Twin safety record

Let'sgoflying!

Let'sgoflying!

Touchdown! Greaser!
Joined
Feb 23, 2005
Messages
20,322
Location
west Texas
Display Name
Display name:
Dave Taylor
I need a refresher on this, it has been a while since I saw a thread or Nall review of light piston twins vs singles.
Thanks for any links/comments.
It might affect my next airplane decision.

As I recall, they have less accidents (was that less, due to engine outs - or less, total?)
But they have proportionally more fatals (OEI instances and carry more energy into any unplanned with terrain).
 
I am wondering if anyone has done a study on the twin v. single accident rates that compared single engine aircraft and their twin sibling like Bonanza/Baron, Comanche/Twin Comanche, Lance/Seneca, etc. The problem with the general accident statistics is that they compare aircraft with much greater average stall speeds to the average single engine which included Cubs, etc. The other problem with the twin engine safety analysis is that there is no data on the twins that suffer an engine failure and land at an airport. These are often not reported so they don't get adding to the statistical pool.
 
Twins have two engines, so its twice as likely to have an engine failure. This works to negate the safety of the additional engine. The studies Ive seen were done by Flying magazine and actually showed the twins being MORE dangerous than singles. Lots of twin pilots dispute this though. No one really knows for sure. There is no question that they are more expensive.
 
If you need an all weather traveling machine, are going to fly 150 hrs per year, and are willing to commit to proper and recurring training then a twin is the way to go. If you don't meet those conditions then get a single.

When I lost an engine the other one brought me safely to an airport. YMMV, but I prefer two.
 
  • Like
Reactions: Ted
coloradobluesky said:
Twins have two engines, so its twice as likely to have an engine failure. This works to negate the safety of the additional engine. The studies Ive seen were done by Flying magazine and actually showed the twins being MORE dangerous than singles. Lots of twin pilots dispute this though. No one really knows for sure. There is no question that they are more expensive.
Click to expand...

How about the pilot who never goes through recurring training and when he loses and engine can't resolve the situation to a safe ending? James brought his 310 in on one and there was a happy ending. Would a lesser trained pilot be capable of that?
 
With proper training,twins are great if you can afford the costs associated with them. If you fly like you could loose an engine at any time,you won't have a problem.
 
On a light twin if you have an engine failure, you lose 80% of your performance. The problem flying on one engine is pilots don't keep current on SE emergency procedures or are extremely rusty on the procedures. Most light twins will climb some and/or hold altitude as long as one does things correctly. I used to instruct in C-310s of which the FBO had 5 of. The one we used for training most of the time usually wouldn't hold altitude, might have been a Q model but I forget. I did my MEI in this plane w/ a Fed and he didn't believe it wouldn't hold altitude. He tried it and we were descending about 1-200 FPM. He said this plane is sick and a pig! Don't remember what he told the owner of the FBO. As long as a pilot knows what to expect if one quits and applies the proper procedures, they can make it to an airport.
 
coloradobluesky said:
Twins have two engines, so its twice as likely to have an engine failure. This works to negate the safety of the additional engine. The studies Ive seen were done by Flying magazine and actually showed the twins being MORE dangerous than singles. Lots of twin pilots dispute this though. No one really knows for sure. There is no question that they are more expensive.
Click to expand...

Mathematically speaking that is not entirely accurate.
 
I can only give one data point. I've had two engine failures, both in twins. The other engine always brought me back home.
 
Kristin said:
I am wondering if anyone has done a study on the twin v. single accident rates that compared single engine aircraft and their twin sibling like Bonanza/Baron, Comanche/Twin Comanche, Lance/Seneca, etc. The problem with the general accident statistics is that they compare aircraft with much greater average stall speeds to the average single engine which included Cubs, etc. The other problem with the twin engine safety analysis is that there is no data on the twins that suffer an engine failure and land at an airport. These are often not reported so they don't get adding to the statistical pool.
Click to expand...

+1.

