By David M. North
January 25, 2004
HERITAGE PAYOFF
Following the publication of the Sikorsky S-92 pilot evaluation in
the Sept. 29, 2003, issue of Aviation Week & Space Technology,
I received a letter from USAF Maj. Regan Patrick, a HH-60G Pave
Hawk pilot in a combat search-and-rescue unit at Nellis AFB, Nev.
Patrick chided me, noting that because I am not a rated helicopter
pilot, I had omitted some specific performance parameters that
would have been of interest to helicopter pilots in better
evaluating the S-92. I discussed these points with him, and asked
what queries should have been posed during the flight. He, and
other pilots of the 66th Rescue Sqdn., sent a substantial list of
questions for me to ask while flying the AgustaWestland EH-101. I
have attempted to incorporate the answers into this pilot
evaluation of the Merlin Mk. 3.
The team of AgustaWestland, Bell Helicopter and Lockheed Martin are
counting on the more than 45,000 flight hours and proven
operational record of its EH-101 to help them in their quest to
provide the next helicopter for presidential service.
The team is also banking on the inherent strength of the
three-engine helicopter's design and performance, along with its
U.S. partners' experience, to defray the home-court advantage held
by Sikorsky Aircraft. That U.S. manufacturer has a strong contender
for the presidential mission in its S-92, and has supplied
helicopters for the executive travel role since the 1950s
(AW&ST Sept. 29, 2003, p. 44).
Recently, the joint team strengthened its case by choosing General
Electric's CT-6 engine to power its US101 candidate, rather than
the alternate Turbomeca engine utilized by some countries' EH-101s.
AgustaWestland and Lockheed Martin officials also are quick to
point out partner Bell Helicopter's heritage, and that the
Texas-based company would be chief builder of the US101.
The EH-101 had its inception in 1984 with a joint development
contract between Italy and Great Britain. There were nine
preproduction helicopters built starting in 1992, and 10,000 hr.
were devoted to development flying. This included two EH-101s
delivered to Bristow Helicopters which were flown by the support
company an average of 4 hr. a day on a six-day-week basis for four
years. That test phase ended in 2001, and according to Royal Air
Force Wing Cdr. David Stubbs, AgustaWestland discovered that the
tires, and bearings in the tail rotor, were wearing out faster than
expected. Both those deficiencies were corrected, according to
Stubbs.
The Royal Navy began receiving the first of its 44 Merlin Mk. 1
helicopters in 1998 for maritime patrol, anti-submarine warfare,
troop transport and vertical replenishment missions. At about the
same time, the Tokyo Metropolitan Police started to operate its
EH-101s. The Marina Militaire Italiana received the first of its
initially planned 20 EH-101s in 2000. The Italian service uses the
helicopter for special operations and various traditional
roles.
The Royal Air Force has been using Merlin Mk. 3s since 2000, and
has received its 22 helicopters to be used in the support role.
Early in 2003, the RAF sent four Merlins to fly anti-surface
missions in support of the U.S. Navy in Operation Iraqi Freedom.
The RAF had one Merlin in the air at all times, and the four
Merlins accumulated 800 hr. total flying and 200 hr. in a 14-day
period, Stubbs said. Only one sortie was scrubbed, and that was for
maintenance reasons. Another two of the Mk. 3s from the RAF
squadron have been operating in Bosnia since April of last year.
The average availability of Mk. 3s has been 90.2%, with a high of
96.7% and a low of 84.6%. The lower-than-expected rates were due to
the long supply chain for parts from England, exacerbated by the
fact that there were only two supply flights a week.
I had the opportunity to fly an EH-101 in the RAF Mk. 3
configuration from the general aviation Stafford Airport south of
Washington in late November. Two of the Merlins had been shipped to
the U.S. to support Naval Air Systems command test-and-evaluation
flying planned for this month. The flight was in ZJ 121, the fifth
production Merlin Mk. 3, which had returned from operations in
Bosnia late last year. The flight was with the leader of 28th
Sqdn., Al Dale, who had recently returned from Bosnia. The flight's
crew leader was Pete Appleby; second crewman was Shaun Chanc.
Dale gave me a walk around briefing of the Merlin Mk. 3 prior to
the flight. The EH-101 is at least 6,000 lb. heavier than the S-92
in the RAF version, although both helicopters would increase in
size for the presidential mission, the US101 version by some 2,200
lb.
The Mk. 3 is equipped with a comprehensive integrated defensive
system, including Northrop Grumman AN/AAQ-24 Nemesis Dircm,
Raytheon laser detection, BAE Systems AN/ALE-47 chaff/flare
dispensers and Sky Guardian 2000 RWR. The flight data and cockpit
voice recorder are housed in a round container near the tail, which
detaches if the helicopter goes into the water.
