Airship / Helicopter Hybrid Aircraft (Helistat)
Peter Lobner, Updated 21 December 2020
1. Introduction:
There have been many different designs of airship / helicopter hybrid
aircraft (a helistat) in which the airship part of the hybrid aircraft
carries the empty weight of the aircraft itself and helicopter rotors
deployed in some fashion around the airship work in concert to lift
and propel the fully loaded aircraft without the need for an exchange
of ballast.
In this section, we’ll take a look at one heavy-lift helistat that actually
flew (the Piasecki PA-97-34J) and other heavy-lift helistats that have
been described in patents and concepts designs.
• Piasecki Aircraft Corp. helistats (USA, 1955 – 1986)
• NASA heavy-lifter (USA,1975)
• Aerocrane (USA,1975)
• Goodyear buoyant quad-rotor, heavy-lift Dynastat (USA, 1979)
• Rotor-aerostat composite aircraft patent (USA, 2000)
• Hybrid aircraft patent (Canada, 2002)
• Hybrid lift air vehicle patent (Canada, 2007)
• Boeing lighter than air vertical load lifting system (USA, 2007)
• Skyhook International improved hybrid lift air vehicle patent
(Canada, 2009)
• Boeing SkyHook JHL-40 (USA / Canada, 2008 – 2010)
2. Piasecki Aircraft Corp. helistats (USA, 1955 – 1980s)
After engagements with earlier firms, including Piasecki Helicopter
Corporation, Frank Piasecki founded the Piasecki Aircraft Corporation
(PiAC) in 1955 in Essington, PA. The Piasecki Aircraft Corporation
website is here: https://www.piasecki.com
From the mid-1950s through the mid-1980s, Frank Piasecki was a
major force in the development of helistat technology and flight
testing in the US.
1
Piasecki Patent US 3,008,655, “Helicopter and Balloon Aircraft
Unit” (1958)
Frank Piasecki filed a patent application for a “Helicopter and Balloon
Aircraft Unit” on 17 March 1958 and received Patent US 3,008,655 on
14 November 1961. This patent described an early concept for a
helistat with a large, spherical helium balloon coupled to a central
load beam that was connected to two tandem-rotor helicopters by a
rigid cross beam. The helicopters have an integrated control system
that enables a single pilot to fly the helistat. This general
configuration is shown in the following figure.
As described in the patent,
“The present invention relates in general to helicopters, and
more particularly to an assembly of a plurality of interconnected
helicopters and a balloon forming an aircraft unit particularly
suitable for transporting heavy loads…… beyond the normal
capability of helicopters.”
You can read Patent US 3,008,655 here:
https://patents.google.com/patent/US3008665
2
Piasecki Patent US 4,591,112A, “Vectored thrust airship” (1979)
On 12 October 1979 Frank Piasecki and Donald Meyers filed a patent
application for a “Vectored thrust airship,” which was a more
advanced design for a helistat, with a large blimp-shaped aerostat
connected to four individual helicopters with an integrated control
system flown by a single pilot. They received Patent US 4,591,112 A
on 27 May 1986. This patent describes the basic design and
operation of this helistat as follows:
“An airship with provisions for vectored thrust provided by a
plurality of controllable pitch rotor thrust producing units
attached to the elongated aerostat hull spaced from and on
opposite sides of the center of overall mass of the airship. The
pitch control systems for the rotors of all thrust units include
collective and cyclic pitch controls of the main, horizontally
rotating lifting rotors and the control systems are interconnected
to be operable by a master control which establishes both
similar and differential pitch settings of the rotors of selected
thrust units in a manner to establish vectored thrust in
directions which establish the required amounts of vertical lift,
propulsion thrust, trim and control forces to control all flight
aspects of the airship.”
You can read Patent US 4,591,112A here:
https://patents.google.com/patent/US4591112A/en
Frank Piasecki notes, “Semi-rigid pressure envelopes or rigid
envelopes can be adapted to the Hell-Stat concept. The longitudinal
and lateral support beam structure, which serves to attach the
helicopters and support the payload, can be tied structurally to the
structural frames of the rigid envelope. In the case of the semi-rigid
(envelope), the helicopter attachment and load-support beams can be
made integral with the fore-and-aft keel structure.”
