Shell Card

Military charters—troop movements either to or from the United States—don’t work the way scheduled service trips do. They don’t even work the way a normal civilian charter does. Which makes them hard to describe or explain without getting awfully confusing. It’s a little like trying to explain baseball to a foreigner: a very simple game, really, hit a ball that’s been thrown to you somewhere where the other guys can’t catch it. You get three tries, and if the pitcher throws you pitches that aren’t any good, you get to go to first base for free after four of them. Except for foul balls, which count as strikes. Unless you already have two strikes, and then they don’t. And so on. Baseball starts simple and gets complicated fast. Likewise with military charters, but let me try to explain, because unless you understand something about how a military charter works, a good part of this story won’t make any sense, and the not making any sense part will probably then become the focus, which would be too bad because this is really a Christmas story.

A military charter typically starts or ends at an Army air field, an Air Force air base, or a Naval or Marine air station. (We’ll assume here the trip is one “going over”—leaving the US for some hot spot overseas, but the same process happens bringing troops back.) The airplane for that trip has to be flown into the air base from somewhere else—“ferried in”—by one crew, and will be picked up to start the trip by another crew that has commercialed in separately. This allows the working crew—the crew who will begin the actual troop movement—to be fresh and maximizes their duty day, which maximizes the length of the first leg. Because these troop movements typically cover such long distances—Hickam Air Base in Hawaii to Bishkek, Kyrgyzstan, is not unusual, for instance—that first crew almost never takes the troops the whole way. So another crew is prepositioned further down the road—Bangor, Maine, Shannon, Ireland, Frankfurt, Germany, are typical crew change points—and that crew picks up the flight and takes it from there. Typically that crew cannot go all the way either, but hands it off to yet another crew who often complete the final leg to the destination, and do a “turn”—turn the aircraft around and fly it back empty to the crew who brought them the aircraft. That crew has had 18 hours of so of crew rest and they take the airplane back to the first crew, who have had two days or so of crew rest, and that crew brings it back to the States somewhere, wherever it is needed for its next trip.

When everybody gets to where he or she is supposed to be—everyone is in place—and the airplane isn’t delayed anywhere, it all works fine, but even at its best it is a complicated operation. The troops don’t get any stops for rest—they are on the aircraft the entire time from departure in the States to arrival at the final destination. You never hear any complaints, though, mostly because they’re military and it’s just part of the job, but also because they know they are on a civilian airliner with hot meals and pretty girls, and they know that the alternative would be a sling seat on a C5 with MRI’s, and that the closest thing to a flight attendant would be a loadmaster.

ATA, then known as American Trans Air, flew many missions into Mogadishu, Somalia, beginning in December of 1992. The crew changeover points for these missions were typically Shannon, Ireland and Cairo, Egypt. I did several of these missions as an L-1011 First Officer between Cairo and Mogadishu, which meant I had to first “position”—get myself from the US to Cairo using the regular commercial airlines—well enough ahead of the arrival of the actual aircraft to have my legally required crew rest and be ready for my leg. One trip in particular stands out because I was commercialling over on TWA out of JFK to Cairo, and as it happened a very senior TWA crew, consisting mostly of management pilots and check airmen, was also on the aircraft positioning over to do a Mogadishu “turn” out of Cairo as well, just a few hours before our scheduled mission. We exchanged pleasantries, and they said it would be their first mission to Mogadishu, and expressed some apprehension about the whole affair. (I think TWA had contractual limitations on using line pilots for these kinds of trips, which meant management pilots had to do them—I don’t think they were exactly willing volunteers.) Anyway, I said I had been there before, that it wasn’t any real big deal except for the odd chance of getting shot at (nervous laughs all around), but that there were a few things to watch out for which I would be glad to go over if they were interested.

And they certainly were interested. I told them that the airport was basic and limited: one runway, no taxi way, and a small ramp, “small” meaning room for only one civilian wide body at a time (they were going to take in a 747). That meant you had to be right on schedule, and it meant taking a lot of extra fuel in case things didn’t work out and you had to hold waiting for room on the ramp.

“No taxi way” meant you had to turn around at the end of the runway, on the runway itself, and then taxi back to the ramp. The tricky part here is that the runway was only 150 feet wide and wide bodies like the 747 and the 1011 need a minimum of 142 feet to turn around—a very small margin of error on either side—and if you blew it you would bury a "truck"--a whole set of main landing gear--in the sand on the side of the runway, grounding you for days and shutting down the airport. No one wanted to be on the airplane that did that. But, I said, there is good news: it isn’t shown on the airport diagram, but there are extra little half moon shaped turn around points at both ends of the runway, which give you quite a bit more room to turn and really take most of the sweat out of it. They were relived: turning a wide body on a 150 foot wide runway is something most pilots spend their entire careers trying to avoid.

Finally, I said there is no fuel available in Mogadishu, which means you have to tanker fuel—carry extra fuel with you—so that you can go on to Djibouti, the nearest facility that did have fuel. (Djibouti is both a city and a country, like “New York, New York.” It is on the horn of Africa, and is an ally, of sorts, of the United States. Mostly I think they like our aid and our business, but that’s another story.) I told them that Djibouti won’t take credit cards for the fuel, not even American Express, only cash or Captains’ checks (checks the company provides that the captain can use to make cash purchases. Surprisingly, they are accepted nearly everywhere.) One of them said, “Oh that’s no problem, we have a Shell card, it won't be a problem.” That was news to me, but I didn’t say anything. Maybe they knew something we didn’t—they were TWA after all, everyone had heard of TWA, but American Trans Air? (The usual response to "American Trans Air" was, “Is that part of American?”) I said to my captain, “How come we don’t have Shell cards?” He shrugged and said, “Who knows.”

So that was that. We landed in Cairo and went to our separate hotels. The next day we left for Mogadishu and on our arrival overhead the airport we saw their 747 below us, taxiing back into position for takeoff, presumably headed to Djibouti, so we assumed everything had gone alright for them at that point.

This was in December of 1992, months before the infamous "Blackhawk Down" catastrophe, but Mogadishu, in fact, all of Somalia, was already a very dangerous place. Rebels were assumed to have air-to-air missiles, so we took different, random routes over Somalia into Mogadishu each time. (The route from Cairo took us down the length of Egypt, over Sudan, over Ethiopia, and then across Somalia. I never heard of any missiles being launched, but you never knew.) Once on the ground at Mogadishu, the airport itself was squeezed between the ocean and a bluff probably 100 feet high that ran the length of it. Looking up at that bluff from the ramp you could see militia types walking around with rifles, machine guns, and grenade launchers. A lot of troops were actually camped on the airport grounds, and the bad guys would occasionally lob a mortar onto the field just to keep everyone from sleeping too well. Again, not while I was there, but it kept you on your toes. No one needed to tell us that we needed to make a quick turn. Nonetheless, it still probably took two hours or so to off load the troops, get all their gear unloaded and get cranked up and turned around and on our way.

The hop to Djibouti for fuel was a short one, less than an hour, so by the time we got there it had probably been three hours or so since the TWA 747 had left Mogadishu, plenty of time to get to Djibouti and refuel and go on its way. So we were surprised to see it still on the ramp when we taxied in. The captain, the flight engineer, and I all headed into what passed for a terminal, really just a two story building with various government offices, to start the fussy process of paying landing fees, filing ICAO flight plans, and paying for handling, lav cleaning, air stairs, and water service, none of which we needed but were obliged to pay for anyway—your tax dollars at work around the world. We were even more surprised to see the entire TWA crew sitting in the terminal lobby, looking quite disheveled and unhappy—ties had long ago come off—and something much worse than the weariness of an already long day had set in.

