A C185 pilot lost fuel in-flight; the right tank vent was exposed and forced fuel out the left tank....

Narrative:

Enroute it was discovered that fuel was being forced out of the left wing tank vent. The fuel could be seen being blown out of the vent in small bursts. A precautionary landing was made. Fuel was requested; the left tank was full; and the right tank required 21.5 gallons to top it off. The right tank vent was exposed to the oncoming air more than the left causing the fuel in the right tank to be forced into the left. The right fuel tank vent was readjusted upward. Departing runup and takeoff were normal. Enroute the engine hesitated and began to lose fuel flow. The engine failure checklist was followed; and a landing at a major class B airport was requested. The controllers cleared us to land runway 29. The engine continued to run and the landing was normal. After taxing to the ramp and shutting down the aircraft it was discovered that the left tank cap was hanging by its chain and not secured. The fuel caps on this C185 are monarch fuel caps; they require more turning than normal caps to secure. They are more similar to those found on automobiles where they are rotated until they stop and continue until you receive clicks to let you know that the cap it is secure. The fueling of the aircraft at the previous airport was observed. Even though the both fuel caps appeared from the ground to be correctly secured; they should have been reinspected by the PIC. On the final flight to my destination all systems were normal.

Original NASA ASRS Text

Title: A C185 pilot lost fuel in-flight; the right tank vent was exposed and forced fuel out the left tank. On the next flight a rough running engine resulted when the Monarch fuel caps were not fully secured. Precautionary landings were make in both events.

Narrative: Enroute it was discovered that fuel was being forced out of the left wing tank vent. The fuel could be seen being blown out of the vent in small bursts. A precautionary landing was made. Fuel was requested; the left tank was full; and the right tank required 21.5 gallons to top it off. The right tank vent was exposed to the oncoming air more than the left causing the fuel in the right tank to be forced into the left. The right fuel tank vent was readjusted upward. Departing runup and takeoff were normal. Enroute the engine hesitated and began to lose fuel flow. The Engine Failure checklist was followed; and a landing at a major Class B airport was requested. The Controllers cleared us to land Runway 29. The engine continued to run and the landing was normal. After taxing to the ramp and shutting down the aircraft it was discovered that the left tank cap was hanging by its chain and not secured. The fuel caps on this C185 are Monarch fuel caps; they require more turning than normal caps to secure. They are more similar to those found on automobiles where they are rotated until they stop and continue until you receive clicks to let you know that the cap it is secure. The fueling of the aircraft at the previous airport was observed. Even though the both fuel caps appeared from the ground to be correctly secured; they should have been reinspected by the PIC. On the final flight to my destination all systems were normal.

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	931913
Time
Date	201102
Local Time Of Day	1201-1800
Place
Locale Reference	ZZZ.TRACON
State Reference	US
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	Skywagon 185
Operating Under FAR Part	Part 91
Flight Phase	Cruise
Route In Use	Direct
Flight Plan	None
Component
Aircraft Component	Fuel Tank Cap
Person 1
Function	Pilot Flying
Qualification	Flight Crew Air Transport Pilot (ATP) Flight Crew Multiengine Flight Crew Instrument Flight Crew Flight Instructor
Experience	Flight Crew Last 90 Days 55 Flight Crew Total 32500 Flight Crew Type 420
Events
Anomaly	Aircraft Equipment Problem Less Severe Deviation - Procedural Published Material / Policy Inflight Event / Encounter Fuel Issue

A C185 pilot lost fuel in-flight; the right tank vent was exposed and forced fuel out the left tank. On the next flight a rough running engine resulted when the monarch fuel caps were not fully secured. Precautionary landings were make in both events.