Narrative:

After takeoff from falcon field a right turn was made with a GPS direct prescott route of flight. Upon reaching 3900 ft I noticed an unusual reading on my fuel flow computer. The gph flow on the left engine had dropped slightly in the climb; as we were about to reach the bottom of the class B airspace when the fuel flow reading dropped to 11.2 gph on the left engine. The aircraft had been in maintenance in the past several weeks for a fuel flow check based on a recent owner advisory from cessna. The outside air temperature (OAT) at this point was approximately 90 to 95 degrees and climbing with a forecast high of 114 degrees fahrenheit. As mentioned; all of a sudden the left engine fuel flow dropped to 11.2 gph (both engine fuel flows had been reading approximately 23.5 gph). My location was approximately 8 miles northwest of falcon field with a class B ceiling of 4000 ft. I was also within ten miles of scottsdale airport. I observed the drop for about twenty (20) seconds; and the fuel flow did not improve. I then made the decision to go through a standard diagnostic to determine whether or not I might be facing an emergency shut down of the left engine. Since it was a hot and getting hotter I made the decision to initiate a gentle climb in order to ensure that I had enough altitude in case I had to return to either airport. Climb performance was estimated to be in the 200 FPM range with the elevated temperatures. Falcon is a student training airport with lots of flight activity and scottsdale; was fairly light in traffic when I left; so I proceeded northwest bound and began my diagnosis. I wanted enough altitude so that if I did have an emergency; I could return to either airport recognizing that at falcon there would be more traffic - however it was closer at this point. I climbed approximately 600 ft into the class B airspace - I was not authorized to do so but felt it was key to managing the potential emergency. I did not at this point in time call an emergency for a low fuel flow; nothing of significance had yet happened. I first cross-referenced the fuel flow computer with the standard analog fuel gauge; which was installed on the co-pilots side. The fuel flow computer read 11.2 gph and the analog gage read 21.5 gph. The fuel flow computer for the right engine read 23.5 gph and the analog for the right engine read 22.8 gph - at this time I felt that further diagnosis was required before taking the next step of either shutting the engine down and/or calling an in-flight emergency. I chose to keep current heading until I could further assess the situation for I still had both airport options with a decision to proceed to scottsdale if the situation worsened. At this point I had entered the class B airspace without ATC approval. I did not call ATC; I instead focused on both flying the airplane as well as diagnosing the problem. I planned to call ATC once I had resolved the issue. I proceeded with my diagnosis as follows:1) I immediately checked all egt's and cht's made records of the readings; and found the readings from the left engine to be in the same range as the right engine. This I believe ruled out the possibility of an immediate engine failure; however; I wanted to continue to try and understand the reading before I made the decision to return to either airport. If I had been IMC I would have made the immediate decision to return to falcon field. 2) I switched the left engine fuel source to auxiliary (in order to determine whether or not I had a fuel pump failure); and the left fuel flow returned to normal (reading approximately 22.5 gph). I left the left engine fuel flow configuration in auxiliary's tank mode for approximately two minutes and all appeared normal. 3) I then switched the left engine fuel source back to main and the computer fuel flow reading was normal. The fuel flow anomaly was no longer present. All three of these diagnostics allowed me to believe that the most likely source of the low fuel flow reading was either a semi-broke wire on the fuel transducer and or a failing transducer. I again check the left engine cht's and egt's and found them to be in the same range of the left engine. The aircraft will be sent to maintenance to check the fuel flow transducer. At this point in time I had transitioned to the next step in the phoenix class B (6000 ft) and I was under the airspace ceiling. Again; the unauthorized incursion into the class B airspace was for the sole purpose of getting some additional altitude in case of a left engine failure and having to operating the C310T on a hot day in phoenix with it single engine performance characteristics. As indicated I had passed into the next ring of the class B airspace. Recognizing that I had violated the airspace; I had planned to call phx TRACON upon my arrival in prescott (provided that I had no further fuel flow problems for I would have immediately returned to scottsdale). After about six to eight minutes of flight I observed that the fuel flow computer was performing normally. Egt's and cht's were in line and I made the decision to proceed to prescott. The rest of the flight was uneventful; both to prescott; then back to falcon field. No further fuel flow glitches were observed. Upon starting to make my approach for the ILS to runway 21L; prescott tower asked me to call albuquerque center for a message. Abq center asked me to call phoenix TRACON upon my landing; which I did. Phoenix TRACON told me that I had violated their airspace upon departure; I acknowledged that I did; and explained my reasoning (the full above scenario) regarding the fuel flow issue. They indicated that they would pass on this information to the scottsdale FSDO for review.

Related reports:

Google
 

Original NASA ASRS Text

Title: A Cessna 310 pilot; fearing engine failure on a hot day; reported entering PHX Class B airspace without a clearance while attempting to trouble shoot a fuel flow anomaly.

