Heavy Single Versus Light Twin

An in-depth analysis of performance, cost and safety reveals that the major difference is money.

Which will it be, a heavy single or a light twin?

Our guess is this question is being asked more often than ever as the Baby Boom pilot population matures and many owners find themselves financially able to even consider the choice.

But the fact is, airplane ownership has always been a step-up game. Start out simple and cheap-a Cessna 172 or Archer-and move up to something sleek and fast.

Eventually, most owners advancing through the ranks will confront the dilemma of whether to step up to a twin from a high-performance single. And this is indeed a dilemma.

Performance and load-carrying of most twins is better than the big singles and thanks to escalating gas prices, twins are a relative bargain. But there’s always a piper (the old piper, not the New Piper) to be paid and it comes in the form of higher operating costs for a twin, including gas, maintenance and insurance.

Safetys an issue, too. For a well-trained and competent pilot, a properly loaded twin probably is a safer airplane to fly. In reality and as the accident record shows, many pilots simply arent we’ll trained and if an engine crumps after takeoff in a twin, they find themselves in serious trouble.

Why Upgrade?
Unless you have money to burn-and believe us, a twin will burn it-there ought to be a practical reason for upgrading. Setting aside ego and status, most owners look to a twin for one of several reasons or a combination of reasons.

More payload: A growing family needs more airplane to haul more stuff. Twins usually (but don’t always) deliver. Speed: In the same cabin size and class, a twin will usually be marginally faster; a Baron will outrun a 36-series Bonanza, although the margin evaporates when the turbocharged B36TC is plugged into the equation.

Safety: In theory, the additional engine does offer more options. But as the old joke goes, it may also simply get you to the scene of the crash. NTSB studies have consistently shown that engine-failure crashes in twins are more likely to be fatal than in a single-as much as four times more likely.

But thats not the same as saying twins have four times the number of accidents as twins. In fact, the reverse seems to be true. In terms of overall accidents-not just engine-failure accidents-twins generally have a better safety record than do high-performance, retractable singles, such that its possible to measure such things accurately.

The usual disclaimer applies. Accident rates are traditionally measured on an hours-flown basis. But the total hours flown by the GA fleet is a loose estimate at best and breaking it down by category and model type is a wild guess.

The last significant study the NTSB did on the subject-back when it had staff to undertake such research-was done between 1972 and 1982. That study showed that among a representative sample of 18 popular twins, the composite fatal accident rate was 1.7 per 100,000 hours of flight compared to 2.3/100,000 hours among 17 single-engine aircraft.

Given the inaccuracy of the hour estimates, a dose of skepticism is recommended. Nonetheless, its reasonable to assume that hours estimates for both twins and singles are equally suspect so the relationship may very we’ll be valid.

Since the overall GA accident rate and fatal rate has declined over the past two decades, its reasonable to assume the twin versus single accident picture has also improved somewhat.

Three Comparisons
Thanks to so-called parts-bin engineering, the manufacturers made stepping up to a twin somewhat logical. Piper used essentially the same fuselage for the Saratoga and the Seneca, Beechcraft did the same with its 36-series and the Baron.

Cessna has no derivative twin so for this comparison, we’ll use the Cessna 210 and 310, logical step-up options in our view. Neither is a cabin class, both will carry six people. (If you disagree, fine; but we need to fit this article into a magazine, not a book.)

First, new purchase price: New Piper still makes both the Seneca and the Saratoga. A new Toga II TC tops out at about $450,000, typically equipped, while a factory fresh Seneca V will invoice around $550,000 or so, a relative bargain for a new twin.

Exiting here into the real word, where airplanes are bought used, is instructive on how twins are valued in the market. A decent 1980 Saratoga SP will sell for $163,000, according to the Summer 2000 Aircraft Bluebook. The equivalent Seneca-the Continental-powered Seneca II-retails for $148,000, a price Delta of 10 percent favoring the used twin, while the new twin costs 22 percent more than the new single.

Similarly, you can still buy both a new Baron and a new 36-series Bonanza, either an A36 or a B36TC. A new Baron is hardly for the financially feint of heart, typically retailing in the $900,000 range, almost twice the cost of the Seneca V. The A36 and B36TC arent cheap either, as new singles go. Typical invoice on the A36 is about $550,000 while the B36TC typically sells for closer to $650,000.

