Weight Is Focus of Plane Safety

WASHINGTON, Jan. 27 — Saying that overloading may have contributed to a fatal plane crash this month in North Carolina, federal aviation officials announced today that thousands of passengers flying on small planes over the next month will have to tell ticket agents how much they weigh, or step on a scale, to check whether existing estimates of average passenger weight are accurate

The Federal Aviation Administration is ordering all 24 airlines that operate the small planes to collect weight information from a sampling of their flights. Investigators suspect that a Beech 1900 that crashed on takeoff in Charlotte, N.C., on Jan. 8, killing all 21 people on board, was overloaded. Flawed weight estimates could have contributed. If studies show that average passenger weights have increased, that could require airlines to leave some passengers or baggage behind, especially on flights requiring full fuel loads.

Standard guidance from the agency to airlines flying small planes, including US Airways Express, which operated the Charlotte plane, is to allow 180 pounds for each adult in winter and 175 pounds in summer. Both figures include clothing and shoes and 20 pounds for carry-ons. Children ages 2 to 12 are assumed to weigh 80 pounds, year round.

These figures were developed before obesity became the public health problem it is today.

No recent studies have confirmed the current validity of the government's figures, said Lou Cusimano, deputy director for flight standards. "If we find the weights cannot be validated," he said, "we'll take the next step."

That would probably mean a bigger study that would weigh more people, he said. If the agency concludes that its averages are too low, it could raise the figures that airlines must use. The paperwork for the Charlotte plane showed it was within about 100 pounds of its maximum load, according to the National Transportation Safety Board, which is still investigating the accident. If passengers or their bags weighed more than assumed under the aviation administration's estimates, it may have been overweight. The plane's flight data recorder showed that it climbed at takeoff at an angle of 52 degrees before it crashed. It pitched up more and more steeply until it was pointed too high to fly. Investigators are looking into whether too much weight in the back of the plane caused the nose to pitch up.

The airlines will be adding 10 pounds to whatever passengers tell them that they weigh. Peggy Gilligan, director of flight standards at the agency, said that she expected people to fib about their weight, but that "they usually lie in the single digits." But officials said passengers generally do not consider the weight of their clothing and shoes.

The airlines will also be weighing bags to verify that assumptions about their weight are still correct. The standard allowance is 25 pounds per bag for domestic flights and 30 pounds for international flights.

Aviation agency officials said they had been using the 180-pounds-per-person estimate since 1995 and possibly longer.

The rule issued today applies to 24 airlines that operate planes with 10 to 19 seats. There are 223 such planes in airline service, made by a number of manufacturers. The planes include the Beech 1900, the DeHavilland Twin Otter and the Embraer Bandeirante.

The airlines must ascertain the weight of all passengers and bags on a sampling of their flights, covering 30 percent of their routes. They must pick flights at varying times of day, and on a Sunday, a Monday and a Tuesday.

Mr. Cusimano of the aviation agency said that assumptions on weight were now used only for regular passenger service. If a small plane were being used as a charter for a football team or for a group of soldiers with heavy equipment, he said, the airline would have to weigh each bag and ask about the weight of each passenger.

Soon after the crash in Charlotte, investigators asked gate agents if there had been any "large-statured people" among the passengers, said John Goglia, the safety board member at the scene. Mr. Goglia said they had not, thus far, asked next-of-kin about the passengers' weights and would do so "only if concern got higher" in the overweight theory. Investigators tried to weigh the luggage, which was difficult because some of it had burned.

The plane was taking off in clear weather and a light wind for a scheduled 45-minute trip to the Greenville-Spartanburg airport in Greer, 84 miles to the southwest. It nosedived seconds after taking off, slamming into a maintenance hangar and bursting into flames.

In another response to the Charlotte crash, the agency also ordered that all airlines flying Beech 1900's complete by Friday new inspections of the tail assembly to ensure that the elevators, the parts that control the nose-up or nose-down attitude, could move as far as they were supposed to.

