Rolls-Royce completes ground-testing of technology set to power the world’s fastest all-electric plane: ACCEL

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Rolls-Royce has completed testing of the technology that will power the world’s fastest all-electric plane. All the technology has been tested on a full-scale replica of the plane’s core—called an ‘ionBird’—including a 500hp electric powertrain powerful enough to set world speed records and a battery with enough energy to supply 250 homes. The plane is part of a Rolls-Royce initiative called ACCEL, short for “Accelerating the Electrification of Flight”.

The ACCEL project team includes key partners YASA, the electric motor and controller manufacturer, and aviation start-up Electroflight. The team has been developing the technology while adhering to the UK Government’s social distancing and other health guidelines; the systems will soon be integrated into Rolls-Royce’s ‘Spirit of Innovation’ plane. There is a long history of iron-birds in aviation for testing propulsion systems ahead of flight; in this case Rolls-Royce named the test airframe “ionBird”, after the zero-emission energy source propelling the aircraft. 

The dedicated team have tested each and every component of the system including running the propeller up to full speed (approximately 2,400 rpm) using the most power-dense battery pack ever assembled for aircraft propulsion. When at full power during the flight-testing phase, it will propel the aircraft to more than 300 mph setting a new world speed record for electric flight.

More than 6,000 cells are packaged in the battery for maximum safety, minimum weight and full thermal protection. Since January, engineering and test pilots have spent many hours optimizing the system and developing operating procedures for electric flight. GBs of data—generated every hour of operation—are analyzed to improve performance wherever possible. 

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Rolls-Royce is committed to playing a leading role in reaching net zero carbon by 2050.The completion of ground-testing for the ACCEL project is a great achievement for the team and is another important step towards a world record attempt. This project is also helping to develop Rolls-Royce’s capabilities and ensure that we remain a leader in delivering the electrification of flight, an important part of our sustainability strategy. —Rob Watson, Director – Rolls-Royce Electrical

Bremont will be the official timing partner for the all-electric speed record attempt. The British luxury watch maker has also helped develop the design of the plane’s cockpit which will feature a stopwatch, while the company has machined canopy release parts at its Henley-on-Thames manufacturing facility. 

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The first flight is planned for later this year; the aim is to beat the current all-electric flight world record early next year. Half of the project’s funding is provided by the Aerospace Technology Institute (ATI), in partnership with the Department for Business, Energy & Industrial Strategy and Innovate UK. The ACCEL project is the first Rolls-Royce project to use offsetting to make the whole program carbon neutral. The company also hopes to inspire young people with the ACCEL project to consider STEM careers (Science, Technology, Engineering and Math).

Link: https://www.greencarcongress.com/2020/10/20201001-accel.html

World First Hydrogen-Electric Passenger Plane Flight

Given the role that metrology plays in the manufacturing and support of commercial and military aviation Metrology.News believes that the following news story is of measurable significance, and worthy of bringing to the attention of the metrology sector, as the aviation industry takes a step-forward in decarbonising commercial aviation. 

ZeroAvia, a leading innovator in decarbonising commercial aviation, has completed the world first hydrogen fuel cell powered flight of a commercial-grade aircraft. The flight took place at the company’s R&D facility in Cranfield, England, with the Piper M-class six-seat plane completing taxi, takeoff, a full pattern circuit, and landing. 

ZeroAvia’s achievement is the first step to realising the transformational possibilities of moving from fossil fuels to zero-emission hydrogen as the primary energy source for commercial aviation. Eventually, and without any new fundamental science required, hydrogen-powered aircraft will match the flight distances and payload of the current fossil fuel aircraft. 

This major milestone on the road to commercial zero-emission flight is part of the HyFlyer project, a sequential R&D programme supported by the UK Government and follows the UK’s first ever commercial-scale battery-electric flight, conducted in the same aircraft in June. ZeroAvia will now turn its attention to the next and final stage of its six-seat development program – a 250-mile zero emission flight out before the end of the year. The demonstration of this range is roughly equivalent to busy major routes such as Los Angeles to San Francisco or London to Edinburgh. 

​“It’s hard to put into words what this means to our team, but also for everybody interested in zero-emission flight. While some experimental aircraft have flown using hydrogen fuel cells as a power source, the size of this commercially available aircraft shows that paying passengers could be boarding a truly zero-emission flight very soon. All of the team at ZeroAvia and at our partner companies can be proud of their work getting us to this point, and I want to also thank our investors and the UK Government for their support.” comment’s Val Miftakhov, ZeroAvia CEO. 

ZeroAvia’s innovation programme in the UK is part-funded through the UK Government’s Aerospace Technology Institute (ATI) Programme. Through the HyFlyer project, ZeroAvia is working with key partners the European Marine Energy Centre (EMEC) and Intelligent Energy to decarbonise medium-range small passenger aircraft by demonstrating powertrain technology to replace conventional engines in propeller aircraft. Intelligent Energy will optimise its high power fuel cell technology for application in aviation whilst EMEC, producers of green hydrogen from renewable energy, will supply the hydrogen required for flight tests and develop a mobile refuelling platform compatible with the plane. 