Much talk around the hangar over the years about "...the second engine taking you to the scene of the accident...", but as you noted above most light twin single engine out incidents that end without drama are not reported.

coloradobluesky said:
Twins have two engines, so its twice as likely to have an engine failure. This works to negate the safety of the additional engine. The studies Ive seen were done by Flying magazine and actually showed the twins being MORE dangerous than singles. Lots of twin pilots dispute this though. No one really knows for sure. There is no question that they are more expensive.
Click to expand...

Are you able to provide a link or more complete reference please?
The use of the phrase "more dangerous" without any qualification is a wee bit pejorative. ;) Are gliders, with no engine and no chance of an engine failure, therefore "safer" than a single? Are high performance singles "more dangerous" than training airplanes? Is a car with 8 cylinders less reliable than a car with only 4?

For most of us I suspect mission and budget are two of the main determining criteria for our choice of airplane (otherwise we would all be buying the $$$ airplane with the red handle on the ceiling, non?) :cool:

My primary reason for owning a twin is that I live just east of the Continental Divide and my wife & I grew up on the west coast. Even on a perfect VFR morning in the summer most of the interior valleys are fog shrouded, and all the airports are in the valley bottoms. An engine out in a single leaves few options...and none of them are good. Hence my singles too often sat in the hangar on an otherwise perfect flying day while my family and I headed to the coast jammed into the seats of a discount airline. The second reason I own a twin is single engine IFR in actual IMC (over any terrain) is something I simply will not do - over the years I have lost a couple of friends who used to do that regularly in a Malibu and a Mooney - both came to an end due to mechanical failure of the engine in IMC.

To your point, twins are more complex and generally have more systems than most singles. That demands a certain amount of respect imo. Could be a lot of accidents in twins are the result of pilots getting complacent and assuming the redundancy in the aircraft will save them from harm? When I note how many singles end up on the ground after fuel exhaustion, I wonder how many pilots of twins like mine fail to consistently check the operation of both vacuum pumps, both alternators and both hydraulic pumps before they depart.

Here's a recent example that is going to go down as a light twin accident in the statistics. But the reality is if these pilots had made exactly the same poor decision in an IFR single the outcome would certainly have been the same. They took off IFR into IMC with one vacuum pump known to be inop, lost the other in flight, lost control of the airplane after the gyros quit and experienced the inevitable "done come from together".

http://generalaviationnews.com/2016/03/08/inflight-break-up-fatal-for-two/#more-100117
 
Last edited:
coloradobluesky said:
Twins have two engines, so its twice as likely to have an engine failure. This works to negate the safety of the additional engine. The studies Ive seen were done by Flying magazine and actually showed the twins being MORE dangerous than singles. Lots of twin pilots dispute this though. No one really knows for sure. There is no question that they are more expensive.
Click to expand...
According to the AvWeb article linked earlier...
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.
Click to expand...
 
The aviation writer that I believe has done the most analysis of this over the decades is Richard Collins. A lot of what he wrote factored into my assessments as I was considering whether I should move up to a twin. Here's a few excerpts from an article from Flying by Collins dated 2008:

http://www.flyingmag.com/what-happened-piston-twin

"...Aviation was much into myths at the time. Two of them were that twins were far safer than singles, plus, that any red-blooded American pilot would "step up to a twin" as soon as he could afford to do that. It was a natural progression from a beginning airplane to a high-performance single to a twin (and later to a turboprop and then a jet).

The available information on accidents was sparse at that time and most opinions were formed based on what we saw and experienced around the local airport. Twins certainly seemed like they would be safer. The first tarnish that I saw on the reputation of the twin came in July 1958. I lost three friends when a Beech Travel Air flat spun to the ground on an FAA multiengine check ride. That accident was followed by many more like it, mainly in Travel Airs, Barons and Piper Twin Comanches.

The cause of all these similar accidents related more to an insane FAA requirement (do minimum engine-out control speed demonstrations as low as possible, but not below 500 feet above the ground) than to the airplanes. It was as if the FAA just wanted to certify survivors to fly twins. It took a long time and a lot of effort to bring sense and logic to the FAA on this subject..."

