EPFD-02-02 System Requirements Document.pdf

EPFD-02-02

Uncontrolled when printed. The electronic version is the official approved document.

National Aeronautics and Space Administration

Electrified Powertrain Flight Demonstration (EPFD) Project

System Requirements Document (SRD)

Date: February 21, 2021

EPFD System Requirements Document (SRD) Document No: EPFD-02-02 Revision: Rev A Effective Date: February 21, 2021 Page iv

TABLE OF CONTENTS

1.0 INTRODUCTION

1.1 Purpose

1.2 Scope

1.3 Applicability

1.4 Change Authority and Responsibility

2.0 RELATED DOCUMENTATION

2.1 Applicable Documents

2.2 Reference Documents

3.0 SYSTEM DESCRIPTION

3.1 Ground Tests and Demonstration

3.2 EPFD Flight Demonstration

3.3 Requirements Trace

3.4 Verification of NASA driving requirements and system requirements

4.0 EPFD SYSTEM REQUIREMENTS

4.1 Requirements that Primarily Support Driving Requirement 1

SRD-01 - EPFD Transport Mission Types

SRD-02 - Flight Test Environment

SRD-03 - Removed

4.2 Requirements that Primarily Support Driving Requirement 2

SRD-04 - Flight Test Demonstration of high voltage Integrated MW-class powertrain systems

SRD-05 - Flight Test Demonstration of high power Integrated MW-class powertrain systems

SRD-06 – Electromagnetic Interference (EMI) and Electromagnetic Compatibility

(EMC) 12

SRD-07 – Demonstrate an Energy Storage System

SRD-08 - EPFD Propulsion during Flight Phases

4.3 Requirements that Primarily Support Driving Requirement 3

SRD-09 - EPFD Crewed Flight Testing

SRD-10 - Removed

SRD-11 – Industry Partner Proposed Airworthiness Process

Effective Date: February 21, 2021 Page v

SRD-12 - Environmental Testing

SRD-13 - Structural Airworthiness Requirements

SRD-14 – Software Requirements

4.4 Requirements that Primarily Support Driving Requirement 4

SRD-15 - First Flight No Later Than Date

4.5 Requirements that Primarily Support Driving Requirement 5

SRD-16 - Thermal Management System

SRD-17 - Hot and Cold Day Operations

4.6 Requirements that Primarily Support Driving Requirement 6

SRD-18 - Fault Control System

4.7 Requirements that Primarily Support Driving Requirement 7

SRD-19 - Obtain Integrated MW-class Powertrain Test Data In-Flight

SRD-20 - Removed

SRD-21 - Removed

4.8 Requirements that Primarily Support Driving Requirement 8

SRD-22 – Identify Gaps & Develop Approaches to Closing the Gaps Prioritized in Regulations and Standards Gap Analysis

SRD-23 - Removed

4.9 Requirements that Primarily Support Driving Requirement 9

SRD-24 - Obtain Integrated MW-Class Powertrain Ground Test Data

SRD-25 - EPFD Ground Testing for TRL maturation

SRD-26 - System Performance Analysis and Model Data

APPENDIX A EPFD PROJECT NEEDS, GOALS AND OBJECTIVES

A.1 EPFD Project Need

A.2 EPFD Project Goals

A.3 EPFD Project Objectives

APPENDIX B EPFD VERIFICATION MATRIX

APPENDIX C EPFD TRACEABILITY MATRIX

APPENDIX D EPFD ALLOCATION MATRIX

APPENDIX E ACRONYMS

APPENDIX F TO BE DETERMINED AND TO BE RESOLVED ITEMS

Effective Date: February 21, 2021 Page vi

List of Figures

Figure 1 - EPFD Project Internal Requirements Flow Figure 2 - Industry Requirements Flow in Response to NASA EPFD Requirements

List of Tables

Table 1 - ARMD Strategic Thrust 3 and Critical Commitment 3.1 Table 2 - List of Applicable Documents Table 3 - List of Reference Documents Table 4 - Driving Requirements Table 5 - ARMD Needs from NASA Critical Commitment Table 6 -SRD Verification Matrix Table 7 - EPFD Verification Methods Table 8 - EPFD Traceability Matrix Table 9 - EPFD Allocation Matrix Table 10 - List of Acronyms Table 11 - To Be Determined Items Table 12 - To Be Resolved Items

Document No: EPFD-02-02-SRD Revision: Rev A Effective Date: February 21, 2021 Page 2

1.1 Purpose

The purpose of this document is to describe the system-level requirements for the EPFD Project for development of integrated MW-class powertrain technologies. The EPFD System Requirements Documents is a companion document to the EPFD Statement of Objectives (SOO). In the SOO, the EPFD Project is stating why the data we are asking for is important to NASA, and how the SOO meets NASA ARMD’s Critical Commitment to accelerate MW-class powertrains to the aviation commercial market.

The EPFD Project will share this Systems Requirements Document with the Industry Partners so they can understand the criteria NASA is using, internal to the Project, to assess/verify whether the contractor provided SRD, and subsequent data that are provided, meets NASA’s objectives in the SOO, and ARMD’s Critical Commitment.

1.2 Scope

The scope of this document covers the system-level requirements of the EPFD Project ground and flight demonstrations of integrated MW-class powertrain systems and technologies. The nature of the project is such that the details of the system, including functions, interfaces and operations will be proposed by an Industry Partner. The EPFD system-level requirements trace to the EPFD Project goals and objectives, SOO, standards, airworthiness and technical data.

The EPFD system-level requirements link NASA and Community Stakeholder needs to the project’s goals and objectives.