“Hey, guys, how’s it going? What are you guys still doing here?” someone said.

After several moments of silence and irritated looks all around, one of them finally said, “They won’t take our Shell card.”

“Wow, bummer. What are you going to do?”

“We’re trying to get some cash wired in, but the company says it could take as long as 48 hours.”

“We tried to tell you” wasn’t what they wanted to hear. After a couple of awkward attempts at sympathy, our flight engineer—flight engineers are, if nothing else, experts in the practical world of thinking on their feet—perked up and said, “You know, $50 can go a long ways in this part of the world.”

“Really?” one said. “Do you think that’s all it would take?”

“I don’t know, but it sure wouldn’t hurt to try.”

So one of them, I think maybe their flight engineer, went upstairs to the fueling office, and came back down after less than five minutes with a big smile on his face. “You were right. They find they can accept our Shell card after all.” Smiles all around.

So we all refueled, got our lavs cleaned and water serviced, paid outrageous amounts of money for it all, and headed out again on our separate ways, which in our case meant back to Cairo where the crew who brought the airplane into Cairo was waiting to take it back to the States.

When we got to Cairo most of us on the crew elected to stay on the airplane and ride it back all or part of the way to the States, even though we had rooms reserved for us in Cairo and could have gotten off there and later made our way back home commercially. But with big first class seats to sleep in and racks of movies to watch, staying on the aircraft with another crew to do the work made getting home a lot easier and a lot quicker. The company didn’t care because we saved them from having to pay for hotel rooms in Cairo and plane fare out of there, so everyone was happy and we set off for the next refueling stop which was scheduled for Shannon, Ireland.

When we got to Shannon most of the crew elected to stay on, but the captain and I had had enough of airplanes for one day, and we were kind of looking forward to a night in Shannon, and we knew we would have an easy trip back to Boston where we both lived the next day. So we got off and were picked up by Conway transporters, our regular crew bus providers, so regular that we knew the drivers by name, and were taken to the Limerick Ryan, our favorite hotel in the Shannon-Limerick area, a place we had spent so much time in it was almost a home away from home. (It has since been converted into something like a retirement home, I think, to the dismay of all crew members from the many airlines that used it over the years.)

The core of the Limerick Ryan was an older Irish mansion, and added to that over the years were restaurants, bars, lounges, and a rather ugly, ‘60’s era tower that housed the actual rooms. (No one minded, you didn’t spend much time in your room.) By the time we got there the public bar was closed, but, one of the great traditions of both English and Irish hotels, the residents’ bar—a private bar for guests only—was still open. (Actually, the residents’ bar has no hours and will stay open as long as there are guests to serve, and after that there is always the Night Porter who will fetch a Guinness for you. You never have to think about a having a Guinness all the way to Ireland only to find out that the bar is closed when you get there; a way will be found to accommodate you.) The residents’ bar was more like a living room, and the staff had decorated it for Christmas, there was a fire in the fireplace and it was all very relaxing and quiet, the perfect end to a long day that had started in Cairo. And then it got even better: someone said, “Oh, Sean, give us a song, will you?”, and Sean said, "O'course I will," and someone else sat down at the piano and Sean sang Christmas carols for us for a half an hour or so, and I was reminded of James Joyce’s great short story The Dead, which also took place around Christmas time in a musical setting with snow falling over all of Ireland.

The next morning, standing outside waiting for Conway to take us back to the airport, there was no snow, but there was the smell in the air of coal being burned, a smell that I loved because it took me back to my childhood, to Sault Ste. Marie, Michigan, where we had lived for three years when I was a boy. And amongst those memories, I tried to imagine how a place like Mogadishu, and a place like Shannon, could both exist at the same time, and how one could hardly be any worse off, and the other could hardly be any better.

Amazing

I just got back from a week of skiing at Snowbird, Utah with some of my old friends from the East Coast—my “ski buddies,” a bunch of guys who regularly meet to ski together. Since our abilities and interests vary somewhat (and ages, too, I’m the oldest of the bunch, which tells you something about where my interest and ability level is relative to theirs), we sometimes go off on our own for awhile. That was just what I was doing, cruising along on one of the easy “groomers” (a slope that has had the bumps smoothed out of it), when two guys wearing similar yellow parkas stopped beside me. They turned out to be mountain hospitality agents, which is something like a Wal-Mart greeter on skiies, and we chatted a bit, and when we got to the part where they asked me what I did, I said I was a retired airline pilot. One of them said, “No kidding? What a small world. This guy here [the other guy in yellow] is an airline pilot too.”

“Really,” I said, “for what airline?” He said, “Continental. How about you?”

I said, “ATA. You have some of our airplanes. We sold you several of our '300s' [a Boeing 757-300, the stretch model] during our bankruptcy.”

“I know,” he said. “I’m on the 757/767. We’ve probably flown the same airplane.”

“Amazing,” I said.

“Want to ski a run together?”

“Sure,” I said. And then they showed me a way down the mountain that I hadn’t known about.

And the other guy in yellow, the one who asked me what I did, turned out to a helicopter pilot and had air lifted most of the lift towers in place years before when Snowbird was being developed. You never know who you’re going to run into on a ski slope.

Engines, More or Less

Most aircraft today have either one or two engines, but it certainly hasn’t always been that way. Historically, the number of engines has corresponded inversely with engine power: the less powerful the engines, the more needed. The B-36 bomber, the first intercontinental strategic bomber, had 10 engines, six huge Pratt & Whitney R-4360 Wasp Major engines, the most powerful and complicated reciprocating engines (recips) ever produced in any significant numbers, supplemented by four jet engines, two on each wing tip. As a young corporate pilot I used to fly with a captain, Richard Howland, who flew B-36’s in the Air Force. He said they almost never came back from a mission with all the engines still running, and often had more than one shut down. The B-52, the successor to the B-36, had eight turbojet engines. The eight engines were not there for redundancy, but because it needed that many to power it given the engines available at the time. .

Pilots love to argue the merits of different numbers of engines, but the fact is there is no right or wrong answer because the number depends on two variables, power required and reliability, and the two are interrelated. As a generalization, most larger general aviation aircraft have two engines because they need that many to be adequately powered. Whatever redundancy results from having more than one engine is secondary, and marginal—better than nothing (except at very slow speeds, where, unless the control response is precise, the remaining engine is often more liability than asset), but not much better. The Beech 58P Baron, a high performance, pressurized twin, is powered by two 325 hp engines, for a total of 650 hp. There are no reciprocating engines currently in production capable of producing that much combined power, hence two. (More powerful recips were made, like the Wright Cyclone shown in a previous post, Gone Wrong, and the R-4360 Wasp, but they have all been replaced by turbine engines.) The most powerful reciprocating engine still in production is the rare and exotic Continental GTSIO-520, a geared monster producing 375 hp. The more commonly available Lycoming 540, the engine that powers the pressurized single engine Piper Malibu Mirage, produces 350 hp. The Beech Baron needs 650 total hp because it weighs 4500 pounds empty and grosses out at 6200 pounds versus less than 3000 pounds empty and a gross of 4300 for the Malibu. There is no way the Baron could replace its two 325 hp engines with a single, existing reciprocating engine and perform adequately, and conversely, the only way the Malibu can carry any more weight would be to replace its single engine with twin recips (or with a turbine engine, which, when done at the factory makes it a Meridian, and when done by retrofit makes it a turbine Malibu). The Baron has two engines because it needs two engines, and the single reciprocating engine Malibu can’t carry any more than it does because it doesn’t have the power to do so.