In addition to all the aircraft work, ZeroAvia and EMEC have developed the Hydrogen Airport Refuelling Ecosystem (HARE) at Cranfield Airport – a microcosm of what the hydrogen airport ecosystem will look like in terms of green hydrogen production, storage, refuelling and fuel cell powered-flight.

This also marks another world’s first – a fully operational hydrogen production and refueling airport facility for primary commercial aircraft propulsion. The successful flight represents good news for the aviation industry’s role in supporting the net zero transition, but also raises hopes for innovation that can reduce commercial challenges in the medium term, particularly important for the industry as it considers the post pandemic recovery.

ZeroAvia’s hydrogen-electric powertrain is projected to have lower operating costs than its jet-fuelled competition due to lower fuel and maintenance costs. The company plans to control hydrogen fuel production and supply for its powertrains, and other commercial customers, substantially reducing the fuel availability and pricing risks for the entire market.

Link: https://metrology.news/world-first-hydrogen-electric-passenger-plane-flight/

BEA releases final report on Air France Airbus A380 fan failure accident over Greenland

Status:Final
Date:Saturday 30 September 2017
Time:ca 09:45
Type:
Airbus A380-861
Operator:Air France
Registration:F-HPJE
C/n / msn:052
First flight:2010-08-10 (7 years 2 months)
Total airframe hrs:27184
Engines:Engine Alliance GP7270
Crew:Fatalities: 0 / Occupants: 24
Passengers:Fatalities: 0 / Occupants: 497
Total:Fatalities: 0 / Occupants: 521
Aircraft damage:Substantial
Aircraft fate:Repaired
Location:over southern Greenland (   Greenland)
Phase:En route (ENR)
Nature:International Scheduled Passenger
Departure airport:Paris-Charles de Gaulle Airport (CDG/LFPG), France
Destination airport:Los Angeles International Airport, CA (LAX/KLAX), United States of America
Flightnumber:AF066

Narrative:
An Air France Airbus A380, operating flight 66 from Paris-Charles de Gaulle Airport, France, to Los Angeles International Airport, California, USA, diverted to Goose Bay, Canada after suffering an uncontained GP7270 engine failure over Greenland.
The aeroplane took off at 09:50 UTC with the three pilots (the captain and two first officers, FO/1 and FO/2) in the cockpit. The cruise altitude (FL 330) was reached around 25 minutes later. The crew agreed on the division of the rest time. FO/2 took the first duty period around 30 minutes after take-off. The aeroplane changed levels several times during the cruise and then stabilized at FL370 at 11:14.
At 13:48, the crew asked Gander Oceanic to climb to FL380. The controller accepted and asked them to report when reaching FL380. The low pressure compressor and turbine rotation speed (N1) of the four engines increased from 98% to 107%.
At 13:49, the titanium fan hub of the right outer engine (No 4) separated into at least three parts. This failure was the result of the progression of a crack originating in the part’s subsurface. The central fragment of the hub stayed attached to the coupling shaft between the low pressure compressor and the low pressure turbine. The two other hub fragments were ejected, one upwards and the other downwards. The interaction between the liberated fan rotor fragments and the fixed parts of the engine caused the destruction of the engine casing and the separation of the air inlet which fell to the ground. Debris struck the wing and airframe without affecting the continuation of the flight.

After the failure, the aeroplane’s heading increased by three degrees to the right in three seconds, and there were vibrations in the airframe for around four seconds.
The crew perceived these variations and associated them with engine surging by analogy with the sensations reproduced in simulator sessions. An “ENG 4 STALL” ECAM message came up. The captain requested the “ECAM actions”. He engaged Autopilot 1 and indicated that he was taking the controls and would thus be Pilot Flying. He reduced engine No 4 thrust by positioning the associated lever to IDLE. The engine performed an automatic shutdown and the FO/2 confirmed the sequence by depressing the Engine 4 Master and Engine 4 fire pushbuttons, a few seconds later.

The damaged engine could not be seen from the cockpit or in the image from the camera located on the fin of the A380. A member of the cabin crew brought to the cockpit, a photo of the engine taken by a passenger with his smartphone.
FO/1 who had returned to the cockpit to help the flight crew on duty, went to the upper deck to assess the damage and take other photos. He observed damage on the leading edge slats and small vibrations in the flaps.

