Bjorn’s Corner: Aircraft drag reduction, Part 21

By Bjorn Fehrm

March 16, 2018, ©. Leeham News: In the last Corner, we looked at the drag of an airliner during cruise. We could see the thrust required to counter the drag in the thin air of 37,000 feet was low, about 4,000lbf per engine.

Now we continue with the drag created by the aircraft during descent and landing.

Figure 1. Drag of an aircraft at different airspeeds. Source: Leeham Co.

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Bjorn’s Corner: Aircraft drag reduction, Part 20

By Bjorn Fehrm

March 9, 2018, ©. Leeham Co: In the last Corner, we started to go through a typical mission for an airliner and study which drag types are important when and why.

We went through the take-off and climb phases, now we continue with the cruise phase.

Figure 1. An aircraft’s drag profile as airspeed varies. Source: Leeham Co.

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Bjorn’s Corner: Aircraft drag reduction, Part 19

February 23, 2018, ©. Leeham Co: In the last Corner we wrapped up the discussion on different drag types by discussing some less dominant drags.

To finish the series we will go through a typical mission for an airliner and study which drag is important when and why.

Figure 1. An aircraft’s drag profile as airspeed varies. The main part of Parasitic drag is air friction drag Source: Leeham Co.

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Bjorn’s Corner: Aircraft drag reduction, Part 18

By Bjorn Fehrm

February 23, 2018, ©. Leeham Co: In the last Corner we discussed transonic flow and drag. Now it’s time to finish the drag type discussion by adding some less dominant but still important drag types.

Knowing their origin will help us understand why aircraft are made like they are.

Figure 1. Low-pressure (green) shows areas with high flow speeds for the 787 during cruise. Source: Boeing and Leeham Co.

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Bjorn’s Corner: Aircraft drag reduction, Part 17

By Bjorn Fehrm

February 16, 2018, ©. Leeham Co: In the last Corner, we discussed supersonic flow and drag. Now it’s time to talk about the drag created by transonic flow on an aircraft.

Figure 1. Pressure distribution of 787 during cruise. Source: Boeing and Leeham Co.

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Bjorn’s Corner: Aircraft drag reduction, Part 16

By Bjorn Fehrm

February 9, 2018, ©. Leeham Co: In the last Corner, we discussed some further aspects of supersonic flow. Now it’s time to talk about the drag created by supersonic flow on an aircraft.

We will start with the full supersonic case this week, followed by the transonic case next week.

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Bjorn’s Corner: Aircraft drag reduction, Part 15

By Bjorn Fehrm

February 2, 2018, ©. Leeham Co: In the last Corner, we discussed the basics of supersonic flow, to prepare for a supersonic and transonic drag discussion.

We will continue the supersonic aerodynamics discussion, however, as there are some further areas needing an explanation before we move on.

Figure 1. The first supersonic airliner, the Concorde. Source: Google images.

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Bjorn’s Corner: Aircraft drag reduction, Part 14

By Bjorn Fehrm

January 26, 2018, ©. Leeham Co: In the last Corner, we discussed Induced drag after having covered Friction drag and Form drag. These are the main drag components of a subsonic aircraft.

As the aircraft flies over Mach 0.5, an additional drag is added, this time based on the air’s compressibility, transonic or supersonic drag.

Figure 1. The first supersonic airliner, the Concorde. Source: Google images.

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Bjorn’s Corner: Aircraft drag reduction, Part 13

By Bjorn Fehrm

January 19, 2018, ©. Leeham Co: In the last Corner, we described how the boundary layer theory lead to the understanding of Friction drag for aircraft. The mechanisms behind Induced drag was understood about the same time.

Once again Prandtl was involved, but it was an English person who first postulated the physical root of induced drag, Fredrick Lanchester.

Figure 1. Focke-Wulf Condor, a high aspect ratio aircraft from the 1930s. Source: Wikipedia.

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Bjorn’s Corner: Aircraft drag reduction, Part 12

By Bjorn Fehrm

January 12, 2018, ©. Leeham Co: In the last Corner, we described how the theory for the boundary layer was proposed by Ludwig Prandtl, and how this led to an understanding of the source of Friction drag for an aircraft.

We will now continue with describing how the role of Friction drag was researched and how aircraft designers learned how to reduce it.

Figure 1. Sopwith Camel fighter of the WW 1. Source: Google images.

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