DER Services

Part 27 and Part 29 Powerplant DER (chart B) and Flight Analyst (chart G)

Christopher Ludwig

Consultant Powerplant DER and Flight Analyst supporting projects relating to conventional rotorcraft under 14 CFR part 27 and 14 CFR part 29 and eVTOL aircraft under 14 CFR part 21.17(b). One of the few consultant DERs with part 27/29 delegations for both Powerplant Installations under Chart B and Propulsion Flight Test under Chart G.

I have worked on certification projects with four helicopter OEMs, and I am an Unit Member of three ODAs. I also consult with eVTOL companies as they work towards project initiation with the FAA.

Prior to working as a DER/Flight Analyst, I served as an Aircraft Test Director, Flight Test Engineer, Flight Test Software Developer, and Data Acquisition Engineer. My career started as a passenger flying onboard helicopters servicing offshore platforms in locations including the Gulf of Mexico, Caspian Sea, North Sea, Offshore Angola and Congo, and Western Australia. I learned that I like test engineering and data acquisition. I also took up aerobatics and formation flying. It made sense to combine all my passions with my undergraduate in aerospace and get into flight testing. I went back to school to get a flight test Master's degree. After 6 years in the oil industry and 2 years studying Flight Test, I joined a major rotorcraft OEM where I worked as a Powerplant FTE and Aircraft Test Director before becoming an ODA Unit Member. It finally came time where going out on my own as a consultant made the most sense, and that brings me to today.

Part 27 and 29 Flight Analyst

15 years as an Flight Test Engineer
Engine upgrade programs on military and civil helicopters
Engine rated power increase certification
Installed performance recovery investigations
FADEC to aircraft integration including Powerplant aspects of cockpit displays
Engine governing and limiter performance flight test
Engine driveshaft upgrade programs
Fuel system flight test including fuel flow, venting, Hover In Flight Refuel (HIFR), and fuel jettison
Extreme cold weather testing including climatic chamber and natural cold testing at the aircraft level to -51°C.
Critical Avionics Cooling flight test in support of 29.1309(a) certification
Mechanical and hydraulics system flight test
Environmental Control System (Heater and Air Conditioner) function and performance flight test
Helicopter tie-down endurance testing per 29.923 and 29.927

Part 23, 27 and 29 Powerplant DER

Engine installation manual compliance
Flight envelop expansion (Weight, Altitude, Temperature) certification
Engine rated power increase certification
Special mission power rating certification
Specialist knowledge in installed power available analysis including 29.45(c) showing of compliance
Specialist knowledge in engine vibration analysis to 29.907
Advanced methods for powerplant and drivetrain cooling analysis
Experienced in cockpit display design and validation for powerplant and drive system indicating systems
Engine driveshaft upgrade programs
Experienced with eVTOL Projects

eVTOL Aircraft Certification

The FAA announced in June of 2022 that powered-lift aircraft, which includes eVTOLs as well as most Urban Air Mobility aircraft, will be certified as a special class of aircraft under 14 CFR part 21.17(b). The certification basis for these aircraft will be compiled from the existing regulations in parts 23, 25, 27, 29, 31, 33, and 34 as well as special conditions for novel features which do not have adequate existing regulations. This approach would allow the cockpit and cabin of an eVTOL to comply with part 23, while driveshafts, fuel tanks, and engine installations in the case of hybrid designs, might comply with part 27, propulsion systems might comply with part 33, and unique rotors might comply with standards from part 34 or part 27/29.

This hybrid approach to certification allows for the FAA to select regulations which best suit the unique design attributes of a special class of aircraft, but the burden on the applicant is significant. Where before it was only necessary to maintain a team of DERs dedicated to a single aircraft type, the applicant may now need DERs with a background in a broad selection of parts 23, 25, 27, 29, 33, and 34. Even when the Certification Basis has been designated as a portion of part 23 Amendment 64, the Applicant and FAA may still negotiate the use of a part 27 or 29 paragraph as the Means of Compliance to fulfill the part 23 requirement. Certification guidance material defining a means of compliance specific to eVTOL is currently being developed in industry technical and regulatory committees around the world. UAM and eVTOL companies must keep pace with those developing standards and policies.

The 21.17(b) special class certification approach is not necessarily a burden in all cases for applicants. For instance, the rotor burst safety standard in part 29 is less stringent than the rotor burst standard in part 23. The reason for this difference is that the FAA recognizes that rotorcraft mount their engines in the fuselage and therefore usually cannot achieve adequate lateral separation to meet the part 23 and part 25 criteria for safety of the remaining engine. This is not the only area where part 27 or part 29 regulations are less stringent than part 23 due to the unique aspects of rotorcraft.

While the exact certification basis and means of compliance for a prototype design can only be determined after the initiation of the certification project, preliminary design must be performed to a prospective set of requirements to ensure the end product is certifiable. Many applicants have found that it is best to work with a group of advising DERs to consider the requirements of each part and to determine where certification requirements are similar or different so that the applicant can be informed to ensure their design will meet likely certification requirements. TS Integrators is able to supply certification advising relating to part 27 and part 29 powerplant systems to assist powered-lift applicants navigate the challenging path to successful certification.

