A
tour of the Rolls Royce Gnome Gas Turbine Engine
The
Gnome (series) turbines are manufactured by Rolls Royce under
license from General Electric, targeting the 'overseas' market.
A cousin to the General Electric T58, the Gnome turbines are
designed with output ratings from 1,000 HP to 1,660 HP.
Several models were produced for powering helicopters including
the H1000 Mk 501, the H1200 Mk 660, and the H1400 gas turbines.
Several other models were designed to power Hovercraft
and aircraft GenSets.
Here
we take a tour of the Rolls
Royce H1200 Mk 660 which is a 10 stage axial flow turbo-shaft
engine weighing 314 lbs, with an output of 19,500 rpm producing
1350 HP.
Here's what the several thousand parts look like when a Rolls
Royce Gnome is completely
disassembled.
These
particular twin Gnome H1200 Mark 660 turbines flew for many
years in a Nigerian registered Wessex
60 helicopter. They came certified air-worthy, with logbooks,
lube oil system, and single (common) gearbox. With just over
1,000 hours since overhaul, these fine examples will provide
many more years of dependable service.
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Here's
some photos 'as received'. There were several minor
parts missing, so (after some research) I was able to
locate a Rolls Royce Gnome aircraft parts supplier and
get them ordered. After a detailed inspection, I realized
both turbines had been properly preserved and are in
outstanding condition overall.
Since
I no longer have my turbine engine test stand, I'll
modify the factory turbine support fixture so it will
also hold my batteries and fuel supply. I'll be able
to roll it outside for ground running.
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The
aircraft logbooks document all maintenance on these
engines since the aircraft first rolled off the assembly
line. Every component change, all adjustments, and every
test result- it's all documented here. Lots and lots
of power checks. Each and every maintenance action was
performed by factory certified technicians.
I
found entries for factory servicing performed in the
field by maintenance teams out of Djambi Sumatra and
Great Yarmouth England. Since my background is in Aviation
Maintenance, I find it very interesting to see where
the aircraft
has been and what work was performed. It's like looking
back in time.
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While
reviewing the logbooks, I came across an interesting
bit of history; this original receipt shows the cost
of £46,057.50 (that's over $87,000 at the time of this
writing) for one overhauled Gnome H1200 turbine engine.
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If
the Rolls Royce Gnome turbine were compared 'side by side'
to the General Electric T58 turbo-shaft engine, you'd immediately
notice many similarities.
While individual parts are generally not interchangeable,
some complete assemblies will bolt together. Starting with
the T58, Rolls Royce continued to refine this power plant
by adding many additional features designed to further automate
the operation of this exceptional turbine engine. For instance;
during the start cycle on the T58 you must manually hold the
starter engaged until the turbine spools up over 20%. On the
Gnome once the starter button is depressed, it will stay engaged
until when the turbine spins up to the correct RPM then it
will automatically disengage. Many of the systems on the Gnome
turbines have been improved, or safeguarded in much the same
way. Very interesting.
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This is the Rolls Royce "Coupling Gearbox"
Type 100 that came with these turbines. This aircraft
gearbox would be ideal for a tractor pull as it would
allow two gas turbine engines to output to a single
shaft (power output the the rear wheels could be in
excess of 2800 HP depending on what gas turbine engines
were selected). It will bolt up to several varieties
of T58 or Gnome turbines.
This
gearbox was originally used in several models of helicopters
including the Westland
Wessex 60 twin turbine helicopter.
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Here's the coupling hardware (which connects the power
turbine output shaft to this Rolls Royce reduction gearbox.
Another
view of the type 100 gearbox. It has its own cooling
fan, dry sump lubrication system, and mounts for two
generators.
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This drawing shows the arrangement of the Gnome turbine
engines utilizing the Rolls Royce coupling gearbox type
100. This combination powered the WS-58
Wessex which proved to be one of Westland's most
successful and enduring aircraft. The Westland
Sea King also flew twin Gnome turbine engines.
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Here's
a view of how the engines are positioned in the fuselage
of the Wessex 60 aircraft. The output shaft exits the
rear of the gearbox and continues aft, upwards at an
angle to the main gearbox to power the main rotor. This
twin Gnome turbine engine configuration is also known
as the 'coupled Gnome'.
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Here's a video of the Westland Sea King helicopter in flight. The
Rolls Royce Gnome turbine can also be successfully converted
to thrust.
I
could use a few Rolls
Royce Gnome parts
Ground
running the Rolls Royce Gnome Turbine
I'm
setting up each turbine engine for ground running (one at
a time while mounted in my modified support cradle).
