MAY 1 RECD

Accession No. 58181-64

Copy No. SID 63-328 

APOLLO IN-FLIGHT MAINTENANCE CONCEPT

Contract NAS9-150

15 Ap ril 1964

Exhibit I, Paragraph 3.5

N O R TH A M E R IC A N AVIATION, INC.

SPACE and INFORMATION SYSTEMS DIVISION
FOREW ORD

The In-Flight Maintenance (IFM) Concept was 

developed to convey the manner in which S&ID w ill 

support flight operations by providing in-flight m ain -

tenance. It constitutes the definition of IFM goals 

rather than the method by which these goals w ill be 

attained. It is d ire cte d tow ard the utilization of the 

efforts going into the overall IFM p roject developm ent 

rather than the definition of these efforts.

The general concept of in-flight maintenance 

d escribed in this report m ay be applied to the lunar 

excu rsion m odule (LEM ); however, concurrent with 

the developm ent of the LEM project, interface co o r d ination m ust be continued with the associate contractor 

to insure the effectiveness of the overall sp a cecraft/ 

IFM concept.
CONTENTS

Section Page

INTRODUCTION ix

1 .0 MISSION CONSIDERATIONS 1

1.1 Initial Thrust 1

1.2 Earth Orbit 1

1.3 Translunar and Transearth 1

1.4 Lunar Orbit 1

1.5 Earth Reentry 2

2 .0 CONSTRAINTS 3

2.1 Weight 3

2.2 Mission Phase 3

2.3 Crew Constraints 3

2.4 Equipment Accessibility 3

3.0 MISSION EVENTS LOGIC 5

3.1 Mission Events Logic Explanation 5

3.1.1 Spacecraft Status - Mission Events 5

3.1.2 Indications Normal (Decision) 5

3.1.3 Criticality Criteria (Information) 5

3.1 .4 Critical (Decision) 5

3.1.5 Switch to Alternate or Redundant Mode 

(Action) 9

3.1.6 Fault Isolation Procedures

(Information) 9

3.1.7 Attempt Isolation (Decision) 9

3.1 .8 Isolate Fault (Action) 9

3.1. 9 IFM P r o ce d u re s , Technical Data,

Spares Stock (Information) 9

3.1.10 Attempt Maintenance (Decision) 9

3.1.11 Repair and/or Replace (Action) 9

3.1.12 Verification Procedures (Information) 10

3.1.13 Success (Decision) 10

4. 0 QUALITATIVE MAINTENANCE INFORMATION 11

4.1 Maintenance Decision 11

4.2 Maintenance Action 13

4.2.1 In-Flight Maintenance Analysis 13

4 .2 .2 Isolation Analysis and Task Times 14
ILLUSTRATIONS

Figure

3-1 M ission Events L ogic 7

4-1 In-Flight M aintenance Inform ation Requirem ents 12

4-2 In-Flight Maintenance Analysis 15

4 -3 Isolation and Task Tim es Analysis 17

Page
INTRODUCTION

The in clu sion of a th ree-m an crew in the A pollo com m and m odule 

allow s for the p rov ision in g of a m aintenance capability. The A pollo IFM 

w ill p rovid e a m aintenance capability with the rea liza tion that equipm ent 

reliability indicates m inim um activity in this area. A ll aspects of m a in tenance and m aintenance support are considered to assure that IFM goals w ill 

be m et. T h ese goals a re defined as the d e v e lo p m e n t of a p r o g r a m that w ill 

m o s t c o m p le t e ly augm ent re lia b ility , i . e . , en h an ce the p r o b a b ility o f 

m ission su ccess and crew safety. Studies w hich consider this augmented 

reliability versus the weight penalty im posed are being conducted continuously. System s criticality is the prim ary factor in determ ining the extent 

of maintenance support to be provided for each system . An optimum 

reliability, through continuous assessm ent of maintainability, is m andatory 

for those system s deem ed m ost critical, and m ay dictate the tra d e-off of 

maintenance support fro m those system s determ ined to be less critical.

This docum ent outlines those maintenance activities that m ay be 

re q u ire d during a ty p ica l A p o llo s p a c e c r a ft flight. It c o n s id e r s ea ch m is s io n 

phase as it affects maintenance and identifies the constraints im posed by the 

m ission m ode.

The m aintenance support item s required to a ccom plish the m aintenance 

tasks effectively are listed.

A lo g ic diagram and a w ritten d escription of the inform ation, and the 

decision and action requirem ents of the IFM p rogram also are provided.

This conceptual approach w ill be utilized by the spacecraft crew in a c c o m -

plishing IFM.

The p rim a ry m eans of im plem enting the in-flight maintenance capability 

are use of the in-flight test system , provision of displays, spares, tools, 

technical data, training, and m aterials. This w ill support the crew m em ber 

that is in the con trol position when he is m aking a m a in ten an ce- related 

decision or taking the corresponding required actions. The prim ary system 

(on-board) w ill furnish an independent detection and fault isolation capability 

to the spacecraft crew.

The ground operational support system (GOSS) w ill be con sid ered as a 

back-up or auxiliary system . GOSS w ill have the capability of supporting the 

sp a ce cra ft crew in the determ ination of alternatives fo r a m aintenance d e c i -

sion and resulting maintenance actions. It w ill also be capable of furnishing 

ground intelligence by making recom m endations to the sp a cecra ft- com m ander 

pertinent to the m ission decision.
1.0 MISSION CONSIDERATIONS

1.1 INITIAL THRUST

The need to p e rfo rm m aintenance m ay arise at any point during the 

Apollo m ission . However, the particular m ission phase, because of w ork 

load, crew availability, or environm ental conditions, m ay lim it norm al 

maintenance activities severely. A critica l in-flight period on the A pollo 

equipment w ill be during the initial thrust. In this period of m inim um 

maintenance activity by the crew , the spacecraft w ill be subjected to a high-g 

loading. During this phase, the crew safety system w ill be in control, and 

will b ecom e the determ ining fa ctor in making and supporting the m ission 

d e cis io n , i . e . , p r im a r y , altern ate, o r a b ort.

1.2 EARTH ORBIT

D u rin g ea rth o rb it and p r i o r to the tra n slu n a r in je c tio n phase, a 

relatively high crew task loading can be anticipated. Continuation of navigational sightings and other activities prep aratory to the translunar injection 

can interfere with an d/or postpone the perform an ce of maintenance due to 

simultaneous tasks occu rrin g in the sam e location within the com m and 

m odule.

1 .3 T R AN S LU N A R AND TRANS E A R TH

The translunar and transearth coast periods provide the greatest 

opportunities for m aintenance. Subsequent to the transposition of the lunar

excursion m odule (LEM), and prior to lunar orbit injection, crew task 

loading w ill be relatively sm all. Crew task loading also w ill be sm all from

the transearth injection until p rio r to earth reentry.

1.4 LUNAR ORBIT

The entire lunar orbit phase is con sid ered to be a peak-load period.

The d iv isio n of the c r e w during lunar e x p lora tion im p o s e s a v e r y sign ifican t 

constraint upon maintenance. Any m aintenance activity aboard the com m and 

module during this time m ust be of absolute necessity. Such maintenance 

activity m ay require the tra d e-off of other scheduled functions, such as those 

associated with guidance and control, and with com m unication. The time 

periods p rior to LEM separation and after rendezvous w ill be fully occupied 

with various system checks, scientific observations, and scheduled tasks.