But, here’s the catch: As engines are tuned to extract more power, they also tend to become less reliable. Common ways to extract more power are to reduce weight and to increase temperatures, often in the form of turbocharging. Turbochargers are nothing more than exhaust driven turbines, operating on the same principle as turbine engines do, except instead of using the turbine to drive a fan or prop, the turbine drives a compressor, increasing the air available for combustion. (Turbine engines also drive compressors, an essential component of their operation.) A byproduct of compression is heat. Weight reduction and heat both lead to less reliability. So to a certain extent you add a second engine not for redundancy, but to reduce the demand for power from those engines and, hopefully, make them be more reliable. So, paradoxically, part of the reason for the second engine is to ensure you never need it.

Early jets, the Boeing 707 for instance, had four engines because the early jet engines, straight turbine engines without a fan, did a better job of converting jet fuel to noise and smoke than they did power. They needed four engines to be powered adequately. But they also were tremendously more reliable than the recips they replaced. So while the four engines provided multiple redundancies, it was seldom needed. The four engines were there mainly for power, not failures.

Adding fans to jet engines not only made them more powerful, but also made them quieter and more efficient. In fact, engine designers quickly figured out that the fan was the component that had the greatest potential for increasing power, and each new generation featured bigger fans with higher bypass ratios—the ratio of air going around the hot section to the air through the hot section. A beneficial byproduct was sound reduction: the cold bypass air muffled the scream of the hot air coming from the compressors and turbines. And with increased efficiency came cleaner burns, which meant less smoke.

Among the first aircraft to benefit from fan jets were the Boeing 727, 737, and the Douglas DC-9. The 707 was also retrofitted with fan engines. The smaller aircraft, the 727, 737 and the DC-9, didn’t need four engines to be adequately powered, and started what would become a trend in airliner design continuing today: fewer and fewer engines. The 727 was, as far as I know, the first three engine aircraft since the Ford Trimotor. Larger, more powerful engines with big fans, the Rolls Royce RB211, for instance, made it possible to design large, wide body aircraft with just three engines, aircraft like the DC-10 and L-1011. Then Airbus, with the A-300, introduced a wide body aircraft with only two engines, and, while controversial at the time, established the trend for virtually all airliners thereafter.

Two things made all of this possible: power and reliability. You have to have both if you want to reduce the number of engines, and the modern, high bypass turbofan engine does that. The very largest aircraft, the 747, the C-5, and now the Airbus 380, still have four engines, for the usual reasons, but as far as I know there is no reason even larger and more powerful engines can’t be developed allowing even super sized aircraft like these to be powered with just two engines someday.

So, how safe is all of this? I have to admit that after almost 15 years of flying nothing but three engine aircraft, the Boeing 727 and the Lockheed 1011, I was skeptical about flying two engine airplanes over long stretches of water—what the FAA calls ETOPS, for Extended Twin Engine Operations. (ETOPS is also jokingly said to stand for “Engines Turn Or Passengers Swim.” It’s funny the first time.) Even though turbine engines almost never quit, I loved knowing I could lose one and still have two left, and I also loved knowing I would still have at least two generators, two engine drive hydraulic pumps, two sources of air and so on. I say, “at least” because the center engine on the 1011 had two engine driven hydraulic pumps, meaning I had the same hydraulic redundancy as a four engine aircraft as long as it was a wing engine that failed. And if the center failed (which it did once for me, see previous blog Gone Wrong) I would be down to two engine driven pumps, but that was what two engine aircraft started with. And I loved knowing that if one of those engines did fail over water it would be a huge non-event: just descend to a lower cruising altitude and continue or turn back, depending on the ETP (see previous article Equal Time Point Considerations). A little bit scarier was thinking about losing another one after that, because then you would be down to your last engine and your last set of fully functional engine driven systems, and fuel remaining could be critical if you had to cruise for any length of time on a single engine, but it could be done, and it was a whole lot less scary than thinking about losing a second engine on a two engine aircraft.

So it was with less than full enthusiasm that I transitioned from the 1011 to the Boeing 757/767. (The 757 and 767 cockpits are identical, except that you step down into the 757 and step up into the 767; the type rating allows you to fly either). But it didn’t take me long to get over my misgivings. The 757/767 has multiple system redundancies, even with just two engines: power transfer units, ram air turbines, hydraulically driven generators, an auxiliary power unit with an electric generator unit identical to that on each of the engines, and so on. But what made it most easy to accept was that not only did the engines always work, but the systems themselves always worked. The 1011 was (I should say “is,” but there are only a few left) an incredible airplane, but it was complex and fussy: little things were always going out on it, usually nothing serious because it was so well designed with so many backups, but many nuisance failures nonetheless. The trip without a “write up”—something for maintenance to fix—or the log book without a deferral—something minor that had been deferred for a short period of time, usually long enough to get it back to a maintenance hub—was rare. The Boeing, on the other hand, just didn’t have failures. It was a much simpler aircraft, much less complex, but rugged: “If it’s a Boeing, it’s going.” The 1011, on the other hand, loved the gate, as they say. Once you could get all those little problems squared away and get it in the air, it was your castle: nothing could touch you. But it would often be sitting at the gate, or on the ramp, long after all the 757s had departed.

So I came to trust, and even love, maybe not in the same way as I did the 1011, but still respect and admire, the 757. It proved itself to me by never letting me down for many hours over many miles of ocean. And the other two engine aircraft flying today, the Boeing 737 and 777 and the entire Airbus family except for the 340 and the 380, do the same thing every day. Because of that record of reliability the FAA now allows two engine aircraft to be flown for as many as 180 minutes away from a suitable airport at single engine cruising speed (and for as many as 207 minutes in the Pacific, three hours and 27 minutes), meaning they can fly virtually any route they want in the world without having to deviate to stay within range of suitable airports. (Specific ETOPs procedures apply, but mostly they just mean everything has to be working—generators, hydraulic pumps, Flight Management Systems, etc.—to be dispatched at the 180 or 207 minute limit.) The FAA is saying, in effect, we don’t expect these aircraft to lose an engine very often at all, and when one does fail we don’t expect the remaining engine to fail in the three hours or so it takes to reach land, ever. (The actual requirement is to demonstrate a shut down rate better than one in every 50,000 hours of flight.) If you can expect an engine to fail less than once in 50,000 hours, it is pretty safe to say that that engine is probably not going to fail during the three hours it takes to fly on one engine to a suitable airport.

Which raises an interesting paradox about probabilities. The odds of pitching a coin and having it come up heads 100 times in a row are astronomical—virtually impossible. But, assuming you have already tossed the coin 99 times, and it has come up heads all 99 times, the odds of pitching heads again on the next pitch are still 50/50. The past record has no bearing on the next outcome. It seems impossible, but it’s true: the fact that it is so difficult to throw 100 heads in a row would seem to tell you that that the odds are getting worse with every toss that comes up heads, but the odds on each toss are still 50/50. The coin doesn’t know. And the odds of losing the second engine are the same as the odds of losing the first: very low, but the same. If the odds were one in 50,000 of losing an engine, either engine, then having lost that engine the odds remain one in 50,000 of losing the second one too.

