Bonsoir
As you certainly know, a lot of official archives of french ww1 military aviation had been destroyed in 39-40
Hopefully the roster of the escadrille HD 174 still exists but only for the second
quarter of 1919
Looking at the photo,season were it was taken was certainly spring or summer
(of 1919 or 1920 ??)
The pilot( or observer ?) is sous-lieutenant or adjudant
I dont know him , but look familiar
here is the roster of that escadrille on 2nd quarter of 1919
Mémoire des hommes
Cordialement
Bruno
click on 'controle des officiers et controle de la troupe ' on the arrow at top