U.S. patent number 3,744,743 [Application Number 05/071,319] was granted by the patent office on 1973-07-10 for helicopter power plant system.
This patent grant is currently assigned to Gates Learjet Corporation. Invention is credited to Robert E. Head, John M. McDermott, Richard E. Moore, Harvey O. Nay, Frank S. Okamoto.
United States Patent |
3,744,743 |
Nay , et al. |
July 10, 1973 |
HELICOPTER POWER PLANT SYSTEM
Abstract
Two turbine engines power the craft. They are positioned at the
main rotor hub region just above the cabin. Each engine extends
laterally, cross-ship. A simplified transmission/gearing system
results. Also, should one engine fail, the other readily takes over
alone. A nacelle encloses each lateral engine, in the form of a
stub wing. The nacelles are set at a positive incidence angle, and
provide a substantial lift that unloads the main rotor and saves in
the overall horsepower requirement. They are of relatively small
down area, to minimize downloading due to rotor downwash. Their
leading edge has an inlet slot for engine air. The exhaust ports
are in their outboard edges to direct the noise and hot gases away
from the craft. The wing-like nacelles are symmetricaly arrayed,
and aerodynamically as well as esthetically integrated with the
helicopter.
Inventors: |
Nay; Harvey O. (Palos Verdes
Estates, CA), Okamoto; Frank S. (Torrance, CA), Head;
Robert E. (Palos Verdes Estates, CA), Moore; Richard E.
(Los Angeles, CA), McDermott; John M. (Torrance, CA) |
Assignee: |
Gates Learjet Corporation
(Wichita, KS)
|
Family
ID: |
22100582 |
Appl.
No.: |
05/071,319 |
Filed: |
September 11, 1970 |
Current U.S.
Class: |
244/17.11;
244/55; 244/6; 416/170R |
Current CPC
Class: |
B64C
27/12 (20130101) |
Current International
Class: |
B64C
27/12 (20060101); B64C 27/00 (20060101); B64c
027/12 () |
Field of
Search: |
;416/170 ;60/39.35
;244/17.11-17.27,6,7,6R,7R,7C,53R,54,55 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Buchler; Milton
Assistant Examiner: Sauberer; Paul E.
Claims
We claim:
1. A helicopter comprising:
a fuselage;
a main rotor rotatably mounted over the fuselage;
a drive shaft for the main rotor;
two turbine engines supported on the fuselage with their
longitudinal axes extending generally laterally from and
substantially perpendicular to the longitudinal axis of the
fuselage, the main axis of which is horizontally offset with the
extension of the axes of the turbine engines and the longitudinal
axis of each of the engines being substantially parallel to each
other; and
transmission means coupling the power output shafts of both engines
with said drive shaft to power said rotor.
2. A helicopter according to claim 1, further including a nacelle
about each engine formed to provide relatively low drag and an
upward lift to the helicopter.
3. A helicopter according to claim 2, in which said nacelles are
arranged at a positive incidence angle to provide significant
upward lift in flight.
4. A helicopter according to claim 2, in which each nacelle has an
air inlet for the contained engine, and an exhaust port therefor at
a separate location.
5. A helicopter comprising:
a fuselage;
a main rotor rototably mounted over the fuselage;
a drive shaft for the main rotor;
turbine engines supported on the fuselage with the longitudinal
axes of the engines extending generally from said fuselage and
substantially perpendicular to the longitudinal axis of the
fuselage and the longitudinal axis of each of the engines being
substantially parallel to each other,
said turbine engines having turbine wheels positioned to spin in
planes that do not intersect said fuselage; and
transmission means coupling the power output shafts of said engines
with said drive shaft to power said rotor.
6. A helicopter according to claim 5, in which said transmission
means is planetary gearing, a driven gear connected with said rotor
drive shaft, said driven gear being coupled centrally with said
planetary gearing.
7. A helicopter according to claim 6, further including a coupling
unit between each said engine output shaft and said planetary
gearing.