Narrative: After takeoff from Falcon Field a right turn was made with a GPS direct Prescott route of flight. Upon reaching 3900 FT I noticed an unusual reading on my Fuel Flow computer. The GPH flow on the left engine had dropped slightly in the climb; as we were about to reach the bottom of the Class B airspace when the fuel flow reading dropped to 11.2 GPH on the left engine. The aircraft had been in maintenance in the past several weeks for a fuel flow check based on a recent Owner Advisory from Cessna. The outside air temperature (OAT) at this point was approximately 90 to 95 degrees and climbing with a forecast high of 114 degrees Fahrenheit. As mentioned; all of a sudden the left engine fuel flow dropped to 11.2 GPH (both engine fuel flows had been reading approximately 23.5 GPH). My location was approximately 8 miles Northwest of Falcon Field with a Class B ceiling of 4000 FT. I was also within ten miles of Scottsdale Airport. I observed the drop for about twenty (20) seconds; and the fuel flow did not improve. I then made the decision to go through a standard diagnostic to determine whether or not I might be facing an emergency shut down of the left engine. Since it was a hot and getting hotter I made the decision to initiate a gentle climb in order to ensure that I had enough altitude in case I had to return to either airport. Climb performance was estimated to be in the 200 FPM range with the elevated temperatures. Falcon is a student training airport with lots of flight activity and Scottsdale; was fairly light in traffic when I left; so I proceeded northwest bound and began my diagnosis. I wanted enough altitude so that if I did have an emergency; I could return to either airport recognizing that at Falcon there would be more traffic - however it was closer at this point. I climbed approximately 600 FT into the Class B airspace - I was not authorized to do so but felt it was key to managing the potential emergency. I did not at this point in time call an emergency for a low fuel flow; nothing of significance had yet happened. I first cross-referenced the Fuel Flow Computer with the standard Analog fuel gauge; which was installed on the co-pilots side. The fuel flow computer read 11.2 GPH and the Analog gage read 21.5 GPH. The fuel flow computer for the right engine read 23.5 GPH and the Analog for the right engine read 22.8 GPH - at this time I felt that further diagnosis was required before taking the next step of either shutting the engine down and/or calling an in-flight emergency. I chose to keep current heading until I could further assess the situation for I still had both airport options with a decision to proceed to Scottsdale if the situation worsened. At this point I had entered the Class B airspace without ATC approval. I did not call ATC; I instead focused on both flying the airplane as well as diagnosing the problem. I planned to call ATC once I had resolved the issue. I proceeded with my diagnosis as follows:1) I immediately checked all EGT's and CHT's made records of the readings; and found the readings from the left engine to be in the same range as the right engine. This I believe ruled out the possibility of an immediate engine failure; however; I wanted to continue to try and understand the reading before I made the decision to return to either airport. If I had been IMC I would have made the immediate decision to return to Falcon Field. 2) I switched the left engine fuel source to AUX (in order to determine whether or not I had a fuel pump failure); and the left fuel flow returned to normal (reading approximately 22.5 GPH). I left the left engine fuel flow configuration in AUX's tank mode for approximately two minutes and all appeared normal. 3) I then switched the left engine fuel source back to main and the computer fuel flow reading was normal. The fuel flow anomaly was no longer present. All three of these diagnostics allowed me to believe that the most likely source of the low fuel flow reading was either a semi-broke wire on the fuel transducer and or a failing transducer. I again check the left engine CHT's and EGT's and found them to be in the same range of the left engine. The aircraft will be sent to maintenance to check the fuel flow transducer. At this point in time I had transitioned to the next step in the Phoenix Class B (6000 FT) and I was under the airspace ceiling. Again; the unauthorized incursion into the Class B airspace was for the sole purpose of getting some additional altitude in case of a left engine failure and having to operating the C310T on a hot day in Phoenix with it single engine performance characteristics. As indicated I had passed into the next ring of the Class B airspace. Recognizing that I had violated the airspace; I had planned to call PHX TRACON upon my arrival in Prescott (provided that I had no further fuel flow problems for I would have immediately returned to Scottsdale). After about six to eight minutes of flight I observed that the fuel flow computer was performing normally. EGT's and CHT's were in line and I made the decision to proceed to Prescott. The rest of the flight was uneventful; both to Prescott; then back to Falcon Field. No further fuel flow glitches were observed. Upon starting to make my approach for the ILS to Runway 21L; Prescott Tower asked me to call Albuquerque Center for a message. ABQ Center asked me to call Phoenix TRACON upon my landing; which I did. Phoenix TRACON told me that I had violated their airspace upon departure; I acknowledged that I did; and explained my reasoning (the full above scenario) regarding the fuel flow issue. They indicated that they would pass on this information to the Scottsdale FSDO for review.

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.