From the time of the failure and for around 1 min 30 s, the CAS had decreased from 277 kt to 258 kt and level flight at FL370 was maintained. The captain noticed this reduction in speed and decided to descend to the drift-down level calculated by the FMS (EO MAX FL 346) to maintain a constant speed in level flight. Observing that it was not possible to hold this level and this speed, he continued descending level by level. He selected FL 360, FL 350 then FL 330 and lastly FL 310. The level by level descent obliged the crew to stop their ECAM actions each time a descent was initiated. During level flight at FL310, the N1 rotation speeds of the three remaining engines decreased to 103%. The captain stabilized the descent to FL290 with a constant speed (CAS was 290 kt) by keeping the three engines in maximum continuous thrust (MCT). He decided to continue the descent and stabilize at FL270 in order to spare the engines to destination. The speed stabilized at 279 kt. Around five minutes after the A380 had started its descent, the controller in the Gander Oceanic control centre with which the crew were in datalink contact (CPDLC), detected the deviation from the vertical profile of the path and sent a message: “ATC NOW SHOWS YOU FL330. IS THERE A PROBLEM”.

At the same time, the control centre received an audio Mayday message from AF066, relayed by another aeroplane. One minute later, the PM replied to the CPDLC question with a MAYDAY. Direct audio communication between the flight and ATC resumed a few minutes later.

The crew decided, in agreement with Air France’s Operational Control Centre , to divert to Goose Bay airport and asked the controller for a direct route. After studying the available approaches and taking into consideration the captain’s experience and the airport’s immediate environment, the crew confirmed the selection of Goose Bay airport as the alternate airfield even though it was at a greater distance than Kangerlussuaq airport in Greenland.
The crew started the descent to Goose Bay and were cleared to carry out the RNAV GNSS RWY 26 approach. They were then cleared to land on runway 26. They configured the aeroplane for landing. On approaching the altitude of 1,000 ft, the captain disconnected Autopilot 1 and the flight director (FD) and continued the landing in manual flight. The aeroplane landed at 15:42. The taxiing phase to the stand took some time due to having to stop several times so that the airport services could collect the debris which had fallen onto the runway during the landing. At 16:22, all the engines were shut down.

Probable Cause:
Contributing factors
The following factors may have contributed to the failure of the fan hub on engine No 4:
– engine designer’s/manufacturer’s lack of knowledge of the cold dwell fatigue phenomenon in the titanium alloy, Ti-6-4;
– absence of instructions from the certification bodies about taking into accout macro-zones and the cold dwell fatigue phenomenon in the critical parts of an engine, when demonstrating conformity;
– absence of non-destructive means to detect the presence of unusual macro-zone in titanium alloy parts;
– an increase in the risk of having large macro-zones with increased intensity in th Ti-6-4 due to bigger engines, and in particular, bigger fans.
Accident investigation:

Investigating agency: BEA Status:Investigation completedDuration: 3 yearsAccident number:BEA2017-0568Download report:Final report:  https://www.bea.aero/uploads/tx_elydbrapports/BEA2017-0568.en.pdf

Link: https://aviation-safety.net/database/record.php?id=20170930-1

IndiGo completes replacing A320 Neo aircraft engines

  • Budget carrier IndiGo has completed replacing engines for Pratt & Whitney (PW)-run A320neos, sources told CNBC-TV18.
  • The airline has now installed modified engines on 128 A320neo aircraft.
  • GoAir is yet to complete engine replacement exercise for around 20 neo aircraft.

IndiGo has completed engine replacement exercise for 128 Pratt & Whitney-powered A320neo aircraft, ahead of the Aug 31 deadline, sources close to the development told CNBC-TV18.

In October and November 2019, the Directorate General of Civil Aviation had found issues in the low-pressure turbine of the PW-run A320neos. There were incidents of LPT breakage, leading to engine vibration and the return of aircraft to the ground. As a result, DGCA had asked IndiGo and GoAir, the two operators of such aircraft in India, to install modified engines.

As of August 27, IndiGo has installed 256 modified engines on its 128 A320neos and has completed engine replacement exercise, officials said.

GoAir is yet to install modified engines on its A320neos which run on Pratt & Whitney engines.

“GoAir is yet to replace engines of around 20 A320neo aircraft,” officials added.

It is important to note that as the government has currently mandated airlines to operate with only 45 percent capacity due to COVID-19, GoAir is operating a reduced fleet and hence, is using only those PW-run A320neos which have both engines modified, officials further added.

It is expected that in view of this scenario, DGCA may extend the deadline for GoAir to complete engine replacement exercise.

About 40 percent of the domestic seat capacity of India is powered by Pratt & Whitney neo engines.

Pratt & Whitney has been in the spotlight in the Indian aviation space since 2016 when India’s largest airline IndiGo started facing delivery delays in A320neo aircraft amid issues related to cooling down and a start-up time of the engine, reliability, combustion chamber lining, oil seal and fan blades.

In fact, in 2018, India’s aviation regulator DGCA grounded as many as 14 Airbus A320neos following warning of a potential in-flight shutdown in a sub-category of its Pratt & Whitney engines.

