Most research funding goes to making something work. Most technologies that fail do so after they have already been made to work — somewhere between a prototype that flies on a test range and a product anyone can buy. Engineers call that span the valley of death, and it has a number.
On 23 September 2026, the Technology Development Board of the Department of Science and Technology approved ₹285 crore to Ubifly Technologies Private Limited, Chennai, under the Research Development and Innovation (RDI) Fund, to take its indigenous ePlane advanced air mobility platform from Technology Readiness Level 6 to Technology Readiness Level 9. The total approved project cost is ₹570 crore, and the TDB support will be provided through Optionally Convertible Debentures.
The scale itself
The Technology Readiness Level scale was developed by NASA in the 1970s and has since been adopted by defence ministries, space agencies and research funders worldwide. It runs from 1 to 9 and answers a single question: how close is this technology to actually being used?
- TRL 1 — basic principles observed and reported
- TRL 2 — technology concept or application formulated
- TRL 3 — analytical and experimental proof of concept
- TRL 4 — component validation in a laboratory environment
- TRL 5 — component validation in a relevant environment
- TRL 6 — system or subsystem prototype demonstrated in a relevant environment
- TRL 7 — system prototype demonstrated in an operational environment
- TRL 8 — actual system completed and qualified through test and demonstration
- TRL 9 — actual system proven through successful operations
The distinctions that carry most of the meaning are between levels 4, 5 and 6, and they turn on the word environment. A laboratory environment is controlled: temperature, vibration, power and interference are all as the engineer chose them. A relevant environment reproduces the conditions the technology will actually face. An operational environment is those conditions, in the real system, doing the real task.
A great deal of technology works perfectly at TRL 4 and fails at TRL 5, not because the science was wrong but because the world is dirtier, colder, hotter, wetter and more electrically noisy than a bench.
Why 6 to 9 is the expensive span
Moving from TRL 6 to TRL 9 is the most expensive and most failure-prone stretch of the scale, and understanding why explains what this funding is for.
Up to TRL 6 the work is engineering: make it function. From TRL 6 the work is qualification: prove it functions every time, under every condition, for every unit produced, to a standard someone else defines. That second task consumes far more money and time than the first, and it produces no new science at all.
For an aircraft this is especially stark. Certification requires demonstrating airworthiness across the full flight envelope, failure modes, structural margins, software integrity and maintenance procedures, in a process specified by the regulator rather than the engineer. It is a fixed, large cost that does not scale down for a small company or a small aircraft.
The financing problem follows directly. Research grants typically fund the early levels, where the output is knowledge. Commercial investors typically enter at the late levels, where the output is revenue. In between sits a stage that is too applied for a research grant and too unproven for a commercial lender — expensive, slow, and producing nothing saleable until it is finished. This is the valley of death, and it is where a functioning technology quietly stops.
An instrument like the TDB's exists specifically to bridge it. The RDI Fund — the government's ₹1 lakh crore Research Development and Innovation corpus — is designed to put public money into exactly this stage, on the argument that the state is the only actor willing to hold that risk for that long.
The funding mechanism is itself informative. Support is through Optionally Convertible Debentures: the money goes in as debt which the holder may later convert into equity. If the venture succeeds, the government can convert and share in the upside; if it merely survives, the instrument remains a loan to be repaid. This is neither a grant, which returns nothing, nor a pure equity stake, which makes the government an owner from day one. It shares risk without transferring control — which is the design objective when public money backs a private deep-tech firm.
The aircraft
The e200X is a three-seater — one pilot and two passengers — zero-emission advanced air mobility aircraft, with a targeted range of 110 km and an ideal speed of 160 kmph.
The technically interesting feature is the landing gear, designed for both conventional and vertical landing, and the reason is a genuine engineering trade-off worth understanding.
Vertical take-off and landing needs no runway, which is the entire promise of urban air mobility. It is also, in energy terms, expensive: hovering requires the rotors to generate lift equal to the aircraft's full weight with no help from forward motion. Conventional take-off uses a wing, which generates lift from forward airspeed far more efficiently than a rotor generates it from still air — but it needs a runway.
An aircraft that can do both can operate from a confined site when it must and use a strip when one is available, spending less energy in the second case. For a battery-powered aircraft, where stored energy is the binding constraint on range, that flexibility is not a convenience. It is the difference between one trip and several on a single charge, and the release explicitly cites multiple trips per charge as a design intent.