The n e c e s s ity fo r m aintenance during these periods also m ay req u ire a tra d e -

off of other tasks.
1.5 EARTH REEN TRY

The earth r e e n tr y phase, like the a s ce n t phase, w ill be a p e r io d of 

relatively lim ited m aintenance.
2 .0 CONSTRAINTS

2.1 WEIGHT

Weight is the m ost significant constraint on the Apollo in-flight m ain tenance p r o g r a m . W eight has an in d ir e c t e ffe c t on IF M b y im p o s in g r e s t r ic t io n s 

on equipm ent design. It has a d ire ct e ffe ct on IF M by lim iting the quantity 

of on -board spares and other maintenance fa cilities.

2.2 MISSION PHASE

During thrust periods, crew m em bers w ill be restrained to their 

couches. This w ill lim it maintenance to those functions that can be a c c o m -

plished by the m anual use of switches consistent with existing g -fo r c e s .

During the period of lunar orbit and exploration, m aintenance capability 

w ill be restricted by crew nonavailability.

2.3 CREW CONSTRAINTS

Crew constraints generally can be divided into several ca tegories: 

those im posed by the adverse environment; those im posed by the hardware 

design, crew equipment and a cce sso rie s; and those im posed by psych op h ysiological load capabilities.

2 .4 EQUIPM ENT ACCESSIBILITY

P hysical placem ent of equipment within the com m and and serv ice 

module also w ill lim it, and som etim es m ay preclude, maintenance on som e 

equipment. P rim e consideration shall be given to the priority placem ent of 

critica l equipm ent to ensure that an optim um m aintenance capability is 

provided.
3.0 MISSION EVENTS LOGIC

3.1 MISSION EVENTS LOGIC E X PLA N A TIO N

M ission events logic is provided to indicate the relationship of m aintenance to m is s io n tasks. F igure 3-1 is a dia gra m of m is s io n events log ic.

An explanation of the logic portrayed by the diagram is presented in 

subsequent sub-paragraphs. The num bers below the events on the diagram 

corresp on d with the paragraph num bers.

3 .1 .1 Spacecraft Status - M ission Events

It can be discern ed from the m ission events logic that the crew is 

co n tin u ou sly m o n ito rin g d isp la y s. It is apparen t that as lon g as a ll in d ica tion s 

rem ain norm al the m ission decision would be to continue the existent m ission . 

Follow ing the m ission d ecision are three alternative actions, each supported 

by the inform ation required to fulfill the requirem ents of the selected action. 

The rem ainder of the diagram represents the inform ation decision action 

aspects of the perform a n ce of m ission tasks.

3.1.2 Indications N orm al (D ecision)

As a function of the continuous m on itorin g sp a ce cra ft status, the cre w 

is constantly making the Indications N orm al decision. This concept is 

d irected at the activity arising from an Indications N orm al No decision.

3 .1 .3 Criticality Criteria (Information)

C riticality b e co m e s a highly co m p le x outgrowth of m ission phase, 

equipment utilization, and alternate m odes of operation available. This 

criteria m ust support two decisions by the crew ; first, the degree of cr iticality at the tim e of failu re and, second, the effect of the failure on the 

m ission decision even though repair is accom plished.

3.1.4 Critical (D ecision)

A C ritical No d e cisio n has a dual m eaning; first, the failed function is 

not critical now, nor w ill it be fo r the rem ainder of the m ission and, second, 

the failed function is not critical now, allowing the maintenance task to be 

d eferred for a time. A C ritical Yes d ecision indicates that im m ediate action 

m ust be taken to elim inate the danger to the crew or to m inim ize m ission 

degradation resulting from the failed function.
F igure 3 -1 . M ission Events L ogic
3.1.5 Switch to Alternate or Redundant M ode (Action)

The availability of alternate or redundant m odes provides fo r the first 

m aintenance action. In som e ca se s these m od es w ill support an e m e rg e n c y 

function. In other cases it m ay provide support for a less cr itic a l function 

as an indirect result of that support provided for critica l functions.

3.1.6 Fault Isolation P roced u res (Information)

Isolation proced u res w ill be provided in support of every m aintenance 

action available to the crew .

3 .1 .7 Attempt Isolation (D ecision)

A No d ecision to attempt isolation m ay result from the C ritical decision 

(Paragraph 3 .1 .4 ) that the type of failure would disallow continuation of the 

p rim a ry m issio n . It also m a y be caused b y a failed function that has no 

m aintenance support. A Yes decision would allow the crew to p roceed with 

the isolation.

3.1.8 Isolate Fault (Action)

U tilizin g the in -flig h t te s t s y tsem (IFTS) m i c r o - m o n i t o r and the i s o l a -

tion p roced u res, the crew w ill isolate the fault to the failed item .

3 .1 .9 IFM P roced u res, Technical Data, Spares Stock (Inform ation)

After the failure has been isolated, pertinent p roced u res, technical 

data, and spares stock m ust be review ed to assure support of the re m o v e / 

replace task.

3 .1 .1 0 Attempt Maintenance (Decision)

An Attempt Maintenance No decision would indicate that no maintenance 

exists for this failure or that the maintenance support has been expended. A 

Yes decision would indicate that a maintenance capability exists.

3 .1 .1 1 Repair a n d /or R eplace (Action)

G enerally repair w ill be lim ited to adjustments servicin g a n d /or 

calibrations and w ill have procedural coverage. Utilizing the procedures 

provided, the repair an d/or rem ove and replace task w ill be accom plished.
3.1.12 V erification P roced u res (Information)

A fter repa ir has been accom p lish ed , the sy stem m u st be v e rifie d to 

assure that the system s function has been restored.

3.1.13 S uccess (D ecision)

A Success No d ecision would indicate that the m aintenance was not 

su ccessfu l. In this ca se the flight crew w ill con sid er m a k in g another attempt 

to repair the failed item . A Yes decision indicates that the system function 

has been restored. This com pletes the maintenance task. H owever, even 

though maintenance has been successful, the crew m ust evaluate the new 

conditions caused by expending a portion of the m aintenance support, with 

regard to the m ission decision.
4 .0 Q U A L IT A T IV E M A IN TE N A N C E IN F O R M A T IO N

4.1 M AINTENANCE DECISION

S pecific inform ation is required to support in-flight m aintenance. This 

inform ation m ust be com prehensive enough to support the flight crew when 

they are m aking m aintenance related decision s or perform in g m aintenance 

actions. F igure 4-1 illustrates som e of the requirem ents for inform ation to 

support these d ecision s. F rom this inform ation the crew can select the 

appropriate action. Follow ing are som e of the actions that m ay be selected 

individually or in com bined form .

Tolerate condition 

Switch to a redun dancy 

Switch to an alternate m ode 

R eplace 

Repair

No maintenance p ossib le

A fter the m aintenance decision has been m ade and appropriate action 

has been taken, the effect of the maintenance event m ust be evaluated. The 

flight crew w ill m ake the m ission decision predicated on the effect of the 

m aintenance event on crew safety and m ission su cce ss. Following are three 

conditions that illustrate the im pact of the m aintenance event. The m ission 

decision is m ade by indicating yes or no to each condition in sequence.

