REMOVABLE REACTIVATION PACK FOR A TURBOSHAFT
ENGINE, ARCIDTECTURE OF A PROPULSION SYSTEM OF A
MULTI-ENGINE HELICOPTER EQUIPPED WITH SUCH A PACK
AND CORRESPONDING HELICOPTER
1. Technical field ofthe invention
The invention relates to a reactivation pack for a turboshaft engine of a
helicopter which is capable of operating in at least one standby mode during a
stable flight of the helicopter, and is referred to as a hybrid turboshaft engine.
10 The invention also relates to an architecture of a propulsion system of a
15
multi-engine - in particular twin-engine or triple-engine - helicopter equipped
with at least one such reactivation pack. The invention also relates to a helicopter
comprising a propulsion system having such an architecture.
2. Technological background
As is known, a twin-engine or triple-engine helicopter has a propulsion
system comprising two or three turboshaft engines, each turboshaft engine
comprising a gas generator and a free turbine which is rotated by the gas
generator and is rigidly connected to an output shaft. The output shaft of each free
20 turbine is suitable for putting into motion a power transmission gearbox, which
itself drives the rotor of the helicopter.
It is known that the turboshaft engines of the helicopter operate in modes
which are dependent on the flight conditions of the helicopter. Throughout the
following text, a helicopter is said to be in a cruise flight situation when it is
25 progressing in normal conditions, during all the phases of the flight, apart from
transitional phases of take-off, ascent, landing or hovering flight. Throughout the
following text, a helicopter is said to be in a critical flight situation when it is
necessary for it to have available the total installed power, i.e. during the
transitional phases of take-off, ascent, landing and the mode in which one of the
30 turboshaft engines is malfunctioning, referred to by the abbreviation OEI (One
2
Engine Inoperative).
It is known that, when the helicopter is in a cruise flight situation, the
turboshaft engines operate at low power levels, below their maximum continuous
power. These low power levels give rise to a specific consumption (hereinafter
5 SC), defined as the ratio between the hourly consumption of fuel by the
combustion chamber of the turbo shaft engine and the mechanical power supplied
by this turboshaft engine, greater than around 30 % of the SC of the maximum
takeoff power, and therefore overconsumption of fuel in cruise flight.
Moreover, the turboshaft engines of a helicopter are designed so as to be
I 0 oversized in order to be able to keep the helicopter in flight in the event of failure
of one of the engines. This flight situation corresponds to the OBI mode described
above. This flight situation occurs following the loss of an engine, and results in
each functioning engine providing a power that is significantly greater than its
rated power in order to allow the helicopter to overcome a dangerous situation,
15 and to then continue its flight.
At the same time, the turboshaft engines are also oversized so as to be able
to ensure flight over the entire flight range specified by the aircraft manufacturer,
and in particular flight at high altitudes and during hot weather. These flight
points, which are very restrictive, in particular when the helicopter has a mass that
20 is close to its maximum take-off mass, are only encountered in specific use cases.
These oversized turboshaft engines are disadvantageous in terms of mass
and fuel consumption. In order to reduce this consumption in cruise flight, it is
envisaged to put one of the turboshaft engines into standby during flight. The
active engine or engines then operate at higher power levels in order to provide all
25 the necessary power, and therefore at more favourable SC levels.
In FR1151717 and FR1359766, the applicants have proposed methods for
optimising the specific consumption of the turboshaft engines of a helicopter by
means of the possibility of putting at least one turboshaft engine into a stable
power mode, known as continuous, and at least one turboshaft engine into a
30 particular standby mode that it can leave in a rapid or normal marmer, according
to need. Leaving standby mode is said to have occurred normally when a change
3
in the flight situation requires the turboshaft engine in standby to be activated, for
example when the helicopter is going to transition fi'om a cruise flight situation to
a landing phase. Leaving standby mode normally in this manner occurs over a
period of between 10 seconds and 1 minute. Leaving standby mode is said to have
5 occurred rapidly when a failure or power deficit of the active engine occurs or
when the flight conditions become suddenly difficult. Leaving standby rapidly in
this manner occurs over a period of less than 10 seconds.
A turboshaft engine leaves a standby mode by means of a turboshaft
engine reactivation pack.
