2017 AF Corrosion Conference Corrosion in the Aircraft

Corrosion in the

Aircraft Structural

Integrity Program

(ASIP)

7 June 2017

Chuck Babish

AFLCMC/EZ

DSN: 785-5312

[email protected]

2017 AF Corrosion Conference

DISTRIBUTION A. Cleared for Public Release, Distribution Unlimited

Aircraft Structural Integrity Program

Outline

• ASIP Introduction

• Corrosion Requirements in ASIP

• Corrosion Metrics in ASIP Reviews

• Corrosion R&D Needs

• Other CP&C Needs

2


Why Does USAF Have ASIP?

3

Aircraft Date Failure

Location

Number of

Flight Hours

Cause of

Failure

B-47B 13-Mar-58Center Wing,

BL 452,077 Fatigue

TB‑ 47B 13-Mar-58Center Wing,

BL 352,419 Fatigue

B-47E 21-Mar-58 Disintegration 1,129 Fatigue

B-47E 10-Apr-58Wing to Fuse

Fitting, FS 5151,265 Fatigue

B-47E 15-Apr-58 Disintegration 1,419 Overload

• Established on 12 June 1958 to control structural fatigue

in response to four B-47 aircraft losses in one month


4

Why Damage Tolerance

Philosophy in ASIP?

Defect

• F-111 loss on 22 December 1969 and F-5 loss on 20 April

1970 demonstrated ASIP fatigue controls not effective– F-111 structural failure due to fatigue cracking from a

manufacturing defect (design unable to tolerate damage)


5

Aircraft Safety Record Since ASIP Damage Tolerance Implemented

1.E-08

1.E-07

1.E-06

1.E-05

1.E-04

1.E-031945

1950

1955

1960

1965

1970

1975

1980

1985

1990

1995

2000

2005

2010

2015

2020

US

AF

De

str

oye

d A

irc

raft

Ra

te

USAF Destroyed Aircraft Rate (Annual Rate for All Causes, Cumulative Rate for Structural Failures)

All Causes Except Combat

Structures


ASIP Policy (1 of 2)

• AFPD 63-1, Acquisition and Life Cycle Management

– “3.6 The Air Force shall apply integrity programs to

weapon systems.”

• AFI 63-101, Acquisition and Life Cycle Management

– “5.4.1.3 For each Aircraft Mission Design Series (MDS)

the Air Force acquires, uses, or leases, the PM shall

establish an Aircraft Structural Integrity Program (ASIP)

IAW AFI 63-140, Aircraft Structural Integrity Program.”

• “5.4.1.3.1. Corrosion prevention and control (CPC)…is an

important element of product and system integrity. The PM shall

integrate CPC with program integrity efforts.”

• “5.4.1.3.2. Each ASIP shall be developed, documented, approved,

and executed according to MIL-STD-1530, Aircraft Structural

Integrity Program (ASIP).”

6


ASIP Policy (2 of 2)

• AFI 63-140, Aircraft Structural Integrity Program– “3.1. The PM shall establish an ASIP for each Mission Design Series

(MDS) the Air Force acquires, uses, or leases.”

– “3.2. For each aircraft MDS developed or modified by the Air Force,

the ASIP shall comply with MIL-STD-1530, DoD Standard Practice for

Aircraft Structural Integrity Program (ASIP).”

• “3.2.2. Obtain PEO approval for the ASIP Master Plan before the

System Requirements Review (SRR).”

• “3.2.5. For aircraft that are to be modified, fly new missions, or

whose operation will extend past the aircraft’s certified design

service life, develop a revised ASIP Master Plan and obtain PEO

approval of the revised plan before modifications are executed,

regular flights begin under the new mission, or commencing

operations beyond the previously certified service life.”

• MIL-STD-1530D, Aircraft Structural Integrity Program

– With Change 1 published 13 October 2016

7


8

Task III, Full-

Scale

Testing

ASIP Framework

Established in MIL-STD-1530

Task I, Design

Information

Task IV,

Certification &

Force Management

Development

Task V, Force Management Execution

Task II, Design

Analyses &

Development Tests


9

Corrosion Requirements in ASIP:

A Continual Evolution (1 of 4)

• Pre-STD phase: focus on fatigue, strength, & flutter

– HQ USAF Message, 19 November 1958 (ASIP official

start)

– ASD-TN-61-141, September 1961

– ASD-TR-66-57, January 1968

• MIL-STD-1530, 1 September 1972– “Structural durability requires that the areas of the structure that could

be susceptible to fatigue, corrosion, or other crack initiation

mechanisms…”

– “Complete…corrosion-control requirements…for all fracture and

fatigue critical parts…”

– “…that meets the strength, corrosion, and service life requirements…”

• MIL-STD-1530A, 11 December 1975– “The corrosion prevention and control plan shall be in accordance with

MIL-STD-1568”


10



• MIL-STD-1530B, 20 February 2004

– “Corrosion prevention shall also be a primary consideration in the

development and implementation of the durability and damage tolerance

control process and the fleet management process.”