Link: https://www.cnbctv18.com/aviation/indigo-completes-replacing-a320-neo-aircraft-engines-6762611.htm

With Ultralight Lithium-Sulfur Batteries, Electric Airplanes Could Finally Take Off



Oxis Energy’s design promises outstanding energy density, manufacturability, and safety

By Mark Crittenden

A jet airliner with batteries for engines.
Photo-illustration: Edmon de Haro

Electric aircraft are all the rage, with prototypes in development in every size from delivery drones to passenger aircraft. But the technology has yet to take off, and for one reason: lack of a suitable battery.

For a large passenger aircraft to take off, cruise, and land hundreds of kilometers away would take batteries that weigh thousands of kilograms—far too heavy for the plane to be able to get into the air in the first place. Even for relatively small aircraft, such as two-seat trainers, the sheer weight of batteries limits the plane’s payload, curtails its range, and thus constrains where the aircraft can fly. Reducing battery weight would be an advantage not only for aviation, but for other electric vehicles, such as cars, trucks, buses, and boats, all of whose performance is also directly tied to the energy-to-weight ratio of their batteries.

For such applications, today’s battery of choice is lithium ion. It reached maturity years ago, with each new incremental improvement smaller than the last. We need a new chemistry.

Since 2004 my company, Oxis Energy, in Oxfordshire, England, has been working on one of the leading contenders—lithium sulfur. Our battery technology is extremely lightweight: Our most recent models are achieving more than twice the energy density typical of lithium-ion batteries. Lithium sulfur is also capable of providing the required levels of power and durability needed for aviation, and, most important, it is safe enough. After all, a plane can’t handle a sudden fire or some other calamity by simply pulling to the side of the road.

The new technology has been a long time coming, but the wait is now over. The first set of flight trials have already been completed.

Fundamentally, a lithium-sulfur cell is composed of four components:

  • The positive electrode, known as the cathode, absorbs electrons during discharge. It is connected to an aluminum-foil current collector coated with a mixture of carbon and sulfur. Sulfur is the active material that takes part in the electrochemical reactions. But it is an electrical insulator, so carbon, a conductor, delivers electrons to where they are needed. There is also a small amount of binder added to ensure the carbon and sulfur hold together in the cathode.
  • The negative electrode, or anode, releases electrons during discharge. It is connected to pure lithium foil. The lithium, too, acts as a current collector, but it is also an active material, taking part in the electrochemical reaction.
  • A porous separator prevents the two electrodes from touching and causing a short circuit. The separator is bathed in an electrolyte containing lithium salts.
  • An electrolyte facilitates the electrochemical reaction by allowing the movement of ions between the two electrodes.

These components are connected and packaged in foil as a pouch cell. The cells are in turn connected together—both in series and in parallel—and packaged in a 20 ampere-hour, 2.15-volt battery pack. For a large vehicle such as an airplane, scores of packs are connected to create a battery capable of providing tens or hundreds of amp-hours at several hundred volts.

Lithium-sulfur batteries are unusual because they go through multiple stages as they discharge, each time forming a different, distinct molecular species of lithium and sulfur. When a cell discharges, lithium ions in the electrolyte migrate to the cathode, where they combine with sulfur and electrons to form a polysulfide, Li2S8. At the anode, meanwhile, lithium molecules give up electrons to form positively charged lithium ions; these freed electrons then move through the external circuit—the load—which takes them back to the cathode. In the electrolyte, the newly produced Li2S8 immediately reacts with more lithium ions and more electrons to form a new polysulfide, Li2S6. The process continues, stepping through further polysulfides, Li2S4 and Li2S2, to eventually become Li2S. At each step more energy is given up and passed to the load until at last the cell is depleted of energy.

Recharging reverses the sequence: An applied current forces electrons to flow in the opposite direction, causing the sulfur electrode, or cathode, to give up electrons, converting Li2S to Li2S2. The polysulfide continues to add sulfur atoms step-by-step until Li2S8 is created in the cathode. And each time electrons are given up, lithium ions are produced that then diffuse through the electrolyte, combining with electrons at the lithium electrode to form lithium metal. When all the Li2S has been converted to Li2S8, the cell is fully charged.

This description is simplified. In reality, the reactions are more complex and numerous, taking place also in the electrolyte and at the anode. In fact, over many charge and discharge cycles, it is these side reactions that cause degradation in a lithium-sulfur cell. Minimizing these, through the selection of the appropriate materials and cell configuration, is the fundamental, underlying challenge that must be met to produce an efficient cell with a long lifetime.

Anatomy of a Battery

A lithium-sulfur cell goes through stages as it discharges [left]. In each stage, lithium ions in the electrolyte flow to the cathode, where they form polysulfides having ever higher sulfur-to-lithium ratios. Charging reverses the process. Cells are linked into battery packs, which themselves fit into a casing, along with battery-management devices.

