case study: the military

Chapter 9

Case Study: The Military

ContentsPage

THE NATURE OF MILITARY OPERATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185Military Tasks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187

OPERATIONS REQUIRING 24-HOUR MANNING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 188Army Operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...,*. 188Air Force Operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 189Navy Operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. ... ..+,..... 190Marine Corps Operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192

SUMMARY AND CONCLUSIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193CHAPTER 9 REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ● .*.**.* .*** 193

TablesTable Page9-1. Crew Endurance Guide for Flight Operations, U.S. Army . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1899-2. Maximum Flight Duty Periods, U.S. Air Force .,...., . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1909-3. Maximum Accumulated Individual Flight Times, U.S. Navy . . . . . . . . . . . . . . . . . . . . . . . . . 192

Chapter 9

Case Study: The Military

As Operation Desert Storm illustrated, technolog-ical advances have dramatically increased the abilityof the military to carry out operations at night. Inaddition, many military situations demand thatpersonnel engage in operations that require 24-hourmanning and around-the-clock work. These opera-tions can lead to circadian rhythm disruption, sleeploss, and other stressors (13). Many military settingsthat require continuous manning (e.g., command andcontrol, medical, security, communications, shipnavigation and propulsion, most transportation sys-tem operations) have civilian equivalents; others donot. For the most part, military work that has nodirect civilian counterpart is performed on a continu-ous basis. This case study focuses on operations andwork settings that are unique to the military andexamines the typical duty schedules employed bythe U.S. armed forces for carrying out those opera-tions.

THE NATURE OF MILITARYOPERATIONS

An important characteristic of military activity isthe context in which operations and tasks are beingcarried out. That context determines the tempo atwhich tasks are to be performed and the nature of thestressors associated with job performance. A taskbeing performed during routine operations or intraining can be very different when performed underactual or simulated combat conditions. Routineoperations are those that are characteristic of peace-time and usually involve regular duty and restschedules for continuous reaming of tasks. Incontinuous operations, work is unceasing, but thedemands on the individual are not; in sustainedoperations, the individual has to maintain perform-ance for long periods (usually more than 12 hours).Sustained operations are characteristic of combat orhigh-alert conditions and are often characterized bysharply increased tempo (surge conditions). As aresult, in sustained operations individuals haveinadequate opportunity for rest, making sleep lossand fatigue limiting factors in an operation. Insustained operations, sleep loss often results fromthe need for an individual to perform some vitalfunction almost continuously for an extended periodof time. The amount and tempo of work (especially

mental work requiring attention and concentration)and the availability of nonsleep rest periods willdetermine the rate at which performance degrades,with faster work tempos causing faster degradationof performance (l). Although this report is con-cerned with the factors limiting personnel endur-ance, other factors, such as having enough materiel(munitions, fuel, other supplies), equipment (servic-ing and repair requirements), or information (com-mand and control decisionmaking, communicationlimitations, or intelligence and situation assess-ments) can also limit the duration of fast-pacedcombat or training activities.

The nature of work and rest schedules can also bealtered when military units are transported to differ-ent areas. The extra tasks involved in relocationoperations disrupt individual schedules, and trans-meridian relocations add jet lag to other disruptions.Rapid aerial deployment of military units overseasresults in jet lag, and the first day or two at sea ofteninvolves extra tasks. Relocation of forces can alsooccur under surge conditions (the beginning ofcombat operations, combat reinforcement opera-tions, and major training exercises), in which casedisruptions and stressors associated with both nor-mal relocation and surge conditions are present.

Various disruptions of biological rhythms andstressors that lead to performance decrements areassociated with these situations. Short-term desyn-chronization of circadian rhythms can result fromchanges in operations (e.g., relocation overseas) orchanges in operating tempo (e.g., at the onset ofhostilities or at the start of a major operation). As inshift work in the civil sector, chronic disruption ofcircadian rhythms may result from constantly shift-ing schedules and schedules that require daylightrest and night duty, such as the 18-hour duty cycleoften found in submarines, the 12-hour duty cycleoften used on ships, or the deployment of night-fighter teams on the battlefield. Both acute andchronic sleepiness may occur in these situations,especially under sustained operating conditions, andthese, in concert with circadian disruption or on theirown, can lead to degradations in performance.

Training and operational readiness exercises are aconstant fixture in the military. These exercises are

–185–

as realistic as possible, replicating as closely aspossible the conditions and schedules that would beencountered during combat. Although training exer-cises cannot duplicate the stress and fear encoun-tered in actual combat, they do mimic the nature andtempo of such operations. As a result, militarypersonnel are routinely and repeatedly exposed tothe various conditions described.

Activities that occur in conjunction with combator combat training are usually marked by anincreased tempo and sustained hours of duty. An-other factor which can impinge on military dutyhours are manpower limitations. For example, in theNavy there are manpower documents that outline thelevel of manning of a ship necessary for a givenoperation. A loss of manpower due to casualties orsickness will result in a mismatch between man-power resources and mission requirements. Thissituation would require that the available crew workextended duty hours to successfully complete themission (21).

