I think it's appropriate to establish our position in this venture of alternate power.
We picked the Van's RV6A as our test bed. It is a straight forward no frills aircraft.
It does everything very well without being the fastest or best acrobatic, etc. But it's
an honest airplane that does it all well and some of it better than others. The price
is right; probably the most bang for the buck for all the good merits that it possesses.
Keeping with the Van' s philosophy, we have created a power plant package of ample
power that is simple, inexpensive to buy and maintain with good reliability. It' s not an
expensive hot rod nor is it a cheap marginally powered replacement. We like to equate
it to a Chevy - - you just get in it, turn the key and go.
The engine is modified only to the extent necessary to achieve our goals as stated above.
It is a Chevrolet 4.3L V-6 with cast iron block and heads as used in the S-10 truck and vans.
This particular cast iron engine lends itself to ease of rebuild, by virtue of readily available
inexpensive parts, ease of machine work, and familiarity with the engine by most engine
rebuilders. This Chevy V6 is very similar to the 350 only with two cylinders removed.
When possible, we run the stock Chevy cam and followers. These engines when purchased
from Chevrolet may have any of six different cams and we do not always have a choice of
which cam will be in the engine. If the engine happens to have one of the cams not suitable
for our use, we replace it with a very mild aftermarket cam, matching followers and springs.
The aftermarket cam we use is designed to produce its highest horsepower between 2000
and 4000 rpm, just as the tuned headers are.
The heads are modified to protect them when aviation fuel is used. Hard seats, stainless
valves with chrome plated stems and hard tips, and bronze guides are installed. This is a
normal job performed by any competent automotive machine shop and is not considered
a high performance or racing modification. In the event of taking on a bad load of fuel, such
as jet fuel, the survivability of the engine is greatly enhanced. The valves and seats are better
able to resist the extreme temperatures and the bronze valve guides will stand a better chance
of remaining free.
The electronic fuel injected engine is converted to standard carburetion with a manual fuel
mixture control. The stock Chevrolet intake manifold is modified to accept the Holley carburetor.
However we now have under development a manifold expressly for use with the carbureted system.
This will be installed on all future engines. Why replace a good proven reliable electronic fuel
injection (EFI) system with a carburetor? Technologically this would seem like a step backwards
and in a sense it is. However there are several reasons for this decision not to use an EFI system.
Cost.... an EFI system adds over $2000.00 more to the engine cost. How can this be when all you
have to do is remove the current system from the vehicle intact with the engine? True this will work,
until it fails, and as good as these systems are, they do fail. Over the years we have had five different
vehicles that have failed with total engine stoppage. To ensure this does not happen on the aircraft
requires a redesign on the system itself. To simply add a second system would not only double the
cost and complexity but does not necessarily ensure that the second system will not fail the same
way. Also, the second system would require a second alternator as the EFI system draws a
considerable electrical load in injector and pump operation. Why the second alternator? The
damage to the first system could well be from the alternator itself and if the backup system is
switched to the first alternator it could be failed just as the original EFI system was. A backup would
require a mechanical or electrical, not electronic, system. All of this will require considerable R & D
costs and the cost of the fail-safe system itself.
Safety.....Under-the-cowl fuel pressures for an EFI system can run as much as ten times higher than
a carbureted system. Carbureted systems typically run 3 to 5 psi, EFI systems run 30 to 45 psi with
the ability to produce up to 90 psi in the event of a regulator failure. Not only are the pressures higher,
but the fuel feeds are much more complex and subject to leakage. We have experienced injector
system failures on a stock system that actually created a fog under the hood of a car. An EFI system
regulates the fuel pressure by routing excess fuel back to the tank. The pilot must manage this constant
flow of fuel. It involves more complex valves, and extra return fuel lines. With the complexities of an EFI
system involving bypass fuel management by the pilot, extra pumps, additional fuel selection valves and
attendant plumbing certainly detracts from the overall safety.
