DOT/FAA/TC-14/11 General Aviation Engine Fleet Federal Aviation Administration William J. Hughes Technical Center Assessment for Octane Aviation Research Division Atlantic City International Airport Requirement New Jersey 08405 July 2014 Final Report This document is available to the U.S. public through the National Technical Information Services (NTIS), Springfield, Virginia 22161. This document is also available from the Federal Aviation Administration William J. Hughes Technical Center at actlibrary.tc.faa.gov. U.S. Department of Transportation Federal Aviation Administration NOTICE This document is disseminated under the sponsorship of the U.S. Department of Transportation in the interest of information exchange. The U.S. Government assumes no liability for the contents or use thereof. The U.S. Government does not endorse products or manufacturers. Trade or manufacturers’ names appear herein solely because they are considered essential to the objective of this report. The findings and conclusions in this report are those of the author(s) and do not necessarily represent the views of the funding agency. This document does not constitute FAA policy. Consult the FAA sponsoring organization listed on the Technical Documentation page as to its use. This report is available at the Federal Aviation Administration William J. Hughes Technical Center’s Full-Text Technical Reports page: actlibrary.tc.faa.gov in Adobe Acrobat portable document format (PDF). Technical Report Documentation Page 1. Report No. 2. Gov ernment Accession No. 3. Recipient's Catalog No. DOT/FAA/TC-14/11 4. Title and Subtitle 5. Report Date GENERAL AVIATION ENGINE FLEET ASSESSMENT FOR OCTANE July 2014 REQUIREMENT 6. Perf orming Organization Code 7. Author(s) 8. Perf orming Organization Report No. Herbert W. Schlickenmaier1, Ronald Wilkinson2, and David Atwood3 E001-006-TR-2013-001 9. Perf orming Organization Name and Address 10. Work Unit No. (TRAIS) 1 Crown Consulting, Inc. 2 AvSouth LLC 3 Federal Aviation 1400 Key Blvd, Ste 1100 for Crown Administration William J. Arlington, VA 22209 Consulting, Inc. Hughes Technical Center 12129 Scenic Airport and Aircraft Safety R&D View Dr. Group Flight Technology Team Mobile AL Atlantic City International 36695 Airport, NJ 08405 11. Contract or Grant No. DTFAWA-10-A-00085-0005 12. Sponsoring Agency Name and Address 13. Ty pe of Report and Period Cov ered U.S. Department of Transportation Final Report Federal Aviation Administration, New England Regional Office 12 New England Executive Park Burlington, MA 01803 14. Sponsoring Agency Code AIR-002 15. Supplementary Notes The Federal Aviation Administration William J. Hughes Technical Center Aviation Research Division COR was David Atwood. 16. Abstract This report supports the recommendations of the Unleaded Avgas Transition Aviation Rulemaking Committee for a high-octane unleaded fuel; it is the technical (but not the only) basis on which options can be addressed as contingencies for lower octane unleaded fuels to be inserted into the fleet as replacement for the current tetraethyl lead A VGA S currently used in general aviation. This report assesses the ability of the aircraft fleet to accommodate lower octane fuels with both low-octane drop-in replacement unleaded fuel and the necessary interventions to accommodate lower octane fuels with operational or engineering interventions. Further, it indicates which engines may require major modifications to accommodate lower octane unleaded fuels. The report uses publicly available engine performance data (compression ratio, brake mean effective pressure, cylinder head temperature, bore diameter, and stroke, as well as information regarding whether the engine is naturally aspirated or turbocharged) to document the ability of the U.S. piston-engine fleet to move to lower octane by direct application and—when direct application cannot be accommodated—to characterize the operational or engineering interventions that would allow operation using lower octane unleaded fuel. The focus is on the U.S. piston-engine fleet, but the methodology is applicable worldwide. This report does not address the technical or financial feasibility of attempting a certification process for any potential operational or engineering modification. The use of the Aircraft Registry Database described in DOT/FAA/AR-TN11/22 “Aviation Fules Research Reciprocating Engine Aircraft Fleet Fuel Distribution Report,” was repurposed to include the population of engines, as well as incorporating the engine performance data from the associated engine type certificate data sheet. 