U.S. patent application number 14/017471 was filed with the patent office on 2014-03-20 for dual-channel deicing system for a rotary wing aircraft.
This patent application is currently assigned to Sikorsky Aircraft Corporation. The applicant listed for this patent is Sikorsky Aircraft Corporation. Invention is credited to Timothy R. Budd, Antonio G. Daniele, Mark P. Eisenhauer, Robert J. Flemming, JR., Michael Houlihan.
Application Number | 20140076882 14/017471 |
Document ID | / |
Family ID | 37073965 |
Filed Date | 2014-03-20 |
United States Patent
Application |
20140076882 |
Kind Code |
A1 |
Houlihan; Michael ; et
al. |
March 20, 2014 |
DUAL-CHANNEL DEICING SYSTEM FOR A ROTARY WING AIRCRAFT
Abstract
A dual primary deicing system for a rotary-wing aircraft,
according to an exemplary aspect of the present disclosure
includes, among other things, an electrothermal heating element
system; and a controller in communication with said electrothermal
heating element, said controller communicating a heating cycle to
said electrothermal heating element system, said heating cycle
defining a first electric pulse train associated with a main rotor
blade assembly.
Inventors: |
Houlihan; Michael;
(Southbury, CT) ; Flemming, JR.; Robert J.;
(Trumbull, CT) ; Daniele; Antonio G.; (Manchester,
CT) ; Budd; Timothy R.; (Trumbull, CT) ;
Eisenhauer; Mark P.; (Milford, CT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Sikorsky Aircraft Corporation |
Stratford |
CT |
US |
|
|
Assignee: |
Sikorsky Aircraft
Corporation
Stratford
CT
|
Family ID: |
37073965 |
Appl. No.: |
14/017471 |
Filed: |
September 4, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11101269 |
Apr 6, 2005 |
8550402 |
|
|
14017471 |
|
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Current U.S.
Class: |
219/486 ;
219/490; 219/492; 244/134D |
Current CPC
Class: |
H05B 1/0236 20130101;
B64C 27/04 20130101; B64D 15/12 20130101; B64D 15/14 20130101; B64D
15/22 20130101 |
Class at
Publication: |
219/486 ;
244/134.D; 219/490; 219/492 |
International
Class: |
B64D 15/12 20060101
B64D015/12; H05B 1/02 20060101 H05B001/02 |
Claims
1. A dual primary deicing system for a rotary-wing aircraft
comprising: an electrothermal heating element system; and a
controller in communication with said electrothermal heating
element, said controller communicating a heating cycle to said
electrothermal heating element system, said heating cycle defining
a first electric pulse train associated with a main rotor blade
assembly.
2. The dual primary deicing system as recited in claim 1, wherein
said electrothermal heating element system includes a first
electrothermal heating element, a second electrothermal heating
element, a third electrothermal heating element, and a fourth
electrothermal heating element for each main rotor blade of the
main rotor blade assembly.
3. The dual primary deicing system as recited in claim 1, wherein
said heating cycle defines a second electric pulse train subsequent
to said first electric pulse train.
4. The dual primary deicing system as recited in claim 3, wherein
said first pulse train communicates with a first main rotor blade
and a second main rotor blade of said main rotor blade assembly,
and said second pulse train communicates with a third main rotor
blade and a fourth main rotor blade of said main rotor blade
assembly.
5. The dual primary deicing system as recited in claim 4, wherein
said first pulse train and said second pulse train are sequentially
communicated as said heating cycle.
6. The dual primary deicing system as recited in claim 1, wherein
said controller defines an off-time between heating cycles, and an
element on-time within said first pulse train.
7. The dual primary deicing system as recited in claim 6, further
comprising an ice rate probe in communication with said controller,
said off-time defined in response to said ice rate probe.
8. The dual primary deicing system as recited in claim 6, further
comprising an air data computer in communication with said
controller said element on-time determined in response to an
outside air temperature determined by an air data computer.
9. The dual primary deicing system as recited in claim 8, further
comprising a second controller in communication with a second ice
rate probe and said controller in communication with said
electrothermal heating element in response to failure of said first
controller.
