PAFI-RTP-004 Ambient and Elevated Storage Stability REV A.pdf

Revision: A Date: June 13, 2025

Storage Stability Test

PAFI-RTP-004

PAFI Rig #4 Storage Test

PAFI Fuels – Storage Stability

PAFI-RTP-004, FAA PAFI Storage Stability Test Plan Rev A

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Revision Log:

Rev No.

Rev Date

Af fected Page(s) Descript ion of Revis ion

None 12/22/20

All Initial Release

A 11/29/22 Multiple General update for organizat ional changes and current formatt ing. Inc ludes edits to al low for public release of the document . Added disc laimer and updated preface on pages 2/3.

Changed references of “test fuels” to the tes t fuel .

Added safety notes to sect ion 1.1.

A 6/13/25 Appendix A

Updated Appendix A wi th pre and post fuel test ing

PREFACE

This test plan spec if ies the requirements for conducting comparat ive materials compatibil ity screening tes ts under the FAA’s piston av iation fuels ini tiat ive (PAFI). This document is derived f rom extens ive FAA and industry experience and best pract ices for evaluat ing the suitabil ity of av iat ion fuels for use in the pis ton powered general aviat ion f leet . This document is used by the FAA to compare and evaluate new aviat ion fuels relative to the performance of 100LL aviat ion gasoline that meets ASTM D910.

In addit ion to the candidate unleaded fuel , a high aromat ic ASTM D910 fuel formulation is required for the screening tests under this plan.

This document is not intended to prov ide a method to obtain data to serve as a showing of compl iance to regulatory requirements for the cert if ication of ai rc raft or ai rc raf t engines.

Furthermore, the material in this document does not change or permit deviat ions f rom ex ist ing regulatory requirements. This material is neither mandatory nor regulatory in nature. Use of this document or any derivat ive, in an attempt to obtain an FAA authorization of an alternative av iation fuel , should be pre-coordinated and approved by the appropriate FAA office(s) as part of an approved quali f icat ion program.

Successful complet ion of this test plan prov ides data that may support both FAA Fleet authorizat ion and development of an ASTM product ion speci ficat ion for PAFI Fuels. It also al lows the collec tion of data to be used to generate performance and detonat ion performance values in support of other candidate fuel types being invest igated under various FAA Research & Development projects.

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References made to the Alternat ive Fuels Program Off ice or AFPO, refer to the group within the FAA that is responsible for the PAFI program. At the t ime of this revis ion, that group is the AIR-650 organizat ion. Please see https: //www.faa.gov/about/ init iat ives/avgas/org_info .

NOTE

ASTM International granted a limited, nonexclusive license to reproduce the equations requested in this FAA test document. They are reprinted, with permission, copyright ASTM International. A copy of the complete standard may be obtained from www.astm.org.

https://www.faa.gov/about/initiatives/avgas/org_info http://www.astm.org/

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TABLE OF CONTENTS

1. SCOPE

1.1. Provisos

2. OBJECTIVES

3. BACKGROUND

4. PAFI RIG SCREENING TEST PLANS

5. APPLICABLE FAA, SAE & ASTM REQUIREMENTS

5.1. FAA Regulations

5.2. FAA Advisory Circulars & Orders

5.3. SAE Standards

5.4. ASTM Guidance & Practices

6. APPLICABLE OEM DOCUMENTS

7. DESCRIPTION OF TEST ARTICLES

7.1. Ambient Storage Stability

7.1.1. Glass Jars

7.1.2. Glass Rods

7.1.3. Wooden Dowels

7.1.4. Aircraft Fuel Filler Cap

7.2. Accelerated (Oven) Storage Stability

8. DEFINITIONS & TERMINOLOGY

8.1. Adherent Insolubles

8.2. Exposure

8.3. Filterable Insolubles

8.4. Calibration

8.5. Sample

8.6. Sample Set

8.7. Specimen

8.8. Validation

9. FUEL CONFORMITY

9.1. Test Fuel

10. SAFETY PROCEDURES

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10.1. Sample Fill (Reference ASTM D4057-12, Section 5.2)

10.2. Static Charge (REFERENCE ASTM D4057-12)

10.2.1. Grounding (D4057-12, Section 5.4.1)

10.2.2. Personal Attire (D4057-12, Section 4.5.2)

10.3. Vapor Hazards

10.4. Personal Protective Equipment (PPE)

11. PRE-TEST REQUIREMENTS

11.1. Specimen Identification

11.2. Pre-Exposure Fuel Preparation

11.2.1. Ambient Storage Stability Testing

11.2.2. Elevated Storage Stability Testing

11.3. Pre-Exposure Baseline Data

11.3.1. Ambient Storage Stability Testing

11.3.2. Elevated Storage Stability Testing

11.4. Pre-Exposure Photographs

11.4.1. Ambient Storage Stability Testing

11.4.2. Elevated Storage Stability Testing

11.5. Laboratory Notebook

12. TEST FACILITY & EQUIPMENT

12.1. Fuel Drum Transfer Valving

12.2. Ambient Storage Testing

12.2.1. Exterior Storage Drums

12.2.2. Aluminum Open Head Drum with Cover

12.2.3. Inner Storage Rack

12.2.4. Storage Containment for Collected Glass Rods and Dowels

12.2.5. Specimen Jar Lifting Rig

12.2.6. Drum Stabilizing Structure (Feet)

12.2.7. Controlled Access Space

12.2.8. Ambient Weather Monitoring Equipment

12.3. Elevated (Accelerated) Storage Testing

12.3.1. Elevated Temperature Controlled Areas – Ovens

12.3.2. ASME Stainless Steel Pressure Vessels with Fluorocarbon Seals

12.3.3. 500mL (1 pint) glass Jars

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12.4. Karl Fischer Moisture Meter – Coulometric

