393SYS
Airport Engineering Practice
Lecture 5
Engineering & Production
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6.0
Engineering
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6.0 Engineering
Introduction
There is an on-going, open discussion in the aviation industry
about whether or not an airline needs an engineering
“department”.
At one time, airlines decided what they wanted in terms of
aircraft –
- size
- range
- operating systems
In more recent years, however, the trend has been to leave the
design and development of new aircraft to the aircraft
manufactures.
The airlines ask only that these manufacturers … “build
something we can use effectively and something we can afford.”
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6.0 Engineering
This situation has led many airlines to actually reduce their
engineering staff.
However, there are still good reasons for hiring people with
engineering skills and background.
Engineers are usually identified by some speciality – civil,
mechanical, electrical, aeronautical, transportation, nuclear, etc.
However, none of these specialisms apply directly to aviation
except aeronautical engineering.
What is really needed in a typical airline maintenance
organization are people trained as “maintenance engineers”.
This type of engineer would need to know basic engineering as
well as the technical details of the equipment used in aviation,
and in the maintenance and operation of that equipment.
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6.0 Engineering
If employed by aircraft manufacturers, these engineers would
develop maintenance programs from MSG-3 activity and also
produce the various documents identified in last week’s lecture.
However, most colleges and universities do not have courses in
maintenance engineering.
Note that the engineering department of an airline can vary
widely.
The size of the airline often determines the function provided by
the engineering department.
Ideally, an airline engineering department would have both –

engineers with a degree in engineering, and

senior licensed mechanics
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6.0 Engineering
Mechanics and Engineers
•
Mechanics know the details of systems and components on
aircraft and are experienced in the rules and regulations of
maintenance.
•
However, they tend not have had the same analytical training
as graduates of engineering.
•
Engineering graduates, on the other hand, often lack a detailed
understanding of aircraft, aircraft engines, and the multitude of
systems and components need in aircraft.
Mechanics
•
Mechanics, and technicians study the practical aspects of
aviation systems.
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They specialize in avionics systems –
electrical, electronic, communications, computers
or hydraulic systems –
hydraulics, pneumatics, flight controls and structures.
A mechanic is trained to understand how each system or unit
is supposed to work, and how it is supposed to be operated.
When there is a discrepancy, the mechanic follows standard
procedures for trouble shooting, fault isolation, and repair.
Procedures for removal, and installation, as well as for testing
the installed unit, are all standardized.
An experienced mechanic also knows what kinds of things
can go wrong – in operation, installation and in testing.
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6.0 Engineering
However, no matter how well trained a mechanic may be, and
no matter how much experience he or she might have, there
are often problems that cannot be resolved with these standard
approaches.
It might then be necessary to “dig deeper” than the standard
approaches or else call upon the engineering staff for help.
Engineers
The term engineer is usually reserved for those who have
academic degrees in some engineering field.
These people are trained differently than mechanics.
Engineers are trained in the basics of science and engineering.
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They are also trained in –
- the techniques of inductive and deductive reasoning
- statistical analysis
- problem solving, and
- systems engineering.
They will generally specialize in one particular kind of
engineering – electrical, mechanical, aeronautical, structural.
If all the usually effective procedures applied by the mechanic
fail, then the engineer must begin by looking at the problem
from a new angle.
The engineer must be capable of developing new and
innovative procedures for studying and analyzing problems,
and must understand the “big picture”.
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Homework Exercise :
Read through –
Appendix C (trouble shooting techniques), and
Appendix D (problem solving example)
One important thing – for all the engineer knows about
engineering, problem solving, and about systems and their
interactions, he or she must know about the airplanes, the
engines, and their associated systems to effectively apply this
knowledge to the solution of real airplane problems.
It therefore takes both disciplines – engineering and
maintenance – as well as both types of experts – engineers and
mechanics – for a maintenance and engineering organization
to run smoothly.
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6.0 Engineering
Engineering Department Functions
Each model of aircraft has an initial maintenance program
developed by an Industry Working Group.
The initial maintenance program is a generalized program and
must be tailored to the individual airline operator’s
requirements from the very beginning.
The manufacturer produces the FAA approved MRB report
and a maintenance planning document.
It is the responsibility of the engineering department of the
airline to package these tasks into workable units based on
factors such as –
time, space, personnel, fleet schedules, and overall
airline capabilities.
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6.0 Engineering
Aircraft Maintenance Checks (from http://en.wikipedia.org/wiki/C_Check)
Aircraft maintenance checks are periodic checks that have to
be done on all aircraft after a certain amount of time or
usage.
Airlines casually refer to these checks as one of the
following: A check, B check, C check, or D check.
A and B checks are lighter checks, while C and D are
considered heavier checks.
A Check — This is performed approximately every month.
This check is usually done overnight at an airport gate.
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The actual occurrence of this check varies by aircraft type, the
cycle count (takeoff and landing is considered an aircraft
"cycle"), or the number of hours flown since the last check.
The occurrence can be delayed by the airline if certain
predetermined conditions are met.
B Check — This is performed approximately every 3 months.
This check is also usually done overnight at an airport gate.
A similar occurrence schedule applies to the B check as to the
A check.
C Check — This is performed approximately every 12-18 months.
This maintenance check puts the aircraft out of service and
requires plenty of space - usually at a hangar at a
maintenance base.
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6.0 Engineering
The schedule of occurrence has many factors and
components as has been described, and thus varies by
aircraft category and type.
D Check — This is the heaviest check for the airplane.
This check occurs approximately every 4-5 years.
This is the check that, more or less, takes the entire airplane
apart for inspection.
This requires even more space and time than all other
checks, and must be performed at a maintenance base.
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The A and B checks are no problem for airlines because they
do not take the aircraft out of service.
Large airlines have a large fleet of aircraft - enough for the
airline to schedule people and facilities for regular “C”
checks – e.g. one airplane per week or month.
In small airlines, there are not enough airplanes or manpower
for the regular scheduling of “C” checks.
To solve this problem, the “C” check is divided into parts,
called “phases”, and each phase is conducted separately.
For example, a C check could be divided into four phases –
C1, C2, C3 and C4 – each one carried out every 3 months
until the entire C check is performed.
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Alternatively, a C check could be divided into 12 packages
with one package completed every month together with the A
check.
In both cases, the manpower utilization is more constant
throughout the year.
The airline “engineering department” is responsible for selecting
the tasks to be done, for packaging the tasks into workable
packages, and for ensuring that all task time limits are met.
The “Production, Planning and Control department” is then
responsible for scheduling the checks.
The tasks to be performed by the maintenance unit of the airline at
any of these checks can be quite detailed.
To endure that they are carried out correctly, tasks cards are issued
to the mechanics.
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Evaluation of New Aircraft for the Airline Fleet
One of the primary functions of an airline engineering
department is to evaluate new equipment for the airline.
A typical question here is – “What airplane/engine
combination should we buy ?”
The answer to this question will be influenced by –