Crew safety or probability of su ccess have not been degraded 

beyond continuation of prim ary m ission .

New conditions w ill allow an alternate m ission .

A bort is required.

The m ethod of displaying this inform ation to the crew w ill be detailed 

in the In -F lig h t M a in ten a n ce Plan. One m a n n e r o f p re se n tin g a la r g e p a rt 

of the d e c is io n -m a k in g c r it e r ia is a m a in te n a n c e -o r ie n te d tim e line. The 

presentation of the planned m ission reflecting total crew activity, equipment 

utilization, m issio n events, m ission decision points, w ill point out the 

allowable m aintenance periods and the possible trad e-offs.

Another d e cis io n elem ent w ill be the task tim es associated with a 

specific m aintenance contingency. The m ission tim e available versus the 

actual task tim e requ ired m ay have a large effect on the m aintenance or 

m ission decision.
INFORM ATION REQUIRED FOR 

M AINTENANCE DECISION AND ACTION YES NO TIME

The function is critical, or tim e is critical x

The condition can be tolerated x

There is an alternate m ode or redundancy x

The m ission time

Tim e rem aining until the function b ecom es 

critical

Tim e rem aining to next decision point

X

X

X

X

X

X

There is a m aintenance capability X

There are fault isolation procedures X

There are replace or repair procedures

Maintenance task tim es under existing conditions 

(shirt sleeve, vented suit, or pressu rized suit)

T h ere is a t r a d e -o f f requ ired

X X

X

X

A tra d e-off is possible X

Maintenance was successful X

Figure 4 -1. In-Flight Maintenance Inform ation Requirem ents
4 .2 MAINTENANCE ACTION

Figures 4 -2 and 4 -3 dem onstrate the support of the m aintenance 

program m ed fo r a s p e c ific m ission . T hese fig u re s, though they are still in 

the form ative state, w ill reflect the analysis effort and the coordination of 

information for each m aintenance action available to the crew . They w ill 

furnish criteria and inform ation required for in-flight m aintenance p r o c e -

dures and flight crew training. These figures are prop osed for inclusion 

in the IFM Plan, h ow ever a separate negotiation w ill be re q u ire d as the 

effort is considered to be beyond the scope of the present contract.

Each com ponent of spacecraft system s having an in-flight m aintenance 

action possible in the fo rm of a spare, redundancy, or repair (adjustments, 

servicing, or calibrations) w ill be analyzed to determ ine the type of failure, 

system protection provided, failure indications, isolation elem ents, a c c e s s ibility, and effect on system functions. In-Flight Maintenance A nalysis, 

Figure 4-2, and Isolation and Task Tim es Analysis, Figure 4-3 , w ill be 

used to provide a tabulation of all m aintenance planned for each m ission. 

F igure 4 -2 a n alyzes ea ch item having a planned m ain ten an ce action.

Figure 4-3 groups these item s by com m on m alfunction indications and keys 

the failures to fir s t-le v e l isolation and related task tim es. Additional 

m eth ods fo r anlay s is w ill be d e v e lo p e d with r e g a r d to altern ate m o d e s of 

operation. These w ill be included in subsequent revision s of this docum ent

and detailed in the IFM Plan.

4 .2 .1 In-Flight M aintenance Analysis

An explanation of the inform ation to be entered in each colum n of the 

In-Flight Maintenance A nalysis form follow s. W here inform ation indicated 

by column heading is not applicable to an individual item, the w ord "none" 

w ill be entered.

Colum n 1 - L ist each unit for which an in-flight m aintenance capability 

exists in the form of a spare, redundancy, or repair.

Colum n 2 - L ist the type of possible failures, such as out of tolerance, 

s h o rte d , etc., op p osite the individual unit.

Column 3 - L ist the system protection, circuit breaker, relief valve, 

s e n s o r s w itc h , etc., p ro v id e d fo r the unit after it 

m alfunctions.

Column 4 - L ist the caution and warning signals that are associated 

with the item malfunction.
C olum n 5 - L ist the control and display indications that are associated 

with the item m alfunction.

Colum n 6 - L ist the IF T S /m icro -m o n ito r indication (lights) associated 

with the unit m alfunction, down to the first level of 

isolation.

C olum n 7 - L ist the stim uli requirem ents associated with the isolation 

of the m alfunction of this unit.

C olum n 8 - L ist and identify the system test points associated with 

isolating a unit m alfunction.

Colum n 9 - L ist the system test point voltage required to isolate the 

unit m alfunction.

Colum n 10 - P rovide inform ation p rim a rily oriented to units having a 

repair capability. A lso provide inform ation for rem oval 

and replacem ent of units. A cce ssib ility w ill be qualified as:

a. R eadily A ccessib le - Those units available directly

for repair or rem oval and replacem ent without d isplacem ent or rem oval of other units.

b. Secondarily A ccessib le - Those units which are

a ccessib le for m aintenance only after other units have 

been displaced or rem oved.

c. In accessible - The location of the malfunctioned item

precludes maintenance.

C olum n 11 - L ist the spacecraft function that m ay not be perform ed

because of the m alfunction and the effect that the m alfunction w ill have on other system s.

4.2.2 Isola tion A n a ly s is and T ask T im e s

Isolation Analysis and Task Tim es, Figure 4-3, w ill be prepared 

utilizing the data from the In-Flight Maintenance A nalysis. This form 

consolidates and groups the units having an in-flight maintenance planned 

capability in accordance with their com m on IFTS and/or m icro-m on itor 

malfunction indication. The inform ation provided by this form will support 

the developm ent of in-flight maintenance proced u res. An explanation of the 

inform ation to be entered in each colum n of the form follow s. Where 

information indicated by colum n heading is not applicable, the w ord "none" 

w ill be entered.
P ro v id e d 

M aintenance

Type of 

Failure

System

P rotection

Failu re Indications Isolation E lem en ts

A c ce s s ib ility

L ost Function 

and E ffect on 

Other System s R em a rk s

Item s 

Spared 

Redundant 

A djustable

Caution and 

Warning

C on trols 

and D isplays

IFTS/MicroMoni tor

Stimuli 

R equirem ents

System T est 

Points

S ystem T est 

Point Voltage

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10) ( 11) (12)

F igu re 4 -2 . In -F lig h t M aintenance A n al ysis
IF T S /M icro 

M on itor Indication

Stim uli

R equ irem en ts

P ossib le 

F ailed Units

System

P rotection

System T /P 

C onn ector and 

Pins

System T est 

Point Voltage

E ffect on System 

or System s

Isolation T ask 

T im es

R em ove, R ep la ce, 

A djust Task

V e rifica tio n 

T ask T im es

T ota l Related 

T ask T im es

S /S V /S P /S S /S V /S P /S S /S V /S P /S S/S V /S P /S

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10) ( 11)

F igure 4 -3 . Isolation and Task T im es A nalysis
C olu m n 1 - List the IFTS a n d /or m icr o -m o n ito r indications (lights) 

associated with the planned in-fligh t m aintenance.

C olu m n 2 - List the stimuli requirem ents associated with the individual indication (light).

C olu m n 3 - Group and list all p ossib le failed units associated with an 

individual indication (light) opposite the indication in 

Colum n 1.