But wait, you say, doesn’t having two engines give you two chances to lose one? Yes, of course, but each has the same one in 50,000 chance, there are just two of them. The remaining engine doesn’t know the other has failed, any more than the coin about to be tossed knows you just threw 99 heads before it. Flying along for three hours on one engine may sound scary, but the odds that it will fail during that three hours are the same as the odds that the first one would fail in the first place: 50,000 to one, in our example. Nonetheless, human nature being what it is, my guess is that despite having flown thousands of hours in a two engine aircraft before a single engine failed, it would still be a very long and anxious three hours flying on that remaining engine, no matter how many times you told yourself that the second one was no more likely to fail than the first one was. The one that just failed.

Which brings us full circle to the question of the single engine Malibu versus the twin engine Baron—or any other single engine aircraft versus any other light twin. We said that the number of engines always revolves around two issues, power and reliability. The power issue can be solved fairly easily, as long as money is no object. We can increase the power available for the single by replacing the recip with a turbine; we don’t have to add another engine.

So power isn’t the question anymore, we just have to replace the recip with a turbine—exactly what the airline industry and the military did in the ‘60’s and ‘70’s, replacing all of their reciprocating engine aircraft with turbine powered aircraft. Which leaves reliability. And there again the answer is very simple if money is no object: replace the recips with turbines. I don’t have exact figures, but there isn’t any question that turbine engines are more reliable than recips—a lot more reliable. (They also cost a lot more, but that’s another issue that we will get to later.) The reasons are several, but the most obvious is that the turbine engine, even in its turboprop form, is many times simpler than a recip: all the pieces go around in circles, the fuel and air are dumped into a combustion chamber that has continuous, self sustaining combustion, there is no intricate valve or ignition timing involved, no carburetors or magnetos to adjust, and reciprocating motion doesn’t have to be converted to rotary motion. The one thing a turbine engine has to do that a reciprocating engine doesn’t is sustain very high temperatures. That turns out to be a pretty simple problem to solve, though, compared to those for a recip anyway, it just takes money. The metals necessary to withstand those temperatures are very, very expensive. Which is why we still have recips.

For an easy way to see the difference between recip reliability and turbine, compare times before overhaul (TBO) for each. Reciprocating engines typically have recommended TBOs between 1200 and 2000 hours, and require regular maintenance in between, usually on a 100 hour in service schedule, and still often don’t make it to TBO. Turbines typically have TBOs between 3000 and 4000 hours, with minimal maintenance in between, the only major service being a hot section inspection at the mid point for cracks. And they almost always make it to TBO. Turbines are also lighter (for a given amount of power) than a comparable recip, have less vibration and are often quieter. Finally, they burn jet fuel, which is not only cheaper than avgas, but much more readily available (and always will be, whereas avgas, while not an endangered species, is a very small part of refinery production and is no longer universally available). So for all kinds of reasons, turbines are the way to go, if you can just get past that initial cost. (Recips do have one advantage over turbines, and that is that they burn less fuel, but not much less, and that fuel still costs more, so the result is close to a wash.)

So we’d all love to have a turbine engine in our general aviation single or twin, but, of course, money is a factor, and replacing a recip with a turbine can be a prohibitive expense. Assuming we are staying with reciprocating engines, what about this single versus multi thing? To answer that question intelligently, I think we have to start with an acceptance of the relative lack of reliability of reciprocating engines: we may be able to show that turbine engine failures are so rare that we can assume we will never have two fail in a three hour period, but we can’t assume that same degree of reliability with recips. Recips will fail, with much greater regularity than turbines do, and we have to take that into account.

So does that mean that if we are going to fly with recips that we have to have two of them? What about the accident rate for multiengine aircraft, and their miserable performance on one engine? Aren’t we sometimes better off in a single, even if we do accept the fact that it could quit at any time and leave us with no alternative to an emergency landing?

And I think the answer is, “Yes,” sometimes we are better off in a single, or more specifically, some pilots are better off in a single, and some pilots are better off in a twin, depending on their training, experience, proficiency, and currency. A well trained, experienced, proficient, and, perhaps most importantly, current pilot—meaning he or she flies a lot and at regular intervals—will always be better off in a twin than in a single. The single engine performance may be very marginal, even close to nil shortly after takeoff, but it will still be something, and something is always better than nothing. But without good training, and a lot of flying experience in general, and without proficiency at keeping a twin engine aircraft upright on one engine and currency in flying that aircraft, he or she is better off taking his or her chances in the single. Those chances can be improved considerably by careful planning and good judgment: using airports with multiple emergency landing sites, using the longest runways at those airports, and, once airborne, keeping a continuous tally of suitable airports within range and adequate emergency landing sites when out of range, flying around mountainous areas and large bodies of water, flying as high as is practical to increase gliding range, avoiding areas with low ceilings, all are ways to increase your chances after an engine failure, meaning your chances could be pretty good. If you can’t handle a twin engine airplane on one engine really, really well, you’re better off taking your chances on your gliding skills than on your engine out skills. Because when you lose an engine on a single engine airplane, you have one very simple task ahead of you and that is to find some place to land. But when you lose an engine on a twin engine airplane, you have a beast with a mind of its own that will turn on you unless you do something to control it. Single engine safety is only as good as the planning and judgment that goes into it, and multiengine safety is only as good as the pilot flying it. And that’s the long and short of it, more or less.

Gone Wrong

Wright nine-cylinder Cyclone engine, as installed in a North American T-28 Trojan. Photograph taken at AirVenture 2007, the Warbird Flight Line, Oshkosh, Wisconsin.

“England and America are two countries separated by a common language.” George Bernard Shaw.

“Have you ever had an engine gone wrong?”

The question was asked me by a young boy, 10 years old or so, in the cockpit of an L-1011 while on the ground in Manchester, England. We had just completed a night time crossing from Orlando, Florida, a regular charter run for ATA at the time, ferrying Brits back and forth “on holiday” to the sunny South. We still had one more leg to go, Manchester to London Gatwick, and as was common, had invited the kids going on to Gatwick to visit the cockpit while we were on the ground.

The kids were excited, of course, because they were going back home after a fun vacation. The questions came thick and fast. “What does that do?” “How do you know what all these things do?” “Is it hard to fly an airplane?” But, “Have you ever had an engine gone wrong?” was a new one.

“Gone wrong,” I thought. You mean, like get into drugs? I didn’t say that, of course, but that’s what I was thinking. “That was a good engine until it started hanging around with a bunch of recips.” How could an engine go wrong?

So I did the only sensible thing and said, “Could you ask that question again?” And he said, “Have you ever had an engine gone wrong?”

Right. Probably shouldn’t ask again. So I said, “Do you mean fail? Have I ever had an engine failure?”

“Yes,” he said.

“No.” And at that point I hadn’t. I probably had 7000 or 8000 hours of flying at that point, most of it in multiengine jets, and had never had an engine failure. In fact, I’ve only had one in my entire career, and except for the fact that it occurred on Christmas Eve, ironically departing Orlando (but for Boston, not Manchester), that failure was a simple affair, losing the center engine on a very lightly loaded airplane in good weather at 1000 feet. We shut it down (it was vibrating severely and probably was about to come apart), told the tower we had an engine shut down and needed to come back, circled around and landed. Spoiled Christmas for a very disappointed crew of 12, but it was a big non-event otherwise. Modern turbine engines, unlike their reciprocating ancestors, seldom fail, and when they do it usually is without too much drama.

