looking for Issoudun squadron listings

Trying to find the squadron my grandfather was in while training in Issoudun, France. Have picture of him next to Nieuport 17 with scull and cross bones. Any help on this would be greatly appreciated. Thanks.....Steve

[Cliff]

Issoudon was the 3rd Instruction Center and personnel would go thru training there before being assigned to the aero squadrons.
The skull and crossbones insignia was used on a group of nieuport scout trainers there.

Cliff

Cliff, Thank you for responding to my request about Issoudun and the scull and cross bones insignia. If you have any more information,like squadrons and personnel lists or pictures, please let me know