CUSTOMER BULLETIN

SUBJECT

NUMBER 121 

FLIGHT CONTROLS (ATA 27) 

INSPECTION - FLIGHT CONTROL SURFACES 

PAINT THICKNESS 

MARCH 23, 2012 
Gulfstream G550 Customer Bulletin No. 121 

“March 23, 2012” 

Page 1 of 8 

Flight Controls (ATA 27), Inspection – Flight Control Surfaces Paint Thickness

I. Planning Information:

A. Effectivity: 

Aircraft serial numbers 5038, 5079, 5223, 5227, 5237, 5240, 5245, 5246, 5252, 5258, 

5261, 5265, 5267, 5283, 5290, 5293, 5294, 5302, 5307, 5311, 5318 and 5320 

B. Reason: 

Gulfstream has determined through routine records review that, during application, the 

flight control surfaces paint thickness may not have been properly documented on a 

number of aircraft. Excessive paint thickness will affect the balance moment of the flight 

control surface and may result in reduced control surface flutter margin. 

C. Description: 

This customer bulletin is divided into two parts: 

Part I of this customer bulletin is a one-time action to inspect the flight control surface 

paint thickness on identified aircraft and to incorporate Airplane Flight Manual 

Supplement (AFMS) G550-2012-01 or EASA-G550-2012-01, as applicable, imposing 

altitude restrictions for any aircraft found to have excessive paint. 

Part II of this customer bulletin is a one-time action to correct any excessive paint 

thickness conditions identified by the Part I inspection. This part will also remove the 

AFMS altitude restrictions upon completion of corrective action. 

Note: All references in this document are intended to be inclusive of any amendments 

or revisions unless otherwise stated. 

D. Compliance: 

Compliance with Part I of this customer bulletin is required within 90 days of the release 

date. 

Compliance with Part II of this customer bulletin, if necessary, is required within 12 

months from compliance with Part I of this customer bulletin. 

This customer bulletin is a managed program and should be accomplished at a 

Gulfstream Aerospace Authorized Warranty Repair Facility. Compliance with this 

customer bulletin must be coordinated through Gulfstream Scheduling at 800-810-GULF 

(4853), or 912-965-4178. If not scheduled, down times could increase significantly. 

E. Approval: 

This customer bulletin has been FAA approved as this issue is the subject of FAA 

Airworthiness action. It does not contain any modification information nor revise the 

approved configuration and as such does not require any other regulatory approval. 
Gulfstream G550 Customer Bulletin No. 121 

“March 23, 2012” 

Page 2 of 8 

F. Manpower: 

Inspection (Part I) - 4.5 man-hours 

Note: Listed man-hours are for Part I inspection only. Due to the potential variation of 

work requirements to correct any deficiencies, labor coverage for Part II 

corrective action must be charged on a separate work order and submitted for 

warranty consideration. 

G. Material: 

None 

H. References: 

 G550 Aircraft Maintenance Manual (AMM), Chapters 20 and 27 

 G550 Airplane Flight Manual (AFM) 

 G550 Airplane Flight Manual Supplement (AFMS) G550-2012-01 (attached) 

 G550 Airplane Flight Manual Supplement (AFMS) EASA-G550-2012-01 (attached) 

 Gulfstream Aerospace Material Process Specification (GAMPS) 4000, revision F 

I. Tooling/Equipment: 

Ultrasonic Coating Thickness Gage, Positector 200 series or equivalent

J. Opportunity for No-Charge Compliance:

Labor and material will be provided at no charge if this customer bulletin is accomplished 

within the recommended compliance time, as stated in this document, at a Gulfstream 

G550 Authorized Warranty Repair Facility. 

Note: Additional labor hours incurred due to aircraft configuration or mechanical 

difficulties must be charged on a separate work order and submitted for warranty 

consideration. 

Note: Labor and materials for corrective action (Part II), if necessary, must be charged 

on a separate work order and submitted for warranty consideration. 

K. Weight and Balance: 

N/A 

Part I

II. Accomplishment Instructions:

CAUTION: PROTECT WIRE BUNDLES, CONNECTORS AND SURROUNDING 

STRUCTURE DURING ANY MAINTENANCE PROCEDURE FROM SHAVINGS, 

DEBRIS AND CONTAMINATION. MAINTAIN A PROPERLY CLEANED WORK 

AREA THROUGHOUT THE PROCEDURE TO ENSURE THE INTEGRITY OF 

THE AFFECTED COMPONENT / SYSTEM. VISUALLY INSPECT WORK AREA 

USING ADDITIONAL LIGHT AS NECESSARY TO VERIFY ABSENCE OF ANY 

DEBRIS PRIOR TO COMPLETION OF PROCEDURE. FAILURE TO COMPLY 

MAY RESULT IN DAMAGE TO COMPONENTS AND / OR SYSTEMS.
Gulfstream G550 Customer Bulletin No. 121 

“March 23, 2012” 

Page 3 of 8 

A. Prepare the aircraft for safe maintenance. Refer to AMM, Safe Ground Maintenance 

Procedure, Chapter 20.