He said, “Thank you,” and that was that. Then another kid said, “I miss my cat.” With kids, it’s not always about airplanes.

Bardufoss

As the days get shorter, I’m always reminded of a trip I made to Bardufoss, Norway. The trip itself was an interesting one. We picked up a company of army reservists from Augusta, Georgia (the closest I’ve ever gotten to The Masters) who were deploying for several weeks of winter warfare training in northern Norway, above the Artic Circle. It was March, which doesn’t sound like winter, but Bardufoss is surrounded by mountains, it sits at the end of a fjord, actually, way up in the very northern part of Scandinavia where Norway, Sweden, and Finland all come together. It may have been March, but it definitely was still winter.

Since it was March, the days were fairly long, close to the 12 hours a day of daylight that the entire world experiences at the spring equinox. But I was curious what it was like to live in Bardufoss in the winter and summer since I knew it had to have several days of total darkness each winter and an equal number of midnight sun days in the summer: The Artic Circle is the line of latitude, North 66 degrees, 33 minutes and 39 seconds, that experiences one day of total darkness and total daylight per year. Bardufoss was above that at North 69 degrees 3 minutes and 21 seconds, so it had to have at least one full day of light and darkness each year; I didn’t know exactly how many such days they would have two and half degrees or so above the Artic Circle, but guessed three or four.

What really made it interesting to me was that Bardufoss otherwise seemed like a perfectly ordinary Norwegian village. I don’t know what I was expecting exactly, not igloos for sure, but maybe something more like Greenland or Labrador—something very basic and utilitarian. But it wasn’t. There was a pizza shop and a video store and a nice hotel, the one we stayed in, and the houses were very attractive, modern Scandinavian homes. The kids ran around outside after school dressed in standard European/American outdoor gear with colorful Norwegian touches. We could have been in Minnesota. All very prosperous, clean and healthy. Yet these people lived for a long time with very short days, including several non days each year, and also for a long time with almost no nights, including several when the sun never fully set.

So I cornered the handler—the local agent assigned to handle our flight the next day, I think we went on to Ramstein Air Base in Germany—and asked him how many days a year they had of total darkness in Bardufoss.

“Days?” he said.

“Yah, how many days of total darkness do you have here each year?”

“It’s more like months,” he said.

“Months?” I said. But you’re only a few degrees above the Arctic Circle.”

“That may be, he said, “but the mountains block out the light for several hours after sunrise and before sunset, and even with the sun not completely setting we don’t see it here. It’s dark for months here in the winter.”

“But,” I said, “here we are in March with 12 hours of daylight and just a short while ago it was completely dark. That’s a lot of change.”

“Yes,” he said, “the length of the day changes by about 10 minutes every day, longer or shorter. You notice a difference from one day to another.”

“So what’s it like to live like that?” I asked.

“It’s just the way it is,” he said.

We didn’t get into Daylight Saving Time. It didn’t seem appropriate.

Weight and Balance, Form and Function

Do we have to? Weight and balance? Could anything be more boring?

Actually, yes, quite a few things are more boring than weight and balance. The guest book at any B & B, for instance: “Loved it! Can’t wait to come back! And the bran muffins—delish! And those charming people from Montana! Who would have known there was so much to know about macramé!” As Charlie Brown would say, “Ahhhhhhhhhhhh…!”

In aviation, the most boring subject I know, one which general aviation pilots are normally spared but no commercial pilot ever makes a clean escape from, is the annual, mandatory “hazmat” training—hazard materials. It didn’t make any difference in our case that the ATA General Operating Manual—The GOM, “The Law”—stated very clearly that, “ATA will not transport hazardous materials,” we had to sit through it every year anyway. Weight and balance is practically exciting compared to that. And at least it has relevance for all pilots of all aircraft. But why does it have to be so difficult and tedious? Isn’t there some way to make it simple? And halfway interesting?

“Simple” may be a stretch, but a lot simpler is certainly possible. And halfway interesting ought to be possible once an important aspect of weight and balance is understood: the importance of weight and balance is directly proportional to the complexity of the aircraft. If you want to fly fancy airplanes, you better be ready to deal with weight and balance. It’s pretty hard to get a Cessna 150 out of balance, for instance: there are only two seats, side by side, with a limited baggage area behind them. As long as you observe the weight limits, the balance will pretty much take care of itself. But as soon as you start adding rows of seats and external baggage compartments, the complexity begins. And it gets really complex when you sweep the wings and put the fuel in both center and wing tanks. Because then you have to consider the shift in CG—the center of gravity—as fuel is burned off. (In a straight winged airplane, unless you have a fuselage or tail tank, something not very common in general aviation, the fuel is all pretty much at the same balance point.) Balance reaches the ultimate in complexity when you go supersonic, because the supersonic shock wave causes the center of lift to shift as well, which means that the CG has to shift to counter the shift in lift—a kind of moving target.

I was lucky enough to get into the cockpit of the Concorde twice, once on the ground in Papeete, Tahiti, and once in the air as a passenger flying from JFK to LHW (London Heathrow). The first time I was flying an L-1011 on an around the world luxury charter and we had landed in Papeete. (The passengers went on to Bora Bora for several days.) An Air French Concorde landed right behind us, doing a similar kind of charter. Both crews were curious about the others’ flights and aircraft, and we exchanged visits. Two things struck me about the Concorde cockpit: one, it was really narrow and long, and two, most of it was just like any cockpit: the same instrumentation, the same wear marks on the panels from fingers and feet, the same Jepp charts folded up and stuck between the panel and the windshield, the same stained, empty coffee cups, the same pencils stuck in improvised holders, and so on. A very exotic airplane, and still so much the same.

The cockpit is narrow for obvious reasons, but it is long because it is an extraordinarily complex aircraft requiring a very large flight engineer’s panel, and the only way to fit a panel that large in a narrow cockpit is to make it long. The cockpit is almost tunnel like, and the flight engineer slides along a rail to go from one end of his panel to the other.

On the second occasion, I got to visit the cockpit enroute for a few minutes, got to chat with the pilots, and got to see the flight engineer in motion. As we all know, the Concorde burned a tremendous amount of fuel, nearly as much as a 747 in fact (while carrying one quarter as many people twice as fast). To carry that much fuel it had to store it all over the aircraft in many different fuel tanks, and to keep the aircraft in balance as it flew along at Mach 2.2, the flight engineer had to constantly keep switching fuel tanks, and by constant I mean every few minutes or so. Keeping the aircraft in balance was clearly as critical as monitoring the fuel reserves themselves, and I only spent a few minutes in the cockpit because it was clear to me that there was very little time for chit-chat—the captain sat sideways the whole time watching the panel and making comments to the flight engineer as the flight engineer slide back and forth on the rail switching tanks.

This is an extreme example, but the lesson here is clear: if you want to fly bigger, faster, more exciting airplanes, and every pilots does, you have to also deal with some pretty unexciting stuff like weight and balance as well. It just goes with the territory, like sitting through “hazmat” once a year goes with being an airline pilot. So, if we can’t ever make it really interesting, can we at least make it easier? Yes, I think we can, and there’s an even bigger payoff than convenience when we do that, but I’m going to leave that note for last. First, easier.

