Narrative:

I was scheduled to tow a banner around an area before an event. I planned the flight to be 4 hours. The distance from ZZZ to the area is about 35 NM. We fly the banners at 60 KIAS. After accounting for wind; I computed the ground speed to the area from ZZZ airport to be 65 KTS and 55 KTS returning to ZZZ airport from the area. I planned the flight to take 0.54 hours (32.4 mins) to the area; 2.5 hours over the area; and 0.64 hours (38.4 mins) returning to ZZZ. I also added about 0.2 hours (12 mins) to account for banner pick up; and 0.1 hours (6 mins) to drop the banner. All of these times added together; came to 3.97 hours. I rounded the flight time up to 4 hours. I used the cruise performance chart in the FAA approved airplane flight manual supplement for a 180 hp C172N to calculate fuel consumption. Using a power setting of 2300 rpms; at a pressure altitude of 2000 ft; with a temperature of 15 degrees C; fuel consumption rate is stated as being 7.9 gph. Under the same air conditions; the fuel consumption rate at 2200 rpms is stated as 7.2 gph. Being at a pressure altitude closer to 1000 ft; with a higher than standard temperature; and an RPM setting of 2250; I used a fuel consumption rate of 8.1 gph to calculate the amount of fuel required for the flight. I calculated a flight lasting 4.0 hours; with a fuel consumption rate of 8.1 gph; should use 32.4 gals. The C172N; used for this banner flight; has a total of 40 gals of useable fuel on board; as stated in poh. I subtracted 3 gals of usable fuel to allow for taxi; run up; and banner pick up. Using these calculations; I determined I had 37 gals of usable fuel. After a 4.0 hour flight; using 8.1 gph (32.4 gals total); I determined I would have 34 mins (4.6 gals at 8.1 gph fuel consumption) of useable fuel remaining after landing at ZZZ. During preflight procedures I visually checked the amount of fuel in the wing tanks; and found them to be full of fuel. I also found no evidence of fuel leaks. Upon sumping the wing tanks; I also found that the fuel was not contaminated. After I completed preflight procedures; I taxied the airplane to the run up area. I then completed the appropriate run up procedures. I then took off about XA00; and made a traffic pattern to pick up the banner. After picking up the banner; I leaned the fuel-air mixture to peak egt (exhaust gas temperature) and flew to the area. Upon reaching the area; checked the time and noted the actual flight time to be 0.7 hours. The actual flight time agreed with my calculations; 0.2 hours for banner pick up and 0.54 to reach the area. I flew over the area for 2.5 hours; and then started to return to ZZZ airport. After 3.8 hours of total flight time; I experienced engine failure. I immediately dropped the banner; pitched for best glide speed; and searched for a safe place to land. I noted that the median of the interstate was free of obstructions and was straight enough to perform a safe landing. I then performed an emergency approach to landing on the median of the interstate without causing injury; damage to the aircraft or property. By my calculations; I should have had 34 mins of fuel reserve after landing. I attempted to allow for higher fuel consumption due to low altitudes and time used to pick up and drop the banner. I think these events were due to higher fuel consumption than I calculated in my flight planning. This can be prevented by noting the actual fuel burn of the engine; especially when towing banners. Callback conversation with reporter revealed the following information: the FAA has interviewed him about this event but no conclusion has been reached about what action if any will be taken. Reporter believes that he did his best to calculate the fuel on board and the fuel usage for banner towing. The actual fuel consumption determined after the fact was 11.5 gph versus his preflight planned 8.1 gph. No aircraft malfunctions were found other than a carburetor heat box air leak that would have caused a slightly higher than normal fuel usage but not what he experienced.

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Original NASA ASRS Text

Title: A BANNER TOWING C172 LANDED ON A FREEWAY BECAUSE THE ENG QUIT FROM FUEL STARVATION. NO CHARTS WERE AVAILABLE TO CALCULATE BANNER TOWING FUEL USAGE.

