Initial Provisioning (Spare parts Management)

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AIRCRAFT MAINTENANCE

Section 6

“Plan your work and then work your plan.”

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Production Planning and Control

Production Planning and ControlProduction planning and control (PP&C) is one

of the key organizations within M&E. It is the heart of the maintenance organization.

The PP&C organization is primarily responsible for planning and scheduling all aircraft maintenance activity within the airline.

Actually PP&C has three primarily functions: forecasting, planning and control.

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Forecasting

Forecasting activities include the estimated maintenance workload for the long term and the short term based on the existing fleet and business plans and on any known changes in these for the forecast period.

Forecasting is concerned with the future workload of the M&E organization. It must take into account the routine maintenance requirements as well as all planned changes in the future operations relative to maintenance.

Any changes in fleet size and make up, changes in route structure, and changes in facilities, manpower, and skill requirements must be tracked.

Future plans must also accommodate aging and replacement of equipment, adding new equipment, and the planned incorporation of ADs and SBs.

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Forecasting

Forecasts are usually made for the long and short term but often an intermediate term forecast is also made.

- Short-term forecasts are more detailed and usually

cover 1-2 years. These forecasts contain more definitive

plans with attention to actual manpower and budget

numbers. - Long-term. Larger airlines may also develop intermediate

forecasts for periods of 2 to 5 years.

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Production Planning & ControlsPlanning involves the scheduling of upcoming

maintenance and includes the planning and scheduling of all manpower, parts, facilities, and time frame requirements for such maintenance: less than “A” check items, daily checks, 48-hour checks, transit checks, and letter checks (A, B, C, etc.).

These plans would include incorporation of SBs, SLs, and ADs as well as other modifications deemed necessary by the airline.

Coordination with flight operations and with ground handling and support activities is also included in the planning effort.

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Feedback for planning

- What the planners need to know to adjust future plans are the following:1. The amount of time required to perform each task2. The amount of time lost in waiting for delivery of parts

and supplies3. The down time for unusual circumstances4. The additional time required for non-routine findings5. The variation in manpower availability6. Lost time due to parts robbing from other jobs (or from

the aircraft in check)

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The need of Spares

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An airline sells speed safety and regularityAn aircraft is a highly complex deviceIt is expected to operate at 99% + Technical

regularityIt is expected to fly up to 15 hours per day and

sometimes even moreIt is expected to fly 4000 hours per yearWithout a readily available stock of spares

these targets will not be metA two hours delay costs around 4000$. A

cancellation around 16,000$

Plus The damage to a company’s image

Reliability / Consumption Data

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MTBF : Mean Time Between Failure

MTBUR : Mean Time Between Unscheduled removals

TAT : Turn Around Time

[Time in days from equipment failure to it being available, serviceable again to the airline]

MTBF = Number of Hard failures

Number of equipment hours flown

MTBUR = Number of removals of equipment considered faulty Number of equipment hours flown

In a given Fleet

Sources of Spares

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From the aircraft manufacturerOne stop shoppingGood pressure on suppliersReduced administration loadEquipment matches the aircraftMake up charged

From the equipment supplierNegotiate special dealsNo mark upHeavy administration

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From second hand dealersLow pricesImmediate availabilityDoubts on historyMay need early overhaul

Pooling SchemesReduced capital investmentPay from cash flowPossible availability problems

Sources of Spares

Different types of Spares

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No-Go Essential to be operational for the aircraft to

be dispatched

Go-If Can be failed and the aircraft allowed to be

dispatched if some reservations are met

Go Can be failed and the aircraft can be dispatched.

To be changed or repaired at the first

(sometimes defined) opportunity

Typical Figures for Spares Potential

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A320 Example :

Number of removable part numbers25000

Number of structure part numbers 15000Number of standard part numbers 9000Number of equipment part numbers

1100

How can Initial ProvisioningCost be reduced?

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Lease spares Join pool scheme as a user only Purchase only as need arises Spares included in a larger support scheme from a third

part or airline service provider

CASH FLOW

Pooling

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Basic principle is to take advantage of scale effects. The larger the fleet the smaller the expenditure per aircraft on spares becomes. Members contribute spares or capital

However at about 20 aircraft the effect begin to become less noticeable

Demand is random and so the pool may empty a particular time

Not all prospective candidates are welcome in a pool

Costs may be high. 1/365 of book value per day is common and this may be higher for longer leases by occasional users

Repair costs are to be added

Lease and Exchange Schemes

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Spares are leased against a fixed percentage of their cost in much the same way as are aircraft. However, because of the higher risk and administration load, required rates are higher. -1.6% - 1.7% - per month is normal