There is no requirement under Part 91 to calculate the weight and balance prior to every flight, but that doesn’t mean you still don’t have to observe the limitations. FAR 91.9 requires the pilot to observe all operating limitations as set forth in the approved aircraft manual and all placards, which includes observing the weight limitations—which can include max ramp, max takeoff, max landing, and max zero fuel weight—as well as the balance limitations which will be expressed in terms of inch-pounds of moment within an approved envelope. (That’s just an engineer’s way of saying that the aircraft has to be balanced for and aft within a specified range on the wing.) How you determine that you are operating within those limits is your business, but if the FAA checks you and you’re wrong, that’s a violation: “That will be $1000.00, thank you, and I’m pulling your license until you show me you have received additional instruction in both Part 91 and weight and balance procedures. Then, you will have a chance to demonstrate your new knowledge in the form of an oral examination from an FAA examiner.”

Commercial pilots operating under Parts 135 (air taxi) and 121 (air transport) are required to have an approved method of computing weight and balance, to be trained in that method, and to demonstrate prior to every flight that the aircraft is within limits. Having an approved program doesn’t, of course, guarantee that the aircraft will always be operated within limits, as was shown in a previous post, Fish Story, but it goes a long way.

General aviation, freed from the requirement to have a weight and balance program and from having to demonstrate prior to every flight that it will be operated within weight and balance limits, doesn’t have that level of assurance. Still, most aircraft are operated within limits most of the time, for the simple reason that most of the time general aviation aircraft are operated with less than full loads of people and bags—there is an automatic margin of error built in if you keep the load down and put the people that do go in the front seats and keep the baggage weight down.

And most pilots know this because just about the first thing any pilot does when he gets a new airplane is run a few sample loading scenarios to see, with full fuel (which is the way almost all general aviation aircraft are flown), at what point he starts to get into trouble with weight. Then, usually with the help of the instructor who is checking him out on the new plane, he runs some bag loading scenarios to see when out of balance starts to come into the picture: does the airplane easily become nose heavy or tail heavy, is bag loading only an issue at the heavier takeoff weights, or is it an issue any time? He then has in his mind a range of “normal” loads that he knows will be within limits, and so he knows he will not have to actually compute an exact weight and balance prior to those flights. As long as the loading is normal, or average, the FAA can check him anytime it wants, because he knows he will be within limits. And if the load is heavy, lots of passengers, lots of luggage, or unusual in some way, a heavy box that will only go in the nose compartment, for instance, then, of course, he will do a weight and balance computation and make sure it is within limits.

Well, as they say, “That’s his story,” anyway, “and he’s sticking to it.”

And in many cases, it is okay. In the airline business, we had to do a W&B before every flight, even ferry flights (moving an empty airplane from one place to another, often at the beginning and end of a charter flight to and from its base). The only variables with ferry flights were the number of crew, i.e. were you taking flight attendants with you or not, and the amount of fuel. Neither had any real impact on the weight or the balance, even with full fuel, but we had to do it anyway. The general aviation pilot is spared this chore; if he wants to go fly his airplane by himself, even with full tanks of fuel, he knows that will be okay without having to do a full W&B. And at the other extreme he knows he can’t fill all the seats, max out the baggage compartments, and still fill the fuel tanks; if he does, he knows it will be over the max takeoff weight limit by a bunch, and forget about the balance. “Game over,” as the Brits like to say. But what about all the loading possibilities between a single pilot with full fuel, which we know will be okay, and full load which we know won’t be okay? How safe is it to ignore W&B computations for what we consider to be “normal” loads?

And the answer has to be, not really very safe. The FAA requires W&B to be computed for every commercial flight for just that reason. And general aviation probably should too, and would if there were a quick, simple, and easy way to do it. So let’s look at a couple of ways of doing that.

What we know we’re not going to do is refer to a basic weight and balance manual and look up a bunch of moments using difficult to read graphs with a bunch of numbers up one side and moments, divided by 100 just to keep it confusing, for each passenger, baggage compartment, and fuel tank, along the bottom. We’re about as likely to do that before every flight as we are to start going to the gym and working out with a former Navy Seal instructor every day. For starters, that sort of leg work should have been already done in the form of a chart that lists weights in convenient intervals, often 10 pound intervals, with corresponding moments, for each loading possibility—front seat passengers, second row passengers, front baggage, rear baggage, main fuel tanks, any aux fuel tanks, etc. That way we can eliminate a lot of crossed eyes trying to read up this scale, over to that line, then back down to this scale; instead we just go down the chart, round up to next highest weight as necessary, and read the moment beside it.

Many manufactures provide these charts in their weight and balance documentation. The example I use here is a generic one, but if you look closely it bears a striking resemblance to the Beech 58P Baron. (I can’t copy actual charts from manuals without running into copyright violations, but this example, while generic, is very real world.) The example used here is a twin engine aircraft with main wing tanks, front and rear baggage areas, with two seats up front and club seating for four behind. Loading wise, it’s a fairly complex aircraft, which makes it a good example.

Weight and Moment Tables
CREW/PAX
Weight		Front row		Middle		Back row
0
100		75		111		152
110		82		122		167
120		90		133		182
130		298		144		198
140		105		155		212
150		112		166		228
160		120		178		243
170		128		188		258
180		135		200		274
190		142		210		288
200		150		222		304
200+: Add amount over to 200
BAGS/CARGO
Weight	Nose		Aft cabin
0
10	2		18
20	3		36
30	5		54
40	6		72
50	8		90
60	9		108
70	11		126
80	12		144
90	14		162
100	15		180
110	17		198
120	18		216
130	20
140	21
150	23
160	24
170	26
180	27
190	29
200	30
210	32
220	33
230	35
240	37
250	38
260	40
270	41
280	43
290	44
300	45
FUEL
Gallons	Weight		Mom/100
0	0		0
10	60		46
20	120		92
30	180		140
40	240		189
50	300		238
60	360		288
70	420		338
80	480		388
90	540		439
100	600		489
110	660		539
120	720		590
130	780		641
140	840		692
150	900		743
160	960		793
170	1020		845
180	1080		899
190	1140		953

If you fly an aircraft that only has graphs, you will have to make tables like these from those charts: read up the left scale to 10 pounds, over to the first line, which is probably front seat passenger, then down from that line to the bottom scale for the moment for that position and weight. Back to the left scale for 20 pounds and so on—a tedious chore, but a one time investment for a many year return.

