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Selecting the Bell 47 thats right for you By Steve Brousseau • Bell

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Selecting the Bell 47 that’s right for you
By Steve Brousseau
At Rotorfest 2008, I was approached by a number of people interested in purchasing their own Bell 47 helicopter.
The countless number of questions had to do with differences among the D and G models, the various types of
power plants, rotor blades, cost of ownership, training, maintenance, spares, insurance, reliability, and so on.
Those who have extensive involvement with the Bell 47 (especially those who are fortunate to be owners), can be
a wealth of information to anyone wishing to own one of the great helicopters of our time.
So let’s start by reviewing the common Bell 47 by model and major characteristics. The engine, power plant,
rotor blade specifics and other issues are covered with each model. This paper covers the G-model only, since
this is the helicopter of major interest. I have no experience with the “H” and “J” models, or any other variants.
•
Bell 47D-1
This is the original “MASH helicopter” equipped with the Franklin engine, the most common of which is the
210 HP model. The first D-model started with the 178 HP engine, followed by the 200 and 210 HP, ending
with the 235 HP as a power upgrade. It features a 29-gallon cross-saddle gas tank located behind the mast.
The cabin is the narrow version supporting one or two passengers (snugly). Under normal flying conditions,
this version is quite economical to operate at 11 or 12 gallons of 110LL fuel per hour. It uses the “dash-50”
wood blades, which are relative inexpensive to maintain and overhaul compared to Bell 47 models that
require the expensive metal -13, -21, or -23 rotor blades. Wood blades have no time limitation and are
operated “on condition.”
Bell 47D-1 with Franklin 200 HP engine (Rotorfest 2008)
Photo by Steve Brousseau
Most Bell 47-D1 helicopters are equipped with a mechanical starter solenoid using pedals and cables to
engage the engine starter. This system requires the pilot in command to use his left foot to depress a pedal at
the rear of the center beam to start the engine. A pedal is also available on the co-pilot side of the cabin, so
the helicopter can be started by either the pilot or copilot (instructor) in the event of an engine failure. The
major disadvantage of this system is when the pilot is the sole occupant and an engine failure occurs. The
pilot will need to take his right foot off of the right anti-torque pedal in an attempt to restart the helicopter. So
flight control can be compromised under this condition.
The mechanical starting system can be converted to an electric key-start or push-button system (discussed in a
future article), completely eliminating the starting pedals.
Early D1s did not come equipped with a hydraulic system on the cyclic control. Instead, it used “irreversible
disks” to limit the feedback from the rotor system to the cyclic. With the introduction of
a pressurized hydraulic system using a hydraulic fluid reservoir and complex network of pipes and filters,
fore/aft and lateral servos were installed with special components called “irreversible valves.” These
irreversible valves are designed to hold hydraulic pressure in the system should the hydraulic pump fail. This
enables the pilot to maintain most of the cyclic control of the helicopter long enough to ensure a safe landing
Advantages: Lowest initial purchase cost and low cost of ownership per operating hour; configured with
dual controls that can easily removed. This is great personal helicopter and trainer, fun to fly, and generally
reliable. Accepts later G-5-style arched landing gear.
Disadvantages: Can be a tight squeeze (and heavy) with two passengers; low onboard fuel limits flight
range. Engine difficult to start in cold weather; requires preheating.
The Bell 47D-1 and variations were manufactured by Bell Helicopter in 1949, with military orders extending
into 1952. The Bell 47D-1 can be upgraded to the Bell 47G, covered next.
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Bell 47G
This is the upgraded version of the D-1 with increased 42-gallon fuel capacity with its side-saddle peanutshaped gas tanks. It uses the same power plant and wood rotor blades as the D-1, but with several
improvements, including a horizontal stabilizer that operates in conjunction with the fore/aft cyclic, and a
Franklin 6V350-B 235 horsepower engine available as upgrade. When installed in the Bell 47G, the
helicopter was commonly referred to as the ”Super G”. In addition to the increased horsepower, the 6V350-B
offered heavier cylinders and piston rods for increase reliability.