Column 4 - Enter the system protection, i.e ., circuit b rea k ers, relief 

v a lv es, etc., r e q u ir e d to p r e v e n t s y s te m d a m ag e in event 

of failure of a unit opposite the individual unit listed in 

Column 3.

C olu m n 5 - Identify and list system test points, connectors and pins 

associated with fault isolation relative to an individual 

IFTS and/or m icro -m o n ito r indicator (light) opposite 

the indication listed in Colum n 1.

C olu m n 6 - List the system test point voltage and tolerances opposite 

the re sp e ctiv e test points in Colum n 5.

C olu m n 7 - List the inform ation relative to the effect on system or

system s as the result of a unit failure opposite the possible 

individual failed unit in Colum n 3.

C olu m n 8 - Enter inform ation concerning the gross isolation task tim e 

under shirt sleeve, vented suit, pressu re suit conditions 

related to an individual IFTS a n d /or m icro -m o n ito r 

indication.

C olum n 9 - Enter inform ation concerning the rem ove and replace 

and/or repair task tim es for an individual unit under 

shirt sleeve, vented suit, p ressu re suit conditions.

Colum n 10 - Enter information concerning the task tim es for v e r ific a -

tion after m aintenance under shirt sleeve, vented suit, or 

pressure suit conditions.

C olum n 11 - Enter inform ation that w ill reflect the "w orst ca se" task 

times for isolation, rem ove, replace, repair, and v e r ification under shirt sleeve, vented suit, or pressu re suit 

condition associated with the individual indication (light) 

on the IF T S /m icro-m on itor. "W orst ca se" constitutes 

cases whereby failure cannot be defined to one unit and all 

possible units m ust be changed to co r re ct the condition.
(
5.0 MAINTENANCE PLANNING

5.1 REQUIREMENTS

In-flight maintenance planning encom passes all considerations having 

an influence on the successful accom plish m en t of the basic maintenance 

objective. This objective is the maintenance of equipment in an operable 

condition which will ensure mission success. Major considerations of 

maintenance planning are causative factors, categories of maintenance, and 

maintenance tasks.

5.1.1 Causative Factors

The three m ajor factors that initiate maintenance requirem ents are 

known degradation of equipment due to time a n d /or usage, malfunction or 

failure, and accidental damage of equipment. Known degradation of 

equipment will be provided fo r on a scheduled, preplanned basis. The 

remaining factors will be provided for in the fo r m of a maintenance capabilityb a s e d on p r o b a b ility and c r i t i c a l i t y . S ection 6. 0, Maintenance Support is 

con cern ed with this capability. The probability of accidental damage to 

equipment can only be related to the p r e c is e design tolerances of the 

equipment and the physical location of the equipment within the s p a ce cr a ft.

5.1.2 Maintenance Categories

Maintenance is categorized as scheduled maintenance (preventive) and 

unscheduled maintenance (c o rre c tiv e ). Scheduled maintenance is that 

maintenance which is planned on the basis of known degradation of equipment 

due to time interval or usage. Unscheduled maintenance is that maintenance 

required as a result of malfunction or failure of equipment.

5.1.3 Maintenance Tasks

Scheduled maintenance tasks com prise such actions as inspection, 

servicing, adjustment, calibration, and confidence testing. In the p e r f o r m -

ance of anyone of these tasks, discrepancies or deficiencies may be revealed 

that will result in unscheduled maintenance. Unscheduled maintenance tasks 

encompass such actions as malfunction detection, fault isolation, and repair. 

Before any maintenance event is concluded, inspection and/or verification 

will be p erform ed to ensure that equipment is both operational, and safe for 

continued operation.
It can be g e n e ra lly stated that the m a j o r i t y of c o r r e c t i v e m ain ten ance 

will be directed at the e l e c t r o n ic s s y s te m s . In m ost ca se s this m aintenance 

w ill be lim ited to the is o la tio n of m a lfu n ction s and the r e p la ce m e n t of 

r e p la c e a b le units. The lim ita tio n of m a in te n an c e to r e p la c e a b le units d o e s 

not preclude the possibility of crew discretion-type fixes where damage or 

malfunction causes are readily discernible. The repair function also will 

include the adjustment, servicin g, and calibration required to return the 

system to normal operation.

The on-board capability to p e rfo rm malfunction detection, isolation, 

and system verification con sists of the trained flight crew, caution and 

warning system, controls and displays, the IFTS, the m i c r o - m o n it o r system, 

and availability of pertinent technical data. The continuous monitoring of 

system s by the flight cre w will provide inform ation relative to the i n -lim it / 

out-of-lim it condition of g ro s s system s within the spacecraft. The IFTS 

p r o v id e s the m e a n s w h e r eby the flight c r e w ca n isolate a m alfunction down to 

an individual unit or combination of units within a system. Also, it will 

provide the capability to evaluate s y s te m s degradation. In this m anner, a 

determination may be m ade that the system will still function within m is s io n 

objective requirements although a malfunction is indicated. Detailed 

p ro c e d u re s for isolation of m alfunctions within the spacecraft system s will 

be available to the flight cr e w during a m is s io n . P roced u res for verification 

of systems after corrective maintenance has been performed also will be 

available to the flight c r e w .

An augmentation of the on-board malfunction detection, isolation, and 

verification capability will be provided by GOSS. By use of telemetry, GOSS 

will monitor various points within the spacecraft systems. This will not 

only provide additional detection capability, but will provide the capability 

of sensing an impending malfunction. This additional capability is inherent 

by reason of the continuous m onitoring of system signals and the sensing of 

a degradation of a signal b efore it has exceed ed its allowable param eter. 

Through GOSS, by use of available com m unication links, scientific and 

engineering analyses and inform ation can be transmitted to the flight crew 

relative to maintenance p r o b le m s arising in the spacecraft.

Fault detection and i s o la t io n utilizing the o n -b o a r d c a p ability and GOSS 

have been discussed. However, situations may arise for which no detection 

capability is provided. Such conditions may be detected by the crew through 

sensory means. These conditions can be transmitted through GOSS to ground 

operations for analyses. In turn, ground analyses and recom m endations will 

be transmitted to the spacecraft crew for appropriate action.
The maintenance p roced u res in the manual for ground cr e w operations 

will duplicate the IFM p roced u res but will be m o r e detailed to include 

information to support the advisory or confirm ing com m ent between the 

GOSS networks and the A pollo flight c r e w relative to maintenance p r o b le m s . 

GOSS, with the aid of this manual, will be capable of supporting the s p a c e -

craft crew in making maintenance decisions and taking maintenance actions.

The prim ary maintenance functions, scheduled and unscheduled 

maintenance, will be organized so that all maintenance procedures are 

subject to tim e-line operational events and system criticality. Information 

will be readily available.
6.0 M AINTENANCE SU PPO RT

6.1 SPARES

Spares w ill be predicated on system s criticality, probability of failure, 

and weight and volum etric restraints in the com m and m odule and will only 

be provided for those system s that are a cce ssib le and m aintainable.