the routes to be flown and the destination cities

the expected market share

the cost of the equipment
Another important question, however, is “What is the best
equipment to buy from the standpoint of maintenance and
engineering ?”
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There exists a trade-off here between technical priorities and
business priorities. The following example focuses only on
technical priorities from a maintenance point of view :
Example :
Boeing 767 or Airbus A330 ?
There are a number of questions to be answered in regard to
maintenance :
1. Engines

What engines are available for these models ?

Are they the same or similar to engines in the airline’s current
fleet ?
Note that is question is important because there may be a need for additional
maintenance and test facilities for these new engines.
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2. Aircraft Range

What is the range of these airplanes ?

Will the airline need to position their own personnel at
outstations or arrange for contract personnel at the site to
support maintenance.

Can existing outstation personnel handle these new airplanes ?

Can they do so with or without additional training ?
3. New Technologies

What new technology is included in these new models ?

Are the skills of the current maintenance and engineering staff
sufficient to maintain these new airplanes or will they require
additional training ?
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4. Maintenance Check Schedules

Will the maintenance check schedules for the new aircraft be
compatible with the current schedules for the existing fleet ?
5. Ground Support

Will additional ground support equipment (GSE) be needed
for these new aircraft ?

If so, what equipment ?
6. Hangers

Will the existing hangers be suitable for these airplanes ?

Will they need to be modified or will a new hanger be required
?
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6.0 Engineering
7. Aircraft Parts

What new aircraft parts, and storage for parts, will be required
at both the home base and the outstations to support the new
airplanes ?