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img Illustration: Chris Philpot

One great challenge for both lithium-ion and lithium-sulfur technologies has been the tendency for repeated charging and discharging cycles to degrade the anode. In the case of lithium ion, ions arriving at that electrode normally fit themselves into interstices in the metal, a process called intercalation. But sometimes ions plate the surface, forming a nucleus on which further plating can accumulate. Over many cycles a filament, or dendrite, may grow until it reaches the opposing electrode and short-circuits the cell, causing a surge of energy, in the form of heat that irreparably damages the cell. If one cell breaks down like this, it can trigger a neighboring cell to do the same, beginning a domino effect known as a thermal runaway reaction—in common parlance, a fire.

With lithium-sulfur cells, degradation of the lithium-metal anode is also a problem. However, this occurs via a very different mechanism, one that does not involve the formation of dendrites. In lithium-sulfur cells, uneven current densities on the anode surface cause lithium to be plated and stripped unevenly as the battery is charged and discharged. Over time, this uneven plating and stripping causes mosslike deposits on the anode that react with the sulfide and polysulfides in the electrolyte. These mosslike deposits become electrically disconnected from the bulk anode, leaving less of the anode surface available for chemical reaction. Eventually, as this degradation progresses, the anode fails to operate, preventing the cell from accepting charge.

Developing solutions to this degradation problem is crucial to producing a cell that can perform at a high level over many charge-discharge cycles. A promising strategy we’ve been pursuing at Oxis involves coating the lithium-metal anode with thin layers of ceramic materials to prevent degradation. Such ceramic materials need to have high ionic conductivity and be electrically insulating, as well as mechanically and chemically robust. The ceramic layers allow lithium ions to pass through unimpeded and be incorporated into the bulk lithium metal beneath.

We are doing this work on the protection layer for the anode in partnership with Pulsedeon and Leitat, and we’re optimistic that it will dramatically increase the number of times a cell can be discharged and charged. And it’s not our only partnership. We’re also working with Arkema to improve the cathode in order to increase the power and energy density of the battery.

Indeed, the key advantage of lithium-ion batteries over their predecessors—and of lithium sulfur over lithium ion—is the great amount of energy the cells can pack into a small amount of mass. The lead-acid starter battery that cranks the internal combustion engine in a car can store about 50 watt-hours per kilogram. Typical lithium-ion designs can hold from 100 to 265 Wh/kg, depending on the other performance characteristics for which it has been optimized, such as peak power or long life. Oxis recently developed a prototype lithium-sulfur pouch cell that proved capable of 470 Wh/kg, and we expect to reach 500 Wh/kg within a year. And because the technology is still new and has room for improvement, it’s not unreasonable to anticipate 600 Wh/kg by 2025.

When cell manufacturers quote energy-density figures, they usually specify the energy that’s available when the cell is being discharged at constant, low power rates. In some applications such low rates are fine, but for the many envisioned electric aircraft that will take off vertically, the energy must be delivered at higher power rates. Such a high-power feature must be traded off for lower total energy-storage capacity.

Photo of an airplane.
Photo of a man standing over a machine.
Photos: Bye Aerospace; Oxis Energy
All Amped Up: Bye Aerospace’s eFlyer 2 [top] is designed to train pilots. Bye is working with Oxis Energy on a lithium-sulfur battery that promises to increase the plane’s range. Here a reel of positive electrode, made of sulfur, is being coated onto a current collector [bottom].  

Furthermore, the level of energy density achievable in a single cell might be considerably greater than what’s possible in a battery consisting of many such cells. The energy density doesn’t translate directly from the cell to the battery because cells require packaging—the case, the battery management system, and the connections, and perhaps cooling systems. The weight must be kept in check, and for this reason our company is using advanced composite materials to develop light, strong, flameproof enclosures.

If the packaging is done right, the energy density of the battery can be held to 80 percent of that of the cells: A cell rated at 450 Wh/kg can be packaged at more than 360 Wh/kg in the final battery. We expect to do better by integrating the battery into the aircraft, for instance, by making the wing space do double duty as the battery housing. We expect that doing so will get the figure up to 90 percent.

To optimize battery performance without compromising safety we rely, first and foremost, on a battery management system (BMS), which is a combination of software and hardware that controls and protects the battery. It also includes algorithms for measuring the energy remaining in a battery and others for minimizing the energy wasted during charging.

Like lithium-ion cells, lithium-sulfur cells vary slightly from one another. These differences, as well as differences in the cells’ position in the battery pack, may cause some cells to consistently run hotter than others. Over time, those high temperatures slowly degrade performance, so it is important to minimize the power differences from cell to cell. This is usually achieved using a simple balancing solution, in which several resistors are connected in parallel with a cell, all controlled by software in the BMS.

