Unfortunately, there are more occurrences than there should be of pilots not diverting to alternates when it should have been obvious that it was necessary. Too often, airplanes hit the ground just short of their destination. The only blessing is that there's little chance of a fire since there's usually no fuel left in the tanks.
The rules that define fuel requirements are ridiculous. If you think planning a flight to land with 30 minutes of fuel remaining (45 minutes at night) at your destination is wise, then chances are pretty good you're going to make a lot of flights with an uncomfortable level of anxiety as you approach your destination.
Assuming that everything is going to go as planned is a gamble. Any number of things can cause a delay or the need to go to an alternate airport. Deviating for weather, stronger winds than forecast, an airshow in progress at your destination (I know you normally check the notams), a disabled airplane on the runway and a TFR (temporary flight restriction area) can require some quick calculations of remaining fuel.
The accident records are replete with pilots who were surprised when their engines sputtered and died. Typically, the accident site is within five miles or so of the destination airport and the pilot blithely flew over several airports on his way to the power-off landing.
One of several recent "confessions" to the Aviation Safety Reporting System (ASRS) should serve as vivid object lessons: "The planned flight time was 3.2 hours. There were 24 gallons of usable fuel on board. Expected fuel burn was 4.8 gph. There should have been enough fuel for 5 hours. The fuel was exhausted after 3.7 hours. Fuel burn data was established a year and a half previously when using aggressive leaning at all times and at relatively low power settings. Three weeks prior to the flight in question, the A&P mechanic performing the annual inspection advised the pilot that excessive leaning was harmful to the engine and suggested that it should not be leaned unless above 5,000 feet msl. The flight in question was conducted at 5,000 feet msl. In addition, the pilot began using higher power settings, believing this was desirable for this engine."
I'm surprised at the mechanic's recommendation of not leaning below 5,000 feet. The 5,000-foot rule is designed to protect an engine. If the mixture is leaned and the pilot calls for full power-at altitudes where the engine can achieve high power - there can be damage to the engine. At 5,000 feet, most normally aspirated piston engines can't produce more than about 75 percent of power, so manhandling the throttle won't cause a problem. But there's no reason not to lean an engine at altitudes lower than 5,000 feet as long as it's enriched before the throttle is advanced to call for full power, as in a go-around. If you do find yourself running low on fuel, it's important to alert the controller to your problem. You have two options. You can advise that you are "minimum fuel," or you can declare an emergency. If you declare "minimum fuel," air traffic control has no obligation to give you priority handling. "Minimum fuel" means that your fuel supply has dwindled to a level where you can't accept any undue delays. If you need priority handling, declare an emergency and let the controller know how many minutes of fuel you think you have remaining. The paperwork for declaring an emergency is nothing compared to that required if you run out of fuel.
Flying VFR, you get to choose your altitude - providing you can stay clear of clouds - and that can have a lot to do with your fuel endurance. As a general rule, when heading west you might want to fly lower than heading east in order to avoid stronger head winds. Flight planning will have given you a good idea of the forecast winds at different altitudes and your en route calculations will confirm the wind speed. Flying at higher altitudes often means a smoother ride. If your schedule allows it, you'll want to fly west in the morning and east in the evening to avoid flying into the sun.
Well out from your destination you should listen for the automatic weather reporting system or for other pilots announcing their positions in the pattern. From the ATIS/AWOS/ASOS or Unicom you'll have a good idea of which runway is being used. If you hear someone call, "Downwind for Runway 3, full stop," that's a good indication that Runway 3 is the active runway and there's no reason for you to call in and ask, "Which way are you landing?"
