Assessments

1. Introduction to Minimum Requirements for Electric Propulsion

2. Terminology in ASTM F3338

3. Requirements and Ratings in ASTM F3338

4. Endurance and Durability Testing in ASTM F3338-24

Introduction to Minimum Requirements for Electric Propulsion

  1. Q1: Why does ASTM F3338-24 not cover all possible engine configurations?
    • Because it is meant to be used alongside other supporting documents
    • Because most configurations are not airworthy
    • Because the FAA doesn’t permit electric hybrid designs
  2. Q2: What is the role of the FAA in electric engine design approval in the U.S.?
    • It handles only post-certification inspections
    • It serves as the civil aviation authority and issues design guidance
    • It certifies only imported electric aircraft
  3. Q3: What advantage does electric propulsion offer, as described in the video?
    • Reduced noise and no exhaust emissions
    • Faster takeoff speeds
    • Increased turbulence resistance
  4. Q4: Which of the following is not one of the potential uses for electric aircraft mentioned in the video?
    • Air ambulance
    • Cargo delivery
    • Military combat operations
  5. Q5: What is significant about Pipistrel’s Vellis Electro?
    • It is a hybrid engine aircraft certified for IFR
    • It was the first FAA-certified electric drone
    • It is the first type-certificated electric aircraft for pilot training
  6. Q6: What did the FAA grant in March 2024 regarding electric aircraft?
    • An LSA airworthiness exemption for flight training
    • A full type certificate for air taxis
    • An overhaul inspection waiver for electric motors
  7. Q7: Why are FAA “special conditions” being created for some electric engines?
    • To replace existing standards entirely
    • Because no standard certification yet exists for all electric engines
    • To relax safety requirements temporarily
  8. Q8: How did the FAA establish the “special conditions” for certifying electric engines?
    • Based on international UN aviation goals
    • By combining Part 33 standards with F338-18 technical criteria
    • By exempting electric aircraft from existing rules
  9. Q9: What milestone did Joby Aviation achieve in 2022?
    • They received their FAA Part 135 air carrier certificate
    • They flew across the Atlantic using electric propulsion
    • They were acquired by the Air Force
  10. Q10: As of 2025, what is one ongoing challenge for electric engine certification in the U.S.?
    • Limited funding from private companies
    • Incompatibility with U.S. airspace systems
    • Absence of comprehensive certification requirements for all electric engines

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Terminology in ASTM F3338

  1. Q1: Why is a common understanding of terminology important in aviation, according to the video?
    • It fosters teamwork and avoids confusion
    • It simplifies engine manufacturing
    • It allows for faster aircraft certification
  2. Q2: How does the video define the role of an electric engine in aircraft?
    • It controls electronic signals from the cockpit
    • It converts electric power into mechanical thrust for propulsion
    • It manages the flight computer interface
  3. Q3: What is the main difference between an electric engine and a motor, as explained in the video?
    • A motor requires fuel; an engine doesn’t
    • A motor produces rotational power; an engine provides aircraft propulsion
    • An engine is smaller than a motor
  4. Q4: What does “rated maximum continuous power” refer to in ASTM F3338?
    • Power used only during descent
    • Maximum power for 5 minutes
    • Brake power available for unrestricted use
  5. Q5: How long can “rated takeoff power” be used, as defined in the video?
    • No more than five minutes
    • Indefinitely during ascent
    • Up to 10 minutes in emergencies
  6. Q6: Which of the following is an example of non-periodic duty in aircraft systems?
    • Landing gear retraction
    • Constant-speed propeller adjusting pitch during flight
    • Ice sensor monitoring
  7. Q7: What characterizes periodic duty in aviation systems?
    • Random load variations throughout flight
    • Load spikes during power loss
    • One or more constant loads for specific durations
  8. Q8: What’s the function of deicing boots as discussed in the context of duty types?
    • Non-periodic load balancing
    • Example of periodic duty due to fixed operating cycle
    • Heat dissipation management
  9. Q9: Which term best describes how the load behaves across operating ranges in periodic duty?
    • Constant for defined durations
    • Unpredictable and fluctuating
    • Constant with varied time
  10. Q10: How does ASTM F3338 reference external standards?
    • Only when no internal definitions exist
    • It avoids external references altogether
    • It calls out other standards like SAE J245 when needed