3
The patent includes several helistat design concepts, including the
following:
The helistat is comprised of a non-rigid lift gas envelope (10b) and
four helicopters (22b, 23b, 24b & 25b) that are connected via
cantilever arms (15b) to the rigid keel structure (40).
The basic design of the later PA-97-34J helistat was very similar to
the one shown in patent Figures 7 and 8.
4
The Piasecki 75 ton project X-97-0004 (1975)
This helistat design concept had a 75-ton (68 metric ton) payload
capacity based on using four existing CH-53D heavy-lift helicopters
and an aerostat with a gas envelope volume of 3,600,000 ft3 (102,000
m3). The gas envelope’s overall length was 500 ft (152.4 m), with a
diameter of 133 ft (40.5 m). The helistat had an overall height of 155
ft (47.2 m) and an overall width with rotors operating of 292 ft (89 m).
Project X-97-0004 . Source: Frank Piasecki (1975)
The 75 ton heilstat had the following general characteristics:
• Maximum gross weight: 345,940 lb (156,915 kg)
• Empty weight: 177,540 lb (80,531 kg)
• Useful load (payload, crew, fuel & oil): 168,400 lb (76,385kg)
• Payload: 150,400 lb (68,220 kg)
• Cruise speed: 100 mph (161 kph)
• Operating altitude (ferry): 10,000 ft (3,048 m)
• Hover ceiling: 6,000 ft (1,829 m)
• Rate of climb: 500 fpm (vertical), 2,000 fpm (forward flight)
• Range (full load): 160 miles (257 km)
• Range (ferry): 2,000 miles (3,219 km)
5
The Piasecki 140 ton project X-97-0011 “Gargantua” (1975)
Project X-97-0011 "Gargantua" was a design concept for a huge
helistat with a 140 ton (127 metric ton) payload capacity. This helistat
was created from four Sikorsky CH-53E heavy-lift helicopters
connected to a rigid (dirigible) airship with a gas envelope volume of
5,700,000 ft3 (161,400 m3). The aerostat had the streamlined shape
of the Navy’s 1930-vintage dirigible Macon, but with one less middle
section in the hull. Gargantua had an overall length of 770 ft (234.7
m), a hull diameter of 133 ft (40.5 m) and an overall height of 125 ft
(38.1 m). Overall width with the rotors operating was 292 ft (89 m).
The Gargantua was designed for transporting the National
Aeronautics and Space Administration (NASA) Space Shuttle and
other very large cargo items. There was a longitudinal recessed
cargo bay under the hull that would have enabled the Space Shuttle
to have been hoisted up and carried as a semi-submerged load, with
only the wings and lower fuselage outside of the cargo bay.
Project X-97-0011 "Gargantua" helistat. Note scale relative to the
Space Shuttle. Source: Frank Piasecki (1975)
6
The Piasecki project PA-97-212B helistat (1977)
The 1977 project PA-97-212B helistat was designed to use four Bell
212B (UH-1N) "Twin Huey" utility helicopters.
The project PA-97-212B helistat.
Source: Piasecki Aircraft Corporation via US Forest Service
The Piasecki PA-97-34J helistat (1979 – 1986)
In the early 1970s, the US Forest Service initiated Project Falcon,
which was a research and development program for advanced
logging systems to “…provide more wood products for a growing
population and, at the same time, accommodate an increasing
concern over the natural environment.” In the late 1970s, Piasecki
proposed a helistat to the Forest Service to demonstrate a heavy
vertical airlifter for harvesting timber from inaccessible terrain. The
Forest Service expected the helistat to carry 25 tons (one truckload,
22.7 metric tons) of timber for distances of up to 5 miles (8 km) over
steep mountainous terrain.
7
The Piasecki helistat concept for the Forest Service.
Source: Piasecki
The Forestry Service funded development and testing of the PA-97-
34J in 1980 via a $10.7 million contract administered by the Naval Air
Development Center. Total program cost was expected to be $25
million, with $11 million for helistat construction and flight testing and
$14 million for a planned three-year demonstration phase in the
Gifford Pinchot National Forest in Washington State. The Forest
Service expected to recover most of the helistat project costs through
timber sales during the demonstration phase, when the helistat was
expected to harvest nearly $19.6 million worth of timber.