10. The dual primary deicing system as recited in claim 9, wherein
the air data computer is a first air data computer, and further
comprising a second air data computer in communication with said
second controller, said second controller in communication with
said electrothermal heating element in response to failure of said
first air data computer.
11. The dual primary deicing system as recited in claim 1, wherein
said electrothermal heating element system comprises a first
electrothermal heating element, a second electrothermal heating
element, and a third electrothermal heating element, said third
electrothermal heating element is operated prior to said first
electrothermal heating element, said first electrothermal heating
element is operated prior to said second electrothermal heating
element in response to the heating cycle defined by the first
electric pulse train.
12. A method of deicing a rotary wing aircraft comprising the steps
of: (1) communicating a heating cycle to an electrothermal heating
element system, the heating cycle defining a first electric pulse
train associated with a first set of main rotor blades; and (2)
repeating the heating cycle after an off-time.
13. A method as recited in claim 12, further comprising the step
of: determining an element on-time for the first pulse train, the
heater element on-time being a linear function related to outside
air temperature (OAT).
14. A method as recited in claim 13, further comprising the step
of: determining the element on-time with an on-time value of 19
seconds at an OAT=-30 degrees C. and a value of 1 second at
temperatures between 0 degrees C. and +5 degrees C.
15. A method as recited in claim 14, further comprising the step
of: determining the off-time of said step (2) in accordance with a
non-linear function of liquid water content (LWC).
16. A method as recited in claim 12, further comprising the step
of: setting the element off-time equal to 60 seconds/LWC.
17. A method as recited in claim 12, further comprising the step
of: activating a multiple of electrothermal heating elements of the
electrothermal heating element system in a sequential order, the
multiple of electrothermal heating elements including a first
electrothermal heating element located along a leading edge of the
main rotor blade; a second electrothermal heating element located
aft of the first electrothermal heating element along an upper
surface of the main rotor blade; a third electrothermal heating
element located aft of the first electrothermal heating element
along a lower surface of the main rotor blade; and a fourth
electrothermal heating element located aft of the third
electrothermal heating element along the lower surface of the main
rotor blade, the sequential order being the third electrothermal
heating element, the first electrothermal heating element; the
second electrothermal heating element; then the fourth
electrothermal heating element.
18. A method as recited in claim 12, wherein said step 1) further
comprises the step of: communicating a second electric pulse train
subsequent to the first electric pulse train, the first electric
pulse train associated with the first set of main rotor blades and
the second electric pulse train associated with a second set of
main rotor blades.
19. A method as recited in claim 12, further comprising the step
of: redundantly communicating a heating cycle from a second
subsystem of a dual primary deicing system to the electrothermal
heating element system simultaneous with the heating cycle
communicated from a first subsystem of the dual primary deicing
system.
20. A method as recited in claim 19, further comprising the step
of: alternatively designating either the first subsystem or the
second subsystem of the dual primary deicing system as the primary
subsystem.
21. A method as recited in claim 20, further comprising the step
of: alternatively designating either the first subsystem or the
second subsystem of the dual primary deicing system as the primary
subsystem at each initiation of the dual primary deicing system.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional of U.S. patent application
Ser. No. 11/101,269, which was filed on 6 Apr. 2005 and is
incorporated herein by reference.
BACKGROUND
[0002] The present invention relates to an aircraft deicing system,
and more particularly to a dual primary deicing system for a rotor
system of a rotary-wing aircraft.
[0003] Rotary-wing aircraft may encounter atmospheric conditions
that cause the formation of ice on rotor blades and other surfaces
of the aircraft. Accumulated ice, if not removed, can add weight to
the aircraft and may alter the airfoil configuration causing
undesirable flying characteristics.
[0004] One approach to ice management that has been used is thermal
deicing. In thermal deicing, the leading edge portions of the rotor
blades are heated to loosen accumulated ice. The loosened ice is
then removed from the structural members by centrifugal forces and
the airstream passing over the leading edge.