Note: The Franklin 210 HP engine could be readily upgraded to the 6V350-B by competent engine overhaul
shops. The 6V350 could also be installed in the Bell 47D-1.
Bell 47G with Franklin 210 HP engine
Photo by Steve Brousseau
The Bell 47G uses the same cabin as the D-1, limited to the two-passenger-plus-pilot for that cozy fit.
Over the years, many owners of Bell 47D-1 helicopters have converted their helicopters to the Bell 47G. Bell
Helicopter/Textron provides a service instruction (SI) to ensure that all necessary modifications have been
applied.
Advantages: Increased onboard fuel capacity over the D-1, offering longer range. Hydraulic system and
horizontal stabilizer introduced with initial production. Accepts later G5-style arched landing gear or
standard square cross-tubes as found on the D-1. Low cost wood blades.
Disadvantages: Typically more expensive than the D-1 due to upgrades. Slightly higher operating cost than
the D-1. Mechanical pedal start same as D-1; can be upgraded to electric start. Engine difficult to start in
cold weather; requires preheating.
The Bell 47G was manufactured by Bell Helicopter from 1950 to 1956 The Bell 47G can be upgraded to the
Bell 47G-2, covered next.
•
Bell 47G-2
The G2 represents the first major step by Bell Helicopter at delivering the Model 47 with increased power and
lifting capacity. The Bell 47G-2 uses the Lycoming VO-435A engine, operating at 260HP. The major
difference between the Bell 47G and the G2 is the Lycoming engine. The helicopter center frame and engine
basket are newly-designed with the G2, offering a 4-point sprag mounting system. The G2 also went into
production with an electric starting system, first introduced on the center console with a turn-key, and then by
adding a starter box/light switch combination to the collective control, easily accessed by the pilots left hand.
The G2 is perhaps the most admired helicopter in the Bell 47G series, as it was featured in the 1950s
television show, Whirlybirds.
Bell 47G-2 with Lycoming engine
Photo by Steve Brousseau
Initially, the 47G-2 came equipped with wood -50 main rotor blades, but later production introduced the first
metal blades on the 47. These blades are known as “-13s” and had a serviceable life of 3200 hours. These 13 blades are no longer manufactured today. However, the currently-manufactured -21 blades from Bell can
be converted by certified rotor blade shops to the -13 configuration, with the only difference being the shorter
length. Once converted, the -21 blade goes from a 5000-hour service life to 3200 immediately. Performing
this conversion is not recommended due to the high hourly loss after the conversion. The Bell 47G-2
equipped with wood blades is a smarter and more economical option. Today, a G2 with original metal -13
blades with 1000 hours or more remaining is considered a prize.
Many major improvements to helicopter design in the industry were introduced with the G2. Anyone who
reviews the G2 parts manual will find an entire section devoted to accessories, avionics, and other features.
Advantages: Most recognized and cherished among the Model 47 series. Strong and reliable power plant;
can be upgraded to Lycoming VO-435A1F high-compression/high-dome engine at 270HP. Wood or metal 13 rotor blades; large number of accessories available. Intermediate operating cost; fuel consumption at
approx. 15 gallons per hour. Model 47G can be converted to G2 with Lycoming VO-435A engine, center
frame, and engine basket.
Manufactured with improved hydraulic servos over the earlier G-model.
Good flight operating range with 42-gallon tanks.
Accepts later G5-style arched landing gear, pictured above, or standard square cross-tubes as found on the D1 and G, as manufactured.
Disadvantages: More expensive at initial purchase; higher gas consumption with Lycoming engine; higher
engine overhaul cost (double that of the Franklin engine).
The Bell 47G-2 was manufactured by Bell Helicopter Corporation from 1956 to 1962.