12.5. Calibrated / Validated Laboratory Measuring Equipment

12.6. ASTM D4625/D5452 Vacuum Filter Apparatus

12.7. Other Specialty Equipment

13. TEST WITNESSING

14. TEST PROCEDURE – AMBIENT STORAGE STABILITY

14.1. Materials

14.2. Rig Assembly

14.3. Test Start

14.3.1. Drum Fill

14.4. Specimen and Data Collection

14.4.1. Restrictions and Rules

14.4.2. Opening Drum

14.4.3. Procedure for wooden dowel

14.4.4. Procedure for the Glass Rod

14.4.5. Procedure for Fuel Specimen Collection

14.5. Preparing for Continued Exposure

14.5.1. Mark Fuel Level

14.5.2. Close Drums

14.6. Week 12

14.6.1. Dowel and Glass Rod

14.6.2. Fuel Specimen Collection

14.7. Post Exposure Measurements

14.7.1. evaporative Losses

14.7.2. Deposit Formation

14.7.3. Moisture Content by Karl Fischer – D6304

14.7.4. Copper Strip Corrosion – D130

14.7.5. Color - D156 AND D1500

14.7.6. Existent Gum Content – D381

14.7.7. Total Acid Number – D664

14.7.8. Water Reaction Test – D1094

14.7.9. Motor Octane Number – D2700

14.7.10. Density – D4052

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14.7.11. Freeze Point – D2386

14.7.12. Electrical Conductivity – D2624

14.7.13. Hydrogen Peroxide Content – D3703

14.7.14. Net Heat of Combustion – D4809

14.7.15. Vapor pressure – D5191

14.7.16. Particle Contamination – D5452

14.7.17. Hydrogen (D7171) and Sulfur (D2622) Content

14.7.18. Distillation – D86

14.7.19. Research Octane Number – D2699

14.7.20. Gas Chromatograph and Mass-Spectroscopy (GC-MS)

14.8. Calculations

14.8.1. Evaporation

14.8.2. Deposition

14.8.3. Karl Fischer – D6304

14.8.4. Distillation – D86

14.8.5. Copper Strip Corrosion – D130

14.8.6. Viscosity – D445

14.8.7. Color – D156 and D1500

14.8.8. Existent Gum Content – D381

14.8.9. Total Acid Number – D664

14.8.10. Water Reaction Test - D1094

14.8.11. Motor Octane Number – D2700

14.8.12. Density – D4052

14.8.13. Freeze Point – D2386

14.8.14. Electrical Conductivity – D2624

14.8.15. Hydrogen Peroxide Content – D3703

14.8.16. Net Heat of Combustion – D4809

14.8.17. Vapor pressure – D5191

14.8.18. Particle Contamination – D5452

14.8.19. Hydrogen (D7171) and Sulfur (D2622) Content

14.8.20. Gas Chromatography

15. TEST PROCEDURE – ELEVATED STORAGE STABILITY

15.1. Materials

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15.2. Rig Assembly

15.2.1. Preparation of Pressure Vessels for Five-Gallon Sample

15.3. Test Start

15.3.1. 400 mL Samples

15.3.2. Pressure Vessel – Five Gallon Samples

15.4. Specimen and Data Collection

15.4.1. 400 mL Samples

15.4.2. Pressure Vessel – Five Gallon Samples

15.5. Week 12

15.6. Post Exposure Measurements

15.6.1. Filterable Insolubles – ASTM D4625

15.6.2. Adherent Insolubles - ASTM D4625

15.6.3. Potential Gum and Precipitate – ASTM D873

15.6.4. Net Heat of Combustion – D4809

15.6.5. Vapor pressure – D5191

15.6.6. Lead (D5059), Hydrogen (D7171) and Sulfur (D2622) Content

15.7. Calculations

15.7.1. Moisture Content by Karl Fischer – D6304

15.7.2. Filterable Insolubles – ASTM D4625

15.7.3. Adherent Insolubles

15.7.4. Potential Gum and Precipitate – ASTM D873

15.7.5. Net Heat of Combustion – D4809

15.7.6. Vapor pressure – D5191

15.7.7. Lead (D5059), Hydrogen (D7171) and Sulfur (D2622) Content

16. PASS/FAIL CRITERIA

17. TEST PERSONNEL

18. TEST RESULTS REPORT

19. REFERENCES

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TABLE OF APPENDICES

APPENDIX A – TEST FUEL COA REQUIREMENTS………..…..………..….. 73

APPENDIX B – EXAMPLE BULK EVAPORATION TABLE…..…..………..….. 80

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Materials Test Plan

Storage Stability Test

1. SCOPE

This test plan spec ifies the requirements and procedures for conduct ing comparative s torage stabi li ty test ing of an unleaded fuel to generate data required for part icipat ing in the FAA Piston Av iation Fuels Ini tiat ive (PAFI) test program.

This data wil l be used for the evaluat ion of an unleaded fuel being tested in the PAFI test program. The data wi l l be used as part of the f inal evaluat ion of data for f leet authorization.

Speci fic objectives of this plan are stated as fol lows:

1) Execute long-term (12 week or longer) storage stabi lity test ing under hot, humid, ambient condi tions, and col lect fuel performance data to assess fuel propensi ty for separation, degradat ion, col lec tion of water, or other anomalous behavior with t ime.

2) Execute elevated temperature (accelerated) storage s tabil ity test ing at 43°C (110°F) and col lect fuel performance data to assess fuel degradation due to changes in oxidat ive and thermal stabil ity, and in total ac id number.

The test plan inc ludes the requirements for conf i rming baseline condit ion, test set -up, inst rumentat ion, specimen col lection and support ing documentation such as fuel certi f icat ion documents as prerequisi tes to the test ing identif ied.

The long-term, storage test is to be performed at a locat ion that provides warm/hot, humid ambient condi tions, for example at a southern U.S., coastal locat ion, over a 12-week (3 month) minimum period. Testing involves collect ing samples and inspecting the fuel every three weeks for a minimum of 12 weeks.

Data to be collected inc lude: format ion of water bottoms and increas ing moisture content, bulk evaporation, deposi tion formation, and microbial growth within the test rig. In addition, one-gal lon samples wi ll be col lected and analyzed for changes in ex istent gums, Saybolt color, motor octane number, total ac id number, water reaction, and copper s t rip corrosion. Other tests inc lude vapor pressure, elect rical conduct iv ity, hydrogen content, sulfur content, heat of combust ion, and f reeze point. The fuel remaining after 12 weeks shall have a ful l cert if icate of analysis performed.

Note: The locat ion for the testing must be ident if ied and submitted to the FAA Alternative Fuels Program Off ice (AFPO) for approval prior to beginning testing.