The terms “shall,” “will,” and "should” are used with specific intent within the requirement statements and are defined as follows:

"Shall": Used indicate a binding and require formal verification of a requirement.

"Will": Used to indicate a statement of fact or express intent, are non-binding, and therefore do not require formal verification of a requirement.

"Should": Used to indicate a desired goal and does not require formal verification of a requirement.

1.3 Applicability

The requirements in this document are applicable to the EPFD Project and the Industry Partners. These requirements are applicable for the entire project lifecycle including demonstrations during the EPFD Project. They are not specifically applicable to the vision vehicle as its capabilities will likely exceed the requirements in this SRD. The Industry Partner shall supply a System and Subsystem Requirements Document (DRD-SE-03) and an aircraft system that is responsive to the Driving Requirements (DR) and System Requirements in this document. These Industry Partner documents shall be representative of the requirements and features that are appropriate for their integrated MW-class powertrain system and trace to this

SRD.

1.4 Change Authority and Responsibility

This document will follow the EPFD Configuration and Data Management Plan (EPFD-01-04).

Any changes after baseline will go through a Configuration Control Board review and an approval process.

Effective Date: February 21, 2021 Page 3

2.0 RELATED DOCUMENTATION

This section lists additional, related documents. Section 2.1 lists the applicable documents.

Section 2.2 lists recommended reference documents for information purposes.

2.1 Applicable Documents

Table 2 lists documents that are specifically called out in this document. The following documents include specifications, models, standards, regulations, guidelines, handbooks, and other special publications. The documents listed in this section are applicable to the extent specified herein.

Table 2 - List of Applicable Documents

Document Number Document Title

NPR 7123.1C NASA Systems Engineering Processes and Requirements

AFOP-7900.3-023,

Revision G

Airworthiness and flight safety review process (NASA Armstrong Flight Research Center [AFRC] document)

AFG-7123.1-001 Aircraft Structural Safety of Flight Guidelines NPR 7900.3D NASA Aircraft Operations Management

RTCA DO-160

Environmental Conditions and Test Procedures for Airborne Equipment

RTCA DO-178C

Software Considerations in Airborne System and Equipment Certification

RTCA DO-254 Design Assurance Guidance for Airborne Electronic Hardware

AFOP-7900.3-004

Environmental Acceptance Testing: Electronic & Electromechanical Equipment (NASA AFRC document)

NASA TM X-64970

Hot, Cold, And Annual Reference Atmospheres for Edwards Air Force Base (EAFB), California (1975 Version)

NASA-STD-8739.8 NASA Software Assurance and Software Safety Standard 14 Code of Federal Regulations (CFR) 23

Airworthiness Standards: Normal Category Aircraft

14 CFR 25 Airworthiness Standards: Transport Category Airplanes 14 CFR 33 Airworthiness Standards: Aircraft Engines 14 CFR 35 Airworthiness Standards: Propellers

EPFD-01-03 Integrated Data Requirements Deliverables Document

EPFD-02-06 EPFD Technical Measures of Effectiveness

EPFD SOO EPFD Statement of Objectives

SAE AS210

Definition of Commonly Used Day Types (Atmospheric Ambient Temperature Characteristics Versus Pressure Altitude)

Effective Date: February 21, 2021 Page 4

2.2 Reference Documents

Table 3 list documents that contain supplemental information to guide the user in the application of this document. The following documents include specifications, models, standards, guidelines, handbooks, and other special publications. The documents listed in this section are applicable to the extent specified herein.

Table 3 - List of Reference Documents

Document Number Document Title EPFD-01-05-TDP Technology Development Plan (TDP) EPFD-01-22 Data and Intellectual Property Management Plan MIL-HDBK-310 Global Climatic Data for Developing Military Products MIL-STD-461G Requirements For The Control Of Electromagnetic Interference

Characteristics Of Subsystems And Equipment

3.0 SYSTEM DESCRIPTION

The EPFD Project procurement strategy is to contract with industry to mature integrated MW-class powertrain system technology, integrate a MW-class powertrain onto an aircraft for flight demonstrations, and conduct ground and flight testing to meet the stakeholder’s expectations.

Due to the procurement strategy, there is no formal NASA system architecture, the system architecture is “owned” by the Industry Partners(s).

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3.1 Ground Tests and Demonstration

The EPFD Industry Partner(s) will conduct ground tests and demonstrations of integrated MW-class powertrain system components and integrated systems to mature technology prior to flight demonstrations. It is anticipated that ground demonstrations will occur at Industry Partners’ facilities or NASA’s facilities. Ground demonstrations should be carried out by Industry Partners in appropriate test facilities, per their approach and schedule, to meet requirements and incrementally demonstrate MW-class powertrain components and technology capabilities.

3.2 EPFD Flight Demonstration

The EPFD Project intends to award contracts for at least two flight demonstrations to mature integrated MW-class powertrain system technology. The EPFD integrated MW-class powertrain system flight test aircraft will be Industry owned and operated. The integrated MW-class powertrain system will fly at altitudes and speeds representative of commercial aviation routes.

The EPFD integrated MW-class powertrain system flight test aircraft will be integrated with a MW-class electrified propulsion system which consists of subsystems that convert electrical power to aerodynamic thrust. The powertrain system will be integrated with existing primary propulsion system(s) and flight test aircraft. EPFD subsystems will include MW-class motors/generators, power transmission, thermal management, control system, inverters/converters, batteries and turbomachinery. The EPFD flight test aircraft can use

Effective Date: February 21, 2021 Page 5 integrated MW-class powertrain systems during any phase of ground and flight operations where these systems are required for the Industry Partners’ Vision Vehicle.

