Gross weight

December 2, 2009 by Tim McAdams

 

 

I was in a pilot lounge at a heliport where an operator was giving sightseeing rides when a pilot returned to the loading area after getting fuel. The loaders brought out five passengers and I heard the pilot say over the radio that they put too much fuel onboard and he could only take four passengers. Right then another pilot who worked for the sightseeing operation jumped up and said, “No, don’t take the passenger back. I’ll do the flight.” He ran out and told the pilot he would take over so the pilot could take a break. As I watched the helicopter lift off, the guy standing next to me (who was not a pilot) said, “Now there goes a real pilot.” I looked at him waiting for him to crack a smile or give me some signal he was kidding. He was serious.

 

I have known helicopter pilots who don’t think too much about gross weight. If it can hover, it will fly fine they would say.

 

Case in point, according to the NTSB the pilot of a Bell 206L departing on a sightseeing flight on a hot summer day lifted the helicopter to a hover and started a takeoff run. The pilot said it felt like the helicopter did not have full power and it did not gain altitude as it neared the end of the heliport. The tail rotor struck the edge of the pier. The helicopter then hit the water, the pilot deployed the floats, and the helicopter rolled inverted.

 

 

When the pilot was questioned about the lack of engine power, he stated that sometimes dirt or dust could lodge in the fuel system and then dislodge from the impact. When asked if the helicopter was overweight, the pilot stated no, because he was able to hover with an indicated turbine outlet temperature (TOT) of 720C and 92-percent torque.

 

Regarding the helicopter’s weight and balance, the pilot stated that he did not ask passengers their weight and did not have a scale at the heliport. Rather, he estimated the weight and balance. For the accident flight, he estimated 150 lb. per person, as there were three male passengers and three female passengers. After the accident, an FAA inspector questioned the passengers about their weights. The passengers reported their weights as 132 lb., 176 lb., 187 lb., 207 lb., 210 lb., and 213 lb. In addition, the pilot weighed about 190 lb. Although the pilot estimated 150 lb. per passenger, the average weight of the passengers was approximately 188 lbs. Those passengers plus fuel made the helicopter about 250 lbs. over gross weight at the time of the accident, not including the weight of clothing, personal effects, and baggage.

 

The FAA puts the standard average weight for operators with a no-carry-on bag program to 184 lb. in the summer and 189 lb. in the winter.

 

 

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24 Responses to “Gross weight”

  1. Anon Says:

    I was dealt some severe criticism for canceling a flight with our CP during my CFI training. With him listing his weight as 240 lbs (the max seat weight for an R22), I couldn’t get us within CG. He even had me recalculate the CG using a different weight (not a scale weight, just a different weight). The next day, I learned the fat pencil technique for calculating CG: off load a little fuel so you are below MGW. Use a fat pencil to fudge/plot the weight and arm data. If your point is touching the forward CG line, you’re good to go. If it is not, off load some more fuel and use a fatter pencil. When I discussed this with other instructors, the said they had “no CG problem” flying with the CP, even in helis with a less favorable longitudinal arm. I thought I musta been a mathematically challenged idiot, so I had one of the more emphatic instructors do the calculations. He didn’t finish them, and just said it was close enough and that he’d flown with the CP. Since he was heavier than I was, he opined that I would be fine and should just do the flights.

    The owner of the school was not happy with this–me canceling the flights, not us being out of CG. Ultimately, I ended up quickly losing a few pounds while waiting for the lightest helicopter to come out of its annual. We did the flights, without doors, in the winter. Just from watching other students in the ready room, I learned that W&B and performance data are for check rides, not for everyday lessons. Several of those guys got hired and will probably make their 1000 hours, but I learned a lesson.

  2. Avi Weiss Says:

    Tim;

    Sadly, this casual approach to weight and balance limitations is not limited to helicopter pilots. The fixed wing version of that thinking is: “if it fits in the plane, it can fly”. Equally unfortunate is that the merits of operating a revenue-producing (or really any) flight that exceeds aircraft and pilot “limitations” will probably be continued to be argued as long as people can get paid to fly.