There are few specific regulations or guidelines inthe military related to hours of service and schedul-ing. Regulations limit flight hours and length of dutyfor aviators in all the services; however, decisionsregarding hours of duty and work schedules for allother military personnel are generally left up tocommanding officers, who base their decisions ontheir knowledge of mission requirements and on thecondition and limitations of their personnel. Underroutine post, camp, and station operating conditions,in which service members can go home to theirfamilies at the end of each workday, military workschedules tend to resemble civilian work schedules.For personnel deployed in the field or at sea, workschedules tend to be about 70 hours per week. Intraining and operational readiness exercises, workoften continues until individuals are unable to go on.The existing guidelines for rest requirements inpeacetime are not binding in combat (29,38,40) andare frequently relinquished in order to accomplishthe mission (3,16).

Chapter 9--Case Study:The Military ● 187

Military Tasks

A variety of tasks have to be carried out at anytime, day or night, and are therefore susceptible tothe effects of disrupted biological rhythms and sleeploss. Since sustained operations are integral tomodern military operations, some of the most salientproblems for an individual are sleepiness (inclina-tion for sleep) and fatigue (weariness due to physicalor mental exertion). Both sleepiness and fatigueaffect performance. As with studies of task perform-ance in a civilian setting, studies of the effects ofaround-the-clock operations in military settingshave revealed that the nature of the task determinesits sensitivity to circadian disruption, sleep loss, andfatigue. For example, studies of sustained operationsover several days with little or no opportunity tosleep show that vigilance, memory, and cognitivetask performance of infantry soldiers, tank crews,and artillery fire direction teams are degraded (13).Although most people need 6 to 8 hours of sleepdaily to maintain normal levels of alertness andperformance, 4 hours of sleep can offer someprotection from the deleterious effects of sustainedoperations (13).

Tasks that require physical activity and effort(e.g., infantry marches, preparing fortifications,handling supplies) are not significantly affected bythe time of day, moderate sleep loss, or othercircadian disruptions (2,8,26,41) However, the per-ceived effort required to do a physical task issensitive to the time of day the task is performed,with greatest fatigue perceived between 2 a.m. and6 a.m. (11). If personnel are quite fatigued, as theyoften are during sustained operations, their ability toperform physical tasks can be reduced (2,10,13).Physical conditioning is important in all the serv-ices, because fit personnel have more endurance inthe performance of physical tasks, even thoughphysical fitness does not protect against the effectsof sleep loss.

Military operations also involve many tasks thatrequire constant vigilance, often under conditionsnot conducive to alertness. These include air defenseradar and electronic surveillance, sonar, sentries,pickets, and so on. The performance of many tasksrequiring vigilance (sonar operation, for example)degrades-measurably after less than an hour of duty(13,24). Performance is also degraded by sleep lossand being required to work at inappropriate timesduring the circadian cycle, regardless of amount of

rest (13,18-20,22). When vigilance is required insustained operations, naps can be effective, espe-cially if taken during the predawn period, from2 a.m. to 6 a.m. (13); however, relief from the task(i.e., simple rest) and sleep are the most effectivemeans of combating decrements in vigilance.

The operation and control of vehicles is also acommon characteristic of military operations. Stud-ies of the effects of fatigue on the performance ofaircraft pilots indicate that physical coordinationseems little degraded, even in conditions of extremesleepiness (15); however, judgment degrades fairlyquickly with the onset of fatigue (7,12,42). Thiseffect is compounded when tasks are performed nearthe nadir of the circadian alertness cycle. There areregulations to guide aircraft operations (describedlater) but no crew rest guidelines for land or watervehicle operators. The use of pharmacologicalagents to enhance performance in aircraft opera-tions, especially after long flights or during sus-tained operations, is being investigated (5).

The performance of other types of tasks associ-ated with military operations, such as the mainte-nance, preparation, and operation of equipment (e.g.,weapons systems, communication systems, con-struction equipment), may also be affected bycircadian, fatigue, and sleepiness factors associatedwith time and duration of duty. As with the othertasks described, this is especially true in the case ofsustained operations (13,23).

Finally, the task of commanding, which involvesjudgment and planning, is vulnerable to perform-ance degradation caused by sleep loss and biologicalrhythm disruption. In fact, judgment is usually thefirst faculty to be degraded, and it is a very difficultone for the individual to monitor (2,9,12). There areno regulations or guidance regarding the duty hoursassociated with command. Leaders and commandand control personnel generally stay awake and areinvolved during continuous and sustained combatoperations to see to their responsibilities. However,since effective leadership depends on unimpairedjudgment, and fatigue, sleep loss, and other biologi-cal rhythm disruptions impair judgment, avoiding orminimizing such effects is critical to successfulcombat leadership and command and control. Theimplementation of sleep discipline plans, a rela-tively new military innovation, is critical for combatleaders (14).