8. A helicopter according to claim 7, in which each said engine
when disabled is readily disconnected from said planetary gearing
across its said coupling, and thereby permit the remaining engine
to power the helicopter.
9. A helicopter comrpising:
a fuselage;
a main rotor rotatably mounted over the fuselage;
a drive shaft for the main rotor;
turbine engines supported on the fuselage with their longitudinal
axes extending laterally from the fuselage and substantially
perpendicular to the longitudinal axis of the fuselage and the
longitudinal axes of the engines being substantially parallel to
each other;
nacelles laterally extending from each side of the fuselage
encompassing the engines,
said nacelles formed to provide relatively low drag and an upward
lift to the helicopter, and
said nacelles further having a wing-like shape and extending
outboard little beyond the encompassed engines whereby low download
effects due to rotor downwash are exerted thereon; and
transmission means coupling the power output shafts of both engines
with said drive shaft to power said rotor.
10. A helicopter according to claim 9, in which said nacelles are
arranged at a positive incidence angle to provide significant
upward lift in flight.
11. A helicopter according to claim 9, in which the leading edge of
each said nacelle has an air inlet for the contained engine, and
the outboard edge thereof provides an exhaust port therefor.
12. A helicopter comprising:
a fuselage;
a main rotor rotatably mounted over the fuselage;
a drive shaft for the main rotor;
engines supported on the fuselage with their longitudinal axes
extending laterally thereof;
nacelles about each engine formed to provide relatively low drag
and an upward lift to the helicopter,
said nacelles having a wing-like shape and extend outboard little
beyond their respective engines, whereby low download effects due
to rotor downwash are exerted thereon,
and further in which the nacelles and their engines therein are
positioned near the top region of the central cabin section and
extend to the main rotor hub; and
transmission means coupling the power output shafts of both engines
with said drive shaft to power said rotor.
Description
BACKGROUND AND SUMMARY OF THE INVENTION
The engine power plant for helicopters have heretofore been located
for utility with little concern as to final appearance of the craft
or their resultant drag. Further, the transmission from engines to
main rotor shaft required gearing and mechanism that added cost and
weight, and reduced reliability.
In accordance with the present invention, two engines are
positioned laterally across the craft, at the main rotor hub level
above the main cabin. They are directly coupled to the main rotor
drive shaft through simple planetary gearing. Should one engine
fail, the remaining one can safely power the helicopter. Each
engine is enclosed in a fairing that extends only little beyond the
engine. Air inlets for the engines are provided at the leading
edges of the nacelles. The engine exhaust is directed outwardly
through a port at the outer edge of its nacelle.
The nacelles are in effect stub-wings, with a minumum plan area to
keep down thrust low due to the rotor downwash. They extend
relatively little laterally for the same reason. Yet they
streamline the engines with resultant low drag. Further, the
nacelles, being winglike in form, and set at a positive incidence
angle, provide significant lift. Their upward thrust unloads the
rotor by the order of ten percent. Horsepower requirement is
correspondingly reduced.
The turbine wheels are laterally positioned to spin in planes that
do not intersect the body of the craft. This is an important safety
factor should one disintegrate in flight. The engines readily
disconnect from the main rotor transmission if stalled in flight.
Thus one engine can take over, or if both disabled, autorotation
may promptly proceed, smoothly to a safe landing at a site in a
wide area of selection.
The helicopter hereof is aerodynamically and operationally
efficient, fail-safe and stable. It is esthetically pleasing, which
is advantageous for civilian design of the helicopter.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a plan view of an exemplary helicopter incorporating the
power plant system of the present invention.
FIG. 2 is a front elevational view of the helicopter of FIG. 1,
with its main rotor blades turned 45.degree..
FIG. 3 is a side elevational view of the helicopter of FIGS. 1 and
2, with the main rotor blades oriented as in FIG. 2.
FIG. 4 is a schematic showing of the main rotor drive system
including its two lateral engines.
