Military

The Need For Improved Helicopter Navigation Systems

 

CSC 1992

 

SUBJECT AREA Aviation

 

 

 

 

                        EXECUTIVE SUMMARY

 

Title:    The Need For Improved Helicopter Navigation Systems

 

 

Author:   Major C.W. D'Ambra, United States Marine Corps

 

 

Thesis:   The navigation equipment on board Marine Corps

helicopters, tasked to fly in support of MEU(SOC) missions,

Is inadequate to meet the demanding mission requirements.

The Marine Corps must move aggressively to procure advanced

navigation systems for its helicopters, seeking both short

and long-term solutions.

 

 

Discussion:   The Marine Expeditionary unit (Special

Operations Capable) (MEU[SOC]), forward deployed, is the most

responsive Marine Air-Ground Task Force (MAGTF) In the Marine

Corps.  Missions of the MEU(SOC) include Noncombatant

Evacuation Operations (NEO), clandestine recovery operations,

Tactical Recovery of Aircraft and Personnel (TRAP),

in-extremis hostage rescue, airfield seizures, and the

seizure of static Gas/Oil Platforms (GOPLATS).

 

            FMFPR 2-12 indicates that the most important capability

of the MEU is its ability to conduct quick reaction long-

range raids over-the-horizon during periods of darkness and

adverse weather conditions.  Unfortunately, the majority of

aircraft tasked to fly on these missions still rely on the

same type equipment that was installed on the Navy RH-53Ds

used in the Iranian Rescue-Mission twelve years earlier.  The

Holloway Report on that mission, referring to that navigation

equipment, indicates that the helicopters were "austerely

prepared.

 

            A review of recent history shows that the opportunities

to employ the MEU(SOC) are increasing, along with the risk,

but installed helicopter navigation systems are not keeping

pace.  The system currently offering the greatest potential

for improved navigation capabilities is the Global Positioning

System (GPS).  Although only available in limited quantities,

GPS receivers used during Operation Desert Shield/Desert

Storm received glowing reviews.  In addition to advanced

navigation systems being developed for the military, several

commercial low-cost GPS's are currently available which could

provide an interim solution.

 

            The Marine Corps cannot afford to needlessly jeopardize

the success of the demanding missions assigned to the

MEU(SOC) due to inadequate navigation equipment when the

technology exists to improve it today!

 

 

                       THE NEED FOR IMPROVED HELICOPTER

                              NAVIGATION SYSTEMS

 

                                    OUTLINE

 

 

THESIS STATEMENT.  The navigation equipment on board Marine

Corps helicopters, tasked to fly in support of MEU(SOC)

missions, is inadequate to meet the demanding mission

requirements.  The Marine Corps must move aggressively to

procure advanced navigation systems for its helicopters,

seeking both short and long-term solutions.

 

 

 I.         Marine Expeditionary Unit (Special Operations Capable)

            A.        Background

            B.        Missions and Requirements

 

 II.        Current Helicopter Navigation Systems

            A.        Low-frequency/Automatic Direction Finding Set (LF/ADF)

            B.        Tactical Air Navigation (TACAN) System

            C.        Long-range Navigation (LORAN) System

            D.        Omega Navigation System (ONS)

 

III.        Examples of Equipment Shortcomings

            A.        Beirut, Lebanon

            B.        Operation Eastern Exit

            C.        Operation Provide Comfort

 

IV.         Advanced Navigation Systems

            A.        Global Positioning System (GPS)

                  1.        System Overview

                  2.        TRIMPACK -- An Immediate Solution

                  3.        Civilian Options

            B.        Future Systems for the Military

                  1.        Position, Location, Reporting System (PLRS)

                  2.        Doppler Navigation System (APN-217)

                  3.        Omega Navigation System Upgrade W/GPS

                  4.        Miniature Airborne GPS Receiver (MAGR)

 

 V.         Procurement, Introduction and Training Considerations

 

 

                       THE NEED FOR IMPROVED

                   HELICOPTER NAVIGATION SYSTEMS

 

      The Marine Expeditionary Unit (Special Operations

 

Capable) (MEU(SOC)) embarked aboard Navy amphibious shipping,

 

is the smallest forward-deployed Marine Air-Ground Task Force

 

