Weight “watchers”

March 27, 2014 by Bruce Landsberg

Small-scaleGot a note from a long time member/pilot who flies for Angel Flight. He noted that his passengers tend to consistently underestimate their weights. He either has to fly overweight or inform them that 150 pounds of luggage or Aunt Tilly has to stay behind. Not so good.

The standard 170-pound human that the airlines used to estimate tonnage has been increased to about 190 pounds—with lower or higher bracketing based on season and Kentucky windage. With big aircraft it’s less of an issue, and with a large number of people the bell-shaped curve drives weights to the statistical average.

Southwest Airlines delicately addresses the issue on their website in the Customers of Size section: “…who encroach upon any part of the neighboring seat(s) may proactively purchase the needed number of seats prior to travel in order to ensure the additional seat(s) is available. The armrest is considered to be the definitive boundary between seats; width between the armrests measures 17 inches. The purchase of additional seats serves as a notification to Southwest of a special seating need, and allows us to adequately plan for the number of seats that will be occupied on the aircraft.”

For light aircraft, weight and its distribution go beyond decorum/comfort to safety of flight. Generally, the aircraft is already fueled by the time the passengers show up, and the pilot has planned on a certain amount, so we don’t have that flexibility. De-fueling is expensive and messy. If the runway is short or the density altitude high, rate of climb becomes essential to survival.

One technique that has served me well is to consciously add weight to whatever a potential passenger tells me. The percentage varies based on the suspected veracity and gender of the traveler. For luggage, I have a small digital scale that helps to ensure that neither weight nor balance limits are exceeded.

Our member suggested perhaps having the AOPA Foundation buy digital scales for FBOs to actually weigh passengers. “Perhaps,” he suggests, “use it as a fundraising campaign as well as a safety reminder.” It’s a novel idea but potentially explosive. What do you think?

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Bruce Landsberg
Senior Safety Advisor, Air Safety Institute

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  • Harold

    We do one and two person tours as part of our business. If a couple, we ask for a Total Weight, not individuals, and explain this is a safety issue. We find generally we get more accurate weights this way and have even had a partner tell us on the side to “add 20 lbs., he/she doesn’t know what I really weigh”

    If the weights seem too low, we’ll add weight, but basically it’s true 95% of the people will lie about their weight, some outrageously (like the 250+ lb. person who insisted they were 120 pounds – Riiight!)

  • Great Blue

    Fat chance that people will use the scale.

  • Duane

    Like anything else in flight planning, including a margin of safety is the way to deal with uncertainty. Most of the common four to six-place private aircraft used for actual transportation, as opposed to purely local around-the-patch recreational flying, have the ability to fly 5 or more hours on a full tank of gas at economy cruise. That’s well beyond the flying time most people are comfortable going between bathroom stops!

    A nominal two-hour flight leg, especially when carrying passengers who aren’t necessarily seasoned small-aircraft veterans, is a good rule of thumb. So knowing that, why fill the tanks to the top?

    When flight planning for passengers whom you don’t know well enough to reasonably estimate their weights (such as, you’ve never laid eyes on them before), then the rule is, only have enough fuel on board to fly to an intended destination about 2 hours out, plus another hour’s reserve – or 3 hours flight time, plus or minus, depending upon where a convenient fuel/bathroom airport stop is located. Not adding that other 2 plus hours of fuel saves around 120-200+ pounds of gross weight, depending upon the aircraft, which gives the PIC a pretty decent margin to deal with passenger payload variance.

    Bruce’s statement that the airplane typically is already fueled prior to passengers showing up at the FBO does not preclude thinking ahead.

  • Thomas Smith

    I fly Angle flights also and i carry a small scale to weigh the people and the baggage. I can tell you its no surprise that most women lie about their weight and i have had a few refuse to get on a scale until i tell them we all could die if my plane doesn’t get off the ground because of weight. I even had one woman finally agree to get on the scale only if no one was watching and her husband would not know her weight. When she returned from weighing herself around the corner and i asked her in private her weight she said “i am not telling you”. She finally told me and i verified the weight when i told her she could not fly if i did not know her weight. When flying Angle flight in my 6 passenger plane i am flying at or very near gross weights with most Angle flights because of the nature of the transportation and the baggage.

  • Jeff Coghill

    Ahead of any flight with passengers, I tell them about needing to know their weight. “If you don’t tell me your weight, you don’t go.” Also, I emphasize the safety factor and that GA aircraft are more sensitive to weight issues than airliners. It usually leads to a discussion of weight and balance issues, how much gear we have on board, how much fuel I carry…that kind of thing. I also add, “give yourself an extra 10 pounds for clothes and shoes.” When you have this kind of discussion, and lace it with humor, folks are pretty willing to tell you their weight. Then I discuss in-flight movies, flight attendants, and beverage services and we have a laugh.

  • Charlie

    I’m a helicopter pilot and have transported lots of passengers. I tell them that I need their weight and that their safety and the safety of the other passengers depends on being honest. I provide post it notes to write their weight so no one has to verbally state their weight in front of the others. Baggage gets weighed.

  • Chris Rodrigues

    If it is important (within several hundred pounds of gross or close to CG limits),I bring out a set of scales for both passengers and baggage. You don’t weigh, you don’t fly.

  • Richard

    Good to read that pilots are being assertive (not hostile and not passive) and have the political sensitivity to discuss the seriousness of weight and balance issues on light aircraft (vs. “heavy” commercial aircraft).
    Take off, climb, and maneuverability are serious issues that carry more weight (no pun intended) than issues of vanity

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  • http://www.aopa.org/asf Bruce Landsberg

    To Duane’s comment about planning ahead on fuel load – that was exactly the point and I’m educated by some of the clever techniques used to avoid public embarrassment.

    Share them with your other pax- carrying pilots. It would be nice to get thorugh this flying season without and overweight or out of balance accident.

  • Mike Bevan

    When I teach weight and balance in ground school I make a point of emphasizing that they need to get the passengers “You die if you give me the wrong weight” weight and not their target weight or their ‘social’ weight. Though I then recommend phrasing it some other way to the passengers.

    I have noticed that nobody ever seems to get on the scale we keep at the flying club.

    One thing I do for flying with students is precalculate the maximum weight that can be in the other seat and not exceed weight or shift the cg too far forward and then ask if they are more than that weight. That seems to get a more honest response. That only works well with one passenger, but a lot of flying is done with only one passenger.

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