17. Key Words 18. Distribution Statement This document is available to the U.S. public through the Piston, Aircraft, Aviation, Unleaded, Engine parametric, National Technical Information Service (NTIS), Springfield, Octane, Minimum approved octane, General aviation, Fleet, Virginia 22161. This document is also available from the 100LL, AVGAS Federal Aviation Administration William J. Hughes Technical Center at actlibrary.tc.faa.gov. 19. Security Classif . 20. Security Classif . 21. No. of Pages 22. Price Unclassified Unclassified 404 Form DOT F 1700.7 (8-72) Reproduction of completed page authorized TABLE OF CONTENTS Page EXECUTIVE SUMMARY x 1. INTRODUCTION 1 1.1 Focus on Fleet Distribution of Approved Octane 1 1.2 Focus for the Parametric Study on Ke y Emp ir ic a l Data 2 1.3 Addressing the Breadth of Intervention Strategies 2 1.4 Summary 3 2. FLEET DISTRIBUTION OF APPROVED OCTANE 3 2.1 Data Source for the Analysis: Aircraft Approved F uels 3 2.1.1 Review of the Aircraft-Focused Database 4 2.1.2 Data Insights From the Aircraft Approved Fuels 7 2.1.3 Applying Aircraft Approved Fuels Methods as a Foundation for Engine Analyses 8 2.2 Integrating the Engine TCDS Data With Their Respective Aircraft 8 2.2.1 Key Engine Parameters for Analysis 9 2.2.2 Ensuring the Integrity of the Engine Parameters and the Utility of the Resulting Insights 9 2.3 Insights From the Population Data 11 2.4 Population Densities by Engine Parameters 12 2.4.1 Detailed View of Population Density for 80/87 12 2.4.2 Detailed View of Population Density for UL91 13 2.4.3 Detailed View of Population Density for 91/96L 14 2.4.4 Detailed View of Population Density for 100LL, NA 15 2.4.5 Detailed View of Population Density for 100LL, TC 16 2.4.6 Observations of the Detailed View of Population Density for All Fuels 17 3. KEY EMPIRICAL DATA—ASSESSMENT OF METRICS AND INDICES AS DISCRIMINATORS OF ENGINE OCTANE REQUIREMENT 18 3.1 The National Advisory Committee for Aeronautics Archives Reviewed for Relevant Data and Engine Textbooks Researched fo r Knock-Specific Indices 18 iii 3.2 Preliminary Knock Sensitivity Metrics Research of Data, Reports, and Archives 19 3.3 Grouping of Engines for Reduced Octane Assessment 20 3.4 Engine Models Approved for Minimum Grade UL91 AVGAS 21 3.5 Preliminary Assessment of the Effect of Changes to Limitations/Hardware on Engine Octane Requirement 26 3.6 Assessment of Maximum Allowable MAT Continental TC Models 26 3.6.1 Continental TC Engines Maximum Allowable MAT vs. BHP 30 3.7 Continental TC Engines Maximum Allowable MAT vs. BMEP x ρo/ρi 32 3.8 Assessment of Maximum Allowable MAT, Lycoming TC Models 33 3.9 Generic TC Engine MAT at Altitude, With and Without Intercooler 37 3.9.1 Assumptions 37 3.10 Continental Model TSIO-550-E,-K TC Engine MAT at Altitude With Dual Large Intercoo le rs 39 4. ADDRESSING THE BREADTH OF INTERVENTION STRATEGIES 40 4.1 The NA Engines 41 4.2 The TC Intercooled Engine Octane Enabling Candidate Adjustments 42 4.3 The TC Non-Intercooled Engine Octane Enabling Candidate Adjustments 43 5. CONCLUSIONS AND RECOMMENDATIONS 44 5.1 Fle et Distribution of Approved Octane 44 5.2 Key Empirical Data—Assessment of Metrics and Indices as Discriminators of Engine Octane Requirement 44 5.3 Addressing the Breadth of Intervention Strategies 45 5.4 Recommendations 45 6. REFERENCES 46 iv APPENDICES A—The Brake Mean Effective Pressure and Compression Ratio for Aircraft and Engines Approved for 80 Octane B—The Brake Mean Effective Pressure and Compression Ratio for Aircraft and Engines Approved for Unleaded 91 C—The Brake Mean Effective Pressure and Compression Ratio for Aircraft and Engines Approved for 91 Leaded D—The Brake Mean Effective Pressure and Compression Ratio for Aircraft and Engines Approved for Naturally Aspirated 100LL E—The Brake Mean Effective Pressure and Compression Ratio for Aircraft and Engines Approved for Turbocharged 100LL F—List of Aircraft and Engines for Which No Valid Brake Mean Effective Pressure or Compression Ratio Is Availab le v LIST OF FIGURES Figure Page 1 Criteria Used to Select the Airworthy Aircraft for the Fleet Distribution 4 2 Distribution of Aircraft Approved Fuels and Validated Engine Parameters for the Associated Approved Fuel 11 3 Population Density for 80/87 12 4 Population Density for UL91 13 5 Population Density for 91/96L 14 6 Population Density for 100LL, NA 15 7 Population Density for 100LL, TC 16 8 Population Density for All Fuels 17 9 Engine Models Currently Approved for Minimum Grade 91 AVGAS 24 10 Typical Installed Induction Air Temperatures for NA Engines 25 11 Continental TC Engines, Maximum Allowable MAT °F vs. BHP 31 12 Continental TC Engines, Maximum Allowable MAT °F vs. BMEP 31 13 Maximum MAT °F vs. Density-Adjusted BMEP 32 14 Maximum Allowable MAT °F vs. Charge Air Temperature Adjusted BMEP 33 15 Maximum Allowable MAT °F vs. BMEP 37 16 Generic TC Engine at 40 MAP Estimate of MAT at Rated Power Hot Day at Altitude, With and Without Intercooler