Known Deficiency


Ensuring the aircraft were about to fly is adequate for the mission is one of the reasons we perform preflight inspections. During such inspections, well occasionally find something amiss. Depending on what it is, whether the problem can be remedied before takeoff and the mission, we may decide to depart without it. (The legality of taking off without all equipment functioning is discussed in the article beginning on page 12 of this issue.)

Owners tend to know their rides better than a renter knows the airplane he or she has been assigned. We might know, for example, a gentle tap on the oil pressure gauge will awaken it, the landing light has burned out again or the number two comm always has a problem with certain frequencies. These kinds of issues dont really impact flight safety. Others, however, can and do.

For example, owners also know if a fuel gauge is sluggish or the magnetic compass is 20 degrees off and needs adjustment. Depending on the airplanes other equipment-a fuel totalizer in the case of the sluggish gauge, or a directional gyro when considering the compass-we may be perfectly content to launch with the balky equipment.

Putting aside the legality of operating an aircraft with known equipment deficiencies, the point is we can reasonably expect to complete a half-hour flight with a defective fuel gauge if we visually verify sufficient fuel is in the tank, or use the directional gyro-perhaps in concert with a panel-mounted GPS-instead of the magnetic compass to find a nearby airport to which weve flown many times before and with which were very familiar.

With some aircraft and proposed operations, however, taking off with a bad compass isnt a good idea. Similarly, if the aircrafts configuration prevents visually inspecting and confirming its fuel quantity, we may need to have the indicating system repaired before further flight. If we dont, we could be forced to turn around shortly after takeoff and wind up in the weeds short of the departure runway.


On May 25, 2009, at 0846 Eastern time, an Aero Commander 500S was substantially damaged following a loss of engine power and collision with terrain during a forced landing shortly after takeoff from the Daytona Beach (Fla.) International Airport. The private pilot was seriously injured and the pilot-rated passenger was killed. Visual conditions prevailed.

About one minute after takeoff, the pilot reported “an engine failure” and announced his intention to return for landing. Witnesses reported the accident airplanes operating engine was “surging” and “revving” and would then “conk out” before revving up again. As the engine surged, the airplane would “shuffle left and right.”

In a written statement, the pilot later described performing a “full” preflight inspection of the airplane, and that the fuel gauge read 110 gallons. He stated, “We lost both engines shortly after takeoff, the engines surged from full throttle to idle.” The pilot maneuvered the airplane onto a left base traffic pattern leg to land in the direction opposite his takeoff, and felt he “had the field made.” As the airplane descended towards the runway, the pilot prepared for a “normal” landing, and “dropped the gear and gave it full flaps when I felt I had the runway made.” The 1470-hour pilot stated he had “no recollection of the airplane stalling or the impact….”


All major aircraft components were accounted for at the accident site. There was no odor of fuel. The airplane came to rest on flat, grassy terrain on airport property, 267 feet prior to the approach end of the opposite, departure runway.

Examination of the cockpit revealed the left and right fuel valve switches and the left and right fuel boost switches were in the “on” position. Both magneto switches were in the “both” position. The floor panels were opened, and flight control cable continuity was confirmed from the cockpit to all flight control surfaces. Examination revealed the landing gear were in the down and locked position, and the flaps were deployed.

The left engines main fuel inlet line to the engine-driven fuel pump was disconnected, and three drops of fuel were collected. The fuel and the line were absent of water and debris. No fuel was collected from the right engine. Its fuel pump and the line were absent of water and debris.

The airplanes fuel system had a capacity of 226 gallons. It was serviced through a single port on top of the left wing, and the tanks were interconnected to a center fuel sump that fed both engines. The fuel cells were opened through access panels; each was intact and contained only trace amounts of fuel. The airplane was leveled, the drain petcock was opened at the center fuel cell sump and one quart of fuel was drained. The sample contained trace amounts of sediment and water.

On April 1, 2009, maintenance was performed on the airplane to diagnose a fuel quantity indication problem. A replacement gauge was installed, but the problem persisted. After the accident, the mechanic told investigators he recommended further troubleshooting and repair of the airplane, but that it would require defueling the airplane. On that occasion and in subsequent discussions, the pilot stated he would prefer to “wait until the quantity was reduced through use of the airplane” rather than have the mechanic defuel the airplane.

The airplane was originally delivered with Lycoming IO-540 engines. In 1978, Lycoming IO-720 engines with twin turbochargers were installed.

Probable Cause

The National Transportation Safety Board determined the probable cause of this accident to include “a total loss of engine power due to fuel exhaustion as a result of the pilots inadequate preflight inspection.”

Basically, the pilot took off in an airplane with a deficient fuel-quanity indicating system, the tank configuration of which prevents visually confirming whether an adequate quantity was aboard. This deficiency had been known for a year or so but had not been repaired.

Its one thing to bounce around in a Cherokee with a bad fuel gauge: We can visually check fuel quantity quite easily by simply removing the filler cap. On more-sophisticated aircraft, including those with single-point refueling ports like this one, the exercise becomes more problematic. However, in both situations, going to the trouble to top off the tanks-or at least add enough fuel for the mission, plus reserves-cures a multitude of sins.


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