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It seems to require a pretty seriously long runway to take off. On a warm day, we’re talking international airport length runway. While pistons are cheaper tha
by karlkatzke 6y ago
It seems to require a pretty seriously long runway to take off. On a warm day, we’re talking international airport length runway.
While pistons are cheaper than turbines, that’s because almost all of the approved pistons on the market use 1940s or earlier technology. They are very, very, very simple machines. They are still extremely expensive.
This engine is very complicated, even for an automotive engine. It’s got some revolutionary attributes, but it also has a bunch of single points of failure that would mean traveling in this airplane over long distances and large bodies of water isn’t a good idea.
I’m frankly not holding my breath. While they’ve got a bunch of buzz around them, that and a working example are like 1/10 the battle in the aircraft industry. Wish them the best for trying to advance the art but many more established and better funded folks have tried and gone bankrupt before them.
- flak48 6y agoSince this plane is intended to compete with other business jets, don't owners of typical business jets mostly travel to (international) airports with long enough runways anyway?
- DuskStar 6y agoHalf the point of a business jet is flying to more convenient (but smaller) airports.
- _uy6i 6y ago3,300 feet in not a long runway - it means you can access ~80% of the ~5,000 runways in the US. On the the other hand A 777 needs 8,000-10,000 feet meaning it can only access <10% of US runways.... https://www.cia.gov/library/publications/the-world-factbook/fields/380.html https://www.cia.gov/library/publications/the-world-factbook/... https://en.wikipedia.org/wiki/Boeing_777#777-200LR https://en.wikipedia.org/wiki/Boeing_777#777-200LR
- karlkatzke 6y ago3300 feet in balanced density conditions. You’d better not bet on 3300 feet in Phoenix during the day time most of the year. Or Denver for that matter.
- dmix 6y agoSorry for the amateur question, but why does it take longer to take off in hot places? Doesn’t heat generate lift, like in gliders crossing hilly terrain? Or is it the heat offsetting with the cooler ground that helps, so you’d need a greater amount in hot places?
- rolph 6y agohot air rises but its less dense thats why it rises, so it has less lifting capacity thermal updrafts are different they are a larger scale phenomenon
- unoti 6y ago> why does it take longer to take off in hot places? When the air is cold the air is more dense. This has an impact both on how much lift is generated per amount of speed over the wings, and also impacts how much power the engine/carburetor are able to generate.
- generatorguy 6y agoWhen it is hot out Air is less dense so the wings don’t generate as much lift. I believe engines make less power when the air in is hotter too as there is less delta T. Something something Carnot cycle
- KMag 6y agoThe Carnot efficiency does drop as T_c increases, so all else being equal, for the same amount of fuel being burned, you'll get less energy. However, more importantly, at higher temperatures, a given volume of air at the same pressure contains less oxygen. All else being equal, at higher ambient temperatures, you're burning less fuel. For a turbocharged engine, you could increase boost to counter-act the reduced density, but that increases both mechanical and thermal stresses within the engine. Anyway, I think the reduction of oxygen density is the primary driver for reduction in power as ambient temperatures rise.
- scarier 6y agoAlso, a 3300' take-off roll doesn't mean you need a 3300' runway to operate--if you lose the engine just before rotation speed, you might need a few thousand more feet to stop the aircraft.
- sitkack 6y agoI would bet they end up putting liquid cooled electric motors in the wheels to shorten the take off distance to 1500 feet.
- joshyeager 6y agoThe article says its typical takeoff run is 3300 feet, which is about half what a 737 needs. I don’t know a lot about airplanes, but that seems like a pretty short runway length requirement. What am I missing?
- 9nGQluzmnq3M 6y agoThe 737 is a far larger plane. The Celera has capacity for 6 passengers, while you can cram over 200 into a 737. For a better comparison, the world's most popular aircraft, the four-seater Cessna 172, needs under 500 feet to take off in optimal conditions, although you might need 1500 feet if fully loaded and high up. http://www.dmjwilliams.co.uk/gbsep_performance.htm http://www.dmjwilliams.co.uk/gbsep_performance.htm (in meters, not feet) However, the Cessna Citation M2 business jet, which targets a similar market as the Celera, also requires ~3000 ft (again depending on weight, altitude, conditions). So not seeing a huge difference here. https://prijet.com/performance/Cessna%20Citation%20M2 https://prijet.com/performance/Cessna%20Citation%20M2
- whatch 6y ago3300 feet = 1 km (for people outside US)
- AceyMan 6y agoTakeoff run length is for the marketing sheets. What counts is the ASD — accelerate-stop distance, see also, balanced field length. Citation, https://en.wikipedia.org/wiki/Balanced_field_takeoff?wprov=sfla1 https://en.wikipedia.org/wiki/Balanced_field_takeoff?wprov=s... /Acey
- sowbug 6y agoA typical small airport might have a 2,500-foot runway, and you never want to come anywhere close to using all that up. It's often desirable to use small airports that are closer to your origin and destination, which could save several hours of travel time before takeoff and after landing. Usually there's also less air traffic to contend with, no landing fees, and cheaper aircraft parking.