
machined from high-grade aluminum bar
stock, is lightweight
and pleasing to the