10 The applicant has already proposed a number of reactivation packs for a
hybrid turboshaft engine. For example, this reactivation pack can comprise an
energy storage device such as an electrochemical store of the lithium ion battery
type or an electrostatic store of the supercapacitor type, which allows the
turboshaft engine to be provided with the energy required for reactivation and for
15 rapidly reaching a nominal operation mode. According to another proposal by the
applicant, this pack comprises a gas generator having a solid propellant that is
suitable for activating a turbine for driving the shaft of the turboshaft engine.
All of the solutions proposed for reactivating a turboshaft engine m
standby mode have the disadvantage of increasing the weight of the turboshaft
20 engine. The benefit in terms of fuel consumption obtained by placing the
turboshaft engine in standby is thus partly lost by the excess weight caused by the
reactivation pack.
Moreover, during its lifetime, a helicopter may carry out different types of
missions, some of which do not allow the hybrid turboshaft engine to be put into
25 standby. The hybridisation of a turboshaft engine of this kind, i.e. the ability to
put said turboshaft engine into standby and to reactivate it by using a reactivation
pack can, therefore, adversely affect the performance of the helicopter for some
miSSIOnS.
Furthermore, a helicopter of which just one turbo shaft engine is capable of
30 being put into standby mode may age differently from the other turboshaft
engines, thus introducing an imbalance.
>l
4
The inventors have therefore sought a means for maintaining the
performance of a helicopter, irrespective of the missions that it carries out. The
inventors have in particular sought to be able to adapt, without major difficulty, a
helicopter to the missions that it has to carry out. The inventors have also sought a
5 means for balancing the aging of the turboshaft engines in a helicopter.
3. Aims of the invention
The invention aims to provide a turboshaft engine reactivation pack that
can be mounted on a turboshaft engine or removed from the turboshaft engine,
10 according to the flight requirements.
The invention also aims to provide a turboshaft engine reactivation pack
that makes it possible to hybridise a turboshaft engine depending on the
requirements.
The invention also aims to provide a turboshaft engine reactivation pack
15 that makes it possible to balance the aging of the turboshaft engines of a
helicopter.
20
The invention also mms to provide, in at least one embodiment, an
architecture of a propulsion system of a helicopter equipped with a reactivation
pack according to the invention.
4. Disclosure of the invention
In order to achieve this, the invention relates to a removable reactivation
pack for a turboshaft engine of a helicopter, comprising a gas generator equipped
with a shaft, said turboshaft engine being capable of operating in at least one
25 standby mode during a stable flight of the helicopter, said removable pack
comprising:
30
a removable gearbox comprising a gem·box output shaft;
controlled means for rotating said gearbox output shaft, referred to
as reactivation means of said turboshaft engine,
mechanical means for reversibly coupling said gearbox output shaft
5
10
5
to said drive shaft of said gas generator.
Furthermore, according to the invention, said reactivation means of said
turboshaft engine comprise at least:
a first reactivation device that is mounted on said gearbox and
comprises a shaft that is referred to as the first gearbox input shaft
and is mechanically connected to said gearbox output shaft, and
controlled means for rotating said first gearbox input shaft so as to
be able to rotate said output shaft,
a second reactivation device that is mounted on said gearbox and
comprises a shaft that is referred to as the second gearbox input
shaft and is mechanically connected to said output shaft, and
controlled means for rotating said second gearbox input shaft so as
to be able to rotate said output shaft.
The invention thus makes it possible to hybridise a turboshaft engine on
15 demand, i.e. to allow the turboshaft engine to be put into standby mode by
providing a turboshaft engine reactivation pack if necessary, said pack being
removable. The pack comprises a removable gearbox, the output shaft of which is
coupled to the shaft of the gas generator using reversible coupling means. The
shaft of the gearbox can therefore be coupled to the gas generator of a turboshaft
20 engine when it is desired to hybridise said turboshaft engine. A removable
reactivation pack according to the invention thus makes it possible to mount the
pack on a turboshaft engine only when a flight undertaken by a helicopter
equipped with this turbo shaft engine is of a type that may encounter a flight phase
during which said turboshaft engine can be put into standby mode. Moreover,
25 during a mission of this kind, it is possible to select the turboshaft engine on
which the removable pack is mounted, such that the aging rates of the different
turboshaft engines of a helicopter can be harmonised. The aim of harmonising
these aging rates may for example be that of matching the maintenance dates of
the different turboshaft engines of a helicopter in order to limit the innnobilisation
30 time of the helicopter. The removable reactivation pack is removed from the
turboshaft engine for all the flights where standby mode is impossible a priori,
6
and this prevents the helicopter from being disadvantaged by unnecessary excess
weight. A turboshaft engine reactivation pack can also be mounted on different
turboshaft engines, and thus on different helicopters. The same pack can therefore
contribute to the hybridisation of different turboshaft engines of different
5 helicopters.
