Narrative:

This was a revenue; part 135; flight in a hawker 700. The crew consisted of myself (designated PIC) and a copilot. Both pilots were type rated and current in type. The WX was good (clear with excellent visibility) the temperature was approximately +5 degrees C and runway conditions were dry. 6 passenger and their baggage were on board for a return trip to ZZZ1. I commented to the copilot that the cockpit smelled like 'dirty socks' as I entered the cockpit just before engine start. Figuring the source of this smell to be sweat rags the pilots used during hot WX and stored in the side pilot pockets; I paid no more attention to the smell. All checklists from preflight to taxi had been completed. No abnormalities or annunciator panel lights indicated a problem. Just before powering up for takeoff at the end of the runway; the passenger called out to me and I turned around to face them and immediately noticed a small amount of smoke in the entry way (airstair) area of the floor. I immediately instructed the copilot to inform CTAF that we were terminating the takeoff and returning to the ramp. During return to the tarmac; both the copilot and me checked for any indications (annunciator light or gauge) of a problem. None were noted. I stopped the aircraft once we were clear of the runway (uncontrolled field precaution); and proceeded to deplane the passenger as per the emergency checklist memory items. I shut down the aircraft as per the checklist; as the copilot took the passenger back to the FBO. As I departed the aircraft; I disconnected the main ship batteries as an additional precaution. The company dispatch and maintenance were contacted; the passenger were provided with another flight home. The aircraft was repaired and the problem was determined to be in the electrical circuit that provided power to the entry and emergency lighting. Since the problem was caught relatively early and on the ground; passenger discomfort and aircraft damage was minimal. I believe that crew training and experience played a pivotal role in resolving the situation without major problems. Crew understanding of aircraft system and procedures for emergencys minimized problems and led to a safe and happy ending for all. Callback conversation with reporter revealed the following information: reporter stated this aircraft does have a 'tks' anti-ice system with a fluid reservoir tank below the door entry threshold. The damaged electrical wire bundle was original installation and was found by maintenance to have fused (melted) together; perhaps from years of in-flight turbulence and chafing. Reporter also stated he wasn't sure; but didn't think that residual fluid from the servicing of the anti-ice fluid reservoir necessarily caused the shorted wiring. This original wire bundle was not replaced during the cabin mod upgrade; but continued in use providing power to the entry door and emergency lighting.

Google
 

Original NASA ASRS Text

Title: AN HS125-700 HAWKER CAPTAIN REPORTS OF A 'DIRTY SOCKS' SMELL IN THE COCKPIT AND PASSENGERS NOTICED SMOKE IN DOOR ENTRY AREA JUST PRIOR TO TAKEOFF.

Narrative: THIS WAS A REVENUE; PART 135; FLT IN A HAWKER 700. THE CREW CONSISTED OF MYSELF (DESIGNATED PIC) AND A COPLT. BOTH PLTS WERE TYPE RATED AND CURRENT IN TYPE. THE WX WAS GOOD (CLR WITH EXCELLENT VISIBILITY) THE TEMP WAS APPROX +5 DEGS C AND RWY CONDITIONS WERE DRY. 6 PAX AND THEIR BAGGAGE WERE ON BOARD FOR A RETURN TRIP TO ZZZ1. I COMMENTED TO THE COPLT THAT THE COCKPIT SMELLED LIKE 'DIRTY SOCKS' AS I ENTERED THE COCKPIT JUST BEFORE ENG START. FIGURING THE SOURCE OF THIS SMELL TO BE SWEAT RAGS THE PLTS USED DURING HOT WX AND STORED IN THE SIDE PLT POCKETS; I PAID NO MORE ATTN TO THE SMELL. ALL CHKLISTS FROM PREFLT TO TAXI HAD BEEN COMPLETED. NO ABNORMALITIES OR ANNUNCIATOR PANEL LIGHTS INDICATED A PROB. JUST BEFORE POWERING UP FOR TKOF AT THE END OF THE RWY; THE PAX CALLED OUT TO ME AND I TURNED AROUND TO FACE THEM AND IMMEDIATELY NOTICED A SMALL AMOUNT OF SMOKE IN THE ENTRY WAY (AIRSTAIR) AREA OF THE FLOOR. I IMMEDIATELY INSTRUCTED THE COPLT TO INFORM CTAF THAT WE WERE TERMINATING THE TKOF AND RETURNING TO THE RAMP. DURING RETURN TO THE TARMAC; BOTH THE COPLT AND ME CHKED FOR ANY INDICATIONS (ANNUNCIATOR LIGHT OR GAUGE) OF A PROB. NONE WERE NOTED. I STOPPED THE ACFT ONCE WE WERE CLR OF THE RWY (UNCTLED FIELD PRECAUTION); AND PROCEEDED TO DEPLANE THE PAX AS PER THE EMER CHKLIST MEMORY ITEMS. I SHUT DOWN THE ACFT AS PER THE CHKLIST; AS THE COPLT TOOK THE PAX BACK TO THE FBO. AS I DEPARTED THE ACFT; I DISCONNECTED THE MAIN SHIP BATTERIES AS AN ADDITIONAL PRECAUTION. THE COMPANY DISPATCH AND MAINT WERE CONTACTED; THE PAX WERE PROVIDED WITH ANOTHER FLT HOME. THE ACFT WAS REPAIRED AND THE PROB WAS DETERMINED TO BE IN THE ELECTRICAL CIRCUIT THAT PROVIDED PWR TO THE ENTRY AND EMER LIGHTING. SINCE THE PROB WAS CAUGHT RELATIVELY EARLY AND ON THE GND; PAX DISCOMFORT AND ACFT DAMAGE WAS MINIMAL. I BELIEVE THAT CREW TRAINING AND EXPERIENCE PLAYED A PIVOTAL ROLE IN RESOLVING THE SITUATION WITHOUT MAJOR PROBS. CREW UNDERSTANDING OF ACFT SYS AND PROCS FOR EMERS MINIMIZED PROBS AND LED TO A SAFE AND HAPPY ENDING FOR ALL. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: REPORTER STATED THIS ACFT DOES HAVE A 'TKS' ANTI-ICE SYSTEM WITH A FLUID RESERVOIR TANK BELOW THE DOOR ENTRY THRESHOLD. THE DAMAGED ELECTRICAL WIRE BUNDLE WAS ORIGINAL INSTALLATION AND WAS FOUND BY MAINT TO HAVE FUSED (MELTED) TOGETHER; PERHAPS FROM YEARS OF IN-FLIGHT TURBULENCE AND CHAFING. REPORTER ALSO STATED HE WASN'T SURE; BUT DIDN'T THINK THAT RESIDUAL FLUID FROM THE SERVICING OF THE ANTI-ICE FLUID RESERVOIR NECESSARILY CAUSED THE SHORTED WIRING. THIS ORIGINAL WIRE BUNDLE WAS NOT REPLACED DURING THE CABIN MOD UPGRADE; BUT CONTINUED IN USE PROVIDING POWER TO THE ENTRY DOOR AND EMERGENCY LIGHTING.

Data retrieved from NASA's ASRS site as of January 2009 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.