Special Joint Webinar Recap: STCs — Certificating Advanced Aviation Technologies
- HYSKY Society
- Oct 9
- 6 min read
Hosted by HYSKY and the Vertical Flight Society’s Commercial Air Transport (CAT) Discussion Group • Oct 9, 2025, 11:00 AM–12:00 PM EDT
HYSKY Society and the Vertical Flight Society’s CAT Discussion Group convened a lively, deeply practical webinar on how Supplemental Type Certificates (STCs) are accelerating the entry of advanced propulsion and systems into real aircraft. Moderated by Mike Hirschberg (H2 Advisors), with featured talks by David Webber (FAA) and Ken Swartz (Aeromedia Consultants), the session blended policy mechanics, field-proven history, and what’s next for eVTOLs, hydrogen, hybrid-electric, and battery-electric conversions.
The hour included frank Q&A with industry participants, notably Ed Lovelace (Ampaire), Prakash Patnaik (National Research Council of Canada), and Al Lawless (eVTOL Flight Test Council). Co-hosts Andy Mearns (Multicopter Aerospace LLC) and Danielle McLean (HYSKY founder/CEO) opened and closed the event.
Why STCs Matter Now in Aviation: The Fast Lane for New Tech on Proven Airframes
STCs allow innovators to modify existing, certified aircraft rather than certify clean-sheet designs. That means teams can focus certification on the changed areas—new powerplants, energy systems, avionics, or mission kits—while leveraging the known safety baseline of the parent airframe. As multiple speakers underscored, this becomes a powerful route for hydrogen fuel cell, hybrid-electric, and battery-electric propulsion to reach service sooner and at lower risk.
Regulatory Backbone: Part 21, Categories, Classes, and the “Special Class” Safety Net
The certification scaffolding designers actually use
Mike Hirschberg set the table with a brisk tour of the rules: Part 21 provides type certification procedures; Parts 23/25 (fixed-wing) and 27/29 (helicopter/rotorcraft) define airworthiness standards by category and size. Where no ready-made standard exists (think powered-lift/eVTOL), applicants use 21.17(b) Special Class, tailoring performance-based requirements with the FAA.
Hirschberg also clarified the working difference between amended type certificates (OEM-led major changes for in-production variants) and STCs (often third-party changes to fielded aircraft). The key dividing line: any change that could affect weight, balance, structural strength, reliability, or operational characteristics tips into “major,” driving test and substantiation.
FAA Perspective: How STCs Move from Concept to Issuance
David Webber’s playbook for surviving (and thriving in) certification
David Webber, a flight-test engineer with the FAA, walked the audience through the practical flow of Order 8110.4—a left-to-right progression from concept familiarization and certification basis to means of compliance, type inspection authorization, and flight test. In reality, he cautioned, it’s an iterative loop: flight testing reveals design realities, which may force requirements refinements, equivalent safety findings, or even updates to the certification basis.
Two field rules from Webber stood out:
Group your “birds of a feather.” The NAS works best when aircraft can be clustered by shared flying qualities and performance, enabling common training, infrastructure, and procedures.
Bring flight test in early. FAA flight-test teams need a holistic picture of the modifications and all systems they touch. Many STC programs “own” more of the aircraft than they initially expect once interfaces and cascading effects emerge (icing, power, thermal, software, etc.).
The deliverable at the end is the Type Certificate Data Sheet (TCDS) for the modified product: a legally enforceable record of the certification basis, limitations, and what was actually approved.
Field Provenances: A Century of Upgrades Points to an Electric/Hydrogen Future
Ken Swartz’s tour of real STCs in the wild—and what they signal next
Ken Swartz zoomed out with a photographer’s eye and a historian’s memory, showing how STCs have long extended the life and utility of airframes:
Fixed-wing engine retrofits: Convair 580 radial-to-turboprop conversions, CFM56 re-engining of DC-8s and KC-135s, and wide use of the PT6 and Garrett/Honeywell turboprops on ag aircraft.
Helicopter upgrades: From the S-58 piston-to-turbine conversion to Eagle Copters’ Bell 407 re-engining for hot-and-high fire missions, and data-plate migrations within OEM families that demonstrate structured pathways for capability growth.
Cabin and mission kits: Air medical interiors, cargo hooks, winches, emergency floats, bubble windows, heaters, and baskets—everyday STCs that will inevitably carry into eVTOL/ECTOL fleets.
Swartz then connected dots to today’s electrification wave: Tier 1/United Therapeutics’ battery-electric R44, Harbour Air/MagniX’s eBeaver, Diamond’s eDA40, CAE/H55/Safran’s trainer work, Robinson/MagniX on the R66, ZeroAvia’s Q400 hydrogen plans, and Ampaire’s hybrid Caravan. The message: we’ve done this before—new powerplants on proven wings and rotors—so the STC road is familiar, even if the technologies are new.
Speaker Deep Dives: What Each Brought to the Table
H2 Advisors’ Mike Hirschberg — “Use the path that fits; shape the path that doesn’t”
Hirschberg oriented attendees to where different programs fit in the regs and how to pick the right certification lane. He reminded teams that electric motors may be treated as engines for certification purposes (to fit into Part 33), and that a successful STC hinges on clear scoping of major vs. minor changes and disciplined substantiation. He also spotlighted Unither Bioelectronics Project Proticity with Robinson Helicopter Company which is a hydrogen helicopter demonstrations—like the R44 testbed and the R66 turbine pathway—that could flow into production via STCs, delivering emissions-free rotorcraft without reinventing the entire aircraft.
