SECTION 11:
ENGINE AND PROPELLER INSTALLATION
RV AIRCRAFT
11-5
sect 11r8 06/24/11
baffle, or on the firewall with a shroud and a SCAT tube supplying pressurize air from the baffle plenum.
Baffles should be reinforced to withstand the weight of the cooler and lines. Oil lines from the ports on the
rear case, typically 3/8” for the O-320 and ½” for larger engines, should be AEROQUIP 701 or equivalent.
The size of oil cooler necessary for a specific engine is difficult to specify. Engines seem to be quite
individual in their needs, and even engines and airplanes of the exact same type will run “hot” or “cool” with
the same cooler. The only general rule of thumb seems to be the bigger the engine, the bigger the cooler.
IO-360 200 hp engines use oil to cool the piston skirts and are more dependent on oil coolers than their
parallel valve cousins. We have found the Stewart-Warner coolers work better than the Positech coolers on
the 200 hp engine.
ENGINE SELECTION
The RV-4 and RV-6/6A are designed to use Lycoming (I)0-320 (150 & 160 HP) and (I)0-360 (180 HP)
engines. The RV-7/7A and RV-8/8A will accept these engines and and have the added option of the 200 hp
Lycoming angle valve IO-360. The RV-3 and RV-9A are designed for Lycoming O-235, O-290 and O-320
engines rated between 118 hp and 160 hp.
At a glance it would appear that you have four choices of engines: 150, 160, 180, and 200 HP. Actually, it is
a bit more complex than that. The engine list at the end of this section includes approximately 200 individual
model numbers for individual engine variations encompassed within these two general engine types. The
letters and numbers in the engine model number each refer to some feature of that engine. By becoming
familiar with these designators, primarily the prefix and suffix numbers and letters, you can select the engine
best suited to your needs by matching the features on the engine to your needs or preferences.
A guide for to Lycoming designator symbols is presented at the end of this chapter. Below is a sample
engine model number with a point-by-point description of features:
x
I0-320-D1A
x
I: Fuel Injected.
x
O: Designates a Horizontally Opposed cylinder placement.
x
320: Engine displacement in cubic inches.
x
D: High (8.5:1) compression ratio; meaning 160 HP and a 100 Octane fuel required.
x
1: Controllable Propeller. Engine is suitable for constant speed prop.
x
A: Rear Mounted Accessories, Bendix Magnetos.
NOTE:
There are two styles of Dynafocal mounts. Dynafocal I and Dynafocal II. Dynafocal II engines are
scarce in the used engine market and not available as “new” through our OEM agreement with Textron-
Lycoming. Van’s Aircraft will not supply mounts for this type of engine.
A list of engine identifiers to avoid follows: (the letters listed below are the “first” letter after the cubic inch
number: example, IO-320B2A is Dynafocal II and is to be avoided.
IO-320A,B or C, IO-360E (180HP), IO-360D (200HP)
There is a wealth of information in these lists, (which may not be complete down to the most recent engines)
but they often seem like a treasure hunt when you are trying to find specific information.
How much horsepower?
The RV series was designed around the most plentiful and reliable of aircraft
engines, the Lycoming 0-320. In production since the early 1950s, this engine has proven to be one of the
most reliable internal combustion devices ever built. There are two basic versions, and a vast array of
different models and sub-models.
The low compression (approx. 7:1) version is rated at 150 hp and designed for 80 octane fuel. The high
compression (approx. 8.5:1) develops 160 hp and is designed for 100LL. Low compression engines are
often modified to produce 160 hp, but this is NOT sanctioned or approved by Lycoming.
The O-360 (or its cousin, the parallel valve IO-360) develop 180 hp on 100LL.
An RV with 150 hp is
not
an underpowered airplane. Remember, this is the same engine that drags four
place production airplanes around. Installed in the light, clean RV, it provides excellent performance.
Installing higher powered engines usually increases the climb rate, shortens the take off and increases the
cruise and top speeds slightly. There is a price, of course; power comes from gasoline, not the engine. If
you use the extra power needed for better performance, you will burn more fuel.
Although the temptation to install the biggest engine and get the most performance is great, remember, even
with the lowest horsepower, a clean RV is capable of speeds very close to the published VNE. Engines with
more horsepower can easily drive the airplane past redline in level flight. Just because you
can
install a big
engine doesn’t mean it is a smart thing to do.