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188 ● Biological Rhythms: Implications for the Worker

OPERATIONS REQUIRING24-HOUR MANNING

Military operations that could be affected whenpersonnel are exposed to biological rhythm disrup-tion or sleep loss include combat operations (imme-diate involvement in fighting) and combat support(supply, communications, or medical aid), as well ascombat training exercises. This includes all aspectsof land combat (in-place, reinforcement, and expedi-tionary), support logistics operations, air operations(tactical and logistic), high-readiness operations ofstrategic forces, and the operation of naval vessels atsea. The most salient disruption in such cases isfatigue and sleep loss, exacerbated by various kindsof stress. Circadian disruption can also occur incombat operations: events such as strikes andassaults are often planned for the time at which theenemy is expected to be least effective. Momentumis very important in offensive operations (especiallyin land combat), and sustaining it for days or weeksentails many human endurance problems. Also,some element of surprise is always desirable incombat actions. The conduct of extended combatoperations (over days and weeks) tends to be moreeffective if there is no discernible routine to theaction. The need to carry out operations in whichroutines and predictability are minimized will havea negative effect on personnel duty-rest schedules.

Army Operations

With the exception of Army Aviation, there are nospecific guidelines for work schedules and dutyhours for most Army activities and operations. Intheir planning of operations, it is the responsibilityof individual commanders to ensure that the person-nel under their command are rested and fit for duty.

Deployment

Most military units are based in the United States;military units outside the United States are usuallydeployed for some limited period and then replaced.This deployment is usually scheduled well inadvance. Individual jet lag can best be mitigated byallowing for recovery periods at the destination.

Surge deployment is usually in response to somenew military requirement (e.g., the need to showforce to support foreign policy in a time and place oftension) and is done on short notice. It usuallyinvolves transmeridian movement by aircraft, so jetlag effects would be present. The requirement to

pack up, load, unload, and set up at a destinationcauses additional transient disruptions. Since thesetemporary tasks are not part of what is usuallythought of as combat or mission tasks, they are notincluded in the planning of operations (35,38).

Reinforcement

Reinforcement is adding more personnel andequipment to units already deployed. Usually, rein-forcement would be more urgent than relocation andwould require new personnel to begin operationsimmediately on arrival at the same operating tempoas existing forces. Reinforcement is most likely tooccur under surge conditions. The same disruptionsin biological rhythms that would be encounteredduring initial troop deployment could also occurduring reinforcement operations.

Special Operations

Special operations are difficult to characterize,given their inherent irregularity and classified na-ture. Special forces can be subjected to unpredicta-


Table 9-l-Crew Endurance Guide for Flight Operations, U.S. Army

Maximum duty Maximum flightTime period (hours) period (hours) time (hours) Environmental factor

24 16 8 Day48 27 15 Day contour/low level72 37 22 Instrument168 (7 days) 72 37 Night720 (30 days) (peacetime) 288 90 Day NOE720 (30 days) (mobilization) 360 140 Night terrain

Night vision devicesChemical MOPP

1.01.31.41.41.62.12.33.1

EXAMPLE : The stress and fatigue experienced in 1 hour of day nap-of-the-Earth (NOE) flight (e.g., extreme low-level, Contour flight) isequal to 1.6 hours of standard day flight. If a crew member flies day NOE in chemical mission-oriented protective posture(MOPP), the larger factor (3.1) will be used. The flight time shown in column 3 will be adjusted by the factors in column 4.

SOURCE: U.S. Department of the Army Regulation AR 95-3, Aviation, General Provisions, Training, Standardization, and/7esource Management.

ble and unanticipated requirements and must re-spond on short notice to anything from militarysearch and rescue missions to counterterrorism.Frequently these situations require rapid deploy-ment and the crossing of time zones. Planned orprogrammed duty-rest schedules usually are diffi-cult to implement in such situations (17). Specialoperations forces tend to train at a continuousoperations tempo, interspersed with periods ofsustained operations, combined with relocations onshort notice (often involving transmeridian travel).

Combat

For planning purposes, Army regulations specifythat combat personnel (those doing the fighting)should have 6 hours each day for rest (35). In actualcombat situations, as in the reinforcement andspecial operations outlined above, the nature andscheduling of rest periods would be dictated by theconditions of the moment.

Army Flight Operations

Army regulation 95-3 (36) governs schedulinglimits for flight operations of both fixed-wing androtary aircraft. These regulations provide guidancefor duty period and flight time limits for air crews(table 9-l). The limits are adjusted for the conditionsunder which the operations occur. For example,flying 1 hour at night is considered the same asflying 1.3 hours during the day. In addition, theregulations recommend that commanders consultthe unit’s flight surgeon and aviation safety officerwhen setting limits for specific operations or timeperiods.

