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National Advisory Committee for Aeronautics, Technical Notes - Flight and Wind Tunnel Tests of an XBM-1 Dive Bomber

Results are given of pressure-distribution measure—
ments made in flight over the right wing cellule and the
right half of the horizontal tail surfaces of a dive—
bombing biplane. Simultaneous measurements were also
taken of the air speed, control—surface positions, centrol
forces, and normal accelerations during various abrupt ma“
neuvers in a vertical plane. These maneuvers consisted
of push~downs and pull~ups from level flight, dives and
dive pulluouts, and push—ups from inverted flight.

In addition to the pressure measurements, flight
tests were made to obtain (1) wing-fabric deflections dur—
ing dives and (2) variation of the minimum drag coeffie
cient with Reynolds Number. Supplementary tests were also
made in the full~scale wind tunnel to obtain the d1aracter~
istics of the airplane under various propeller conditions '
and with various tail settings.

The results indicate that: (1) By decreasing the
fabric deflection between pressure ribs, the span load
distribution was considerably modified near the center and
the wing moment relations were changed; and (2) the mini—
mum drag was less for the idling propeller than for the'
propeller locked in a vertical position. The value of
03min was equal to K(Reynolds Number) 0 03 for a range
from 2,800,000 to 13,100,000.

This report summarizes the results of various tests
of a Navy dive bomber conducted in 1933- 34 by the N. A C. A.
at Langley Field, Va. These tests were made in accord—
ance with requests from the Bureau of Aeronautics, Navy
Department.

The primary objects were to obtain data on the wing
load distribution, the structural deformations of the
wing, the stresses in several wing members, and themaail
loads in the maneuvers for which the airplane was de—
signed. These data were then to be used by the Navy as a
check on the structural~design requirements that had been
established for this type of airplane. A secondary ob—
ject was to determine the effect of the structural defor—
mations on the load distribution by comparing the results
from the critical maneuvers with results obtained at the
same conditions of angle of attack but at such low air
speeds that the loads and corresponding deformations would
be negligible.