Even when charging and discharging rates are kept within safe limits, any battery may still generate excessive heat. So, typically, a dedicated thermal-management system is necessary. An electric car can use liquid cooling, but in aviation, air cooling is much preferred because it adds less weight. Of course, the battery can be placed at a point where air is naturally moving across the surface of the airplane—perhaps the wing. If necessary, air can be shunted to the battery through ducts. At Oxis, we’re using computational modeling to optimize such cooling. For instance, when we introduced this technique in a project for a small fixed-wing aircraft, it allowed us to design an effective thermal-management system, without which the battery would reach its temperature limits before it was fully discharged.

As noted above, a battery pack is typically arranged with the cells both in parallel and in series. However, there’s more to the arrangement of cells. Of course, the battery is a mission-critical component of an e-plane, so you’ll want redundancy, for enhanced safety. You could, for instance, design the battery in two equal parts, so that if one half fails it can be disconnected, leaving the aircraft with at least enough energy to manage a controlled descent and landing.

Another software component within the BMS is the state-of-charge algorithm. Imagine having to drive a car whose fuel gauge had a measurement error equivalent to 25 percent of the tank’s capacity. You’d never let the indicator drop to 25 percent, just to make sure that the car wouldn’t sputter to a halt. Your practical range would be only three-quarters of the car’s actual range. To avoid such waste, Oxis has put a great emphasis on the development of state-of-charge algorithms.

In a lithium-ion battery you can estimate the charge by simply measuring the voltage, which falls as the energy level does. But it’s not so simple for a lithium-sulfur battery. Recall that in the lithium-sulfur battery, different polysulfides figure in the electrochemical process at different times during charge and discharge. The upshot is that voltage is not a good proxy for the state of charge and, to make things even more complicated, the voltage curve is asymmetrical for charge and for discharge. So the algorithms needed to keep track of the state of charge are much more sophisticated. We developed ours with Cranfield University, in England, using statistical techniques, among them the Kalman filter, as well as neural networks. We can estimate state of charge to an accuracy of a few percent, and we are working to do better still.

All these design choices involve trade-offs, which are different for different airplanes. We vary how we manage these trade-offs in order to tailor our battery designs for three distinct types of aircraft.

  • High-altitude pseudo satellites (HAPS) are aircraft that fly at around 15,000 to 20,000 meters. The hope is to be able to fly for months at a time; the current record is 26 days, set in 2018 by the Airbus Zephyr S. By day, these aircraft use solar panels to power the motors and charge the batteries; by night, they fly on battery power. Because the 24-hour charge-and-discharge period demands only a little power, you can design a light battery and thus allow for a large payload. The lightness also makes it easier for such an aircraft to fly far from the equator, where the night lasts longer.
  • Electric vertical take-off and landing (eVTOL) aircraft are being developed as flying taxis. Lilium, in Germany, and Uber Elevate, among others, already have such projects under way. Again, weight is critical, but here the batteries need not only be light but must also be powerful. Oxis has therefore developed two versions of its cell chemistry. The high-energy version is optimized in many aspects of the cell design to minimize weight, but it is limited to relatively low power; it is best suited to HAPS applications. The high-power version weighs more, although still significantly less than a lithium-ion battery of comparable performance; it is well suited for such applications as eVTOL.
  • Light fixed-wing aircraft: The increasing demand for pilots is coming up against the high cost of training them; an all-electric trainer aircraft would dramatically reduce the operation costs. A key factor is longer flight duration, which is enabled by the lighter battery. Bye Aerospace, in Colorado, is one company leading the way in such aircraft. Furthermore, other companies—such as EasyJet, partnered with Wright Electric—are planning all-electric commercial passenger jets for short-haul, 2-hour flights.

Three factors will determine whether lithium-sulfur batteries ultimately succeed or fail. First is the successful integration of the batteries into multiple aircraft types, to prove the principle. Second is the continued refinement of the cell chemistry. Third is the continued reduction in the unit cost. A plus here is that sulfur is about as cheap as materials get, so there’s reason to hope that with volume manufacturing, the unit cost will fall below that of the lithium-ion design, as would be required for commercial success.

Oxis has already produced tens of thousands of cells, and it is currently scaling up two new projects. Right now, it is establishing a manufacturing plant for the production of both the electrolyte and the cathode active material in Port Talbot, Wales. Later, the actual mass production of lithium-sulfur cells will begin on a site that belongs to Mercedes-Benz Brazil, in Minas Gerais, Brazil.

This state-of-the-art plant should be commissioned and operating by 2023. If the economies of scale prove out, and if the demand for electric aircraft rises as we expect, then lithium-sulfur batteries could begin to supplant lithium-ion batteries in this field. And what works in the air ought to work on the ground, as well.

This article appears in the August 2020 print issue as “Ultralight Batteries for Electric Airplanes.”