The Beech in the Charlotte crash was serviced a few hours before the crash. Investigators suspect that the cables that run from the cockpit controls back to the tail were misrigged when they were reattached and that the elevators may not have been able to move as far into the nose-down position as they were designed to.

The order to check the tail assemblies covers 368 Beech 1900's registered in the United States. There are 688 such planes in the worldwide fleet, including some in cargo use and some in corporate fleets.

Operators will now have to check the rigging after each time the tail is serviced, to ensure it moves properly.

The safety board can take more than a year to determine the cause of some plane accidents. Investigators in the Charlotte crash have said they are focusing on the cables that work the tail surfaces, the overall weight of the plane and whether too much of the weight was concentrated in the tail.

Officials at the aviation administration said that there was no direct evidence that the tail was misrigged and emphasized that it was not their agency but the safety board that would determine a cause. The safety board is an independent body, but the F.A.A. is one of the participants in its air crash investigations, along with the airline involved, the aircraft manufacturer, and other specialists, depending on the circumstances of each crash

Here is a little info. for those not familiar with aircraft weight and balance.

Last updated 07-May-1997.

Running the Numbers
Taking time to calculate weight and balance on the ground can save you some nasty surprises in the air. Consider the misfortunes of some pilots who didn't.
This article first appeared in the June 1, 1995 issue of Aviation Safety. It's reproduced here with permission of Belvoir Publications.

by Brian Jacobson (bjacobson@avweb.com)

Are you looking for trouble?

You know as well as I do that looking for trouble isn't conducive to a long and safe career in aviation. But, we all have probably launched on trips without running the weight-and-balance numbers. And, in doing so, we may have inadvertently punched a few holes in the weight-and-balance envelopes established by the manufacturers of our aircraft.

Weight-and-balance limitations are there for very good reasons, most involving the safety of the occupants while the aircraft is in flight. When we disregard them, knowingly or unknowingly, we are looking for trouble.

Take, for instance, the hapless pilot of a Cessna 402 who attempted to transport nine members of a varsity basketball team in his airplane. The pilot did not get the accurate weights of the individuals and their luggage. As he entered the cabin to close the door, the airplane tilted over onto its tail...not an uncommon occurrence for that type of airplane when too much weight is placed in the rear of the cabin. The pilot and passengers got out of the airplane and raised the tail. Then, the pilot decided to proceed with the flight, still without having "run the numbers."

As he climbed through 300 feet AGL, he turned to those in the cabin and yelled that he had a problem. He instructed his passengers to move as far forward as they could. This apparently solved the pilot's immediate "problem," but the airplane eventually was landed with most of its passengers not seated with restraints fastened.

An inspection revealed that the 402's rear bulkhead, a stringer, the elevator control tube and the housing for the tail navigation light were damaged when the aircraft fell onto its tail. Investigators ran the numbers using actual weights of the passengers and baggage, and found that the center of gravity was well beyond the aft limit. The pilot was very fortunate that he did not lose an engine during the flight; the aft c.g. would have seriously aggravated the asymmetric control problem.

This may be an extreme case of weight and balance mismanagement and total neglect of incurred damage, but the fact remains that many of us don't pay enough attention to how we load our aircraft. While we don't get into accidents every time that happens, there can be consequences that we don't anticipate.

Ask, Don't Guess
There are compromises in the designs of almost every airplane built. We can fill the cabin or the fuel tanks; but, normally, we can't do both. Most of the time, we must juggle fuel and payload to assure ourselves that the airplane is within the weight and balance envelope. In some airplanes, like the Piper Seneca, the c.g. may be forward of its limit with full fuel and only two people aboard (in the front seats). In others, like the Beech Bonanza, the numbers should be run both for takeoff and landing, since the c.g. moves aft in a rather tight envelope as fuel is burned.

If you guess passenger and baggage weights, as the Cessna 402 pilot apparently did, you could find yourself playing test pilot and operating outside the envelope. It's best to ask each individual for their actual weight, check each piece of baggage as it is loaded and run the numbers before takeoff.