6.2 TOOLS

The selection of the in-flight m aintenance tools w ill be based upon 

their capability to a ccom plish the required task effectively. The possibility 

of providing a dual purpose capability and m in im izin g redundancy also 

influences the selection of this equipment. Other tool and equipment 

considerations are:

1. M inim um weight

2. Com patibility with space suit

3. O perability in a w eightless environm ent to 1 -g environm ent

4. O perability in a lo w -p r e s s u r e am bient environm ent

5. Operability in an extrem e tem perature environm ent

6. A ccom m od a tion fo r carryin g a crew m an in -fligh t m aintenance belt 

assem bly

7. Ready a ccessib ility

8. E fficien t p sy ch o m o to r utilization

9. Operability in a 100 percent oxygen environm ent

6.3 TECHNICAL DATA

Technical data in support of the m aintenance functions will be provided 

in a c o m p r e h e n s iv e and co m p a ct fo r m . It w ill be align ed to the in -flig h t 

test system and will be relevant to the on-board m aintenance capability.
6.4 EQUIPMENT

The equipment to support maintenance con sists of the i n - f light test 

system, the m icro-m on itor system (primary) and GOSS (auxiliary). A general 

description of the functions of these systems is found in Paragraph 5 .1 .3 .

6.5 MATERIEL

The m ateriel required to support maintenance w ill be identified after 

equipment replacement, repair, and test requirements have been defined 

clearly.

6.6 TRAINING

The flight crew will be trained in the recognition of system degradation, 

detection and diagnosis of system s malfunctions, and the determination of 

co r re ctiv e action. Such training will begin as part of the system m a n agement training for the guidance and navigation, com m unications and data, 

stabilization and control, and environmental control systems, and will continue 

in an integrated systems trainer. Practice will be given on this trainer in 

systems checkout and in system analysis for spacecraft malfunctions.

Main panel controls and indicators, the in-flight test system, and simulated 

system s inform ation fr o m the integrated m is s io n control center (IMCC) 

and ground operational support system (GOSS) will be used.

Training will be given concerning any removal and replacement of 

components or the obtaining of a cce s s for repair. P ractice by the flight 

c r e w in analyzing contingency situations and in determining action to be 

taken will be included in e x e r c is e s for the A pollo part task trainer (A P TT ) 

and the Apollo m ission simulator (AMS). To develop flight-crew flightcontroller coordination in these in-flight maintenance procedures and 

decisions, com bined e x e r c is e s will be p ro g r a m m e d with the operational 

support personnel (IMCC/GOSS).

6.7 PROCEDURES

The procedures will be prepared as an aid to trained personnel. The 

crew procedures will be limited by obvious weight and space availability.

Thus, only actual maintenance procedures will be displayed, i.e., confidence 

test, fault isolation, rem ove, replace, and repair (adjust, service, or 

calibrate), and verify. A m ore complete IFM procedures manual will be 

prepared for ground crew operations.
CONCLUSION

This document establishes the requirem ents for an effective in-flight 

maintenance p ro g r a m . It defines the maintenance functions and support 

categories insofar as the state of equipment design will allow.

The maintenance function, irrespective of where it is accomplished, 

is, b yn ecessity, the same. The basic difference is in the constraints and 

environm ental conditions under which the maintenance is p e r fo r m e d .

The in-flight maintenance p rogram will be predicated on an ability to 

m in im iz e the effects of constraints and environmental conditions, and on 

the logical design of equipment maintainability within these conditions. A lso, 

it will depend on an ability to predict analytically the probability of failure 

and the provisioning of redundancies, spares, and material in support of 

the required maintenance actions.

The end product will be the sum of the knowledge and efforts of all 

the scien ces in the provisioning of a com p lete and workable in-flight 

maintenance program.
GLOSSARY OF TERMS

This glossary defines term s that relate to the Apollo P rogra m in 

g en era l. It is s p e c i fi c a l l y applica ble to the A p o llo Maintenance Concept 

SID 62-702, the Apollo Maintenance Plan SID 6 2 -7 0 2 -2 , the Apollo In-Flight 

Maintenance Concept SID 63-328, and will be applicable to all subsequently 

produced maintenance planning documentation.

ACCEPTANCE The act of an authorized representative, by which the customer approves 

specific services rendered, or 

acknowledges that certain specified 

articles are in conformity with the 

requirements of the contract.

ACCESSIBILITY The re la tive e a se with which a c o m p o -

nent or an assem bly can be approached 

to be repaired, replaced, or serviced.

ACCESSORY A me c h anism or device employed to 

facilitate or increase the effective use 

of some other mechanism or piece of 

equipment.

ADJUSTMENT A m ea ns b y w h ich parts, as of a 

machine or device, are adjusted to one 

another to attain an operating standard 

peculiar to the unit.

AIRFRAME A ssem bled structural and aerodynam ic 

com ponents of a spacecraft or launch 

vehicle.

ARTICLE A unit of hardware, or any portion of 

the hardware, required by the contract,

ASSEMBLY Refer to Addendum.

ATTACHMENT A supplementary device fastened to or 

mounted on a m ach in e, apparatus, or 

other end item, so as to vary or extend 

its basic function.
BENCH MAINTENANCE 

EQUIPMENT (B M E )

Equipment required to support com ponent and s u b sy ste m te stin g . It is 

designed to provide the capability of 

isolating and defining m alfunctions.

BO ILER PLATE A sim u lated module for p red ev elop -

m ental and developm ental tests leading 

to the design of the spacecraft m odule.

BULK ITEMS Certain raw m aterials and s e m ifabricated items used in the m anufactu rin g o f an a r tic le , e .g ., b o lts , nuts, 

w ashers, hoses, clips, lubricants, 

fasteners, clam ps. T hese m aterials 

and item s include standard, c o m m e r -

cial, and m ilitary hardware, and the 

d e s ig n m a n u fa c tu r e r ' s standard parts 

falling within the sam e category.

CALIBRATE A method of com paring an instrum ent, 

d ev ice, or dial with a standard to 

determ ine its accuracy, capacity or 

graduations, or devising a scale.

CALIBRATION TESTS T ests conducted to determ ine the 

in p u t-to-ou tp u t c h a r a c t e r is t ic s o f a 

m easuring device, component, or 

assem bly; these tests are also 

conducted to verify that the ch a ra cte ristics are within specified toleran ces.

CHECKOUT A sequence of operational and ca lib ra -

tional tests needed to determ ine the 

con d ition and status of a re q u ire d 

operational function.

COMBINED SYSTEMS The physical and functional com bin ation of system s and structures yielding 

one vehicle, e.g., com m and m odule 

or serv ice module.

COMMAND MODULE The personnel and control vehicle in 

A pollo, containing com m and and 

com m unication facilities and crew 

provisions.
COMMON AND STANDARD ITEMS Certain item s of com m on and standard 

use, co m m e rcia lly available to 

industry, that adequately satisfy the 

requirem ents of the end a rticle.

COMMON HARDW ARE Certain item s having m ultiple a p p lica -

tions, e.g., nuts, bolts, screw s, 

w ashers, pins, keys, grom m ets, 

rivets, etc.

COMMON TOOLS T ools in general use that are applicable 

to a variety of m ateriel, e.g., s c r e w -

d riv ers, h am m ers, drill p resses, etc.

COMPONENT R efer to Addendum.

CONFIGURATION The physical nature of an item ; the 

physical arrangem ent of com ponents 

which com p rise a spacecraft and its 

d im en sion s.