In addition to forest management, Piasecki saw applications for their
helistat for patrolling sea areas, transporting military equipment,
unloading cargo ships, building power lines, oil rigs, residential and
office buildings.
8
Piasecki PA-97-34J was a very large semi-buoyant hybrid airship
comprised of a retired Navy ZPG-2W blimp gas envelope, which
formed the helium-filled aerostat, and four Sikorsky H-34J helicopters
without their tail sections, connected beneath the blimp via a rigid
framework. The basic design parameters for this helistat were:
• Overall length: 343 foot (105 m)
• Overall height: 113 ft (34.4 m)
• Maximum width (rotors turning): 188 ft (60.6 m)
• Aerostat gas volume: 1,000 000 ft3 (28,317 m3)
• Gross weight: 107,051 lb (48,558 kg)
• Empty weight: 54,885 lb (24,895 kg)
• Aerostatic lift: 55,851 lb (25,334 kg)
• Dynamic lift: 51,200 lb (23,223 kg)
• Useful load (payload, crew, fuel & oil): 52,166 lb
• Cruise speed: 60 knots
• Working range (with reserves): 143 miles (230 km)
• Rate of climb: 100 fpm (vertical), 950 fpm (forward flight)
• Ceiling: 8,000 ft (2,438 m)
• Hover ceiling: 3,000 ft (914 m)
In June 1981, the General Accounting Office (GAO) reviewed the
Forest Service’s helistat demonstration program and recommended
that program objectives and progress be reevaluated. At issue were
the lack of end user input to the operational requirements for helistat
logging and a concern that the PA-97-34J may not actually be suited
for demonstrating the economics of aerial logging.
Rigid framework for PA-97-34J. Source: Flight Int’nl 18 Feb 1984
9
Frank Piasecki & rigid helicopter framework for PA-97-34J.
Source: Flight Int’nl 18 Feb 1984
The first static tests of the helistat’s structure were carried out in
1983. The first tethered flights occurred in October 1985 at Lakehurst
Naval Air Engineering Station. The PA-97-34J first flew on 26 April
1986.
Piasecki PA-97-34J helistat. Source: US Navy via Wikipedia
10
Piasecki PA-97-34J helistat in flight.
Source: US Navy via Planes in Polish Aviation
PA-97-34J in flight with US Forest Service markings.
Source: Piasecki Aircraft Corporation via Planes in Polish Aviation
11
After 15 test flights, the PA-97 was destroyed during a flight test at
Lakehurst on 1 July 1986, after a vibration-induced structural failure
resulted in the starboard-aft helicopter breaking free from its
mounting and its rotors cutting the aerostat’s gas envelope. The
other three helicopters also separated from their supporting
framework during the crash, which killed one pilot. Development of
the PA-97-34J was discontinued after the crash.
You can watch a short (4:58 minute) video, “Piasecki PA-97 Helistat |
The craziest aircraft you have never heard of,” at the following link:
https://www.youtube.com/watch?v=qaUhdDLv8Qk
Piasecki advanced helistats
The Piasecki PA-97-34J was the first, and only, US helistat to fly.
Piasecki had expected that this helistat would be the precursor to
much larger helistats. The Vertical Flight Society reports that “Helistat
payload capacities of up to 280 tons have been designed, but no
upper limit has been set on the combined helicopter and airship lift
capacity.”
Example of a Piasecki advanced helistat design.
Source: Piasecki via Vertical Lift Society
12
3. NASA Heavy-Lifter (USA, 1975)
NASA Heavy-Lifter concept, circa 1975. Source: NASA
In the mid-1970s the National Aeronautics and Space Administration
(NASA) had a program to develop concepts for heavy-lift lighter-than-
air (LTA) vehicles for possible civil and military use. One concept,
called the “heavy lifter,” was a semi-buoyant hybrid vehicle with four
helicopter rotor systems supported from a large rigid airship (dirigible)
hull. At sea level, the gas envelope volume of 75,000 m3 (2.5 million
ft3) would provide 83,550 kg (184,196 lb) of aerostatic lift. When
loaded with cargo, a helistat is only semi-buoyant (it is heavier-than-
air), thereby greatly simplifying ground handling requirements. The
helicopter rotor systems provide the dynamic lift to carry heavy loads
without also having to lift the whole weight of the vehicle. In addition,
the helicopter system enables the helistat to precisely hover above a
destination for in-flight cargo pickup or delivery.