Furthermore, the turboshaft engine reactivation means comprise two
reactivation devices, each device being mounted and suppmted by the removable
gearbox. Mounting the removable gearbox on/removing said gearbox from the
turboshaft engine using the reversible coupling means thus eliminates the
10 mounting/removal of the turboshaft engine reactivation devices. A reactivation
pack according to the invention thus forms a ready-to-use pack (better known by
the term "plug and play"). Each reactivation device further comprises means for
rotating an input shaft in the removable gearbox that is mechanically connected to
the gearbox output shaft. This architecture thus forms two independent units, each
15 unit being formed by a reactivation device and being able to be replaced
independently of one another.
20
Advantageously and according to the invention, said means for reversibly
coupling said gearbox output shaft to said drive shaft of said gas generator are
formed by an accessory gearbox of said turboshaft engine.
According to this variant, the removable pack is coupled to the drive shaft
of the gas generator of the turbo shaft engine by means of an accessory gearbox of
the turboshaft engine. A turboshaft engine accessory gearbox comprises, for
example, a set of pinions that drive the ancillaries necessary for the operation of
the gas generator of the turboshaft engine, and optionally equipment specific to
25 the helicopter, such as air conditioning units or any other accessory. According to
this variant, the removable gearbox output shaft is meshed, in a reversible manner,
with a pinion of the accessory gearbox.
Advantageously and according to the invention, said controlled means for
rotating said first gearbox input shaft of said fust reactivation device are capable
30 of driving said first input shaft at a predetermined speed for a period that is less
than the period required for said means for rotating said second input shaft of said
5
7
second reactivation device to drive said second input shaft at a predetermined
speed, said fust reactivation device thus forming a device for rapid reactivation of
said turboshaft engine, and said second reactivation device forming a device for
normal reactivation of said turboshaft engine.
According to this variant, the two reactivation devices have distinct
features. In particular, the first reactivation device allows rapid reactivation of the
turboshaft engine, for example when the full power of the turboshaft engine in
standby is urgently required on account of failure of another turboshaft engine.
The second reactivation device allows normal reactivation of the turboshaft
10 engine, for example when the helicopter is going to transition from a cruise or
economical flight situation to a landing phase in which the full power of the
engines is required.
Advantageously and according to the invention, said means for rotating
said rapid reactivation device comprise a generator having a solid propellant, a
15 pneumatic turbine that is connected to a pneumatic store, a hydraulic turbine that
is connected to a hydropneumatic store, or an electrical machine that is connected
to an electrical energy store.
Advantageously and according to the invention, the removable coupling
gearbox comprises an intermediate shaft that carries a first intermediate pinion
20 that is meshed with a ring gear carried by said fust gearbox input shaft, and a
second intermediate pinion that is meshed with a ring gear carried by said second
gearbox input shaft, said gearbox output shaft being coupled to said second
gearbox input shaft.
This architecture of the removable gearbox makes it possible, for example,
25 to reduce or increase the speed of the rapid reactivation chain by selecting suitable
gear ratios. The fust input shaft and the second input shaft are preferably parallel
so as to each fmm, together with the associated reactivation device, an
independent unit that can optionally be replaced independently of the other unit.
Advantageously and according to this variant, the first intermediate pinion
30 is mounted on said intetmediate shaft by means of a free wheel that is designed
and oriented so as to be able to rotate said intermediate shaft if said first input
!!
8
shaft is rotated.