The locat ion must have a historical record of elevated temperatures and humidity for the majority of a 12-week period.

The accelerated storage test is to be performed at 43 °C (110 °F) us ing sealed containers. Test ing involves collect ing samples every three weeks for 12 weeks

11 | P a g e PAFI-RTP-004 and replenishing the available oxygen within the test vessel. Each sample shall be analyzed for moisture content , fi lterable solids , and adherent insolubles. The fuel after 12 weeks (3 months) shall have a full certif icate of analys is performed.

Requirements for conf i rming tes t equipment conf igurat ion, test inst rumentation, and supporting documentat ion such as fuel cert if ication and equipment cal ibration/val idation are pre-requis ites to the testing ident if ied.

1.1. PROVISOS

The following ident ifies s ignif icant assumptions, requirements, and prov isions associated with the test ing prescribed within this test plan. Testing performed pursuant to this test plan provides data supporting FAA fleet authorization for PAFI unleaded fuels. Testing performed to this tes t plan may be witnessed by an ident if ied designated representative of the FAA. This may be achieved through the use of a Designated Engineering Representat ive (DER) or other representat ive approved by the AFPO staff prior to executing test ing.

NOTE: In the event tes ting is conducted outs ide the FAA’s Wi ll iam J. Hughes Technical Center, tes ting performed to this test plan must be witnessed by an ident if ied designated representative of the FAA. This may be achieved through the use of a Designated Engineering Representat ive (DER) or other representat ive approved by the FAA AFPO or PAFI Advisory Committee prior to executing test ing.

NOTE: Test ing perfo rmed pursuant to th is test p lan p rovides data support ing 1 ) FAA f lee t au thoriza t ion fo r each PAFI un leaded fue l, and 2 ) the development of an ASTM Inte rnat iona l av iat ion gaso l ine p roduct ion specif ica t ion fo r each fue l.

2. OBJECTIVES

The objective of the Storage Stabil ity Test Plan comparat ive fuel performance tests is def ined as fol lows .

1) Determine the s tabil ity of unleaded av iation fuel under warm, humid condit ions and compare i ts stabi li ty to leaded aviat ion fuel.

2) Determine the accelerated s tabil ity of unleaded av iation fuel under control led elevated temperature condit ions (43 °C) and compare i ts stabi l ity to leaded aviation fuel .

3. BACKGROUND

Bulk fuels stored for long periods of time can suffer f rom fuel s torage degradat ion and contaminat ion, resulting in serious fuel instabil ity problems when eventually used. Problems encountered include polymerizat ion and ox idation. The format ion of f il terable solids and gums can result in operational problems when the fuel is used. Depending on the location, aviat ion gasoline storage tanks may be smal ler

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(500 to 2500 gal lons) with lower turnover rates than experienced with jet fuel storage tanks.

The fuel tanks on aircraft are suscept ible to the same concerns, however, have a smaller mass than a bulk tank and may be more suscept ible to degradat ion. No industry accepted storage stabi li ty tes t spec ific to smaller tanks such as those on aircraf t is avai lable. These propert ies relate to the thermal stabi l ity, oxidat ion stabi l ity, and acid number of the fuel.

His torical ly av iation gasol ine has displayed an observably stable nature. This is due primari ly to the chemical composit ion of av iat ion gasol ine produced in compl iance with ASTM D910, and the presence of lead which prov ides an antimicrobial funct ion. In order to blend fuels which have the necessary detonation resis tance, components with dif ferent propert ies with respect to both thermal and oxidat ive stabi lity, and with respect to i ts resistance to microbial growth, may be used.

Current ly no standard industry test for evaluat ing the long-term s torage stabi li ty of av iation gasol ine under ambient condit ions ex ists . An industry accepted method, ASTM D4625, ex ists for evaluating accelerated bulk storage stabi lity of jet fuel at 43 °C (110 °F), but not for gasol ine.

The accelerated test method is being appl ied to the candidate unleaded fuel under PAFI. However, due to the higher evaporat ion rates of the av iat ion gasoline test fuel ; this ex isting jet fuel tes t method has been modif ied. The exis ting ASTM test ing involves the use of vented glass jars s tored at 43 °C for the durat ion of the test. Specimens are col lected at t imed intervals and tested for the formation of soluble and insoluble gums created by ox idation of the fuel. This vented system is not pract ical for the gasoline test fluids due to their higher evaporat ion rates.

The modif ied method involves sealed containers with rout ine int roduction of ai r to replenish the oxygen in the system. The modif icat ions to the test method (seal ing of the individual specimens) are based on ex ist ing industry research (SwRI gasoline studies). In all other ways, the interval test ing is performed in compl iance wi th the ASTM D4625 test method.

Accordingly , this tes t plan prepared for the FAA PAFI Rig screening test, provides for the development of a common set of val idat ion data support ing compliance wi th both ASTM and FAA requirements . Current ly there are no publ ished regulations for thermal or oxidat ive s tabil ity propert ies. ASTM D7826 prov ides guidance in evaluating the comparative behav iors of fuels and the handl ing of non-comparative outcomes.

The scope and extent of the FAA PAFI Storage Stabi li ty Test plan is def ined by TAC-PROJ-015, latest revis ion, which integrates the f indings and recommendat ions of the PAFI Technical Team meeting of October 9, 2014.

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4. PAFI RIG SCREENING TEST PLANS

The matrix of r ig screening tes t plans support ing the test protocols ident ified in TAC-PRJ-008, latest revis ion, is presented as follows. The tes t plans wi l l follow a common format with general procedures, processes, and test inst rumentation being common to all. The current plan is highl ighted in the list below.

RIG SCREENING TEST PLANS

PAFI-RTP-001, Cold Flow Hardware Test PAFI-RTP-002, Carburetor Icing Test (Removed) PAFI-RTP-003, Dynamic/Operational Hardware Test (Removed) PAFI-RTP-004, Long Term Storage Test , Ambient and Elevated PAFI-RTP-005, Cold Storage Stabil ity Test PAFI-RTP-006, Hot Surface Ignit ion Temperature Test (Removed) PAFI-RTP-007, Ful l Scale Engine Emiss ions Test (Not Released) PAFI-RTP-008, Comingling Evaluat ion with 100LL (Not Released) PAFI-RTP-009, Dynamic Diaphragm Test PAFI-RTP-010, Fuel Sump Valve Test PAFI-RTP-011, Vented Drum Storage Test

Test plans prepared in support of the FAA PAFI test program for unleaded fuels are subject to the fol lowing review and approval protocol.