•
Bell 47G-2A1
This is the first helicopter in the Model 47 Series designed for extended flight range. It is equipped with 61gallon fuel tanks, extended center frame, relocated oil tank, -21 or -23 metal blades, a wide cabin to better
handle two passengers and pilot, and a longer overall length. It uses the Lycoming 260HP VO-435-A1D
engine. The G-2A1 was originally manufactured with the standard square landing gear configuration.
The standard rotor blades were the -21s, but -23s could be used. Both versions are identical, the exception
being that the -23s are fitted with nine-pound weights in the blade tips for increase inertia. If installed, the
helicopter required an upgrade to add hydraulic boost to the collective. This was needed due to the additional
weight of the blade tips and to ease pilot workload when pulling pitch.
Note that prior to the G-2A1, a G-2A model was introduced for a short time with a unique set of
intermediate/wide fuel tanks, not often seen.
Also, many G-2A1s evolved from the Bell 47G-3B1
helicopters, described next, as an STC allowed the removal of the turbocharger and replacing the engine with
the high-compression Lycoming VO-435-A1F engine rated at 270 HP.
Bell 47G-2A1
Photo by Steve Brousseau
Advantages: 61 gallon fuel capacity and extended range. Strong and reliable power plant; can be upgraded
to Lycoming VO-435A1F high-compression/high-dome engine at 270HP. Intermediate to high operating
cost; fuel consumption at approx. 16 gallons per hour.
Accepts later G5-style arched landing gear or standard square cross-tubes as found on the D-1 and G, as
manufactured.
Disadvantages: Quite expensive at initial purchase; higher gas consumption with Lycoming engine; higher
engine overhaul cost (double that of the Franklin engine). Intermediate to high operating cost; fuel
consumption at approx. 16 to 18 gallons per hour depending on the type of flying.
The Bell 47G-2A1 was manufactured by Bell Helicopter Corporation from 1962 to 1967.
Lycoming VO-435-A1F
Photo by Steve Brousseau
•
Bell 47G-3B1 and G-3B2
These are the high-altitude, turbo-charged versions of the Bell 47. The 47G-3B1 and B2 have the same
characteristics as the G-2A1, but with a low-compression version of the VO-435 to accommodate the added
compression of a turbo-charged power plant. The purpose of the turbocharger is to compress thin air present
at high altitudes (called high density altitudes) so that the aircraft performs as if were flying at a much lower
altitude. This means that the G-3-B1/B2 can safely operate at altitudes over 10,000 feet and up to 20,000
feet. Many of these helicopters are found in high-altitude locations, where “normally aspirated” engines
would not be able to operate.
The one interesting difference between the Bell 47G-3B1 and the B2 is the transmission.
The predominant transmission in the Bell 47 is the “600 series”, as the number “620” is found in its part
numbering scheme for all transmission components. The B2 uses a transmission in the “900 series” part
numbering class following the “620”. The 900-series transmission has a unique fan drive gear set over the
gear set used in the 600-series. Because 900-series transmission is somewhat scarce, parts are difficult to
find and can be extremely expensive.
Bell 47G-3B2 turbocharged (Ryan Rotors, Inc.)
Photo by Steve Brousseau
Bell 47G-3B1 turbocharged (Ryan Rotors, Inc.)
Photo by Steve Brousseau
Advantages: 61 gallon fuel capacity and extended range. High altitude performance; strong and reliable
power plant; used in agricultural and heavy lifting applications when power and performance are required.
Accepts later G5-style arched landing gear or standard square cross-tubes as found on the D-1 and G, as
manufactured.
Disadvantages: Very expensive to own and operate; high gas consumption with Lycoming engine; higher
engine overhaul cost; high cost per operating hour with 1000-HR overhaul vs. 1200-HR on all other models.
Fuel consumption is approximately 18 to 20 gallons per hour depending on the type of flying.