3.3 Requirements Trace.

The requirements trace up to the EPFD Project Needs, Goals, and Objectives which are found in EPFD-01-10 and are referenced in Appendix A. A number of Driving Requirements have been identified. Driving Requirements are stated in EPFD-01-10 and listed below along with the verification method that will be used by NASA to verify each requirement.

Table 4 - Driving Requirements

Driving Requirement NASA Verification Method

DR 1: The EPFD integrated MW-class powertrain system ground and flight demonstration(s) shall reduce barrier technical risks associated with the system to enable U.S.

Industry to be first to market with an EAP based Vision Vehicle Product.

Analysis

DR 2: The EPFD integrated MW-class powertrain system flight demonstration(s) shall demonstrate in flight high voltage operation at all relevant ground and flight conditions.

Analysis

DR 3: The EPFD integrated MW-class powertrain system flight demonstration(s) shall conduct crewed (human rated) flight operations and testing.

Inspection

DR 4: The EPFD integrated MW-class powertrain system flight demonstration(s) will attempt to conduct first flight by 2023 and shall conduct first flight no later than August 2024.

Inspection

DR 5: The EPFD integrated MW-class powertrain system flight demonstration(s) shall demonstrate in flight a thermal management system for the electrical power system.

Analysis

DR 6: The EPFD integrated MW-class powertrain system flight demonstration(s) shall demonstrate in flight a control system which manages electrical faults while maintaining fail-safe aircraft operations.

Analysis

DR 7: The EPFD integrated MW-class powertrain system flight demonstration(s) shall measure the performance of the system against the Technical Performance Measures (TPMs) – Reference EPFD-02-06 Table 7 for TPMs.

Analysis

DR 8: The EPFD integrated MW-class powertrain system flight demonstration(s) shall provide ground and flight test data to address gaps in regulations and standards associated with deployment of the integrated MW-class powertrain on the EAP Vision Vehicle.

Analysis

DR 9: The EPFD integrated MW-class powertrain system flight demonstration(s) shall acquire ground and flight data used to validate NASA modeling tools and research.

Analysis

Effective Date: February 21, 2021 Page 6

The EPFD requirements flow down is seen below in Figure 1. The EPFD Project needs, goals and objectives are referenced in Appendix A.

Figure 1 - EPFD Project Internal Requirements Flow

Additional detail for some of the requirements in the EPFD Systems Requirements Document are provided in the Data Requirements Deliverables (DRDs) and the Request for Proposal

(RFP).

Effective Date: February 21, 2021 Page 8

Many of the system requirements reference the Technical Performance Measures which can be found in EPFD-02-06: EPFD Technical Measures of Effectiveness.

3.4 Verification of NASA driving requirements and system requirements

The NASA EPFD team will verify the driving requirements and system requirement using analysis and inspection methods from data that are produced by the Industry Partner and provided to NASA during project execution. Each requirement specifies the verification method that will be used by NASA to verify the EPFD system requirements as well as a method that NASA recommends that the Industry Partner use to verify each requirement. The actual verification methods used by the Industry Partner may vary. Table 7 defines the verification methods.

4.0 EPFD SYSTEM REQUIREMENTS

This section contains the EPFD system level requirements.

4.1 Requirements that Primarily Support Driving Requirement 1

The following requirements are primarily traceable to DR 1: The EPFD integrated MW-class powertrain system ground and flight demonstration(s) shall reduce barrier technical risks associated with the system to enable U.S. Industry to be first to market.

System Requirements that Primarily Support DR 1 SRD-01 - EPFD Transport Mission Types SRD-02 - Flight Test Environment SRD-03 - Removed

SRD-01 - EPFD Transport Mission Types

The EPFD integrated MW-class powertrain system flight demonstration(s) shall demonstrate integrated MW-class powertrain technologies applicable to commercial aircraft transports for the single-aisle, regional, or thin haul markets.

Rationale:

The EPFD Project is maturing integrated MW-class powertrains for use in EAP Vision Vehicles operating in the single-aisle, regional, or thin haul markets.

Verification Method:

NASA Method: Analysis, Recommended Method to Industry Partner: Demonstration

Traceability:

OBJ: 1, 3, 5

DR: 1, 2, 3, 7, 8

Allocation Project, SOO-Sections I, II, III

Effective Date: February 21, 2021 Page 9

SRD-02 - Flight Test Environment

The EPFD integrated MW-class powertrain system flight demonstration(s) shall occur at altitudes and electrical power levels representative of commercial transports.

Rationale:

Demonstrating the integrated MW-class powertrain system at altitudes and power levels of the vision vehicles will have representative impacts on the performance of the integrated system and subsytems. The operational environments for turboprop and turbofan transport aircraft are different. Turboprops typically cruise below 25kft at less than 0.5 Mach. Turbofan aircraft can cruise at altitudes greater 40kft at 0.7- 0.8 Mach. The operational EPFD flight test altitudes and electrical power levels should be representative of the associated EAP Vision Vehicle that the technology is being tested for. Refer to EPFD-02-06 Technical Measures of Effectivness.

Verification Method:

NASA Method: Analysis, Recommended Method to Industry Partner: Demonstration

Traceability:

OBJ: 1,2, 3, 5

DR: 1, 2, 3, 7, 8

ConOps: 4.1 6.2

Allocation SOO-Sections II, III

SRD-03 - Removed

Effective Date: February 21, 2021 Page 10

4.2 Requirements that Primarily Support Driving Requirement 2

The following requirements are primarily traceable to DR 2: The EPFD integrated MW-class powertrain system flight demonstration(s) shall demonstrate in flight high voltage operation at all relevant ground and flight conditions.