[0005] In one form of thermal deicing, heating is accomplished by
electrothermal heating elements over or within the leading edges of
the airfoils. Electrical energy for the electrothermal heating
elements is derived from a generating source driven by one or more
of the aircraft engines or transmissions. The electrical energy is
intermittently supplied to provide heat sufficient to loosen
accumulating ice.
[0006] Rotary wing aircraft rotor blades are particularly
susceptible to icing and provide numerous challenges for
electrothermal deicing systems. One difficulty relates to the
refreezing of ice, which is melted with a leading edge
electrothermal element as the rotor system is constantly in
motion.
[0007] FAA Regulations, including 14 CFR 29.1309, and SAE ARP4761
delineate increased flight safety and redundancy requirements for
rotary-wing aircraft flying under icing conditions. Various
functionally acceptable rotary wing deicing systems are currently
in use, however, none provide the capabilities and redundancy
necessary to meet the expanded FAA regulations. Deicing systems
that meet these regulations provides a competitive position over
currently available rotary-wing ice protection systems.
[0008] Accordingly, it is desirable to provide an effective,
reliable, and redundant rotary wing deicing system which meets FAA
Regulations.
SUMMARY
[0009] A deicing system according to the present invention includes
a dual primary rotor deice system. Each major function of the
system of the dual deice system includes redundant components. Each
half of the dual system generally includes a controller, an air
data computer, slip ring channels, power distributor components, an
ice rate controller, and an ice rate probe. The controller
communicates with a junction box which communicates the electrical
energy to drive an electrothermal heating element system for the
main rotor system and an antitorque rotor system. Each component of
each of two subsystems of the dual deicing system can take over the
function of a failed component in the other half of the dual
deicing system.
[0010] The main rotor electrothermal heating element system
includes a number of electrothermal heating elements on each rotor
blade. The first electrothermal heating element of a spanwise rotor
blade deice system is located along the leading edge of the main
rotor blade along a stagnation line. The second electrothermal
heating element is located aft of the first electrothermal heating
element along the upper surface of the main rotor blade. The third
electrothermal heating element is located aft of the first
electrothermal heating element along a lower surface of the main
rotor blade. The fourth and succeeding electrothermal heating
elements are located aft of the third electrothermal heating
element along the lower surface of the main rotor blade. The first
electrothermal heating element of a chordwise rotor blade deice
system is located near the tip of the rotor blade and additional
elements are located inboard of this heating element. Those skilled
in the art know that combinations of spanwise and chordwise heaters
are practical.
[0011] The controller communicating a heating cycle to an
electrothermal heating element system such that the electrical
energy provided by the junction box follows the heating cycle. The
heating cycle defines a first electric pulse train and additional
electric pulse train subsequent to the first electric pulse train.
The first electric pulse train may be associated with a first set
of main rotor blades such as blades 1 and 3 of a four-bladed main
rotor system, while the second electric pulse train is associated
with a second set of main rotor blades such as blades 2 and 4 of a
four-bladed main rotor system. A tail rotor blade distributor is
typically not required as power is applied to each of the tail
rotor blades simultaneously.
[0012] Each electric pulse train of a four-bladed,
four-heating-element main rotor sequentially provides power to the
heating elements in the designated blade set. The sequential order
being the third electrothermal heating element, the first
electrothermal heating element, the second electrothermal heating
element, then the fourth electrothermal heating element. Such
sequence efficiently minimizes the likelihood of the melted ice
refreezing as it flows along the blade chord. The dual deicing
system controller is trained to bypass a failed heating element,
retaining the function of the remaining heater elements.
[0013] Each electric pulse train is defined by an element on-time,
a null time between the element on-time for this element and the
next element, and an off-time between repetition of the heating of
this element. The element on-time is a function of outside air
temperature (OAT). The off-time is a function of liquid water
content (LWC). The tail rotor heating cycle is a more
straightforward version of the main rotor heating cycle as each of
the tail rotor blade heater elements are activated simultaneously
and there is only a single heating element on each tail rotor
blade.
