The medical supplies arrive and you are briefed to keep the cabin temperature cool because the supplies need to be kept cold, but that they should not be allowed to freeze. This doesnít seem like a problem since the small heater in the nose of the aircraft seldom heats up the drafty cabin very much. You hop in the aircraft just after sunset, suddenly aware that you missed lunch, and donít have any food along for this trip. But the excitement of a good trip in the left seat of the Navajo makes you forget about this issue and you start up, do a quick run-up, pick up your clearance, and in no time you are airborne.
Once you are airborne, you are cleared to 14 000 ft. Through 10 000 ft, you put on the oxygen mask and turn on the valve. You note the time, so that you can track consumption of oxygen, because you donít want to run out on the way home. At 14 000 ft, you level off and lean the engine according to the companyís policies till the exhaust gas temperature (EGT) is 50į rich of peak. You note that this gives you a fuel flow of 18 gph on each side, for a total consumption of 36 gph. This is 4 gph higher than you had planned, but it doesnít create too much concern for you because you are carrying plenty of reserve fuel. What causes much more concern is the fact that within minutes of levelling off, the heater quits working, and the temperature drops quickly. You are concerned because you donít want the medical supplies to freeze. You are concerned because you donít want to freeze. You are concerned because the heater supplies the heat for the windshield, and if you pick up a little rime ice on descent, it may obstruct your vision. You decide to leave the heater on, so that cold air will blow over the windshield, in the hope that this will somehow keep it clear.
The rest of the flight is very cold, but uneventful. You do pick up some rime ice on the descent, but it clears off of the windshield long before you are in position to land. After landing, you are greeted by an ambulance that has arrived from the hospital to pick up the medical supplies. You are relieved to find that nothing is frozen (other than your toes), and you feel good about a job well done. After the ambulance leaves, you are left completely alone on the dark ramp, and wonder what you should do. You are very cold and hungry, but the airport is deserted and everything is locked up. You recall that the heater has a button on it that can sometimes pop out and cause the heater to fail. You are tempted to try to find that button and reset it.
Now you start thinking about the return flight. The oxygen tank is down to 40 percent. You were on oxygen for 35 min and had used 10 percent of the tank. You should need roughly the same amount of oxygen for the return flight, so there should be plenty of oxygen. The main fuel tank gauges are reading exactly half full, with the auxiliary tanks still untouched, and still reading more than half full. In spite of the higher fuel flow indication, the gauges indicate that you have used exactly the amount of fuel that you had planned. You decide that the fuel flow gauges must be over reading. You realize that you forgot to use any fuel from the auxiliary tanks on the way up because you were distracted by the broken heater.
What do you do now?
off the panel for the heater and see if you can reset the button. This way you might have some heat for the return flight.
There is nothing to do except get in the airplane and fly home. It will be a cold flight, but you are not a maintenance technician and you donít want to fool around with something you arenít sure about.
Take a cab into town, find a hotel room for the night and return in the morning after getting some advice from the maintenance people about the heater and the higher fuel flow. Right now you are cold and hungry, and in no shape for the return flight.