Unlike the S-92, where the fuel is contained in two large sponsons,
fuel in the EH-101 is located below the cabin in self-sealing
tanks. Program officials were quick to point out that during
development testing and operational flying, the operation and
integrity of the fuel system has not been a problem, and is as safe
as other means of fuel storage. The EH-101 has the internal
plumbing required for an inflight refueling system, but a probe has
not been installed on RAF helicopters. Sikorsky officials also
believe their S-92 benefited from its later certification date and
newer technology, granting longer mean time between failures and
time between overall for some of its components. AgustaWestland
officials counter that while initial U.S. certification came in
1994, full production EH-101 civil certification was granted in
1999 and differences between requirements have only changed
slightly. They also claim infinite component lives for many items,
and say that rotor main blades have a 10,000-hr. life.
The RAF helicopter was rigged for the utility role with side-facing
web seats in the interior. Walking up the rear ramp into the
helicopter, I noted the impressive cabin size. It is larger than
that of the S-92, befitting its overall larger size and higher
gross weight. While the cabin height is virtually the same in both
helicopters, the EH-101 cabin is 1.5 ft. wider and more than 3.3
ft. longer. The overall larger size requires the EH-101 to be
fitted with "low rider" wheels prior to being loaded on a Boeing
C-17. The tail has to be prefolded, but in the naval EH-101 an
electrical system is installed, and folding takes about 2 min.,
according to Lockheed Martin officials. The main rotor blades have
to be removed, but when they are refitted on the helicopter after
it's taken from the cargo aircraft, without rigging adjustments,
the first flight is to confirm operation, rather than a required
test flight. Time required for preparation for stowage or
reassembly is under the 5-hr. target, company officials say.
Dale took the right seat, I flew from the left. The auxiliary power
unit was operating so we had power to the cockpit. The RAF version
of the helicopter is equipped with an eight-Smith-cathode-ray tube
display for the instrument panel. Dale said the EH-101s destined
for the Danish air force this year would have six LCDs installed in
place of the CRTs. The Danish helicopter also will have current
TCAS and GPWS installed plus a second GPS--the same configuration
as on the presidential mission submission.
I found the system displays to be easy to read, and with a little
study, could understand how they operate. You could tell that
pilots supplied input to the engineers in the design process. The
primary flight displays also were very functional, and taken
overall in the flight, provided excellent situational awareness. A
moving map display will be added to RAF Merlins, but is standard
equipment on later versions of the EH-101. The cockpit is
night-vision-goggle capable, as is the cabin, with the activation
of one switch. Dale said the RAF uses the goggles for all night
flights.
We started the No. 1 engine first. The left engine is tied to the
auxiliary gearbox and does not directly turn the main rotors. The
middle, or No. 2 engine, once started, had the main rotor turning.
The No. 3 engine functions much like the No. 1. Dale said they have
demonstrated the ability to go from cold helicopter to takeoff in
90 sec. While he would activate this capability later, he said that
they often shut down the right engine in cruise to provide more
range or greater loiter time. Nominal range for the Mk. 3 is close
to 750 naut. mi. with internal fuel, but with the right engine off
during cruise, can be extended to near 1,000 naut. mi. Dale said
the engines have presented no problems during RAF operations,
including the center engine in hot and sandy conditions.
Maj. Alex Thomson, a Canadian Air Reserve pilot, has flown the
EH-101 Cormorant since October 1999 and confirmed Dale's statement
on the reliability of the EH-101 in operational service. He said
the Cormorant, equipped with General Electric turbine engines, has
had no difficulties. The GE engine is not fitted with Fadecs in the
Canadian version, but would be for the US101 presidential
helicopters.
Dale demonstrated a short takeoff roll from the general aviation
runway, with liftoff at approximately 40 kt. and we started our
cruise toward a grass field in a U.S. Army restricted area. The top
cruise speed of the Merlin Mk. 3 is 150 kt., so we cruised at 1,500
ft. at 140 kt., which was quite comfortable in relation to
vibration and noise. Top airframe speed of the EH-101 is 167 kt.
and best range speed is 130 kt. I was easily able to write on a
kneeboard at the cruise speed. AgustaWestland has addressed
vibration dampening in two ways. The EH-101's rotor is the same
diameter as the Sikorsky H-3 series, but an advanced blade design
with larger width near the tip delays the rapid rise of vibration
at high speed.
Vibration dampening is primarily the task of the Active Control of
Structural Response (ACRS) system. By the use of 10 sensors in the
cockpit and cabin, vibration measurements are processed and
canceling signals are computed and transmitted to hydraulic
actuators within four transmission support struts. The ACRS system
is designed to adapt to different flight regimes, and can operate
in a degraded mode, if necessary. At 138 kt. Dale turned the ACRS
system off, and the difference in vibration was noticeable; I was
unable to write on my kneepad.
