BAe 125 Series 800
Flight Crew Air Transport Pilot (ATP); Flight Crew Flight Instructor; Flight Crew Instrument; Flight Crew Multiengine
Flight Crew Last 90 Days 46.; Flight Crew Total 10555.; Flight Crew Type 3100.
Aircraft Equipment Problem Less Severe; Ground Event / Encounter Loss Of Aircraft Control; Ground Event / Encounter Object
Air Traffic Control Provided Assistance; Aircraft Aircraft Damaged; Flight Crew Regained Aircraft Control; Flight Crew Requested ATC Assistance / Clarification; General Maintenance Action
Aircraft
My colleague & I were returning empty on an IFR flight plan Part 91 from ZZZ. I was in the right seat acting as SIC while my colleague was flying the aircraft from the left seat & acting as PIC. We switch roles in order to maintain our skills. The before landing checklist was performed after gear extension. This was done in a command / response manner. The landing was normal until the moment the nose tire contacted the runway. The airplane began veering hard to the right. My colleague was making every effort to return to the centerline of the runway but it was not bearing fruit. When we were about to exit the runway; I shouted 'steering!' At the same time; I checked to see whether the left rudder was pushed in. It was. We went traveling across a section of rocks. In doing so; we knocked over a taxiway sign & a light. The aircraft suffered FOD damage to both engines; wings & landing gear. There was also a fuel spill. I want to commend my colleague for regaining aircraft control the way he did. For a moment there; it was dicey when we were headed toward parked aircraft. Several possibilities come to mind: A centered tiller indication with a nose tire that was not actually centered. Confirmation bias with an uncentered tiller interpreted as a centered one. Something else.
After landing the airplane started to veer to the right and I immediately added left rudder to counteract the situation. When the aircraft continued to the right; I then applied full left rudder and to no avail the aircraft exited the runway to the right. At that time I decided to decelerate straight ahead to avoid any side loads that may collapse the landing gear in the rocky surface between the runway and the taxiway. In retrospect I will add on final a quick glance at the nose wheel tiller pointer to make sure it is pointing perfectly forward. My other advice is to delicately use as a last effort  the tiller above 80 KIAS to attempt to keep the aircraft on the runway.
HS-125 flight crew reported loss of directional control during landing resulting in a runway excursion.