Why Twin-Props Are Screwdrivers In A World Of Hammers

twin-propeller aircraft landing
Credit: FlugKerl2/Wikimedia

My house sits in open country with a big sky overhead and two airports— one a joint military-commercial operation, the other an executive general aviation facility—nearby. The satisfying consequence is a daily air show viewed from my office balcony. 

And while participants reduced in number noticeably with the onset of the COVID-19 pandemic, there are still regular appearances by military transports, jetliners, business jets, full-throated fighters, helicopters, spray planes and even an occasional U.S. Marine Corps V-22 Osprey.

I’m happily distracted often, Bushnell monocular always at the ready. 

The other day, I spotted a light twin approaching with singularly rakish wingtip tanks. Ah! A 310. I’d not seen one of those since . . . well, I couldn’t remember when. That seemed surprising, since Cessna delivered 5,500 of them during the model’s 26-year production run. And while the last came off the Wichita line in 1981, when properly maintained, such aircraft live long, productive lives. 

Pondering that, I further realized that piston twins in general rarely join my air show, a head-scratcher considering the tens of thousands of Piper Navajos, Senecas and Aztecs, 300- and 400-series Cessnas, Beech Dukes and Barons, along with Shrikes, Aerostars, et al., the airframers produced.  

According to the General Aviation Manufacturers Association (GAMA), industry output in the 1970s averaged 2,000+ new piston twins annually. By contrast, that figure was down to 150 per year in the past decade.  

So did piston “multi-” owners and operators advance to turboprops? After all, there were plenty of those available from Beech, Cessna, Piper, Rockwell, Mitsubishi, Fairchild and Piaggio, among others. The GAMA numbers seem to support that possibility. Back in the ’70s, airframers delivered about 3,200 executive turboprop models; in the most recent decade, the total increased to 5,500, a bump of more than 70%.

However, that new, higher count includes single-engine turboprops, a category essentially nonexistent five decades ago. When you subtract those for an apples-to-apples comparison, it turns out aircraft-makers delivered just over 1,000 twin turboprops in the recent 10-year period, or two-thirds fewer than during that earlier decade. In fact, Beech King Airs are the only ones left in GAMA’s production count, and last year Textron turned out just 62 of those.  

Unsurprisingly, most former OEMs have either disappeared or simply abandoned twin-prop production altogether. Why? For myriad reasons, it appears. 

The initial assumption that two engines provide extra safety and performance was shown to be a commonly held canard by no less a general aviation advocate than the late aviation editor Richard Collins. After poring over accident data, he found little difference between most high-performance piston singles and twins in the rate of mishaps. Moreover, when properly maintained and supplied with the appropriate and sufficient fuel, engines—whether piston or turbine—rarely fail.

As for performance and systems, the newer singles pretty much mirror those of any twin counterparts. Or surpass them. Garmin’s award-winning Autoland system, for example, is so far available only on turbine singles; Cirrus equips its aircraft, all singles, with an emergency parachute. Moreover, fuel systems on twins are necessarily more complex than on singles. And should an engine fail on a twin, pilots rusty in engine-out procedures will have their hands full, whereas a lost engine on a single presents the pilot with one course of action.

And then, of course, there’s the matter of cost. Obviously, a second engine represents increased operating and maintenance expense over similar aircraft with half that number. It’s impossible to put an exact figure on the differential, but the premium can be 40% or more. Indeed, according to Business & Commercial Aviation’s 2020 Operations Planning Guide, the variable costs of a Beech King Air C90GTx versus Daher’s high-performance, single-engine TBM 940 are approximately double.

In addition, Lance Toland, a leading aviation insurance broker, reports the cost of coverage for high-end twins and turboprops is “most definitely” a factor, if it is available at all. He says many lenders require insurers to pay them for any such loss, regardless of circumstances. That “breach of warranty” provision has chilled insurers’ enthusiasm for covering those aircraft. 

Finally, one major consultant noted there are many cost-effective options available to potential twin-prop aircraft users including jet cards, fractional networks and clubs, along with competitively priced used light jets. Consequently, he says, twins have become “screwdrivers in a hammer world.”  

He characterized the “multi” segment as undergoing a “devolution,” whose turnaround is dubious . . . along with participation in my air shows.

William Garvey

Bill was Editor-in-Chief of Business & Commercial Aviation from 2000 to 2020. During his stewardship, the monthly magazine received scores of awards for editorial excellence.


I'm spending too much time contemplating a next aircraft purchase. Piston twin prices are tantalizing, but then I created a spreadsheet of estimated annual fixed and variable costs. These are rough, but looks to me as if a $450,000 twin piston Cessna 421 and a single turboprop $750,000 Piper Meridian would cost about the same to own and operate. I'd fly with more confidence behind the single turbine. But the twins still have an aura of cool to an old timer like me.
p.s. Glad to see you're still contributing! Jeff
The same reason why four-engine jet airliners have been replaced by twins.
The fact is that most of the people that used to fly twins have been priced out in this economy. Large jets have done well everything else is down.
One factor not mentioned is fuel availability. In many parts of the world LL100 is as rare as rocking horse urine, and about as costly!
Jet A1 is a different matter however, widely available and cheaper; also I believe many/most of the diesel engines certified for aviation will run on Jet A1 or 'road' diesel. And that is ubiquitous.
The main reason for light twins disappearing is the dismal safety record with misunderstood engine-out performance leading to Vmc Loss Of Control resulting in fatal accidents. The General Aviation community and the regulators need to take a good look at how pilots are trained in these aircraft. Far too many pilots are trained to think that they have a little airliner in performance and control in light twins. Unfortunately the pilots who train them are either inexperienced, have no understanding of light multi-engine aircraft performance and control due to the fact that they only understand transport category aircraft performance from the airline world and the military which is a totally different world from the light twin. As a result insurance and economics make these aircraft too expensive for the average general aviation pilot to operate these days.
Your sister publication Business & Commercial Aviation and Aviation Consumer had some excellent articles in the past about engine-out performance in light twins and since a generation or two of pilots has gone by it would probably be a good time to reprint these.