Boeing 797 - An Internet Hoax

by Kenneth J. Kahn

The aircraft depicted below (fig.1) is an Internet hoax. My analysis is below the drawing.

b797-1.jpg
fig. 1

This analysis is divided into the sections listed below. All dimensions and numbers for the 797 are estimates made by me using the stated figure of 265' for the wingspan as a scale.

Operational Considerations
Performance and Structure
Final Thoughts

Operational Considerations
FAA certification of an airliner requires a demonstration that a full load of passengers can be evacuated within 90 seconds with half of the exits blocked (FAA regulations, section 25.803). The only exits clearly depicted are four under the trailing edge and perhaps one behind the cockpit. All of these would be blocked in a ditching or gear-up landing. With all of the passengers inside the wing, there are no conventional doors or over-wing exits. Doors could be provided in the leading edge but such doors would require a leading edge much blunter than aerodynamically optimum. The rear-most passengers would be as far as 76' from the nearest leading-edge exit making it difficult to meet the evacuation requirement. Such doors and the exits shown would all have compatibility problems with current jetways. There would be no window seats with the possible exception of front-row passengers who are as far as 30' from the leading edge.

Performance and Structure
In the 1930's and 1940's, German aerodynamicists learned that the most-efficient wings for cruise at subsonic Mach numbers were swept back and had high aspect ratios and low thickness ratios. These lessons were applied by Boeing with great success to the B-47 bomber and later to the Boeing 707, the first successful long-range jet airliner. Aspect ratio (AR) is defined as b²/s where b is the wingspan and s is the wing area. For a rectangular wing, this formula simplifies to b/c where c is the chord, the distance from the leading edge to the trailing edge. The two examples shown in fig. 2 have equal wing areas.

ar.gif
fig. 2

The thickness ratio is t/c where t is the maximum thickness of the wing and c is the chord at a particular wing section as shown in the example in fig. 3.

tr.gif
fig. 3

The most efficient airliner in service today is the Boeing 787. Its aspect ratio is 10.58. For the 797, the estimated aspect ratio is 6.8, far less than optimum. The thickness ratio for the 787 is .134 at the wing root (next to the fuselage) reducing to .088 at the wingtip. On the 797, the wing thickness must be sufficient so that passengers can stand erect for the full length of the outermost aisles and place carry-on luggage in overhead bins.

Final Thoughts

For the reasons stated, I do not think that configurations such as the one in fig. 1 are suitable for the carriage of either passengers or freight; at least given the present state of technology. Finally, however, the last word goes to Boeing:

http://boeingblogs.com/randy/archives/2006/11/air_mail.html
Top

© 2013, 2010  Reproduction of any material on this Web site is prohibited without prior written consent