The indigenous content spans vertical rotors, forward propellers, flight-control algorithms, power-distribution controllers and battery-pack modules with integrated cooling systems, with the complete airframe — fuselage, wings and booms — designed in house.
Two of those deserve a note. Flight-control algorithms are not incidental software. A multi-rotor aircraft is aerodynamically unstable by design and is flown by a computer adjusting rotor speeds many times a second; without that control loop it does not fly at all. And battery thermal management is a safety system, not an efficiency one: lithium cells degrade and, in the worst case, enter thermal runaway when they get too hot, and a pack discharging hard enough to lift an aircraft generates a great deal of heat. The cooling system is what makes the energy density usable.
Secretary of the TDB Rajesh Kumar Pathak framed the support as enabling private-sector participation in high-impact technologies and moving innovations closer to deployment. The project is categorised under Deep Technology.
Where this sits
India's aerospace development effort has generally run through government laboratories and public sector undertakings. A private company in Chennai receiving state backing to certify an aircraft of its own design is a different model, and it belongs with the shift described in our explainer on CSIR-NAL's micro gas turbine engines, where propulsion development is being opened up in a similar way.
Whether these aircraft find a market is genuinely unsettled, and an honest answer should say so. Advanced air mobility has attracted large investment worldwide against a business case that remains unproven: the aircraft are expensive, the range is short, the regulatory framework for flying them over populated areas is incomplete, and the ground infrastructure does not exist. A 110 km range and three seats describes a machine for a specific set of journeys — a city to a nearby airport, a hospital transfer, a route across water or difficult terrain — not a replacement for road transport.
What the regulatory question will turn on is covered in our piece on how India investigates an air incident: certifying a new class of aircraft to carry passengers over cities is the hardest thing a civil aviation regulator does, and it is the reason TRL-9 for an aircraft is a far higher bar than TRL-9 for most technologies. The connectivity policy such aircraft would eventually plug into is described in our explainer on the next phase of UDAN, whose helipad component is the nearest existing infrastructure commitment.
The funding decision is best read not as a bet that urban air taxis will succeed, but as a decision that if they do, the aircraft should be one India designed.
🔑 Revision block
- The approval: 23 September 2026 — Technology Development Board (TDB), Department of Science and Technology, approved ₹285 crore to Ubifly Technologies Private Limited, Chennai
- Total project cost: ₹570 crore; TDB Secretary: Rajesh Kumar Pathak
- Fund: the Research Development and Innovation (RDI) Fund, the government's ₹1 lakh crore corpus
- Instrument: Optionally Convertible Debentures — debt that may later be converted to equity; shares risk without transferring control
- Purpose: take the indigenous ePlane from TRL-6 to TRL-9; categorised under Deep Technology
- The aircraft — e200X: three-seater (one pilot, two passengers), zero-emission, targeted range 110 km, ideal speed 160 kmph
- Distinctive feature: landing gear for both conventional and vertical landing
- Indigenous elements: vertical rotors, forward propellers, flight-control algorithms, power-distribution controllers, battery-pack modules with integrated cooling; complete airframe designed in house
- TRL scale: developed by NASA in the 1970s, runs 1 to 9
- TRL 1 basic principles observed · TRL 2 concept formulated · TRL 3 proof of concept · TRL 4 component validation in a laboratory environment · TRL 5 component validation in a relevant environment · TRL 6 prototype demonstrated in a relevant environment · TRL 7 prototype demonstrated in an operational environment · TRL 8 system completed and qualified · TRL 9 system proven in operations
- The valley of death: TRL 6 to 9 — too applied for a research grant, too unproven for commercial finance; the work shifts from making it function to qualifying it
- Why VTOL costs energy: hovering needs rotor lift equal to full aircraft weight with no help from forward motion; a wing produces lift from airspeed far more efficiently
- Flight-control algorithms: a multi-rotor aircraft is aerodynamically unstable and is flown by a computer adjusting rotor speeds continuously
- Battery thermal management: a safety system against cell degradation and thermal runaway, not merely an efficiency measure
🎯 Practice MCQs
Q1. The Technology Readiness Level scale runs from: (a) 1 to 5 (b) 1 to 7 (c) 1 to 9 (d) 1 to 10
→ (c) — developed by NASA in the 1970s.