"...To this day, many folks who were around then, and for the many things I've written since on the single v. twin subject, are convinced that I just hate piston twins. Nothing could be farther from the truth. All I ever wanted to do was convince pilots that if twins are properly flown, they will almost always give you a shot at landing on a runway after one engine fails. If they are not flown with a high degree of proficiency when the thrust is asymmetric, they'll kill you quick..."

"...The simple fact today is that, using available numbers, there's little difference in accident rates of most high performance singles and piston twins. One can't be said to be safer than the other and there is no current justification for insurance discrimination against twins. That is somewhat different than my original study, but back then there were no numbers of hours flown by type and all you could look at was the percentage of the fleet that crashed. That gave an advantage to the singles because twins tend to fly more hours, and accident rates are generally considered to be so many per hundred thousand hours.

Today there are exceptions in the safety record picture, with the Piper PA-46 Malibu/Mirage, Cessna pressurized P210 and Aerostar twins on the high side. On the other hand, airplanes like the Cessna 172 and 182 have a lower involvement in serious accidents than other piston singles.

So many things have changed since the piston twin first came on the scene that it is hard to imagine how these airplanes can ever enjoy a second coming. The alignment of the stars will never again be like it was when the piston twin was the airplane lusted over by most pilots..."

​
 
GRG55 said:
The aviation writer that I believe has done the most analysis of this over the decades is Richard Collins. A lot of what he wrote factored into my assessments as I was considering whether I should move up to a twin. Here's a few excerpts from an article from Flying by Collins dated 2008:

http://www.flyingmag.com/what-happened-piston-twin

​
...
Click to expand...

Here's a link to Richard Collins' original groundbreaking light twin safety statistics assessment back in 1965:

http://airfactsjournal.com/2011/12/50-years-ago-in-air-facts-double-trouble/

Just in case anyone is not aware, Collins is still writing some interesting articles (now online), with a safety emphasis:

http://airfactsjournal.com/dicks-blog/
 
Collins has softened a bit. In the 80's, he was trumpeting the fact that twins have a higher fatal accident rate than singles, by about 4x. His statistics at that time didn't seem to distinguish between high performance singles and Cubs, IIRC. His latest is more nuanced.

I live on the west coast. I have a Twin Comanche because I fly IFR and at night. Even in the day time, the number of satisfactory places to put down a single after losing an engine is very limited -- specially compared to the Midwest, for example.
 
Kristin said:
Collins has softened a bit. In the 80's, he was trumpeting the fact that twins have a higher fatal accident rate than singles, by about 4x. His statistics at that time didn't seem to distinguish between high performance singles and Cubs, IIRC. His latest is more nuanced.

...
Click to expand...

I also believe training and recurrency standards have improved, possibly fewer low time pilots are flying twins now (insurance discourages it for one thing), and there are more high performance singles being bought and flown instead of twins (Malibu, Cirrus, Cessna 400/TTX, turbo-Mooneys). From one of the Collins articles (written in 2008) linked above:


"...The simple fact today is that, using available numbers, there's little difference in accident rates of most high performance singles and piston twins. One can't be said to be safer than the other and there is no current justification for insurance discrimination against twins. That is somewhat different than my original study, but back then there were no numbers of hours flown by type and all you could look at was the percentage of the fleet that crashed. That gave an advantage to the singles because twins tend to fly more hours, and accident rates are generally considered to be so many per hundred thousand hours..."​
 
I have to think that today's ready availability of decent simulators to GA pilots has to be a big step in making twin flying safer. Sims let the pilot practice not crashing a lot better than can be done in a real airplane.

There were no GA sims to speak of until fairly recently.
 
JimNtexas said:
I have to think that today's ready availability of decent simulators to GA pilots has to be a big step in making twin flying safer. Sims let the pilot practice not crashing a lot better than can be done in a real airplane.

There were no GA sims to speak of until fairly recently.
Click to expand...

The real issue is utilization. Insurance requires an "approved" school, which is usually in an old, junk sim. And that's if it's required, which it isn't for many twins.

My opinion for light twins, the best school is a good instructor in the plane plus some sim time.
 