Could this involve a considerable amount of financial
investment for parts not common to the existing fleet ?
8. Industry Experience

What is the industry experience on these new aircraft relative
to maintenance ? i.e. –

parts availability ?

parts delivery ?

failure rates ?

removal rates ?

amount of maintenance required ?
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Engineering
Question
What new aircraft would probably
require the most changes in M&E
support ?
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6.0 Engineering
Evaluation of Used Aircraft for the Airline Fleet
If the airline is considering leasing used aircraft, then other
items must be considered.
These items would include information on –

the engine type

the maintenance program and check schedule

the status of any modifications to the aircraft e.g. AD & SB
Questions to be asked would include –

Are the above the same as, similar to, or different
from your airline’s equipment ?

How will this affect training, maintenance support,
etc. ?
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What modification and configuration standards must be met
by the operator or by the lessor ?
What configuration should the airplane be in at the
termination of the lease ?
Example
An aircraft in ETOPS* configuration is leased to an airline. The
airline did not need the ETOPS capability and did not keep up with
the newer ETOPS modifications. When the aircraft was returned at
the end of the lease, the airline discovered that they were responsible
for returning the airplane to ETOPS configuration at their own
expense. Note that the condition of the aircraft at termination of the
lease should be clearly stated and understood.
*ETOPS – Extended Range Operations with Two-Engine Airplane (e.g. Boeing 777
ER)
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6.0 Engineering
Other functions of an airline engineering department include –
Evaluation of the need for new equipment in support of
aircraft added to the fleet.
The requirements for new facilities such as hangars, engine
test facilities, component shops, and storage facilities.
The issuing of engineering orders (EOs) :
Any work performed by maintenance in the form of standard
checks – A, B, C checks – is perfumed on “standing orders”
from the airline Vice President of M&E, as identified in the
maintenance section of the Ops Spec.
Any work not included in these standard checks must be
assigned by an “engineering order”.
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7.0 Production Planning and Control
Introduction
The “Production Planning and Control” (PP&C) activity
within an airline is one of the key organizations within M&E.
It is actually the “heart” of the maintenance organization.
The title implies two functions – planning and control.
Actually, PP&C has three primary functions – forecasting,
planning, and control.
Forecasting includes the estimated maintenance workload for
the long term and short term based on the existing fleet and
business plans, and on any known changes in these for the
forecast period.
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7.0 Production Planning and Control
Planning involves the scheduling of upcoming maintenance
and includes the planning and scheduling of all manpower,
parts, facilities, and time frame requirements.
Control allows adjustment of the plan and keeps (or attempts
to keep) the check on schedule.
There are several methods of adjusting the plan, including –

deferral of maintenance to a later check,

addition of personnel to complete the work,

outsourcing the work to a contractor
Feedback from a check allows PP&C to adjust the planning
effort for future checks.
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7.0 Production Planning and Control
Without planning, action would be impulsive and produce
unpredictable results.
The diagram below illustrates how work in expended on a
typical project with and without proper planning :
Performance
WORKLOAD
Planning
Unplanned
Check
Planned
Check
Start
Check
Start
Planning
TIME
End
Check28
7.0 Production Planning and Control
The preliminary planning consists of the development of a
maintenance program and its schedule.
With proper planning, once the check has begun, the work
progresses smoothly (dashed yellow line).
Without preliminary planning, the effort swells as the work
progresses, mostly due to unexpected events and delays (solid
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red line).
7.0 Production Planning and Control
Example for “C” Check

Normally, a C check requires about 4 or 5 days.

A new airline operator started to consult the maintenance
manual for the C check one week before the check was due.

Without adequate preplanning, the C check took 4 weeks to
perform !
The goals of PP&C are 
to maximize the M&E contribution to the airline

to plan and organize work prior to execution

to adjust plans and schedules to meet changing requirements
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7.0 Production Planning and Control
Production Planning
The goal of M&E is to deliver airworthy vehicles to the flight
department in time to meet the flight schedule, with all
maintenance activities completed or properly deferred.
The airline engineering department will have developed the
maintenance plan from the MRB (Maintenance Review Board
report) or Ops Specs document and divided the work into
appropriate work packages indentifying –

