GEM Research in the U.S. 297 
BIBLIOGRAPHY 
Liberatore, E.K., “GEM Activities and Bibliography,” Buffalo, Bell Aerosystems Co., 
Mar. 1960 
ADDENDUM 
ILLUSTRATIVE COMPARISON OF THE GROUND CUSHION CONCEPTS 
Direct comparisons between the various ground cushion concepts are very risky at the 
present state of the art. The simplified theory presented in the body of this paper neglects 
many factors, which may affect one concept more than another, and the degree of experi- 
mental understanding is by no means the same for all of the concepts. For this reason it 
was originally decided to avoid direct comparisons. 
However, in retrospect it became apparent that direct comparisons would go far toward 
clarifying many of the points made. It was decided to present the comparisons shown in 
Fig. 12 after all. The reader is implored to accept Fig. 12 as merely illustrative of some of 
the distinctive characteristics of the different concepts, and to use it cautiously or not at 
all as a criterion of their relative practical usefulness. 
100 
| % | of 
oo 
\p b = es G@) Simple Air Curtain 
=. Ss Q@) Air Curtain with Skegs 
: 4 (2/b= 4) 
4 @ Integrated Water Curtain 
o© RF (G/h = 0.005) 
4 ae el ©) Plenu= 
‘gn | jaca 
= 
| = Cruise Performance 
| <—! Per simplified ideal theory; 
Parasite drag limits shown: 
5 | Comparisons are illustrative only. 
| he =10 
S Pg % 
= a ay | = 4 (}) Integrated Air Cu-tain 
' 
' 
’ 
Equivalent Lift/Drag 
6.1 0.5 1.0 5 
Vv 
10 30 100 500 
L 
Vapn, ee =a 