(MAGTF) and is considered to be the most responsive MAGTF in

 

the Marine Corps.  The MEU(SOC) is the immediate response,

 

on-scene, sea-based Marine component of the fleet commander's

 

amphibious and power projection forces.  The MEU is normally

 

composed of a reinforced infantry battalion -- Battalion

 

Landing Team (BLT) as the Ground Combat Element (GCE), a

 

composite helicopter squadron as the Aviation Combat Element

 

(ACE), and a MEU Service Support Group (MSSG) as the combat

 

Service Support Element (CSSE).  Advanced training and the

 

addition of specialized equipment enhances the individual

 

skills and unit capabilities required for the performance

 

of MAGTF special operations, thus adding the "SOC"

 

designation.(11:31-36)  In addition to being capable of

 

conducting amphibious operations of limited scope, the

 

MEU(SOC) is capable of conducting a variety of special

 

operations to include Noncombatant Evacuation Operations

 

(NEO), Clandestine recovery operations, Tactical Recovery of

 

Aircraft and Personnel (TRAP), in-extremis hostage rescue,

 

airfield seizures, and the seizure of static Gas/Oil

 

Platforms (GOPLATS). (13:25)  FMFRP 2-12 states,

 

      Most important is the MEUs capability to conduct

      quick reaction long-range amphibious raids over-

      the-horizon without electronic emissions, during

      periods of darkness, and under adverse weather or

      sea conditions with 6-hour notice. (11:33)

 

            The primary means of transportation for many of these

 

missions is the embarked Marine Corps helicopters.  Due to

 

the nature of these missions, they are most often conducted

 

under the cover of darkness and require pin-point accuracy

 

and split-second timing.  Aircraft arriving early, late, or

 

not at all due to navigation problems could have dire

 

consequences for the forces on the ground and/or the

 

civilians/hostages that are the focus of a mission.  In

 

addition to the potential loss of life from a failed or

 

aborted mission, the political implications must be

 

considered.  Although not a direct result of navigation

 

problems, the Iranian hostage rescue mission in 1979 clearly

 

demonstrates the possible national and international

 

political ramifications from a failed mission.  In the

 

Holloway Report on the Iranian Rescue Mission, investigators

 

indicated that the helicopters used were "austerely

 

prepared," referring to the fact that they were not equipped

 

with state-of-the-art equipment, although they did carry

 

precision inertial navigation systems (PINS) and Omega

 

navigation systems. (7:77)  Twelve years later, our

 

helicopters are still flying with the same type equipment!

 

The navigation equipment on board Marine Corps helicopters,

 

tasked to fly in support of these MEU(SOC) missions, Is

 

inadequate to meet the demanding mission requirements.  The

 

Marine Corps must move aggressively to procure advanced

 

navigation systems for its helicopters, seeking both short-

 

and long-term solutions.

 

            The standard navigation equipment installed on all

 

Marine Corps helicopters consists of the low-frequency,

 

automatic direction finding (LF/ADF) set and the tactical air

 

navigation (TACAN) set.  The LF/ADF provides relative

 

direction to a transmitting station, and the TACAN system

 

provides direction and range to the transmitting station.

 

Both systems were designed to give navigation information to

 

aircraft flying at minimum specified altitudes due to terrain

 

or obstacle clearance requirements while under instrument

 

conditions and to enable aircraft to safely conduct

 

standardized instrument approaches to airports.  The systems

 

require land-or ship-based transmitters, and the accuracy of

 

the systems improve as aircraft approach the transmitter

 

sites.  Unless one of these transmitters is located in the

 

mission objective area, neither system is of value within the

 

tactical environment.  Although the Marine Air Control Group

 

(MACG) detachment of the ACE can deploy with the TPN-30

 

Ground Landing System (GLS), the system is only capable of

 

providing range information to helicopters.  The Marine Corps

 

is currently pursuing a modification to the TPN-30 which

 

includes the addition of a TACAN, which will provide range

 

and azimuth information. (12)  However, this system would

 

still be primarily used for expeditionary airfield or

 

shore-basing operations and of little value in short duration

 

special operations.  Two additional systems with potential

 

for tactical use have been installed on some helicopters.

