PA30 pilot is informed by the tower after takeoff of 'smoke' from the right engine. The reporter det...

Narrative:

Upon departure; tower indicated that smoke was flowing from the right engine. We checked and determined it was vapor/fuel coming from the aux fuel tank. We returned to the airport and landed without incident to check out the situation. Upon landing we found that the latch covering the fuel cap had come open and the fuel cap was gone. As a precaution; we asked the tower to check the runway for the cap to ensure that if it came off during takeout other aircraft would not be affected. Maintenance found the cap and returned it to us as we were having the aircraft put away. I checked the airplane during preflight and the cap and latch were secure. My co-pilot also confirmed the latch was secure prior to takeoff. Given the morning was very cold; around 10 degrees fahrenheit; I believe the rubber which expands when turning the knob on the fuel cap was not as effective as it would normally be on a warmer day. To correct future problems we will just replace these caps every 6-12 months to provide a better chance for a good seal. In addition; although we checked the fuel door latch during preflight; we will give this additional attention every time we fly; even though this is the first time this has happened in owning and operating this aircraft for over 10 years.

Original NASA ASRS Text

Title: PA30 pilot is informed by the Tower after takeoff of 'smoke' from the right engine. The reporter determines that fuel vapor is coming from the auxiliary fuel tank. Upon returning the auxiliary tank cap is found missing.

Narrative: Upon departure; Tower indicated that smoke was flowing from the right engine. We checked and determined it was vapor/fuel coming from the aux fuel tank. We returned to the airport and landed without incident to check out the situation. Upon landing we found that the latch covering the fuel cap had come open and the fuel cap was gone. As a precaution; we asked the Tower to check the runway for the cap to ensure that if it came off during takeout other aircraft would not be affected. Maintenance found the cap and returned it to us as we were having the aircraft put away. I checked the airplane during preflight and the cap and latch were secure. My co-pilot also confirmed the latch was secure prior to takeoff. Given the morning was very cold; around 10 degrees Fahrenheit; I believe the rubber which expands when turning the knob on the fuel cap was not as effective as it would normally be on a warmer day. To correct future problems we will just replace these caps every 6-12 months to provide a better chance for a good seal. In addition; although we checked the fuel door latch during preflight; we will give this additional attention every time we fly; even though this is the first time this has happened in owning and operating this aircraft for over 10 years.

Data retrieved from NASA's ASRS site as of April 2012 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.

Attributes
ACN	927094
Time
Date	201101
Local Time Of Day	0601-1200
Place
Locale Reference	ZZZ.Airport
State Reference	US
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	PA-30 Twin Comanche
Operating Under FAR Part	Part 91
Flight Phase	Takeoff
Route In Use	None
Flight Plan	None
Component
Aircraft Component	Fuel Tank Cap
Person 1
Function	Pilot Flying
Qualification	Flight Crew Instrument Flight Crew Multiengine Flight Crew Air Transport Pilot (ATP) Flight Crew Flight Instructor
Experience	Flight Crew Last 90 Days 15 Flight Crew Total 3000 Flight Crew Type 700
Events
Anomaly	Aircraft Equipment Problem Critical

PA30 pilot is informed by the tower after takeoff of 'smoke' from the right engine. The reporter determines that fuel vapor is coming from the auxiliary fuel tank. Upon returning the auxiliary tank cap is found missing.