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Requirements and Ratings in ASTM F3338

  1. Q1: What kind of information must be included for safe engine operation?
    • Things like maximum torque, temperature, and vibration limits
    • Marketing data and manufacturer logos
    • A list of all suppliers used during design
  2. Q2: What factors influence how long and how hard an electric engine can run safely?
    • Paint finish and wing length
    • Duty cycle involving power, speed, torque, and time
    • Whether the aircraft is single- or twin-propeller
  3. Q3: How does the video say power ratings can be visually represented?
    • Through barcodes scanned into software
    • Using time-sequenced graphs or pre-defined duty profiles
    • Through temperature gauges on control panels
  4. Q4: What real-world example does the video use when discussing “overspeed”?
    • The rotor must not break apart even if spinning faster than normal
    • When the engine stalls mid-air
    • Pilots manually throttle up during storms
  5. Q5: What kind of electric engine parts need to be taken out after a certain number of hours or flights?
    • Any parts exposed to wind
    • All cockpit controls
    • Lifelimited parts like bearings with low-cycle fatigue
  6. Q6: Which part is mentioned as critical, but not necessarily lifelimited, in electric engines?
    • The propeller
    • The landing gear
    • The wing flaps
  7. Q7: What does the safety analysis process aim to do in electric engine design?
    • Ensure proper color coding on wiring
    • Identify what could go wrong and reduce hazard risks
    • Determine battery recharge speed
  8. Q8: What kind of events can block cooling systems in electric aircraft?
    • Dust storms and overheating
    • Cabin pressurization errors
    • Bird strikes, hail, or ice
  9. Q9: What must happen if there’s structural damage to a cooling system?
    • A restart sequence must be triggered
    • A flight delay must be reported
    • It should not lead to any hazardous engine behavior
  10. Q10: What is the takeaway message about engine safety and design?
    • That these engines are safer because they’re smaller
    • That safety must be ensured in real conditions like failure and ingestion
    • That engines are mostly hands-off for pilots now

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Endurance and Durability Testing in ASTM F3338-24

  1. Q1: What is the primary goal of endurance and durability testing for electric engines?
    • To ensure no unsafe condition develops during the engine's life or between overhauls
    • To increase battery cycle efficiency
    • To validate exterior aerodynamic features
  2. Q2: What does vibration testing aim to confirm?
    • That the propeller blade angles stay fixed
    • That any vibration encountered is within acceptable limits
    • That the aircraft structure does not flex
  3. Q3: What must be proven during the over torque test?
    • That the engine can keep running without maintenance at over torque levels
    • That torque sensors are replaced post-test
    • That the engine fuel system is optimized
  4. Q4: What is a key requirement of the over temperature test?
    • Continuous operation for at least 6 hours
    • Rotor magnets must exceed their thermal rating
    • Operation until steady-state plus one hour, with magnets within limits
  5. Q5: What is the main purpose of calibration tests?
    • To align the engine’s GPS unit
    • To establish power characteristics across operational ranges
    • To ensure the weight-to-thrust ratio meets baseline specs
  6. Q6: What types of functions are included in operation testing?
    • Landing gear extension, retraction, and braking
    • Throttle smoothing and taxiing
    • Powering on, idling, accelerating, and overspeeding
  7. Q7: What does the power response test assess?
    • Flight time per battery cycle
    • The engine's ability to increase from minimum to peak power without damage
    • Noise levels at different altitudes
  8. Q8: When are rotor locking tests performed?
    • Only on hybrid-electric engines
    • If the engine has a rotor-locking feature that must be tested under torque
    • At cruising speed with autopilot engaged
  9. Q9: What happens during the teardown inspection?
    • The engine is fully disassembled and inspected post-testing
    • The batteries are swapped and discarded
    • The cooling system is flushed and re-oiled
  10. Q10: What is the focus of containment testing?
    • Evaluating wiring insulation under pressure
    • Verifying propeller pitch memory
    • Assessing energy and path of any fragments from rotating component failures

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This work was prepared by Purdue University under award number 70NANB22H200 from the National Institute of Standards and Technology, U.S. Department of Commerce.  The statements, findings, conclusions, and recommendations are those of the author(s) and do not necessarily reflect the views of the National Institute of Standards and Technology or the U.S. Department of Commerce.