Air Force Operations

Tactical and Transport Forces

Air Force tactical and transport flight operationsare guided by a number of regulations that providerequirements for scheduling (27-29,32,33). Tacticalforces engage in air combat, support land warfare(close air support, interdiction of enemy supplylines, surveillance), and consist largely of fighters,bombers, and helicopters. Transport forces carrypersonnel and materiel from the United Statesoverseas and from overseas supply depots to moreremote distribution points. These aircraft consistprimarily of tanker and transport craft. Exercises areconducted routinely to provide experience withvarious combat and readiness scenarios.

Rest and flight duty limitations for all personnelwho operate Air Force aircraft are delineated inseveral Air Force regulations (29-31,33). Theseregulations specify:

● maximum allowable flight duty periods forbasic and augmented crews,

. maximum monthly and quarterly flying hoursfor aircrews,

● minimum crew rest periods, and. conditions necessary to waive the require-

ments.

The maximum allowable flight duty period is themaximum number of hours crew can fly in a certaintype of aircraft in a 24-hour period (table 9-2). Totalflying time for tactical forces is limited to 75 hoursper 30 consecutive days and 200 hours per 90consecutive days (31). A minimum rest period of 12hours is mandated between flights and must include8 hours of uninterrupted, continuous rest. If a crew

190 . Biological Rhythms: Implications for the Worker

Table 9-2—Maximum Flight Duty Periods,U.S. Air Force

Basic AugmentedAircraft aircrew aircrewFighter, attack or reconnaissance

Single control . . . . . . . . . . . . . .Dual control . . . . . . . . . . . . . . .

Bomber or reconnaissanceSingle control . . . . . . . . . . . . . .Dual control . . . . . . . . . . . . . . .

Transport . . . . . . . . . . . . . . . . . . .Sleeping provisions . . . . . . . . .

Tanker . . . . . . . . . . . . . . . . . . . . . .Sleeping provisions . . . . . . . . .

Trainer . . . . . . . . . . . . . . . . . . . . .Rotary wing (no automatic

flight control system). . . . . . . .Rotary wing (automatic flight

control system) . . . . . . . . . . . .Utility . . . . . . . . . . . . . . . . . . . . . .

1212

12241616202012

12

1412

16

30

24

3016

14

1818

SOURCE: U.S. Department of the Air Force Regulation AFR 60-1, EUghtManagement.

member is interrupted and cannot get 8 hours of rest,he or she must be afforded 8 more hours ofuninterrupted rest plus reasonable time for otheractivities (e.g., dressing, eating, traveling) (31).These regulations also specify that the relationshipbetween crew rest and limitations on flight dutyhours be considered when planning and schedulingmissions. For transport crews, total flying time islimited to 125 hours per 30 consecutive days and 330hours per 90 days (33). Based on the timetableestablished for a deployment operation, a unit’scommander and flight surgeon may develop aschedule prior to departure that will adjust crewmembers’ body clocks (6). Finally, the regulationsauthorize commanders to waive maximum flightduty periods for high-priority missions and duringimpending or actual hostilities.

Nonflight Air Force support units (airfield opera-tions, communications facilities, logistic support,aircraft repair) are generally operated on a continu-ous basis. The factors affecting their operatingtempo and conditions are similar to Army combatsupport activities.

Maximum limits on duty hours for all Air Forcepersonnel (i.e., flight and nonflight) in a wartimesetting have been set at 247 hours per month (10

hours per day, 6 days a week) during continuousoperations and 309 hours per month (12 hours perday, 6 days a week) for a maximum of 30 days duringsustained operations (6).

Strategic Forces

Strategic forces are the nuclear deterrent intercon-tinental bomber and missile forces. These forcesoperate on a routine carefully designed and con-trolled to sustain operations without decrements inperformance. The primary concern is to ensure thatpersonnel with access to nuclear weapons arereliable and can carry out their duties withoutimpairments to their judgment or performance.1

Flight operations are guided by the general AirForce flight regulations previously described andothers specific to strategic forces operations (30).These regulations include the requirement that,when possible, missions with late-night departures(which cause the crew to fly through normal sleepinghours and to rest during normal working hours) bescheduled for less than maximum duty periods.Also, the regulations stipulate that crew memberswho cross more than three time zones on route to apermanent location should normally not be requiredto perform any additional flight duty for the first 48hours after arrival at their destination (30).

The crews manning intercontinental ballistic mis-sile silos are on alert duty for 24-hour periods.Regulations stipulate that the minimum rest-sleepperiod for each crew member is 6 hours (34). Ingeneral, these crews are on duty every third day.When relieved of duty, a crew member will have aminimum rest period of 12 hours.

Navy Operations

Nonshipboard operations are similar to Army orAir Force nonflight operations as far as schedulingis concerned. Ships in port maintain duty-restschedules very much like those of activities ashore,nominally modeled on a 40-hour workweek, withlimited personnel standing watch around the clock(see later discussion). When deployed, there is atransition to the at-sea routine, which typicallyconsists of a 70- to 80-hour workweek (38).

l~ch semice has a tighfly con~o~~ pmsonnel Reliability Program which covers all persons who have duties invOlvkg aCCeSS tO nUckXU wmpo~(from the technicians who put them together and do maintenance on them, to the crews who prepare them to fue or be dropped, to the CXEWS who fmor drop them). The program involves background checks, regular reviews by medical officers and commariders, and annual certification of behavioralreliability for each person in the program.