About the Author

Mark Crittenden is head of battery development and integration at Oxis Energy, in Oxfordshire, U.K.

Link: https://spectrum.ieee.org/aerospace/aviation/with-ultralight-lithiumsulfur-batteries-electric-airplanes-could-finally-take-off

Ingenuity Mars helicopter recharges its batteries in flight

NASA’s Ingenuity Mars Helicopter received a checkout and recharge of its power system on Friday, Aug. 7, one week into its near seven-month journey to Mars with the Perseverance rover. This marks the first time the helicopter has been powered up and its batteries have been charged in the space environment.

During the eight-hour operation, the performance of the rotorcraft’s six lithium-ion batteries was analyzed as the team brought their charge level up to 35%. The project has determined a low charge state is optimal for battery health during the cruise to Mars.

“This was a big milestone, as it was our first opportunity to turn on Ingenuity and give its electronics a ‘test drive’ since we launched on July 30,” said Tim Canham, the operations lead for Mars Helicopter at NASA’s Jet Propulsion Laboratory in Southern California. “Since everything went by the book, we’ll perform the same activity about every two weeks to maintain an acceptable state of charge.”

The 4-pound (2-kilogram) helicopter-a combination of specially designed components and off-the-shelf parts-is currently stowed on Perseverance’s belly and receives its charge from the rover’s power supply. Once Ingenuity is deployed on Mars’ surface after Perseverance touches down, its batteries will be charged solely by the helicopter’s own solar panel. If Ingenuity survives the cold Martian nights during its preflight checkout, the team will proceed with testing.

Ingenuity Mars helicopter recharges its batteries in flight
The Ingenuity Mars Helicopter can be seen between the left and center wheels of the Mars 2020 Perseverance rover. The image was taken in the vacuum chamber at JPL on Oct. 1, 2019. Credit: NASA/JPL-Caltech

“This charge activity shows we have survived launch and that so far we can handle the harsh environment of interplanetary space,” said MiMi Aung, the Ingenuity Mars Helicopter project manager at JPL. “We have a lot more firsts to go before we can attempt the first experimental flight test on another planet, but right now we are all feeling very good about the future.”

The small craft will have a 30-Martian-day (31-Earth-day) experimental flight-test window. If it succeeds, Ingenuity will prove that powered, controlled flight by an aircraft can be achieved at Mars, enabling future Mars missions to potentially add an aerial dimension to their explorations with second-generation rotorcraft.

Link: https://phys.org/news/2020-08-ingenuity-mars-helicopter-recharges-batteries.html

Aerospace Technology Institute Launches One-Year Study of Zero Emission Commercial Aircraft

The Aerospace Technology Institute will bring more than one hundred people onboard for a year-long feasibility and design study of zero-emissions commercial aircraft. (ATI)

The UK’s Aerospace Technology Institute (ATI) will lead a one-year project to study design challenges and potential for a zero-emission commercial aircraft, a part of the Jet Zero Council launched by Prime Minister Boris Johnson in July to tackle climate change and establish national leadership on carbon neutral long-haul air travel.

Executives from ATI, speaking during a webinar about the project, described it as an effort to holistically explore the potential to realize a zero-carbon emission commercial aircraft, with 80 seats or more, by the end of the decade, with potential for a follow-on phase to include a major demonstrator project.

“The prime minister spoke about his ambition to achieve some bold carbon reduction … he’s completely bought into it, and they see FlyZero as forming a key component of that mission,” said Gary Elliot, CEO of ATI. “This is a transformative project that has the potential to have a follow-on moonshot phase if we get it right.”

Working with partners across the UK’s aerospace sector, ATI intends to bring up to 110 people into its organization as “secondees,” where they will work for the FlyZero project full-time with salaries and expenses paid by ATI. Most will be engineers, but smaller teams will also be stood up to examine markets, commercial viability, production, lifecycle and supply chain issues.

The project will begin with an initial study phase, collecting and structuring known information on air vehicle concepts, energy sources and conversion, and future air transport markets, according to Simon Weeks, ATI’s chief technology officer.

“Then, we’ll down-select ideas that we think are most appropriate and carry out a concept trade study, starting to pull those views of aircraft and aircraft systems … how they might perform, how sustainable they might be, what operational issues there might be, and whether we have a view at that stage on what the commercial and operational viability might be,” Weeks said during the broadcast.

In the final project phase, one or more designs will be chosen through a further down-select for a preliminary design phase, where Weeks said the intent is to develop concepts into much more fleshed-out models and understand their performance and technological challenges in greater detail.

“We’re looking to see what is the most likely commercial zero net carbon aircraft in the 2030s and what addition does the UK need to do to be ready for that? What demonstrator projects do we need to do downstream from this study?” Weeks said. “[This project will] take one or more designs to a reasonable level of detail, and once you get into a level of detail, only then you start to tease out some of the key technical issues.”