On the used market, 1980 55 Barons hover around $198,000, compared to $188,000 for an A36 of the same vintage. Set your sights a little higher on a 58-series Baron and youre in the $250,000 range. A turbocharged A36TC (the B didnt come along until 1982) will cost you only a couple of grand more than the normally aspirated model, at about $190,000.

Cessna no longer makes the 210 nor the 310, so the only choice is used. Again, the market votes on value here and evidently, the Cessna 310 is a valuable twin indeed.

Among our comparison group, its the only used twin that sells for substantially more than a single that might logically be considered an alternative choice.

Using the 1980 model year as the benchmark, a Cessna 310R typically retails for $214,000 versus $156,000 for the equivalent year Cessna 210N, a price difference of 37 percent in favor of the single.

One thing you can bank on: The twins in these comparisons definitely are faster, although not blazingly so.

Lets look at the two Pipers first. The 1980 Seneca II, with its turbocharged Continental TSIO-360s, cruises along in the 165 to 170-knot range. Obviously, being turbocharged, it does a bit better higher, especially in the low teens.

The Saratoga SP, by comparison, cruises at 155 to 164 knots, on a bit more than half the fuel. If youre willing to opt for turbocharging in the Saratoga-not a bad option-the airplane will run within a few knots of the Seneca on perhaps 25 to 30 percent less fuel than the twin uses.Looking at the Beech products, speed variation between the singles and twins are a bit greater, but not dramatic. A 55 Baron tools along at 180 to 190 knots, burning 27 gallons an hour or so but some owners run them slower, theorizing the engines will last longer.

The A36 cruises at 162 to 168 knots, depending on loading. As with the Saratogas, opt for turbocharging in the TC version and you’ll run with the Baron at about 190 knots in the mid-teens.

Running the two Cessnas wing-to-wing will yield similar results. Most owners cruise the 310R at 170 to 180 knots, burning 26 to 28 GPH total. Baron owners like to claim even the 55 model is faster than a 310 but in the real world, the difference is too slight to consider. Cessna 210s can be counted on for 160 to 170 knots, with more owners closer to the slower number than the faster. The turbocharged version will true at 190 to 200 knots, especially if high and light.

Conclusion: In this group and in general, the twins will be 10 to 15 percent faster on roughly twice the fuel, although the fuel burn variations are less when a turbocharged single is considered. In order of most fuel economical, the B55 and Seneca are close, the 310 with its IO-520s, the thirstiest.

Handling, Single Engine
Few light twins qualify for what we call the Joy of Flight award. Like the Saratoga, the Seneca is a clunky handler, heavy in roll and variable in pitch, depending on loading. It tends toward a forward CG and thus takes a hefty tug to land well; leaving power on for additional stabilator authority helps.

The Cessna 210 can best be described as truck-like. It has heavy pitch forces and although quick in roll, it takes a heave to get it there. The upside of this is that the thing goes where you point it and stays there. Its a very stable airplane for instrument flying, even without an autopilot.

The 310 is similarly exceptionally stable and pleasant to fly in cruise and light maneuvering. But with all that fuel in the tip tanks, inexperienced pilots can virtually count on pilot-induced roll oscillations on the first few takeoffs.

Experience and technique cure this. The 310s higher-than-usual gear legs also require some adaptation and unlike the Seneca and Baron 58, it has no rear cabin door. Its a high climb onto that wing and into the cabin through a single door.

The exceptional aircraft in this group are the Bonanzas and Barons. In our view, they are clearly the best handling in terms of control harmony. Although the Baron isn’t quite as sprightly at the Bo, by dint of weight, the difference between the two is about what you would expect.

Pilots transitioning from another twin or a heavy single into a Baron often remark on how pleasant it is to fly. Like the Bos, the Baron has light control forces (for a twin) and pitch and roll are we’ll harmonized and not much affected by minor changes in CG, as with the Pipers.

The acid test for all twins, of course, is single-engine performance. You are, after all, buying into the worst case scenario, not hoping for the best. In general, this group of twins would best be characterized as not bad but not exceptional, either. In our June 2000 comparison of light-light twins, we noted that single-engine climb rates are anemic, at best. Published figures should be viewed with a raised eyebrow.

A Cessna 310s published single-engine climb varies with model but is in the 330 to 380 FPM range; turbocharged models do better, especially at higher altitudes. Given the vagaries of airplanes and pilot proficiency, a new owner could probably expect 250 FPM on one engine. The 55 Baron is about on par with those figures, while the Seneca has a published single-engine climb rate of 235 FPM.