Shipboard operations require that some tasks beperformed on a continuous basis. Unlike land-basedfacilities, where there may be local resources to drawon, each ship must be entirely self-sufficient. Thecrew must not only carry out the mission of the shipbut also perform all housekeeping and maintenancetasks associated with it. Thus, normal operations ona ship have the character of continuous operations.Typically, jobs on board ship are divided into twotypes. Work that is general in nature, such asmaintenance and repair tasks, is routinely carried outon board ships at sea using a 12-hour shift schedule(12 hours on, 12 hours off’) (38,39). Tasks thatrequire an individual to operate a specific piece ofequipment or be at a specific station (sonar, radar,communication operators, engine room personnel)are manned using a watch schedule. A person whois on watch is at his or her station for a certain periodof time and is then relieved by the next personstanding watch. The specific watch schedules forsubmarines and surface ships are described later;however, they often result in personnel constantlychanging the hours they are active and the hours thatthey are sleeping. Thus, these schedules causesubstantial circadian disruption. A study that exam-ined the effects of watch schedules on merchantships has shown that these schedules are associatedwith sleep disturbances, decreased alertness, anddecreases in measures of performance (4,25).

Several conditions of readiness modulate a ship’swork schedule. Condition I Battle Readiness is theequivalent of sustained operations; all systems aremanned and operating, and no maintenance isconducted except maintenance associated with keep-ing watch and urgent repairs. The crew does not haveany rest period and is expected to be able to endureCondition I for 24 continuous hours. Condition IIBattle Readiness means that required operationalsystems are continuously reamed and operating, butthe crew does have 4 to 6 hours of rest per person perday. Urgent preventive maintenance and supportfunctions are carried out. Other conditions areWartime Cruising Readiness, Peacetime CruisingReadiness, and Inport Readiness, as well as readi-ness for specific types of ships (e.g., mine counter-measures, amphibious operations, supply ships)(21).

Submarines

The essence of submarine operations is to remainundetected, and that, in turn, depends on maintaininga very high state of vigilance. Undersea is asignificantly more hostile environment than thesurface, with much less time available to respond tomechanical problems that arise, so propulsion andcontrol (and related systems) vigilance must be highand sustained as well. There are two types ofsubmarines, ballistic missile and attack submarines.Ballistic missile submarines carry nuclear missilesand operate in a mode that is essentially a combina-tion of independent operations and Air Force strate-gic forces operations. Their task is to remain in theirassigned area, undetected, and be ready to launchtheir missiles if so ordered. Attack submarines havemore varied tasks, including defense of a group ofsurface ships, information gathering, and attacks onenemy shipping. Both ballistic and attack submarineoperations at sea use 18-hour watch schedules,consisting of three sections of personnel rotating6 hours on, 12 hours off. Generally, the 6-hour onperiod is the time an individual is engaged in his orher specific job (e.g., sonar operator, radio operator).The 12-hour off period is used for sleep and rest aswell as other activities, including meals, mainte-nance, training, and administration. Typically, acrew member averages 4 hours of sleep during an18-hour cycle, depending on the tempo of theoperations, training, and maintenance, with eachsleep period occurring 6 hours earlier than theprevious one (37). Analogous to a rotating shiftschedule, watch scheduling results in individualswho will always be active and sleeping at differenttimes of the day and whose sleep periods willgenerally be shorter than normal.

Surface Ships

Naval surface ships include combat vessels andsupply ships. During routine operations at sea, thewatch schedules depend on the size of the crew,which will determine how many sections of person-nel are used. Usually, schedules are based on dutycycles of 12 hours (two sections with 6 hours onwatch, 6 hours off; three sections with 4 hours onwatch, 8 hours off), 16 hours (four sections with 4hours on watch, 12 hours off), or 18 hours (threesections with 6 hours on watch, 12 hours off). The onperiod is the time when the crew member is engagedin a specific job, while off time is divided amongother tasks, eating, and sleeping. Crew members on


surface ships average 6 hours of sleep per 24 hours(37), and their watch schedules require them toconstantly change their hours of activity and rest.

Supply ships replenish combat ships with fuel,foodstuffs, parts, and munitions. Replenishing sup-plies while at sea can upset the duty-rest routine ofa large portion of the crew on the ship being suppliedbecause of the extra tasks required (e.g., tendinglines, standing extra lookout watches, stowingsupplies). The frequency of underway replenishmentdepends on the activity of the ship, but replenish-ment every 3 or 4 days is not uncommon, principallybecause combat ships are maintained as nearly fullof fuel and other supplies as possible all of the time.