Once you have tables like those above, you need a form to enter and compute the information, and, fortunately, as far as I know all manufactures supply a sample form because they all provide a sample weight and balance computation in their owner’s manuals or other documentation. A form is an essential first element in simplifying this process. An example of my design is shown here:

WEIGHT AND BALANCE FORM

LOADING
		WEIGHT		MOMENT/100
PAX	Range 100-200#, 10# incr.
Front row
Front row
Middle row
Middle row
Back row
Back row
BAGGAGE	10# increments
NOSE (300 max)
AFT (120 max)
FUEL
GALLONS	In 10 Gallon increments,

WEIGHTS
	WEIGHT	MOMENT/100
BOW	4350	3265
PAYLOAD
ZFW
FUEL
RAMP
TAKEOFF
ESTIMATED LANDING WEIGHT
BURN	WEIGHT	MOMENT/100
	0	0
LANDING	0	0

ENVELOPE
TAKEOFF WEIGHT		FWD LIMIT	AFT LIMIT
4300		3139	3634
4400		3212	3718
4500		3285	3802
4600		3358	3887
4700		3431	3972
4800		3504	4056
4900		3577	4140
5000		3650	4225
5100		3723	4310
5200		3811	4394
5300		3914	4478
5400		4019	4563
5500		4125	4628
5600		4232	4732
5700		4340	4816
5800		4449	4901
5900		4560	4986
6000		4671	5070
6100		4784	5154
6200		4898	5239

You will note that the form essentially has three parts, a loading part, a weight computation part, and a weight and balance envelope in table form. Most of it is pretty self explanatory, beginning with the passenger load, entering pax weights and moments (from the moment tables either provided or created from the chart, here we have tables provided), then the bag weights and moments for both forward and rear compartments. Then the fuel load info is entered, in gallons and pounds, and that completes the “lookup” part. This is what this part would look like for a typical trip with full fuel, four passengers (two up front and two in the rear, forward facing seats in a club seating cabin arrangement) and several bags, some up front and some in the rear:

LOADING
	WEIGHT	MOMENT/100
PAX	Range 100-200#, 10# incr.
Front row	150	112
Front row	200	150
Middle row		0
Middle row		0
Back row	100	152
Back row	110	167
BAGGAGE	10# increments
NOSE (300 max)	100	15
AFT (120 max)	90	162
FUEL
GALLONS	In 10 Gallon increments,
190	1140	953

Using the data entered in this loading section, we compute the weights in the next section. The BOW (Basic Operating Weight) and its corresponding moment is a constant and can be entered permanently on the form. (Actually, it is a constant until modified by equipment changes, such as adding a second transponder. No matter how small the change, the W&B documentation must be modified whenever a change occurs. This is the responsibility of the A&P performing the change.) The pax and bag weights are all added up with the result entered on the weight section as payload (see completed Weight section below). The same for the moments. Payload is then added to the BOW to get ZFW (Zero Fuel Weight), or weight to this point without fuel. (Not all aircraft have a ZFW limitation, but many do; the more complex aircraft, the more likely it will have a ZFW limitation. The reason is that not all weights are equal: fuel carried in the wings is easier on the aircraft, structurally, than weight carried in the fuselage.) Fuel, in pounds, is added to the ZFW to get ramp weight, or total weight prior to start up and taxi. An allowance for taxi fuel, usually provided by the manufacturer, 40 pounds in this case, is subtracted from the ramp weight to get takeoff weight. Takeoff weight must, of course, but less than or equal to maximum allowable takeoff weight.

The corresponding moments are also added together and entered on the Weight section under Moments/100, resulting in a payload moment, a ZFW moment, a ramp moment, and a takeoff moment (the amount of moment to subtract for taxi fuel is the moment for 40 pounds of fuel, 33 in this case. This is also often provided by the manufacturer. If separate ramp and takeoff limits are not provided, then the takeoff limit alone must be observed.) Here is what this portion would look like completed:

WEIGHTS
	WEIGHT	MOMENT/100
BOW	4350	3265
PAYLOAD	750	758
ZFW	5100	4023
FUEL	1140	953
RAMP	6240	4976
TAKEOFF	6200	4943
ESTIMATED LANDING WEIGHT
BURN	WEIGHT	MOMENT/100
100	600	489
LANDING	5600	4454

Assuming all weight limits have been met, the only thing left is to verify that the moment falls within the allowable envelope—that the aircraft is in balance. The easiest way to do that is again to use an envelope that is in table form, weights down one side with forward and aft limits for the moment alongside. Referring to the envelope section (shown again here), we go down the weight column to 6200 pounds, maximum allowable for this aircraft, to get a forward limit of 4898 and an aft limit of 5239. Our moment of 4943 falls within these two limits: we’re pushing the forward limit and at the limit for weight, but we are still within limits and legal.

ENVELOPE
TAKEOFF WEIGHT		FWD LIMIT	AFT LIMIT
4300		3139	3634
4400		3212	3718
4500		3285	3802
4600		3358	3887
4700		3431	3972
4800		3504	4056
4900		3577	4140
5000		3650	4225
5100		3723	4310
5200		3811	4394
5300		3914	4478
5400		4019	4563
5500		4125	4628
5600		4232	4732
5700		4340	4816
5800		4449	4901
5900		4560	4986
6000		4671	5070
6100		4784	5154
6200		4898	5239

There is one final weight and balance limit that has to be considered for some aircraft, and that is landing weight. The more complex the aircraft, the more likely it is to have a lower weight limit for landing than for takeoff. (This is actually a good thing because it allows you to take off with a higher gross weight than you could otherwise.) This is just one more simple calculation, but it does assume that the flight has already been planned with an estimated fuel burn for the trip. Landing weight is then just takeoff weight minus the fuel burn weight and landing moment is takeoff moment minus the moment for the fuel burned. Landing weight must be lower than the maximum landing weight limit and the moment must still fall within limits for that weight. Actually, if the aircraft was within limits for takeoff and lands within limits for landing, the landing moment will always also be within limits because the FAA will not allow an aircraft to be certified that can go out of balance as fuel is burned off (but it may require that specific fuel management procedures be followed. Such was the case in the extreme example of the Concorde, described above.) If mechanical failures or weather conditions force an early landing, an over weight landing can always be made under a pilot’s emergency authority, but a logbook write up will have to be made and signed off by an A&P after inspecting for damage. Here is what this additional computation would like:

ESTIMATED LANDING WEIGHT
BURN	WEIGHT	MOMENT/100
100	600	489
LANDING	5600	4454

This hypothetical aircraft has a maximum landing weight of 6000 pounds so it is well under the landing limit, and if we do check that weight against the envelope, we see that the for and aft limits for 5600 pounds are 4232 and 4732, so, as promised, the aircraft took off within balance limits and stayed within limits as fuel was burned off (still fairly close to the forward limit. Fuel generally has a negligible effect on balance for straight winged aircraft with fuel carried only in the wings.)

So, after all that, what have we done to make W&B easier? Actually, quite a bit. The hard part, a one time investment for a long time return, has been done: we have a simple form that flows from one section to another quite easily, and we have our weight and moment data in table form, so all we have to do is look up the appropriate weight and enter that and its moment on our form, add it all up, make sure everything is within limits, and off we go. If it were me, I would get a folder of some sort, one with a clip for my forms with a pocket or clip on the other side, and I would print up and laminate my tables and stick them on the left side with my forms on the right side, stick the folder in a pocket or in my flight bag, and then I would get in the habit of filling one out as just a normal part of my preflight.

But, there is an even easier way. The forms and table above were actually created using Microsoft Excel™, a spreadsheet program that comes bundled on most PCs. (Macs have comparable programs, but even a basic, generic spreadsheet program will do—nothing complicated or advanced is necessary.) If you’ve never used a spreadsheet program at all you may want to run a basic tutorial or get a “spreadsheets for dummies” kind of book, but I think it will be time well spent: I find spreadsheets to be extraordinarily useful, and the nice thing is you can use them for basic, easy stuff in the beginning, and then just keep adding features as you learn to use the more advanced functions. I’m not going to try to teach you how to use spreadsheets here, but I will show you, with the appropriate functions, how to set up the forms to do all the arithmetic themselves (that’s the really easy part, and where you want to start if you’re new to spreadsheets), and then how to automate them so you don’t even have to look anything up. Once you’ve done that, all you have to do is enter the appropriate weights on the form, and the spreadsheet will do all the rest. I think it’s a lot of fun to create one of these things, and pretty neat to watch it do all the dirty work.

