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<p class=”article-category”><strong>Knowledge Centre | Testing Explained</strong></p>

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<h1 class=”wp-block-heading”>Powerplant Fire Testing Standards: From FAA Report 3A to AS6826</h1>

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<p class=”article-standfirst”><strong>Powerplant fire testing has changed substantially over the past six decades.</strong> What began as a standard apparatus and procedure for testing flexible aircraft hose assemblies developed into a broader engineering discipline built around calibrated thermal severity, representative installation conditions, defined safety functions and defensible certification evidence.</p>

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<p>The journey from FAA Powerplant Engineering Report No. 3A to SAE AS6826 is not simply a history of burner designs. It is the story of how aerospace fire testing moved from hardware-based instruction towards a more repeatable, performance-focused and hazard-led approach.</p>

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<p>The history of powerplant fire testing is the history of aerospace engineering moving from prescribed hardware towards controlled performance and safety-focused evidence.</p>

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<p class=”brand-message”><strong>Your Test Facilitator. Not simply a test facility.</strong></p>

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<h2 class=”wp-block-heading”>Executive Summary</h2>

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<p>FAA Powerplant Engineering Report No. 3A established a standard fire-test apparatus and procedure for flexible aircraft hose assemblies. Its approach combined a severe flame with operational influences including fluid pressure, fluid flow, elevated fluid temperature, vibration, controlled airflow and representative mounting.</p>

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<p>When the original modified Lennox OB-32 burner became unavailable, the challenge was not merely to find another burner that looked similar. Industry needed replacement equipment capable of reproducing the established thermal environment.</p>

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<p>FAA-RD-76-213 helped characterise the reference flame and assess alternative modified burners. This strengthened an important principle: burner acceptability depends on configuration, operating settings, geometry and measured performance, not model identity alone.</p>

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<p>The technical development continued through the revised Engineering Report No. 3A, SAE AS1055, SAE AIR1377, ISO 2685 and FAA AC 20-135. In April 2025, SAE issued AS6826 to provide a more structured framework for powerplant and auxiliary power unit fire testing. FAA AC 20-135A subsequently recognised AS6826 as an acceptable means of compliance for applicable powerplant fire-protection requirements.</p>

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<h2 class=”wp-block-heading”>In This Article</h2>

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<li>#evolutionThe evolution in one minute</a></li>

<li>#why-fire-testing-existsWhy powerplant fire testing exists</a></li>

<li>#report-3aThe origins of Engineering Report No. 3A</a></li>

<li>#classificationsFire resistant and fireproof</a></li>

<li>#burner-problemThe burner availability problem</a></li>

<li>#faa-rd-76-213FAA-RD-76-213 and performance-based thinking</a></li>

<li>#report-3a-revisionThe 1978 revision of Report 3A</a></li>

<li>#qualification-verificationQualification and routine verification</a></li>

<li>#sae-standardsSAE AS1055 and AIR1377</a></li>

<li>#iso-2685ISO 2685 and international practice</a></li>

<li>#ac-20-135AC 20-135 and certification objectives</a></li>

<li>#as6826SAE AS6826 and the modern framework</a></li>

<li>#why-history-mattersWhy this history still matters</a></li>

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<h2 class=”wp-block-heading” id=”evolution”>The Evolution in One Minute</h2>

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<th>Period</th>

<th>Development</th>

<th>Central contribution</th>

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<td>1961</td>

<td>FAA Powerplant Engineering Report No. 3A</td>

<td>Established a standard apparatus and procedure for flexible aircraft hose fire testing.</td>

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<td>Mid-1970s</td>

<td>Original Lennox burner became unavailable</td>

<td>Created a burner-equivalence, availability and repeatability problem.</td>

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<td>1977</td>

<td>FAA-RD-76-213</td>

<td>Characterised the original burner and assessed alternative modified burner configurations.</td>

</tr>

<tr>

<td>1978</td>

<td>Revised Engineering Report No. 3A</td>

<td>Formalised alternative burner arrangements and performance controls.</td>

</tr>

<tr>

<td>Later industry development</td>

<td>SAE AS1055 and SAE AIR1377</td>

<td>Applied related hose-test and fire-test equipment principles through recognised industry documents.</td>

</tr>

<tr>

<td>International development</td>

<td>ISO 2685</td>

<td>Provided an international fire-test framework for aircraft components, equipment and structures in designated fire zones.</td>

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<tr>

<td>FAA certification guidance</td>

<td>AC 20-135 and Change 1</td>

<td>Connected fire-test methods with wider powerplant installation and certification objectives.</td>

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<tr>

<td>2018</td>

<td>FAA tasking to SAE</td>

<td>Initiated development of a more harmonised powerplant fire-test standard.</td>

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<tr>

<td>April 2025</td>

<td>SAE AS6826 issued</td>

<td>Established a more prescriptive framework for planning, calibration, boundary conditions and acceptance.</td>

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<tr>

<td>September 2025</td>

<td>FAA AC 20-135A issued</td>

<td>Recognised AS6826 as an acceptable means of compliance for relevant powerplant fire-protection requirements.</td>

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<figcaption class=”wp-element-caption”>A simplified timeline of major developments in aerospace powerplant fire testing.</figcaption>

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