Service Bulletin No: 21-012 Ref No: 165

Modification No: EC-14-0359 ATA Chapter: 21

SERVICE BULLETIN

PILATUS AIRCRAFT LTD. STANS, SWITZERLAND

Service Bulletin No: 21-012 Date: Nov 04/14

Rev. No. Date: Page 1 of 10

AIR CONDITIONING - COOLING

INSTALL A COVER ASSEMBLY TO THE COMPRESSOR TO PROTECT TO THE ENGINE OIL HOSE 

1. Planning Information

A. Effectivity

MSN 101 thru 607, Pre Service Bulletin 21-006.

B. Concurrent Requirements

None.

C. Reason

(1) Problem

On PC-7 aircraft that are pre Service Bulletin 21-006, the oil cooler inlet-hose is routed 

close to the air conditioning compressor clutch plate. If a spring on the compressor clutch 

plate shears, the oil hose can become damaged and the engine oil can spill into the 

engine bay.

(2) Solution

Install a cover assy which will be mounted on the attachment points of the compressor. 

This will provide a barrier between the compressor clutch plate and the oil hose. The 

shield can be mounted on the compressor support bracket with the current bolts.

D. Description

This Service Bulletin gives the data and instructions necessary to install a cover assy (between 

the compressor clutch plate and the oil hose) to protect the oil hose.

E. Compliance

Mandatory.

Accomplishment required not later than 120 days after the effective date of this Service Bulletin.

F. Approval

The technical content of this Service Bulletin is approved under the authority of Letter of DOA 

Acceptance ref. FOCA.21J.002.

Pilatus advises Operators/Owners to check with their designated Airworthiness Authorities for 

any changes, local regulations or sanctions that may affect the embodiment of this Service 

Bulletin.
Service Bulletin No: 21-012 Date: Nov 04/14

Rev. No. Date: Page 2 of 10

SERVICE BULLETIN

G. Copyright Information

© Pilatus Aircraft Ltd. This document contains proprietary information that is protected by 

copyright. All rights are reserved. No part of this document may be copied, reproduced or 

translated to other languages without the prior written consent of Pilatus Aircraft Ltd.

H. Manpower 

NOTE : Man-hours figures do not include the time required to cure sealants, paints and 

adhesives.

I. Weight and Balance

(1) Weight Change

Negligible.

(2) Moment Change

Negligible.

J. Electrical Load Data

Not changed.

K. Software

Not changed.

L. References

Aircraft Maintenance Manual (AMM): 12-00-00, 20-31-00, 21-50-00.

M. Publications Affected

Aircraft Parts Catalog (IPC): 21-10-01.

N. Interchangeability of Parts

Not applicable.

Total Total

Preparation 1.0 1.0

Installation of the Cover Assy 0.5 0.5

Close up 1.5

Close up (including, if necessary, to evacuate and charge 

the cooling system)

4.5

TOTAL MAN-HOURS 3.0 6.0
SERVICE BULLETIN

Service Bulletin No: 21-012 Date: Nov 04/14

Rev. No. Date: Page 3 of 10

2. Material Information

Operators who require further information on Price and Availability should contact their 

Customer Liaison Manager at:

Pilatus Aircraft Ltd,

6371 Stans,

Switzerland.

Operators are requested to advise Pilatus Aircraft Ltd. of the Manufacturer’s Serial Number 

(MSN), the flying hours and landings of aircraft which are allocated for this Service Bulletin using 

the Service Bulletin Evaluation Form.

A. Material - Price and Availability 

B. Material Necessary for Each Aircraft

(1) Material to be Procured

Modification Kit No. 500.50.07.045 has these parts: 

NOTE: Part Numbers given in this Service Bulletin are correct at the time of approval. 

Pilatus Aircraft Ltd. reserves the right to change the part numbers as necessary. 

Part numbers of items delivered with the Modification Kit are correct when the kit 

is dispatched. This could lead to differences between those part numbers quoted 

in this Service Bulletin and the Modification Kit if parts are superseded. 

Operators are requested to check the IPC for delivered parts which differ from 

those listed in the Service Bulletin Materials Kit List.

Modification Kit Number Price Availability

500.50.07.045 Contact address above Contact address above

NEW PART NO. DESCRIPTION OLD PART NO. QTY DISP. 

CODE

FIG ITEM

938.75.11.311 WASHER 1 - 1 1

938.77.11.110 WASHER 1 - 1 5

521.50.07.022 COVER ASSY 1 - 1 11

971.32.51.105 CABLE TIE 2 - 1 12
Service Bulletin No: 21-012 Date: Nov 04/14

Rev. No. Date: Page 4 of 10

SERVICE BULLETIN

(2) Operator Supplied Materials (Ref. AMM, 20-31-00): 

C. Material Necessary for Each Spare

Not applicable.

D. Re-identified Parts

None.

E. Tooling - Cost and Availability

Not applicable.

MATERIAL NO. DESCRIPTION QTY REMARKS

P01-010 SOLVENT A/R Or equivalent

P02-013 ABRASIVE CLOTH A/R Or equivalent

P02-014 ABRASIVE CLOTH A/R Or equivalent

P02-031 ABSORBENT PAPER A/R Or equivalent

P07-021 ALODINE 1132 A/R Or equivalent

P10-013 DINITROL AV40 A/R Or equivalent
SERVICE BULLETIN

Service Bulletin No: 21-012 Date: Nov 04/14

Rev. No. Date: Page 5 of 10

3. Accomplishment Instructions

WARNING: BEFORE YOU DO WORK ON THE COOLING SYSTEM, MAKE SURE YOU OBEY THE 

SAFETY PRECAUTIONS LISTED IN THE AMM, 21-50-00, PAGE BLOCK 201).