1) PAFI r ig test plans follow a format and content cons istent with establ ished practice for FAA compl iance projects .

2) Draft tes t plans are furnished to the FAA AFPO off ice for review and approval prior to release to the TAC.

3) Upon concurrence from the FAA AFPO, the test plan wil l be formal ly furnished to the PAFI TAC for rev iew and concurrence preceded by FAA Contracts review and authorization for release to the TAC.

4) A f inal tes t plan wil l be released incorporat ing changes resul ting f rom the TAC rev iew.

5) All changes and referrals to this test plan should reference the latest revis ion level and date.

5. APPLICABLE FAA, SAE & ASTM REQUIREMENTS

The following is a lis ting of the appl icable FAA, SAE, and ASTM documents which contain informat ion relevant to the test ing spec if ied by this test plan.

5.1. FAA REGULATIONS

There are no FAA Regulat ions applicable to the test ing.

5.2. FAA ADVISORY CIRCULARS & ORDERS

There are no FAA Advisory c i rculars or orders applicable to the test ing.

5.3. SAE STANDARDS

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There are no SAE standards applicable to the test ing.

5.4. ASTM GUIDANCE & PRACTICES

ASTM guidance and s tandards applicable to the test ing identi fied are listed as follows. Data provided by this test plan wil l support the development of an ASTM product ion spec if ication for the unleaded fuel.

1) ASTM D4625 Standard Test Method for Middle Dis ti llate Fuel Storage Stabil ity at 43 °C (110 °F)

2) ASTM D7826-19a Standard Guide for Evaluat ion of New Aviation Gasolines and New Aviat ion Gasol ine Addit ives

6. APPLICABLE OEM DOCUMENTS

There are no appl icable OEM documents required.

7. DESCRIPTION OF TEST ARTICLES

7.1. AMBIENT STORAGE STABILITY

This tes t plan covers the evaluat ion of changes to both the fuel and the fuel tank environment as a result of changes in the fuel . Mult iple test art icles are required wi thin each indiv idual task. In addit ion, the fuel itself, collec ted over the durat ion of the tes t, also represents a test artic le.

7.1.1. GLASS JARS

In order to assess the propensi ty of a fuel to draw and settle water f rom the ambient ai r, it is necessary to observe the fuel tank bottoms. I t is not pract ical for the researcher to inspect the bottoms of the ambient tank rig, so a means of col lect ing the bottoms and bringing them to the researcher is required. The use of glass jars placed at the bottom of the s torage tank permits the ext ract ion of fuel tank “bot toms” without unacceptable mixing. The glass jars shal l have a minimum volume of one quart (one l iter). Whi le one-quart , wide mouth canning jars have been successful ly used in prev ious test ing, any glass jar wi th the necessary volume and a wide mouth is acceptable. Five jars per fuel sample are required.

7.1.2. GLASS RODS

To assess the propens ity for the formation of sediment, deposi ts, or microbial growth, it is necessary to prov ide a surface for col lect ion of any depos its which are subsequently inspected. Standard 1.25 to 2.5 cm (½ to 1 inch) diameter boros il icate glass rods with a length simi lar to the height of the fuel tank rig are required. Five rods per fuel sample are required.

7.1.3. WOODEN DOWELS

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In an at tempt to assess how quickly fuel is l ikely to evaporate f rom a fuel tank over t ime, a means of pos it ively measuring fuel volume is required. Because the diameter of the fuel tank rig is constant, the fuel volume can be determined by measuring the fuel depth. Because one gal lon fuel samples wi l l be collected at each inspect ion, it is necessary to measure the fuel depth after al l sampling is completed during the inspect ion, and to compare this value to the fuel depth after the fol lowing three-week exposure t ime. Previous test ing has found that s tandard 1 to 2.5 cm (½ to 1 inch) diameter unt reated hardwood wooden dowels can be successful ly used. The use of pine dowels is not recommended. These dowels also prov ide a support for the water indicating paste used to inspect the tank bottoms for f ree water at each inspection. Five dowels per fuel sample are required.

7.1.4. AIRCRAFT FUEL FILLER CAP

As part of the material compat ibil ity tes ting, the long-term storage s tabil ity tes ting is best suited for test ing fuel f il ler caps for fuel compat ibi lity . A s tandard aircraft fuel cap shal l be instal led into the fuel tank rig aluminum l id (Figure 1). One fuel cap per fuel sample is required.

Figure 1 - Fuel Filler Cap Installed in Ambient Storage Rig Lid

7.2. ACCELERATED (OVEN) STORAGE STABILITY

This tes t plan covers the evaluat ion of changes to the fuel over t ime under elevated temperature. The fuel itself is the only test art ic le.

8. DEFINITIONS & TERMINOLOGY

Definit ions, terminology, and abbrev iat ions spec ific to this document and to FAA nomenclature are summarized in the fol lowing section.

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8.1. ADHERENT INSOLUBLES

Adherent insoluble are gums formed during the storage test and are adherent to the specimen container after the tes t fuel is removed. They are not soluble in the fuel and remain in the container.

8.2. EXPOSURE

Within this document, the term exposure is the execution of a test on a test f luid at a given temperature for a given amount of time.

8.3. FILTERABLE INSOLUBLES

Fi lterable insolubles are sol ids formed during the s torage test which remain in the fuel and can be removed by f i ltering the fuel . They are not solubi lized by the fuel but are carried in the fuel.

8.4. CALIBRATION

Cal ibrat ion is a set of act ions that establ ishes that the inst rument being cal ibrated is equal to, or reports values equal to a standard. The unknown, the inst rument being cal ibrated, wi ll be checked against a known, the standard, at several di fferent points and adjustments made to the unknown to bring it into al ignment wi th the standard.

8.5. SAMPLE

Within this document the fol lowing concept is meant by the term “sample”. A sample is the spec if ic material to be prepared as specimens and exposed to test f luids. It is also the indiv idual fuel. For example, 100LL AvGas is a sample, and unleaded test fuel is a second sample.