CONSUMABLE M A TE R IA L A type of item that is expended through 

use.

CONTRACT SCHEDULE The prim e contract executed by the 

G overnm ent and the prim e contractor 

which, in addition to the term s and 

conditions thereof, includes by 

referen ce or otherwise, specification s, 

drawings, exhibits, and other data 

n ecessa ry to its proper discharge.

CONTRACTOR The in d iv id u a l(s ) or c o n c e r n (s ) who 

enters into a prim e contract with the 

Governm ent, e.g., North A m erican 

Aviation, Inc.

CONTRACTOR FURNISHED 

EQUIPMENT (C FE )

An item of equipment provided by the 

co n tr a c to r under the te rm s o f a 

contract.

CONTROLLED ENVIRONMENT An env ironm ent in which factors such 

as humidity, pressure, and tem p era -

ture are under control.
CONTROLLED PARTS P arts, assem blies, or com ponents 

which require lot or seria l number 

identification.

CORRECTIVE M AINTENANCE Maintenance p e rfo rm e d on a nonscheduled basis to re sto re equipment 

to a serviceable condition.

CRITICAL MATCHING ASSEMBLIES A ssem blies that are sp ecifica lly

m atch ed to a p a rticu la r s p a c e c r a ft, 

GSE end item , trainer, or sim ulator,

CRITICAL MATCHING PARTS Parts that are sp ecifica lly identified 

fo r use on a particular sp a cecra ft, 

GSE end item , trainer, or sim ulator,

CRITICAL MATCHING 

SPA CECRA FT SUPPORT 

HARDWARE

A sse m blies that require sp ecific fit 

to the individual vehicle.

CUSTOMER The National Aeronautics and Space 

Adm inistration (NASA).

CUSTOMER WORK ORDER (CWO) An S&ID form which authorizes the 

perform ance of certain w ork such as 

the overhaul, repair, or m odification 

of equipment. The CWO is used to 

identify and control item s during the 

overhaul, repair, or m odification 

cycle.

D ELIVERABLE EQUIPMENT All manufactured hardware that is 

com plete to the degree required, and 

ready for delivery to any scheduled 

destination.

DIAGNOSIS The process of identifying a malfunction 

to the level of component, assem bly, 

or part at which the m aintenance action 

will be taken.

DIRECT SUPPORT M ATERIEL P rop erty which m ay be incorporated 

into or attached to an end item , or 

which m ay be consum ed or expended 

in the p e r fo r m a n c e of a co n tr a c t. It 

includes raw and p rocessed m aterial,
parts, assem blies, components, and 

small tools and supplies which may be 

consumed in normal use in the perform -

ance of a contract.

DISPLAY Osci lloscopes, counters, dials, 

printers, lights, indicators, scales, 

etc., used to p r o v id e v isu a l in telligence.

END ITEM A space system or any of its principal 

systems or subsystem elements, e.g., 

launch vehicle, spacecraft, ground 

support system, propulsion engine, or 

guidance system; also, articles which 

w ill be d e liv e re d d ir e c t ly to a G o v e r n -

ment installation or provided as GFP 

to a con tractor.

ENVIRONMENT The aggregate of the conditions and 

forces that influence or affect an 

article and its perform ance throughout 

its service life.

EXPENDABLES A category of materials that are not 

accountable upon issue.

FAILURE An occurrence, produced by sudden or 

gradual deterioration, which causes 

equipment perform ance to deviate 

from specified limits.

FAILURE RATE The average number of failures 

occu rrin g per unit of tim e in a specified 

piece of equipment.

FAULT ISOLATION The process of determining the cause 

of failu re within a given system .

GOVERNMENT FURNISHED 

AERONAUTICAL EQUIPMENT 

(GFAE)

All types of aeronautical equipment 

that is supplied by the Government to 

the prime contractor or subcontractor 

for incorporation into the end item.

GOVERNMENT FURNISHED 

EQUIPMENT (GFE)

Equipment furnished to the contractor 

by the Government.
GOVERNMENT FURNISHED 

PROPERTY (GFP)

All property in the possession of, or 

acquired directly by the Government, 

and subsequently delivered or otherwise made available to the contractor.

GROUND SUPPORT EQUIPMENT 

(GSE)

All non-flight implements or devices 

required to inspect, test, adjust, 

calibrate, appraise, gage, measure, 

repair, overhaul, assemble, disassem -

ble, transport, safeguard, record, 

store, actuate, or otherwise perform 

a function in support o f the s p a c e c r a f t 

and b o ile r p la te during (1) tests at 

factory subsequent to manufacturing 

completion, (2) prelaunch, launch, 

and postlaunch operations at test sites, 

and (3) m ajor development tests such 

as house spacecraft tests, propulsion 

tests, and environmental tests. This 

includes equipment required to support 

ground support equipment as defined 

herein.

HANDBOOKS In a general sense, any small book 

containing specialized information or 

instructions.

IDENTIFICATION A te rm refe rrin g to a controlled serial 

or lot number which relates the part, 

a s s e m b l y , m o d e l , etc., to a p a rticu la r 

lot of raw material, manufacturing 

process, manufacturer, manufacturing 

date, cure date, receiving date, 

purchased lot, historical record, test 

data, calibration data, assembly 

process, matched equipment, expiration 

date.

INDIRECT SUPPORT MATERIEL Equipment, machinery, structures, 

and co n su m a b le m a te rie l, used on a 

recurring basis, for outfitting, maintaining, or operating purposes; and 

maintenance stock, tool crib supplies, 

stationery, office supplies, nonproductive hardware, fuel, bottled 

water, dry ice, etc.
IN-FLIGHT M AINTENANCE The use of available maintenance 

a c c e s s o r ie s and technical inform ation, 

in a ccord a n ce with procedu res established in the In-Flight Maintenance 

Plan to augment the probability of 

m ission su ccess and m axim ize crew 

safety.

INSPECTION The exam ination, including testing, of 

contract w ork, a rticles, and services 

to determ ine conform ance to contract 

requirem ents.

INSPECTION AGENCY A G overnm ent agency, or an agency 

acting on behalf of the Government, 

which determ ines that contracted work, 

a rticles, and serv ices conform to 

technical requ irem en ts.

INSPECTION, FINAL An inspection which m ay occur either 

at the co n tra cto r's plant or at any other 

designated location and whose purpose 

is to verify com pliance with applicable 

drawings, a n d /or specifications, and 

to insure con form an ce with req u irem ents of the contract.

INSPECTION, PRELIM IN ARY An in sp ection which is p erform ed at 

the con tra ctor's plant or plants and 

w hose purpose is to establish that the 

a rticles inspected are in conform ity 

with requ irem en ts of tire contract prior 

to shipment to the place of final in sp ection and acceptance.

INSPECTION, RECORD Final inspection and acceptance which 

are acknow ledged in a binding m anner 

by an authorized representative of the 

cu stom er.

INTEGRATED SYSTEM The physical and functional combination

of two o r m o r e v e h icle s to fo r m a 

spacecraft or launch vehicle, e . g. , 

A pollo spacecraft.
INTEGRATED SYSTEMS TEST A t est o f a v e h icle or stage with two or 

m o re system s involved.