System Requirements that Primarily Support DR 2 SRD-04 - Flight Test Demonstration of high voltage Integrated MW-class powertrain systems SRD-05 - Flight Test Demonstration of high power Integrated MW-class powertrain systems SRD-06 – Electromagnetic Interference (EMI) and Electromagnetic Compatibility (EMC) SRD-07 – Demonstrate an Energy Storage System SRD-08 - EPFD Propulsion during Flight Phases

SRD-04 - Flight Test Demonstration of high voltage Integrated MW-class powertrain systems

The EPFD integrated MW-class powertrain system flight demonstration shall conduct flight tests of a MW-class, integrated, high voltage electrical propulsion system.

Rationale:

EPFD will demonstrate technologies and vehicle-level integration of high-voltage (MW-class) electrified aircraft propulsion systems with advanced airframe systems to small transport aircraft. Refer to EPFD-02-06 Technical Measures of Effectivness Table 7 for voltage levels.

Verification Method:

NASA Method: Analysis

Recommended Method to Industry Partner: Demonstration

Traceability:

OBJ: 1, 2, 3, 5

DR: 1, 2, 3, 5, 6, 7, 8, 9

Allocation SOO-Section II, III

Effective Date: February 21, 2021 Page 11

SRD-05 - Flight Test Demonstration of high power Integrated MW-class powertrain systems

The EPFD integrated MW-class powertrain system flight demonstration shall conduct flight tests with MW power levels required for MW-class powertrains.

Rationale:

The primary focus of EPFD is MW-class systems. Refer to EPFD- 02-06 Technical Measures of Effectivness Table 7.

Verification Method:

NASA Method: Analysis

Recommended Method to Industry Partner: Demonstration

Traceability:

OBJ: 1, 3

DR: 1, 2, 7

Allocation SOO- Section II, III

Effective Date: February 21, 2021 Page 12

SRD-06 – Electromagnetic Interference (EMI) and Electromagnetic Compatibility

(EMC)

The EPFD integrated MW-class powertrain system flight demonstrator(s) shall demonstrate correct operation of production aircraft systems and MW-class powertrain systems in a common electromagnetic environment.

Rationale:

A MW-class electric propulsion system is four times higher power than typical state of the art aircraft electrical systems and often exhibit high frequency switching that can potentially lead to radiated and conducted electromagnetic interference (EMI) onto other aircraft systems (e.g., production aircraft systems). The integrated MW-class powertrain system will necessitate robust subsystem level EMI/EMC protections be developed for this unique application with the goal to prevent failure modes during operation while preventing unintended collateral impact to existing robust high Technical Readiness Level (TRL) aircraft systems. Subsystem EMI/EMC testing will identify conditions early, prior to integration, preventing damage to neighboring systems. This will ensure integrated MW-class powertrain aircraft remain safe for continued safe flight and landing through the planned range of flight conditions. The Industry Partner may propose using existing standards such as DO-160: Environmental Conditions and Test Procedures for Airborne Equipment, MIL- STD-461G: Requirements For The Control Of Electromagnetic Interference Characteristics Of Subsystems And Equipment, or equivalent.

Verification Method:

NASA Method: Analysis

Recommended Method to Industry Partner: Test

Traceability:

OBJ: 2, 3, 5

DR: 1, 2, 8

Allocation DRD-SE-05

Effective Date: February 21, 2021 Page 13

SRD-07 – Demonstrate an Energy Storage System

The EPFD integrated MW-class powertrain system flight demonstration(s) shall demonstrate an electrical energy storage system as part of the integrated MW-class powertrain capable of operating in the flight environment compatible with the Electrified Aircraft Propulsion Vision Vehicle.

Rationale:

The integrated MW-class powertrain flight demonstration(s) will demonstrate an electrical energy storage system with capablity levels that trace to the needs to the related Vision Vehicle.

Electrical energy storage systems for this application typically will operate at significantly higher voltages and much higher energy levels than current aircraft systems.

Verification Method:

NASA Method: Analysis

Recommended Method to Industry Partner: Demonstration

Traceability:

OBJ: 2, 3

DR: 1, 2, 3, 7

ConOps: 3.2

Allocation Directly to Industry Partner

SRD-08 - EPFD Propulsion during Flight Phases

The EPFD integrated MW-class powertrain system shall have the capability to demonstrate electrified aircraft propulsion during any phase of ground and flight that the system would be used for the associated EAP Vision Vehicle.

Rationale:

The flight test aircraft should utilize an integrated MW-class powertrain system during the mission phases where electrified aircraft propulsion is planned for use in the related Vision Vehicle. Flight phases include taxi, takeoff, climb, cruise, descent, approach and landing.

Verification Method:

NASA Method: Analysis

Recommended Method to Industry Partner: Demonstration

Traceability:

OBJ: 1, 2, 3, 5

DR: 1, 2, 3, 5, 7, 8

Effective Date: February 21, 2021 Page 14

4.3 Requirements that Primarily Support Driving Requirement 3

The following requirements are primarily traceable to DR 3: The EPFD integrated MW-class powertrain system flight demonstration(s) shall conduct crewed (human rated) flight operations and testing.

System Requirements that Primarily Support DR 3 SRD-09 - EPFD Crewed Flight Testing SRD-10 - Removed SRD-11 – Industry Partner Proposed Airworthiness Process.