This short-haul heavy lifter concept could provide the lifting capacity
needed to deliver heavy power generating equipment of other
industrial equipment, particularly when its destination is a remote
area not served by other heavy transportation systems.
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4. Aerocrane (USA, 1975)
The Aerocrane is an unusual concept, even for a helistat, because
the large, rotating spherical aerostat also is the “hull” of the helicopter
component of the helistat. During operation, the four large rotors (or
wings) rotate at about 11 rpm to generate a controllable amount of lift
and a controllable thrust vector for propulsion and positioning the
Aerocrane during a load exchange. A sling load is supported below a
stabilized control cab that does not rotate.
Aerocrane cutaway drawing. Source: Perkins & Doolittle (1975)
An empty Aerocrane is a lighter-than-air (LTA) vehicle with an
operating empty weight between 31 – 35% of design gross weight. In
comparison, the empty weight of a heavy lift helicopter is between 57
– 72% of design gross weight, leaving much less margin for carrying
cargo.
Aerostatic lift supports two-thirds of the Aerocrane’s design gross
takeoff weight, including payload. This means that the aerostat
supports the full structural weight of the hybrid vehicle and up to 50%
of the design sling load, while aerodynamic lift from the rotors only
need to support the remaining 50% of the sling load.
14
In their 1975 paper, authors R. G. Perkins & D. B. Doolittle reported:
• The primary advantages of the Aerocrane are:
o VTOL load capacity greatly exceeds heavy-lift helicopter
capacity and eliminates the common airship problem of
ballast transfer during a load exchange
o The rotor provides 360° vectorable thrust to supply a
relatively large force component for mitigating gust loads
o Symmetrical shape reduces the mooring problem of
airships
• The primary penalties of the Aerocrane are:
o Larger and more cumbersome than a helicopter
o Reduced forward speed envelope; a 40 knot design
cruise speed seems to be practical
• Principal areas of uncertainty to be addressed in a development
program are:
o Aircraft stability and control characteristics
o Practical modes of operation considering its airship-size
bulk, speed envelope, and potential gust sensitivity
• The Aerocrane is best suited for short range, high load/unload
cycle missions where loads are in excess of helicopter
capabilities
• The Aerocrane does not compete directly with helicopters
because the concept does not scale down to helicopter load
size. The Aerocrane also does not compete with airships
because it cannot offer efficient long range service comparable
to an airship.
You can read their complete paper here:
• R. G. Perkins & D. B. Doolittle, “Aerocrane: A hybrid LTA
aircraft for aerial crane applications,” Proceedings of the
Interagency Workshop on Lighter than Air Vehicles, NASA-CR-
137800, pp. 571 - 584, Doc ID 19760007975, 1 January 1975:
https://ntrs.nasa.gov/citations/19760007975
15
5. Goodyear Aerospace Corp. quad-rotor, heavy-lift Dynastat
(USA, 1979)
In the 1960s and 1970s, Goodyear developed several design
concepts for a class of semi-buoyant hybrid airships they called
“Dynastats.” In a Dynastat, the aerostatic lift of the airship carries
most or all of the deadweight of the airship while vectored thrust
propulsion and aerodynamic lift share the weight of the cargo
throughout the flight envelope, from vertical takeoff and landing
(VTOL) to level cruise flight.
Goodyear Aerospace airship development continued through the
1970s. In 1979, it was reported that the corporate R&D funded
airship program was focused on heavy-lift airships and maritime
patrol applications. One example of Goodyear’s work during this
period is the quad-rotor, heavy-lift Dynastat shown below. In spite of
its Dynastat name, this hybrid craft was a helistat. This basic
configuration has a cylindrical airship hull with a rigid framework
supporting the quad-rotor modules. Auxiliary horizontal-thrusting
propellers are shaft-driven from the associated main rotors. These
Dynastat propulsion modules were optimized for high reliability and
low maintenance and would be de-rated relative to comparable,
lighter weight, higher performance helicopter propulsion systems.
