6 ms·

I think this airplane is pressurized, flies very high and has a big turbocharger. And it has a diesel engine, so the MPG means a different thing - diesel is den

I think this airplane is pressurized, flies very high and has a big turbocharger. And it has a diesel engine, so the MPG means a different thing - diesel is denser. It's optimized differently to the experimentals, and it's more useful commercially. Flying high avoids a lot of weather issues. You don't have to cancel flights because of weather. The drag from the streamlined shape is very low. It's just a textbook minimum drag shape. The cruise speed advertised does seem high still.

scarier 6y ago
All of that helps, but a pilot flying an unpressurized experimental can still get up to 17.5k' VFR on oxygen. Assuming the Celera cruises around FL250, you're talking the difference between ~300KTAS and ~350 KTAS at 200 KIAS. I'd be shocked if they cruise much above FL300, regardless of how high their service ceiling proves to be--for anything other than a really long-distance flight, they'll spend too much time climbing to altitude for it to be worth the effort.
- Robotbeat 6y ago
  This is optimized for really long distance flight, thousands of miles. That’s the whole point. Cruise height of 30,000ft, I think. Why would you be shocked by flying at heights comparable to typical jet aircraft flying similar distances?
  - scarier 6y ago
    I wouldn't be surprised by a long-range cruise altitude around FL300, but if it was FL450 I'd be extremely surprised. If the plane achieves the advertised 20mpg on a hypothetical 4500-mile flight at FL500, but only makes a small fraction of that on a more realistic 400-mile regional hop at FL210, it's not really a practical success. (Aside: the advertised range seems like drastic overkill for something designed to offer a cheap alternative to private jets--it's difficult to overstate how much it sucks being cooped up in a tiny plane for over 11 hours, even if you have the luxury of rich leather seats, can stand up in the cabin, and don't have to pee into plastic bags. Even if a family wants to charter a private jet from LA to the Bahamas for a long weekend, it'd be miserable trying to one-leg it.)
    - Robotbeat 6y ago
      The whole business case for this vehicle is that it enables extremely low cost granular travel between distant city pairs. The short regional hop is not its target market. It’s designed to be competitive with commercial air travel.
      - scarier 6y ago
        That's fair--400 miles is on the shorter end of the spectrum. Still, "low cost" is relative to a chartered private jet--which, emphatically, is not a service that people purchase because it's the most economical option--rather than a commercial airliner (although, if true, the SFC per passenger of the Celera would be in the same ballpark as modern commercial airliners, which is very impressive). The average domestic flight is under 1000 statute miles (https://www.bts.gov/content/average-length-haul-domestic-freight-and-passenger-modes-miles https://www.bts.gov/content/average-length-haul-domestic-fre...), so this plane needs to offer compelling efficiency gains at ~500-1500 mile ranges in order to compete with existing services, unless they're strictly planning to fill the niche of one-leg, long-range flights that existing private jets don't have the legs for.
        Robotbeat 6y ago
        No, they intend to compete with like commercial travel, maybe business class at first, in price per seat per trip to charter an aircraft like this. $300/hour charter price with 6 seats for a 5 hour trip (2000 miles) is about $250 per seat each way. This is pretty competitive.
        scarier 6y ago