8.6. SAMPLE SET

A sample set is all the indiv idual specimens and al l of the tes t fluids comprising a set of samples to generate a set of data. For example, f luid col lected f rom the 100LL on week 3 and f luid col lected f rom the unleaded fuel sample on Week 3 comprise the “Ambient Exposure, Week 3 Sample Set”.

8.7. SPECIMEN

Within this document the fol lowing concept is meant by the term “spec imen”.

Specimens are the individual pieces/aliquots collected f rom the sample materials .

For example the individual fuel volumes col lec ted f rom the test sample (the fuel) at each t ime interval are the test specimens for the ambient storage exposure.

Similarly , the individual glass rods are spec imens.

8.8. VALIDATION

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As opposed to cal ibrat ion, val idat ion is the act of document ing that an inst rument wi l l actual ly and cons istent ly give expected results . This may be done by measuring a specimen with a known value and conf i rming the ins t rument reports that value within the repeatabi lity of the ins t rument . If the expected value does not resul t, validat ion has fai led and some addit ional act ion must be taken to repair or adjust (calibrate) the inst rument.

9. FUEL CONFORMITY

9.1. TEST FUEL

Each PAFI test fuel shall be shown to conform to the complete spec if ication approved by the AFPO, as documented by a CoA furnished with each fuel batch or bulk volume del ivered by the fuel supplier to the tes t fac il ity. In addit ion, representat ive data must be generated by an independent 3rd party laboratory for specif ic pre- and post -test c riteria. Pre-test samples should be f rom fuel col lected f rom the original shipping containers ‘as received’ by the Test Faci li ty. Analysis must be performed on the fuel samples in accordance with Appendix A. Deviat ions f rom the fuel spec ification shall require approval of AFPO. The full Test Fuel CoA as well as the pre and post-tes t analys is spec if ied in Appendix A must be included in the test resul ts report .

NOTE: A five-gal lon retained sample of the test fuel ‘as received’ at the test fac il ity must be col lected and stored unt il complet ion of the PAFI tes t program.

See PAFI-FHP-001.

10. SAFETY PROCEDURES

This document does not purport to address all safety considerations. This document does not replace or supersede indiv idual inst rument documentat ion, Federal, State and local regulat ions, s ite procedures, or general indust ry practices. Appropriate safety precaut ions are the respons ibi lity of the Test Fac il ity conduct ing the test. The Test Faci li ty shal l es tablish and ensure compliance with the appl icable safety and health standards. The Test Fac il ity shal l establish and ensure compliance with the appl icable safety and heal th standards. Prior to init iation of tes t, each test set-up shal l be inspected for safe pract ices.

Cons ideration for personal protective gear (PPE) is the respons ibi lity of the Test Fac il ity .

10.1. SAMPLE FILL (REFERENCE ASTM D4057-12, SECTION 5.2)

For safety and protection of the integrity of the samples, during t ransportation and storage, the use of a sample carrier is recommended. A safe f il l of between 70- 85% volume is recommended unless otherwise inst ructed. Do not f i ll over 85% of the container volume.

10.2. STATIC CHARGE (REFERENCE ASTM D4057-12)

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10.2.1. GROUNDING (D4057-12, SECTION 5.4.1)

Fires and explos ions have occurred as a result of hydrocarbon vapors being ignited by stat ic elect rici ty. I f elect r ical charges are not grounded, they are unable to diss ipate and become “s tatic . ” This static elect ric charge can accumulate and f reely migrate to a s ingle point on the sample container by a difference in elect rical potent ial , then jump off as a high-energy spark discharge to a nearby less charged surface. The spark may be hot and prolonged enough to ignite nearby hydrocarbon vapors present above the lower explosive limit (LEL). This potential shall be managed by safely diss ipating static charges, and through proper grounding, when handl ing f lammable products. This inc ludes grounding the ambient storage test rigs and prov iding grounding during fuel f iltering as part of the laboratory tests .

10.2.2. PERSONAL ATTIRE (D4057-12, SECTION 4.5.2)

Footwear or clothing, capable of caus ing sparks, should not be worn during fuel handl ing activ it ies in which f lammable vapors are likely to be present .

Sampl ing should not be carried out during periods of atmospheric elect ric dis turbance or hai lstorms. To ground any stat ic charge on their body, the individual performing the handl ing should touch a grounded structure prior to handl ing fuel.

10.3. VAPOR HAZARDS

All testing must be done in compl iance with si te and local f i re safety protocols as wel l as applicable NFPA regulat ions. Appropriate vent ing of vapors generated during the elevated storage stabi lity test shal l be addressed.

10.4. PERSONAL PROTECTIVE EQUIPMENT (PPE)

This document does not replace or supersede any Federal, State, local or s ite specif ic requirements related to personal protect ive equipment . Technicians and test engineers are advised to fami liarize themselves with the safety data sheets (SDS) for al l of the f luids under test . Recognize that exposure at elevated temperatures may resul t in the concentration of blend components and appl icable PPE should be considered. Individuals are recommended to use at a minimum safety glasses or goggles, pet roleum resis tant gloves, and lab coats or aprons.

Note that fi re rated lab coats MAY NOT also be chemical resistant. Closed toed, non-charge isolating footwear is also recommended.

11. PRE-TEST REQUIREMENTS

11.1. SPECIMEN IDENTIFICATION

Specimens in this tes t plan are comprised of liquid fuels col lected f rom the bot tom of the ambient s torage stabi li ty fuel tank rig, samples collected f rom the elevated temperature storage s tabil ity r ig, and samples collected during laboratory test ing.

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In addit ion, glass rods and wooden dowels wi ll be col lec ted f rom the ambient storage stabi lity fuel tank rig.

I t is recommended that spec imen containers to be used to collec t the indiv idual specimens be marked with unique specimen ident if iers which are permanent ly aff ixed to the spec imen containers. The selected means of mark ing must not interfere wi th the c losure of the specimen container, and must not be removed by accidental contact with the sample material . Means of mark ing that have proven problematic in previous tes ting include labeling the glass surface of the container wi th permanent marker ( i.e. Sharpies™), as the tes t fluids inc luding av iat ion gasoline wi ll remove the mark ings. The use of taped labels has been successful as long as the marks were made prior to sampling and the tape was placed on the container prior to use. Other successful methods inc lude the attachment of a pre-marked metal tag wired to the container as long as the attaching wire was of a gage that did not interfere with the cap.

