My outfit once rented a (small) ship to a TRE who wanted to renew/reval his qual - and I went along for the ride. After several VERY low approaches
w/out gear one of them oop front turned round and shouted "Hey, the GPWS isn't working".
"Maybe coz it isn't fitted?", was the sotto reply.
I still wonder how they managed to complete a pre-flight GPWS check, that might have convinced them that it *would* be...