Here at Goodrich,
we prescribe to the premise that not all rescue hoist and cargo
winches are created equal. We produce both the traditional level
wind and industry unique translating drum cable management systems.
At Goodrich, we believe the distinction between the technologies
is significant enough that we have internally categorized the translating
drum as Category One and the traditional level wind as Category
Two. Goodrich is the only manufacturer of the Category One Technology
in the world.
The reason for
the Category One & Two identity is simple. The mission capabilities
of the two design concepts are profoundly different and should be
taken into consideration when selecting a rescue hoist for your
helicopter. Specifically, the translating drum (Category One Technology)
allows for an unlimited fleet angle (the relative angle between
the helicopter and the load being hoisted).
High fleet angles
are a result of the environmental factors impacting a rescue. The
angles can be generated spontaneously from pitching decks, swift
water, high winds, obstacles, terrain, or a multitude of circumstances
out of the rescue crews control.
At Goodrich,
we believe it is critical that rescue hoist operators understand
the differences and recognize the limitations associated with the
Category One translating drum versus the Category Two level wind technologies.
These differences may very well save a life and at the very least
impact the probability of success of the mission. While both have
proven successful in general application, the selection of the technology
should be based on the application of the hoist envisioned by the
user.
The Category Two
level wind technology is applicable in the environment where usage
is minimal and high fleet angles are not anticipated. In comparison,
the Category One translating drum technology provides opportunities
to operate in high usage, high fleet angle environments with minimal
impact to the hoist, cable or overall reliability of the hoist.
Category
One Technology
(Manufactured exclusively by Goodrich)
The
Goodrich Category One rescue hoist is designed with a LeBus cable groove
that provides the most efficient, compact cable-wrapping technique.
A level wind screw and shoe allow the cable drum to translate while
rotating. Thus, the chance of a cable miswrap induced from side loading
is substantially reduced.
The translating drum allows direct transfer of side load into the
housing. Therefore, side loads from the cable do not have any effect
on the level wind or ball spline mechanisms. Combining this with large
diameter fairlead rollers dramatically increases hoist and cable life.
Other technological
considerations include the use of a traction drive that maintains
cable tension even with no load. Heat is dissipated through a wet
clutch eliminating cable wear associated with standard over drive
mechanisms and also allowing the cable to be lubricated extending
the life. Oil from the cable in turn is transferred to internal
metallic parts minimizing corrosion, especially when the hoist is
used in salt water environments.
Additionally, Goodrich Category One Technology also offers symmetrical
braking, which should be considered as a necessary feature because
it eliminates coasting. This design feature allows a hoist to rapidly
reverse direction for safe operation in unstable environmental conditions.
Symmetrical braking also allows easier control over cable slack
during fast water or high fleet angle rescues increasing rescuer
safety.
Category
Two Technology
(Standard Industry Offering)
The
Goodrich Category Two rescue hoist is designed with a follower, commonly
called a shoe that travels in the groove of the Yankee screw. This
follower provides the thrust force for translating the level wind
assembly. Most followers are crescent shaped with a triangular cross
section that is designed to wedge into the groove of the screw.
The resulting motion between the screw and follower is a sliding
action that produces a thrust force on the level wind mechanism.
At each end of the screw, a "turn-around" groove is provided
that joins both helices. The turn-around grooves allow the level
wind mechanism to reverse the direction of translation.
The pitch of the screw and pitch of the drum must be equal, or a
secondary gear reduction must be provided that allows the two pitches
to be synchronized. The "industry standard" for helicopter-mounted,
personnel rescue hoists is a three-sixteenths inch diameter cable
with a three-eighths inch screw pitch. A gear reduction of integral
number (in this case a two to one gear ratio) is used to slow down
the screw to maintain a synchronized position with the drum pitch.
The level wind mechanism and the storage drum work in unison to
produce an even layering of cable on the drum.
Conventional
level wind mechanisms must react to the horizontal load component
from a cable fleet angle. A 600 pound load with a 30 degree fleet
angle produces a thrust load of 300 pounds (600 * sin 30o = 300),
which must be reacted to by the conventional level wind mechanism.
In comparison, a maximum thrust load of eight pounds is required
to translate the Category One Goodrich drum with a 600 pound load regardless
of fleet angle.
Two
Choices One Answer
Goodrich
offers both technologies because it is our goal to provide our user
community with exactly what they need. If your hoisting requirements
involve minimal duty cycles and simple lifts of less than fifteen
degrees fleet angle, then the less expensive Category Two Technology
is right for you and investing in Category One Technology may not be
cost effective. If your hoisting requirements involve a significant
number of operations in adverse conditions and high reliability is
a priority, you should consider investing in the Category One Technology
for a variety of reasons.
Perhaps the
most important consideration is the unlimited rescue capability
that the Category One Technology offers the user. Regardless of conditions,
the lack of fleet angle restrictions offers you far more options
and capability than the Category Two Technology.
Category One systems also offer symmetrical braking on the cable, eliminating
additional payout upon reversal of cable direction giving the operators
greater control. Additionally both electrical and hydraulic rescue
hoists feature systems that eliminate the need for cool down periods
allowing unlimited operations.
In addition to capability, the Category one technology lends itself
to greater reliability over far more duty cycles that the Category
two technology can offer. In fact, our first recommended overhaul
for a Category one hoists is either 111 hoisting hours or ten years
(which ever comes first)
Regardless of
your rescue hoist demands, Goodrich is confident that we have a
cost effective solution for you.