SRD-12 - Environmental Testing SRD-13 - Structural Airworthiness Requirements SRD-14 – Software Requirements

SRD-09 - EPFD Crewed Flight Testing

The EPFD integrated MW-class powertrain system flight demonstration(s) shall conduct human crewed flight testing.

Rationale:

The integrated MW-class powertrain technologies will be flown on crewed, passenger carrying aircraft.

Verification Method:

NASA Method: Inspection

Recommended Method to Industry Partner: Demonstration

Traceability:

OBJ: 1, 2, 3, 5

DR: 1, 2, 3, 5, 6, 7, 8

ConOps: 3.1.1

Allocation Directly to Industry Partner, DRD-SE-01

Effective Date: February 21, 2021 Page 15

SRD-10 - Removed

SRD-11 – Industry Partner Proposed Airworthiness Process.

The EPFD integrated MW-class powertrain system flight demonstrator Industry Partners shall present their airworthiness process, including flight release, to NASA for acceptance.

Rationale:

As outlined in NPR 7900.3d, the airworthiness and flight release processes are tailorable and shall be proposed by the Industry Partner. The process should be coordinated with EPFD Engineering and Airworthiness technical authority. The AFOP- 7900.3-023: Airworthiness and flight safety review process, which is compliant with NPR 7900.3d and will be a guiding document to develop the framework for the Industry-led, tailored airworthiness review and flight release process.

Verification Method:

NASA Method: Analyisis

Recommended Method to Industry Partner: Analysis

Traceability:

OBJ: 2, 3

DR: 3, 5, 6

Allocation DRD-SE-06

Effective Date: February 21, 2021 Page 16

SRD-12 - Environmental Testing

The novel MW-class powertrain components that will be flown on the EPFD integrated MW-class powertrain system flight test aircraft shall demonstrate successful environmental tests of subsystems in support of airworthiness, with tailored environmental testing standards and guidelines that are appropriate for commercial transport flight environments.

Rationale:

Integrated MW-class powertrain systems must be safely demonstrated in flight. One of the desired outcomes for the EPFD Project is to develop environmental testing standards that account for high voltage and high power MW-class electrified aircraft propulsion technologies. Given a number of unprecedented altitude dependent high voltage and power electrical boundary conditions in this TRL raising activity, additional specifications will be needed when tailoring existing environmental qualification and acceptance metrics. EPFD partners should propose the environmental testing standards and guidelines that will be tailored to ensure airworthiness of integrated MW-class components that will be used on the demonstrator aircraft. Existing standards such as DO-160:

Environmental Conditions and Test Procedures for Airborne Equipment, AFOP-7900.3-004: Environmental Acceptance Testing:

Electronic & Electromechanical Equipment, or equivalent standards may be used.

Verification Method:

NASA Method: Inspection

Recommended Method to Industry Partner: Test

Traceability:

OBJ: 1, 2, 3, 5

DR: 1, 2, 3, 5, 6, 8

Allocation DRD-SE-05, SE-06

Effective Date: February 21, 2021 Page 17

SRD-13 - Structural Airworthiness Requirements

EPFD Industry Partners shall develop an airworthiness approach for integration of MW-class powertrain technologies into the flight test aircraft structures.

Rationale:

Integrated MW-class powertrain systems must be safely tested inr flight. Structural modifications may be required for integration of the integrated MW-class powertrain technology into the flight test aircraft and may impact the static loads and dynamic characteristics of the aircraft structure. The Industry Partner should propose a structural airworthiness process.

NASA AFRC document, AFG-7123.1-001: Aircraft structural safety of flight guidelines may be to be referred to for guidance.

Verification Method:

NASA Method: Analysis

Recommended Method to Industry Partner: Analysis

Traceability: DR: 3

Allocation DRD-SE-06

SRD-14 – Software Requirements

The software development approach used by the Industry Partners shall be tailored to align with RTCA DO-178C: Design Assurance Guidance for Airborne Electronic Hardware or alternatively NASA NPR 7150.2: NASA Software Engineering Requirements.

Rationale:

For software developed as part of EPFD, Industry Partner(s) under contract are required to align with NASA software engineering requirements. The EFPD Software Management Plan is based on NPR 7150.2C and allows provisions for Industry Partner(s) to use DO-178C: Software Considerations in Airborne System and Equipment Certification.

For safety critical software NASA-STD-8739.8, NASA Software Assurance and Software Safety Standard (or equivalent), shall be satisfied per NPR 7150.2C.

Verification Method:

NASA Method: Inspection

Recommended Method to Industry Partner: Inspection

Traceability: DR: 3

Allocation DRD-SW-01

Effective Date: February 21, 2021 Page 18

4.4 Requirements that Primarily Support Driving Requirement 4

The following requirements are primarily traceable to DR 4: The EPFD integrated MW-class powertrain system flight demonstration(s) will attempt to conduct first flight by 2023 and shall conduct first flight no later than August 2024.

System Requirements that Primarily Support DR 4 SRD-15 - First Flight No Later Than Date

SRD-15 - First Flight No Later Than Date

The Industry Partner(s) will attempt to conduct first flight of the integrated MW-class powertrain system by 2023 and shall conduct first flight no later than August 2024.

Rationale:

To meet Stakeholders Expectations and the timeline for technology development that enables insertion into Industry Commercial Vision Vehicles, EPFD first flight is required to occur no later than August 2024. Spiral developments may extend into 2025.