The free wheel makes it possible to transfer the mechanical power ofthe
fust input shaft, which is transmitted by the rapid reactivation device, to the
intermediate shaft. The intermediate shaft then transmits the received mechanical
5 power to the output shaft by means of the fust input shaft that is mechanically
connected to said intermediate shaft. In contrast, the power transmitted to the
intermediate shaft by means of the second input shaft is not transmitted to the fust
input shaft by means of the free wheel because said wheel slides. This makes it
possible to protect the rapid reactivation chain. Furthermore, an architecture of
10 this kind ensures that, when rapid reactivation is required, the power is always
transmitted to the turbo shaft engine, even if the normal reactivation device is also
active. In other words, the rapid reactivation chain overrides the normal
reactivation chain.
According to another variant, the gearbox may comprise two intermediate
15 shafts, a first intermediate shaft that carries the fust intermediate pinion that is
meshed with the pinion carried by said first gearbox input shaft, and a second
intermediate shaft that carries the second intermediate pinion that is meshed with
the pinion carried by said second gearbox input shaft, the two intermediate shafts
being mechanically interconnected, for example by means of a free wheel.
20 Advantageously and according to the invention, the removable gearbox
comprises a sealed casing that comprises a lubrication opening in order to allow
lubrication of the mechanisms of said removable gearbox.
The invention also relates to an architecture of a propulsion system of a
multi-engine helicopter comprising turboshaft engines connected to a power
26 transmission gearbox, characterised in that it comprises:
30
at least one turboshaft engine from said turboshaft engines, referred
to as a hybrid turboshaft engine, which is capable of operating in at
least one standby mode during a stable flight of the helicopter, the
other turboshaft engines operating alone during this stable flight,
a removable turboshaft engine reactivation pack according to the
invention, which is mounted on said hybrid turboshaft engine so as
9
to make it possible for said hybrid turboshaft engine to leave a
standby mode on demand.
The invention also relates to a helicopter comprising a propulsion system,
characterised in that said propulsion system has an architecture according to the
5 invention.
The invention also relates to a removable turboshaft engine reactivation
pack, to an architecture of a propulsion system of a multi-engine helicopter, and to
a helicopter equipped with a propulsion system having an architecture of this
kind, characterised in combination by all or some of the features mentioned above
10 or in the following.
5. List of drawings
Other aims, features and advantages of the invention will become apparent
upon reading the following description, which is given purely by way of non-
15 limiting example and relates to the accompanying drawings, in which:
20
25 6.
Fig. 1 is a schematic view of a removable turboshaft engme
reactivation pack according to an embodiment of the invention and
mounted on a turboshaft engine,
Fig. 2 is another schematic view of a removable turboshaft engine
reactivation pack according to an embodiment of the invention,
Fig. 3 is a schematic view of a helicopter comprising a turboshaft
engine equipped with a reactivation pack according to an
embodiment of the invention.
Detailed description of an embodiment of the invention
In the drawings, the scales and the propmtions are not respected for the
sake of illustration and clarity.
Fig. 1 is a schematic view of a removable turboshaft engine reactivation
pack 5 according to an embodiment of the invention and mounted cin a turboshaft
30 engine 6 of a helicopter.
Said turboshaft engine 6 comprises a gas generator 7 and a fiee turbine 8
10
that is rotated by the gases produced by the gas generator 7. For this purpose, the
gasgenerator 7 comprises an air compressor 9 that is supplied with air by an air
inlet (not shown in the drawings). The compressor 9 supplies a fuel, in the
compressed air, to a combustion chamber 10, which fuel delivers burned gas that
5 provides kinetic energy. Furthermore, a turbine 11 for partially expanding the
burned gas is coupled to the compressor I 0 by means of a drive shaft 12 so as to
be able to rotate the compressor 10 and the equipment necessary for the operation
of the gas generator or the helicopter. The resultant portion of the burned gas
drives the free power transmission turbine 8 which is mechanically connected to a
10 power transmission gearbox 22 by means of a free wheel 21.