Narrative: I WAS SCHEDULED TO TOW A BANNER AROUND AN AREA BEFORE AN EVENT. I PLANNED THE FLT TO BE 4 HRS. THE DISTANCE FROM ZZZ TO THE AREA IS ABOUT 35 NM. WE FLY THE BANNERS AT 60 KIAS. AFTER ACCOUNTING FOR WIND; I COMPUTED THE GND SPD TO THE AREA FROM ZZZ ARPT TO BE 65 KTS AND 55 KTS RETURNING TO ZZZ ARPT FROM THE AREA. I PLANNED THE FLT TO TAKE 0.54 HRS (32.4 MINS) TO THE AREA; 2.5 HRS OVER THE AREA; AND 0.64 HRS (38.4 MINS) RETURNING TO ZZZ. I ALSO ADDED ABOUT 0.2 HRS (12 MINS) TO ACCOUNT FOR BANNER PICK UP; AND 0.1 HRS (6 MINS) TO DROP THE BANNER. ALL OF THESE TIMES ADDED TOGETHER; CAME TO 3.97 HRS. I ROUNDED THE FLT TIME UP TO 4 HRS. I USED THE CRUISE PERFORMANCE CHART IN THE FAA APPROVED AIRPLANE FLT MANUAL SUPPLEMENT FOR A 180 HP C172N TO CALCULATE FUEL CONSUMPTION. USING A PWR SETTING OF 2300 RPMS; AT A PRESSURE ALT OF 2000 FT; WITH A TEMP OF 15 DEGS C; FUEL CONSUMPTION RATE IS STATED AS BEING 7.9 GPH. UNDER THE SAME AIR CONDITIONS; THE FUEL CONSUMPTION RATE AT 2200 RPMS IS STATED AS 7.2 GPH. BEING AT A PRESSURE ALT CLOSER TO 1000 FT; WITH A HIGHER THAN STANDARD TEMP; AND AN RPM SETTING OF 2250; I USED A FUEL CONSUMPTION RATE OF 8.1 GPH TO CALCULATE THE AMOUNT OF FUEL REQUIRED FOR THE FLT. I CALCULATED A FLT LASTING 4.0 HRS; WITH A FUEL CONSUMPTION RATE OF 8.1 GPH; SHOULD USE 32.4 GALS. THE C172N; USED FOR THIS BANNER FLT; HAS A TOTAL OF 40 GALS OF USEABLE FUEL ON BOARD; AS STATED IN POH. I SUBTRACTED 3 GALS OF USABLE FUEL TO ALLOW FOR TAXI; RUN UP; AND BANNER PICK UP. USING THESE CALCULATIONS; I DETERMINED I HAD 37 GALS OF USABLE FUEL. AFTER A 4.0 HR FLT; USING 8.1 GPH (32.4 GALS TOTAL); I DETERMINED I WOULD HAVE 34 MINS (4.6 GALS AT 8.1 GPH FUEL CONSUMPTION) OF USEABLE FUEL REMAINING AFTER LNDG AT ZZZ. DURING PREFLT PROCS I VISUALLY CHKED THE AMOUNT OF FUEL IN THE WING TANKS; AND FOUND THEM TO BE FULL OF FUEL. I ALSO FOUND NO EVIDENCE OF FUEL LEAKS. UPON SUMPING THE WING TANKS; I ALSO FOUND THAT THE FUEL WAS NOT CONTAMINATED. AFTER I COMPLETED PREFLT PROCS; I TAXIED THE AIRPLANE TO THE RUN UP AREA. I THEN COMPLETED THE APPROPRIATE RUN UP PROCS. I THEN TOOK OFF ABOUT XA00; AND MADE A TFC PATTERN TO PICK UP THE BANNER. AFTER PICKING UP THE BANNER; I LEANED THE FUEL-AIR MIXTURE TO PEAK EGT (EXHAUST GAS TEMP) AND FLEW TO THE AREA. UPON REACHING THE AREA; CHKED THE TIME AND NOTED THE ACTUAL FLT TIME TO BE 0.7 HRS. THE ACTUAL FLT TIME AGREED WITH MY CALCULATIONS; 0.2 HRS FOR BANNER PICK UP AND 0.54 TO REACH THE AREA. I FLEW OVER THE AREA FOR 2.5 HRS; AND THEN STARTED TO RETURN TO ZZZ ARPT. AFTER 3.8 HRS OF TOTAL FLT TIME; I EXPERIENCED ENG FAILURE. I IMMEDIATELY DROPPED THE BANNER; PITCHED FOR BEST GLIDE SPD; AND SEARCHED FOR A SAFE PLACE TO LAND. I NOTED THAT THE MEDIAN OF THE INTERSTATE WAS FREE OF OBSTRUCTIONS AND WAS STRAIGHT ENOUGH TO PERFORM A SAFE LNDG. I THEN PERFORMED AN EMER APCH TO LNDG ON THE MEDIAN OF THE INTERSTATE WITHOUT CAUSING INJURY; DAMAGE TO THE ACFT OR PROPERTY. BY MY CALCULATIONS; I SHOULD HAVE HAD 34 MINS OF FUEL RESERVE AFTER LNDG. I ATTEMPTED TO ALLOW FOR HIGHER FUEL CONSUMPTION DUE TO LOW ALTS AND TIME USED TO PICK UP AND DROP THE BANNER. I THINK THESE EVENTS WERE DUE TO HIGHER FUEL CONSUMPTION THAN I CALCULATED IN MY FLT PLANNING. THIS CAN BE PREVENTED BY NOTING THE ACTUAL FUEL BURN OF THE ENG; ESPECIALLY WHEN TOWING BANNERS. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE FAA HAS INTERVIEWED HIM ABOUT THIS EVENT BUT NO CONCLUSION HAS BEEN REACHED ABOUT WHAT ACTION IF ANY WILL BE TAKEN. RPTR BELIEVES THAT HE DID HIS BEST TO CALCULATE THE FUEL ON BOARD AND THE FUEL USAGE FOR BANNER TOWING. THE ACTUAL FUEL CONSUMPTION DETERMINED AFTER THE FACT WAS 11.5 GPH VERSUS HIS PREFLT PLANNED 8.1 GPH. NO ACFT MALFUNCTIONS WERE FOUND OTHER THAN A CARB HEAT BOX AIR LEAK THAT WOULD HAVE CAUSED A SLIGHTLY HIGHER THAN NORMAL FUEL USAGE BUT NOT WHAT HE EXPERIENCED.

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.