Goodyear 1979 concept for an advanced quad-rotor,
heavy-lift Dynastat. Source: AIAA Paper 79-1611 (1979)
via NASA Technical paper 1921 (1981)
16
6. Rotor-Aerostat Composite Aircraft patent (USA, 2000)
US Patent 6142414A; “Rotor-Aerostat Composite Aircraft”; published
7 November 2000; applicant: Donald B. Doolittle; assignee: All
American Industries, Inc., Wilmington, DL; available here:
https://patentimages.storage.googleapis.com/32/99/58/58779b2aeb7
acf/US6142414.pdf
Abstract: “A composite aircraft comprising an aerostat containing a
lighter than air gas, and a rotor assembly mounted to and below the
aerostat, via an axle. The aerostat provides buoyancy to lift the
weight of the aircraft plus a significant portion of the payload
connected to the aircraft. The rotor assembly statically connects to
the aerostat in all aspects except rotationally about the axle, and
provides the remaining lift and propulsion to the aircraft and payload.”
17
7. Hybrid aircraft patent (Canada, 2002)
European Patent Application EP 1209076A2; “Hybrid Aircraft”;
published 24 October 2002; applicant & inventor: Hans-Jurgen Bothe,
Albert, Canada; available here:
https://patents.google.com/patent/EP1209076A2
Abstract: “A hybrid aircraft having VTOL R-VTOL and S-STOL
capabilities having a lifting body hull (1) and four wing sections (20)
arranged in tandem which are pivotally moveable about their neutral
axis. Each wing section has mounted thereon a pivotal propeller-rotor
(21) assembly for providing thrust substantially in a range between
horizontal and vertical. The wings and propellers are integrated to the
hull by an outrigger designed to be very stiff and to distribute forces
from the wings and propellers from the hull. The hull is shaped to
provide aerodynamic lift in an airstream and to facilitate construction
by minimizing the number of panels of differing curvature required.
The hull is formed of a pressure-tensioned frame covered with semi-
rigid panels, a lower cladding frame and bow and stem cladding nose
cones. ……. A turbo-electric drive system can be used to drive the
aircraft.”
18
19
8. Hybrid Lift Air Vehicle patent (Canada, 2007)
US Patent 8167236 B2; “Hybrid Lift Air Vehicle”; filed 27 August
2007; published 6 March 2008; patent granted 1 May 2012; inventor:
Peter Jess, Calgary, Canada; assignee: Shell Technology Ventures
Fund; available here:
http://www.jessco.ca/assets/us-patent-8167236-hybrid-lift-air-vehicle-
--peter-jess.pdf
Abstract: “A hybrid lift air vehicle for lifting and transporting a
payload to a delivery location, which comprises a helium or other
lighter-than-air gas filled envelope mounted on an airframe. Variable
and reversible vertical thrusters are positioned on the airframe, and at
least two variable and reversible lateral thrusters are mounted on the
envelope or mounted on truss arms attached and extending out from
the airframe, Wherein, when the vehicle is connected to the payload
for transport, the helium or other lighter-than-air gas supports or
substantially supports the weight of the vehicle and the vertical
thrusters are then continuously engaged to support the weight of the
payload and to provide lift to the payload, Wherein the lateral
thrusters are then engaged to effect lateral movement of the vehicle
to the delivery location, Whereby, once at the delivery location, the lift
provided by the variable and reversible vertical thrusters is reduced or
reversed so as to allow the air vehicle to descend and the payload to
again engage the ground surface, and where necessary, the variable
and reversible vertical thrusters may be reversed to facilitate the
unloading of the payload from the vehicle, the vehicle continuing to
be kept aloft, once unloaded, by the helium or other lighter than air
gas. In this manner, the vehicle utilizes the helium or lighter than air
gas to offset or substantially offset the weight of the vehicle, the
vertical thrusters providing the power to lift the payload.”