Of course these numbers are just that, numbers. They apply to airplanes at gross weight but in perfect rig and flown by company pilots who knew the ropes. One way a less proficient owner can stack the deck in his or her favor-although few do this-is to simply fly the airplane at lighter weights. Carry less fuel and as little weight as necessary. Unfortunately, pilots who have the capability to schlep around all that a light twin will carry tend to load it up, even over gross, in which case the single-engine climb may easily sag into the negative values.

If you always operate out of relatively long runways, say 3000 feet or more with clear overruns, single-engine operations may be less of an overriding concern on takeoff. But we see real risk when twins are based on fields with short runways or with trees and obstacles nearby. Constantly operating at gross weights out of such airports tempts fate, in our view.

Range and Payload
But dear, we’ll be able to carry more in the twin.

Thats a common rationale for buying into a light twin. Under some circumstances, it is indeed true; the twins generally win out on raw payload. For example, the 1980 Cessna 210N, with a gross weight of 3800 pounds has about a 1500-pound useful load. Fill the tanks, and there’s still room to carry 950 pounds of people and baggage, a full family of four with clothes for a month. Payloads of 210s vary considerably by model year, approaching 1100 pounds in some models.

The Cessna 310Rs gross weight is 5500 pounds for a useful load in the 1800-pound range. Fill the tanks (standard 101 gallons) and youve still got more than 1200 pounds to play with. But with standard tanks and the above specified load, you might we’ll get there first in the 210, since it has a tanks-full still air range of more than 1100 miles, versus only 700 miles for the 310. The twins cruise speed doesnt wipe out the burden of its higher fuel burn.

To match the 210s range, the 310 will need 150 gallons of gas, which can be carried in the optional 207-gallon tanks. The extra gas exacts a 300-pound weight penalty-or 600 pounds if you top off-leaving the twin with a 900-pound cabin load, virtually the same as the 210.

Bottom line: In this scenario, you’ll spend twice as much on gas to carry about the same payload, give or take a few pounds. On a 600-mile leg, you’ll get there about 20 minutes sooner in the twin, thanks to the higher cruise speed.

At 1000 pounds load with full tanks, a 1980 Saratoga is a prodigious load hauler, which in part explains the models popularity. But once again, the Seneca II bests it in raw payload, easily hauling some 1200 to 1300 pounds with the tanks full of gas or six 170-pounders with light baggage.

Unfortunately, thats not much gas. Standard tankage allows 93 gallons and at 25 gallons per hour total, youre at dry tanks in 3.7 hours. At 170 knots, thats just over 600 miles. By comparison, the Saratogas 102-gallons of gas translates to more than six hours of endurance and even at a throttled-back pokey cruise of 155 knots, the Saratoga goes further and will get there first if the twin needs a fuel stop.

Among this group of three, only the 55 Baron has a better payload and range profile, and then only because the A36 Bonanza doesnt shine in this category. The Baron can haul 1200 pounds with a full fuel load of 100 gallons, 136 gallons optional. Even with the optional fuel load, the payload hovers around 1000 pounds or so, give or take. (But watch the CG.)

Among six-place heavy singles, the 36-series Bonanza is not a load hauling champion, with typical full-fuel payloads under 900 pounds. Again, not much gas: The A36 has only 74 gallons, giving an endurance of 5 hours to dry tanks for a still air range of 870 miles.

With the larger tanks-and thanks to its smaller IO-470s-the Baron can fly for 5.6 hours, with a still-air range of more than 900 miles.

Conclusion: Although it wont be true in all cases, in general, twins carry significantly more payload but because of their higher fuel consumption, the longer the trip is, the less the advantage. On very long trips, the single will probably win out on overall range.

The twin will shine on shorter trips which require hauling a lot of heavy or bulky stuff-say carting the family 300 miles to the beach house for a two-week stay. If the beach house is 1000 miles away, the twins range/payload parity may evaporate.

Operating Costs
Rationalize it all you like, but a twin is simply far more expensive to operate than a single and its not just gas and oil youre paying for. Twins have more complex systems and often have two of everything, so youre doubly exposed.

Consider the plight of a Baron owner who got hit by both recent Continental crankshaft ADs. Besides having the airplane down for many months, both engines might have been removed, dissembled, repaired and re-installed.