In a somewhat different approach to multifunction displays I have
flown recently, speed and altitude were displayed on round dials;
rate of climb with a bar. The bottom display was used for
horizontal navigation while the screen to the right of the primary
could have been used for the radar or infrared system in the
helicopter. The RAF Merlin has a chin-mounted BAE Systems infrared
system. The two center displays are used for system and engine
monitoring. The EH-101 is equipped with a Health and Usage
Monitoring System (Hums). And, as with most current helicopters,
the EH-101 has a dedicated avionics cabinet with its own cooling
systems.
Dale demonstrated how the Mk. 3 would be used for either troop
extraction or insertion by flying into a relatively small grass
field surrounded by trees. A second RAF Merlin was flying overhead
to provide suppression fire, if required. This exercise underscored
the extent of Dale's vast pilot experience as we let down and
hovered in the small area. I also realized that visibility from the
left seat was excellent as I looked at the ground, surrounding area
and the helicopter flying overhead.
When the demonstration was completed, I took the controls and we
headed for the Potomac River. Engine limits for both maximum
continuous and a 2.5-min. power are shown as bugs on the torque
meter scale. A torque margin indicator showed whether we might be
engine or torque limited. Specific engine performance and predicted
power required for hover was displayed on the aircraft management
computer. Although it was somewhat alien to this fixed-wing pilot,
Dale quickly explained what the parameters and limits meant in
relation to the helicopter's performance. Maximum operational
altitude of the EH-101 is 15,000 ft.
The flight control system compensates for yaw in turns so the
EH-101 can be flown with feet off the pedals in flight. I found
bank control to be very positive and precise once I learned the
needed inputs. Pitch control was somewhat dampened, but again, the
nose went where it was placed.
As we approached the Potomac, Dale had me slow the Mk. 3 to 100 kt.
and engage the autopilot. With hands off, we decelerated to a hover
speed and descended to 60 ft. We further let down to 20 ft. and
with a hover display showing, we positioned the EH-101 over an
imaginary person in the water to allow a hoist operator to assay a
rescue. With my hands resting lightly on the stick and collective
at the hover, Dale said not to worry as the automatic functions on
the Merlin Mk. 3 have proven to be very reliable. This same
automatic leveling, deceleration and hover capability can be tied
to the autopilot's coupled VOR/ILS mode for landing
approaches.
DURING THE FLIGHT back to Stafford I asked Dale about the deicing
function of the helicopter. The EH-101 has a full electrical
system, providing anti-icing to the airframe, including engine
intakes and pitot tubes. Continuous deicing of tail rotor blades
and sequenced deicing of main rotor blades are also provided. At
present, the EH-101 is cleared for continuous operation in icing
conditions down to -8C, but the company is working to expand that
to -45C. Thomson, the Canadian pilot, said the system works very
well and that in eastern Canada's harsh winter conditions there
were times when the Cormorant was the only helicopter flying.
I continued to fly the Mk. 3, making an approach to the runway at
Stafford and touching down at near 20 kt. Dale said maximum speed
for a roll-on landing is near 40 kt. He then took the helicopter to
a grassy area near the runway and had me operate the rudder pedals
while he held on the collective and stick in the hover. Rotation in
the hover was quick and I realized that, at hover, the helicopter
was in a horizontal attitude. I then individually took control of
the stick and collective, while Dale operated the two other
controls. Following a hover at 20 ft. where we stayed almost
stationary, I landed the Merlin in the grass. Following this
exercise, I felt more comfortable as a helicopter pilot.
Dale then performed a takeoff and shut down the No. 3 engine on the
downwind to the Stafford runway. In the cockpit, you could not tell
the difference at 100 kt., and Dale indicated that plenty of power
margin was left, and there would be ample margin remaining if we
had been at maximum gross weight. Engine and transmission limits
with one engine out still make available more than 75% of the power
to the pilot.
The flight lasted for 1.2 hr. in which time four landings were
executed.
While the competition for the next presidential helicopter is more
imminent and a win would be very important for AgustaWestland, Bell
and Lockheed Martin, the combined team is also looking at other
potential programs. A candidate for a future combat
search-and-rescue helicopter for U.S. forces would be based on the
US101 aircraft and engine combination, along with the same rear
ramp configuration and dynamic systems. The avionics suite and
defensive electronics also could be similar to that proposed for
the presidential replacement helicopter.
A US101 version will be proposed to the U.S. Coast Guard, as well,
when the service reaches later phases in its "Deepwater" program
and is looking for increased range for the helicopter fleet.
Win or lose in their quest for the presidential helicopter buy, the
combined team is doing its best to promote the time in service and
operational successes of EH-101 as well as US101's U.S. roots and
connections. Whether the combined team was able to oust the
entrenched Sikorsky team and its S-92 contender should be known by
mid-2005.
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