The counterpart international patent is WO2008/025139A1, which is
available here:
https://patents.google.com/patent/US8141814B2/en?oq=8%2c1
41%2c814
20
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9. Boeing lighter than air vertical load lifting system (USA, 2007)
Patent US8141814B2; “Lighter-than-air vertical load lifting system;”
filed 26 November 2007; patent granted 27 March 2012; inventor:
Richard Kulesha; assignee: Boeing; available here:
https://patents.google.com/patent/US8141814B2/en?oq=8%2c141%2
c814
Summary: “The present disclosure provides an aerial load lifting
system that overcomes ……. disadvantages of the prior art by
providing a neutral buoyancy or lighter-than-air aircraft comprising
non-rigid or blimp-type lighter-than-air envelope surrounded at least
in part by a structural shell. The structural shell contains the lighter-
than-air envelope, and supports the cargo load, the engine(s), fuel
tank(s), rotors, and transmission system(s) that power the lift and
vectoring of the aircraft. The structural shell is designed to transfer
the weight of the load essentially directly to the location of the rotors,
thus avoiding unnecessary stress on the envelope. Utilizing a
structural shell instead of utilizing a conventional frame or truss
structure, large booms or hanging the apparatus from either a cable
or from multiple cables from the balloon as in the prior art provides
significant advantages, since we make a shell lighter than a “frame”.
The system is designed so that the envelope provides essentially
neutral buoyancy for the structure including the structural shell,
engines, fuel tanks, rotors and transmissions, leaving essentially only
the cargo weight to be lifted by the rotors. Preferably, but not
necessarily the rotor controls are similar to standard helicopter rotor
controls. Thus, the present disclosure provides a relatively compact
and simple design for an aerial lifting system that is capable of
transporting very heavy loads to remote locations.”
Patent Figure 1A is a profile view of the Boeing helistat. The non-rigid
(blimp) gas envelope (10) is partially enclosed by a rigid structural
shell (50) that supports the engines (100), tandem rotors (200),
cockpit (52) and retractable landing gear (54). The propulsion train
consists of tandem rotors (200), two engines (200), two transmissions
(120) and drive shaft (140) to deliver power to the front transmission
and rotor.
22
The cargo (20) is carried as an external sling load suspended by
cables (32) from four cargo hooks (30) on the rigid structural shell.
Patent Figure 1b is a cross-section
view of the Boeing helistat. The gas
envelope (10) is shown inside the rigid
structural shell (50). The twin engines
(100) flank the rear rotor (200). The
cargo (20) is suspended by cables
from four cargo hooks (30).
The gas envelope was expected to
have an operating life of about 10
years with only minor maintenance.
23
10. Skyhook International Improved Hybrid Lift Air Vehicle
patent (Canada, 2009)
WIPO International Publication Number WO 2009/152604 A1;
“Improved Hybrid Lift Air Vehicle”; filed 21 May 2009; published 23
December 2009; inventors: Peter Jess & Ken Laubsch; applicant:
Sky-Hook HLV International Inc., Alberta, Canada; available here:
https://patentimages.storage.googleapis.com/48/ac/66/c0375cae5e7d
b2/WO2009152604A1.pdf
Abstract: “A hybrid lift air vehicle for carrying and transporting a load,
comprising an envelope (2) having a generally ellipsoidal shape
adapted to receive a volume of lighter-than-air gas, at least two
variable thrust vertical thrusters (28) in secure engagement with the
envelope and at least two variable thrust lateral thrusters (30) in
secure engagement with the envelope, means for temporarily
securely engaging the load (12) to the envelope wherein the volume
of lighter-than-air gas has a buoyancy that offsets at least 25% of the
weight of the air vehicle when unloaded, wherein the thrust from the
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at least two vertical thrusters may be varied to raise and lower the air
vehicle and the load when engaged, and wherein the thrust from the
at least two lateral thrusters may be varied to maneuver and transport
the raised air vehicle and the load when engaged.”