FIG. 5 is a perspective view of the power plant and drive system
for the main rotor blades, in position in the airframe.
FIG. 6 is an enlarged cross-sectional view through the main rotor
support system at the hub, taken along the line 6--6 in FIG. 4.
DETAILED DESCRIPTION OF THE INVENTION
The exemplary helicopter 10 is designed with an overall
configuration for civilian and executive travel use. Its airframe
is formed with minimum fuselage drag for efficient high-speed
cruise. Central cabin section 11 contains door 12 that opens close
to bottom 15 of the fuselage so that the cabin floor is at a low
level for easy entrance and exit. The cockpit area 14 at the front
has a nose section 16 at its tip. Nose section 16 is arranged to be
removable. It is detachable along its junction with cockpit 14
along the dash-lines 17, 18 to provide easy and direct access to
the avionics, instruments, etc for servicing. Behind the main cabin
area 11 is baggage compartment 19, extending rearwardly to narrowed
end-fuselage section 20, to complete the helicopter body. A drive
shaft 63 (FIG. 5) extends through fuselage section 20 to couple the
central main rotor drive with the tail rotor drive. A drive rod 22
projects from tip 23 of the fuselage (FIG. 1) for the tail rotor,
terminating in an interior take-off gear box (not shown). A tail
rotor drive shaft connects this gear-box (not shown) to the main
rotor drive, seen at 63 in FIG. 5, through damper 64.
The single main lifting rotor 25 has four elastically restrained
blades 40,40 assembled 90.degree.apart. Rotor blades 40, 40 are
arranged with significant flap hinge offset for good flying
qualities with low vibration levels. A static mast structure is
attached directly to the body of the helicopter, as described
hereinafter in connection with FIG. 6. The rotor hub is mounted
thereon by suitable bearings for its rotation. Equivalent main
rotors, per se, may instead be used insofar as the present
invention is concerned.
The rotor blades 40, 40 are coupled at central hub 26. The main
rotor 25 and the tail rotor 21 are driven by laterally disposed
turbine engines 50, 50 within respective wing-like low-drag
nacelles 27, 27. Each engine nacelle 27 contains an air inlet slot
28 at its leading edge that directs air to the contained engine
(50), and an outboard exhaust port 29.
In accordance with the present invention, the fairings 27,27 are
arranged to provide sufficient lift in cruise flight to more than
make up for their drag. They are symmetrical, cross-ship, and
exhibit minimum aerodynamic interference with rotor 25. There is
negligible download on them in flight because of their relatively
small span. In the exemplary helicopter: The main rotor drive shaft
is tilted 4.degree. forwardly from vertical (30), see FIG. 3. The
incidence of the winglike fairings 27, 27 hereof is 6.degree.. The
horizontal tail 31, 31 is arranged at an incidence angle relative
to the engine fairings 27, 27 and the rotor angle, to optimize lift
and moment factors. Wind tunnel tests have shown that
minus-two-degree incidence for tail sections 31, 31 provides these
factors with optimum result and minimum interference.
The tail rotor 21 is a straight forward two-blade type, mounted on
a teetering hinge. It is located laterally of fuselage tip 23
through its drive rod 22. Its rotor blades are closely behind
horizontal tail surfaces 31, 31 yet positioned to avoid mechanical
interference therewith. The vertical tail is composed of an upper
segment 32, and a lower one 33. Vertical tail areas 32, 33 are
sufficiently sized to make the helicopter directionally stable,
even in the extremely unlikely event of loss of the tail rotor (21)
and/or failure of the tail rotor drive system. Vertical tail
surfaces 32, 33 are cambered, and set an an incidence angle to
significantly unload tail rotor 21 in cruise flight, minimize tail
rotor fatigue loads and maximize tail rotor life.