Unfortunately, you don't see too many pilots standing around their airplanes with calculators in hand. That's a shame, since it really does not take a lot of time to run the numbers. There are special plotters, calculators and computer programs for many aircraft that produce results within a minute. I have a program that takes the weights of passengers, baggage and fuel, and then shows me where I stand in a graph, similar to that in the AFM.

Still, too many pilots load passengers and baggage with nary a thought about weight and balance. The FARs don't specifically require a record of weight and balance for noncommercial flights, but all pilots are required to operate our aircraft within the limitations prescribed by the manufacturer. We cannot be sure we are doing so unless we run the numbers.

One quick-and-dirty method used by many pilots is what I call the "half-of-the-equation" system: The pilot quickly adds up the weights of the empty aircraft, passengers, baggage and fuel, and gets a warm and fuzzy feeling if the sum is less than the maxmum allowable takeoff weight. The balance portion of the calculation is neglected altogether. This practice reflects an ignorance of what "weight and balance" really is, and of what flying an airplane out of its c.g. envelope could mean to safe operation.

The balance side of the equation could be simply envisioned as the airplane resting on a pinnacle, supported at its center of gravity by one sharp point. As you add or subtract weight to the aircraft, that balance point (e.g., the center of gravity) moves. Add or subtract too much weight forward or aft, and the aircraft will fall off the pinnacle. Before that happens, though, the pilot will experience some handling problems. And, in some cases, those problems can be serious enough to cause a loss of control.

For example, as the c.g. shifts closer to the horizontal tail (toward the aft limit), the elevator becomes more effective the stick forces required to make a pitch change become very light, and the airplane becomes longitudinally unstable.

Inherent Stability
Production airplanes are designed to be longitudinally stable when operated within their c.g. envelopes. You can "feel" this when you push or pull the control wheel to make a pitch change: The airplane, when trimmed for level flight, will try to return to its trimmed condition. But, as the distance between the c.g. and the horizontal tail decreases, the stick force required to make a pitch change also decreases.

At the point of "neutral longitudinal stability," the airplane will tend to maintain its present attitude instead of trying to return to its trimmed condition. The stick force required to make a change will be extremely light, and that could result in overcontrolling. It's possible, in an extreme case, to get into a pitch attitude so high that there won't be enough "down" elevator travel to prevent, or recover from, the impending stall.

You've probably flown your airplane at one time or another with the c.g. at or near the aft limit. You'll probably remember that as you rolled down the runway, the airplane came off the ground before you expected it to. You quickly trimmed the nose down, realizing that although you set the trim forward of where you normally would, it was not enough. Then, as you flew the airplane away from the airport, you noticed that the amount of elevator travel to effect a pitch change was much less than normal.

Some time ago, a Beech 18 captain lifted off from an Alaskan airport, retracted the landing gear and found the aircraft trying to roll to the left. He corrected with right aileron and attempted to decrease the pitch attitude, but the aircraft rolled right and then back to the left. He landed near the departure end of the runway with the gear up.

Investigators discovered that no one had checked the weight of the freight and that the airplane was 1350 pounds over its maximum certified takeoff weight. Also, the c.g. was about three inches aft of the aft limit. Did the pilot run out of forward elevator because of the severe aft loading? We don't know that for sure, but the rolling action of the airplane indicates it was in or near a stall condition from the time the landing gear was retracted.

What may have happened is that the stick forces on the elevator were so light because of the rear loading that, initially, the pilot thought he had the airplane trimmed properly when it was perilously close to a stall. When he realized that, in reality, the nose was pitched way too high and tried to avoid the stall, it was too late to do anything except allow the aircraft to settle back to the ground.

The "behavior" of different airplanes loaded to an aft c.g. varies. But, remember that the manufacturer designed and certified your airplane to be operated within the c.g. limits; and, once you get behind the aft limit, you are on your own. You become a test pilot, and you relegate your passengers to playing the role of potential crash dummies.

Exceeding the forward limit can be trouble, as well. As from the time the c.g. moves forward, the controls become heavier. More effort, and travel, is required to make a pitch change. The level-flight trim position of the elevator is higher than nonmal; and, in some extremes of forward loading, you could run out of elevator before you accomplish the pitch change you want.

