In these notes, the authors state that:

On the Concorde, a one count drag increase (∆CD = .0001) requires two passengers, out of the 90 ∼ 100 passenger capacity, be taken off the North Atlantic run.

and refer to this article (paywalled). I've seen other statements that an increase of one drag count is equivalent to 5-10 passengers, but do not recall the source.

Do you know of any other references that list the equivalence between drag count increases with reduced numbers of passengers?

  • $\begingroup$ Your question is not completely clear to me. You want an equation that compute the relation between drag coefficient and number of passengers? $\endgroup$ Commented Dec 21, 2016 at 9:44
  • $\begingroup$ I do not understand the question and I don't understand the answer. Perhaps knowing the reason for the question (research?) would help. $\endgroup$ Commented Dec 21, 2016 at 15:30
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    $\begingroup$ @Gianni Alessandro: I think my question is quite clear - I am asking for references that give examples of how increased drag counts (higher than expected drag coefficients) forced the manufacturer to drop the number of passengers to keep the aircraft range. I did not ask for an equation. It seems pretty clear to me that the relevant equation is the Breguet range equation. Just what is not clear about my question? $\endgroup$ Commented Dec 21, 2016 at 18:45
  • $\begingroup$ @user6035379: I don't see how the motivation for asking the question makes any difference to understanding it, but my motivation is simply curiosity, not research. $\endgroup$ Commented Dec 21, 2016 at 18:49
  • $\begingroup$ @user1362373 there are two people commenting and one person answering that didn't understand your question. You may be simply less arrogant and try to make it clearer to somebody that is freely trying to help you. $\endgroup$ Commented Dec 21, 2016 at 22:07

1 Answer 1


The book "Airplane Design Part I: Preliminary Sizing of Airplanes" by Jan Roskam covers this extensively.

Nothing tabulated, mind you but the text goes into extensive detail of the equations involved for the sizing of a prospective aircraft and the relationships between the aircraft range, drag polars under various flight conditions and payload weights.

It also gives the equations for calculating the sensitivity of the change of aircraft range with drag polar and payload weight, which is essentially what your passenger is.


Relevant section is in chapter 2 from page 74 onwards.Problem 1 on page 85 is practically custom tailored for your needs here.

Bear in mind there is no one size fits all application of a rule of thumb for this question as every aircraft will differ on account of any number of factors.

  • $\begingroup$ Thanks for your answer. I'm aware that the Breguet range equation can be used to see how increased drag results in reduced payload (reduced number of passengers). But in order to use that equation, quite a lot of information about the aircraft performance is required (CL, CD, SFC, etc). Therefore, I did not ask about the equation, but about the actual result: How increases in drag coefficients result in reduced number of passengers. $\endgroup$ Commented Dec 21, 2016 at 18:48
  • $\begingroup$ In the book Roskam does some regression modelling of aircraft of similar roles to come up with a couple of coefficients for use in some of the other (non breguet) equations. The Cd values can likewise be assumed or educated guesses made. $\endgroup$ Commented Dec 21, 2016 at 20:02
  • $\begingroup$ I'll take a look at Roskam's book, thanks. $\endgroup$ Commented Dec 22, 2016 at 7:24

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