INTERCHANGEABLE UNITS A ss em b lies, subassem blies, and 

replaceable parts that can be substituted for one another without physical 

or electrical m odification.

INTER C H A N G E A B IL IT Y A p rop erty given a part so that it m ay 

be used in m ore than one application.

INTERFACE In a rocket vehicle or other system , 

a com m on boundary between one 

com ponent and another; the junction 

points or the points within or between 

system s or subsystem s where matching 

or accom m odation must be properly 

achieved in order to make their o p e ra -

tion com patible with the successful 

operation of all other functional entities 

in the space vehicle and its ground 

support.

INTERIM R E L E A SE /

EM ERGENCY RELEASE

An authorization to proceed with 

fabrication or procurem ent of long 

lead tim e item s prior to the norm al 

approval cycle.

LAUNCH COMMIT That point in tim e when the vehicle is 

actually released.

LAUNCH ESCAPE SUBSYSTEM 

(LES)

A subsystem providing for command 

m odule recovery in case of m ission 

abort after launch and prior to orbit, 

and consisting of the launch escape 

m otor, launch escape tower, and 

tow er jettison m otor.

LOGISTICS SUPPORT The support given by an organization 

to an activity by means of which are 

furnished all, or any part of, its 

supplies, equipment maintenance, 

transportation, storage, or any other 

like service, so as to enable the 

activity to ca rry out its intended 

operation m ore expeditiously.
LOT SCHEDULE A schedule directing that an item be 

inspected, crated, and readied for 

shipment prior to the lot number date, 

and shipped in the time period assigned.

LONG LEAD TIME ITEMS Items that cannot be d e liv e r e d within a 

short time span because of their 

complexity of design, complicated 

manufacturing processes, or limited 

production or procurement cycles.

LUNAR EXCURSION MODULE 

(LEM)

The two-man vehicle which will land 

on the moon after the Apollo spacecraft 

enters lunar orbit.

MAINTAINABILITY A quality of the combined features of 

materiel design and installation that 

permits or enhances the accom plishment of maintenance by personnel of 

average skill. Materiel design param -

eters include such items as the 

operational and environmental conditions under which the maintenance 

functions will be performed. Also 

included are repairability and 

serviceability, which are functions 

of the ease with which maintenance 

activities may be performed to avert 

or correct malfunctions.

MAINTENANCE All actions required to retain materiel 

in, o r r e s t o r e it to, a s e r v ic e a b le 

condition. Its phases include servicing, 

repair, modification, overhaul, test, 

inspection, and condition determination.

MALFUNCTION A general term used to denote the 

inability of a product to give s a t is fa c -

t o r y p e r f o r m a n c e . It need not constitute 

a failure if readjustment of operator 

controls can restore an acceptable 

operating condition.

MATERIAL The substance or goods out of which 

an item is, or can be, made.
MATERIEL Items of all kinds required for the 

equipment, maintenance, operation, 

and support of activities.

MEAN REPAIR TIME (M R T) The expected mean-value of the active, 

repair/w ork time required to restore 

a s y s te m , equipment, or com ponent 

to a condition of satisfactory operation.

MODIFICATION A change in the design of an item, 

effected in order to co rre ct a design 

deficiency, to facilitate production, 

or to improve operational effectiveness

MODULE A combination of components contained 

in one package, or so arranged that 

together they are common to one 

mounting, which provides a com plete 

function or functions to a s y s t e m a n d / 

or subsystem in which it operates.

(See command module, service module, 

lunar excursion module, etc.)

N A S A 'S D E L E G A T E D 

REPRESENTATIVE

A representative of NASA stationed at 

a s u p p l i e r 's plant, or a r e p r e s e n t a t iv e 

of the inspection agency to whom 

quality assurance functions have been 

delegated.

NON- R E P A R A B L E An item designed and procured with 

the intention of disposing of it at 

failure rather than attempting repair.

OVERHAUL The rebuilding or extensive repairing 

and reconditioning of an item of equipment which has deteriorated through 

testing or extensive use.

PACKAGING The cleaning, preservation, and packing 

in unit quantities; interior cushioning 

and bracing; design and utilization of 

interior and exterior containers; 

identification of contents of inner and 

outer containers; and loading.

PART Refer to Addendum.
PECU LIAR AND NONSTANDARD 

ITEMS 

Items peculiar to the equipment design

of the con tractor, subcontractor, or

supplier for which no known com m on 

or standard item can be substituted, 

and for which design approval m ay not 

have been received.

PREVEN TIVE MAINTENANCE The inspection, care, and servicin g 

required to maintain equipment and 

fa c ilitie s in a s e r v ic e a b le condition.

PRIME CO N TRACTO R N orth A m e r ic a n A viation , Inc., S p a ce 

and Inform ation System s D ivision.

PROCEDURES The step -b y-step manner in which any 

given task is perform ed.

P R O T O T Y P E M ODEL A m odel suitable for com plete evaluation of electrica l and m echanical form , 

design, and perform ance. In its final 

form it em ploys approved parts and is 

com pletely representative of final 

equipment.

PURCHASED PARTS A rticles m anufactured by outside 

sou rces in conform ance to S&ID 

drawings and identified by S&ID part 

num bers.

RACE SYSTEM "Rapid Action Coordinated E ffort"; 

the em ergen cy requisition system of 

the prim e contractor, used to expedite 

m ateriel support requirem ents.

RECLAM ATIO N The p rocess of recoverin g required, 

serviceab le, and econ om ically 

r e p a r a b le com p on en ts a n d m a te r ia ls .

REFURBISH R es toration of an item to its original 

configuration. This m ay include 

m odification as required.

RELEASE An approval to fabricate or procu re 

item s o f m a te rie l support.
RELIABILITY The p ro b a b ility that a sy ste m , s u b -

system , com ponent, or part w ill p e r -

fo rm its required functions under 

defined conditions at a designated tim e 

and fo r a specified operating period.

R EPAIR The restora tion of a system or equipm ent to a satisfactory operating 

condition after malfunction, dam age, 

or deterioration.

REPAIRABILITY The probability that when m aintenance 

action required by equipment m a lfu n ction is taken, (1) the system w ill be 

restored to a satisfactory operating 

condition in a given period of tim e with 

a given m anpower expenditure; and (2) 

the equipment will rem ain in sa tisfa cto ry operating condition over a 

sp ecified period of tim e.

R E P L A C E A B L E SERIALIZED 

UNIT

The sm allest serialized unit that can 

be replaced without soldering.

R EPLACE M EN T The substitution of one unit for another 

functionally identical unit.

R E P L A C E A B L E PACKAGE OR 

MODULE

R ef er to Addendum.

SERVICEABILITY A function of equipment design, con -

figuration, installation, and operation 

that indicates the degree to which 

m aintenance requirem ents are 

m inim ized and sim plified.

SERVICEABLE CONDITION That condition in which the article is 

con sidered suitable for carrying out 

the purpose for which it was designed 

or authorized.

SERVICE LIFE The period of tim e or number of 

functional perform ances during which 

an item , installed in an operational 

system , will be expected to rem ain in 

a serviceab le condition.
SERVICE M ODULE The Apollo m odule containing propulsion 

equipment fuel, reaction control 

system s, and com m unications power. 

