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Torenbeek (engineer famous for his book on aircraft design) indicates 0.014-0.020. However I've been estimating values for typical planes like the B737/A319 and I'm getting values of 0.026-0.027. I'm interested in planes of approximately this size. This makes me think that Torenbeek may be outdated.

Does anyone know typical values? CD0 being the parasitic drag coefficient of the entire aircraft.

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    $\begingroup$ Torenbeek is right, the high Reynolds numbers of large and fast transports make such low values possible. It would be interesting to see the basis of your results; without those I cannot really give a better answer. $\endgroup$
    – Peter Kämpf
    Aug 22, 2021 at 1:00

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The $C_{D0}$ table in Torenbeek's book. The version I have was published in 1982, at the time the B737-200 had been in operation for 11 years. Plus the following high-subsonic jet aircraft:

  • Airbus 300 since 1974
  • B-707 since 1958, including the stretched B707-320 operational since 1959
  • B-727 since 1964, including the 727-200 operational since 1967
  • DC-8 since 1959, including stretched versions through the DC-8-63
  • DC-9 since 1965, including stretched versions through the DC-9-50
  • F28 since 1967, including stretched versions through to 1973.
  • Many others, such as the B747, Ilyushin 62, L-1011, Caravelle, Comet, BAC 111 etc.

The $C_{D0}$ values in the table were based on all high subsonic jets in operation at the time. Note that the B737 shares the fuselage diameter with the B727 and B707 - length of the current B737Max at 43.8m is still a bit shorter than the B707 @ 46.6m, so is the wing span. The 4 narrow cross section engines of the 707, versus the dual engines with much wider cross sections of the Max.

Nothing in the configuration changes since 1982 strikes me as a probable cause of an increase in $C_{D0}$ to that of a twin engine piston aircraft.

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    $\begingroup$ As additional info, another source from 2018 includes the newer jets; the CD0(clean) is from 0.012 (A380) to 0.033 (777-300ER). $\endgroup$
    – user14897
    Aug 22, 2021 at 11:11
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    $\begingroup$ @ymb1 Thx for the doc, interesting info. They use statistical methods to estimate a matrix of parameters, the results have quite an uncertainty spread, not in the least because they don’t know the actual mass. At the time of writing of Torenbeek the manufacturer windtunnel data was much more freely available. $\endgroup$
    – Koyovis
    Aug 23, 2021 at 23:12

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