Ted DuPuis said:
The real issue is utilization. Insurance requires an "approved" school, which is usually in an old, junk sim. And that's if it's required, which it isn't for many twins.

My opinion for light twins, the best school is a good instructor in the plane plus some sim time.
Click to expand...


Lolz... I distinctly remember some ******* instructor giving me my initial checkout in the 310. We're in the pattern with a 121 flight and he picks the downwind leg to decide to have 'engine troubles'. Did I mention that I already had gear and flaps out when this 'problem' occurred? I was so far behind the plane that it is a minor miracle that he didn't have to intervene.

Best lesson I ever had. :)
 
  • Like
Reactions: Ted
JimNtexas said:
I have to think that today's ready availability of decent simulators to GA pilots has to be a big step in making twin flying safer. Sims let the pilot practice not crashing a lot better than can be done in a real airplane.

There were no GA sims to speak of until fairly recently.
Click to expand...
Do the lower level sims truly emulate a failure shortly after takeoff??? (Not a part 25 airplane so no V1 cut, but similar?).
 
Ted DuPuis said:
My opinion for light twins, the best school is a good instructor in the plane plus some sim time.
Click to expand...

You mean like this guy?

Had to give it some power on the bad engine to make it. As soon as he retracts flaps he goes downhill quick. Granted, his technique was average, which is to say it was a realistic condition, but still that's pretty terrible engine performance.

Anybody has the stats on engine failures for single engine turboprops? How they compare to the piston twin? I think that'd be my preference if money didn't reach the twin turbine. Granted, you lose the turbine past balanced field length and below 500AGL and you're in deep doo doo with 4k+ lbs airplane crashing straight ahead; I just haven't heard much about single T-props crapping out much. There was the Caravan in Hawaii that ditched. One fatality, the rest swam out to safety.
 
hindsight2020 said:
You mean like this guy?

Had to give it some power on the bad engine to make it. As soon as he retracts flaps he goes downhill quick. Granted, his technique was average, which is to say it was a realistic condition, but still that's pretty terrible engine performance.

Anybody has the stats on engine failures for single engine turboprops? How they compare to the piston twin? I think that'd be my preference if money didn't reach the twin turbine. Granted, you lose the turbine past balanced field length and below 500AGL and you're in deep doo doo with 4k+ lbs airplane crashing straight ahead; I just haven't heard much about single T-props crapping out much. There was the Caravan in Hawaii that ditched. One fatality, the rest swam out to safety.
Click to expand...

If I understood this video correctly, this instructor should not be teaching. It appears that he has one prop windmilling (not sim. feather), and orders a go-around from a landing configuration. They are hugging the runway with the instructor calling out airspeed warnings and then says he will simulate feather, removing the drag of the windmilling prop. He was lucky that he didn't end up in a Vmc rollover.
 
Kristin said:
If I understood this video correctly, this instructor should not be teaching. It appears that he has one prop windmilling (not sim. feather), and orders a go-around from a landing configuration. They are hugging the runway with the instructor calling out airspeed warnings and then says he will simulate feather, removing the drag of the windmilling prop. He was lucky that he didn't end up in a Vmc rollover.
Click to expand...
Huh?? Looked fine to me. In fact, looked like good training.
 
hindsight2020 said:
You mean like this guy?

Had to give it some power on the bad engine to make it. As soon as he retracts flaps he goes downhill quick. Granted, his technique was average, which is to say it was a realistic condition, but still that's pretty terrible engine performance.

Anybody has the stats on engine failures for single engine turboprops? How they compare to the piston twin? I think that'd be my preference if money didn't reach the twin turbine. Granted, you lose the turbine past balanced field length and below 500AGL and you're in deep doo doo with 4k+ lbs airplane crashing straight ahead; I just haven't heard much about single T-props crapping out much. There was the Caravan in Hawaii that ditched. One fatality, the rest swam out to safety.
Click to expand...
He didn't add power per se, but rather simulated zero thrust by adding power to simulate a feathered prop.
 
Kritchlow said:
He didn't add power per se, but rather simulated zero thrust by adding power to simulate a feathered prop.
Click to expand...