    Given the diverse nature of aviation, revenue-producing missions often come into stark conflict with aircraft operating limitations. Given the direct cause-and-effect relationship completing a revenue-flight has on producing …uh… revenue, as compared to the number of times those flights that did exceed an aircraft limitation directly caused an accident, it is not surprising that tremendous pressure is often brought to bear on pilots to conduct such compromising flights, with subtle and not-so-subtle intimations as the caliber, ability, or “realness” of that pilot if they DON’T, and the attendant threats to livelihood. What’s worse, limitation-violating flights that are conducted to safe conclusions only serve to reinforce the misguided notion that “limitations are only for pilots who aren’t good enough to find their own” (my apologies to Chuck Yeager for twisting his famous quote).

    What most of those who espouse that thinking don’t take fully into account is that most aircraft limitations do not necessarily have a one-to-one relationship between limit-exceedance and determining if such exceedance will result in the flight coming to grief. Using weight-and-balance limitations, while the aircraft MAY lift off being overweight and out of aft CG, and it MAY even fly safely being overweight and out of CG, that doesn’t account for the time a flight conducted overweight and out of aft CG encounters a downdraft, or an updraft that pitches the aircraft nose skyward. So, in a way, limitations can be viewed as “insurance policies”: you hope to never need them, but if you do need them, it’s good to know you have them.

    At the risk of stating the obvious, adhering to aircraft limitations is not some form of conservative risk aversion, or some form of confidence or skill defect, but the mark of a sensible and level-headed pilot, who accepts the inherent risk in flying, but does what they can to minimize exposing themselves, their aircraft, and their passengers to it.

    “There are old pilot, and bold pilots…but there are no OLD, BOLD pilots”

  3. Steve Says:

    On the R-22s that I flew, we would always bust out the front of the CG envelope before going over gross. In all the calculations I ran, it basically came out that the max combined pilot/passenger/baggage weight was 430 pounds. Didn’t really matter what combination you did there (if you followed the 240 lb seat limit) and every R-22 was so similarly equipped that it always seemed to be within a couple pounds of that limit.

    It sure seemed like my instructor just gave me a number for his weight that would make everything work out when I did the CG calculations while working on my rating. The weight he gave me made us come up right at the forward CG limit and max gross limit.

    After earning my rating, I did tell one of my friends “One of us will need to lose 15 lbs to go flying, well, actually you’ll need to lose 15 lbs before I can take you flying.” I wasn’t going to go through the effort of losing weight to take him flying. :-)

    For those that are interested, I have an Excel spreadsheet for doing R-22 W&B calculations posted at http://homepage.mac.com/swaltner/flying/r22weightandbalance.xls

    My understanding is the big risk about going out the forward end of the CG envelope on a helicopter is not having enough back cyclic to either stop the drift in a tailwind or properly flare at the bottom of an auto. Not something I’d like to experience.

    Going over the gross weight invalidates your IGE/OGE charts in the POH and puts you at risk for accidents like those described in the blog posting. It’s been a while since I went to the RHC Safety Course, but I remember them showing parts that were failed/fatigued from the helicopter being over-torqued due to being repeatedly flown over gross weight.

  4. Chris Says:

    I’ve been an advocate of always doing a W&B before every flight. One of the problems I ran up against was that the school’s pre-printed W&B sheets didn’t always have the right data on them. A common problem was that the basic empty weight x the arm wasn’t equal to the number they had pre-printed in the moment column. This error was on the worksheets for most of the aircraft, and had been for a while, but nobody else had ever noticed.

    Steve, I think I’ve seen your W&B sheet on Just Helicopters. I’ve also developed a set of Quick Weight and Balance Calculators for the R22 and R44 that allows schools to lock down the BEW and arm data, to quickly adjust fuel load, and to change removable equipment (doors and controls) easily. They also automatically plot the data so there can be no massaging the outcome when the numbers are close to the limits. I have one for the Mariner as well, but need somebody who flies one to check it out for me.

    With my weight, I have to be flying with a really big instructor to be out of CG if we’re at or below MGW. My whole philosophy around doing a W&B before every flight was that it is a good habit to develop early in training, just like checking the squawks, Hobbs time, weather, and performance data–even for flights in the pattern.

