Are Textbooks Holy?

In my engineering practice, I have encountered issues several times when using equations given in textbooks. The issue was that the application of an equation yielded unrealistic results. It took hours to unveil the cause of the issue and arrive at the correct version of the equation. This work was done with frustration, anxiety, and self-distrust: a classic textbook cannot be wrong just because it cannot be wrong!

Well, it can. In some cases, there are more errors (for example, the textbook Aircraft Design by Eger unfortunately features many of them), and in some cases, fewer. To exclude all possible errors, somebody has to try all the equations before the book sees the light of day. Otherwise, the author is the only one who, at least in theory, can thoroughly and critically review all of the book's contents.

My recent negative but educational experience is related to the textbook 'Аэромеханика самолета' edited by Bochkarev (Бочкарев, А. Ф. (1977). Аэромеханика самолета. Москва: Машиностроение). In page 262, there is the equation for aircraft longitudinal equilibrium expressed for the forward center of gravity limit. Guys, here is the correct version of this equation:

I hope this post will save somebody's time and nerve cells.