Under combat conditions, when the crew of a shipis at general quarters for extended periods, acutefatigue can become a problem. In combat there is aconstant threat of attack from the air, submarines,and other ships. The entire crew is on duty withoutrelief in order to carry out all of the defensive andother operations required. Activity under theseconditions is fast-paced and continuous; sleep andrest are often sporadic and irregular.

Aircraft carrier operations involve the same tasksas other combat surface vessels but include tasksinvolved in flight operations. These tasks includemoving aircraft around, preparing them for flight,operating catapults and arresting gear, air trafficcontrol, and all other operations that support aircombat mission preparation and control. Generally,aircraft carriers carry enough personnel to make upone complete shift to operate the equipment and dothe tasks required to conduct flight operations.During continuous flight operations, this shift issplit; thus, flight operations do not involve the kindof rotating work-sleep schedules so common onother ships. Crews ordinarily work about 14 to 16hours each day; during periods of sustained activity,they may work nearly continuously (20 hours or soeach day) for several days. Operating for extendedperiods at general quarters is even more disruptiveaboard an aircraft carrier than other surface combatships because of the far greater amount of movementof men and materiel from one part of the ship toanother in conducting flight operations. Crew mem-bers are effectively in a sustained operations mode(none returns to sleeping quarters).

Table 9-3--Maximum Accumulated Individual FlightTimes, U.S. Navy

Maximum hours

Aircraft 30 days 90 days 365 days

Single-piloted. . . . . . . . . . . . . . . . 65 165 595Multipiloted (pressurized,

ejection seat) . . . . . . . . . . . . . . 80 200 720Multipiloted (nonpressurized) . . . 100 265 960Multipiloted (pressurized) . . . . . . 120 320 1,120

SOURCE: U.S. Department of the Navy, “Military Planning and the Impactof Circadian Rhythms on Military Operations,” briefing materialsprovided to D. Liskowsky, Offioe of Technology Assessment,Washington, DC, 1989.

Flight Operations

The Navy’s flight crew regulations are similar tothe Air Force’s in that they may not constrainoperations in wartime (40). These regulations spec-ify maximum hours of flight time: 6.5 hours per dayfor single-seat aircraft and 12 hours for other aircraft.They also specify that flight personnel should not beassigned to flight duty on more than 6 consecutivedays. The regulations indicate that 8 hours of sleeptime should be made available every 24-hour periodand that flight personnel should not be scheduled forcontinuous alert or flight duty (which requires theperson to be continuously awake) for more than 18hours. If the 18-hour rule is exceeded, 15 hours ofcontinuous off-duty time must be provided to theindividual. The maximum number of accumulatedhours of flight time for various aircraft is alsospecified (table 9-3). Finally, the regulations statethat if the tempo of operations requires an individ-ual’s flight time to exceed any of the guidelines, thatperson should be closely monitored and speciallycleared for flight by the commanding officer, withthe advice of the flight surgeon. In situations wherejet lag might occur (changing local sleep-awakeperiods, transmeridian flights), flight crews are notgrounded, but the guidelines suggest that closerobservation of the individuals by the flight surgeonmay be warranted (37,40).

Marine Corps Operations

Amphibious Assault

The opposed landing (coming ashore againstarmed opposition) is the essence of Marine Corpsoperations. It is a very intense period of sustainedoperations that changes to continuous operations ina day or two. Although seas and tides are importantfactors in the timing of amphibious assaults, most

Chapter 9--Case Study:The Military . 193

operations are planned to begin before dawn, whenthe enemy is expected to be least vigilant andeffective. As with Army combat operations, thereare no specific guidelines regarding duty hours forMarine combat units. The planning of operationsand the monitoring of the condition of troops are leftto the discretion of commanding officers. TheMarine air forces, which provide air support foramphibious assaults and other Marine ground opera-tions, are governed by the same flight crew duty-restcycle regulations as Navy flight crews (40). Underactual combat conditions, the limitations on flighthours imposed by these regulations may be ex-ceeded. For example, in the case of amphibiousassaults, which tend to be fairly short in duration,these limits may be exceeded for the first 36 to 48hours of the operation.

SUMMARY AND CONCLUSIONSThe nature of many military operations requires

that personnel be engaged in activity at all hours andoften for extended periods of time. Within thecontext of these operations, personnel are required tocarry out a variety of tasks, the performance of whichcan be degraded as a result of disruptions inbiological rhythms, sleep loss, fatigue, and otherfactors. Decisions concerning the schedules usedand the duration of duty are generally left tocommanding officers, who base their judgments ontheir knowledge of the limitations of their personnelunder various conditions. There are few specificregulations or guidelines in the military related tohours of service and scheduling. An exception is theregulations that direct flight operations in all serv-ices. These regulations specify maximum allowablehours of flight duty and may include stipulationsregarding transmeridian flight, minimum necessaryrest periods, and the scheduling of flight operations.In the Navy there are specific guidelines, which havea long-standing tradition, for the scheduling ofwatches on board ships. They require that personnelstanding watch constantly vary their hours ofactivity and sleep, which results in a constant stateof circadian desynchronization.