Lower section 33 oF the vertical tail is used as a protective
bumper to keep tail rotor 21 from contacting ground in a tail low
landing, as noted in FIG. 3. The circular tip path of the tail
rotor is indicated by lines 4. The lowest edge 36 of tail section
33 is below tip circle 34. The surface areas of vertical tail
sections 32, 33 serve as a safety barrier against approach to the
tail rotor (21) from the opposite side. This factor, combined with
the proximity of swept-back horizontal tail wings 31, 31 form a
significant safety zone about the tail rotor 21 when the helicopter
is on the ground.
Horizontal tail wing-sections 21, 21 extend symetrically from the
narrow rear portion 20 of the fuselage, as seen in FIG. 1. The tail
sections 31, 31 each are oriented rearwardly, by .alpha..degree..
The disc area under rotating main rotor 25 is indicated by
dash-line circle 35. As seen in FIG. 1, a disc area 35 intersects
radially interior portions of tail wings 31, 31 where the
downloading effect is minimal. The download due to downwash in
hovering is a negligible factor with the exemplary horizontal tail
31, 31. The sweptback extent of its wing sections 31, 31 fall
effectively beyond the downwash within disc area 35 (in hover). The
increasing radial portions of the horizontal wings extend beyond
this downwash. In addition to said swept-back configuration, the
two tail wings 31, 31 are also arranged with a downward sweep, as
best seen in FIG. 2. Their downward sweep is at a substantial
anhedral angle .beta..degree. , being a negative dihedral angle.
The symmetrical rearwardly extending and downwardly projecting
horizontal tail wings 31, 31 provide smooth transition from hover
to forward flight, since the downwash of rotor blades 40, 40
recedes backwardly across the horizontal tail during the
transition. Further details thereof are set forth in our
concurrently filed patent application Ser. No. 71,320, filed on
Sept. 11, 1970, now abandoned for "Helicopter Tail
Configuration."
Turbine engines 50, 50 are incorporated to directly couple to the
central transmission/gearing 55. The engines 50, 50 extend radially
outwardly from the transmission 55. In the preferred embodiment
hereof, the turbine engines 50 are positioned laterally,
cross-ship, as shown in the drawings. As can best be seen from
FIGS. 2 and 3, the extension of the axes of the turbine engines 50
are horizontally offset from the main axis of the fuselage. The
drive shaft 60 for the main rotor assembly 25 is directly
mechanically connected to the center of the transmission/gearing
system 55. Drive shaft 60 is made hollow to save weight. Its driven
gear 61 is secured at its internal end 62, see FIG. 6. The engine
power output drive shafts 51--51 are short, and connect into shafts
52, 52 of the power transmission 55 through flexible end-couplings
53, 53, see FIG. 4. The internal gearing of the transmission 55
hereof is simple, direct, effective and efficient, with a minimum
number of parts. It is significantly less in weight and cost, and
with improved reliability when compared with prior art systems.
A preferred transmission/gearing 55 is a planetary array between
its coupling shafts 52, 52 and the central rotor gear 61. In its
main gearbox 55 engines 50,50 each drive a pinion through an
overrunning clutch. These two pinions in turn drive a single ring
gear that serves as the input to the planetary second stage. The
main rotor shaft 60 transmits only torque to rotor 25. All other
rotor loads are carried through stationary rotor mast 65. Cooling
air is provided for engine 50 and main rotor gearbox 55 by an
engine-driven fan mounted with the accessories 54 of each engine.
Air from each of said fans is distributed to the engine oil cooler
for that engine, to the engine's accessory compartment, and to
one-half of the oil cooler for rotor gearbox 55. The latter assures
adequate gearbox 55 cooling even when one engine is inoperative.
Discharge air from the engine oil cooler is directed to ventilate
the compartment about the hot end of the engine.
The laterally-disposed position of the turbine engines 50,
left-and-right, gives good separation and redundancy to prevent any
disaster that may occur to one engine from spreading to the other
engine. The turbine wheels of each engine 50, 50 are located well
outboard of the fuselage, including the cabin section 11 and
cockpit 14. Said wheels spin in a plane that does not intersect the
fuselage. Thus in the unlikely event of a turbine wheel
disintegrating, and not being contained by the engine case, it
could not endanger the crew or passengers nor damage the hull at
all. The exhaust port 29 of each engine 50 is placed well outboard
where its heat and noise have minimum influence on passenger
comfort.