Reliability.....although the EFI systems have a great reliability record they need backup. Power loss
due to fuel system failure is very common among aircraft. The EFI system depends on an electrical
system for a least 3 items: to fire the injectors, run the fuel pump, and operate the computer for the
correct timing/mixture. If the charging system is lost it places a heavy load on the battery and
dramatically decreases the flying time. With a carburetor only one fuel system item may be
dependent upon the electrical system, that is the pump and even it can be mechanical. With all of
this in mind we feel it would be most prudent not to use the EFI system until such time as we are able
to resolve some of these problems. Yes, the EFI system may in some respects be better, but we feel
we could be sacrificing safety and reliability if we don't do our homework first. At this juncture the EFI
system does not meet our goals of safety, low cost, and reliability. But we are working on it and it may
well be a future option.
The ignition is a straightforward dual point electrical distributor with two batteries, two coils, two
condensers, and single plugs. However it is possible to run an electronic system with a backup
electrical point system. The electronic system is superior in some ways, but can be failed more
easily than the electrical system. Why not run two electronic systems? Alternators are a common
cause of electronics failure as they can spike a system with high voltage (150V+). If you were to
experience a high voltage surge, which took out one electronic system, you would immediately
switch to the backup electronic system and it would be taken out too! That is one reason we run
at least one set of plain old electrical points, they are more tolerant of spurious voltages.
The cooling system is professionally designed and engineered by one of the best engineers available,
as evident by the outstanding cooling obtained. We typically run 190 degrees in the engine and 150
to 160 on the radiator outlet. The engine is designed to run 210 degrees in the trucks. This very
effective cooling system is all done with a very compact lightweight radiator and minimal aerodynamic
drag under a basically stock cowling. Typically a new engine does not come with the water pump.
We install an aluminum aftermarket pump; it is not a racing pump. In every sense of the word the
cooling system is stock except it has a very good quality pump and radiator. A stock 180 or 192
degree thermostat is retained to ensure stable engine temperatures. An optional combination
alternator/water pump is available. This adds to the simplicity as it eliminates belt adjustments,
alternator brushes, and brackets while providing a sturdier water pump and alternator than stock.
Again for simplicity, elimination of costs, and reliability no oil cooler is used or needed.
Now as for putting lots of flying hours on the installed system - - we couldn't agree more! The only
limitations have been costs; we're not GM or Ford. We do try to put as much airtime on as possible,
but we are limited on time and money. This has always been a point of contention with us as we see
so many units that simply do not have the necessary flight time to proof them and they are making
claims which we know not to be true, whether it be through ignorance or intentional. One factor which
has helped us mitigate some of the flight time is good professional engineering . By having the correct
engineering we are better able to predict the outcome of empirical testing. But again, we strongly
support flight time. An example of using sound engineering is the fact that the stock nodular cast iron
crankshaft in the 4.3L V6 Chevrolet engine is capable of running in excess of 2000 hours at 4000 RPM
under full load manifold pressure, 225 to 250 hp before it will start to fatigue.
Our engine never reaches these load parameters and therefore would experience only normal bearing
wear, not fatigue. Without knowledge of proper engineering it might seem reasonable to install a forged
steel crankshaft with its attendant additional costs, and possibly less desirable bearing performance.
This also is a good illustration to keep it stock.
As for the speed reduction unit, it does have an effect on the engine. From the tip of the crankshaft
farthest from the propeller to the propeller itself, everything has to be in agreement. Bearing loads,
structural loads, torsional reversals, harmonics, and use of correct materials all play a big roll in the
success of the overall power plant unit. Every bit of this must be professionally engineered to ensure
a cost effective reliable power package. Without the proper engineering you could be misled into
thinking the reduction unit is performing OK when in fact it could be detrimental to the engine itself.
We hope this explains the WHY of Belted Air Power's alternate power project. We have a real interest
in the everyday flyer and have set our sights on fulfilling your needs with an economical and reliable
total package. Through our professional engineering and conservative approach we are able to offer
a product by a company that will be there to stand behind it in years to come.
If you're in the area please stop by and fly with us. We believe that many of your questions will be
answered when you see for yourself just how a basically stock engine in concert with a professionally
engineered package really performs.
Jess Meyers, pres.
Belted Air Power - Hanger C6 - North Las Vegas Airport NV - Ph 702.384.8006 - © Copyright 2004