Although TCM picked up some of the freight, such a development is an expensive, frustrating experience. Fortunately, it doesnt happen often but high repair costs are a fact of life with twins.

Lets examine fuel costs first. Simply stated, expect to spend twice as much for gas and oil as you would for a heavy single. The actual total might be a bit less, depending on the aircraft compared.

For example, if you measure a Saratoga against a Seneca II, the Toga might burn 14 to 15 gallons per hour against the Senecas 24 to 28 gallons.

But the Cessna 210 and 310 will likely yield a two-to-one ratio-they share the same engine- and thats what you should budget for. True, the 310 will make the trip a bit faster, shaving the edge off the two-to-one ratio block-to-block. And with avgas prices inching toward a decade high, fuel costs over a years time are significantly higher than they were two years ago.

Any pilot buying into a new twin can have some inkling of the lowest end of the maintenance cost scale. It will be the cost of a flat-rate annual or 100-hour inspection. Unfortunately, the reality is that there’s no upward limit for maintenance costs. Buy a hangar queen and the cost to keep it flying could spiral ever upward, with no end in sight. Consider, for example, a 1980 Cessna 310R bought for Bluebook value, $214,000. When the engines come due, the owner will have to cough up about $38,000, give or take.

In a year when maintenance expenses are otherwise high, buying a pair of engines could easily push the cost of ownership for that year to $50,000 or more. For that matter, even a heavy single can tear into the bank account unpredictably but not nearly to the degree that a twin can.

All aircraft owners tend to underestimate true operating costs, either due to pie-in-the-sky optimism or because they just don’t accurately track-or don’t want to know-what they spend. Owners who are realistic about such things report that all-up typical operating costs for light twins are in the $175 to $250 range, with a bias toward the higher figure. However, as we’ll note in our conclusion, we don’t think this is necessarily the best way to look at the equation.

In this group of three, is there a cheap twin? Probably not. Because of high parts prices, we would say the Baron is the most expensive to maintain, the Cessna 310 next and the Piper Seneca last. A light-light twin-say a Duchess, Seminole or Apache-might be marginally cheaper to operate but it wont carry as much, wont be as fast and wont have the equivalent single-engine performance.

Peace of Mind
And last, the perceived safety argument. The word perceived is appropriate, since the safety margin of a twin over a single is elusive at best. There’s no argument that having a second engine has prevented many accidents and saved lives when one quits.

And having a second alternator, vacuum pump and the de-icing systems that some twins carry is also an undeniable plus and perhaps worth the extra maintenance costs.

The ugly side of this coin is that the pilot who botches an engine-out situation in a twin may not survive. Loss of control and Vmc rollovers in a twin are almost certain to be fatal whereas an engine failure in a single is more likely to result in a survivable if not a walk-away landing.

Distilling the twin pro and con arguments soon confronts the issue of training, both initial training for the multi-engine rating and re-current training for systems and engine-out work. For a properly trained and current pilot in a twin flown within or below its weight limits, there’s little question that the additional engine provides an edge, especially when flying over water or in low-IMC, where the prospect of an engine failure in a single sends chills up the spine.

What constitutes properly trained and current? Were not sure but its not a pencil whipped BFR and 50 hours a year. We think a serious session of multi-engine recurrency at least once a year and no fewer than 80 to 100 hours of twin time is the bare minimum.

Forget speed, forget payload, forget safety. Weighing a twin against a heavy single should first and foremost be an economic decision. The rule of thumb that a twin costs two-and-half times as much to operate as a single seems to hold remarkably true. Some might not be quite that pricey, others may be far worse.

Second, we think would-be owners should forget hourly costs and look at the annual cost of owning the airplane, to include debt, hangar, maintenance, insurance, training and fuel. Flown 150 hours a year, the typical twin can consume $8000 worth of gas alone. Add up everything and your annual expenditure can easily exceed $30,000 in actual cash outlays, even in a year when engines don’t come due.

Only if such lofty numbers sound doable should you then consider the performance and speed pros and cons and the ever intangible perceived safety factor. If you can easily afford it-including the training-there’s nothing quite like having a fist full of throttles. But if the dollars are a pinch and you don’t fly but 50 hours a year, stick with the heavy single.

Also With This Article
Click here to view charts for Price, Cruise Speeds, Payload and Range.
Click here to view Hard Specs.
Click here to view the Checklist.
Click here to view “Insurance: Plan on Doubling Your Premium With Lower Limits.”