Which is safer- a twin piston or a single turbine?

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BonanzaDriver

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BonanzaDriver
Ah, what an open ended question :)

I am debating between a turbine bonanza A36 or a 58 baron. Safety is paramount, especially after experiencing piston failures in the past. I do not like the extra fuel burn associated with the baron, nor the extra cost of maintaining two engines.

Acquisition costs are about the same, insurance is higher on the baron, and speed goes to the bonanza by about 30 knots.

Any thoughts? I have spoken to old timers who swear by the "extra" engine in the baron.
 
Given those two choices, I'd personally take the turbine Bo, assuming it fit the necessary parameters regarding useful load and range. PM me an email address and I'll send you an article I did on exactly this question -- single turboprop vs piston twin -- although I did not address the specific pair you mention.

Edit: I would post it, but all I have is a scan of the pages and it's 22 MB. I can reduce it a little, but that's a little too much bandwidth to eat here.
 
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You know, I don't know if there is a specialist for this area of expertise. To me, it sounds like you're opening it for discussion, so here's my two cents:

We live (and die) by statistics. I am convinced the statistical liklihood of losing BOTH engines in a twin is LESS than losing THE ONE in the single.

If, as you said, safety is paramount, and we assume that the most unsafe thing that could happen would be loss of powered flight (a big assumption), then the twin is the way to go.

The following is a mostly facetious argument, with some tongue-in-cheek truth:

For me, safety is VERY IMPORTANT, and this may sound wierd intially, but it's not PARAMOUNT. If it was, I wouldn't fly, drive, or ride. I'd mostly stay home in bed.

I think the most unsafe part of flying is NOT loss of powerplant (but then, I've only had that once - with good resolution), but rather stupid pilot tricks. That is, when WE make a bad decision or a mistake. When we run out of options/ideas/luck at the same time. Barring few situations, Gliding to the ground is usually (GA statistics bear witness) not catastrophic.

So I'd feel good about, and go with, the single. It has MUCH better economy, usefulness, and endearment for me. I like the concept of having a meticulously cared for single that I know very well, for less money.

YMMV. God Bless!
 
at least when they engine quits in the A36 the aircraft will still be aerodynamically symmetric.

turbine reliability is very high. fatalaty rates are probably higher after losing one on a twin than losing one on a single (no stats on that, just a hunch)

turbine A36s look and sound cool. although they've fairly limited range dont they? just cant hold enough gas.
 
tonycondon said:
at least when they engine quits in the A36 the aircraft will still be aerodynamically symmetric.

turbine reliability is very high. fatalaty rates are probably higher after losing one on a twin than losing one on a single (no stats on that, just a hunch)

turbine A36s look and sound cool. although they've fairly limited range dont they? just cant hold enough gas.
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The turbine bonanza's range (on 114 gallons) is ~1100nm's, much more range than the A36.
 
Dr. Bill said:
You know, I don't know if there is a specialist for this area of expertise. ..
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...it was me, I'd want to get the opinion of a skilled journalist who specialized in aviation writing, preferably one who specialized in writing about Twins and Turbines.

But what are the odds of ever finding such an odd duck, huh? :D
 
SCCutler said:
...it was me, I'd want to get the opinion of a skilled journalist who specialized in aviation writing, preferably one who specialized in writing about Twins and Turbines.

But what are the odds of ever finding such an odd duck, huh? :D
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...hehe; you called him an 'odd duck'... NOW THAT's funny!!!:goofy:
 
Well, all I can add to this conversation is, if you get that turbine Bo in time, you'd BETTER bring it down to Houston for the Bonanza party at Hobby on August 18. :)
 
BonanzaDriver said:
The turbine bonanza's range (on 114 gallons) is ~1100nm's, much more range than the A36.
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I don't know who in the world told you that, but I'd sure suggest you check that range number. The folks that sell any bird are known for numbers that may not pencil out in the real world.

I went to the P-Baron instead of the A-36 turbine for several reasons, not just the two engines. One of the biggest negatives of the turbine Bo was it's shorter range. I frequently go the exact range you are discussing: to San Diego and the east coast from Dallas--over 1,000NM. I can make it non-stop in the P Baron and did it in my TN A-36 with tip tanks on the amount of fuel you mentioned: 114 useable gallons. The biggest issue with the turbine conversions was they were limited to 700 to 800 NM. Climbed quickly, faster cruise, but limited range. The fuel burns on those are over 30 gph at higher power settings. Maybe high 20s at lower power; I know several owners with them; they all state range is a limitation. I know a few folks that gave them up and went back to the piston or moved on to another turbine with more range (at a much higher price).