Verification Method:

NASA Method: Inspection

Recommended Method to Industry Partner: Inspection

Traceability:

OBJ: 1, 4

DR: 1, 4

Allocation Project, Directly to Industry Partner

Effective Date: February 21, 2021 Page 19

4.5 Requirements that Primarily Support Driving Requirement 5

The following requirements are primarily traceable to DR 5: The EPFD integrated MW-class powertrain system flight demonstration(s) shall demonstrate in flight a thermal management system for the electrical power system.

System Requirements that Primarily Support DR 5 SRD-16 - Thermal Management System SRD-17 - Hot and Cold Day Operations

SRD-16 - Thermal Management System

The EPFD integrated MW-class powertrain system flight demonstrator(s) shall demonstrate in-flight a thermal management system for the integrated MW-class powertrain.

Rationale:

Thermal management for MW-class powertrain systems is a challenge because large amounts of waste heat are produced at relatively low rejection temperatures. The thermal management system must support the overall integrated MW-class powertrain system that is proposed through all phases of operation. There are not specific thermal management system sucess criteria, but the thermal management system associated with the integrated MW-class powertrain is part of the overall metrics.

Verification Method:

NASA Method: Analysis

Recommended Method to Industry Partner: Demonstration

Traceability:

OBJ: 3

DR: 5

Effective Date: February 21, 2021 Page 20

SRD-17 - Hot and Cold Day Operations

The EPFD integrated MW-class powertrain system shall be capable of demonstrating integrated MW-class powertrain technology at SAE AS210 10% hot day conditons and 10% cold day conditions during ground and takeoff operations.

Rationale:

The thermal management system must function properly under all expected operating conditions, including Hot and Cold Day Operations. This requirement does not imply that the aircraft must perform flight demonstrations under hot or cold day conditions.

The Industry Partner shall design the integrated MW-class powertrain system to the temperatures in SAE international AS210 “Definition of Commonly Used Day Types (Atmospheric Ambient Temperature Characteristics Versus Pressure Altitude),” Table A10 which provides 10% Hot Day temperature versus pressure altitude based on Table XIX, “Supplementary HighTemperature Values for the Worldwide Air Environment”, of MIL-HDBK-310, dated 9 January, 1987. Table A13 provides 10% Cold Day temperature versus pressure altitude based on Table XX, “Supplementary Low Temperature Values for the Worldwide Air Environment”, of MIL- HDBK-310, dated 9 January, 1987 Example: Table A10 lists a temperature of 113 F (45C) at a pressure altitude of 0ft (0m). Table A13 lists a temperature of –65 F (-54C) at a pressure altitude of 0ft (0m)

Verification Method:

NASA Method: Analysis

Recommended Method to Industry Partner: Analsyis

Traceability:

OBJ: 2, 3

DR: 2, 5, 8

Effective Date: February 21, 2021 Page 21

4.6 Requirements that Primarily Support Driving Requirement 6

The following requirements are primarily traceable to DR 6: The EPFD integrated MW-class powertrain system flight demonstration(s) shall demonstrate in flight a control system which manages electrical faults while maintaining fail-safe aircraft operations.

System Requirements that Primarily Support DR 6 SRD-18 - Fault Control System

SRD-18 - Fault Control System

The EPFD integrated MW-class powertrain system shall be capable of safely managing electrified powertrain system faults. Safety can be demonstrated through a combination of analysis, ground test, and/or flight test.

Rationale:

The integrated MW-class powertrain requires robust protection functions for electrically related faults (e.g., ground faults, line-to-line low and high impedance faults) that can potentially impact the propulsion system and other aircraft systems. Fault detection, isolation, and reporting need to be demonstrated. A fail-safe design will detect and mitigate failures using both software and hardware approaches. In addition, fail safe operation should be demonstrated with faults being isolated. Cascading failures and collateral impact to aircraft systems should be avoided.

Verification Method:

NASA Method: Analysis

Recommended Method to Industry Partner: Demonstration

Traceability:

OBJ: 1, 3, 5

DR: 1, 3, 6

Effective Date: February 21, 2021 Page 22

4.7 Requirements that Primarily Support Driving Requirement 7

The following requirements are primarily traceable to DR 7: The EPFD integrated MW-class powertrain system flight demonstration(s) shall measure the performance of the system against the technical performance measures (TPMs) – Reference EPFD 02-06 for TPMs.

System Requirements that Primarily Support DR 7 SRD-19 - Obtain Integrated MW-class Powertrain Test Data In-Flight SRD-20 - Removed SRD-21 - Removed

SRD-19 - Obtain Integrated MW-class Powertrain Test Data In-Flight

The EPFD integrated MW-class powertrain system flight demonstration(s) shall obtain in-flight test data of the integrated MW-class powertrain systems and components.

Rationale:

Integrated MW-class powertrain system flight data is needed to validate electrified powertrain systems and components in a relavant environment. These data will directly support for example: 1) Measurement of technical performance of Integrated MW-Class Powertrain Systems 2) Provide validation data to reduce/retire regulations and standards gaps through simulation, ground test, and flight tests of integrated MW-class powertrain systems 3) Provide validation data for NASA and Industry tools and research (jointly defined with AATT, TTT, HyTEC and EPFD Projects) 4) EPFD risk mitigations, and 5) Technology readiness level progression. The flight data plan will drive the instrumentation sensor allocation, redundancy and placement locations derived from system test requirements during project development. This data should be recorded in flight for post-processing and analysis on ground. The Industry Partners will develop a Master Measurement List (MML) that will be provided to the NASA EPFD Project.