 

            The CH-53 helicopter and a limited number of CH-46

 

helicopters have Omega Navigation Systems (ONS) installed

 

which receive and process Omega and very-low-frequency (VLF)

 

signals to provide worldwide navigation capability.  The

 

system must be initialized (told where it is) upon start-up,

 

which can present some unique problems during shipboard

 

operations, as discussed later.  Additionally, the operators

 

manual states that manual position updates should not be

 

accomplished unless the system error exceeds three nautical

 

miles; this would indicate an accuracy factor of several

 

miles, although the system may be capable of better

 

results.(10:4.2.1)  Long Range Navigation (LORAN) systems

 

have also been installed on a limited number of aircraft.

 

This system, which is capable of self-initialization, uses

 

low-frequency (LF) radio signals from a series of master and

 

slave stations (called chains) divided into geographical

 

regions, to triangulate the aircraft's position, often with

 

accuracy within a couple hundred feet.  Fortunately for the

 

U.S., there is a LORAN chain centered in Saudi Arabia, which

 

provided coverage for the Iraq/Kuwait battle areas of Desert

 

Shield/Desert Storm.  Unfortunately, with the exception of

 

extensive coverage of the North American continent, global

 

coverage is limited.  Although these two systems appear to

 

provide some of the needed capability, neither system

 

completely fills the requirements, as demonstrated by the

 

following examples.

 

            During 1989, a MEU(SOC) was off the coast of Lebanon

 

preparing for the possible evacuation of the U.S. Embassy.

 

The mission was to be conducted at night.  Helicopters were

 

to be launched from ships 15 to 20 miles off the coast,

 

proceed to the beach and locate a single stone jetty. The

 

jetty was the initial point to guide them to the embassy,

 

which was located a mile inland within a built-up area.

 

LORAN coverage did not exist in the area.  The process of

 

initializing the ONS on a moving ship, vice a stationary land

 

point, can introduce errors of a mile or more into the system

 

before the aircraft takes-off.  This factor, combined with

 

the indicated accuracy of the ONS and the fact that the

 

mission did not allow for a precision update over land prior

 

to reaching the Embassy, made the system unsuitable for the

 

mission.

 

            Operation Eastern Exit, the NEO from the U.S. Embassy in

 

Mogadishu, Somalia, in January 1991, required two CH-53E

 

helicopters to launch at 0347 local time for a 466 nautical

 

mile flight with two in-flight refuelings in order to reach

 

the embassy.  The Omega navigation system, which is the

 

CH-53E's primary long-range navigation system, failed to

 

provide navigation information in either aircraft shortly

 

after take-off.  The Indian Ocean area, from which the

 

aircraft launched, is one of the areas not completely covered

 

by omega signals.  Although one system did start providing

 

information later in the flight, it was used as a backup

 

system for the remainder of the flight.  In their report on

 

Operation Eastern Exit, the Center for Naval Analysis states,

 

            Thus, flying over water at night, the CH-53Es

            relied on a combination of positive control from

            Guam (to approximately 60 miles from the ship),

            dead reckoning, and pathfinding by the KC-130s

            [aerial refuelers] for their navigation.  An

            upgraded navigation system, whether an inertial

            navigation system (INS) or one based on the global

            positioning system (GPS), would be valuable if

            CH-53Es are to be prepared to conduct other

            long-range missions. (9:48)

 

 

            During Operation Provide Comfort a section of

 

helicopters, returning from a refugee relief mission in the

 

mountains along the Turkey/Iraq border, became disoriented

 

trying to circumnavigate bad weather.  Unsure of their

 

location and running low on fuel, they elected to land near a

 

small military outpost, which fortunately happened to be on

 

the Turkish side of the border!  Again, LORAN coverage was

 

not available in the area and neither aircraft had the ONS

 

installed, due to limited system availability.

 

            In the event of an in-extremis hostage rescue attempt,

 

the assault forces will normally make their way to the

 

objective area by clandestine means.  The "take down" usually

 

commences at a prearranged time and helicopters must arrive

 

at the pick-up point within minutes to extract the forces

 

prior to enemy reinforcements arriving on scene.  Errors in

 

navigation by the helicopter crews that cause them to arrive

 

early could compromise the mission and if they arrive late

 

they may find the assault forces dead or captured by the

 

enemy.  Timing and accuracy is critical to mission success!

