Getting To Know You
Introducing Yourself To The AirplaneEvery airplane has its own personality, and pilots who have flown "identical" makes and models know that some machines were born to fly. Others do the job without flair, and a few ought to be sent back to the factory for an attitude adjustment. Just as it takes time to get to know people, the same can be said for aircraft. When forming new aircraft relationships, it is best to be conservative until you see how things are going to work out. And that perspective should be passed on to your students.
At our flight school, NXX34S (numbers changed to protect the guilty) flew somewhat sideways. It was consistently five knots slower than any other Cessna 150 and was nicknamed 34 Suicide because of its climb performance from short fields. It was a great airplane for stall practice because you didn't have to wait long for it to slow down, and if the student needed to log cross-country hours, Suicide was your ride.
NXX89 Joker did everything well and must have come off the assembly line mid-week after bonuses were given out. She was spectacular. Everyone tried to get the Joker first.
NXX467 flew well enough but was no lady. She had a nasty little habit of dropping the left wing in a departure stall. This airplane was practically guaranteed to spin if the student was not quick with his or her feet, and it was completely intolerant of any indiscretion in coordination. It also burned just a bit more fuel than the other 150s. On student cross-countries this was never an issue because we always allowed for fuel to get to the destination, a little unscheduled "sightseeing" to get reoriented, and a very healthy reserve. However, when our students graduated or a new pilot came to check out, we might advise them of 467's thirstiness. It consumed only about 0.5 to 0.7 gallons per hour more than the others, but this was noticeable after a long trip. The mechanics were never able to get it to exactly match the specs in the pilot's operating handbook, and the engine ran just fine otherwise.
Even a brand-new aircraft on its flight from the factory is deserving of some consideration until pilot and machine reach an understanding. A Piper PA-28-81 was picked up at the factory in Vero Beach. The new owner flew to Lakeland, Florida, where the aircraft was fueled with 13 gallons for a computed burn rate of 11.8 gallons per hour. According to the pilot, he visually verified full tanks on both sides and then flew with relatives for a total of 0.5 hours with an ending Hobbs reading of 12.9 hours.
The pilot calculated the distance to the next fuel stop as 344 nautical miles. "At about 120 knots per hour average, I calculated that I would need about 2.9 hours of fuel. Adding the 0.5 hours of flight the night before yielded about 3.4 hours of fuel required. At 12 gallons per hour, that would require 40.8 gallons of fuel, which would leave a reserve of 7.2 gallons (more than the required one-half hour)." The PA-28-181 had a usable fuel capacity of 48 gallons.
The flight was cruising between 1,500 and 3,000 feet when the engine lost power. The pilot switched fuel tanks, but the engine did not respond. He tried to land in a field, went under some wires, bounced over a road, and the right wing struck the ground. The pilot was uninjured but the aircraft sustained substantial damage.
During the investigation, the pilot said he made a restroom stop at Valdosta, Georgia. He told the investigator that the Hobbs meter read 12.4 hours when he added 13 gallons at Lakeland. This added 0.5 hours to the flight time stated in the accident report. The Hobbs meter showed 16.2 hours for a total of 3.8 hours since the last refueling. Less than a gallon of fuel was found on board the aircraft, and there were no signs of spilled fuel. At 3.8 hours and 48 gallons used, the calculated burn rate was 12.63 gallons of fuel per hour. That burn rate, multiplied by 3.8 hours, equals 47.99 gallons of fuel - exactly the useable fuel on board.
The POH predicts the engine will use 10.5 gallons per hour in cruise when properly leaned, and a brand-new engine might burn slightly more. If the mixture is not leaned, fuel burn will be much higher. The charts also predict that cruise speed at 2,000 feet will be about 114 kt. This is slower than the pilot's estimate. An additional takeoff, such as when the pilot made his pit stop, will add to fuel burn. The half-hour discrepancy in the pilot's recollection of the Hobbs time would have made a difference. The tanks may not have been completely full. It's easy to miss a couple of gallons when eyeballing. While we're taught to be suspicious of fuel gauges, if they show close to empty, believe it unless you know they are in error. This pilot couldn't have known that because he was just getting acquainted with the aircraft.
At the AOPA Air Safety Foundation, we recommend that flights be on the ground with one hour reserve, and that is after you get to know the aircraft's actual fuel consumption. Yes, you will make more fuel stops with the resulting inconvenience and delay, but all of them, added up over a lifetime of flying, won't begin to equal the inconvenience of a single fuel-exhaustion accident. There are multiple causes that subtract from real-world reserves. In retrospect, the pilot probably wishes he had gotten to know this new airplane better. Like people, they're all a little different.
Bruce Landsberg is executive director of the AOPA Air Safety Foundation.
By Bruce Landsberg