The Esri FLT data format stores its data identically to an Esri BIL file, which GDAL does support:
GDAL_Translate -of EHdr -ot Float32 ....
Then all you need to do is change the extension from bil to flt and edit the header - the keywords are different.. for example:
is what is in the header from GDAL translate, which needs to be changed to:
for a FLT file... easy as!
First change NODATA to NODATA_VALUE (if not already, both keywords are supported by Esri BIL),
BYTEORDER keyword changes from
I (Intel) to
LSBFIRST - assuming Intel, only one cellsize is supported so get rid of
XDIM, YDIM and replace with
XLLCENTER and then it gets tricky.. BIL is upper left referenced but FLT is lower left referenced so you need to reduce the reference by
NROWS * CELLSIZE to obtain
You should be able to validate your results in QGIS (I used 2.6 (Brighton)) by drag-n-drop the .flt file into the window.