Unique Certification Project Experience

Installed Engine Performance

Experienced validating installed performance to the highest possible accuracy
Experienced showing compliance to 29.45(c) with and without access to engine cycle models
Experienced showing compliance to 29.45(f) with FADEC computed power assurance checks

FADEC, HUMS and Display Integration

Experienced certifying engine limits integration with glass cockpit displays, and Health, and Usage Monitoring Systems
Experienced with powerplant aspects of 29.1305, 29.1321, 29.1521, 29.1549, and 29.1583
Experienced with special condition issue papers relating to the use of integrated power indicators in lieu of separate engine gas temperature and engine torque indicators
Experienced certifying emergency engine and drivetrain limits augmentation in FADEC logic

Environmental Testing and Certification

Environmental chamber testing of the whole aircraft from 50°C to -50°C including powerplant and mechanical systems, ECS, drivetrain systems, avionics and mission systems, onboard computers, maintenance tasks, and aircraft servicing
Natural hot and cold weather testing on ground and in flight

Military Commercial Derivative Aircraft

Experienced on multiple aircraft types certifying military modifications to engine installations and fuel systems on civil helicopters for military applications
Work experience includes certifying custom power ratings for military missions via special condition issue papers
TS Integrators is able to provide DER witnessing and compliance findings for special access programs

Helicopter to Ship Integration

Shipboard pressure refueling testing including refuel envelope definition based on deck motion
Testing of rollover vent valves and over-pressure relief valves in helicopter fuel systems under extreme use cases
Hover In Flight Refuel (HIFR) testing
Shipboard fuel slosh and fuel vent leakage testing for safe hangar storage

(Certifying authority was DTAES Canada)

Engine Vibration and Structural Dynamics Analysis

Extensive experience writing software to automate frequency spectrum processing, display, limit checking, and reporting of flight and ground test dynamics data
- Developed the Telemetry monitoring software for a transport category rotorcraft manufacturer, used for engine vibration and flight load survey and envelope expansion structural monitoring
- Developed the drive system and gearbox test stand monitoring software for a transport category rotorcraft manufacturer
- Developed a Flight Test data processing and reporting software for an STC applicant
Types of processing employed to date include:
- Fast Fourier Transform (FFT) with various window types
- Low pass, band pass, high pass, and band stop via Butterworth digital filers
- Low pass, band pass, high pass, and band stop via Inverse FFT
- Zero phase shift digital filters
- Various types of limit checking including Nr tracking limits.

(Software Development activities are performed through Moore Good Ideas Inc.)

Industry Collaboration and Technical Contributions

SAE Powered Lift Propulsion Committee (S-12) - Vice Chair and Voting Member
SAE Aircraft Icing Technology Committee (AC-9C) - Liaison Member
ASTM International General Aviation Committee Member, F44.50 Powerplant, and F44.60 Systems and Equipment
Society of Flight Test Engineers Technical Council Member

Confidentiality

As a DER, my most valuable asset is the special trust and confidence that clients, their vendors and partners, and the FAA place in me. I work with several helicopter manufacturers and many aircraft modifiers. My relationship to these clients is similar to that of FAA employees who see test reports from other manufacturers, but never discuss this data with other parties. Design data from OEMs and TC holders will never be shared with STC applicants or any other client.

Engine manufacturer supplied data including installation manuals, cycle models, and installation losses, are also held in absolute confidence. In most cases, TS Integrators will enter into NDAs directly with engine manufacturers to provide a direct means for them to protect their proprietary information from unauthorized disclosure.

In order to ensure impartiality and to avoid conflicts of interest, TS Integrators supplied engineering services will be limited to the following:

Assisting clients with the compiling of a certification basis and developing a compliance checklist for a PSCP
Advising clients on accepted certification methods as needed to correctly identify project scope in the PSCP
Assisting clients to identify aspects of proposed designs which may not be certifiable, or may require an equivalent level of safety finding or special condition to achieve certification
Assisting clients with issue papers and technical discussions with FAA subject matter experts
Assisting clients with test plan writing, test data processing, or report generation when requested
Test witnessing and approving client-supplied data/reports

The following services will not be offered:

Engineering design services are not offered. TS Integrators will not assist clients with the design of their products. This is both to maintain impartiality and a third party perspective when reviewing client data as a showing of compliance, and to avoid inadvertent design knowledge transfer from one client to another.
Test execution services beyond the certification services listed above are not offered.

Pricing

Pricing for DER Services is intended to roughly track the overhead rate for comparably experienced engineers averaged across the industry. In most cases however, the resultant billing rate will lag well behind many companies' internal overhead rates. Work performed is billed at a straight time hourly rate and invoiced monthly. Rate increases are applied annually on January 1st to adjust for any increase in cost of living. All customers are billed at the same rate, but late-year PO start dates and multi-year agreements may be handled on a case by case basis.

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