Stats for Multi vs Singles- Engine Failure rate

[Jaybird180]

I'm not trying to start a shouting match here, but I'd like some real-world data to backup the assertions I've heard that twins are safer than singles.

I hypothesize that the failure rate for an engine in a twin is higher than the failure rate of singles. Given that however, unfortunately I theorize that given the same failure rate we are likely to see higher injury rate in singles due to training and lack of options that the pilot of the mutiengine may have at his disposal.

I hypothesize that engine maintenance in personally owned singles tend to be deferred more often because of the idea that they have two.

 

[Jim Logajan]

I'm not trying to start a shouting match here, but I'd like some real-world data to backup the assertions I've heard that twins are safer than singles.

I hypothesize that the failure rate for an engine in a twin is higher than the failure rate of singles. Given that however, unfortunately I theorize that given the same failure rate we are likely to see higher injury rate in singles due to training and lack of options that the pilot of the mutiengine may have at his disposal.

I hypothesize that engine maintenance in personally owned singles tend to be deferred more often because of the idea that they have two.

I believe this article addresses the points you bring up:

http://www.avweb.com/news/usedacft/182809-1.html

He discusses safety, operating costs, maintenance, reliability, and so on of twins versus high performance singles; here is what he says about safety (but read the whole article) :


"I recently finished editing a Cessna 310 safety review for the AOPA Air Safety Foundation. In the course of this project, I took an in-depth look at the safety record of the Cessna 310 and a group of comparable aircraft (Aerostar, Aztec, Baron, Commander, Crusader) during the eleven year period from 1982 through 1992. Some interesting statistics emerged from this study.
The overall accident rates of high-performance singles (like Bonanzas or 210s or Mooneys) and light twins (like Aerostars or Barons or Commanders or Cessna 310s) are astonishingly close. Twins have a slightly higher accident rate per 100 aircraft and a slightly lower accident rate per 100,000 hours, but for all practical purposes the accident rates are the same. The same is true if you consider only "serious" accidents that involve death, serious injury, or substantial damage. For both high-performance singles and light twins, approximately one-third of all accidents are classified as serious.

For both singles and twins, roughly three-quarters of all accidents are classified as "pilot caused". While weather-related accidents dwarf all other pilot causes in the single-engine accident data, the pattern for twins seems to be significantly different. Weather is still the leading cause of pilot-caused twin accidents, but a variety of other non-weather-related causes are quite significant: botched takeoffs and landings, controlled flight into terrain, improper IFR procedures, fuel exhaustion, and gear-up landings, just to name a few.

About one-fourth of all accidents are classified as "machine caused" for both singles and twins. Only a small fraction of those are engine-failure accidents. But it's interesting to look at the impact of that second engine on engine-failure accident statistics.

For the group of light twins we looked at, mechanical failures of the engine or propeller were responsible for One about 3% of all accidents. Breaking that down, 15.3% of all accidents were due to mechanical failures, and 20.8% of those involved the engine or propeller.

In contrast, roughly 8% of all accidents in high-performance singles were attributed to engine or propeller failure: 17% of accidents were mechanicals, but nearly 50% of those involved the engine or prop.

The statistics showed that a light twin is about equally likely to have a mechanical-caused accident as a high-performance single. But the twin's mechanical problem is most likely to be gear-related while the single's is most likely to be engine/prop-related. A single is about two-and-a-half times more likely to have an accident due to engine/prop failure than a twin (8% versus 3%). And if we assume that a twin is twice as likely to have an engine/prop failure (since it has twice as many to fail), then we can conclude that an engine/prop failure in a single is five times more likely to result in an accident than an engine/prop failure in a twin.

So are you any safer flying a light twin than a high-performance single? In terms of the overall and serious accident rates, the answer seems clearly to be no. But your risk profile changes somewhat: in the twin, you're less likely to be hurt by an engine failure, and more likely to be victimized by something else."