4 ms·

But also inversely affects the weight of the aircraft, negatively affecting the fuel economy.

Retric 7y ago
While true, parasitic drag is generally a significantly larger factor at airliner speeds. Airbus A320 during Cruise: “The 7,900lbf of drag is composed of 4,700lbf of Parasitic drag or drag independent of lift and 3,200lbf of Induced drag or drag caused by lift.” https://leehamnews.com/2018/03/09/bjorns-corner-aircraft-drag-reduction-part-20/ https://leehamnews.com/2018/03/09/bjorns-corner-aircraft-dra... On top of this slightly increasing passengers, their luggage, and a few extra seats has fairly minimal impact on aircraft weight. The aircraft’s maximum fuel/range is impacted, but that’s rarely an issue.
- cameldrv 7y ago
  Yes, but parasite drag is indirectly affected by weight. A lot of the parasite drag comes from the wings and engines, and they scale up with weight, as long as you want to keep the same takeoff/landing distances.
  - Retric 7y ago
    This is a comparison of the impact of seating arrangements for otherwise identical aircraft. The maximum takeoff weight stays the same, the difference is how much fuel they can add before they hit it. Which is why ultra long haul flights tend to have more leg room. This can be as much as 5 inches for the same airlines.
    - cameldrv 7y ago
      Fair enough, but my point was that for a given set of capabilities (landing speed/distance, range), if you want to add more payload, you need more wing. The additional payload costs you drag from induced drag, but it also costs you parasite drag from the bigger wing you need to generate that lift at landing speed. You even see this with some stretched versions of airliners, they enlarge the wings or make changes to the high lift devices.
usrusr 7y ago
It improves the payload fraction of total mass. That is generally better. But you might have to factor the expected total mass into the design. If you want to transport the payload mass of a 747 in lead bars, the smallest plane that can fit the volume will certainly not work. But a plane designed for that lead load would be far more efficient than a 747 (or modern equivalent) that is flying almost empty by volume.

While true, parasitic drag is generally a significantly larger factor at airliner speeds. Airbus A320 during Cruise: “The 7,900lbf of drag is composed of 4,700lbf of Parasitic drag or drag independent of lift and 3,200lbf of Induced drag or drag caused by lift.” https://leehamnews.com/2018/03/09/bjorns-corner-aircraft-drag-reduction-part-20/ https://leehamnews.com/2018/03/09/bjorns-corner-aircraft-dra... On top of this slightly increasing passengers, their luggage, and a few extra seats has fairly minimal impact on aircraft weight. The aircraft’s maximum fuel/range is impacted, but that’s rarely an issue.

cameldrv 7y ago
Yes, but parasite drag is indirectly affected by weight. A lot of the parasite drag comes from the wings and engines, and they scale up with weight, as long as you want to keep the same takeoff/landing distances.
- Retric 7y ago
  This is a comparison of the impact of seating arrangements for otherwise identical aircraft. The maximum takeoff weight stays the same, the difference is how much fuel they can add before they hit it. Which is why ultra long haul flights tend to have more leg room. This can be as much as 5 inches for the same airlines.
  - cameldrv 7y ago
    Fair enough, but my point was that for a given set of capabilities (landing speed/distance, range), if you want to add more payload, you need more wing. The additional payload costs you drag from induced drag, but it also costs you parasite drag from the bigger wing you need to generate that lift at landing speed. You even see this with some stretched versions of airliners, they enlarge the wings or make changes to the high lift devices.

usrusr 7y ago

It improves the payload fraction of total mass. That is generally better. But you might have to factor the expected total mass into the design. If you want to transport the payload mass of a 747 in lead bars, the smallest plane that can fit the volume will certainly not work. But a plane designed for that lead load would be far more efficient than a 747 (or modern equivalent) that is flying almost empty by volume.