Yep, could be that. Certainly nothing to do with yaw stability, though they
will have some effect at speed.

"RustY©" wrote in message
...

"PVK" wrote in message
...

I've never noticed those flat plates sticking down from under the
Harrier's
fuselage before. Any idea what they are for ?

I can't say that I have ever thought about them but how about blast
shields
for the centreline stores for when the jet nozzles are pointing downwards
?
They do look as though they are in the right place to be deflectors.