 

All of the systems mentioned previously fail to provide

 

the navigation coverage and accuracy required to optimize the

 

chances for success on the demanding missions assigned to the

 

MEU(SOC).  However, a relatively new system called the Global

 

Positioning System or GPS, has demonstrated the potential to

 

meet the requirements.  Unlike other navigation systems which

 

are land-based, GPS is a space-based system employing a

 

constellation of 21 satellites and 3 in-orbit spares which

 

continuously transmit their position and the time (based upon

 

an internal atomic clock).  A GPS receiver uses this

 

information to triangulate its position with an accuracy of

 

approximately 10-15 meters, although the Department of

 

Defense can degrade the accuracy of GPS for military purposes

 

using an operational mode called "Selective Availability"

 

(S/A).  The receiver must be able to "see" three satellites

 

in order to provide a 2-dimensional position and a minimum of

 

four satellites to provide a 3-dimensional (includes altitude)

 

position.(4)  Although the GPS constellation is not yet

 

complete (currently there are 5 Block I test-phase model and

 

12 Block II operational model satellites in orbit), the Air

 

Force Space Command anticipates continuous worldwide

 

2-dimensional coverage by Spring of 1992, and worldwide

 

3-dimensional coverage by late Summer of 1992.(1:6; 6:60)

 

Until that time, there will be coverage gaps as the available

 

satellites move in their orbits and occasionally drop from

 

view.  As was demonstrated during Operation Desert Shield/

 

Desert Storm though, this is not a problem as the satellite

 

orbits can be changed by Air Force control stations in order

 

to provide continuous coverage for selected areas.

 

            One version of a GPS receiver already being used on a

 

limited number of Marine Corps helicopters is the Trimble

 

TRIMPACK.  The Trimble TRIMPACK is a rugged, self-contained,

 

hand-held GPS receiver with a built-in antenna.  While not

 

originally designed for aircraft use, its compact size (6.5"W

 

x 7.0"D x 2.0"H) and optional remote antenna make it easily

 

adaptable for helicopter use with minimum aircraft modifi-

 

cations.  Although wiring the aircraft for the receiver

 

requires several hours, the receiver can be mounted in the

 

cockpit of a helicopter simply by using velcro to attach it

 

to the glareshield (dashboard) or console.  Thus the unit can

 

remain portable for use in other similarly equipped aircraft

 

or for hand-held use in the field.  The receiver operates

 

from a variety of battery types for flexibility and an

 

external power cable is available which enables the receiver

 

to operate off of aircraft power.  Additionally, the

 

receiver's display is compatible with the night vision

 

devices currently used by pilots.

 

            The Marine Corps originally purchased 250 TRIMPACK

 

units; these were disseminated throughout the Fleet Marine

 

Force (FMF) to both air and ground forces for testing and

 

evaluation.  The units became highly sought after during

 

Desert Shield/Desert Storm and received high accolades from

 

all who had access to them during the war.  Due to the lack

 

of identifiable terrain features and accurate maps of the

 

desert in Southwest Asia for navigation, the use of GPS was

 

instrumental not only for helicopter missions but also for

 

ground units to determine their location.  At forward-based

 

sites, Marine AV-8B Harrier pilots would reinitialize their

 

Inertial Navigation Systems (INS) using position information

 

supplied by the GPS receivers from helicopter crews!  The

 

receiver's ability to tell time from the satellite's atomic

 

clock eliminated the need for units to synchronize watches

 

for missions that required exact timing.(8:5)

 

            Long range navigation routes have been flown with the

 

TRIMPACK at various altitudes and airspeeds with typical

 

error rates of less than 0.1 to 0.2 nautical miles.  It has

 

been noted that the accuracy of the system is often better

 

than the pilot's ability to plot checkpoints off the typical

 

1:50,000 and 1:250,000 scale maps that are used for heli-

 

copter navigation.  Checkpoints are normally plotted to six

 

digits when using the grid reference system and to tenths of

 

a minute or rarely whole seconds for the latitude/longitude

 

reference system.  The TRIMPACK wild accept grid locations to

 

ten digits and latitude/longitude locations to tenths of a

 

second!

 

            Trimble Navigation has recently expanded its line of

 

civilian GPS receivers designed specifically for aircraft.