The glass rods and wooden dowels have been successful ly identif ied by using tubes constructed f rom threaded PVC pipes and caps and attaching permanent specimen ident if ication to the tubes.

11.2. PRE-EXPOSURE FUEL PREPARATION

11.2.1. AMBIENT STORAGE STABILITY TESTING

No special fuel preparat ion is required for the ambient storage stabi l ity test ing.

11.2.2. ELEVATED STORAGE STABILITY TESTING

Prior to tes ting, all of the fuel to be used for preparing the indiv idual 400mL specimens shal l be fi ltered us ing 0.8 µm fi lters. Fuel to be used to prepare the f ive-gallon sample for post -exposure CoA test ing does not require fi lt rat ion.

Cleaning Glassware and Equipment

1) Wash al l glassware to be used in f il tering the fuel and executing the exposure. Wash the equipment us ing the alkal ine washing procedure described in ASTM D4625. A summary of the process is prov ided below.

a. Soak the c lean equipment overnight in an alkaline detergent. Only touch the equipment after this point with laboratory forceps and clean gloves.

b. Af ter the overnight soak, r inse the glassware with dist il led water for a minimum of three rinses.

c. A llow the glassware to dry thoroughly in a laboratory oven at 100°C (212°F).

d. I f glassware is not to be used immediately, cover the glassware and segregate f rom other laboratory glassware.

Fi lter the solvents

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1) Fi lter each of the laboratory solvents (iso-octane, iso-propanol, and the 1:1:1 methanol:toluene:acetone f lushing fluid) through 0.45-micron fi lter membranes, using c leaned glassware, see Figure 2.

2) Use an aliquot of the f il tered solvent to prepare the s torage bott les for each solvent .

a. Rinse the concomitant 4L bottle inc luding the bott le threads and the l id.

b. Discard the rinsate.

c. The fi ltered solvent can now be s tored in the rinsed bott le.

d. Label the bott le as “Fil tered” and segregate f rom other laboratory chemicals. Store in compliance with local safety protocols.

Fi lter the fuel for test ing, (100LL and any tes t fuels)

1) When ready to fi lter the fuel samples, procure c lean, dry f ilt rat ion apparatus components and rinse with f il tered iso-propanol, followed by fi ltered f lushing f luid. Al low the fi lt rat ion apparatus to dry and cover to protect f rom ambient contamination. The apparatus inc ludes the f lask stoppers, the receiv ing flask, the f ilter support, and the fuel funnel.

2) Assemble the fi lt rat ion apparatus as shown in Figure 2 us ing a 0.8-micron membrane fi lter.

1Figure 2 - ASTM D4625 Filtration Apparatus

3) Carefully pour an al iquot of the fuel into the fuel funnel and s lowly turn on the vacuum. The fi ltered fuel is collected in the clean receiv ing flask.

1 Reprinted, with permission, from ASTM D4625-21, Standard Test Method for Middle Distillate Fuel Storage Stability at 43 °C (110 °F), copyright ASTM International. A copy of the complete standard may be obtained from www.astm.org.

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a. Continue to s lowly add fuel to the fuel funnel unt il suf fic ient fuel has been fi ltered to f il l al l of the sample jars for the 400 mL fuel exposure tests . This wil l be a minimum of 3 l iters of fuel; 400 mL x 7 samples (Week 0, 3, 6, 9, 12 and two spares).

4) Transfer 400 mL to each clean 500 mL sample jar as the fuel is f i ltered to minimize potent ial contamination. These jars shal l be sealed to prevent evaporat ion. Test ing shall commence within 48 hours of the fi ltrat ion.

5) Repeat s teps 1 through 4 for each addit ional fuel sample to be tes ted.

11.3. PRE-EXPOSURE BASELINE DATA

11.3.1. AMBIENT STORAGE STABILITY TESTING

1) At the t ime of test ing, col lec t a specimen of the fuel “as is. ” Measure the ambient water content of the test fuels by Karl Fischer Coulometric per ASTM D6304 and record the values. Because of the temperature dependence of water content, this spec imen shal l not be al lowed to warm or cool prior to the analys is. Immediate test ing is recommended. This wi ll be used for comparat ive analysis .

11.3.2. ELEVATED STORAGE STABILITY TESTING

1) Col lect pre-exposure insolubles and adherent data per ASTM D4625 on the T=0 f il tered fuel.

2) Col lect pre-exposure total acid number data on the f il tered or unf il tered fuel.

3) I f the suppl ied CoA does not include the data, collect vapor pressure, net heat of combustion, sulfur and hydrogen content , and ox idative stabil ity data on unf i ltered fuel.

11.4. PRE-EXPOSURE PHOTOGRAPHS

11.4.1. AMBIENT STORAGE STABILITY TESTING

Exemplar photographs of the ambient test ing glass rod and glass jar shal l be taken. I t is recommended that the set up for photographs include a repeatable backdrop/surface (white or blue), repeatable light ing, and the abil ity to repeat camera locat ion. It is recommended that a printed identif icat ion label be included in the photo that inc ludes sample identi ficat ion, and that i t is pre-exposure.

Note: Consider how the photos wi ll be collected at the tes t r ig when select ing the photography conditions.

11.4.2. ELEVATED STORAGE STABILITY TESTING

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Exemplar photographs of the fuel within the glass jar and the pressure vessel shall be taken.

Note: Depending on the color of the test fuel , it may be necessary to place a c lean glass sti r rod into the fuel to prov ide a focal point for the camera.

11.5. LABORATORY NOTEBOOK

Either a bound notebook or digital notebook shall be maintained for any exposure test ing. Technicians shal l record each indiv idual spec imen’s unique identi ficat ion, any lot or certif icat ion informat ion, and al l corresponding pre-exposure data. Each test and tes t method, as well as any equipment identi ficat ion shal l be recorded.

The tes t results report shal l document the manufacturer and model of any analyt ical equipment used. Informat ion related to the inst rument cal ibration or val idation shal l be recorded.

This notebook shall also be used to record any start times and dates, tes t condit ions such as temperature, v isual observations, and the t ime and date of test terminations.

