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View Diary: How Airliners Work - Weight and Balance (160 comments)

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  •  On 9/1/2007, a Beech A36 stopped at (16+ / 0-)

    Elizabethton, TN (0A9) and picked up a fourth passenger. That made five people on board.  All the passengers were, according to witnesses who saw them at the FBO, rather portly.  The  pilot weighed 200 pounds at his last medical. The total weight of the four passengers was 780 pounds. Items recovered were included in the calculations. The NTSB calculated takeoff weight was 3,798 pounds.  The center of gravity was 88.65 inches aft of datum.

    According to Beechcraft, the maximum takeoff weight is 3,833 pounds, and at that weight, the aft CG limit is +87.7 inches aft of datum.

    0A9 is at 1,593 feet elevation MSL. Temperature at the time was about 74 degrees.  The airport is in a valley, with mountains on both sides. A local pilot was hiking on Holston Mountain and saw the plane go by well below him. He said it appeared to be struggling, nose high attitude trying to climb and not climbing well at all.  They eventually impacted Holston Mountain at 3,400 feet MSL a little more than five miles from the airport.

    Weight and balance. Don't leave home without it, not to mention calculating density altitude.  

    Rudeness is a weak imitation of strength. - Eric Hoffer

    by Otteray Scribe on Tue May 07, 2013 at 04:03:00 PM PDT

    •  35 lbs, 1 inch (5+ / 0-)

      but they couldn't climb 1800 feet  in 25,000 feet of ground track.?

      sounds like they might have had a power problem?

      of course with that aft CG condition, they may have been holding so much forward elevator, that the control drag was just killing them.

      •  I think there was more than just a power problem. (6+ / 0-)

        The NTSB said the ambient temperature from the automated wx station was 74 degrees, but I was two miles from the airport that day, at about that same time, and the outside air temperature on my Jeep was showing 91 degrees. Visibility was reported to be nine miles. You could see the outlines of mountains nine miles away, but it was hazy. I don't know the relative humidity that day, but it seemed higher than we are used to around here.

        Several pilots watched him taxi out and take off, but no one saw or heard him run up the engine or check the mags and prop.

        Rudeness is a weak imitation of strength. - Eric Hoffer

        by Otteray Scribe on Tue May 07, 2013 at 05:44:26 PM PDT

        [ Parent ]

        •  now that's a problem (2+ / 0-)
          Recommended by:
          ER Doc, Otteray Scribe

          adds an extra 3,000 feet but still

          they might have had a dead cylinder or contaminated fuel

        •  And they couldn't circle?! (2+ / 0-)
          Recommended by:
          ER Doc, Otteray Scribe

          It sounds like the pilot probably didn't lean the engine out, either. That matters more at high altitude and/or when the humidity is high.

          It took a lot of mistakes to fly into that mountain there.

          Two friends of mine witnessed an amusing incident at the field I learned at. A large hispanic family drove up to the airport (Meadowlake Airport, near Colorado Springs), got out of their station wagon, and climbed into a Piper Cherokee 6. Lots of fussing and squeezing and putting stuff in and out. Finally everyone managed to get in, they closed the door, and the plane slowly, ever so slowly sat back onto its tail.

          Everyone then got out of the plane, several persons got back in the car, and with a bunch more fussing around, some left in the car and some left in the airplane. The plane was apparently still very heavily loaded (and the airport there is at 6,880' MSL), because although it took off, it had a very flat climbout to the south (where fortunately the terrain descends all the way down to Pueblo).

          •  There were several things that did not add up. (3+ / 0-)

            They listed the total weight of the four passengers as 780 pounds, but the guys who saw them all get out and shake hands greeting the fellow they picked u,p described them all as "widebodies."  and the 780 pounds may be conservative. When bodies are weighed at the morgue, they have no way of accounting for missing parts and blood loss.  Bunch of Baptist preachers, they said. Circling is not an option when you have  a 4,500 foot mountain at your left elbow. and you are climbing out through a valley. One pilot saw them go past his house at probably no more than 100-150 feet higher than the trees. When the sectional says "rapidly rising terrain", it means it.  I am wondering about  plug fouling also. The NTSB report said that when he parked on the ramp to pick up the passenger, he did not "secure the engine,"  then did not run it up and check the mags, according to witnesses.  

            So, we have a situation of inadequate preflight, over gross, hot humid day. Mountain airport. What could possibly go wrong?  As you know, winds in the mountains can be unpredictable, especially if you run into downslope wind as Steve Fossett appears to have done.

            The photo at the link gives an idea of what the departure route looked like. Photo is small, so you will have to zoom in.
            http://flightwise.com/...

            Rudeness is a weak imitation of strength. - Eric Hoffer

            by Otteray Scribe on Wed May 08, 2013 at 05:48:45 AM PDT

            [ Parent ]

            •  ... (2+ / 0-)
              Recommended by:
              Otteray Scribe, RiveroftheWest

              I've flown in and out of that airport several times, although not as pilot. I've also done missed approaches there in bad weather as an airline PAX.

              At altitude (where I learned...), plug fouling is real and problematic. I learned to lean for taxi, and even so spent more than a little time leaning to reduce fouling during and after run-up.

              One of the few times I truly scared myself was in a C-172 at Meadowlake Airport (6,880') at the short crosswind runway, launching to the east. (That runway is now gone; at the time they were rebuilding the main runway.) I had one passenger, forgot to lean the engine, and one of my co-owners had filled the tank, against club rules. So I was very heavy (still well under gross, but quite heavy for high altitude). It was morning, and fairly cool (~50F).

              Forgetting to lean made the difference between clearing the telephone wires near the end of the runway and flying under them...

      •  ... (0+ / 0-)

        You really don't want to push the rear CG limit, either. As Major Kong notes, that way lies pitch divergence, and soon after uncontrollability.

        Further, as planes age, especially small planes, they tend to accumulate more weight (dust bunnies, paint, ...) behind the c/g than in front. Sometimes the actual c/g is substantially aft of the computed c/g, and this has resulted in fatalities. :-(

    •  Sometimes weight and balance is blamed (0+ / 0-)

      when something else goes wrong. There was a horrible crash in PA back in the '70s, when my ex was working at Piper, and around five VIPs from the state government were killed. You know things are bad when you go to pick up your spouse from work, quitting time comes, and no one leaves the building.
      It was a difficult investigation because the plane was pretty well destroyed. Initially it was blamed on pilot error calculating balance because the passengers were fat cats in every sense of the term. The engineers breathed a sigh of relief until closer examination found that the flaps had split meaning one was down and one retracted causing the plane to flip. My ex was convinced it was an electrical fault, as was his way, but in the end, due to some invaluable input from a corporate pilot who was also a pretty good mechanic, he found that the case hardness on the gears in the flap transmissions were not what they should have been. One tooth would break off and, if it was right after an inspection, no one would notice until the airplane was under stress and three or four more teeth would strip.
      That little problem took about six months to solve, and would have taken a lot longer. Piper management did its best to keep that pilot from cruising his aircraft into the engineering hangar whenever he dropped by Lock Haven. Eventually he had a lightning strike and during the inspection following that, the wonky gear was found. Enough further inspections in the field proved it.
      Piper would have dearly loved to pin it on a pilot in a hurry and bad weather, but sometimes it just ain't so.

      You..ought to be out raising hell. This is the fighting age. Put on your fighting clothes. -Mother Jones

      by northsylvania on Wed May 08, 2013 at 04:46:51 AM PDT

      [ Parent ]

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