Q2. TRL-6 denotes: (a) Basic principles observed and reported (b) Component validation in a laboratory environment (c) A system or subsystem prototype demonstrated in a relevant environment (d) An actual system proven through successful operations
→ (c) — TRL-9 is the last of those.
Q3. The distinction between TRL-4 and TRL-5 turns principally on: (a) The size of the funding involved (b) The number of prototypes built (c) Whether a patent has been filed (d) Whether validation occurs in a laboratory or in a relevant environment
→ (d) — the world is dirtier, hotter and noisier than a bench.
Q4. The "valley of death" in technology development refers to: (a) The failure of basic research to produce publishable results (b) The stage too applied for research grants and too unproven for commercial finance (c) The period after a product is launched but before it is profitable (d) The loss of researchers to industry
→ (b) — broadly the TRL 6 to 9 span.
Q5. An Optionally Convertible Debenture is: (a) Debt that the holder may later convert into equity (b) A grant that need not be repaid (c) A share that must be bought back by the company (d) A government guarantee on a bank loan
→ (a) — it shares upside without making the funder an owner from the outset.
Q6. Vertical take-off is energy-expensive compared with conventional take-off because: (a) Vertical flight requires more fuel by regulation (b) Batteries discharge faster at low altitude (c) Vertical take-off needs longer runways (d) Hovering requires rotor lift equal to the full aircraft weight without help from forward motion
→ (d) — a wing generates lift from airspeed far more efficiently.
Q7. The targeted range of the e200X is: (a) 50 km (b) 110 km (c) 250 km (d) 500 km
→ (b) — at an ideal speed of 160 kmph.
Q8. Flight-control algorithms are essential to a multi-rotor aircraft because such an aircraft is: (a) Aerodynamically unstable and must be continuously corrected by computer (b) Too heavy to be flown manually (c) Required by law to be autonomous (d) Unable to carry a pilot
→ (a) — without the control loop it does not fly at all.
Q9. Battery thermal management in an electric aircraft is primarily: (a) A comfort feature for passengers (b) A means of increasing cruise speed (c) A requirement for night operations (d) A safety system against cell degradation and thermal runaway
→ (d) — a pack discharging hard enough to lift an aircraft generates considerable heat.
Q10. Consider the following statements: 1. Moving from TRL-6 to TRL-9 chiefly involves qualification rather than new scientific discovery. 2. Certifying a new class of passenger aircraft is among the most demanding tasks a civil aviation regulator undertakes. Which is/are correct? (a) 1 only (b) 2 only (c) Both 1 and 2 (d) Neither 1 nor 2
→ (c) — which is why TRL-9 for an aircraft is a far higher bar than for most technologies.
📋 How this gets asked (PYQ pattern)
Science and technology policy has become a regular presence in the NDA general ability paper, and this item carries two separately examinable strands.
The scale question asks what TRL means and what its range is. One to nine, NASA origin. The endpoints — TRL-1 basic principles, TRL-9 proven in operations — are the two most asked, and the laboratory-versus-relevant-environment distinction is the discriminating one.
The body question separates the funding institutions, which candidates confuse freely. TDB is the Technology Development Board, under DST, commercialising indigenous technology. DST is the department. DBT handles biotechnology. CSIR runs national laboratories. DRDO is defence research, under the Ministry of Defence. ANRF is the newer apex research funding body. Five acronyms, five distinct functions and parents.
The instrument question asks what a convertible debenture is. This is corporate finance appearing in a science question, and it is worth the thirty seconds it takes to learn: debt now, possibly equity later.
The technology question covers eVTOL, advanced air mobility and the VTOL energy trade-off. The reason hovering costs more energy than wing-borne flight is a physics answer, not a policy one, and it is exactly the kind of thing the NDA paper likes.
For the SSB interview, the honest framing is the strongest one. A candidate asked about urban air mobility who says the technology is real, the business case is unproven, and the government's interest is in owning the design if the market does emerge is giving a considered answer. Uncritical enthusiasm for a technology is easy to produce and easy for an interviewing officer to discount.
Preparing for NDA? Technology-policy questions get much easier once the funding bodies are learnt as a set with their parent departments attached. Build the base with our NDA general ability notes, follow the daily NDA current affairs, and prepare with our faculty in the upcoming Cavalier courses in Delhi.
✍️ Written by Col Vijyanat Thakur — Defence studies faculty at The Cavalier. Reviewed by the Cavalier Faculty Desk.