Aviation is full of mysteries. Perhaps rooted in reality, they take on an almost mythical air about them. Pilots know they are true, without being able to justify that position and without really knowing where that knowledge came from.
The downwind turn, operating lean of peak and flying on the step have all been part of that aviation lore – and in fact may be so still for some pilots.
The fact is that many pilots treat their airplanes like its a complex remote control for a big screen TV. They know only enough about its operation to meet their anticipated daily needs. Instead of studying the book on the airplane and engine, they put their effort into learning to fly instrument approaches and working that fancy moving map. Noble goals, both, but such pilots can lose sight of whats really keeping them in the air.
New airplanes come with operating manuals for the airplane, engine and each instrument installed. Each manual is published by the manufacturer of that device, although the airframe manufacturers book typically includes some information from other companies products pertinent to the operation of that specific airplane.
After several owners, however, the materials usually begin to disappear. The published operating instructions for the Stormscope become a photocopy, which eventually is missing the last five pages. The quick guide to the GPS is dutifully tucked into the binder that holds the operating handbook, but the more complete book lives with a previous owner or one-time renter. And the engine manual is forgotten, replaced by the performance tables and the various checklists incorporated into the POH.
Pilots then learn about their airplanes through trial and error, word of mouth, and the instructions from well-meaning mechanics and instructors who just might be wrong about the details.
Consider the final flight of a Cessna P210 that was flying from a suburb of Dallas to Spicewood, Texas. The aircraft departed at about 10:40 a.m. for a flight that would take about an hour. Aboard the airplane were the 69-year-old pilot and a passenger.
The pilot had friends who lived adjacent to the airport and had visited them on at least four other occasions. One witness said that, on past visits, the pilot had to make go-arounds on at least three occasions because of high airspeed on final approach.
Witnesses said that on this particular day the airplane approached the airport from the west at a high rate of speed with the gear already down. It crossed the runway at about mid-field and turned onto a left downwind for runway 17, a 3,900-foot paved runway that is 30 feet wide. At about 20 feet, and still fast, the airplane flared and ballooned to about 50-60 feet.
The airplane slowed as it continued down the runway at about 50 feet, with 30 degrees of flaps and the engine producing little or no power. As the airplane slowed, witnesses said its angle of attack grew increasingly nose-high. After traveling about two-thirds of the length of the runway, the pilot apparently applied partial power and the Cessna climbed to about 200 feet and turned to the right.
The turn was described as uncoordinated, with the airplane flying in slow motion.
With the gear and flaps hanging out in the wind and the engine not producing full power, the airplane refused to climb. He turned to the north, perhaps making right traffic for another approach, and briefly leveled off at a low altitude.
As the witnesses watched, the airplane stalled and descended toward the trees. About two or three seconds before impact, the engine was heard to rev to full power but the airplane crashed into trees at the edge of a creek and burst into flames. Both occupants were killed.
The pilot had owned the airplane for several years, logging nearly 300 of his 550 hours in it. His logbook contained an endorsement for the instrument rating dated 16 months before the accident, but he had never taken the instrument checkride.
The First Problem
The pilots repeated high-speed approaches into the airport illustrate a common aviation illusion. The pilots home base, Redbird Airport, features two runways that are each 150 feet wide. The main runway is 6,451 feet long; the other is 3,800 feet long. Flying into a narrow runway such as Spicewood, particularly one that is shorter than what youre used to, gives you the illusion youre higher than you are.
Pilots can respond to being high in two ways. Some will reduce power and slow down, eventually stalling or landing short of the runway threshold. Others will dive toward the runway, trying to descend quickly without considering the energy theyre storing in the form of airspeed.
This pilot may have responded to the illusion by thinking he had more time to bleed off energy than he did. He may have planned his initial descent poorly, arriving at pattern altitude with excessive airspeed in the first place. He may also have responded to the visual illusion that the airport was more distant than he thought by keeping his speed high for longer than necessary.
In either case, the end result was a long float with poor airspeed control. The pilots decision to go around was a correct one, but came only after the airplane had adopted an extreme nose-high attitude.
He compounded the problem by executing the go-around improperly. The Cessna POH stipulates applying full power, retracting flaps to 20 degrees, pitching to climb speed of 70 knots and then retracting the flaps completely and accelerating further.
While the go-around is one of the least-practiced maneuvers in light airplanes, this accident underscores the importance of being ready to make a quick decision and properly perform the maneuver. But there was one other complicating factor that put the outcome of a successful go-around in doubt.
One of the witnesses, a friend of the pilot who had flown with the pilot in the accident airplane six days earlier, said, He told me to be careful how much throttle I give it because he had just gotten an overhaul and the mechanic had told him not to give it over so many inches of manifold pressure until it got broken in.
The Second Problem
A review of the aircrafts maintenance record showed that all six cylinders had been replaced at the previous annual inspection six months and 26 flight hours earlier – at which time the airplane had just over 2,500 hours on it. Prior to that top overhaul, the engine had also had all six cylinders replaced five years and 400 hours earlier. Investigators also determined the airplane was for sale, although the reasons for the potential sale were not outlined in their report.
Clearly the Cessnas turbocharged Continental TSIO-520 had a troubled history. The engine had also been overhauled at 1,000 hours total time. A major overhaul and two top overhauls in 2,500 hours is hardly standard procedure, even for the hardworking engine on a pressurized single. (The manufacturers recommended TBO is 1,400 hours.)
This history may have been enough to make the pilot/owner think about ways to minimize wear on his engine. He had also told the witness to limit manifold pressure until the engine was broken in.
The source of that information apparently was traced to an overhaul manual supplement provided when the first top overhaul was done in 1994. The Ram Aircraft Corp. cylinder work included a set of break-in procedures that called for limiting power output to 30 inches of manifold pressure and 2,700 rpm. It allows use of full power, 36.5 inches and 2,700 rpm, in the case of emergency.
Whether these specific guidelines were what the pilot was using to set power is unknown. If they were, however, the pilot obviously missed the part where the manual said the break-in procedure was necessary for the first flight, which the company recommended to be two hours.
With 26 hours since the top overhaul, most engine experts would agree the new parts were broken in. Some aviation folklore, however, says break-in may take 25 or even 50 hours to be complete, although neither Continental nor Lycoming recommend it currently.
Even more insidious is the notion that partial-power takeoffs prevent abuse to an engine. For someone wanting to sell an airplane, avoiding additional maintenance expense takes on a fairly high priority.
But partial power takeoffs are harder on an engine than full-power takeoffs. That may be somewhat counterintuitive, but a look at how the engine works makes the truth of the statement obvious.
Air-cooled piston engines depend on excess fuel to cool them when the airplane is flying slowly, as during takeoff. The mechanics of the system vary from engine to engine, but all work essentially the same way. Advancing the throttle to full power does more than open the throttle. It also allows extra fuel to enter the cylinders – fuel thats not burned to produce power but instead merely cools the cylinders.
An airplane equipped with a fuel flow meter will demonstrate this conclusively. At nearly full throttle, the engine will be producing its maximum rated power. Advance the throttle to the stop and fuel flow will increase but the engine will not produce additional power. Instead, cylinder head temperatures will go down.
The pilots logbook was burned in the post-crash fire, so his most recent instruction or flight review in the airplane is unknown. But one cannot fault an instructor for an owners improper operation of an airplane.
Knowing your airplane means relying on authoritative information rather than rules of thumb or common knowledge. The price of misinformation can be high – even when the pilot thinks hes being conservative and conscientious.
-by Ken Ibold