Anomal ies, issues, troubleshooting, unplanned events , and any other observat ions shal l be recorded in the notebook. Final test data shall be recorded and pos it ively connected to the appropriate pre-exposure data.

12. TEST FACILITY & EQUIPMENT

12.1. FUEL DRUM TRANSFER VALVING

I t is assumed that the fuel samples wil l be stored and t ransferred us ing stainless steel drums. In order to dispense the fuel f rom the drums, the use of dedicated valves and drum vents shal l be used. Each valve and vent shal l be posi tively ident if ied and only used with the spec ific test fuel . Regardless of the receiving and storage methods employed, segregat ion of the fuels shal l be maintained throughout the fuel t ransfer and handl ing.

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Figure 3 - Dedicated Drum Vent and Valve (Notice Metal ID Tag)

12.2. AMBIENT STORAGE TESTING

With no exist ing industry accepted ambient storage test procedure, it is necessary to construct a test r ig and execute a protocol developed during Phase 1 PAFI test ing. This rig is comprised of a vented exterior drum which holds an internal aluminum test tank rig. In this aluminum tank, a collect ion of jars and glass rods are submersed in the test fuel for a total of 12 weeks with sampl ing occurring every three weeks. The ambient storage rig successfully des igned and constructed for the FAA PAFI test ing is shown schematically in Figure 4.

Figure 4 - Schematic of Ambient Storage Stability Test Rig (Courtesy of Purdue University)

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12.2.1. EXTERIOR STORAGE DRU MS

The external rig containment is comprised of a 55-gallon black, steel drum f itted wi th a vent , see Figure 5. The drum is black to maximize solar heating. The drum is an open head drum with a f itted l id c lamped into place wi th a spl it r ing. It is recommended cutting the spl it ring 180° f rom the spl it. Add an addit ional bol t f ixture so the ring can be released on both s ides and opened as two halves. This fac il itates opening the drum during rout ine inspections, see Figure 6.

Figure 5 - Exterior Storage Drum with Vent

Figure 6 - Cut to Split Ring and Additional Bolting Fixture

The drumhead shall be f itted with a vent. This vent may be made us ing aircraft tubing wi th a flared end and standard aircraft f i tt ings. The vent shal l have a bend so that the open end of the f lare is point ing downward. This allows the test r ig to “breathe” but prevents water such as rain f rom running direc tly into the rig.

A protect ive cover, such as a black t rash bag, may be used to minimize water accumulat ion on top of the drumhead, making opening the drum eas ier to open during the routine inspections. The protect ive cover shal l not be airtight and the vent shal l prot rude through the cover.

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The external 55-gallon drum prov ides st ructure and protection to the aluminum test tank which wi l l be placed ins ide of the exterior drum.

12.2.2. ALUMINUM OPEN H EAD DRUM WITH COVER

The aluminum fuel tank is represented wi th the use of an aluminum open head drum with a loose-fi tt ing lid (Figure 7) which is f itted into the external 55-gallon steel drum.

The drum is constructed to f it into the 55-gallon steel drum. The aluminum drum shal l be f itted with a supporting ring on the ins ide diameter on which the aluminum l id wi ll rest. The aluminum l id shall be constructed with a means of li ft ing the lid, such as loop handles. The lid is to be li fted off the aluminum tank rig at each routine inspect ion.

The aluminum l id shal l be fit ted with a representative airc raft fuel f i ller cap which acts as a material compatibi l ity test artic le.

Figure 7 - Interior Rig Test Tank with Lid

12.2.3. INNER STORAGE RACK

Throughout the tes ting, representat ive specimens of glass rods and jars of fuel wi l l be col lec ted and inspected. In order to support these specimens, an internal rack system capable of holding the minimum f ive glass rods and the minimum f ive wide mouth jars in a stable orientat ion and locat ions is required. An example is shown in Figure 8. In Figure 9, the loops at the top of the rack st ructure that wi ll support the glass rods can be seen.

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Figure 8 - Support Rack Interior to Test Rig Tank

Figure 9 - Loops to Support Glass Rods

12.2.4. STORAGE CONTAINMENT FOR C OLLECTED GLASS RODS AND D OWELS

At each routine sampling, one glass rod is removed and inspected. Following the inspect ion, the glass rod is to be col lec ted and stored. One means of holding and protecting, as well as prov iding pos it ive spec imen identi ficat ion of the glass rod is through the use of threaded PVC pipes with caps (Figure 10). Pos it ively ident ify ing the tubes wi th metal tags and bundl ing them into sample sets, i.e. al l

Loop Holding Rod

27 | P a g e PAFI-RTP-004 f ive 100LL glass rod tubes for the enti re exposure, has been successful ly used to improve the ease of handl ing and storage of the tubes.

S imilarly , a set of tubes for the wooden dowels used to t rack the fuel volume is recommended. The length of the tubes is determined by the length of the rods and dowels.

Figure 10 - PVC Threaded Pipes with Caps Bundled in Sample Sets

12.2.5. SPECIMEN JAR LIFTING RIG

In order to col lec t fuel bottoms, each ins tal led specimen jar shal l be l if ted st raight up and out of the test rig tank. This has been successfully accomplished by attaching a ring around the mouth of the jar and at taching st iff uprights which come above the surface of the fuel and can be grasped to l ift the jar (Figure 11).

The top of the li ft ing rig support wires are bent over to prov ide s tructure to l ift given the likely sl ipperiness of the wires. These “hooks” may also be used to secure the jar via the l ift ing rig to the interior support s truc ture. This wil l help prevent the jars being knocked over or upset due to inadvertent movement of the test rigs or due to movement caused during rout ine sample col lect ion.

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Figure 11 - Wide Mouth Jar Installed in Lifting Rig and Hooked to Interior Support Rack

12.2.6. DRUM STABILIZ ING STRUCTURE (FEET)

In order to provide posi tive stabi lity for the enti re rig, i t is recommended a three-legged s t ructure, into which the drum can be posi tively clamped in place, be constructed for each rig assembly. It is also recommended that this s t ruc ture be posit ively attached to ground, for example bol ted into the concrete. This wil l help prevent inadvertent movement of the drums during tes ting and wi l l prov ide a point for grounding the drums. The s tructure may act as the ground point as long as there is a continuous path f rom the drums, to the feet, and to the grounding rod.