the tasks to be done

the intervals at which they will be done, and

the manpower requirements for each task.
The check package schedule for a typical mid-sized airline is
shown in the following table …
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7.0 Production Planning and Control
From “Aviation Maintenance Management”, H.A.Kinniston, McGraw-Hill 2004.
FH = Flight Hours, HMV = Heavy Maintenance Visit
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7.0 Production Planning and Control
PP&C must now take this engineering package and then plan,
schedule and adjust the work for each check and for each aircraft.
The estimated man hours for the various checks and aircraft for the
same mid-sized airline are as follows :
From
“Aviation
Maintenance
Management”,
H.A.Kinniston
, McGrawHill 2004.
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7.0 Production Planning and Control
Daily, 48-hour and transit checks are usually standardized and
require little or no effort on the part of PP&C other than
scheduling.
All “A” checks and higher are planned, scheduled, and
coordinated by PP&C and their content varies from check to
check.
These activities are more involved than the daily, 48-hour and
transit checks, so the panning is started well in advance of the
actual check.
For “A” checks, planning begins 1 to 2 weeks prior to the
scheduled check.
For “C” checks, planning begins about 4 weeks in advance.
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7.0 Production Planning and Control
Maintenance Tasks for “Less-than-A-Check” Intervals
Certain items in the MRB report must be checked daily, biweekly, and weekly.
The scheduling is the responsibility of PP&C.
These checks can be scheduled overnight, or at certain turnaround times, or may be included in the “A” checks.
This is up to the airline and is usually determined by local
conditions and man-power availability.
Airlines can experience problems if they defer these tasks day
after day due to heavy work loads.
The deadline for completion gets nearer and nearer and,
finally, the airline has to take the aircraft out of service for
several hours to get the work done without exceeding FAA
time limits. These delays can be costly.
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7.0 Production Planning and Control
Multiple Checks
Some MRB items are done at intervals like every other; every third check.
This is true for A & C checks. That means that different “A” check have different
task set and require different amount of time depending on where that “A” check is
in the maintenance cycle.
The following table shows a typical aircraft “A” check and “C” check schedule :
From “Aviation Maintenance Management”, H.A.Kinniston, McGraw-Hill 2004.
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7.0 Production Planning and Control
Every “C” check includes all the “A” check items.
The “C” check items can also be scheduled for longer
intervals.
A chart similar to the one on the previous slide can be drawn
for multiple “C” checks.
Phased Checks
These are different from multiple checks.
An “A” check may be split into two phases, each one
performed on successive nights to minimize maintenance
crew needs and down time.
The right side of an aircraft might be done on the first phase
(called an “A1” check and the left side on the second phase
(the “A2” check).
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7.0 Production, Planning and Control
A “C” check may be broken down into four parts (C1, C2, C3,
and C4) and performed every 3 months or so depending on the
full “C” check cycle.
The “C” check can also be divided into 12 parts, with one part
being completed each month (C1, C2, … C12).
The table on the following slide shows a typical airline estimate
for the man-hours planned for a “C: check on the Airbus A300B4.
The check will consist of three categories of task – routine, variable
routine, and non-routine.
Routine tasks are identified in the MRB report document.
Variable routine tasks vary from one check to another and from one
aircraft to another.
Nonroutine tasks are generated by the accomplishment of other,
routine tasks.
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7.0 Production Planning and Control
From “Aviation Maintenance Management”, H.A.Kinniston, McGraw-Hill 2004.
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Summary
Summary
Engineering

Introduction

Mechanics and Engineers

Engineering Department Functions

Aircraft Maintenance Checks

Evaluation of New and Used Aircraft for the Airline Fleet
Production Planning and Control

Introduction

Production Planning

Maintenance Tasks for “Less-than-A-Check” Intervals

Multiple Checks

Phased Checks
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What you need to know for the exam !

Why do all airlines require a maintenance department, regardless of whether or
not they actually do the maintenance themselves ?

Explain the difference between mechanics and engineers in terms of their role
in aircraft maintenance.

What is the MRB report, who is responsible for producing it and what are
airlines required to do with it ?

Explain, briefly, what is meant be aircraft A, B, C and D checks.

What approach is adopted by small airlines in conducting “C” checks ?

What issues need to be addressed in evaluating new (used) aircraft for an
airline fleet ?

Explain, briefly, the function of Production Planning and Control department
within an airline ?

What is the relationship between Engineering and PP&C in an airline ?

Explain the purpose of Production Planning.

Explain “Multiple Checks” and “Phased Checks” and also the difference
between the two.
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