The Bell 47G-3B1 was manufactured by Bell Helicopter Corporation from 1963 to 1967. The Bell 47G-3B2
was manufactured from 1967 to 1974, a version of which was the very last Bell 47 helicopter to come off of
the Bell assembly line, delivered in early 1974.
•
Bell 47G-4 and Bell 47G-4A
The G-4 and G-4A models are perhaps the most expensive versions of the Bell 47. Similar to the Bell 47G2A1, these versions came equipped with the Lycoming VO-540 280 HP power plant. The G-4 featured a
narrow cabin similar to that of the G-2, while G-4 sported the wide cabin found on the
|G-2A1. Interestingly, Bell decided to supply the 600-series transmissions in the G-4, and the 900-series
transmission in the G-4A.
Advantages: 61 gallon fuel capacity and extended range. Strong and reliable power plant; used in
agricultural and heavy lifting applications when power and performance are required. Wide or narrow cabin
depending on model. The G-4/G-4A uses the -23 weighted tip metal main rotor blades with a power-boosted
collective control. Accepts later G5-style arched landing gear or standard square cross-tubes as found on the
D-1 and G, as manufactured.
Bell 47G-4A (Bell Helicopter/Textron)
Photo by Oscar Bernardi
Disadvantages: Very expensive to own and operate; high gas consumption with Lycoming engine; very high
engine overhaul cost ($40K plus). Fuel consumption is approximately 18 to 20 gallons per hour depending on
the type of flying.
The Bell 47G-4 and G-4A were manufactured by Bell Helicopter Corporation from 1965 to 1972.
Bell 47G-4A in Army paint scheme
Photo by Ramon Berk
•
Bell 47G-5 and Bell 47G-5A
The Bell 47G-5 and G-5A models were introduced by Bell to drastically cut the cost of the initial helicopter
purchase. In 1972, a Bell 47G-4 could be purchased for $40,000, or thereabouts. Both models operate on a
12V electrical system, down from 24V on all previous models, a low-profile instrument console, and a fixed
horizontal elevator (on the G-4,), -21 non-weighted metal blades, and no collective boost. However, these
features were introduced (or available as options) with the G-5A and could be retrofitted to the G-4.
The VO-435 engine with the Bell 47G-5/G-5A was a new design that featured a “wet sump” that eliminated
the external oil tank (another cost cutting feature).
The G-5 version (with narrow cabin) and sometimes with only one fuel tank behind the co-pilot seat, as well
as the G-5A (with wide cabin) and dual fuel tanks, introduced the arched landing gear cross tubes, which
could be installed on the earlier D- and G-models.
Most people believe that this is the most-desired Bell 47 model, assuming that the G-5s were the last and
most recent of the Bell 47 series. This is simply not true. The model was originally introduced to replace the
expensive Bell 47G-2A1 in 1967. Production continued through 1973 and concurrently with the 47G-3B2
and the G-4 and G-4A.
I had the opportunity to fly a G-5A a few years ago. I did not like the small instruments (due to my corrected
eyesight), and the non-boosted collective supporting the -21 blades. I found it somewhat difficult to fly
because it lacked some the power features that I was used to. However, it remains a beautiful helicopter. If a
G-5A is equipped with some of the earlier options, it will fly like a 47G-2A1.
Bell 47G-5A with low profile console
Photo by Steven Veigel
Advantages: 61 gallon fuel capacity and extended range on G-5A. Only one tank on the G-5, but a second
tank could be added. Strong and reliable power plant at 260HP. Intermediate to high operating cost; fuel
consumption at approx. 16 gallons per hour.
It was manufactured with the late arched landing gear cross tubes. Standard square cross-tubes as found on
the D-1 and earlier G-models could be installed on the G-5/G-5A. Manufactured with the low-profile
console, offering improved visibility for passengers.
Disadvantages: Hard to find. Expensive at initial purchase due to over-perception about later production;
higher gas consumption with Lycoming engine. Intermediate operating cost; fuel consumption at
approximately 16 gallons per hour depending on the type of flying.