B. Gain access to all flight control surfaces (aileron, rudder and elevator). 

C. Using the paint thickness measurement maps (Tables 1, 2 and 3) mark the reading 

points on both sides of each flight control surface. 

D. Using an ultrasonic coating thickness gage, Positector 200 series or equivalent, 

measure the paint thickness on the flight control surfaces at each reading point as 

shown on the paint thickness measurement map for each respective flight control 

surface. Record readings on the appropriate tables. See Tables 1, 2 and 3. 

E. Calculate the average paint thickness for each surface by adding all of the readings for 

that surface and dividing by the number of readings. For example, in Table 1 the left 

aileron point readings for mid-chord and rear, upper and lower surfaces would be totaled 

and then divided by 24, which is the number of reading points. 

F. Table 4 contains maximum allowable paint thickness averages for individual aircraft 

serial numbers. These thickness allowances have been determined using historical 

balance information for each individual flight control surface to determine maximum paint 

thickness that could be applied without negatively affecting the balance moment, and are 

not required paint thicknesses. Confirm part number and serial number of the respective 

flight control surface prior to using the values on this chart. If the part number and/or 

serial number do not match the chart information, default values of 5.0 mils must be 

used. 

G. Compare average paint thickness recorded on Tables 1, 2 and 3 with the maximum 

allowable paint thickness average for each flight control surface shown in Table 4. For 

each flight control surface perform the following: 

1. If average paint thickness is equal to or less than 5.0 mils – no further action is 

required, proceed to Step II.H. Report Part II of this customer bulletin as “Not 

Applicable – No action required from Part I.” 

2. If average paint thickness is greater than 5.0 mils, but equal to or less than the serial 

number specific allowances provided in Table 4 - no further action is required, 

proceed to Step II.H. Report Part II of this customer bulletin as “Not Applicable – No 

action required from Part I.” 

3. If average paint thickness is greater than the serial number specific allowances 

provided in Table 4, but less than 13 mils – incorporate AFMS G550-2012-01 or 

EASA-G550-2012-01, as applicable, into the Airplane Flight Manual for continued 

operation at or below 45,000 feet until condition is corrected. Compliance with Part II 

of this customer bulletin is required within 12 months from compliance with Part I. 

4. If average paint thickness is greater than the serial number specific allowances 

provided in Table 4, and exceeds 13.0 mils – continued operation is not allowed, 

contact Gulfstream Customer Support for instructions on compliance with Part II of 

this customer bulletin. 

H. Ensure work area is clean and clear of foreign objects (FOD). 
Gulfstream G550 Customer Bulletin No. 121 

“March 23, 2012” 

Page 4 of 8 

I. Record compliance with Part I of this customer bulletin in the aircraft’s permanent 

maintenance records and return aircraft to flight status. 

J. Report compliance with Part I of this customer bulletin to Gulfstream Computerized 

Maintenance Program (CMP) via electronic transmittal or fill out and fax the attached 

service reply card. 

Part II

III. Accomplishment Instructions

CAUTION: PROTECT WIRE BUNDLES, CONNECTORS AND SURROUNDING 

STRUCTURE DURING ANY MAINTENANCE PROCEDURE FROM SHAVINGS, 

DEBRIS AND CONTAMINATION. MAINTAIN A PROPERLY CLEANED WORK 

AREA THROUGHOUT THE PROCEDURE TO ENSURE THE INTEGRITY OF 

THE AFFECTED COMPONENT / SYSTEM. VISUALLY INSPECT WORK AREA 

USING ADDITIONAL LIGHT AS NECESSARY TO VERIFY ABSENCE OF ANY 

DEBRIS PRIOR TO COMPLETION OF PROCEDURE. FAILURE TO COMPLY 

MAY RESULT IN DAMAGE TO COMPONENTS AND / OR SYSTEMS. 

A. Prepare the aircraft for safe maintenance. Refer to AMM, Safe Ground Maintenance 

Procedure, Chapter 20.

B. For affected surfaces having an overall average thickness greater than the values shown 

on Table 4 as described in Part I, Steps II.G.3. and II.G.4., one of the following corrective 

actions shall be required within the specified compliance time. Contact Gulfstream 

Customer Support for assistance in determining the appropriate corrective action. 

1. Remove flight control surface and rebalance per AMM, Chapter 27. 

2. Strip and repaint with average thickness less than 5.0 mils. Re-measure thickness. 

Refer to GAMPS 4000, revision F. 

3. Sand/buff down to 5.0 mils or less and re-measure thicknesses (not recommended 

on surfaces with averages exceeding 7.0 mils). Refer to GAMPS 4000, revision F. 

C. Ensure work area is clean and clear of foreign objects (FOD). 

D. Remove Airplane Flight Manual Supplement G550-2012-01 or EASA-G550-2012-01, as 

applicable, from the Airplane Flight Manual. 

E. Record compliance with Part II of this customer bulletin in the aircraft’s permanent 

maintenance records and return aircraft to flight status. 