 

One of these receivers is the DZUS GPS Navigator which is

 

designed to be DZUS-rail configurable, the standard mounting

 

system for military and commercial aircraft.  The Navigator

 

is available in a GPS only or GPS/LORAN combination.  The

 

system includes a navigation database of worldwide aviation

 

information including airports, navigation aids, airspace

 

boundaries and much more.  Trimble expects to have "military"

 

versions of these systems, which would include military grid

 

reference and "P code" capability, available this year.  A "P

 

code" receiver's accuracy is not effected when DOD initiates

 

S/A mode operations for the GPS satellites.  Additionally, a

 

half-dozen or more manufacturers are also currently producing

 

various versions of GPS receivers for aircraft use at this

 

time.

 

            The Marine Corps is currently conducting research and

 

development on the Position Location Reporting System (PLRS),

 

APN-217(V3) doppler navigation system and several GPS pro-

 

grams specifically designed for aircraft.  These GPS pro-

 

grams include upgrading the APN-217(V5) and Omega systems

 

with embedded GPS receivers and the Miniaturized Airborne GPS

 

Receiver (MAGR) program.

 

            While PLRS provide excellent accuracy and incorporates

 

several other useful functions, it should not be considered a

 

primary navigation system for helicopters because like the

 

TACAN, PLRS requires a "Master Station" to be located in the

 

operating area before it can be used.  The system would be of

 

little or no value in long-range special operations.  The

 

APN-217(V3) doppler navigation system has been under

 

development since 1985 for use in the CH-46 helicopter.  The

 

system requires initialization upon start-up (like Omega);

 

then using precision measurements of movement, updates the

 

location based upon the units original starting point.  After

 

seven years of development the system has yet to be installed

 

in fleet aircraft and during recent developmental testing had

 

difficulty meeting navigation accuracy requirements.

 

Additionally, sources at Headquarters, Marine Corps have indicated

 

that the manufacturer has been unable to integrate a GPS

 

receiver with the APN-217(V5) and that aspect of the program

 

has been discontinued.  The case for the APN-217(V3) is still

 

pending; if it can meet requirements, it could be paired with a

 

"stand-alone" GPS receiver such as the MAGR as a viable

 

navigation aid.  APN-217 installation is currently projected

 

to commence in 1994 and take several years to complete.

 

            Currently the CH-46 is the only helicopter equipped

 

with the AN/ARN-148 (Trimble TNL-7880) Omega receiver, which

 

is capable of being upgraded with a GPS receiver.  The Litton

 

211 Omega receiver in the CH-53E is an older system and will

 

not accept a GPS upgrade.  The Marine Corps currently has 48

 

complete AN/ARN-148 mission kits and an additional 48 instal-

 

lation kits installed on the CH-46s so that the units can be

 

rotated among aircraft.  This equates to an average of three

 

systems for each tactical squadron (containing twelve air-

 

craft), with four or five additional aircraft configured to

 

accept the system.  Since this system was intended as an

 

interim solution until the AN/APN-217(V3) was available,

 

there are no plans at this time to purchase additional

 

systems for the CH-46 or other aircraft.  The AN/ARN-148 with

 

the GPS upgrade has been evaluated by Marine Helicopter

 

Squadron One (HMX-1) and has been deemed a "significant

 

improvement" over the current system. (2:7)

 

            The MAGR is considered a "non-developmental item," which

 

means it is a derivative of an off-the-shelf, commercial

 

product, the "3A".  This reduces research and development

 

costs and time.  The MAGR is currently undergoing testing and

 

if accepted, initial fleet installation of the MAGR or the

 

slightly larger 3A (for aircraft with larger avionics bays)

 

is scheduled to commence in 1994 and run for five years.

 

            Unfortunately, programs still in the developmental stage

 

will not solve the navigation problems for the MEU(SOC)s

 

currently deployed worldwide.  There exists an immediate need

 

to upgrade helicopter navigation capabilities before the next

 

mission is flown!  Additionally, whichever system or systems

 

are decided upon must be procured in sufficient quantities to

 

provide pilots adequate training time over familiar terrain

 

to properly learn how to use them.  The introduction of the

 

AN/ARN-148 OMEGA and LORAN systems into the CH-46 aircraft

 

are perfect examples of how not to add a new system.  On

 

separate occasions, these systems were installed in a limited

 

number of aircraft-just prior to the squadrons (to which I

 

was attached) departure to the Mediterranean for six-month

 

deployments.  Manuals were scarce and only a handful -of

 

pilots flew with the systems often enough to become profi-

 

cient with them.  Most pilots viewed trying to use them as a

 

distraction when flying over unfamiliar terrain in foreign

 

countries and preferred to rely on terrain navigation,

 

leaving the systems turned-off.  The Holloway Report,

 

referring to the navigation systems on the Navy RH-53Ds used

 

in the Iranian Rescue Mission, states the crews had "received

 

only limited training (in the systems) and expressed low

 

confidence in the equipment and their ability to employ

 

it." (7:78)  Hence, their primary means of navigation was dead

 

reckoning with the map and compass.

