FlightGlobal.com
Home
Premium
Archive
Video
Images
Forum
Atlas
Blogs
Jobs
Shop
RSS
Email Newsletters
You are in:
Home
Aviation History
1941
1941 - 0898.PDF
APRIL iyra, 1941. THE FOWLER FLAP The History and Applications of a Well-blown American Type of Wing Flap Wing Loadings of 75 Pounds/per Squ&fe Foot Predicted By HARlAN/D. The Consolidated 31 flying boat has a wing-loading of 48 lb./sq. ft. Its take-off and landing runs are kept to reasonable length by means of Consolidated-Fowler wing flaps. , SINCE its conception in 1916 the development of theFowler flap principle has passed through practicallyevery known stage oi the proverbial struggle of an invention conceived ahead of its time. In fact, twenty 3'ears passed before its first practical application to extensive commercial use. It may be interesting to briefly review this transition period. -The greatest difficulty surrounding the acceptance of a high lift device prior to about the year 1930 was the almost universal use of the biplane type of wing con- struction. The wing load- ing was low, ranging from 6 to 15 lb./sq. ft., repre- senting wing surfaces of extremely large proportions compared to present-day practice. Now the basic principle of the Fowler flap is (1) variable area, (2) vari- able camber and (3) a gap between the wing and fully extended flap. The combination of these factors was obtained by extending a separate airfoil surface from its closed position under the trailing surface of the wing rear- wardly and downwardly. This increased the chord of the wing. The aerodynamic effect was to so increase the cir- culation of the aii around the wing as to increase its lifting power. So large is this increase in lift under certain designed conditions, such as a 40 per cent, chord flap over the entire span of a wing, that the maximum lift of a normal wing is increased as much as 2J times. Despite these known facts it was practically impossible to break through the apathy towards the acceptance of the mono- plane type of wing construction, because it was by virtue of this extremely high increase in lift of the Fowler flap that it was possible to substitute a monoplane wing for a biplane. (Surely it would be more correct to say that it is high wmg loading, not monoplane construction, which has been made possible by the use of flaps?—ED.) Anyone familiar with the pioneering efforts of Anthony Fokker and THE Fowler flap first came into world prominence when fined to the Lockheed 14, that very useful civil airliner which was developed into the equally useful Coastal Command recon- naissance bomber, the Hudson. The Lockheed 14 appeared in 1937, so the author's statement that the principle of the flap was conceived in 1916 will come as a surprise to most people. The article is printed by courtesy of the Consolidated Company's journal, " Consolidator " Bellanca in introducing; the monoplane would understand this situation. Realising the importance of providing by actual flying demonstration the econojmic advantage of the Fowler flap, the writer constructed a jmonoplane wing incorporating this device An old-type Canuck aeroplane was obtained, its bi- plane wing of 330 sq. ft. area was removed and the mono- plane wing of 136 sq. ft. normal area, extended area 166 sq. ft., substituted. The test flight showed that the landing speed was about the same in both cases, but the top speed increased from 90 to 100 m.p.h. This increase in speed was equivalent to chang- ing the power of the engine from 90 to 135 h.p. These flight tests were made in 1927, and substantiated again in 1929, when the same wing was installed on a Pitcairn PA-3. It was not until 1934 that substantial progress was made. In that year a Fairchild F-22 was equipped with a specially designed wing and delivered to the Bureau of Aeronautics. This aeroplane had the unique experience of being tested in the National Advisory Committee for Aeronautics 60-foot wind tunnel and then subsequently flown. As compared to the original F-22 aeroplane the stall speed was reduced 7 m.p.h., the high speed increased nearly 4 m.p.h., and both the take-off and landing distances considerably reduced. Other Types of Flap In the same year, during the Fourth International Com- petition at Warsaw, the Fieseler Fi-97 took 5 of the 14 first places. The remarkable feature of this aeroplane was the use of full span Fowler flaps in combination with a new type of lateral control. This development was done in Germany. It should be noted here that the monoplane idea was
Sign up to
Flight Digital Magazine
Flight Print Magazine
Airline Business Magazine
E-newsletters
RSS
Events
