Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Flight Instructor
Flight Crew Last 90 Days 22; Flight Crew Total 3300; Flight Crew Type 600
Communication Breakdown; Distraction; Situational Awareness
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy; Ground Event / Encounter Gear Up Landing
Aircraft Aircraft Damaged
Human Factors
We were on a night training flight for night currency. The Pilot Flying was planning to update their night currency. I was acting as PIC (Pilot-in-Command)/CFI/PNF (Pilot Not Flying) in the right seat. We met at the airport approximately XA:45. After preflighting the aircraft we started engines at approximately XB:20. Some engine roughness was noted at startup but was resolved after leaning and run-up checklist was completed.  Additional time was lost waiting for a transient aircraft who was lost on the airport trying to find his way to a gate for exit. I informed the Pilot Flying to hold position until the transient airplane was clear of all runways. We offered assistance via radio to the transient pilot whom we directed to the ramp.We made a normal takeoff on Runway XXL; retracted the landing gear; and entered a normal left traffic pattern. On downwind we extended the landing gear and continued to a normal landing with full stop. We then taxied back for another takeoff and entered the downwind leg. Upon reducing power for the approach we noticed some engine roughness which I attributed to 'pushing the prop' because of our relatively high airspeed and being full rich at minimal power. The Pilot Flying thought it was an engine malfunction so I attempted to adjust the mixture to no satisfaction to the Pilot Flying. I directed the PF (Pilot Flying) to go to full flaps for landing as we were turning final and speed seemed high. We continued the approach to landing and failed to do a 'GUMP' check for landing gear due to our distraction resulting from the engine issue.We did not get a gear warning alarm even though the MP (Manifold Pressure) was at 11 inches. Had that alarm sounded; we would have; if time and altitude allowed; been able to extend the landing gear or otherwise execute a go-around. This is a case of two senior pilots trusting each other to 'take care of business'. The distraction with the engine caused me to forget the pre-landing checklist which I assumed the PF was managing but was really my responsibility as CFI/PIC. The result was a gear-up landing which resulted as a very smooth landing with minimal damage to the aircraft and no injuries to personnel.
BE36 flight instructor reported a gear-up landing after being distracted by engine issues.