Verification Method:

NASA Method: Analysis

Recommended Method to Industry Partner: Demonstration

Traceability:

OBJ: 3

DR: 2, 5, 7, 9

Allocation

DRD-TE-03, SE-05

SRD-20 - Removed

SRD-21 - Removed

Effective Date: February 21, 2021 Page 23

4.8 Requirements that Primarily Support Driving Requirement 8

The following requirements are primarily traceable to DR 8: The EPFD integrated MW-class powertrain system flight demonstration(s) shall provide ground and flight test data to address gaps in regulations and standards associated with system application to commercial transport aircraft.

System Requirements that Primarily Support DR 8 SRD-22 – Identify Gaps & Develop Approaches to Closing the Gaps Prioritized in Regulations and Standards Gap Analysis SRD-23 - Removed

SRD-22 – Identify Gaps & Develop Approaches to Closing the Gaps Prioritized in Regulations and Standards Gap Analysis

The design for the MW-Class powertrain system as integrated onto the Industry Partner’s flight test aircraft shall be used to identify and address the highest priority gaps and means of compliance in standards and in current regulations of Title 14 of the Code of Federal Regulations (CFR) Chapter I, Subchapter C, Aircraft, that enables timely market introduction of integrated MW-class powertrain system technology in commercial aircraft.

Rationale:

Electrification of aircraft and its technology are evolving more rapidly than the regulations and standards necessary to support them. An assessment of the regulations is required to identify gaps in the current regulations, and identify the highest priority standards that need to be developed. The EPFD Project team, consisting of NASA and Industry Partners, will work with US aviation industry on the development of standards and regulations. The regulations for the aircraft and technology of interest to the EPFD Project is focused on Title 14 of the Code of Federal Regulations (CFR) Part 33, Aircraft Engines. In addition, large aircraft will also examine 14 CFR Part 25, Large Transport Category Aircraft. Finally, small aircraft will examine both 14 CFR Part 23, Normal Category Aircraft, and Part 35, Propellers, in addition to 14 CFR Part 33. The identified highest priority competitive and pre-competitive (Unlimited Rights) MW-class electrified aircraft propulsion regulations and standards gaps will be documented, and recommended means-of-compliance will inform the development of new standards, and potentially updating regulations.

Verification Method:

NASA Method: Analysis

Recommended Method to Industry Partner: Demonstration, Analysis

Traceability:

OBJ: 5

DR: 7, 8, 9

Allocation Project, SOO Section II, DRD-SE-02

SRD-23 - Removed

Effective Date: February 21, 2021 Page 24

4.9 Requirements that Primarily Support Driving Requirement 9

The following requirements are primarily traceable to DR 9: The EPFD integrated MW-class powertrain system flight demonstration(s) shall acquire ground and flight data used to validate NASA modeling tools and research.

System Requirements that Primarily Support DR 9 SRD-24 - Obtain Integrated MW-Class Powertrain Ground Test Data SRD-25 - EPFD Ground Testing for Technology Readiness Level Maturation and Risk Reduction SRD-26 - System Performance Analysis and Model Data

SRD-24 - Obtain Integrated MW-Class Powertrain Ground Test Data

The EPFD ground tests shall obtain data from the integrated MW-class powertrain components, subsystems and systems during ground demonstration(s) that will directly support risk mitigations, regulations and standards development, technology readiness level progression and integration for the flight demonstration.

Rationale:

Ground test data from the integrated MW-class powertrain components, subsystems and systems are need to characterize the integrated MW-class powertrain components, subsystems and systems prior to the flight test. These data will directly support EPFD risk mitigations, regulations and standards development, technology readiness level progression and integration onto the EPFD aircraft.

Verification Method:

NASA Method: Inspection

Recommended Method to Industry Partner: Inspection

Traceability:

OBJ: 2, 5

DR: 1, 2, 8, 9

Allocation SOO-Section I, II, III, DRD-SE-05, TE-03

Effective Date: February 21, 2021 Page 25

SRD-25 - EPFD Ground Testing for Technology Readiness Level Maturation and Risk Reduction

Ground demonstration(s) of the EPFD integrated MW-class powertrain components, subsystems and systems shall be conducted to raise TRL level, reduce risk and validate performance ahead of the flight demonstration.

Rationale:

Integrated MW-class powertrain components, subsystems and systems testing of hardware and software at the power levels expected during flight is essential to ensuring a successful demonstration is essential to advance the technology readiness level and reduce risk to ensure a successful flight demonstration. Ground tests may be performed in a laboratory, an environmental facility, and/or on a copper bird to evaluate MW-class powertrain components, subsystems and systems at conditions that are representative of flight conditions when possible.

Verification Method:

NASA Method: Analysis

Recommended Method to Industry Partner: Test, Demonstration

Traceability:

OBJ: 2, 5

DR: 1, 2, 8, 9

Allocation SOO-Section I, II, DRD-SE-05, TE-02, TE-03, TE-04

Effective Date: February 21, 2021 Page 26

SRD-26 - System Performance Analysis and Model Data

Data for the integrated MW-class powertrain system, within the accuracy of the measured ground and fight test data, shall be collected for validation of the physics-based models to be used in the assessment of the performance of the EAP vision vehicle.

Rationale:

Physics-based model and system performance analysis data will be collected for the integrated MW-class powertrain and Vision Vehicle as described in the Technical Data Requirements and Reporting DRD-TE-

03. For the Vision Vehicle, the collected data will be used to assess the sensitivity of the Vision Vehicle benefits to the key performance parameters of the Integrated MW-class powertrain, the associated barrier technical and integration risks, the required technology maturation, and regulations and standards changes needed for introduction of the Vision Vehicle as described in the Vision Vehicle Description and Validation Report DRD-TE-01. For the integrated MW-class powertrain the collected data will support the verification and validation process of the proposed ground and flight demonstration systems engineering products as described in the Verification and Validation Plan DRD-SE-05.