FAA’s David Webber — “Plan for iteration; invite flight test early”
Webber emphasized the performance-based ethos now common in Part 23 and Special Class, which allows applicants to propose innovative means of compliance so long as safety objectives are met. He urged developers to budget for discover-and-revise loops during flight test and to surface interdependencies (icing systems, thermal limits, operating manuals, Subpart B & G areas) before TIA. His bottom line: efficiency and safety both improve when certification and flight test are integrated from day one.
Aeromedia Consultants’ Ken Swartz — “History says STCs will carry the next revolution”
Swartz showed how retrofits create markets: lower DOCs, improved performance, and mission-specific configurations have repeatedly rejuvenated airframes. He argued the same dynamics will propel electric, hybrid, and hydrogen conversions—especially in training, regional mobility, and specialized missions. Expect the “everyday STCs” (floats, interiors, mission kits) to follow eVTOL/ECTOL into service, just as they did in helicopters and commuters.
The Q&A: Practitioners Weigh In on What’s Hard (and What Works)
Ampaire’s Ed Lovelace — “Hybrid STC on Caravan: familiar shape, new details”
Ed Lovelace, CTO at Ampaire, offered a program snapshot: an STC for the Cessna Grand Caravan that mirrors traditional powerplant upgrades in structure but integrates an “amp-drive” parallel hybrid with high-voltage battery and a new propeller. Ampaire is also advancing a powertrain type certificate—the FAA’s first formal hybrid powertrain program of record—through PSCP and G-1, now deep into special conditions tailored for hybrids.
Two takeaways from Lovelace:
Why hybrid? A slightly heavier system with dramatically better specific fuel consumption yields 50–70% fuel savings. Because you carry less than half the fuel, there’s a payload–range crossover where the hybrid can carry more than the baseline turbine.
What’s tricky? Swapping a turbine for a compression-ignition (diesel) engine removes bleed air. Teams must re-provide functions like de-ice (boots compressors or TKS) and air-conditioning electrically. Otherwise, “no major surprises” so far—development flight testing continues toward commercial-intent configuration and envelope corner-points.
NRC Canada’s Prakash Patnaik — “Materials and fatigue STCs are real certification work”
Prakash Patnaik recounted STC campaigns on PT6 components and titanium fittings, emphasizing the materials science and fatigue rigor behind successful approvals. NRC’s labs often host witnessed testing for Transport Canada and the FAA. He also flagged ongoing defense-side work in electrification and hydrogen for a net-zero 2050 horizon.
eVTOL Flight Test Council’s Al Lawless — “Same STC process, more coupling for VTOL”
Al Lawless agreed the STC framework will apply to AAM aircraft, but warned of tighter coupling—heat sinking, battery duty cycles, and system interdependencies can make changes more involved than a conventional single-engine swap.
Audience Prompts that Moved the Discussion
Eve Morrier pushed the conversation beyond engines to avionics and autopilots. Panelists noted that non-propulsion STCs (from autopilots to interiors) are common today and will be equally relevant for eVTOL/ECTOL fleets.
George Bryan asked about SAF and unleaded avgas. Hirschberg summarized the progression from engine-specific approvals (via STCs) toward broader allowances as experience grows; the same staged pattern is instructive for electrification and hydrogen transitions.
Practical Guidance Heard Between the Lines
What developers should do now
Map your change ripple-effects early. If your STC touches icing, ECS, or manuals, plan to own those areas in test and compliance.
Bring in the FAA flight-test team during concept familiarization. Early exposure reduces surprises and accelerates means-of-compliance alignment.
Use STCs strategically. For many missions, retrofitting a proven airframe is the fastest, cheapest, least risky on-ramp for low-emission propulsion.
Expect iteration. Flight testing will refactor assumptions; build schedule and budget to handle loop-backs.
Looking Ahead: SAF vs. Hydrogen vs. Batteries—Future Session Teed Up
HYSKY and speakers signaled interest in a follow-on webinar demystifying the alphabet soup of decarbonization: SAF, hydrogen, and battery-electric—their use cases, limits, and cross-over points. As Danielle noted, hydrogen isn’t labeled “SAF,” which confuses newcomers; a side-by-side explainer will help the broader ecosystem align on fit-for-purpose solutions.
Event Notes and Credits
Who, when, where
Title: STCs — Certificating Advanced Aviation Technologies
Date/Time: Oct 9, 2025, 11:00 AM–12:00 PM EDT
Speakers: Mike Hirschberg (H2 Advisors), David Webber (FAA), Ken Swartz (Aeromedia Consultants)
Co-Hosted by: HYSKY and the Vertical Flight Society (CAT Discussion Group)
Moderator: H2 Advisors (Mike Hirschberg)
Thanks to: Andrew Mearns (Multicopter Aerospace LLC), Danielle McLean (HYSKY), Tom Risen (VFS), and participants Ed Lovelace, Prakash Patnaik, Al Lawless, Eve Morrier, George Bryan, and a highly engaged audience.
Closing & Call to Action
HYSKY thanks all presenters and participants for a concise, rich walk through how STCs enable innovation without compromising safety. From Part 21 mechanics to hands-on retrofit experience, the message was consistent: smart certification strategies are the bridge between breakthrough tech and scalable operations.
Join us next: FLYING HY on November 5 — details and registration at hysky.org (tickets $30). We’ll continue bringing regulators, operators, and innovators together to decarbonize aviation with hydrogen and allied technologies—one pragmatic step, and one certified modification, at a time.on
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