At the end of the lease the equipment does not belong to the airline

Instead of repairing and item a serviceable unit is given in exchange

The exchange unit may be newer or older than that for which it is exchanged. There may be cash/cost adjustments

Maybe difficult in some areas of the world due to extra customs charges

Lease Schemes

Exchange Schemes

Package Schemes

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The major players – big airlines, airframe manufactures and engine companies are looking at spares repair and leasing packages. A “spares by the hour” approach

User would pay a fixed or pre-determinable fee ensuring replacement of failed items by serviceable ones

Main Advantage areReduced capital expenditureEasier budgetingReduced administrationReduced risk from random need for sparesSometimes attached to an overall support scheme,

particularly by airlines – “Big Brother”

Non availability of Spares

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Loss of serviceExtension of overhaul downtimesCost of spares loaned or purchased

hurriedlyLease of aircraftDamage to company image

A.O.G. System

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Literally it means the aircraft cannot operate because of damage or an equipment failure

Often used when the aircraft is close to such a condition

The manufacturer is expected to react within a minimum period of time to advise of and take action

It costs much more than normal shippingIt occasionally carries a surchargeIts abuse costs the industry a lot of money – The

innocent pay for the guilty

A.O.G. Aircraft On Ground

Parts and Materials InformationApproved parts is one that meets approved

design data applicable to the part and having been manufactured and subsequently maintained in accordance with the requirements of the State of Design, Manufacture or Registry, as applicable.

Standard parts are approved parts conforming to national or industry accepted standard.

Parts and material acceptance: The process of evaluating parts and material for acceptance involves establishing that the part/material is authentic, conforms to the relevant type design, customers order, physical state and accompanying release documents.

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Parts and Materials InformationUnapproved Parts: These are parts that

do not meet the criteria, they also include parts improperly returned to service.

Original Equipment Manufacturer (OEM) parts

OEMs are the primary source of approved parts

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Parts Manufacturer Approval (PMA)Parts Manufacturer Approval (PMA) is a

combined design and production approval for modification and replacement articles. It allows a manufacturer to produce and sell these articles for installation on type certificated products.

FAA Orders 8110.42 and 8120.2 prescribe the approval procedures for FAA personnel and guides applicants in the approval process.

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OEM vs PMA

Compatibility, Price and AvailabilityCustomer BasesThe AirlinesThe Cargo CarriersThe MilitaryThe Commercial and Business OperatorsThe GA Community

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OEM vs PMA

The Battle Wages OnThe war between the PMAs and the OEMs is

a heated one. And even though there seems to be revenue enough to go around today, more contenders and products enter the market every year, causing everyone to worry about their own market share. Ironically, there are even some cases of combatants defecting.

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Approved technical stores

Approved technical stores comprise of Quarantine and Bonded stores.

Quarantine stores Quarantine Store - Incoming: Provide

storage for incoming material and parts. Quarantine store – Unserviceable: Provide

storage for parts and material awaiting investigation and dispatch for repair.

Bonded stores Bonded store: Provide storage of parts and

material that have been proved authentic.

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Approved Technical Stores The approved technical stores will be

contained in the user manual which could be a stand alone document or part of the GMM/TPPM/MPM / MCM and will address the following:a ) Quarantine and Bonded stores;

b) Incoming and outgoing inspections;

c) Shelf/storage life;

d) Records control;

e) Parts identification ( markings);

f) Storage of instruments, tools, rubber items etc;

g) Segregation of parts and materials in the bonded store;

h) Storage facility;

i) Special storage. 04/19/2326

Parts and Material Authenticity EvaluationInvolves establishing that the parts and material

conforms to approved design specifications, and have retained the essential properties assumed in the design as qualified by the supporting documents.

Information on the supporting documents shall include the following: a) The authority under which they are issued; b) Reference identification for the purposes of traceability; c) Name, address and approval reference of the issuing organization;

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Parts and Material Authenticity Evaluation

d) Work order, contract or invoice number; e) Quantity, description, part numbers and, if applicable, serial numbers of the parts; f) Relevant information concerning any shelf life limitations, special storage condition requirements, compliance or non-compliance with any airworthiness directives, etc; g) The signature and approval reference of the person issuing the document; and h) Whether the part is new or used.

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Materialsand

PartsManageme

nt

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Tags

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More Details

More information please going through “Aviation Maintenance Management, chapter 16 Materiel Support” by Harry A. Kinnison, Ph.D.

or Any questions please contact

samrit.aero@gmail.com

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