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11. Boeing SkyHook JHL-40 (USA / Canada, 2008 – 2010)
The SkyHook JLH-40 (JHL = “Jess Heavy Lifter”) is the commercial
incarnation of the patented heavy lift helistat designed by Peter Jess
and assigned to the Canadian firm SkyHook International, as
described in WIPO International Publication Number WO
2009/152604 Al. In July 2008, Boeing announced that it would team
with SkyHook International to build the SkyHook JHL-40.
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For the SkyHook application, the helium-filled gas envelope makes
the empty aircraft neutrally buoyant. The rotor system will generate
the lift needed to carry heavy loads. Lateral thrusters will provide
cruise propulsion and precise positioning during load transfers.
The SkyHook JHL-40 was 302 feet (92 m) long, slightly shorter than
the 1980s-vintage Piasecki PA-97-34J. The SkyHook was designed
to carry an external sling load of 40 tons (80,000 lb; 36,287 kg) at a
speed of 70 knots over a range of 230 miles (370 km) without
refueling. Without cargo, the SkyHook was expected to have a ferry
range of 800 miles (1,287 km).
Load exchange was accomplished with the SkyHook hovering
precisely over its destination with the coordinated rotor system
managing the increase in lift needed during load pickup and the
decrease in lift needed during load delivery. No exchange of ballast
was needed during a load exchange.
Source: Boeing, SkyHook International
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Source: Boeing, SkyHook International
Source: Boeing, SkyHook International
The business case for a SkyHook JHL-40 operating in the Canadian
high-North was based on the avoided cost and environmental
benefits of not building roads or rails for ground transportation into
these sensitive Arctic regions.
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The JHL-40 was to be certified by Transport Canada and the U.S.
Federal Aviation Administration, with the first aircraft expected to fly in
the 2012 – 2014 time frame. However, the development program was
cancelled in 2010 before the detailed design phase was completed.
Since the demise of the SkyHook program, there has not been
another heavy-lift helistat program.
12. For more information:
Piasecki
• Frank Piasecki, “Ultra-heavy vertical lift system: The Heli-Stat,”
Proceedings of the Interagency Workshop on Lighter than Air
Vehicles, NASA-CR-137800, pp. 465 - 476, Doc ID
19760007967, 1 January 1975:
https://ntrs.nasa.gov/citations/19760007967
• “PA-97: Multiple helicopter Heavy-Lift System,” Piasecki
Aircraft: https://piasecki.com/wp-content/uploads/2018/12/PA-
97.pdf
• “Heli-Stat Fact Sheet,” Department of Agriculture, Forest
Service, circa 1980: https://foresthistory.org/wp-
content/uploads/2011/04/Heli-Stat_factsheet.pdf
• “Piasecki PA-97 ‘Heli-Stat’, 1975” (in Polish), Planes in Polish
Aviation:
http://www.samolotypolskie.pl/samoloty/14640/126/Piasecki-
PA-97-Heli-Stat2
• “Need to Reevaluate Helistat Program Objectives and
Progress,” Report MASAD-81-31, General Accounting Office, 2
June 1981: https://www.gao.gov/assets/140/133372.pdf
• “ASN Wikibase Occurrence # 40405” (PA-97 crash 1 July
1986), Aviation Safety Network: https://aviation-
safety.net/wikibase/40405
• Eben Lehman, “From Aerologger to "Balloondoggle,” Forest
History Society, 29 April 2011: https://foresthistory.org/from-
aerologger-to-balloondoggle/
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Skyhook
• “Boeing Teams With Canada’s Skyhook For Heavy Lift Airship,”
Defense Daily, 7 October 2008:
https://www.defensedaily.com/boeing-teams-with-canadas-
skyhook-for-heavy-lift-airship-3/international/
• “JLH-40, Taking industry beyond the last mile,” SkyHook
International, Inc. & Boeing,
2008:http://www.jessco.ca/assets/boeing_skyhook_jhl-
40_backgrounder.pdf
• “Boeing Completes Major Design Milestone For SkyHook
Heavy Lift Vehicle,” Energy Daily, 29 July 2009:
https://www.energy-
daily.com/reports/Boeing_Completes_Major_Design_Milestone
_For_SkyHook_Heavy_Lift_Vehicle_999.html
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