In addition to potential follow-on projects, the results of the one-year FlyZero program will be disseminated back into the UK aerospace community to further encourage progress toward zero emissions aircraft.

ATI officials said the initial FlyZero project will only include UK partners, as part of its goal is to create a UK consortium and bolster national competitiveness in pursuit of zero-carbon aviation solutions, but later follow-on projects may look to include international collaboration.

“If you take the [Intergovernmental Panel on Climate Change] scenarios in order to achieve 1.5 or even 2 degrees [Celsius] warming by the end of the century, and overlay the trajectory for aviation in terms of CO2 output, the sector is on track by 2050 to become a major, if not the major, contributor to CO2 emissions,” said James McMicking, chief strategy officer for ATI.

“Today, it’s only two percent, but other sectors will find it easier than aerospace to reduce their carbon emissions.”

Link: https://www.aviationtoday.com/2020/08/13/aerospace-technology-institute-launches-one-year-study-zero-emission-commercial-aircraft/

Rolls-Royce to carry out extra inspections on some Trent XWB engines

LONDON (Reuters) – Britain’s Rolls-Royce will carry out extra inspections on some of its Trent XWB engines which power the Airbus A350 airliner.

Rolls-Royce said on Tuesday that the issue would not cause significant customer disruption or material cost, as it affected a small number of XWBs of a certain age.

The Trent XWB-84 engine is set to be subject to an Airworthiness Directive from regulator EASA, Rolls said, because of wear on a small number of Intermediate Pressure Compressor blades found on a minority of engines which have been in service for four to five years.

Rolls-Royce finds cracks in small number of Trent XWB engines
FILE PHOTO: A man looks at Rolls-Royce’s Trent Engine displayed at the Singapore Airshow

None of those engines have experienced abnormal in-flight operation, it said, adding that it would carry out inspections on all Trent XWB-84s of a similar service life as a precaution. There are just over 100 of them.

“Given the limited scale of additional work which we anticipate will be required at existing shop visits to address this wear, together with the availability of replacement parts and spare engines, we do not expect this issue to create significant customer disruption or material annual cost,” Rolls said in a statement.

Problems with its Trent 1000 engine which powers the Boeing 787 airliner are expected to cost Rolls-Royce 2.4 billion pounds ($3.1 billion) to fix over a 2017-2023 period.

Rolls recently said it was considering strengthening its finances to help it withstand the pandemic.

It burned through 3 billion pounds in the first half of the year as planes stopped flying, cutting the revenue it receives from flying hours.

Link: https://www.yahoo.com/news/rolls-royce-carry-extra-inspections-090622638.html

MagniX Sees Regional Operators as Electric Aviation Pioneers

MagniX eCaravan
Electric propulsion specialist MagniX says it is close to signing up a launch customer and STC partner for its eCaravan re-engining program. (Photo: MagniX)

MagniX has reported further progress with flight testing of its proposed electric versions of the Cessna Caravan and DHC-2 Beaver utility aircraft. The company told AIN it is on track to achieve FAA Part 33 certification for the battery-powered propulsion systems by late 2021 or early 2022 and that supplemental type certificates (STCs) could be in place for both programs in time for aircraft to enter commercial service by the end of 2022. At the same time, MagniX is continuing to work with its sister company Eviation Aircraft to provide the electric motors for the new Alice fixed-wing aircraft.

Following a fire during ground testing and delays due to Covid-19 pandemic restrictions, the first prototype of the aircraft is now expected to make an initial flight in early 2021, according to MagniX CEO Roei Ganzarski. U.S.-based MagniX is focusing its efforts on providing electric propulsion for new and existing fixed-wing aircraft that could fly sectors of between 50 and 1,000 miles.

For now, Ganzarski explained, it is not seeking to provide propulsion for new eVTOL aircraft because it doesn’t see the strong commercial case for scaling down its Magni250 and -500 motors, which currently offer continuous power of 280 and 560 kW, respectively. Many eVTOL aircraft designs require multiple electric motors, each with power of around 40 or 50 kW. On May 28, MagniX and its partner AeroTec achieved a first flight with the eCaravan prototype, which is a modified version of the Cessna 208B Grand Caravan powered by the Magni500.

Flight testing has continued at Grant County International Airport in Moses Lake, Washington, and Ganzarski said that it has since become the first electric aircraft of its type to fly at an altitude of 8,000 feet. This has allowed engineers to evaluate how the electrical components perform in an unpressurized environment. Each flight test has lasted a minimum of 30 minutes, with distances flown gradually being increased by unspecified amounts. The development team has been experimenting with various rates of climb and descent and also with varying power levels.

Link: https://www.ainonline.com/aviation-news/air-transport/2020-08-10/magnix-sees-regional-operators-electric-aviation-pioneers