Right! Which means that up until that point, the prop was windmilling. Trying to go-around with gear down and a windmilling prop is great training up until the point that you lose it and crash. Too much risk of a crash to justify making the training that realistic, assuming that it was realistic, which I question.

I don't know what they are flying, but if you are making a single-engine approach, why is the prop not set to simulated feather, as in a real situation you would have feathered the engine. A SE go-around is generally for aircraft that really have the capability of doing that, which is not most light twins, at least not at gross on a warm day. This one apparently did not have much extra thrust as it was not able to overcome the windmilling prop, and the instructor had to set zero thrust, which seems to me should have been done a long time before.
 
Kristin said:
Right! Which means that up until that point, the prop was windmilling. Trying to go-around with gear down and a windmilling prop is great training up until the point that you lose it and crash. Too much risk of a crash to justify making the training that realistic, assuming that it was realistic, which I question.

I don't know what they are flying, but if you are making a single-engine approach, why is the prop not set to simulated feather, as in a real situation you would have feathered the engine. A SE go-around is generally for aircraft that really have the capability of doing that, which is not most light twins, at least not at gross on a warm day. This one apparently did not have much extra thrust as it was not able to overcome the windmilling prop, and the instructor had to set zero thrust, which seems to me should have been done a long time before.
Click to expand...
I wasn't there to see the particulars (obviously) but many, many moons ago I was taking a checkride for an employer that wanted to make it as hard as possible.... Windmilling prop on final, then, in the flare, the prop suddenly feathers (he sets zero thrust) and the airplane yaws. Right or wrong practice??? Not sure. Examiner is FAA.
 
"Single-engine go-arounds must be avoided. As a practical matter in single-engine approaches, once the airplane is on final approach with landing gear and flaps extended, it is committed to land. If not on the intended runway, then on another runway, a taxiway, or grassy infield." --Airplane Flying Handbook
 
dmspilot said:
"Single-engine go-arounds must be avoided. As a practical matter in single-engine approaches, once the airplane is on final approach with landing gear and flaps extended, it is committed to land. If not on the intended runway, then on another runway, a taxiway, or grassy infield." --Airplane Flying Handbook
Click to expand...
Indeed that's true for smaller twins, but in the above scenario, you still can't land on top of another airplane....
 
In real life, this is true. In the sim, the fuel truck always pulls out onto the runway. In a piston twin below 500 AGL, I'd put it on the taxiway or grass. I keep flaps at 10 degrees and gear up until landing is assured on one engine, then I commit to landing. Training is the key, whether you have one engine or two.

dmspilot said:
"Single-engine go-arounds must be avoided. As a practical matter in single-engine approaches, once the airplane is on final approach with landing gear and flaps extended, it is committed to land. If not on the intended runway, then on another runway, a taxiway, or grassy infield." --Airplane Flying Handbook
Click to expand...
 
Kritchlow said:
I wasn't there to see the particulars (obviously) but many, many moons ago I was taking a checkride for an employer that wanted to make it as hard as possible.... Windmilling prop on final, then, in the flare, the prop suddenly feathers (he sets zero thrust) and the airplane yaws. Right or wrong practice??? Not sure. Examiner is FAA.
Click to expand...

FAA examiners have ended up causing a number of crashes doing questionable things on checkrides.
 
dmspilot said:
"Single-engine go-arounds must be avoided. As a practical matter in single-engine approaches, once the airplane is on final approach with landing gear and flaps extended, it is committed to land. If not on the intended runway, then on another runway, a taxiway, or grassy infield." --Airplane Flying Handbook
Click to expand...

I completely agree with that. In that situation, if there was no chance of using the runway regardless of the aircraft, it would sidestep to the taxiway. Maybe very light and temps well below standard I might consider the SE go-around if I could start to execute it above 500' AGL Seems like an unlikely combination of events.
 
Light twin SE go-around? If it's a real situation remember it's now an emergency. Land somewhere, whether it's the runway, taxiway, grass etc. Planes can be replaced.
 