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I
modified the factory holding fixture for my test cart.
I matched the same (original) square tubing and fabricated
another level below the crossmembers. Now I have enough
room underneath for the batteries and fuel tank.
I raised it up so the turbine intake would be high enough
to help reduce the FOD
hazard
during ground running. Locking casters will help prevent
the cart from 'hauling ass down the street' when I hit
the throttle.
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The
cart is designed to be 'self-contained' so I just roll
it out in my driveway, lock the wheels, and start it
up. It 'turns a lot of heads', but it's not as noisy
as one might think.
I
fabricated an engine control panel, mounted my indicators,
and wired the engine control switches.
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My
test cart includes a self-contained fuel supply system.
Here you can see the electric fuel pump (arrow "D"),
fuel filter/water separator (arrow "E") and
fuel tank (arrow "F").
At
the control panel, the operator can monitor all vital
indications and control the igniters, fuel pump, and
starter. I left room so I can add oil pressure and oil
temperature indicators for the Speed Decreaser Gear
(SDG) when I install my gearbox at a later date.
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Here
is one of the Rolls Royce Gnome gas turbines setup to run
on my test cart. Both turbines 'spool up' and stabilize at
idle right off the starter. All specs are well within limits,
they accelerate real nice. Definitely a 'keeper', this pair
of gas turbines will provide many more years of dependable
service with very little maintenance.
Here's
a short video of my gas turbine engine running on my test
cart
If
the video does not display properly, click
here.
Thanks to all who have contacted me after viewing my movie.
Some common questions seem to keep coming up so I'll try to
address them here;
Yes,
it smokes a little in this video as I was doing a test run
on straight Diesel. The next test run was on 75% Diesel and
25% gasoline and the smoke disappeared. I usually burn Number
One Heating Oil or Kerosene.
Regarding
running a turbine without an intake screen. Yes, there is
always the chance you could FOD
the motor and I don't recommend ground running without a properly
fitted intake screen. In this case, I've taken several steps
to reduce the FOD hazard; I've mounted the motor so the intake
is up high enough to prevent a vortex from forming (and greatly
increasing the chance of sucking FOD down the intake), I've
washed the concrete slab all around the motor (to remove all
traces of gravel, dirt, and debris) prior to ground running,
and my test cart is 'FOD free' (no loose fasteners, no metal
shavings, etc.). Plus, I don't run the turbine at any higher
than about 70% RPM without a load on the Power Turbine. At
just over 70% RPM (indicated on the Gas Generator) the Power
Turbine (while unloaded) can easily approach 100% RPM and
I don't want to 'overspeed' the blades. The suction into the
intake increases dramatically as the throttle is advanced
(greatly increasing the chance of FOD). When this motor is
installed in a boat an intake screen will be properly fitted.
About
the noise; yes it's pretty noisy running in my driveway. To
me it's a lot of 'moving air' rather than the 'high-pitched
whine' a lot of other turbine engines produce. After working
the Flight Deck for many years, I find this particular turbine
to be relatively quiet (both the Rolls Royce Gnome and the
General Electric T-58 sound about the same). I only run it
occasionally (during daylight hours) and when I do, it's only
for a short time. The folks who live around me are very understanding.
Besides, I'm the 'handyman' all my neighbors call when something
breaks, so they don't seem to mind my 'eccentric hobbies'
One
of these gas turbines has been sold; it will be converted
to thrust and installed in an aircraft (possibly a cozy),
but the mate to it is still available. This Rolls Royce Gnome
gas turbine would be perfect to power your helicopter, aircraft,
boat, tractor pull, or other turbine powered project. It has
just over 1,000 hours since overhaul (based on a 2500 hour
overhaul cycle) and comes with aircraft logbooks that documents
all maintenance actions all the way back to the day it arrived
from the factory.
Since
I'm into fast boats, I always enjoy seeing these gas turbines
installed in offshore race boats. With an output of over 1250
HP, this turbine will 'haul ass'!
A
few more details about the Rolls Royce Gnome H1200 Mk660 Turbine
Here's
a closer look at a few of the systems and individual components
on the Gnome Turbine Engine.
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It
takes 8 quarts of lube
oil to perform an oil change. Adding a short section
of hose to a funnel helps get the oil into the lube
oil fill fitting (arrow "A") without making
a big mess. At $20 a quart we don't want a mess.
The
throttle cable attaches to the throttle arm (arrow "B")
once installed in the boat.