The removable pack 5 for reactivating the turboshaft engine 6 comprises a
removable gearbox 30 comprising a gearbox output shaft 31, a device 32 for rapid
reactivation of the turboshaft engine 6 that is mounted on the gearbox 30, and a
device 33 for normal reactivation of the turboshaft engine 6 that is mounted on the
15 gearbox 30. The rapid reactivation device 32 further comprises a gearbox input
shaft that is referred to as the first gearbox input shaft 34 and is mechanically
connected to the output shaft 31 by means of a system of gears that is described in
detail in relation to Fig. 2. The normal reactivation device 33 also comprises a
gearbox input shaft that is referred to as the second gearbox input shaft 35 and is
20 also connected to the gearbox output shaft 31 by means of a system of gears that
is described in relation to Fig. 2.
The reactivation pack further comprises means for reversibly coupling the
gearbox output shaft 31 to the drive shaft 12 of the gas generator 7. These means
are formed by an accessory gearbox 14 of the turbo shaft engine 6. In other words,
25 the output shaft 31 can be coupled to/disconnected from a pinion 15 of the
accessory gearbox 14 of the turboshaft engine 6.
A reactivation pack according to the invention can therefore be easily
mounted on/removed fi'om a turboshaft engine 6 depending on the requirements
of the mission of the helicopter on which the turboshaft engine 6 is installed.
30 Fmihermore, the turboshaft engine 6 and the turboshaft engine reactivation
devices 32, 33 are controlled by a dedicated inspection-control device, which is
11
not shown in the drawings for reasons of clarity.
Fig. 2 is a detailed view of an architecture of the gearbox 30 and in
particular of the system of gears mechanically connecting the input shaft 34 of the
rapid reactivation device 32 and the input shaft 35 of the normal reactivation
5 device 33 to the gearbox output shaft 31. The gearbox 30 comprises a casing 50 in
which the system of gears is housed. Each reactivation device comprises a plate
62, 63 that is fixed to the casing 50 by screw/nut means, which are not shown in
the drawings for reasons of clarity.
Said system of gears comprises the shaft 34 that is mounted on bearings 44
10 supported by the casing 50, and the shaft 35 that is mounted on bearings 45
supported by the casing 50. The shafts 34 and 31 are parallel and have a centre-tocentre
distance that is, for example, less than 200 mm so as to form a compact
gearbox that can be easily handled by an operator during operations for
mounting/removing the pack. The shaft 34 further comprises a ring gear 54 that is
15 meshed with a pinion 57 carried by an intermediate shaft 37. Said intermediate
shaft 37 is mounted on bearings 47 of the casing 50. According to the
embodiment in the drawings, the pinion 57 is mounted on the intermediate shaft
37 by means of a free wheel 25. The intermediate shaft 37 further comprises a
pinion 58 that is meshed with the ring gear 55 of the shaft 35 connected to the
20 normal reactivation device 33. The free wheel 25 is oriented such that a rotation
of the shaft 34 causes a rotation of the intermediate shaft 37, which shaft itself
rotates the shaft 35. In contrast, rotating the intermediate shaft 37 by means of the
shaft 35 does not rotate the shaft 34. In this configuration, the free wheel 25
slides.
25
30
The casing 50 further comprises an opening 51 for lubricating the system
of gears. This makes it possible to simultaneously lubricate the pinions, the ring
gears and the free wheel of the system of gears.
Each reactivation device further comprises controlled means for rotating
the gearbox input shaft to which said reactivation device is connected.
For example, the controlled means 32 for rotating the first gearbox input
shaft 34 of the rapid reactivation device comprise a generator having a solid
12
propellant, or a pneumatic turbine connected to a pneumatic store, or a hydraulic
turbine connected to a hydropneumatic store, or an electrical machine connected
to an electrical energy store. In general terms, these are means suitable for rapidly
inducing the movement of said first gearbox input shaft 34 at a high rotational
5 speed, for example of over 30,000 rotations/minute, in order to rapidly induce the
movement of the gearbox output shaft 31 and thus rapidly reactivate the
turboshaft engine 6 to which the reactivation pack is connected.
The controlled means 33 for rotating the second gearbox input shaft 35 of
the rapid reactivation device comprise, for example, a starter/generator suitable
I 0 for rotating the shaft at a speed of approximately 10,000 to 20,000
rotations/minute.
