The Aerodynamic Characteristics of Flaps

To obtain A C .... from A C,/, we have the equation
= -1 +'C,,~ ~ 7 ~-1
AC,,,~ AC,.',. 4 c
Alternatively, we can obtain A C .... more directly, if somewhat less accurately, by using the
following relations :--
A C,,r
Z CL -- ff l(ci/c), from Fig. 13, for split and plain flaps,
= -- 0.34, for single and double N.A.C.A. slotted flaps,
= -- 0.43, for single and double Fowler flaps,
0.27 to --0.3, for single and double Blackburn flaps and a single Blackburn flap
with deflected shroud,
= -- 0.35, for Blackburn flap with leading-edge slat,
= -- 0.3 to --0.35, for Blackburn flap with inset slots,
= -- 0.5, for Venetian-blind flaps.
For these relations A CL corresponds to A = 6.
i4.3.2. Part-@an flaps.--For part-span flaps of all types ' '
C m (part span) : /2 2(bf/b) A C,,r (full span)
where ff 2(b/b) is given in Fig. 14.
14.4. :HighcLift flaps.--Foi; the other main characteristics and the geometry Of the high-lift
flaps considered see Table 2 and Fig. 1.
14.5: Wing-body Interference.--To
suggests that for split flaps
allow for wing-body interference, empirical evidence
/] CDO (with interference) = 0"854 CDO (without interference)
and for slotted flaps
A CDo (with interference) : I "4Z] CDO (without interference) .
There is no significant indication of interference effects on lift increments.
14.6. Wing Leading-edge Slats.--The effects of wing leading-edge slats are roughly additive
to those of flaps and when full span are given by
slat chord
ACrmax = 3"3 wing chord' approx.,
A C,,, (st) = 0"9
slat chord
wing chord' approx.
A ~(st) = 10 deg (+ 3 deg),
A(~C,,,/~CL)o.8OLmax = 0"15 (+0"075)
14.7. Effect of Flaps on Induced Drag.--The induced drag of a flapped elliptic wing is given by
C~i Cc ~ A CL ~
-- xA ~- K =A
where K is a function of flap geometry and A/ao is given in Figs. 18, 19, 20.
14.8. Kruger's Nose F/ap.--The characteristic of Kruger's nose flap are illustrated in Figs.
21, 22. The reduction in its effectiveness with increase of wing leading edge radius of curvature
is noteworthy (see Fig. 21d).
14.9. Brake Flaps.--Rough estimates of the effects of brXke flaps on lift, drag and pitching
moment can be obtained from the curves of Fig. 23.
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