 

            Obviously, the procurement of any aircraft system is a

 

complex undertaking, often planned and budgeted for years in

 

advance.  The APN-217 system has been planned for in con-

 

junction with the addition of a cockpit management system

 

(CMS); both the APN-217 and the MAGR require integration with

 

a CMS or some other type cockpit display system in order to

 

function.  All the systems require some additional "acces-

 

sories" in order to work, adding to the planned costs.

 

Prices vary depending on the number of systems procured and

 

range from as low as 5000 dollars for a basic TRIMPACK to

 

over 100,000 dollars for the APN-217(V3) with a display unit.

 

The AN/ARN-148s in the CH-46 can be upgraded with GPS for

 

around 10,000 dollars per unit, a military version of the

 

DZUS GPS Navigator is expected to cost around 20,000 dollars

 

per unit when available, and the MAGR with a display unit is

 

projected to cost in the neighborhood of 50,000 dollars

 

per unit.

 

            Political as well as economic considerations unfortunately

 

also play a role in the process of procuring aircraft systems.

 

should money be spent to upgrade the CH-46E when the Marine

 

Corps is pursuing a replacement for it?  Will money spent now

 

on an interim system reduce the funding available for long-

 

term solutions?  Would a GPS upgraded ARN-148 Omega threaten

 

the higher costing APN-217(V3) program which is already

 

funded and of which the Marine Corps already owns 65

 

uninstalled systems?  If the APN-217(V3) is cancel led, what

 

impact would that decision have on the associated cockpit

 

management system-which is a separate system but funded as

 

part of the APN-217 package?  while the impact of interim

 

fixes on the long-term goals must be evaluated, the impact of

 

inadequate navigation capabilities on the performance of

 

missions assigned to the MEU(SOC) must carry a greater weight

 

in the decision making process!

 

            The Trimble TRIMPACK, although not designed for aircraft

 

use, is inexpensive (compared with most aircraft systems),

 

currently available, and has proven itself to be an excellent

 

system capable of delivering the navigation capabilities

 

needed until follow-on systems can be developed and delivered

 

to the FMF.  Because it is portable, the receivers can be

 

easily rotated between antenna-equipped aircraft, reducing

 

the number of receivers necessary to equip the fleet's

 

helicopters.  The AN/ARN-148 Omega systems in the CH-46

 

aircraft can be upgraded with GPS, to capitalize on the best

 

of both systems, for little more than the cost of the

 

TRIMPACKS.  Within the year, the DZUS GPS Navigator may prove

 

to be an excellent low cost system for all the fleet's

 

helicopters.  At least one of these systems or a combination

 

of these systems, such as TRIMPACKs and 148 upgrades, should

 

immediately be purchased in sufficient quantities to meet the

 

current needs of the helicopter community while development

 

continues on the more advanced and integrated systems for the

 

future.  The Marine Corps cannot afford to needlessly

 

jeopardize the success of the demanding missions assigned to

 

the MEU(SOC) due to inadequate navigation equipment when the

 

technology exists-to improve it today!

 

                                 BIBLIOGRAPHY

 

 

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1991. Quantico.

 

3.            Gabriel, Richard A. Military Incompetence: Why the

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Noonday Press, 1985.

 

4.            "The Holloway Report: Iran Rescue Mission #3."  Aviation

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12.   U.S. Marine Corps.  Marine Corps Lessons Learned System,

Report number 71941-37553 (01363). Quantico, 1991.

 

13.   U.S. Marine Corps.  USMC Landing Force Training Command,

Atlantic.  Marine Air-Ground Task Force Pocket

Guide, LFTCLANT 0305-3(3-90).  Norfolk, 1990.