        $328/hr is the advertised operating cost of the aircraft (fuel and maintenance), not anything close to what a charter would actually charge. Commercial airline operating costs, including crew salary and overhead, are roughly an order of magnitude more (~$3000/hour is a rough, somewhat conservative, number for something like a B737, including fuel, crew, maintenance, and aircraft depreciation/rental costs). The airline is paying under $20 per passenger-hour for all expenses, while a charter service operating with volunteer pilots, free airplanes, and no other costs would break even at ~$55 per passenger-hour (assuming the $328/hr estimate is accurate, which is still very much an open question for an aircraft that's still undergoing initial flight testing and may never be produced in significant volume). Even the best-case scenario doesn't strike me as particularly competitive.
- thunderbird120 6y ago
  Their patent application implies that it is optimized for cruising at 50,000 feet. [1]https://patentimages.storage.googleapis.com/3b/f3/9a/928c8625bcc4aa/US9308989.pdf https://patentimages.storage.googleapis.com/3b/f3/9a/928c862...
  - scarier 6y ago
    I mean, their patent application also claims an SFC of ~30-42 MPG at 460-510 mph... A design cruising altitude of FL500 implies that they're seeing nearly all of their efficiency improvements due to the thin air at altitude (flying around 200 mph indicated, which isn't totally unreasonable for 20 mpg in a small-ish piston-prop), but I doubt they have the climb rate to actually reach that altitude in anything short of a transcontinental flight. I like to think they crunched the performance numbers once or twice, but if they're off by the same amount they were with their initial SFC calculations, there's no way they'll reach an acceptable cruising altitude during an average flight.
aeternum 6y ago
While the shape might work well for drag, looks matter, especially with private aviation. This thing just doesn't look very sleek or impressive. Cost to repair and insurance is also a very significant part of the cost, so if this is difficult to land or costly to repair, it won't be very popular.
- tomcam 6y ago
  If it comes even close to the claimed efficiency it could look like a 1961 Skoda and nobody would care
Meandering 6y ago
The design of the body reduces drag and acts as a mechanism for lift. https://en.wikipedia.org/wiki/Lifting_body https://en.wikipedia.org/wiki/Lifting_body
- mannykannot 6y ago
  A lifting body sounds like you are getting something for free, but it does not really work out that way. In terms of efficiency, what matters is the overall lift/drag ratio, and so the first issue is whether shaping the fuselage for lift can be done without creating so much extra drag as to reduce the overall lift/drag ratio. In this regard, note that fuselages are long and narrow, while efficient wings are wide in span and short in chord. A second factor is the effect of a lifting body on stability, and the cost of compensating for it. Even in the case of nominally non-lifting fuselages, they tend to produce lift at high angles of attack, and that tends to be destabilizing, producing an increasing pitch-up moment as the angle of attack increases (ordinary straight wings do too, but the effect is proportionately less, as the wing chord is considerably less than the fuselage length.) This has to be corrected with measures (typically a larger stablizer) that also create drag. Having a fuselage designed to produce lift exacerbates this problem, commensurably with the amount of lift being generated. Modern sailplane design is a case study in the persuit of aerodynamic efficiency, at least at low speeds, and lifting bodies have not proved to be useful. The fact is that, once you are flying, you do not need more lift; what you want is less drag.
refurb 6y ago
You don't have to cancel flights because of weather. I don't think many flights today are cancelled because of weather on the route there, it's the weather over each airport, which would still impact this aircraft.
- Gravityloss 6y ago
  Small unpressurized planes do cancel a lot of flights since they fly lower and are affected by weather. Many other six seat planes are like that.
  - refurb 6y ago
    Ahhh.. of course. Good point.

