DH 71 photo from NACA Aircraft Circular 57
NACA Aircraft Circular
1927-10-01
<a rel="nofollow" class="external free" href="https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19930090639.pdf">https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19930090639.pdf</a>