PA-23-250 Aztec
Flight Crew Commercial; Flight Crew Instrument; Flight Crew Multiengine; Flight Crew Flight Instructor
Flight Crew Last 90 Days 133; Flight Crew Total 900; Flight Crew Type 45
Troubleshooting; Communication Breakdown; Distraction
Aircraft Equipment Problem Less Severe; Flight Deck / Cabin / Aircraft Event Smoke / Fire / Fumes / Odor
Air Traffic Control Separated Traffic; Flight Crew Landed As Precaution; Flight Crew Overcame Equipment Problem; General Maintenance Action
Aircraft
Flying at a cruise altitude of 6;500 feet 5 miles east of [destination] airport in VFR conditions; began to smell a burning/smokey scent in the cockpit; looked around the cockpit in search of a source and found smoke coming from the instrument panel where the aileron trim gauge is located after turning the master switch off. While the master was off we searched for a Circuit Breaker (CB) for the electrical aileron trim and did not find an associated CB for the aileron trim which is why we left the master off and why we did not attempt to turn the master back on to use the radios. The needle inside the gauge was melted; landed without radio communications at the [destination] airport after entering the pattern at 2;500 AGL; making multiple high passes observing the pattern followed by light gun signals from the tower controller in which we made a successful landing with no injuries.Mechanic looked at our aircraft briefly; saying that he believes this was due to a short in the electrical system with the electric aileron trim. Aircraft is currently with maintenance.Suggest checking more often or replacing old age instruments more often to prevent situations like this. Specific circuit breaker for this instrument should be added to prevent loss of radio communications be it VFR or IFR where the following could create a greater safety risk.
[Report narrative contained no additional information].
Two pilots experienced smoke in the cockpit and a successful landing after receiving light gun signals.