scarier 6y ago

All of that helps, but a pilot flying an unpressurized experimental can still get up to 17.5k' VFR on oxygen. Assuming the Celera cruises around FL250, you're talking the difference between ~300KTAS and ~350 KTAS at 200 KIAS. I'd be shocked if they cruise much above FL300, regardless of how high their service ceiling proves to be--for anything other than a really long-distance flight, they'll spend too much time climbing to altitude for it to be worth the effort.

Robotbeat 6y ago
This is optimized for really long distance flight, thousands of miles. That’s the whole point. Cruise height of 30,000ft, I think. Why would you be shocked by flying at heights comparable to typical jet aircraft flying similar distances?
- scarier 6y ago
  I wouldn't be surprised by a long-range cruise altitude around FL300, but if it was FL450 I'd be extremely surprised. If the plane achieves the advertised 20mpg on a hypothetical 4500-mile flight at FL500, but only makes a small fraction of that on a more realistic 400-mile regional hop at FL210, it's not really a practical success. (Aside: the advertised range seems like drastic overkill for something designed to offer a cheap alternative to private jets--it's difficult to overstate how much it sucks being cooped up in a tiny plane for over 11 hours, even if you have the luxury of rich leather seats, can stand up in the cabin, and don't have to pee into plastic bags. Even if a family wants to charter a private jet from LA to the Bahamas for a long weekend, it'd be miserable trying to one-leg it.)
  - Robotbeat 6y ago
    The whole business case for this vehicle is that it enables extremely low cost granular travel between distant city pairs. The short regional hop is not its target market. It’s designed to be competitive with commercial air travel.
    - scarier 6y ago
      That's fair--400 miles is on the shorter end of the spectrum. Still, "low cost" is relative to a chartered private jet--which, emphatically, is not a service that people purchase because it's the most economical option--rather than a commercial airliner (although, if true, the SFC per passenger of the Celera would be in the same ballpark as modern commercial airliners, which is very impressive). The average domestic flight is under 1000 statute miles (https://www.bts.gov/content/average-length-haul-domestic-freight-and-passenger-modes-miles https://www.bts.gov/content/average-length-haul-domestic-fre...), so this plane needs to offer compelling efficiency gains at ~500-1500 mile ranges in order to compete with existing services, unless they're strictly planning to fill the niche of one-leg, long-range flights that existing private jets don't have the legs for.
      - Robotbeat 6y ago
        No, they intend to compete with like commercial travel, maybe business class at first, in price per seat per trip to charter an aircraft like this. $300/hour charter price with 6 seats for a 5 hour trip (2000 miles) is about $250 per seat each way. This is pretty competitive.
        scarier 6y ago
        $328/hr is the advertised operating cost of the aircraft (fuel and maintenance), not anything close to what a charter would actually charge. Commercial airline operating costs, including crew salary and overhead, are roughly an order of magnitude more (~$3000/hour is a rough, somewhat conservative, number for something like a B737, including fuel, crew, maintenance, and aircraft depreciation/rental costs). The airline is paying under $20 per passenger-hour for all expenses, while a charter service operating with volunteer pilots, free airplanes, and no other costs would break even at ~$55 per passenger-hour (assuming the $328/hr estimate is accurate, which is still very much an open question for an aircraft that's still undergoing initial flight testing and may never be produced in significant volume). Even the best-case scenario doesn't strike me as particularly competitive.
thunderbird120 6y ago
Their patent application implies that it is optimized for cruising at 50,000 feet. [1]https://patentimages.storage.googleapis.com/3b/f3/9a/928c8625bcc4aa/US9308989.pdf https://patentimages.storage.googleapis.com/3b/f3/9a/928c862...
- scarier 6y ago
  I mean, their patent application also claims an SFC of ~30-42 MPG at 460-510 mph... A design cruising altitude of FL500 implies that they're seeing nearly all of their efficiency improvements due to the thin air at altitude (flying around 200 mph indicated, which isn't totally unreasonable for 20 mpg in a small-ish piston-prop), but I doubt they have the climb rate to actually reach that altitude in anything short of a transcontinental flight. I like to think they crunched the performance numbers once or twice, but if they're off by the same amount they were with their initial SFC calculations, there's no way they'll reach an acceptable cruising altitude during an average flight.

aeternum 6y ago

While the shape might work well for drag, looks matter, especially with private aviation. This thing just doesn't look very sleek or impressive. Cost to repair and insurance is also a very significant part of the cost, so if this is difficult to land or costly to repair, it won't be very popular.

tomcam 6y ago
If it comes even close to the claimed efficiency it could look like a 1961 Skoda and nobody would care

Meandering 6y ago

The design of the body reduces drag and acts as a mechanism for lift. https://en.wikipedia.org/wiki/Lifting_body https://en.wikipedia.org/wiki/Lifting_body

mannykannot 6y ago
A lifting body sounds like you are getting something for free, but it does not really work out that way. In terms of efficiency, what matters is the overall lift/drag ratio, and so the first issue is whether shaping the fuselage for lift can be done without creating so much extra drag as to reduce the overall lift/drag ratio. In this regard, note that fuselages are long and narrow, while efficient wings are wide in span and short in chord. A second factor is the effect of a lifting body on stability, and the cost of compensating for it. Even in the case of nominally non-lifting fuselages, they tend to produce lift at high angles of attack, and that tends to be destabilizing, producing an increasing pitch-up moment as the angle of attack increases (ordinary straight wings do too, but the effect is proportionately less, as the wing chord is considerably less than the fuselage length.) This has to be corrected with measures (typically a larger stablizer) that also create drag. Having a fuselage designed to produce lift exacerbates this problem, commensurably with the amount of lift being generated. Modern sailplane design is a case study in the persuit of aerodynamic efficiency, at least at low speeds, and lifting bodies have not proved to be useful. The fact is that, once you are flying, you do not need more lift; what you want is less drag.

refurb 6y ago

You don't have to cancel flights because of weather. I don't think many flights today are cancelled because of weather on the route there, it's the weather over each airport, which would still impact this aircraft.

Gravityloss 6y ago
Small unpressurized planes do cancel a lot of flights since they fly lower and are affected by weather. Many other six seat planes are like that.
- refurb 6y ago
  Ahhh.. of course. Good point.