Weaker 12V electrical system. Fixed horizontal stabilizer (upgradeable to standard fore/aft cyclic
operation). Low console with small instruments difficult to see for some pilots.
The Bell 47G-5/G-5A was manufactured by Bell Helicopter Corporation from 1966 to 1973.
New style 206-style tail rotor system
One piece of information that is worth mentioning when selecting a Bell 47 is whether the helicopter has been
upgraded with the late-style tail rotor gear box and 206-style tail rotor blades. These blades are usually painted
white with black high visibility striping and are 2500-hour blades versus the early-style 600-hour blades. The
206-style system can be retrofitted (per Bell Service Instruction) to most Bell 47 models (D-1 though G5A). I run
these blades and I like the long operating life that they offer. I recommend that they be inspected and overhauled
at 1250 hours with new leading edges, bushings, and paint to ensure their maximum service life.
So here are my picks
For the non-business private owner who has the money to spend, I recommend the Bell 47G-2 with the
VO-435-A1F power plant and -50 wood main rotor blades. This version offers 270 HP and is
relatively economical to run with the wood blades.
The Bell 47D-1 is a fine second choice for a personal helicopter.
For a wide-cabin and extended fuel range, then it’s the Bell 47G-2A1 with the Lycoming VO-435-A1F high
compression engine. But keep in mind that the -21 or -23 metal main rotor blades currently have a list price of
$42,600 for each blade. That’s $85,000 per set. Yes, $85K. So make sure that the helicopter has verifiable
adequate times remaining on the installed blades.
Maintenance
This can be a can of worms that only opens from the inside. Business owners who run their Bell 47s every day
complain about some of the staggering costs. But it’s not nearly as bad for private owners. If you fly 50 hours
a year, which is the average for most of us, your recent Bell 47 purchase with 1000 hours remaining on the power
plant will last you 20 years with proper maintenance. But be prepared for the annual inspection costs and
component overhauls and inspections, such as the main rotor grips (300 hours), transmission fan drive gear set
(the major weakness of the 600-series transmission), tail rotor u-joint replacement, miscellaneous bearings, rod
ends, and other components that typically wear during operation.
Purchasing
Before you buy a Bell 47, make sure that you have all of your ducks lined up. A Bell 47 mechanic (A&P who is
trained in Bell 47 maintenance who can perform a pre-buy inspection, a hangar, and an insurance quote are
absolute essentials before writing out that big check.
Joey Rhodes has authored an excellent book on how to properly buy a helicopter, and specifically the Bell 47,
How to Buy and Sell a Bell 47 Helicopter. I won’t get into this subject here, as Joey covers it most thoroughly.
Go to www.joeyrhodes.com for information on purchasing this book.
____________________________________
Disclaimer: The information in this article is the result of years of research, studying Bell 47 parts and
maintenances manuals, service instructions, airworthiness directives, and technical bulletins, as well as what I
have experienced first hand. The dates of manufacture for the Bell 47 variations are a close estimate only, as
special orders to Bell Helicopter sometimes elapsed to the following year. I believe the information to be accurate
to the best of my knowledge and should only be used as a set of evaluation guidelines (things to look for) when
considering the purchase of a Bell 47 helicopter.
This is an information-only copyrighted article and is not to be copied or used without my express written
consent. Photo credits are used.
About Steve Brousseau
Steve owns and operates Bell 47G-2A1 (N1380X), originally a G-3B1, and Bell 47G (N140B), originally a Bell
47D-1, out of Fitchburg Municipal Airport, Fitchburg, Massachusetts and is a member of the Fitchburg Pilots
Association, EAA Chapter 1454, now participating in the EAA Young Eagles program.
For additional questions or comments, contact [email protected]
.
Other articles that I am working on
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Running the Texas No-Bar Kit
Maintenance tips for the Franklin engine
Overcoming that slow-cranking starter in the Franklin engine
Bell 47 wood rotor blade repair and overhaul
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