5,0

Produce

Prime

Mission

Equipment

9,0

Operate

the System

In User

Environment

Produce

Elements

of Support

Maintain

the System

(as Required)

Example: First-Level Diagram

i

\

9.0

Ref: Operate the System

in User Environment

9.7

Prepare Aircraft for Flight

-

Taxi Aircraft Takeoff

Takeoff

—

Cruise Out to Mission Site

-

Conduct Mission

—

Cruise Sack to Base

—

Land at Home

-

Perform Aircraft Checkout

Prepare

Aircraft for Standby

9.4

9.3

9.5

9.6

9,

9,9

9.2

^ ^ i ^^:

Example: Second-Level Diagram I I

Conduct Mission

9.6.1

Check

Radar Subsystem

9.6,2

Search for

9.6.3

Track

Target

I Example: Maintenance Flow (Partial)

10,1.2

10.1.1

Remove

Unit A

Isolate Fault j to Unit A \ :

10.2-1

10-2.2

Isolate Fault to Unit B				Remove Unit B
	10.3.1				10-3-2
	Isolate Fault				Remove
	toUnii C				Unit C

Figure 5-2. Series of flow diagrams (evolutionary development).

132

Functional Analysis and Requirements Allocation Chap. 5

Ref: 5.4 Perform Range Measurements

-i

••*

* \

Reference: Figure 5-3

Ref: 5,0

Acquire Range

Information

Ref: 5.4.1 Detect and Decode Range information

Ref: 5.4.2

Measure Time Delay

Between Transmitted

and Reply Signals

etc,

etc.

%;

*•?'

.- Ј,v:

•i,

'tit

i •-,;?4>.

*

Figure 5-4. Range information functional-flow diagram.

C. Maintenance Functions

Once operational functions are defined, it is appropriate to continue with the system definition process by developing maintenance functions. Referring to Figure 5-2, there are expected performance requirements associated with each block (signal level, toler­ances, unit dimensions, level of activity quality, speed of task completion), A check of the applicable function will indicate either a go or a no-go decision, A go decision leads to the next operational function. A no-go indication (constituting a symptom of mal­function) provides a starting point for the development of detailed maintenance func­tional flow diagrams- The transitional process, in evolving from operational functional flows to maintenance functional flows, is shown in block 9.6.1 of Figure 5-2. These interfaces are also illustrated in Figure 5-5, which shows a simplified lawn mowing capability. Figure 5-6 presents another example of a maintenance functional flow dia­gram, as it evolves from the operational flow in Figure 5-3.

Maintenance functions identified at this point should reflect the effectiveness and supportability factors specified at the system level, as well as the availability of logistics resources. In some instances it may be possible to expand top-level functional flows in a manner similar to the example presented in Figure 5-4. In most cases, however, only an estimate of first-level maintenance functions can be made, since the availability of preliminary data is limited. Maintenance functional flows can and should also be pre­pared for preventive maintenance, transportation and handling functions, support equip­ment corrective maintenance, servicing, inspections, and so on. The maintenance func­tional flows that are developed are used to update the system maintenance concept in terms of the functions performed by level, repair policies, and preliminary equipment packaging schemes (discussed in Chapter 4). The maintenance concept/functional flow development process is iterative, and is continued throughout the early system definition process.