For example, you are beginning to flare for a landing and discover that, even with full travel of the elevator, the pitch attitude is not high enough to keep the nose wheel from striking the ground before the mains do. In fact, at the point where you pulled the throttle to idle for the landing, the nose would fall, the airspeed would increase, and you couldn't do anything about it except attempt a power-on landing probably at a higher airspeed than normal.

Adding power would pitch the nose back up, but you'd need a longer runway to help dissipate the extra speed.

On the Spot
Sometimes, it's hard to do an accurate "weight and balance" because someone shows up with more luggage than you expect, or it's obvious that some of your passengers didn't give you their correct weights. But, you should always try to be certain that the aircraft is within its weight and c.g. limits. Programmable calculators can make a weight-and-balance problem easy to do on the ramp with your passengers standing by the airplane.

Sure, doing it on paper would take a while; but if you know you have a large load to go into your airplane and you don't know the exact figures before hand, it would be much safer to delay the flight and do the calculations than to cross your fingers while stuffing the seats and baggage areas with as much as they can physically handle. After becoming airborne and realizing that the airplane is not behaving very well is the wrong time to wonder about all the luggage you loaded in a rear baggage compartment.

In one case, a Piper Lance crashed during a night takeoff from Great Barrington Airport in Massachusetts. There were five passengers and the pilot aboard. They had flown in to go skiing but found that the ski resort was closed. They decided to fly over to nearby Pittsfield, where they knew they could ski. On takeoff, the aircraft hit the top of a 60-foot tree nearly 500 feet from the departure end of the runway.

Two of the occupants died. Investigators determined that the aircraft was 368 pounds over its maximum certificated weight and loaded outside the aft c.g. limit. The runway was just under 2600 feet long, and it was the first time the pilot had flown into the airport.

The NTSB report I reviewed did not say where the flight originated or whether the pilot bought any fuel at Great Barrington; but, if he did not, then the aircraft loading was farther out of tolerance on the leg before the crash occurred. It seems as though this pilot loaded the airplane according to the number of seats and amount of baggage space it contained, rather than considering the full impact of weight and balance.

If you always fly your airplane with the same load, it is probably not necessary to do a weight and balance each time; you should know where you stand in the c.g. envelope. But, when something changes--someone unexpected shows up, or more luggage than you anticipated is sitting on the ramp--take the time to do a thorough weight and balance calculation.

Remember, the manufacturer's limitations are the result of tests of handling characteristics within the envelope (there is little or no testing outside the envelope). By flying outside the envelope, you are not only testing your aircraft and your piloting skills, but, also, the ever-present law of Mr. Murphy.

About the author...
Brian Jacobson (bjacobson@avweb.com) has over 12,000 hours in all types of general aviation aircraft from trainers to jets. He has been flying since 1970, and earned most of his certificates and ratings on the East Coast in the early 1970s.

His first aviation employment was as sales manager at Air Worcester, Inc., an FBO in Massachusetts. Through the years, he worked for several FBOs selling airplanes and flying charters. For nine years, he was chief pilot for a division of ITT based in Providence, Rhode Island, and later was a bizjet captain for Textron, Inc., out of Providence, Augusta, Georgia., and Pontiac, Michigan. During those years, he flew real-world IFR in all sorts of weather and some of the most congested airspace in the world.

Since 1988, Jacobson has been a member of the National Aircraft Appraisers Association, and owns and operates a firm called Great Lakes Aircraft Appraisal, appraising airplanes for buyers, sellers and financial institutions. He also helps individuals and businesses buy aircraft by evaluating their needs, recommending the type of aircraft they should purchase, and helping them locate and procure those aircraft.

Jacobson is also a professional aviation writer. He is a contributing editor to AVweb, Aviation Safety, IFR Refresher, a contributor to Plane & Pilot, and can be heard on Belvoir Publications Pilot Audio Update.

In October, 1996, he published his first book, Flying on the Gages, in which he discusses his experiences flying IFR. In May, 1997, his second book was published: Purchasing & Evaluating Airplanes.

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