Almost 20 years ago, I rode coach from JFK to Osaka, Japan on a Northwest Airlines 747-400. Taking my time in deplaning, I managed to sneak a peek at its cockpit and chat briefly with the crew. I was astonished to learn the airplane weighed nearly 900,000 lbs at takeoff, close to or at its maximum gross, and burned almost half that weight in fuel before landing. I can presume the airplanes handling characteristics at takeoff versus landing. While transport pilots routinely operate at maximum weight, the rest of us rarely do. So, on our first gross-weight takeoff in, say, 10 years, the airplanes desire to roll farther and climb more slowly than were accustomed can be an eye-opener. Ive written previously in these pages about how my airplanes FAA-approved maximum gross weight is 250 pounds heavier than its manufacturer intended, thanks to wingtip fuel tanks installed pursuant to a supplemental type certificate (STC). That STC comes with various paperwork, but does not include revised performance charts showing expected takeoff or climb performance. From experience, I know a climb at the higher gross weight requires patience. Not everyone regularly flies their airplane at its gross weight, with or without paperwork allowing heavier takeoffs. If they did, theyd understand more about the substantial hit performance can take. Heres an example of what Im talking about. Background On September 1, 2007, at about 1033 Eastern time, a Beech A36 Bonanza impacted upsloping terrain near Elizabethton, Tenn. Visual conditions prevailed. The flight originated about 1029, from the Elizabethton Municipal Airport (0A9), and was destined for the Virginia Highlands Airport (VJ1) in Abingdon, Va., about 20 nm away. The field elevation at 0A9 is 1593 feet msl; mountains rising to 4321 feet msl exist between the two airports. The airplane was destroyed; the commercial pilot and four passengers were killed. Witnesses reported the airplane landed on 0A9s Runway 6 (4529 feet long and 70 feet wide) at approximately 1001, taxied to the south side of the airport, and without securing the engine, boarded two waiting passengers. The airplane was then observed taxiing towards the approach end of Runway 24, but turned around and taxied to Runway 6, due to an airplane that was being towed on the taxiway at the time. A pilot-rated witness reported the airplane became airborne when it was two-thirds down the runway. The witness reported the airplane did not appear to be climbing very well but continued on runway heading. Another pilot-rated witness located approximately 1500 feet beyond the runways departure end reported the airplane flew 200 yards behind his house at between 75 and 100 feet agl, or “exceptionally low.” The airplane was in a steep climb attitude, flying slowly. A third witness about a mile from the accident site observed the airplane for two seconds when it flew past a clearing. He estimated its altitude at 200-250 feet agl. There were no known witnesses to the crash; the pilot did not establish contact with any ATC facility during the accident flight. Investigation The airplane crashed in a wooded and mountainous area at an elevation of 3400 feet msl. The main wreckage was located approximately 5.38 miles northeast of the departure end of Runway 6. The cockpit, cabin and inboard sections of both wings were consumed by a post-crash fire. No evidence of pre-impact failure or malfunction was noted to the engine, airframe or flight control systems. The propeller exhibited signs of being under power at impact. Since the airplanes last refueling the day before, it had flown six legs totaling approximately 343 nm. The NTSB did not determine how much fuel was aboard, noting only a manufacturers limitation that each flight must begin with no less than 13 gallons in each main fuel tank, for a total minimum of 26 gallons of fuel. Using that minimum fuel load, the NTSB calculated the airplanes gross weight to be approximately 3798 pounds, with the CG 88.65 inches aft of datum. Any fuel weight in the airplanes main fuel tanks above the minimum required for the flight would increase the gross weight but would move the CG forward. The airplanes maximum gross takeoff weight was 3833 pounds. At that weight, the aft CG limit is +87.7 inches aft of datum. The NTSB concluded the airplane was almost an inch beyond its aft CG limit. Probable Cause The National Transportation Safety Board (NTSB) determined the probable cause of this accident to include “The poor in-flight planning by the pilot-in-command for flying towards rising terrain with inadequate clearance.” The accident airplane carried a pair of wingtip-mounted fuel tanks installed under the same STC as the tanks on my airplane. Starting with full tanks, and then flying six legs of “only” 343 nm while employing common mixture leaning techniques, would result in approximately half a full load of fuel remaining. Those 30 or so gallons beyond what the NTSB calculated was the minimum aboard would mean the accident airplane was around 145 pounds overgross, instead of 35 pounds under it. Also, the CG would move forward-perhaps to within the envelope, perhaps not. Well never know the airplanes true weight and balance situation, nor the pilots awareness of its loading, before takeoff. What we do know, however is the airplane exhibited signs of being overweight: It used lots of runway for takeoff and had difficulty climbing. Some of the reason for the climb difficulties could involve a high angle of attack, as indicated by one of the witnesses, resulting from the heavy, aft-CG loading. In such an attitude, the only way to increase the climb rate could have been lowering the nose to accelerate and-once a higher speed was achieved-using it to climb. That said, the airplane climbed almost 1800 feet in approximately four minutes, averaging 450 fpm. Its sea level, gross weight rate of climb is published as 1210 fpm. The real question, though, is why the pilot didnt turn away from the looming mountains. The weather observed at 0A9 37 minutes before the accident included nine miles visibility-almost halfway to the destination-and clear skies. Performing two standard-rate, 360-deg. turns, even at a reduced climb rate of, say, 300 fpm, before attempting to cross the mountains would have gained 1200 feet, allowing the airplane to clear the highest terrain by at least 200 feet.