Verification Method:

NASA Method: Analysis

Recommended Method to Industry Partner: Analysis

Traceability:

OBJ: 3

DR: 1, 2, 9

Allocation Project, DRD-SE-05, TE-01, TE-03

Effective Date: February 21, 2021 Page 29

Table 7 - EPFD Verification Methods

Verification Methods* *V&V Plan’s method definitions have precedence

Inspection

This method of verification is the examination of documentation or physical characteristics that determines compliance of the item with requirements without the use of special laboratory equipment, procedures, test support items, or services. Inspection uses standard methods such as visuals, gauges, etc., to verify compliance with requirements.

Analysis

This method of verification utilizes techniques and tools such as computer and hardware simulations, analog modeling, similarity assessments, and validation of records to confirm that design requirements to be verified have been satisfied. Analysis is the evaluation of the results of multiple tests and analyses at a lower level as it would apply to a higher level of assembly.

Demonstration

This method of verification is a qualitative exhibition of functional performance (i.e., serviceability, accessibility, transportability and human engineering features) usually accomplished with no or minimal instrumentation.

Test

This method of verification is a method where requirements are verified by quantitative measurement during or after the controlled application of functional and environmental stimuli. These measurements may require the use of laboratory equipment, recorded data, procedures, test support items, or services. For all verification, qualification, and acceptance test activities, pass or fail test criteria or acceptance tolerance bands (based upon design and performance requirements) shall be specified prior to conducting the test. This will ensure that the actual performance of tested equipment or systems can readily be assessed against established specifications.

Effective Date: February 21, 2021 Page 32

APPENDIX E ACRONYMS

An alphabetical list of all acronyms used in this document.

Table 10 - List of Acronyms

Acronym Definition AATT Advanced Air Transport Technology AAVP Advanced Air Vehicles Program AFG Armstrong Flight Guideline AFOP Armstrong Flight Operational Procedure AFRC Armstrong Flight Research Center ARMD Aeronautical Research Mission Directorate CC Critical Commitments CFR Code of Federal Regulations ConOps Concept of Operations DR Driving Requirements DRD Data Requirements Deliverable EAFB Edwards Air Force Base EAP Electrified Aircraft Propulsion EMC Electromagnetic Compatibility EMI Electromagnetic Interference EPFD Electric Powertrain Flight Demonstration FDC Flight Demonstration and Capabilities HDBK Handbook IP Industry Partner KPP Key Performance Parameters KW Kilo Watt MIL Military MML Master Measurement List MOE Measure of Effectiveness MOP Measure of Performance MW Mega Watt NASA National Aeronautics and Space Administration NGO Needs, Goals and Objectives NPR NASA Procedural Requirement OBJ Objective PLR Program Level Requirements PMP Project Management Plan PP&C Program Planning and Control RFP Request for Proposal RTCA Radio Technical Commission for Aeronautics SAE Society of Automotive Engineers SE System Engineering SEMP System Engineering Management Plan SI International System of Units

Effective Date: February 21, 2021 Page 33

Acronym Definition SIP Strategic Implantation Plan SOO Statement of Objectives SOW Statement of Work SRD System Requirements Document ST Strategic Thrust S&MA Safety and Missions Assurance SW Software TBD To be Determined TBR To be Resolved TDP Technology Development Plan TM Technical Memorandum TPM Technical Performance Measure TTT Transformational Tools and Technologies TRL Technology Readiness Level U.S. United States USCU United States Customary Units V&V Verification and Validation

Effective Date: February 21, 2021 Page 34

APPENDIX F TO BE DETERMINED AND TO BE RESOLVED ITEMS

This Appendix contains a list of “To Be Determined” (TBD) items and “To Be Resolved” (TBR) issues. TBDs are defined as XX and are generally closed via project decisions. TBRs may or may not have a value listed that is under evaluation. The actual value is generally discussed by the SE and/or management team and may include an engineering trade study to formally close before the final value is resolved. Future updates to this document will remove the TBD or TBR once they are closed.

Table 11 - To Be Determined Items

TBD Section Description Status TBD-01 SRD-07 The project needs a way to communicate the requirement for one hour of continuous electrical battery power. The SOO is best mechanism to do that.

Resolution: SRD-07 has been allocated directly to the Industry Partner via EPFD-02-02.

Resolved

TBD-02 SRD-08 The project needs a way to communicate the requirement for EAP to be used during all mission phases include taxi, takeoff, climb, cruise, descent, approach and landing. The SOO is best mechanism to do that.

Resolution: SRD-08 has been allocated directly to the Industry Partner via EPFD-02-02.

Resolved

TBD-03 SRD-16 The project needs a way to communicate the requirement for EAP to utilize a thermal management system. The SOO is best mechanism to do that.

Resolution: SRD-16 has been allocated directly to the Industry Partner via EPFD-02-02.

Resolved

TBD-04 SRD-17 The project needs a way to communicate the requirement for EAP to designed to operate during hot day conditions. The SOO is best mechanism to do that.

Resolution: SRD-17 has been allocated directly to the Industry Partner via EPFD-02-02.

Resolved

TBD-05 SRD-18 The project needs a way to communicate the requirement for a fault control system. The SOO is best mechanism to do that.

Resolved: SRD-18 has been allocated directly to the Industry Partner via EPFD-02-02.

Resolved

TBD-06 2.0 The Conops documents is not baselined at this time. Resolution: document reference removed.

Resolved