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The
"run/stop" valve is called the HP Cock on
the Rolls Royce Gnome (arrow "C"). I put a
temporary wire on the lever while running on my test
cart. Later, this will be controlled by an actuator
or linkage.
The
fuel flow divider controls fuel to the nozzles during
the start/run cycles. A spring-loaded valve restricts
fuel to half the nozzles during start, then (as RPM
increases along with air flow and fuel pressure) the
valve opens to allow fuel to all the nozzles.
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The
mounting pad for the fuel flow divider is up under the
combustion section (arrow "G").
Here
the output signal of the Tachometer Generator has been
tapped to drive the Percent RPM Indicator (arrow "H")
until I can locate the correct canon plug. The Alumel/Chromel
connections for the Exhaust Gas Temperature (EGT) indicator
are on top of the Gas Generator (arrow"I")
and (arrow "J").
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The
throttle arm (arrow "K") moves vertically
(linked to the computer) and controls the turbine speed
from idle to wide open.
The
ignition system includes the Igniter plug (arrow "L"),
the shielded igniter wire (arrow "M"), and
the igniter power supply (arrow "N"). Considered
part of the airframe, the igniter wire and power supply
stays with the aircraft when the engine is pulled, so
I installed one on my test cart for ground running the
Gnome.
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The
Fuel Control is a Hydro-Mechanical unit that precisely
meters fuel to the burners.
The
correct fuel amount is constantly computed by monitoring
Gas Generator RPM, engine load, throttle position, ambient
air temperature, and Exhaust Gas Temperature.
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The
fuel control mounts on the underside of the Gas Generator
and is driven off the accessory pad.
Here you can see the pressure bellows and vacuum capsule
inside the Flow Control Unit.
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Here's
the overview of the Fuel Pump and Flow Control Unit
(what Rolls Royce calls the Fuel Control).
A cutaway diagram shows the internal parts of the Gnome
Fuel Control.
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The
engineering Rolls Royce puts into these machines is very impressive.
Everywhere I look, the quality is evident and it's clear to
me that every component was designed for reliability. This
Rolls Royce gas turbine will provide many years of dependable
service powering any turbine powered project.
This
configuration of the Rolls Royce Gnome H1200 Mark 610 powers
the Agusta Bell 204
The
extreme example of dependability, this engine flew flawlessly
for 1400 hours powering a single engine Bell 204 military
helicopter. With lots of life left till next overhaul (due
at 2500 hours) this engine is now available to power your
aircraft or turbine powered project. It comes in 'airworthy
condition' with starter, logbooks, gearbox, holding fixture,
factory maintenance manual, and 24 quarts of the correct synthetic
turbine oil. I can be reached by e-mail
to address your concerns.
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In this view from above you can see the overall layout.
The output shaft leaves the gearbox and runs forward
to the main gearbox (located near the intake when installed
in the helicopter).
The
lube lines are shown at the end of the gearbox.
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Here the output shaft runs alongside the Inlet Guide
Vanes (IGV) actuator. The starter is inside the silver
cover.
This
view shows the fuel control, IGVs, and intake.
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The Speed Decreaser Gearbox (SDG) tucks up inside the
exhaust cheeks for a very compact assembly. The output
shaft on this model runs forward, but is easily changes
to run aft (if desired).
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A
look inside the Rolls Royce Gnome H1200 Mk 660 turboshaft
helicopter engine
These
graphics are just a sample of the many detailed illustrations,
charts, and diagrams presented in my Rolls Royce Turbine Maintenance
Manual.
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This
diagram details the temperature and pressure of the
gasses as they flow through the turbine engine.
Here
the fuel flow and fuel control systems are described
in functional detail.
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The
GE T58 turboshaft and Rolls Royce Gnome turbo-shaft
engines both incorporate an automated system that varies
the inlet blade angle according to engine load. The
Inlet Guide Vane (IGV) system is one of several features
that enable these motors 'squeeze out every bit of horsepower'
and boast such exceptional power-to-weight ratios.
The
Power Turbine captures the power of the expanding exhaust
gasses (from the turbine gas generator section) and
turns it into usable shaft horsepower. It's pretty amazing
when you consider this single row of blades puts out
almost 1400 HP.
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This
diagram shows the internal components of the Rolls Royce
Gnome (series) Gas Turbine.
This
Rolls Royce Speed Decreaser Gear (SDG) is used on some
(single turbine motor) aircraft applications reducing
the Power Turbine output from over 20,000 rpm down to
a usable level of around 6,000 rpm (at 100%). It's shown
'upside down' in this view.
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Rolls
Royce Gnome Turbine Engine
Fuel and Lube Oil Requirements
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