Figure 12 shows an example of the stabil izing feet si tt ing upright. The c ircle represents the location of the drum when installed in the structure. Figure 13 shows the drum rig instal led into the s tabil iz ing feet .

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Figure 12 - Stabilizing Feet (Graphic Indicates Location of Drum within the Feet).

Figure 13 - Drum Installed into Stabilizing Feet

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12.2.7. CONTROLLED ACCESS SPACE

In order to meet the objectives of the ambient tes ting, a locat ion which receives sun for the majori ty of the day is required. The locat ion shal l provide posit ive control on access to the drums to prevent interrupt ions, unauthorized access, or movement of drums. This control shall be in place for the enti re 12-week (3 month) period.

Space shal l be suff icient to allow orientation of the drums such that the shadows f rom one drum onto another are minimized.

12.2.8. AMBIENT WEATHER MONITORING EQUIP MENT

A means of measuring and recording the dai ly ambient weather condit ions is required. The data collected shal l include: high and low air temperatures, high and low barometric pressure, wind speed and direct ion, high and low relative humidity, and amount of prec ipitat ion. The weather data shall be collected at the locat ion of the test ing. I f the test ing is performed at or immediately adjacent to an airport location, the daily NOAA data for that ai rport is acceptable.

12.3. ELEVATED (ACCELERATED) STORAGE TESTING

12.3.1. ELEVATED TE MP ERATURE CONTROLLED AREAS – OV ENS

The tests in this document require temperature-controlled environments capable of maintaining temperatures to ±3 °C.

Any elevated temperature spaces used for heating samples shal l not have exposed heat ing elements or ignit ion sources. Considerations shal l include venti lat ion of hazardous or flammable vapors. Temperature recorders are not required but a means of monitoring actual temperatures through a test is required.

Local f i re safety regulat ions may l imit the total volume of flammable liquids that may be stored in a space, espec ial ly at elevated temperatures or in personnel occupied spaces. Elevated tes ting requires approx imately s ix gal lons total volume of each fuel to be heated.

12.3.2. ASME STAINLESS ST EEL PRE SSURE VE SS ELS WITH FLUOROCA RBON

SEALS

Previous tes ting successful ly used ASME wide-mouth, stainless steel pressure vessels f itted with spec ial order f luorocarbon (Vi ton™) seals to perform the elevated temperature storage s tabil ity test ing. A large volume pressure vessel is required to produce the required 5 gal lons of aged fuel. To maintain a 5:4 fuel:ai r rat io required for the exposure and to produce the required 5 gal lons requires a one-gal lon and a f ive-gallon pressure vessel for each fuel. The pressure vessel may be f itted with multiple ports, but al l ports must be capped.

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Figure 14 - One Gallon ASME Pressure Vessel

12.3.3. 500ML (1 PINT) GLASS JARS

In order to produce the aged spec imens to be tested over the 12-week (3 month) elevated temperature storage s tabil ity tes ting, 500mL (1 pint ) jars are required.

The jars are fi lled with 400mL of sample. Prev ious testing successful ly used wide mouth, pint canning jars. When fi l led with 400mL of sample, the resulting fuel:ai r rat io was calculated to be 5:4. Any glass jar with compat ible l id may be used, however it may be necessary to recalculate the fuel :ai r rat io and dupl icate i t in the stainless s teel pressure vessels used to prepare 5 gallons of aged fuel.

12.4. KARL FISCHER MOISTURE METER – COULOMETRIC

A Karl Fischer ti t rator and concomitant chemicals are required to determine the moisture content of the samples. Test ing is to be performed per ASTM D6304.

Depending on the chemist ry of the test fuel, reagents for aldehyde/ketone samples, or an addit ional oil dryer accessory , see D6304, Procedure C, for amine containing fuels may be required.

12.5. CALIBRATED / VALIDATED LABORATORY MEASURING EQUIPMENT

Testing and measuring require standard laboratory equipment which has been cal ibrated or val idated as appropriate. This lis t of equipment does not exclude others. Any equipment which has cal ibration shal l have the date of the latest cal ibration recorded. For inst ruments using val idation measurements, the resul ts of the validation shal l be recorded and the means of rect ifying any non-compl iant equipment documented.

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Instrument Report Reference

Thermometer/thermocouples Cal ibrat ion -

Electronic Balance Cal ibrat ion

Weather station Cal ibrat ion

12.6. ASTM D4625/D5452 VACUUM FILTER APPARATUS

In order to properly f ilter the fuel and solvents used in the ASTM D4625 Fuel Storage Stabi l ity testing, as wel l as determining f i lterable sol ids, and part iculate contaminat ion, a vacuum fi lter apparatus is required. This inc ludes a fi lter funnel , a metal c lamp, a f ilter support assembly , and a laboratory vacuum.

2Figure 15 - ASTM D4625-14 Vacuum Filter Apparatus

12.7. OTHER SPECIALTY EQUIPMENT

Other support materials required inc lude but are not limi ted to:

1) Sar-Gel Water Indicat ing Paste

2) Glass Sti r Rods

3) Reagent grade laboratory chemicals fi ltered with 0.8 µm f i lter paper

a. Isooctane

b. Isopropanol

c. Toluene

d. Acetone

2 Reprinted, with permission, from ASTM D4625-21, Standard Test Method for Middle Distillate Fuel Storage Stability at 43 °C (110 °F), copyright ASTM International. A copy of the complete standard may be obtained from www.astm.org.

33 | P a g e PAFI-RTP-004

e. Methanol

4) Nylon fi lter membranes; 0.8 µm

5) One-gal lon stainless steel cans, a total of f ive for each test fuel

6) Five-gallon s tainless s teel cans, a total of one for each test fuel

13. TEST WITNESSING

Test witnessing is required for the collec tion and report ing of data collec ted in compl iance with this test plan. This data is to be used by the FAA as part of their evaluat ion for f leet wide authorization. Fuel formulators shall submit a test plan for approval by the FAA before execut ing tes ting. Part of the submitted test plan must be a means of test witness ing by an FAA authorized representative.

Testing performed in accordance with an approved test plan shal l be witnessed by a representative of the FAA AFPO or their designated representat ive.