RV
AIRCRAFT
SECTION 11:
ENGINE AND PROPELLER INSTALLATION
11-6
sect 11r8 06/24/11
What model?
The rumor that Lycoming once built two identical engines has never been proven. The variety
is so large that Van’s often (very often) cannot offer advice on whether a specific model will work in an RV.
Remember, you, the builder, are ultimately responsible for making sure the engine you acquire will fit your
airplane. Here are a few tips to help with engine shopping:
x
Mounting Style: Lycoming engines have been built in three basic mounting styles, conical, Dynafocal 1
and Dynafocal 2. The difference is in the angle that the engine mount bolts form with the crankshaft.
An engine mount to fit any of these is available from Van’s, although the Conical and Dynafocal 2 mount
are a special order item, requiring extra time to supply.
x
Induction: One of the critical items in determining whether an engine will fit in an RV is the placement of
the “induction device”, the carburetor or fuel injection servo. In an effort to accommodate airframe
manufacturers, engines have been developed with several different carb locations.
x
Aft mounted carbs, feeding through the side of the oil sump, will not fit an RV. However, often a change
of sump to an updraft version is all that is required to make the engine fit.
x
Most engines with updraft carbs will fit an RV, but some engines have the carb mounted at the very rear
of the sump, which interferes with the RV-6A nose gear mount.
x
In general, any engine with a forward facing or vertical induction device on the middle or front of the
sump will work.
x
Fuel pumps:
The low wing design of the RVs requires an engine driven fuel pump. Since many engines
on the used market originally powered high wing airplanes with gravity feed systems, they do not have
fuel pumps. Usually it is relatively simple to convert an engine without a fuel pump, but this matter should
be checked. Carbureted and injected engines require different pumps, so check carefully.
x
“Different” engines:
The O-320-H2AD engine, used for several years in the C-172, is a special case. It
is unrelated to the rest of the O-320 family, and requires a special mount, which Van’s can supply upon
request. It also has a pad for a forward mounted fuel pump, but, since the C-172 does not require a
pump, none was ever installed. The case must be opened and modified to operate an engine driven
mechanical pump.
x
Some engine models we have encountered that will NOT fit in an RV, at least without modification,
include the I0-320-B1A and the O-360-A4K. This is by no means a complete list.
x
Note that the 200 hp IO-360 angle valve engine is not recommended for the RV-4 or RV-6/6A. It is
physically larger than the parallel valve 180 hp IO and O-360s and will not fit without major modifications
to the cowl. It may, however, be used in the RV-7/7A or RV-8/8A.
PROPELLER SELECTION
The RV builder has four propeller options to consider: fixed pitch wood, fixed pitch metal, and constant speed
metal or constant-speed wood/composite. Just to make it more complicated, the wood/composite props
feature either hydraulic or electric actuation. The metal constant speed props are hydraulically actuated.
Traditionally, metal props have been used on production light aircraft because they offered the best
compromise of performance and serviceability. A fixed pitch metal prop will usually weigh about two or three
times more than a wood prop. For a 150-180 HP engine, this represents a difference of about 17-22 lbs.
The metal prop, because of the greater strength of the material, can be made with a thinner airfoil section
and is generally considered more efficient than a wood prop. This means more overall performance. Not
necessarily significantly more performance, but more than enough to justify the added weight.
All of the fixed pitch metal props manufactured to fit factory designs powered by O-320 and O-360 engines
were designed for much slower airplanes so their pitch angles are much too low to be effective at RV cruise
speed. While it is true that metal props can be re-pitched for more or less speed, they
cannot
be re-pitched
to the extent needed for an RV. In addition to a loss of efficiency incurred through excessive re-pitching, the
stress on the metal renders them
unsafe
. The stresses on metal props are very involved, and are caused by
harmonic vibrations which cannot be felt by the pilot. Extensively reworked metal props have a history of
losing sections of their blades without warning. The result is a catastrophic imbalance, capable of tearing the
engine completely free of the mount and airframe before the pilot can react. People have died.
The
only
fixed pitch metal props suitable for RVs are the Sensenich 70CM for the O-320, and the Sensenich
72FM for the O-360.
Because metal props have not been available, wood props have been, and still are, widely used. These
have both advantages and disadvantages compared to the metal prop.
DISADVANTAGES:
x
The finish of wood props will deteriorate and weather-check over a period of time and require refinishing
every 2-5 years depending on operating conditions.
x
Wood props suffer when flown in rain. While most wood props now offer some form of leading edge
