As eVTOL aircraft prepare for early operations next year, one key aspect seems to be overlooked: the use of runways. Utilizing both vertical and conventional capabilities could be the key to unlocking the full potential of eVTOLs.
I recently discovered an interesting fact about the Lockheed Martin F-35B stealth military aircraft. The F-35B is technically classified as a powered-lift aircraft because of its ability to operate vertically and transition to wing-borne lift, but its VTOL capability is only used for about 10 percent of its flights.
This is because VTOL is not energy efficient, given the significant amount of power needed to lift 30,000-plus pounds (13,600-plus kilograms) off the ground, which is why for the other 90 percent, the F-35B takes off and lands from a runway just like its VTOL-less sibling, the F-35A.
The F-35B’s VTOL capability is essentially reserved for when it needs to operate from short runways, land on non-carrier ships, or simply for showing off its superior leaf blower capabilities at an airshow. When you think about it, the F-35B’s VTOL capability is kind of like the Ludicrous mode in a Tesla: impressive, but not practical for everyday trips to the grocery store.
Like all helicopters, the F-35B can hover superbly with its unified flight controls, but the overall design makes its VTOL capability more of a “we can do it, but we don’t like to,” simply because of the massive amount of power required and associated weight restrictions.
A fantastic powered-lift aircraft that is better suited for hovering — as opposed to air-to-air combat — is the Bell Boeing CV-22 Osprey. The CV-22 design incorporates two huge rotors connected to engines that tilt vertically for landing, and horizontally for forward flight. However, this powered-lift design also requires performance trade-offs.
To hover a 50,000-plus-pound (22,680-plus-kilogram) aircraft, you need very large rotors. Because the diameter of the rotors is larger than the height of the CV-22 airframe, the aircraft can’t land with the engine nacelles in the fully horizontal position since the rotors would strike the runway on touchdown. In addition, because of the sheer size of the rotors and power, the CV-22 produces hurricane-speed downwash, and conducting fast-rope operations from the CV-22 requires that the fast-rope is weighted at the end so that it remains on the ground and not in the rotors.
For any powered-lift design, there are always design trade-offs depending on the mission, and for the military, being energy efficient may not always be at the top of their design priorities. Neither the F-35B nor the CV-22 can be considered eco-friendly, but in this instance, one design is far better at hovering, which is understandable given the inherently different mission roles these two aircraft have.
For in-filling and ex-filling SEAL Team 6, we want a powered-lift like the CV-22 that can hover until the cows come home. For a stealth fighter, we want thrust vectoring, a $500,000 helmet with head tracking, and enough explosive firepower to rival a Michael Bay movie.
When you think about it, the F-35B’s VTOL capability is not what matters the most. Instead, the military has figured out that vertical operations are not practical for every mission and that short/conventional takeoff or landing (STOL/CTOL) should be a primary means, given that it is much more energy efficient and allows for more weight to be carried.
While the military can afford to prioritize power over energy efficiency, the advanced air mobility (AAM) industry faces different pressures. For eVTOLs, energy efficiency isn’t just a goal — it’s a necessity to ensure commercial viability. In the past decade, batteries have made electric cars capable of achieving equivalent distances on a single charge compared to most gas-powered cars. However, battery technology is nowhere near capable of producing comparable ranges to traditional aircraft of the same size and capacity as electric aircraft.
For now, battery technology makes eVTOLs possible, but not quite as range-capable as traditional airplanes or helicopters. However, where the range is lacking, eVTOLs have various other attributes that make them preferable for urban and regional air travel, given they are quieter and operate carbon-free. Being safe, quiet, and easy to operate is non-negotiable for any electric aircraft operator looking to fly in urban environments.
Unlike the F-35B, an electric aircraft must also be cost-effective to operate in order to be affordable to the masses. As with every commercial aviation operator, the never-ending challenge lies in minimizing operating costs without compromising on safety. To achieve this, operators employ various strategies.
For traditional airlines, fuel has always been a significant operational cost, which is why the airlines are constantly searching for new ways to improve fuel efficiency through perfecting flight routes, optimizing airport landing and takeoff sequencing, and engineering turbofan engines to be as fuel efficient as possible. Similarly, eVTOL operators will need to identify areas where overall operational expenses can be curbed. However, instead of fuel, eVTOL operators will need to look to other means to achieve cost savings.
For eVTOLs, energy efficiency is the second most important operational factor — the first being safety. While these aircraft are designed for vertical takeoff, they must transition to wing-borne flight quickly to conserve energy, reduce strain on batteries, and maximize range. This is why most eVTOL developers say, “We don’t hover. We take off and land vertically.”
So why not take advantage of these aircraft’s wing-borne capabilities for takeoff and landing, and use CTOL or even STOL when possible? It’s a huge operational capability that can save immensely on energy usage, not to mention wear and tear on the batteries and electric engines.
Some eVTOL manufacturers have included conventional runway capabilities in their aircraft designs, but they de-emphasize this feature as a safety measure for when VTOL is not possible due to bad weather. Some even consider CTOL to be for emergency situations only, such as when energy reserves fall below an amount where vertical landing is no longer possible.
While eVTOLs can easily take off and land vertically, these operations place significant stress on engines and battery systems due to the massive energy requirements. Hovering, in particular, can drastically reduce flight range, making conventional takeoff and landing far more efficient. But why is that the case? It’s a matter of power needed to sustain a hover. Every second maintained in a hover consumes huge amounts of energy, making hovering in an electric aircraft extremely inefficient.
Most current eVTOL manufacturers are fine with this drawback because hovering for extended periods is not what eVTOLs are designed for. The current cadre of eVTOLs is designed to take off and transition as quickly as possible to wing-borne flight to be as energy efficient as possible. The same is true for landing vertically.
This is why eVTOLs should also be capable of conducting normal CTOL/STOL operations from runways. It just makes sense from a wear and tear, energy management, and safety perspective to conduct a normal takeoff when there’s a perfectly good runway available.
Not implementing CTOL into normal operations is like having a 50 percent off fuel savings coupon and not using it. It’s a major operational capability that can significantly increase the range of an electric aircraft. I predict that future eVTOL operators will be looking to reduce overall costs and maintenance, and having an eVTOL that can also operate from a runway and the pad will be far more attractive in the long run. This is especially true if the route ends or begins at a smaller regional or general aviation airport with an under-utilized runway.
In the continued push to revolutionize air travel, runways shouldn’t be overlooked. The ability to land on a conventional runway is not just a backup — it’s a powerful tool that can extend range, reduce maintenance, and make eVTOL operations more efficient. As AAM evolves, we may find that runways are the key to unlocking the full potential of electric flight. As every pilot knows, the three most useless things in aviation are the runway behind you, the altitude above you, and the fuel left in the fuel truck. For AAM, ignoring the ability to use runways could be just as wasteful as leaving fuel behind.
Erin Rivera is a seasoned attorney and regulatory expert specializing in aviation and emerging technologies. Currently serving with the Federal Aviation Administration (FAA) in Washington, D.C., Erin has previously worked for a leading eVTOL developer. In addition to his professional expertise, he is a pilot and a helicopter flight crew veteran.