DESCRIPTION OF THE DRAWINGS
[0014] The various features and advantages of this invention will
become apparent to those skilled in the art from the following
detailed description of the currently preferred embodiment. The
drawings that accompany the detailed description can be briefly
described as follows:
[0015] FIG. 1 is a general perspective view an exemplary rotary
wing aircraft embodiment for use with the present invention;
[0016] FIG. 2A is a plan view of a rotor blade for use with the
present invention;
[0017] FIG. 2B is a plan view of a rotor blade with a spanwise
zoned deicing system;
[0018] FIG. 3 is a sectional view of the rotor blade taken along
line 2-2 of FIG. 2;
[0019] FIG. 4 is a perspective view of a rotor blade illustrating a
stagnation line;
[0020] FIG. 5 is a schematic block diagram of a deice system;
[0021] FIG. 6 is a graphical representation of one cycle in a pulse
train for a main rotor blade as generated by the deice system of
FIG. 5;
[0022] FIG. 7 is a graphical representation of one cycle in a pulse
train for a tail rotor blade as generated by the deice system of
FIG. 5; and
[0023] FIG. 8 is a graphical representation of one cycle in a pulse
train for a main rotor blade as generated by the deice system
illustrating an increase in the voltage level throughout the
cycle.
DETAILED DESCRIPTION
[0024] FIG. 1 schematically illustrates a rotary-wing aircraft 100
having a main rotor system 102 with rotor blade heater elements 30.
The aircraft 100 includes an airframe 104 having an extending tail
106 on which mounts an antitorque tail rotor system 108. The main
rotor assembly 102 is driven through a transmission (illustrated
schematically at T) by one or more engines E. Although a particular
helicopter configuration is illustrated in the disclosed
embodiment, other machines such as turbo-props, tilt-rotor, and
tilt-wing aircraft will also benefit from the present
invention.
[0025] FIG. 2 schematically illustrates an exemplary main rotor
blade assembly 10 mounted to a rotor hub assembly H (illustrated
schematically) of the main rotor assembly 102 for rotation about an
axis of rotation A. The main rotor blade assembly 10 includes an
inboard section 12, an intermediate section 14, and an outboard
section 16. The inboard, intermediate, and outboard sections 12,
14, 16 define the span of the main rotor blade 10. The blade
sections 12, 14, 16 define a blade radius R between the axis of
rotation A and a blade tip 18.
[0026] A plurality of main rotor blade assemblies 10 project
substantially radially outward from the hub assembly H and are
supported therefrom in one of numerous attachments. Any number of
blades 10 may be used with the main rotor system 102. The main
rotor blade 10 has a leading edge 20 and a trailing edge 22, which
define the chord C of the main rotor blade 10. Adjustable trim tabs
24 extend rearwardly from the trailing edge 22 or may be integral
to the trailing edge 22. A pitching axis P is near the center of
mass of the rotor blade in the chordwise direction and is also the
axis about which blade 10 twist occurs. The airfoil surface of the
rotor blade 10 is typically twisted linearly along the blade span
to improve aerodynamic efficiency.
[0027] Referring to FIG. 3, upper and lower skins 26, 28 define the
upper and lower aerodynamic surfaces of the main rotor blade 10. It
should be understood that relative positional terms such as
"forward," "aft," "upper," "lower," "above," "below," and the like
are with reference to the normal operational attitude of the
vehicle and should not be considered otherwise limiting. The skins
26, 28 are preferably formed from several plies of composite
material such as woven fiberglass material embedded in a suitable
resin matrix. An electrothermal heating element system 30 having a
multiple of electrothermal heating elements 32 is located along the
leading edge 20 of each rotor blade 10. During flight, airflow
impinges the leading edge 20 and a continuum of stagnation points
develop, forming a stagnation line or axis (illustrated
schematically in FIG. 4).
