1R37. Flight Vehicle Performance and Aerodynamic Control. AIAA Education Series. - FO Smetana (N Carolina State Univ, Raleigh NC). AIAA, Reston VA. 2001. 359 pp. CD-ROM included. ISBN 1-56347-463-8. $119.95.
Reviewed by EE Covert (Dept of Aeronaut and Astronaut, MIT, 77 Massachusetts Ave, Rm 9-466, Cambridge MA 02139-4307).
The author’s purpose is “…to explain to beginning aerospace engineering students typical methods used to estimate performance of aircraft…[and] how various parameters derived from aircraft geometry can be used to estimate size, shape and location of control surfaces and aerodynamic forces to actuate these surfaces.” The author adds, “A unique feature of this volume is the inclusion of time tested computer programs…intended to be pedagogical tools….” The author provides detailed explanations for the student users of these codes.
The chapter titles are: 1) Basic Notation; 2) The Atmosphere; 3) Characteristics of Power Plants; 4) Flight Vehicle Lift Drag Characteristics; 5) Equations of Motion; 6) Determination of Aerodynamic Characteristics; 7) Flight Vehicle Performance; 8) Aerodynamic Control Forces and Static Stability; and 9) Flight Vehicle Control.
The selection of material in such a text is partly a matter of personal philosophy and partly experimental. For example, the author has chosen to provide a detailed development of the rigid body dynamics in Chapter 5, including those terms which account for the variation of mass and moments of inertia with time. He then develops the standard small perturbation approximation and makes the underlying assumptions clear at each step in the simplification. For simplicity, the author restricts the aerodynamics and geometries to low speed flows in both the text and the examples.
Each chapter ends with a large number of homework problems, each of which were well stated for the problems the reviewer worked. The author’s love of aircraft is evident in the photographs, the examples, and in the homework problems.
The book has unusually few typographical errors. On page 114, an upper case “W” is used in place of a lower case “w,” which may confuse some students as will the use of “Z” for “X” on page 253; #8. On page 115, in Eq. (5.25) the use of “W” for weight has the potential to confuse the student since the preceding discussion uses “W” as vertical velocity. The use of alpha for angle of attack was not introduced prior to page 76 and is never defined. Its use in that capacity can be inferred by discussion as the slope of the lift curve with respect to alpha. [Added comment — There is a typographical error in Eq. (6.1) p 75, and (6.2) p 76; a “1/2” is missing from the denominator, which the users of the text will want to correct explicitly.]
On occasion, the author introduces other terms prior to their definition. This reviewer is sympathetic with this kind of omission because the terms in question are so commonly used by aeronautical engineers, but the students have yet to reach this level of sophistication. Users of this text must be prepared for this type of question.
In this reviewer’s experience, considerable care must be taken not to confuse the beginning student, which at times requires an author to use a more careful choice of words and a more extended explanation than otherwise might be needed. For example, in Section 2.1.2 on page 42, on model testing, this reviewer feels that the explicit addition of the requirement of geometric similarity as a similarity condition together with the uniform flow Reynolds number would clarify the discussion. This statement relieves the student from inferring such a condition through the use of the word model (which has come to have a wider meaning, such as in the term mathematical model), and is broader since geometric similarity includes the angle with respect to the relative wind.
Another concern along this line is the discussion of induced angle of attack in Section 4.4 on page 76. The statement is made that the change in flow direction is a reaction to the lift and thus a consequence of Newton’s Second Law. This misuse of Newton’s Second law raises two pedagogical difficulties. First as the induced angle of attack vanishes for an infinite aspect ratio (or span), the perceptive student might ask why there is no downwash in two-dimensional flow (there is lift, but no downwash). Second, the perceptive student may recall that pressure was important in the use of the momentum theorem to model actuator disk model for generation of thrust (page 56) and wonder why the pressure is not included here.
This reviewer feels that the idea of downwash can be introduced without a detour into the horseshoe vortex model by merely looking at the wing from in front. One notes the higher pressure on the lower surface at the tip drives the flow around the tip towards the region of lower pressure on the upper surface. A simple sketch makes downwash plausible.
A few other small complaints. On Fig. 4.11 (p 93) the airfoil has a stagnation point at the trailing edge. Rauscher has proved that there is no stagnation point on an airfoil with a cusped trailing edge. Joukowski airfoils have a cusped trailing edge. Thus the legend on the figure must be in error. A number of the figures in Section 7.41, starting on page 171, are computer drawn with no regard to the value of interval on the ordinate and abscissa. As such, the figures are less than a crude depiction of the variation of one parameter as another is changed. On page 179, the Fig. 7.13 wing area is given to five significant figures, and the weight to three significant figures. This reviewer feels that introductory students need a sense of size, so the use of numbers is laudable, but these same students need to develop a sense of the false accuracy implied by an inappropriately large number of significant figures.
All this being said, the author has met his goal, and Flight Vehicle Performance and Aerodynamic Control contains a great deal of practical information and ought to be in university libraries. As for the selection of this as a textbook, the reviewer has not taught for several years and cannot judge the readiness of current second-year students, and will thus suggest that those who teach introductory aerodynamics and design make this judgment after reading the book.
Finally, two practical issues seem to warrant general comments. First, this reviewer assumes that the author retains responsibility for the codes and users of the text should correspond with the author about code maintenance. Second, the reviewer readily admits he neither tried to use the programs included on a floppy disk, nor tried to evaluate the source code. This leads to an open question for reviewers in general. Should reviewers take the time and effort to learn to validate and use the codes included with the text as part of the review process?