WARNING: BE CAREFUL WHEN YOU USE THE CONSUMABLE MATERIALS. OBEY THE 

MANUFACTURERS HEALTH AND SAFETY INSTRUCTIONS.

NOTE: Obey the manufacturer's instructions when you mix and use the consumable materials.

A. Preparation

(1) Open and install a safety clip to the circuit breaker:

COOLING SYSTEM.

(2) Open the access panel ENG 3L (Ref. AMM, 12-00-00, Page Block 1).

B. Installation of the Cover Assy (Ref. Fig. 1)

(1) Remove, and keep, the bolt (3), the spring washer (2) and, if installed, the washer (1).

(2) Remove, and keep, the nut (9), the washer (10), the ground lead (7) and the screw (6).

NOTE: On Pre Service Bulletin installations, the ground lead (7) is installed on the aft 

face of the plate (4) (opposite to that shown in Figure 1). The washer (5) is not 

installed.

(3) Prepare the plate (4) for the new position of the ground lead (7):

(a) Make a circular mark on the forward face of the plate around the lower attachment 

hole, approximately 10 mm from the edge of the hole.

(b) Use the abrasive cloth (Material No. P02-013 and P02-014) to remove the paint and 

primer to get bare metal in the area you marked.

(c) Clean the bare metal area with the solvent (Material No. P01-010) and absorbent 

paper (Material No. P02-031).

(d) Apply layers of the Alodine 1132 (Material No. P07-021) on the bare metal area and 

allow to dry.

(4) Put the cable ties (12) through the holes in the cover assy (11) (P/N 521.50.07.022).

(5) Put the cover assy (11) (P/N 521.50.07.022) in position on the aft face of the plate (4) and 

around the pulleys (8).

(6) Put the spring washer (2) and, if necessary, the new washer (1) (P/N 938.75.11.311) on 

the bolt (3).

(7) Loosely install the bolt (3), complete with the spring washer (2) and the washer (1).

(8) Put the ground lead (7) and the washer (5) (P/N 938.77.11.110) on the screw (6).

NOTE: On Post Service Bulletin installations, the ground lead (7) is installed on the 

forward face of the plate (4) (as shown in Figure 1).
Service Bulletin No: 21-012 Date: Nov 04/14

Rev. No. Date: Page 6 of 10

SERVICE BULLETIN

(9) Install the screw (6), complete with the ground lead (7) and the washer (5) (P/N 

938.77.11.110), the washer (10) and the nut (9).

(10) Tighten the bolt (3).

(11) Make sure there is no interference between the pulleys (8) and the new cover assy (11) 

(P/N 521.50.07.022).

(12) Use the cable ties (12) to attach the cables (13) to the cover assy (11) (P/N 

521.50.07.022).

(13) Apply a layer of Dinitrol AV40 (Material No. P10-013) to completely cover:

• The screw (6)

• The washer (5) (P/N 938.77.11.110)

• The ground lead (7)

• The bare metal of the plate (4)

• The washer (10)

• The nut (9).

C. Job Close-Up

(1) Remove all equipment, materials and tools from the work area. Make sure that the work 

area is clean.

(2) Close the access panel ENG 3L (Ref. AMM, 12-00-00, Page Block 1).

(3) Remove the safety clip and close the circuit breaker:

COOLING SYSTEM.

(4) If necessary, evacuate and charge the cooling system (Ref. AMM, 21-50-00, Page Block 

301).

(5) Do a test of the cooling system (Ref. AMM, 21-50-00, Page Block 501). During the system 

test, set the COOL switch to ON and OFF approximately 15 times at three second 

intervals.

D. Documentation

(1) Make an entry in the Aircraft Logbook that this Service Bulletin has been incorporated.

(2) Use the Service Bulletin Evaluation Sheet and report your results and the serial number of 

the aircraft to Pilatus.
SERVICE BULLETIN

Service Bulletin No: 21-012 Date: Nov 04/14

Rev. No. Date: Page 7 of 10

 Installation of the Cover Assy

Figure 1

1

A

A

2

3

4

5

7

8

9 10 11

6

12

13

12
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SERVICE BULLETIN

Service Bulletin No: 21-012 Date: Nov 04/14

Rev. No. Date: Page 9 of 10

SERVICE BULLETIN EVALUATION SHEET FOR SB No. 21-012

Title

Air Conditioning - Cooling

Install a Cover Assembly to the Compressor to Protect to the 

Engine Oil Hose 

Customer

Service Center

EMBODIMENT REPORTING

This SB has been embodied: On the entire fleet

Only partially

Provide embodiment details per aircraft (use additional copies of this table, if necessary)

MSN Flying Hours MSN Flying Hours

Additional embodiment comments/findings

EDITORIAL COMMENTS

 (procedure, kit quality, suggested improvements, etc.)

Name Signature Date

Please complete and forward this form to:

Pilatus Aircraft LTD,

Customer Technical Support (MCC),

P.O. BOX 992,

6371 Stans, Switzerland

Fax: +41 (0)41 619 6773

Email: Techsupport@pilatus-aircraft.com

SERVICE BULLETIN EVALUATION SHEET
Service Bulletin No: 21-012 Date: Nov 04/14

Rev. No. Date: Page 10 of 10

SERVICE BULLETIN

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