[0028] The electrothermal heating element system 30 preferably
includes four or more spanwise electrothermal heating elements
32-1, 32-2, 32-3 and 32-4 (FIG. 2) which are distributed chordwise,
or four or more chordwise electrothermal heating elements which are
distributed spanwise. In a spanwise deice system with four heating
elements per main rotor blade 10, the first electrothermal heating
element 32-1 is located along the leading edge 20 of the main rotor
blade 10 and preferably covering the stagnation line (FIG. 4). The
second electrothermal heating element 32-2 is located aft of the
first electrothermal heating element 32-1 along the upper surface
26 of the main rotor blade 10. The third electrothermal heating
element 32-3 is located aft of the first electrothermal heating
element 32-1 along a lower surface 28 of the main rotor blade 10.
The fourth electrothermal heating element 32-4 is located aft of
the third electrothermal heating element 32-3 along the lower
surface 28 of the main rotor blade 10. Alternatively or in
addition, the spanwise electrothermal heating elements 32-1, 32-2,
32-3 and 32-4 are separated into a multitude of spanwise zones such
as an inboard zone I and an outboard zone O (illustrated
schematically in FIG. 2B) to provide a composite spanwise and
chordwise electrothermal heating element system 30'.
[0029] The chordwise heater element coverage is preferably from
8.6% of the upper surface to 15% of the lower surface for the
SC2110 airfoil and from 8% of the upper surface 15% of the lower
surface for the SSC-A09 airfoil. It should be understood that other
airfoils will benefit from other chordwise coverage areas but
Applicant has determined that from approximately these values to
10% of the upper surface to approximately these values to 17% of
the lower surface is relatively effective for most airfoils.
Spanwise the heating elements 32-1, 32-2, 32-3, 32-4 preferably
cover from a 20% blade radius position to a 92% blade radius
position of said main rotor blade span, although other values of
spanwise coverage may be effective for other main rotor blades.
[0030] Each tail rotor blade 34 of the antitorque tail rotor system
108 preferably includes a single electrothermal heating element 36
which provides chordwise coverage from approximately 12% of the
upper surface to 12% of the lower surface. Spanwise, the heating
elements 36 preferably cover from a 25% blade radius position to a
92% blade radius position of the tail rotor blade span (FIG.
5).
[0031] Referring to FIG. 5, a deicing system 38 according to the
present invention is illustrated. The deicing system 38 generally
includes a number 1 deice subsubsystem 40 and a number 2 deice
subsystem 42. Each subsubsystem 40, 42 includes a controller 44a,
44b such that the subsystems 40, 42 are redundant. The controllers
44a, 44b communicate with each other over a communication bus 45
such that each subsystem 40, 42 is continually interrogating each
other to assure proper operation of each system. Should one
subsubsystem 40, 42 or one component of the subsubsystem 40, 42
fail, the other subsystem 42, 40 will provide uninterrupted deicing
system 38 operation. Preferably, each subsubsystem 40, 42
communicates with the electrothermal heating element system 30 such
that operation of the deicing system 38 is uninterrupted
irrespective of a failure. Furthermore, the subsubsystem 40, 42 are
alternatively designated as a primary or secondary system such that
each subsubsystem 40, 42 is regularly exercised. The subsubsystem
40, 42 may be alternatively designated as the primary or secondary
system each time the deicing system 38 is initiated, each time the
aircraft 100 is operated, or at some other interval. As the
subsystems 40, 42 are identical, only subsubsystem 40 will be
described in detail with the understanding that the description
applies equally to subsystem 42.
[0032] The subsystem 40 generally includes the controller 44a, an
air data computer 46a, an ice rate controller 48a and an ice rate
probe 50a. The controller 44a communicates with a 200VAC junction
box 52 which communicates the electrical energy such as from the
Engine Driven Generator E.sub.gen to drive the electrothermal
heating element system 30 for the main rotor blade 10 and each tail
rotor blade 34 through a main rotor slip ring 54 and tail rotor
slip ring 56.
[0033] The air data computer 46a communicates flight and
environment information to the controller 44a. Information such as
airspeed outside air temperature (OAT) as well as other conditions
are preferably provided. The air data computer 46a may be a
dedicated controller for the deice system or may be information
provided by other aircraft data systems.