F. Report compliance with Part II of this customer bulletin to Gulfstream Computerized 

Maintenance Program (CMP) via electronic transmittal or fill out and fax the attached 

service reply card. 

If technical assistance is required, contact your area Gulfstream Field Service Representative or call 

Gulfstream Customer Support at 800-810-GULF (4853) or 912-965-4178 (fax 912-965-4184).
Gulfstream G550 Customer Bulletin No. 121 

“March 23, 2012” 

Page 5 of 8 
Gulfstream G550 Customer Bulletin No. 121 

“March 23, 2012” 

Page 6 of 8 
Gulfstream G550 Customer Bulletin No. 121 

“March 23, 2012” 

Page 7 of 8 
Gulfstream G550 Customer Bulletin No. 121 

“March 23, 2012” 

Page 8 of 8 
Gulfstream G550 Customer Bulletin No. 121 

“March 23, 2012” 

Customer Bulletin prepared by Gulfstream Aerospace, 500 Gulfstream Road, P.O. Box 2206, Savannah, Georgia 31402-2206, USA. 

© 2012 Gulfstream Aerospace 

All rights reserved, including the right to reproduce this publication. No part may be reproduced, stored in any retrieval system, or transmitted in any part or form or 

by any means, electronic, photocopying, microfilm, microfiche, mechanical, or otherwise, without prior written permission of Gulfstream Aerospace. 

This technical data is controlled under the Export Administration Regulations by General License TSU. It may not be transferred to a third party 

without the prior written approval of the U.S. Department of Commerce.

GA 611A 2/97 

Part I 

Service Reply Card 

Please fax this page to Gulfstream CMP at 800-944-1775 or 912-963-0265. 

The following Customer Bulletin (CB) has been addressed: 

CB Number A/C A/C Type Compliance Date 

981210 G550 

Aircraft Hours 

Aircraft Landings 

This Customer Bulletin is not applicable because: 

Serial Number not affected 

Appliance not installed 

______Previously complied with (annotate method of compliance below) 

 

Signature Title/Certificate Number Company 

Comments / Suggestions: 
Gulfstream G550 Customer Bulletin No. 121 

“March 23, 2012” 

Customer Bulletin prepared by Gulfstream Aerospace, 500 Gulfstream Road, P.O. Box 2206, Savannah, Georgia 31402-2206, USA. 

© 2012 Gulfstream Aerospace 

All rights reserved, including the right to reproduce this publication. No part may be reproduced, stored in any retrieval system, or transmitted in any part or form or 

by any means, electronic, photocopying, microfilm, microfiche, mechanical, or otherwise, without prior written permission of Gulfstream Aerospace. 

This technical data is controlled under the Export Administration Regulations by General License TSU. It may not be transferred to a third party 

without the prior written approval of the U.S. Department of Commerce.

GA 611A 2/97 

Part II 

Service Reply Card 

Please fax this page to Gulfstream CMP at 800-944-1775 or 912-963-0265. 

The following Customer Bulletin (CB) has been addressed: 

CB Number A/C A/C Type Compliance Date 

981211 G550 

Aircraft Hours 

Aircraft Landings 

This Customer Bulletin is not applicable because: 

Serial Number not affected 

No action required from Part I 

______Previously complied with (annotate method of compliance below) 

 

Signature Title/Certificate Number Company 

Comments / Suggestions: 

This page intentionally left blank. 
FAA APPROVED 

13 March 2012 

epoay coued opeaooocoog s

a 6000 ft altitude ceiling reduction to allow for contin

with surfaces inspected and found having excess coa

Section 0: PREFACE

No Change 

Section 1: LIMITATIONS 

Under 01-03-30: Maximum Operating Altitude, add 

note, and altitude envelope:

Altitude Operating Restriction for Continued Fligh

Non-Conforming Coatings: 

Continued operation within CB compliance time and a

of 45,000 ft. 
BASIC ISSUE FAA 

Page 2 1

Figure 1. Altitude / Mach Flight Envelope 
FAA APPROVED 

13 March 2012 

No Change 

Section 5: PERFORMANCE 

No Change 
BASIC ISSUE FAA 

Page 4 1

This page intentionally left blank. 

This page intentionally left blank. 
FAA APPROVED 

14 March 2012 

epoay coued opeaooocoog s

a 6000 ft altitude ceiling reduction to allow for contin

with surfaces inspected and found having excess coa

Section 0: PREFACE

No Change 

Section 1: LIMITATIONS 

Under 01-03-30: Maximum Operating Altitude, add 

note, and altitude envelope:

Altitude Operating Restriction for Continued Fligh

Non-Conforming Coatings: 

Continued operation within CB compliance time and a

of 45,000 ft. 
BASIC ISSUE FAA 

Page 2 1

Figure 1. Altitude / Mach Flight Envelope 
FAA APPROVED 

14 March 2012 

No Change 

Section 5: PERFORMANCE 

No Change 
BASIC ISSUE FAA 

Page 4 1

This page intentionally left blank.