I read an article that stated it can only perform a limited number of unimproved field landings due to fod / airframe ? vulnerability.
Two comments:
1. Only rotorcraft land at an "unimproved field". Fixed wing transports, no matter how rugged, generally land at what USAF calls "semi-prepared" fields, which is to say unpaved runways.
2. Many civil aircraft can routinely operate from unpaved fields, so it does not take any really special design features to be able to operate from unpaved fields.