Finally, the overriding priority in all militaryoperations is the successful completion of themission. As a result, regulations regarding dutyhours are generally waived in wartime operations.There may be battle circumstances in which allavailable forces are needed, even if they will not befunctioning at optimal levels and even if their

effectiveness in the near future will be even moredegraded. Decisions concerning the disposition andactivities of personnel are guided by the demands ofa given situation, and the effects of performancedecrements due to biological rhythm upset, fatigue,and other factors may be accepted rather thanmediated in some wartime circumstances. A betterunderstanding of those decrements and their effectswill ultimately aid military commanders in balanc-ing the various factors that go into making suchdecisions.

CHAPTER 9 REFERENCES1.

2.

3.

4.

5.

6.

7.

8.

Balkin, T.J., Department of Behavioral Biology,Walter Reed Army Institute of Research, WalterReed Army Medical Center, Washington, DC, per-sonal communication, Dec. 19, 1990.Belen@, G.L., Krueger, G.P., Balkin, T.J., et al.,Effects of Continuous Operations (CONOPS) onSoldier and Unit Pe~orrnance: Review of the Litera-ture and Strategies for Sustaining the Soldier inCONOPS, Rep. No. WRAIR BB-87-1 (Washington,DC: U.S. Department of the Army, Medical Researchand Development Command, Walter Reed ArmyInstitute of Research, April 1987).Comperatore, C.A., U.S. Army Aeromedical Re-search Laboratory, Fort Rucker, AL, personal com-munication, Feb. 15, 1991.Condon, R., Colquhoun, P., Plett, R., et al., “Workat Sea: A Study of Sleep, and of Circadian Rhythmsin Physiological and Psychological Functions, inWatchkeepers on Merchant Vessels. IV. Rhythms inPerformance and Alertness,’ International Archivesof Occupational and Environmental Health 60?105-411, 1988.DeJohn, C. A., Effects of Psychophysiological Coun-termeasures on Pe~orrnance Decrement DuringSustained Flight Operations, Research and Technol-ogy Work Unit Summary Fiscal Year 1989 Adden-dum, Accession No. DN 248502 (Pensacola, FL:U.S. Department of the Navy, Medical Research andDevelopment Command, Aerospace Medical Labo-ratory, 1989).Garnbrell, B., Major, U. S.’ Department of the AirForce, Washington, DC, personal communication,July 17, 1989.Graeber, J. G., Rollier, R.L., and Salter, J. A., Continu-ous Operations SOP for BIFV Units, USA.RI Re-search Note 86-60 (Fort Benning, GA: U.S. Depart-ment of the Army, Research Institute for the Behav-ioral and Social Sciences Field Unit, 1986).Haslarn, D.R., “Sleep Ims, Recovery Sleep, andMilitary Performance,” Ergonomics 25:163-178,1982.


9.

10.

11.

12.

13.

14.

15.

16.

17.

18.

19.

Hegge, F.W., The Future Battlefield: Human Dimen-sions and Implications for Doctrine and Research,Rep. No. WRAIR NP-82-1 (Washington, DC: U.S.Department of the Army, Medical Research andDevelopment Command, Walter Reed Army Insti-tute of Research, December 1982).Hegge, F.W., and Tyner, C. F., Deployment Threats toRapid Deployment Forces, Rep. No. WRAIR NP-82-2 (Washington, DC: U.S. Department of the Army,Medical Research and Development Command,Walter Reed Army Institute of Research, December1982).Johnson, L. C., Freeman, C.R., Spinweber, C.L., etal., The Relationship Between Subjective and Objec-tive Measures of Sleepiness, NHRC Rep. No. 88-50(San Diego, CA: U.S. Department of the Navy,Medical Research and Development Command,Naval Health Research Center, December 1988).Kopstein, G., Siegel, A., Corm, J., et al., SoZdierPeq60rrnance in Continuous Operations, USARIResearch Note 85-68, prepared by Applied Psycho-logical Services, Inc. for the U.S. Army ResearchInstitute for the Behavioral and Social Sciences(Wayne, PA: Applied Psychological Services, July1985).Krueger, G.P., ‘Sustained Work, Fatigue, Sleep Imssand Performance: A Review of the Issues,’ Workand Stress 3:129-141, 1989.Krueger, G.P., “Sustained Military Performance inContinuous Operations: Combatant Fatigue, Restand Sleep Needs,” Handbook of Military Psychol-ogy, R. Gal and A.D. Manglesdorff (eds.) (London:John Wiley & Sons, 1991).Krueger, G.P., Armstrong, R.N., and Cisco, R.R.,“Aviator Performance in Week-Long ExtendedFlight Operations in a Helicopter Simulator,’ Behav-ior Research Methods, Instruments, and Computers17;68-74, 1985.Krueger, G. P., and Liebennan, H.R., U.S. ArmyResearch Institute of Environmental Medicine,Natick, MA, personal communication, Feb. 15,1991.Lindsay, J. J., General, Office of the Commander inChief, U.S. Special Operations Command, MacDillAir Force Base, FL, personal communication, June 7,1989.Mackie, R.R., Wylie, C. D., and Evans, S. M., “Fa-tigue Effects on Human Performance in Combat: ALiterature Review,’ draft working paper prepared forthe Institute for the Behavioral and Social Sciences,Medical Research and Development Command, U.S.Department of the Army, Goleta, CA, and AnnArbor, MI, October 1988.Morgan, B. B., Brown, B.R., Coates, G. D., et al.,Sustaining Pe@ormance During 36 Hours of Contin-uous Work and Sleep, F’RL Rep. No. ITR-75-31