    And Avi is right. Even if you’ve flown outside of the limitations a dozen times and nothing’s happened, you don’t know when you will encounter the one thing that will make the difference. I know one guy who was doing his W&B and managed to get out of CG with zero fuel. His response was that it wasn’t a problem because he’d land before then. Never even considered the possibility that a flight might not go as planned, or that being so close to a limitation leaves no margin for error.

  5. Avi Weiss Says:

    Along the same lines of “I’ve flown over-gross / out of CG and it’s always been fine” is the long-standing myth that engineers build in very conservative margins to the limitations, ostensibly to prevent the aircraft from coming anywhere near its “ultimate” limits.

    As an formally trained aerospace engineer, and having spent a considerable amount of time reviewing aircraft designs and attendant limitations, I have not seen the very conservative limitations often spoken about by pilots. Much of the “margin” that appears to be for conservative purposes, is actually based around ensuring airframe components make it to their service life, as Steve had mentioned.

    That many calculations are “off” due to moment arm mis-measurement, or incorrect weight values being provided, does not provide rationale to simply “game” the exercise to produce the desirable results. As has been stated by a few already, do the calculations as if your life depended on it, because same day, it just might.

  6. Nic Says:

    Hi
    I am a big fan of the Hover Power blog. I too, have a great love for aviation. I learn a lot by reading your articles and respect your thoughts and opinions and that is why I have one question for you.
    I am 20 years old and have a helicopter private pilot license, currently working on my instrument rating and progressing to a commercial helicopter license. I am always well dressed, well spoken and carry myself in a professional manor. Do you think by having dreadlocks will reduce the chances of landing a job as a helicopter pilot even if I have met all of the proper qualification?
    Look foward to reading future articles!

  7. Eric Miller Says:

    Nic, If you want t be hired as a professional pilot, your appearance must fit the job. Why handicap yourself? If you want to wear dreadloocks you may as well show up with a lot of tatoo’s and a pirates eye patch too. The Impression you make will be the same. Companies in business to provide pilot and aircraft availability combined with a reputation for safety will respectfully decline to hire you. They want someone that the paying customer will feel comfortable with. The application and your experience gets you the Interview. Your interviewing skills and appearance gets you the job. Your professonalism, flying skills, maturity and personality when dealing with the customers allow you to keep the job. Refusing to fly broken or out of C.G. aircraft or operating in marginal weather will allow you to live long enough to gain the experience to move up to bigger, better and more capable equipment.
    Flying is one of the best possible occupations for a huge number of reasons. (And I have been a professional pilot for 47 years now) The secret is to not let accountants or management types talk you into killing yourself just to save/make a few bucks.
    No matter WHAT they say, promise or threaten SAFETY in training, planning and execution of every single flight is the only thing that will make it all worth it. Listen to that little voice inside your head-the one that says “I’m NOT comfortable with this” NEVER listen to the one that says Hey watch this-it’s cool………….. Best of Luck to You

  8. Maria Says:

    First of all, I want to remind the folks reading and commenting here that being out of CG and being over gross weight are two separate things. While you can be in both conditions, you can also be in EITHER condition. The topic of this post is being over gross weight, so that’s what I’ll comment on.

    There are two aspects to a helicopter’s gross weight:

    1) There’s the max gross weight for the aircraft, which is something you should NEVER — in a perfect world, anyway — go over. The manufacturer has created this limitation for a variety reasons and the ability to lift off or hover may NOT be one of them. It could be structural. Would you want to fly a helicopter over Max Gross Weight if you knew that every time you did, you could be putting additional stress on the airframe/blades/etc. that could lead to a failure in a future flight? I wouldn’t.

    2) There’s a practical gross weight as it applies to high density altitude. Look at the performance charts. Can you maintain an IGE hover at Max Gross Weight when the LZ is at 6,000 feet and it’s 95°F out? I do a lot of high density altitude flying in Arizona and I’ve experienced a wide range of weight and density altitude situations. I can assure you, max gross weight might be a limiting factor at sea level, but it’s an optimistic number at high DA.