James_Dean said:
Lolz... I distinctly remember some ******* instructor giving me my initial checkout in the 310. We're in the pattern with a 121 flight and he picks the downwind leg to decide to have 'engine troubles'. Did I mention that I already had gear and flaps out when this 'problem' occurred? I was so far behind the plane that it is a minor miracle that he didn't have to intervene.

Best lesson I ever had. :)
Click to expand...

As someone who resembles that remark (specifically the ******* instructor bit), that puts a smile on my face. :)

This weekend, I took someone for a flight in the 310 who'd never been in one before, and also had never done any OEI work before. We failed (and feathered) the right engine. The transition from windmilling to feather and the almost instantaneous performance improvement that goes along with it amazed him. Then we did the in-air restart. I did a similar demo for Lance and Spike at Gaston's (although we did the left engine that time, I did the right engine this time mainly to make sure that it feathered in-flight). In both demonstrations, the passengers were surprised at how easy it was to fly on one, and how good the performance was.

Kritchlow said:
Do the lower level sims truly emulate a failure shortly after takeoff??? (Not a part 25 airplane so no V1 cut, but similar?).
Click to expand...

I've only flown the SimCom full motion sim. Tried flying their fixed sim, but it kept on crashing (the computer, not the airplane).

My opinion is that it simulates the procedure well enough, which is really the point. The performance I think was a bit overly optimistic vs. the real world, but was probably based off of performance charts that the OEMs provided (which were also overly optimistic). Similar for icing - it doesn't lose as much airspeed as it should, and when you blow the boots it becomes instantly better. Real world? Blow the boots and go "****ing ****, I wanted more ice to come off than that."

You do need to be careful in training. I remember one dark, rainy night about 7 years ago in my Aztec when I was doing initial training. We were doing a VOR approach at an airport about 50 miles from home, no tower, nobody around (of course). My instructor tended to fail engines on me using the fuel selector in the Aztec, which worked great from the perspective of making sure I didn't know automatically which engine failed (the fuel selectors are in between the pilot and co-pilot in the Aztec). He failed the engine on me, and then set it to "simulated feather". Turns out, he didn't get the fuel selector in the detent, it was windmilling the whole time. Neither of us noticed. As I was coming down, full power on the right engine and still losing altitude, getting frighteningly close to the trees, he realized what he did wrong, got the fuel selector back in, and we got out. That still scares me thinking about how close we were to an NTSB report.

Oh, and single engine go-around? No. I'm with @N747JB on that one, I'll put it off to the side or in the grass first. Far too many people have killed themselves trying to do single engine go-arounds in a piston twin. Even the 310, which has much better OEI performance than most (thanks largely to the Colemill conversion), I would not do it. You still need flaps and gear up to have any sort of climb performance.
 
Kritchlow said:
I wasn't there to see the particulars (obviously) but many, many moons ago I was taking a checkride for an employer that wanted to make it as hard as possible.... Windmilling prop on final, then, in the flare, the prop suddenly feathers (he sets zero thrust) and the airplane yaws. Right or wrong practice??? Not sure. Examiner is FAA.
Click to expand...
Many moons ago people were less risk averse when it came to training. Then they found out that that type of training was causing accidents. If the trainer/trainee was able to handle these situations it was a good lesson. Otherwise not so much. The fact that it was that FAA doesn't mean anything.
 
Everskyward said:
Many moons ago people were less risk averse when it came to training. Then they found out that that type of training was causing accidents. If the trainer/trainee was able to handle these situations it was a good lesson. Otherwise not so much. The fact that it was that FAA doesn't mean anything.
Click to expand...

A lot of it comes down to how good the student and teacher really are. One of my friends was a long time test pilot for an OEM. He's told me a couple of scenarios that he said he only does with pilots who are really pretty advanced to start out with, and do a good job of creating a realistic very challenging situation. There are outs for training, of course, but there's some risk involved, and it's not something he does with everyone for that reason. But in that case you have a very good instructor in the plane with a pilot who is also very good. Big difference between that and the 250 hour super pilot who just got his ratings at ATP from instructors who were also 250 hour super pilots, and none of them really know what they're doing.
 
You must log in or register to reply here.
Back
Top