20.

21.

22.

23.

24.

25.

26.

27.

28.

29.

30.

31.

32.

33.

34.

(Louisville, KY: University of Imisville, Performa-nce Research Laboratory, 1975).Morgan, B. B., and Coates, G.D., Sustained Per$orm-ance and Recovery During Continuous Operations,PAL Rep. No. JT’R-74-2 (Norfolk, VA: Old Domin-ion University, Performance Assessment Laboratory,1974).Naitoh, P., Naval Health Research Center, San Diego,CA, personal communication, Jan. 21, 1991.Naitoh, P., Englund, C.E., and Ryman, D.H., SleepManagement in Sustained Operations: User’s Guide,NHRC Rep. No. 86-22 (San Diego, CA: U.S.Department of the Navy, Medical Research andDevelopment Command, Health Research Center,July 1986).Naitoh, P., Englund, C.E., and Ryman, D. H., Sus-tained Operations: Research Results, NHRC Rep.No. 87-17 (San Diego, CA: U.S. Department of theNavy, Medical Research and Development Com-mand, Health Research Center, June 1987).Poulton, E. C., The Effects of Fatigue Upon SonarDetection, MRC NPRC Rep. No. OES 20-72 (I.xm-don: Royal Naval Personnel Research Committee,1972).Rutenfranz, J., Plett, R., Knauth, P., et al., “Work atSea: A Study of Sleep, and Circadian Rhythms inPhysiological and Psychological Functions, in Watch-keepers on Merchant Vessels. II. Sleep Duration, andSubjective Ratings of Sleep Quality,” InternationalArchives of Occupational and Environmental Health60:331-339, 1988.Ryman, D. H., Naitoh, P., and Englund, C. E., Per-ceivedExertion Under Conditions of Sustained Workand Sleep Loss, NHRC Rep. No. 87-9 (San Diego,CA: U.S. Department of the Navy, Medical Researchand Development Command, Health Research Cen-ter, 1987).U.S. Department of the Air Force Regulation AFR28-40, Mobility for Tactical Air and StrategicAerospace Defense Forces.U.S. Department of the Air Force RegulationAFR 2842, Mobility for Military Airlijit CommandForces.U.S. Department of the Air Force Regulation AFR60-1, Flight Management.U.S. Department of the Air Force Regulation AFR60-1, Flight ManugementlSAC Supplement 1.U.S. Department of the Air Force Regulation AFR60-1, Flight ManagementlTAC Supplement 1.U.S. Department of the Air Force Regulation MACR28-2, Contingency Planning Policies and Proce-dures.U.S. Department of the Air Force Regulation MACR55-1, Airlifi Operations.U.S. Department of the Air Force Regulation SACR55-66, ICBM Operations.


35.

36.

37.

38.

39.

U.S. Department of the Army Regulation AR 570-2, 40.Manpower Requirements Criteria (MARAC)-Tables of Organization and Equipment.U.S. Department of the Army Regulation AR 95-3, AlAviation, General Provisions, Training, Stanahd- “ization, and Resource Management.U.S. Department of the Navy, “Military Planningand the Impact of Circadian Rhythms on MilitaryOperations,” briefing materials providedtoD. Liskow-sky, Office of Technology Assessment, Washington,DC, 1989. 42.U.S. Department of the Navy Directive OPNAV-INST 1000.16F, Manual of Navy Total Force Man-agement.U.S. Department of the Navy Directive OPNAV-INST 3501 (series), Squadron Manning Document.

U.S. Department of the Navy Directive OPNAV-INST 3710.7M, NATOPS General Flight and Oper-ating Instruction.

Vogel, J.A., Sampson, J. B., Wright, J.E., et al., E~ectof Transatlantic Troop Deployment on PhysicalWork Capacity and Work Performance, USARIEMRep. No. T 3/79 (Natick, MA: U.S. Department of theArmy, Research Institute of Environmental Medi-cine, 1979).

Word, L.E., Observations From Three Years at theNational Training Center, USARI Research Product87-02 (Alexandria, VA: U.S. Department of theArmy, Medical Research and Development Com-mand, Research Institute for the Behavioral andSocial Sciences, 1987).

case study: the military

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