The invention also relates to an architecture of a propulsion system of a
multi-engine helicopter, comprising turboshaft engines 6, 16 that are connected to
a power transmission gearbox 22, as shown in Fig. 3. According to this
I 5 architecture, a turboshaft engine 6 is equipped, by means of the accessory gearbox
thereof, with a removable reactivation pack as described in relation to Fig. 1 and
2.

CLAIMS
1. Removable reactivation pack for a turboshaft engine (6) of a helicopter,
10
comprising a gas generator (7) equipped with a drive shaft (12), said
turbo shaft engine ( 6) being capable of operating in at least one standby mode
during a stable flight of the helicopter, said removable pack comprising:
a removable gearbox (30) comprising a gearbox output shaft (31 ),
controlled means (32, 33) for rotating said gearbox output shaft
(31 ), referred to as reactivation means of said turboshaft engine,
comprising at least:
• a frrst reactivation device (32) that is mounted on said
gearbox (30) and comprises a shaft that is referred to as the
15 frrst gearbox input shaft (34) and is mechanically connected
to said gearbox output shaft (31 ), and controlled means for
rotating said first gearbox input shaft (34),
• a second reactivation device (33) that is mounted on said
gearbox (30) and comprises a shaft that is referred to as the
20 second gearbox input shaft (35) and is mechanically
connected to said output shaft (31 ), and controlled means for
rotating said second gearbox input shaft (35),
mechanical means (14) for reversibly coupling said gearbox output
shaft (31) to said drive shaft (12) of said gas generator.
25 2. Pack according to claim 1, characterised in that said means for reversibly
coupling said gearbox output shaft (31) to said drive shaft (12) of said gas
generator are fmmed by an accessory gearbox (14) of said turboshaft engine
(6).
3. Pack according to either claim 1 or claim 2, characterised in that said
30 controlled means for rotating said first gearbox input shaft (34) of said first
reactivation device (32) are capable of driving said frrst input shaft (34) at a
14
predetermined speed for a period that is less than the period required for said
means for rotating said second input shaft (35) of said second reactivation
device (33) to drive said second input shaft (35) at a predetermined speed, said
first reactivation device (32) thus forming a device for rapid reactivation of
5 said turboshaft engine (6), and said second reactivation device (33) forming a
device for normal reactivation of said turbo shaft engine ( 6).
4. Pack according to claim 3, characterised in that said means for rotating said
rapid reactivation device (32) comprise a generator having a solid propellant,
a pneumatic turbine that is connected to a pneumatic store, a hydraulic turbine
10 that is connected to. a hydropneumatic store, or an electrical machine that is
connected to an electrical energy store.
5. Pack according to any of claims 1 to 4, characterised in that said removable
gearbox (30) comprises an intermediate shaft (37) that carries a first
intermediate pinion (57) that is meshed with a ring gear (54) carried by said
15 fust gearbox input shaft (34), and a second intermediate pinion (58) that is
meshed with a ring gear (55) carried by said second gearbox input shaft (35),
said gearbox output shaft (31) being coupled to said second gearbox input
shaft (35).
6. Pack according to claim 5, characterised in that said first intermediate pinion
20 (57) is mounted on said intermediate shaft (37) by means of a free wheel (25)
that is designed and oriented so as to be able to rotate said intermediate shaft
(37) if said fust input shaft (34) is rotated.
7. Pack according to any of claims 1 to 6, characterised in that said removable
gearbox (30) comprises a sealed casing (50) that comprises a lubrication
25 operung (51) in order to allow lubrication of the mechanisms of said
removable gearbox.
30
8. Architecture of a propulsion system of a multi-engine helicopter comprising
turbo shaft engines ( 6, 16) connected to a power transmission gearbox (22),
characterised in that it comprises:
at least one turboshaft engine ( 6) from said turboshaft engines,
referTed to as a hybrid turboshaft engine, which is capable of
5
10
15
15
operating in at least one standby mode during a stable flight of the
helicopter, the other turboshaft engines operating alone during this
stable flight,
a removable turboshaft engine reactivation pack (5) according to
any of claims 1 to 7, which is mounted on said hybrid turboshaft
engine ( 6) so as to make it possible for said hybrid turboshaft
engine to leave a standby mode on demand.
9. Helicopter comprising a propulsion system, characterised m that said
propulsion system has an architecture according to claim 9.