– “An appropriate tracking methodology shall be developed and

implemented to monitor and assess corrosion potential and other

environmentally-driven structural or critical coating degradation modes.”

– Appendix B: “Inspections of individual air vehicles shall be accomplished

to ascertain the condition of the airframes with respect to corrosion.

Emphasis shall be placed on corrosion detection through nondestructive

inspections and prevention. For those areas found to be corroded, the

preferred approach is to eliminate the corrosion by removing it or

replacing the structural elements in question. This may not be feasible in

rare cases because of near-term operational requirements. In these

cases, an assessment shall be accomplished to determine the change in

the inspection program that will account for the influence of corrosion on

structural integrity.”


11



• MIL-STD-1530C, 1 November 2005

– “A Corrosion Prevention and Control Program shall be established for

the aircraft structure. The program shall establish a Corrosion

Prevention Advisory Board (CPAB) responsible for establishment and

oversight of the execution of the program..”

– “A Corrosion Prevention and Control Plan shall be prepared and

corrosion prevention and control processes shall be used.”

– “5.1.5.2 Evaluation of corrosion susceptibility”

– “5.2.8 Corrosion assessment”

– “5.2.14.2 Corrosion tests”

– “5.5.6.2 Corrosion assessment updates”


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• MIL-STD-1530D Change 1, 13 October 2016Task I Task II Task III Task IV Task V

Design InformationDesign Analyses &

Development TestingFull-Scale Testing

Certification & Force

Management DevelopmentForce Management Execution

1. ASIP Master Plan 1. Materials and Structural

Allowables1. Static Tests 1. Structural Certification 1.L/ESS Execution

2. Design Service Life & Design

Usage 2. Loads Analysis

2. First Flight Verification Ground

Tests

2. Strength Summary & Operating

Restrictions (SSOR)2. IAT Execution

3. Structural Design Criteria 3. Design Loads/Environment

Spectra 3. Flight Tests

3. Force Structural Maintenance

Plan (FSMP)3. DADTA Updates

4. Durability & Damage Tolerance

Control4. Stress and Strength Analysis 4. Durability Tests

4. Loads/ Environment Spectra

Survey (L/ESS) System

Development

4. L/ESS and IAT System Updates

5. Corrosion Prevention & Control 5. Durability Analysis 5. Damage Tolerance Tests 5. Individual Aircraft Tracking (IAT)

System Development 5. NDI Updates

6. Nondestructive Inspection 6. Damage Tolerance Analysis 6. Climatic Tests 6. Force Management Database

Development

6. Structural Risk Analysis

Updates

7. Selection of Materials,

Processes, Joining Methods &

Structural Concepts

7. Corrosion Assessment 7. Interpretation & Evaluation of

Test Findings7. Technical Orders

7. CPC Plan & Corrosion

Assessment Updates

8. Sonic Fatigue Analysis 8. Resolution of Test Findings 8. Analytical Condition Inspection

9. Vibration Analysis 9. FSMP Updates

10. Aeroelastic and

Aeroservoelastic Analysis10. Technical Orders Updates

11. Mass Properties Analysis 11. Repairs

12. Survivability Analysis 12. Structural Maintenance

Database Execution

13. Design Development Tests 13. Structural Certification

Updates

14. Structural Risk Analysis14. Economic Service Life

Analysis Updates

15. Economic Service Life

Analysis15. Others as Required


Corrosion Metrics in ASIP Reviews

13

Corrosion Prevention

& ControlCriteria for Compliance Metric Green Yellow Red

Corrosion Manager1. Assigned & adequately trained (e.g. DAU CLM 038, CLE 070, etc.).

2. Full-time job for the a/c weapon system; or if part-time, have sufficient time to execute CP&C.Both 1 of 2 0 of 2

Corrosion Prevention &

Control Plan

1. CP&C Plan is approved by AF CPCO, it's current (within 5 years) and it's executed as written.

2. It drives all aspects of aircraft program planning, funding & scheduling related to CP&CBoth 1 of 2 0 of 2

Corrosion Prevention

Advisory Board

1. CP Advisory Boards are conducted annually and AF CPCO participates.

2. Results are evaluated and used to revise maintenance requirements as required.Both 1 of 2 0 of 2

Standards &

Specifications

1. MIL-STD-1568 & MIL-HDBK-1587 are used or equivalent incorporated into approved specs.

2. Process/finish specs exist, are coordinated with AF CPCO & AF CTIO, and are used.Both 1 of 2 0 of 2

T.O.s / Work Specs1. -23 or equivalent is sufficient or planned if program not at this phase.

2. -6, -3 and PDM work specs (if applicable) are sufficient.Both 1 of 2 0 of 2

Corrosion

Assessments

1. Performed every 5 years or more often.


Analytical Condition

Inspection

1. Sufficient corrosion tasks are included in annual ACI requirements.


Operational

Environment

1. Basing locations tracked: time at mild, moderate, & severe environment determined for each a/c

using T.O. 1-1-691 and input from AF CPCO for base locations not included in T.O.

