How Low Can We Go?

No matter how badly we want to be on the ground, we have to maintain minimum altitudes on approaches.


Altitude is your friend.” So says a common clich instructors and old-timers pilots drill into their less-experienced contemporaries. The idea-especially when considering failure of a single-engine airplanes powerplant-is greater altitude affords more time to find and glide to a suitable landing area.

But having plenty of altitude isnt always a good thing. Its not a good thing when were on fire, for sure, nor is it a good thing on final to a short runway. In those instances, it can be said we have too much altitude.

Another occasion when we can have too much of a good thing is on an instrument approach in for-real conditions. Approach procedures are predicated on being in such-and-such position at so-and-so altitude, then flying a measured distance, perhaps descending to another altitude, where a runway magically appears through the mist. At least thats what we tell passengers unfamiliar with the concept.

The basic idea of an instrument approach sometimes is misinterpreted, however. We arent trying to get as low as we can; instead, were trying to fly along a prescribed path and altitude, arriving at a point in space from which a relatively normal landing can be made. Too high, and we may not see the runway environment at the right time. Too low, and we may hit something before we have a chance to land on the runway. The latter is far worse than the former.

All of this, of course, presumes our onboard instrumentation is in good working order. Our instrument panels are filled with gauges and dials designed to tell us where we are, how fast were going and how high we are and, usually, theyre accurate. But we check them every two years, whether they need it or not, just to be sure. While its not clear if failing to ensure the 24-month altimeter and static check was performed on this months accident airplane had anything to do with the accident were about to explore, the failure was simply one more link in this events fabled chain.


On January 4, 2007, at 2337 Eastern time, a Cessna 182P collided with trees and the ground while maneuvering during an instrument approach, in the vicinity of the Columbia (S.C.) Metropolitan Airport (CAE). Instrument conditions (IMC) prevailed. The airplane sustained substantial damage; the airline transport pilot and two passengers, one of whom also was a pilot, sustained fatal injuries. The flight originated at Newport News, Va., at 2028.

Earlier, the flight executed a missed approach when trying to land at the nearby Columbia Owens Downtown Airport. Radar data indicate the airplane crossed the final approach fix 500 feet below the published minimum altitude. At 2320, the pilot informed ATC he was executing a missed approach and initiated a right turn instead of executing the published procedure. The approach controls Minimum Safe Altitude Warning alert had activated at 2319, and was presented on the radar display as a recurring “LA,” indicating low altitude. However, ATC did not issue a safety alert.

At 2332, ATC cleared the aircraft for the ILS Runway 11 approach at CAE. Thirty seconds later, ATC vectored the aircraft to rejoin the localizer and, at 2334:47, the flight crossed the ILS approachs final approach fix at 1700 feet, 400 feet low. Radar data included a low altitude alert from this point on the approach throughout the remainder of the flight. No safety alert was issued to the pilot by ATC. At 2334:54, the flight acknowledged an instruction to contact the tower, which never established radio contact. A weather observation taken a few minutes after the accident included wind from 130 degrees at five knots, visibility one quarter of a mile, a ceiling of 200 feet overcast and fog.


The wreckage was located three-quarters of a mile west of the approach end of Runway 11. The crash debris line extended 222 feet. All major aircraft components were found at the crash site. The propeller spinner displayed evidence of rotation and its blades exhibited span-wise scratches. Both wing flaps were found in the retracted position. Fuel was present in both wing-mounted tanks.

The flight instruments were recovered and examined at an FAA-approved facility. Test performed on the altimeter revealed it was within tolerance from -1000 feet to 20,000 feet, except for friction tolerance due to contamination.

The engine was partially disassembled, although no anomalies were found. Fuel was present in the fuel inlet line and in the carburetor bowl. The vacuum pump was removed; its drive coupling was intact. The vacuum pump was disassembled; its vanes and rotor were not damaged.

In its investigation, the NTSB noted FAA instructions to controllers direct them to issue safety alerts to aircraft if they “are aware the aircraft is at an altitude which…places it in unsafe proximity to terrain/obstructions.”


The National Transportation Safety Board determined the probable cause of this accident to include “the pilots failure to follow approach procedures by descending below the prescribed decision height altitude resulting in an in-flight collision with trees and the ground.” And thats the right call. In this case, the NTSB even went further, requesting the FAA to “flight check” the approach; the agency declined.

Although the NTSB attempted to find the out-of-date altimeter as the smoking gun in this accident, the evidence didnt support that conclusion. Although the instrument had not been tested per regulations, it bench-checked fine after the accident. Its unlikely the altimeter was even tangentially at fault.

Meanwhile, its easy to point a finger at ATC for not issuing low-altitude alerts to the pilot. Whether that failure is a cause of this accident depends on the extent to which pilots should place responsibility for their safety in ATCs hands. We tend to discourage transfer of that responsibility.

Instead, were left with little more than two pilots-remember, a fully qualified passenger was aboard-who couldnt begin executing two different approaches at the right altitudes and who wound up in the trees short of an ILS-equipped runway. The controller was of no help whatsoever, of course, but his or her failure to issue low-altitude alerts doesnt absolve the pilots. No matter how low the weather or how badly we want to get home, we still have to observe published minimum altitudes and fly the airplane.


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