    If you’re the pilot in command, it’s in your best interest to REFUSE any flight over Max Gross Weight based on real weights. If you’re the owner of the operation, you’re out of your mind if you set up a flight over Max Gross Weight — the liability is frightening if something goes wrong.

    Thanks for this post. It’s given me something new to blog about.

  9. Maria Says:

    One more thing: I WISH my passenger’s weighed only 150 lbs. Hell, I wish I weighed only that much. ;-)

  10. Keith Gill Says:

    Unfortunately the super pilot phenomenon is still pretty common in our industry. Our company has a most conservative rule for all operations that we fly. This means that anyone on the flight crew which can include the mechanic and interpreter or observer can invoke the most conservative rule and the flight will be changed ,canceled or discontinued.
    There is no debating the issue at the time. An alternative to that flight will be found or we land and discuss the issue.I have never let another pilot or especially non pilot or customer’s opinion of my flying decide the flight to be flown.That is why I am the pilot in command and why I make the decisions that my passengers live or die with.
    The pilot who lets another pilot knowingly violate the air regs. or limitations of the aircraft is doing everyone a disservice.
    Speak up when you are right, acknowledge your mistakes and keep learning.

  11. Dr. Rob Says:

    Years ago, a fellow Army Aviator had a side business hopping pax on weekends with a Bell 47. He asked me to fly for him on one of his weekend “missions,” hopping pax out of a super market parking lot. The aircraft had a l-o-n-g right hand seat belt, and the local high school kid hired as a loader was instructed to put folk in until the seat belt would just barely fasten around them. Things went well until, with min fuel on board, I got a particularly “dense” passenger load. I pulled pitch, cleared the building in front of me, and made the requisite “wazoo” around the area. I flew back to land, and had plenty of cyclic to flare, but as I came to a hover, the ‘copter, with full back cyclic, started moving again, and accelerating, toward the Safeway store, . Fortunately, I was able to lower the collective and get enough braking from the skids to stop about 10 feet short of the building. The boss, the loader and I quickly had a “come to Jesus” meeting about what constituted “about enough” of a load.

  12. Harold Says:

    It is only the highest time most skilled of writer/pilots that can determine a helicopter pilot’s weight solely from a radio transmission.
    Well done!
    Or maybe it was that the pilot in the FBO who ran out to take the flight was the lighter of the two.
    Leave the flying to he who is in the cockpit and the and the finger pointing blogs to another publication please.

  13. Vengeance 07 Says:

    HIGE power equals take off power and passing through translational lift will further decrease power required. Most of the helicopters I have flown have been limited based on the strength of the landing gear. One can further get a good low runway take off and get to an airspeed which will maximize the power margin. The real challenge comes when you need to land. Power management is the key in flying a good approach to give up translational lift as you are settling into ground effect. Remember ground effect is not lineal. I get to see military pilots every day take down wind take offs and fly sloppy because they believe their aircraft will never run out of power. I have case studies full of Cobras, Super Sea Stallions, and Phrogs all running out of power. I fly a Huey. I live at max gross weight everyday and for me, I know the demends who live on the other side of that limitation line. 2300 hours tells me not to go there unless it’s life or death.

  14. Nate Says:

    Dr. Rob,

    I had a similar situation flying a fairground like mission but slightly differant concern. I was flying a Bell-206B which as many aircraft has more seates then a full tank will allow to fill. I had explicit instructions to my loading crew that I could only take 2 pax until I gave them the signal. I was close to giving them the thumbs up for 3 when they sent out a very “Healthy” man and another that was about 180. A quick rough swag showed that we were just under max gross my concern now was if the gentleman could get the belt secured. I didn’t want to embarasse him in front of the line of folks. This being the 10th flight of the day we had got into a habit pattern so we continued as usual. It wasn’t until I lifted that I realized they had loaded the other passenger on the same side of the aircraft and now I became quickly aware that I may have a CG issue. Again, not wanting to embarass and had a very long LZ, I continued teh T/O but made as gentle of turns as possible as I made one very large circle for a pattern and came back in to land. I would contradict Maria in saying that Weight and CG are not seperate issues since as weight changes so does CG. They go hand in hand and should always be considered together. To many people get wrapped around weight only as did I in this case.