[0034] The ice rate probe 50a operates in accordance with a
reference signal provided by the ice rate controller 48a which
communicates with the controller 44a. As ice accumulates on the
probe, the detection frequency will change such that the controller
44a provides the aircrew with a visual display of icing conditions
on a Multi-function Display 58 (MFD) or the like within the
aircraft cockpit. The MFD 58 preferably provides information
regarding the status control and communication with the blade deice
system 38, however, other communication and control systems will
also be usable with the present invention.
[0035] The controller 44a communicating a heating cycle 60 (FIG. 6)
to the electrothermal heating element system 30 such that the
electrical energy provided by the junction box 52 follows the
heating cycle. That is, the junction box 52 distributes power to
the electrothermal heating element system 30 in accordance with the
heating cycle 60.
[0036] Referring to FIG. 6, the heating cycle 60 preferably defines
a first electric pulse train 62 and a second electric pulse train
64 subsequent to the first electric pulse train 62. The first
electric pulse train 62 is preferably associated with a first set
of main rotor blades such as blades 1 and 3 of a four-bladed main
rotor system while the second electric pulse train is associated
with a second set of main rotor blades such as blades 2 and 4 of a
four-bladed main rotor system. It should be understood that the
number of pulse trains and the number of blades within each set may
differ but will likewise be usable with the present invention.
[0037] The controller 44a sends command signals through the main
rotor slip ring 54 to the redundant components of the hub
distributor 66 (FIG. 5), which responds to controller signals by
switching power in sequence to the main rotor blade heating
elements 32-1, 32-2, 32-3, 32-4. The tail rotor blade power is
switched directly by the controller 44a and sent through the tail
rotor slip rings 54 to the tail rotor blades. A tail rotor blade
distributor is not required since the power is applied to each of
the tail rotor blades simultaneously (FIG. 7).
[0038] Each electric pulse train 62, 64 sequentially provides power
to the heating elements 32-1, 32-2, 32-3, 32-4 in the designated
blade set. The preferred sequential order being the third
electrothermal heating element 32-3, the first electrothermal
heating element 32-1, the second electrothermal heating element
32-2, then the fourth electrothermal heating element 32-4. Such
sequence efficiently minimizes the likelihood of the melted ice
refreezing as it flows along the blade chord by airflow.
[0039] Each electric pulse train 62, 64 is defined by a element
on-time, a null time between the element on-time for this element
and the next element, and an off-time between heating on-times
between successive application of power to the first heating
element 32-3. The null time is preferably a relatively short fixed
value such as 200 milliseconds which accounts for electrical
switching between heating elements 32-1, 32-2, 32-3, 32-4.
[0040] The element on-time is a linear function of outside air
temperature (OAT) as determined by the air data computer 46a.
Preferably, the element on-time corresponds to a linear function
having an on time value of 19 seconds at an OAT=-30 degrees C. and
a value of 1 second at temperatures between 0 degrees C. and +5
degrees C.
[0041] The off-time is the time between successive application of
power to the first heating element 32-3. The sum of the on-time and
the off-time defines a heating cycle 60. That is, activation of
each of the heating elements for each of the blades and the time
that heat is not applied to the blades defines one heating cycle.
The off-time is preferably a non-linear function of liquid water
content (LWC) in which the off-time is equal to 60 seconds/LWC.
[0042] Preferably, a voltage signal level is increased during the
heating cycle 60 in a step-function like manner (FIG. 8) to provide
a signal for activating each heating elements 32-1, 32-2, 32-3,
32-4 in the heating cycle 60. The increase in the voltage is the
signal sent from the controller 44a and not the power to the
heating element 32-1, 32-2, 32-3, 32-4. Preferably, there is one
volt between heat application for each element, however, other
voltage differences may also be used. Each of the eight signal
voltage pulses is shown in FIG. 8.