The first step is to set up your forms on the spreadsheet, and you can be as simple and basic or as fancy as you want here, with outlines around boxes, bold titles and headings, change cell sizes to fit different data sizes, it really doesn’t matter at this point and it can always be modified later. Then you need to enter a couple of very basic formulas to get the spreadsheet to do the arithmetic. Using the form above, for instance, we can get the spreadsheet to add up the payload—the pax weighs and baggage—and enter the result in that block. The formula (all formulas here are based on Excel; others will be similar) to do this is “=SUM(C6:C15)”, and that is entered (without the quote marks) in the blank cell to the right of PAYLOAD. This simple formula tells the spreadsheet to add all the cells from C6, which is the cell I used for the first passenger weight, to C15, the last bag weight, and show it in place of the formula. (The spreadsheet ignores cells without numbers in them.) Here is what this part of the form would look like with the formulas shown: Other formulas tell the spreadsheet to enter the value from another cell in that cell, to multiple by 6 to convert avgas in gallons to pounds, and so on. All are basic formulas.

WEIGHTS
	WEIGHT	MOMENT/100
BOW	4350	3265
PAYLOAD	=SUM(C6:C15)	=SUM(D6:D15)
ZFW	=SUM(H5:H6)	=SUM(I5:I6)
FUEL	=C19	=D19
RAMP	=SUM(H7:H8)	=SUM(I7:I8)
TAKEOFF	=H9-40	=I9-33
ESTIMATED LANDING WEIGHT
BURN, GALLONS	WEIGHT	MOMENT/100
100	=G16*6
LANDING	=H10-H16	=I10-I16

With just a few very simple formulas we have eliminated all of the arithmetic which not only makes the process a lot easier and quicker, but also eliminates the errors that inevitably result either from doing the arithmetic in your head or punching incorrect numbers into a calculator. This in itself is a huge improvement over manual computation, but there is something else we can do that will automate the lookup process and turn the whole weight and balance check into a simple matter of entering the weights, and letting the spreadsheet do all the rest. To do this, though, we have to go beyond the simple functions above, but it still isn’t all the difficult, as I hope to demonstrate.

Take a look at the Estimated Landing Weight section again.

ESTIMATED LANDING WEIGHT
BURN	WEIGHT	MOMENT/100
100	600	489
LANDING	5600	4454

In this example, the flight plan burn was 100 gallons, and we let the spreadsheet convert that to pounds by multiplying that number by 6 (“=G16*6”, where G16 is the cell with fuel burn in gallons). The spreadsheet then subtracts that weight from the takeoff weight to get landing weight. At this point the spreadsheet doesn’t know what the moment is for that weight; we have to look it up and manually enter it. But there is a way to have the spreadsheet lookup the number from the table instead of having to do that yourself. The spreadsheet can do that with a function called a LOOKUP function, specifically a VLOOKUP, for vertical lookup, because that is the way our tables are set up, in vertical columns. The VLOOKUP function is a little fussy, because it has four parameters: it has to know what value to reference (600 pounds of fuel in the example), where the table is that has the necessary information, which column has the corresponding data (the moment for 600 pounds, 489 in this case), and finally whether we want it to use exact matches only, our use the next closest lower value. We don’t want it to round down—the next higher would be okay, but the next lower is not—so we will search for exact matches. Since our fuel table goes by 10 gallon increments, we will have to enter fuel burns by 10 gallon increments also, or the formula won’t work. (It will show “#N/A”) This is a little fussy, but it avoids the problem of rounding the weight and moment down, in a less conservative direction.

The actual formula to lookup the value for the moment for the estimated fuel burned enroute is:

=VLOOKUP(H16,B79:C98,2, FALSE)

where =VLOOKUP describes the function desired, H16 is the location of the data we want to reference, the fuel burned, B79:C98 describes the block of cells used to list our data, our fuel weight/moment table (it could be anywhere on the spreadsheet, I put it a page or two down), the number “2” tells the spreadsheet to look in the second column of that table (the first column lists weights, the second moments), and finally the word FALSE tells it to only use exact matches.

All of this took me awhile to figure out, and if you only used it to look up one value it wouldn’t be worth it, but we can use this basic model and modify it as necessary depending on what we want to lookup, where it is, and in which column. Once done, all we have to do is type in the weight for passenger number one in the front row and, bingo, the moment appears right beside it. No looking in tables, flipping pages, copying moments or trying to remember them and enter them on the form, just enter the weight and everything else is done for you. The same for all the other weights.

I’m not going to describe the formulas for the other moments because they all work the same: you enter the cell for the weight—1^st row, 2^nd row, 3^rd row pax weight, forward bag weight, whatever, as the first parameter, the block of cells for that data as the second parameter, the column to find the value, which would probably be the second column for the first row of seats (the first column is the weight itself), the third column for the second row, etc., and then FALSE, all separated by commas and surrounded by parenthesizes. Another one time investment for a long time return.

There are a couple of other ways to spiff up the spreadsheet, nice to have but not necessary, which I will mention only briefly, because if this is your first shot at using spreadsheets, this is enough, and if you know spreadsheets fairly well you probably already thought of them. You can use IF functions to check for limits, for instance. An IF function could be used to check the takeoff weight, and if it is over the takeoff limit could return a message that said, “Out of limits”, for instance. Otherwise it would leave that cell blank—no message—or could return a “Good to go!” message; whatever you want. You could also, and this gets really fussy, combine VLOOKUP with an IF function to have the spreadsheet look up and check that the balance is within limits: take the 6200 pound takeoff weight and check that the moment, 4943, falls within the forward and aft limits (4898 and 5239, it does), something we must do manually even now. That’s the beauty of spreadsheets: you can make them as elaborate and automated as you want, or as simple and basic as you want. It’s all up to you and the amount of time you want to put into it.

So at this point I think we can say that, even with just a basic, paper form and some laminated tables, we have made the process of computing weight and balance before every flight very feasible, and certainly with it all on a spreadsheet, very practical. You could even do it from home before leaving in many cases, because you almost always know what your loads will be at that point. Or, if you normally take your laptop along with you, you could wait to do it when you get to the airplane. There really is no excuse for not doing it though, and that brings me to what I said in the beginning about the added benefit of doing a weight and balance computation before every flight.

We know that weight and balance is important, that an overweight or out of balance airplane is a dangerous airplane, but we also know, or assume, that it usually is within limits, and we know that margins are built in, so even if it is a little out of limits, why make such a fuss about all this? I think the answer has to be something I believe very strongly in, and that is that I believe the only way to make flying truly safe, and in the process also make it easy and enjoyable, is to eliminate as many uncertainties as possible ahead of time. We can’t eliminate them all of course, and that’s part of what makes flying fun and a challenge. But to the extent we can eliminate uncertainties, we are that much better able to concentrate on those we can’t eliminate: unforecast weather, ATC variables, mechanical issues, and so on. Do you really want to add wondering whether you’re overweight or out of balance on top of that? One of the things that makes good pilots good is that they know there will always be challenges in flying that they weren’t expecting. And the best way to be ready to deal with those challenges is to have eliminated ahead of time everything else, and that includes weight and balance. Weight and balance is not the most critical part of every flight, but it is one of the easiest to deal with ahead of time and eliminate from the list of challenges. I hope this helps to make it easier, and, maybe, even a little bit of fun.