  15. Ehud Gavron Says:

    I’m a 110hr pilot so I still do W&B for every flight. I use a spreadsheet given to me under NDA by my flight school. The first one here is almost great. The second doesn’t run in OpenOffice. Still, without these tools we still have a pen, a paper, and a calculator.

    I was trained against the fat-pencil approach. I know there are three sets of rules:
    1. What we tell the FAA DE during the checkride
    2. What we tell the CFI when asked during training
    3. What we do

    My instructor made it a big deal to emphasize that #1 is all about “giving the book answer” but the second and the third need to be the same.

    The exact quote was “If what we do is not what we were taught then we should review why we were taught that with the instructor and either change the teaching, or change the behavior.”

    In the Robinson Safety Course they spend an entire day discussing the mechanical aspects of the aircraft. Those limitations are there for specific reasons. Being over gross weight means the stress on the transmission and MR may cause fatigue. You’ll never know if YOUR over-weight flight caused the fatigue that causes it to break on the next flight… unless you never do it.

    I’m not a rule-follower when it comes to traffic, taxes, and saying “the appropriate thing”… but I am when it comes to flying a helicopter.

    Cheers

    Ehud

  16. ROSEVELT SMIF Says:

    MITER TIMS
    I CANS REALLY BELATES TO YU’S GROSSLY WEIGHTS MESSAGE. I WAS GEETEN READYS TO FLY MYS HELIWOPTER AND MY TO BIG SITERS SHOWS UP DA RIDE. WHEN DEY GOTS OUT OF THE CAR I KNOWED DEY WAS GROOSLY OBERS WEIGHT, SO I’S COULS ONLY TAKES ONE AT’S I TIMES WIFF ABOUT’S TIRTY GALLON OF FUELS. WHEN DA REALLY REALLY BIG ONE GOTS IN DA SKIDS SAID OUCH! NOW I GOTS DA HIGH SKIDS AND WHEN SHE GOTS IN I TAUGHT I HADS LOW SKIDS. I TOLD HERS SHE BROKE MY HELIWOPTER AND SHE HADS TO GETS OUT, I WASEN NOT GOIN TO FLY’S HER. SHE’S WAS REALY MAD AT ME BUTS I WAS NOT GOIN TO RISK MY LIFE. I TOLD ‘S HER TO LEAVES AND TAKE’S A AIRPANE RIDE ON A JUMBOS JET SO SHE’S COULD’S GET OFF DA GROUNDS. YOU’S REALLY MAKKES YOUR STORY GOOOD FOR ME’S TO UNDERSTANDS AND KEEPS ME SAFE

    MEERRY CRITMAS AAND HAPEE NEW YEARS

  17. Brendan Fitzpatrick Says:

    Wow – why is always the simple things that seem to get us? How early on our training do we learn about the dangers of flying over gross weight. Thanks for reminding us!

  18. Maria Says:

    Nate: Weight and CG DO go hand-in-hand — no argument there. But this blog post is about weight and not CG and that’s what I responded to.

    You can be within max gross weight and still be out of CG just as you can likely be over max gross weight and still within CG. One is weight, the other is balance. Separate but related.

  19. Mike Says:

    I knew the Pilot of the site seeing helicopter that you mentioned. He was a talented pilot. When you expose yourself to risks time and time again it is only a matter of time before you have an incident or an accident. A few monthes after this accident a S-76 was departing another heliport north of this accident scene and he two went into the water. He was also over weight on a hot day. When you let employers push you into taking risks it is only a matter of time before an accident. When that happens the responsibility always falls on the Pilot in command. The FAA will fault the pilot, not the opefrator.

  20. 1553 Says:

    Now that’s a “heavy” problem… ;)

  21. Facebook Sluts Says:

    The Black Hawk helicopter can carry a gross weight of 22,000 Lbs and an external load of 9,000 Lbs.

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