[0043] If an element had failed, only seven signal voltage pulses
would be illustrated in FIG. 8 and there would be a two volt shift
between the application of power from one non-failed heating
element 32-1, 32-2, 32-3, 32-4 to the application of the next
non-failed heating element 32-1, 32-2, 32-3, 32-4. That is, the
controller 44a skips the failed heating element. To determine a
failed heater element, the controller 44a preferably provides a
multiple of checks during transmission of the operation of the
voltage signal level (FIG. 8) such as comparisons with a system
clock, current in each power lead, confirmation that sent signals
are received (the sent signal is repeated back to the controller
44a), etc. For example, if a heating element 32-1, 32-2, 32-3, 32-4
is above or below a predetermined target level by more than a
predetermined amount, the heating element 32-1, 32-2, 32-3, 32-4
will be classified as failed. The controller 44a will then no
longer set the voltage signal for the failed heating element at the
level associated with that heater zone in the voltage signal level
(FIG. 8), so the next zone in the sequence will be energized
earlier than normal, in accordance with that signal voltage.
[0044] The tail rotor heating cycle (FIG. 7) is a more
straightforward version of the main rotor heating cycle as each of
the tail rotor blade heaters are activated simultaneously and there
is only a single heating element on each tail rotor blade.
[0045] In operation, the blade deice system 38 utilizes the MFD 58
in conjunction with the controllers 44a, 44b to control and test
the system. The MFD allows the flight crew to select automatic
operation (AUTO) in response to the system determination that at
least 0.015 of an inch ice has been detected or manual operation
(TRACE, LIGHT, MODERATE, HEAVY) when the flight crew believes that
the automatic mode has failed to provide effective deicing of the
main rotor blades 10.
[0046] The MFD 58 preferably displays the icing severity as: TRACE,
LIGHT, MODERATE and HEAVY. It should be understood that the icing
severity levels TRACE; LIGHT; MODERATE; and HEAVY are predetermined
values for each aircraft type. An ICE DETECTED caution is displayed
on the MFD 58 when the electrothermal heating element system 30 is
off but ice has been detected. The flight crew is thereby informed
of the requirement to turn on the blade deice system 38.
[0047] When ICE DETECTED is displayed on the MFD, the flight crew
must ensure that at least the following systems are ON prior to the
warning being extinguished: No. 1 Eng Anti-Ice, No. 2 Eng Anti-Ice,
Pitot Tube Heat (normally automatic), Blade Deice, Pilot Windshield
Heat, and Copilot Windshield Heat.
[0048] The MFD preferably permits selection between automatic or
manual control of blade heating element off time. In AUTO mode, the
controllers 44a, 44b provide the signals that result in off-time
variations proportional to the ice rate as described above. In a
manual mode (TRACE; LIGHT; MODERATE; or HEAVY), the off-times are
fixed.
[0049] When there is an ice rate subsystem malfunction, a FAIL
indication on the MFD will appear advising that the deice system is
using a default LWC and advising that operation of the blade deice
system in one of the manual modes (TRACE; LIGHT; MODERATE; or
HEAVY) made be required.
[0050] MANUAL mode is also preferably entered when the MFD has no
indicated malfunction, but any of these three conditions has
occurred:
[0051] (1) pilot has determined by his judgment of ice severity
that ice rate system is inaccurate,
[0052] (2) torque required has increased to an unacceptable level,
or
[0053] (3) helicopter vibration has increased to an unacceptable
level.
[0054] It should be understood that relative positional terms such
as "forward," "aft," "upper," "lower," "above," "below," and the
like are with reference to the normal operational attitude of the
vehicle and should not be considered otherwise limiting.
[0055] Although particular step sequences are shown, described, and
claimed, it should be understood that steps may be performed in any
order, separated or combined unless otherwise indicated and will
still benefit from the present invention.
[0056] The foregoing description is exemplary rather than defined
by the limitations within. Many modifications and variations of the
present invention are possible in light of the above teachings. The
preferred embodiments of this invention have been disclosed,
however, one of ordinary skill in the art would recognize that
certain modifications would come within the scope of this
invention. It is, therefore, to be understood that within the scope
of the appended claims, the invention may be practiced otherwise
than as specifically described. For that reason the following
claims should be studied to determine the true scope and content of
this invention.
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