The BE55 pilot reported on starting problems which resulted in noticeable smoke from the air filter.

Attributes
ACN	1328894
Time
Date	201601
Local Time Of Day	0601-1200
Place
Locale Reference	ZZZ.Airport
State Reference	US
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Make Model Name	Baron 55/Cochise
Operating Under FAR Part	Part 91
Flight Phase	Parked
Route In Use	Direct
Flight Plan	IFR
Component
Aircraft Component	Powerplant Installation
Person 1
Function	Pilot Flying Single Pilot
Qualification	Flight Crew Instrument Flight Crew Multiengine Flight Crew Flight Instructor Flight Crew Flight Engineer
Experience	Flight Crew Last 90 Days 150 Flight Crew Total 4500 Flight Crew Type 500
Events
Anomaly	Aircraft Equipment Problem Less Severe Flight Deck / Cabin / Aircraft Event Smoke / Fire / Fumes / Odor

Narrative:

When I arrived; the owner of the aircraft was already there waiting on me. The engines were shut down for only a short time so I preceded to start them using the 'hot start' procedure. The starter on the right engine was engaged for about seven seconds when the engine 'backfired'. I noticed that the battery was starting to get weak so I terminated the start on the right engine and tried to start the left engine. After about seven seconds the engine didn't start so I terminated the start on the left engine. That is when I noticed smoke coming from the air intake on top of the right engine nacelle so I preceded to emergency evacuate the aircraft. After everyone was clear I noticed that the smoke had turned black and was thicker so I used the onboard fire extinguisher to extinguish the fire. Upon inspection by a certified mechanic; it was found that the probable cause was the engine 'backfire' ignited the air filter which was determined to be the only damage to the aircraft.

Original NASA ASRS Text

Title: The BE55 pilot reported on starting problems which resulted in noticeable smoke from the air filter.

Narrative: When I arrived; the owner of the aircraft was already there waiting on me. The engines were shut down for only a short time so I preceded to start them using the 'hot start' procedure. The starter on the right engine was engaged for about seven seconds when the engine 'backfired'. I noticed that the battery was starting to get weak so I terminated the start on the right engine and tried to start the left engine. After about seven seconds the engine didn't start so I terminated the start on the left engine. That is when I noticed smoke coming from the air intake on top of the right engine nacelle so I preceded to emergency evacuate the aircraft. After everyone was clear I noticed that the smoke had turned black and was thicker so I used the onboard fire extinguisher to extinguish the fire. Upon inspection by a certified mechanic; it was found that the probable cause was the engine 'backfire' ignited the air filter which was determined to be the only damage to the aircraft.

Data retrieved from NASA's ASRS site 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.