The lateral position of the engines 50, 50 allows the use of a
wing-like, low-drag fairing 27, 27 to enclose each engine. The
fairings 27, 27 supply enough lift in cruise flight to more than
make up for their drag. This feature is made possible by optimizing
the incidence angles of the engine fairings 27, 27, the rotor 25,
and the horizontal tail 31, 31 as aforesaid. Each nacelle exhibits
minimum aerodynamic interference with the rotor 25, and has
negligible download in hover because of its relatively small span.
A slotted inlet 28, along the leading edge of each fairing 27
directs the inlet air into an efficient inlet plenum-chamber 42 for
each engine 50, see FIG. 5. A firewall 43 forms one wall of chamber
42. The inlet sections 45, 45 of the engines are in chambers 42,
42. An engine forward mount is indicated at 46. The engine exhaust
conducts 47, 47 extend to the respective outport exhaust ports 29,
29.
The exemplary helicopter 10 is a twin-turbine 50, 50 power system.
Either disabled turbine 50 may be arranged to be promptly
disconnected from the power drive system. This is done with the use
of automatically disconnectable couplings at 53, 53 between
turbines 50, 50 and main gear box 55; overrunning clutch couplings;
or other known de-clutching means. It is an important back-up
fail-safe factor in that the remaining engine can safely power the
craft. Also, if a turbine break would not unduly load the
transmission 55 its disconnection is optional. Single-engine
performance of the exemplary helicopter is readily designed to
exceed FAR 29 Category A helicopter requirements.
The main rotor hub 70 is mounted on stationary tubular mast 65 by
support bearings 71, 72, see FIGS. 5 and 6. Hollow mast 65 is
attached to mast base 66, which in turn is directly secured to the
airframe structure 67. This provides main rotor 25 support
independent of the drive system. No once per revolution fatigue
loads are thereby imposed on the static mast. Drive system failure,
even lockup of a gearbox, can be sustained and still allow a safe
autorotational landing. Rotor hub 70 is connected with drive torque
shaft 60 by overhanging members 73, 73, and is coaxial within mast
65 much in the manner of a "full floating" truck wheel. In such way
all forces and bending moments are carried by the stationary mast
65.
All the bearings in the main rotor hub 70 are designed for zero
maintenance. The two grease-packed main rotor bearings 71, 72 go
without attention between major overhauls. The blade 40
flap/feather, lead-lag, and control link bearings are teflon-lined
and need no lubrication. The blades 40, 40 are attached to the
rotor hub 70 by laminated retention straps 73, 73 made of thin,
high-strength steel. The straps 73, 73 transfer the blade
centrifugal forces between the two blades in each opposing pair of
the four-bladed rotor 25; and deliver the engine torque to the
blades (40,40) through their truss shape. Straps 73, 73 also
withstand the alternating flapping, feathering, and chordwise loads
applied by the blades 40, 40, while still being flexible enough to
allow the necessary flapping and feathering motions of the blades.
Such design eliminates the need for the highly loaded, not fully
rotating ball bearings that retain the blades in some prior
helicopters, and so eliminates the brinelling problem associated
with that type of blade retention. The rotor hub is covered with
fairings 74, 74 to minimize aerodynamic drag, and also to protect
its mechanism from dust and dirt, and from icing.
As a final safety backup the helicopter 10 has outstanding
autorotational characteristics. Therefore, even with a highly
improbable dual engine failure or running out of fuel, a safe
power-off landing can be made almost any place with the helicopter.
Its exceptionally low aerodynamic drag also provides a long glide
capability. Thus, for example, for an autorotation from 5,000 feet,
nearly 100 square miles of area are available for choosing an
emergency landing site.