2. Corrosion sensors are being or have been used to characterize environment (sampling is OK).

Both 1 of 2 0 of 2

CP&C Maintenance

Impacts

1. All aircraft structure corrosion related maintenance is included in the FSMP or CPCP or other.

2. Includes cost & schedule impacts associated with aircraft structure corrosion maintenance.Both 1 of 2 0 of 2

Life Cycle Cost Benefit

Analysis

1. Life cycle cost-benefit analyses are conducted to evaluate inspection and repair versus

modification/replacement approaches for corrosion damage.

2. Results are effectively communicated to decision makers.

Both 1 of 2 0 of 2

Overall CP&C Metric Weight factor method used to combine these 10 metrics into an overall CP&C metric



• Issue #1: CP&C cost & schedule impacts on MX not well

understood or readily available for most a/c

– Data should be included in the FSMP, CP&C Plan or

other document

• Issue #2: CP&C Plan needs improvement for many a/c

– Use AF CPCO CP&C Plan Template for next update

• Issue #3: ACI program use needs improvement

– Corrosion inspections should be part of annual ACI

• Issue #4: Corrosion Manager improvements needed

– More CMs and/or more training and/or more time

• Issue #5: CPAB improvements needed

– Use AF CPCO personnel, invite MX personnel, ensure

adequate time to discuss issues

14



15

Legend:

CM: Corrosion Manager

CPCP: Corrosion Prevention &

Control Plan

CPAB: Corrosion Prevention

Advisory Board

Spec: Specifications & Standards

TOs: Technical Orders

CA: Corrosion Assessments

ACI: Analytical Condition

Inspection

Env: Operational Environment

MX: Maintenance Impacts

CBA: Life Cycle Cost Benefit

Analysis

#1#2 #3#4 #5

0

5

10

15

20

25

30

CM CPCP CPAB Spec TOs CA ACI Env MX CBA

# o

f M

DS

's

Corrosion Management, Aircraft in Sustainment


16

Corrosion R&D Needs to Improve

ASIP Execution (1 of 3)

1. Ability to decompose top-level design service life

requirements (e.g., years) and sustainment requirements

(e.g., maintenance man-hour per flight hour, aircraft

availability) into verifiable requirements that:

– Leads to proper selection of materials, processes,

coatings, etc., during the design phase

– Eliminates the debate on what is adequate corrosion

prevention to achieve the design requirements

– Establishes periodic maintenance requirements such

as wash intervals, exterior topcoat replacement

intervals, etc., that are “acceptable”

– Survives pressures to reduce cost, weight, etc.

2. Accelerated test methods (designs, quantities,

environment, duration, etc.) and pass/fail criteria that

enables above


17



3. Ability to define the appropriate corrosion-related

maintenance requirements throughout a/c life cycle

– What are the appropriate adjustments to periodic

maintenance requirements such as wash intervals,

exterior topcoat replacement intervals, etc.?

– How does corrosion damage degrade damage

tolerance, static strength, rigidity, etc.?

– When are damage tolerance based inspections

combined with corrosion surveillance inspections no

longer sufficient to protect safety?

– How should corrosion damage and rates be

considered in damage-tolerance based inspection

intervals?

– How should corrosion damage be repaired?

– What is the ROI for use of CPCs?


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4. Validated methods to improve detection of corrosion

damage and characterize corrosion severity

5. Ability to adequately consider corrosion damage when

establishing service life limits (SLL) and during

evaluation of a service life extension program (SLEP)

– Can quantitative methods be used to determine

structural risk due to corrosion damage vs time?

– When does corrosion damage become uneconomical?

– When do non-replaceable coatings simply no longer

provide adequate corrosion protection?

IOW, need an ability to design, analyze, test, and

manage corrosion in the same manner as fatigue!


19

Other CP&C Needs (1 of 2)

• Knowledge and data to enable credible and convincible

business case and Life Cycle Cost (LCC) analysis for any

trade studies involving corrosion prevention & control

such as:

– Service life extension programs

– Changes to depot induction frequency

– Changes from field-level to depot-level corrosion

inspection & repairs

– Requests for a/c wash extensions

– Pre-coated vs. wet-installed fasteners

– Pre-coated vs. faying surface seal & edge seal

structural assemblies

– Top-coat or not in corrosion-prone internal locations

– Proposed use of T6 temper


20

Other CP&C Needs (2 of 2)

• DoD-wide evaluation, recommendation and/or approval

for cross-cutting initiatives that impact corrosion

prevention & control such as:

– Environmental law changes (e.g., hexavalent chrome,

cadmium)

– Material or product form substitutions during

sustainment

– Process changes (e.g., paint removal)

• Coating systems (surface treatment + primer + topcoat)

that meet coating specifications, environmental

regulations, and aircraft cost, schedule and performance

requirements


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Documents

2017 AF Corrosion Conference Corrosion in the Aircraft