Used for thrust after b ooster sepa ration, m id -co u rs e correction , lunar 

orbit, lunar orbit ejection, and earth 

return m id cou rse correction , it is 

jettisoned prior to re-en try.

SERVICING The w ork p erform ed at regular in tervals, or under a re cog n ized system , 

to keep equipm ent o p e r a b le . It in clu d es 

cleaning, inspecting, lubricating, 

adjusting, charging, and changing of 

filters, d esicca tors, etc.

SHELF L IFE That period of tim e during which an 

item can rem ain in storage without 

having its operability affected.

SITE SU PPORT LIST A list of m ateriel item s essential to 

the su p p ort of a sch edu led p ro g ra m at 

a field s ite .

SPA C E C R A FT In the A pollo p rogram , any com ponent 

or com bination o f com ponents of the 

flight vehicle not part of the launch 

v e h ic le , e . g . , launch e s c a p e su b -

system , com m and m odule, service 

m odule, or adapter.

SPARE P A R T Any part, subassem bly, or component 

kept in re se rv e for the maintenance and 

repair of m a jor item s of equipment.

SPECIAL TOOLS Spe cially designed tools required to 

p erform a special function of m aintenance, assem bly, disassem bly, etc.

SUBASSEM BLY R ef er to Addendum.

SUBCON TRACTOR An organization, com pany, or m anufa c tu r e r that is under con tract to a 

prim e contractor, and has been 

delegated the responsibility for design, 

m an u factu re, and support of a sy stem .
SUBSYSTEM R e fe r to Addendum.

SUPPLIER A contractor or subcontractor 

actually perform ing the serv ices or 

producing the contract a rticles.

SUPPORT MANUAL A pu blication containing detailed in fo r -

m ation on technical procedu res, 

including instructions on handling, 

inspection, storage, operation, m a in -

tenance, checkout, repair, m odification, 

and overhaul of given equipment.

SYSTEM R efer to Addendum.

TEST A RTICLE An ite m that appears on a co n tr a c to r, 

subcontractor, or vendor drawing and 

w ill be utilized as a subject of a test.

TEST SITE A fa c ility establish ed at a se le cte d 

geogra p h ic location for conducting a 

sp ecific operation or test.

TEST SUPPORT P A R T A part that is required fo r a unique 

a pplication to a ccom p lish a test fu n ction, and w ill not appear on a 

con tractor, subcontractor, or supplier 

d raw in g as a functional part of that 

draw ing.

TRACE ABILITY A term that refers to the ability to 

tra ce the history, application, use 

and loca tion of an item .

T R A D E -O F F The procedu re of trading a degree of 

one attribute to gain a degree of another 

attribute, e.g., sa crificin g a d egree 

of p e rfo rm a n ce to obtain a greater 

degree of reliability under certain 

conditions, or vice versa.

UNIT R efer to Addendum.
SYSTEM Any com bination of com plete operating 

equipment, com prised of a grouping 

or interconnection of subsystem s or 

other functional entities, capable of 

perform ing a specific operational 

function or functions. Included are 

a erosp a ce system s, support system s, 

com m and and control system s, and all 

associated m ateriel. A system m ay 

a lso be a p roced u ra l entity which 

a cco m p lis h e s a s p e cific task, e.g., a 

quality system .

SUBSYSTEM A m a jo r elem ent in a s y s te m , c o m -

p rised of a single m odule or co m b in a -

tion of m odules plus independent 

com ponents that contribute to m odular 

functions, all interconnected and 

interrelated within a system and 

perform ing a specific system function.

R E P L A C E A B L E PACKAGE OR 

M ODULE

An item of equipment that m ay be 

m ounted in or rem oved fro m a s p a ce -

craft, checkout console, or the like, 

as a single package. A rep la cea b le 

package or m odule is a com bination o f 

com ponents contained in one package, 

or so arranged that together they are 

com m on to one mounting, which 

provides a com plete function or 

functions fo r a system a n d /o r su b -

system in which it operates.

GLOSSARY ADDENDUM

Note: The following definitions are 

presented in sequential ord er 

to provide an understanding of 

system relationships from the 

highest to the low est level of 

elem en ts.
COMPONENT A functional part of a sy stem , su b -

system , replaceable package or 

m odule, that is essential to an item 's 

operational com pleteness. A co m p o -

nent is a com bination of units o r parts 

that together m ay be functionally 

independent of, or an independent 

entity within, a com p lete operating 

m odule or subsystem , but which 

p rovid e a self-con tain ed function 

n e ce ssa ry for proper m odule, subsystem , a n d /o r system operation.

UNIT An assem bly, or any com bination of 

parts, subassem blies, and a ssem blies 

mounted together, n orm ally capable 

of independent operation in a variety 

of situations.

ASSEMBLY A c om bination of parts or suba ssem blies that m ay be taken apart 

without destruction, which has no 

application or use of its own, but is 

essen tial for the com p leten ess of a 

m o re com plex item with which it is 

com bined. An assem bly is an element 

of a component and perform s functions 

n ecessa ry to the operation of the 

com pon en t as a w hole.

SUBASSEMBLY A com bin ation of parts co m p risin g a 

defin able entity o f an a s s e m b ly , a 

unit, or a component, which perform s 

a function essential to the proper 

operation of the assem bly, unit, or 

com ponent.

PART The sm allest subdivision of a system ; 

an individual piece having an inherent 

functional capability, but unable to 

function without the interaction of other 

parts or fo rce s, and ordinarily not 

subject to disassem bly without 

destruction.
A -L E V E L MAINTENANCE All the activity n e ce ssa ry to service, 

adjust, and evaluate the readiness of 

a system , and which can be perform ed 

with m inim um delay. It includes 

maintenance which is within the lim its 

of equipment configuration and within 

the verification capability of GSE 

com m on to system s and integrated 

system s checkout.

B -L E V E L MAINTENANCE R eplaceable package maintenance 

a ccom plish ed by use of replaceable 

units and which is within the v e r ific a -

tion capability of GSE com m on to 

replaceable package checkout.

C -L E V E L MAINTENANCE All the m aintenance activity associated 

with the Apollo program which is 

beyond the A and B levels including 

total repair, m odification and overhaul 

capability.

Figure 3 -1 . M ission Events Logic
P rovid ed

Maintenance

Type of 

Failure

System

P rotection

Failure Indications Isolation E lem ents

A c ce ss ib ility

L ost Function 

and E ffect on 

Other System s R em arks

Items

Spared

Redundant

Adjustable

Caution and 

Warning

C ontrols 

and D isplays

IF T S /M icro -

M onitor

Stimuli

R equirem ents

System T est 

Points

System T est 

Point Voltage

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12)

Figure 4 -2 . In-F light M aintenance A nalysis
IF T S /M icro 

M onitor Indication

Stimuli

R equirem ents

P o s s ib le 

F ailed Units

System

P rotection

System T /P 

C onnector and 

Pins

System Test 

Point Voltage

E ffect on System 

or System s

Isolation Task 

T im es

Rem ove, R eplace, 

Adjust Task

V erifica tion 

Task T im es

Total Related 

Task Tim es

S/S V /S P /S S/S V /S P /S S/S V /S P /S S/S V /S P /S

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11)

F igure 4-3. Isolation and Task Tim es A nalysis