The engine nacelles 27, 27 are aerodynamically shaped to produce
lift with low drag, as herein-above set forth. They are smooth
fairing enclosures for the respective laterally positioned engines
50, 50. Their incidence angle is carefully determined in
conjunction with that for the horizontal tail 31, 31 and the
forward inclination of the main rotor drive. In the exemplary craft
with a forward 4.degree. tilt of the main rotor, the incidence of
these "stub wings" 27, 27 was set at 6.degree., positive. They help
unload the rotor 25 by providing vertical thrust. The nacelles 27,
27 may be said to in effect "pay for themselves" in unloading the
projecting engines. For example, the helicopter 10 with a gross
weight of 6,000 pounds uses shaft horsepower of 600 at 175 m.p.h.,
at an altitude of 5,000 feet. The nacelles 27, 27 at 6.degree.
incidence provides 10 percent of the rotor lift, or 600 pounds. A 5
percent saving in engine power results, namely 30 HP. Other nacelle
incidence angles may be used. Increasing it further may decrease
rotor output power.
It is advantageous to limit the lateral extent of nacelles 27, 27,
as well as hold their plan area to a practical minimum. The reason
is to thereby reduce the downloading action of the main rotor
downwash upon them: the less their plan area and lateral
projection, the less the download. Practical turbine engines 50, 50
for the required power are available with reasonable shaft length,
and good power to weight ratio. The Garrett TSE 231 helicopter
turboshaft engine weighs about 175 pounds, yet develops 475 shaft
horsepower for takeoff under sea level static conditions; with a
continuous maximum of 400 shaft HP. Its power-to-weight ratio is
2.73.
The exemplary helicopter's cabin, arranged to seat 8-12 passengers,
has an outer width of 5 feet. Its gross weight is designed at 6,000
lbs. The tip-to-tip, cross-ship, extent of nacelles 27, 27 is only
11 feet. The main rotor diameter is 40 feet; overall height to top
of vertical tail, 12 feet; height at main rotor hub, 10 feet. The
cross-ship extent of the horizontal tail wings 31, 31 is about 14
feet. The height of the upper tail section 32 extends to 12 feet
above the cabin floor-line; its lower section 33 at bottom 36 to
about 2 feet above. The tail rotor diameter is about 7 feet, and is
positioned 21 inches outwardly from the craft 's central
longitudinal section.
The exemplary "stub wings" 27, 27 each extend laterally from the
top of the cabin 11 by 3 feet. They taper, narrowing outwardly:
being 9 feet longitudinally at their cabin junctures, and 5.75 feet
along their outboard edge. They are streamlined to minimize drag
and provide the lift, as aforesaid; see FIGS. 1, 2 and 3. They are
nacelles that enclose the turbine engines 50 in lateral position
across the craft.
It is to be understood that the fairings 27, 27 may be of other
form, shape and/or size, and remain within the purview of our
present invention. Essentially, they are constructed: (a) to
materially reduce the drag of the engines 50 that would otherwise
be exposed over the cabin; (b) streamlined in form and set at a
positive incidence angle to provide substantial added lift to the
helicopter, even beyond that of the weight of their engines 50, and
thereby help unload the main rotor; (c) with relatively low down
area and short lateral projection to minimize downloading due to
main rotor action; and (d) aerodynamically integrated with the
forward rotor inclination, the horizontal tail incidence and the
fuselage as a whole for efficient, stable operation of the
craft.
Fairings 27, 27 are not wings in the sense of those used in fixed
wing aircraft. They have a relatively small span, and provide a
relatively small proportion of the overall requisite lift; herein
the order of ten percent. Were these "stub wings" extended
laterally outwardly, the resultant down thrust would
correspondingly increase greatly, until a span is reached where
their utility becomes negative. The relatively short engines 50, 50
with the laterally short nacelles 27, 27, as three feet, set at
plus 6.degree. incidence, have been found to be effective, stable
and very useful for the helicopter.
* * * * *