There isn't one. The bomb animations are baked into persistent fx that creates the ship and all associated pieces, so it's not possible to spawn one without them, even through trickery. Even the dev /fxkill command won't help because it will make the ship geometry itself disappear as well.
So the only option is to hack fxinfo.bin itself to null out the reference to the bomb fx.
https://www.dropbox.com/s/nt4m6b06kfvfv6d/dropship.7zExtract that into your icon directory under data/. Create the data directory if it's not there. The final path should look like [COH]\data\bin\fxinfo.bin. With that in place, all dropships will be missing the bomb effects.
While I was looking into it, I also happened to glance at the sequencers for that entity type in case it was just a ready loop or something easy. I found that you can target the dropship and use
/mov Forward_Pre
to make it fire its thursters if you want. You can then use
/mov Ready
to return them to idle mode.