The P-baron also is pressurized, has K-ice, is air conditioned and has other system redundancy. My range is about 1100NM on a no wind, standard conditions day. Look at more than one v. two engines. There are a lot of other things to consider. That turbine Bo info you are using is giving you optimum speeds and ranges (maybe). To get that, you will have to be high (where substantial winds come into play). You'll be on a mask or nose straw: you may be O.K. with that, but most passengers aren't. If you stay lower because of weather or winds, the turbine is much less efficient.

Best,

Dave
 
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tonycondon said:
turbine reliability is very high. fatalaty rates are probably higher after losing one on a twin than losing one on a single (no stats on that, just a hunch)
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I'd tend to agree with that, but I'd also bet that pilot proficiency has more to do with it than any aerodynamic effects of the twin.

In other words, if you do the Baron, train early and often.

tonycondon said:
turbine A36s look and sound cool. although they've fairly limited range dont they? just cant hold enough gas.
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I'm about as much of an expert on turbine Bonanzas as Tony, but it seems to me that, in order to get the range, you have to be using your oxygen system for extended periods of time. Not a big fan of that myself, but to each his own.

Fly safe!

David
 
Dave Siciliano said:
I don't know who in the world told you that, but I'd sure suggest you check that range number. The folks that sell any bird are known for numbers that many not pencil out in the real world.

Best,

Dave
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Or, it may pencil out, but you have to be at Long Range Cruise...can you say "Sit in my Bonanza for 8 hours while on oxygen"?

Fly safe!

David
 
If/When you run a piece of crap thru that turbine, your maintenance bill will off set any other advantage.
 
MauleSkinner said:
I'd tend to agree with that, but I'd also bet that pilot proficiency has more to do with it than any aerodynamic effects of the twin.
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probably David, but it seems that even after a good solid 60+ years of flying light twins, pilots in general still havent figured this out.
 
BonanzaDriver said:
Ah, what an open ended question :)

I am debating between a turbine bonanza A36 or a 58 baron. Safety is paramount, especially after experiencing piston failures in the past. I do not like the extra fuel burn associated with the baron, nor the extra cost of maintaining two engines.

Acquisition costs are about the same, insurance is higher on the baron, and speed goes to the bonanza by about 30 knots.

Any thoughts? I have spoken to old timers who swear by the "extra" engine in the baron.
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Chances are the turbine bo will cost more to operate and maintain than the Baron, but maybe not by much. I think if I were considering a turbine single I'd really want pressurization since altitude is very important for efficiency (and TAS) with a turbine and that alone would eliminate the A36.

As to the safety issue, this is really a pair of differently colored fruits. The twin can be safer if you spend time maintaining proficiency, always operate it far enough below MGW that there's enough performance on one engine to eliminate the typical differential thrust plus minimal climb issues (in a B58 that's about 300 below MGW), and limit yourself to runways long enough to provide a true balanced field (4000-5000 ft long in the flatlands). A turbine is probably several times less likely to suffer a mechanical failure induced significant loss of power than a piston engine and since you only have one, the chances are further halved. But the chances of losing both engines from mechanical failure in the twin are probably an order of magnitude lower than the potential for losing the one turbine.

IOW it takes more planning and discipline to operate a light twin in a way that provides the same or better level of risk than you could have with a single turbine, but IMO it can be done in all phases of flight. And the whole thing flips over once you're out of the terminal environment leaving the single turbine less "safe" than the piston twin. Assuming most of your trips are long enough to spend the vast majority of flight time in cruise, that alone might tip the safety based preference towards the twin.

Safety aside, the twins generally offer more useful load, balance options, and room for onboard radar. The turbine Bonanza is ahead WRT cabin sound levels, fuel availability in foreign countries, topping weather, and "coolness". Pick your poison.

I have thought about this fairly often and there's a good chance that my next airplane will be a pressurized turbine single ala Epic or TBM, but the operating cost there is way beyond my Baron.
 
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BonanzaDriver said:
The turbine bonanza's range (on 114 gallons) is ~1100nm's, much more range than the A36.
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I think you'll find that in order to get that kind of range in the turbine A36 you have to fly very high and very slow (and don't carry much).
 
NC19143 said:
If/When you run a piece of crap thru that turbine, your maintenance bill will off set any other advantage.
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Good point. Get unlucky and trash one of the engines in the Baron and you can be back in the air for as little as $30,000. Kill a turbine and it's like ten times as much. And turbines are much easier to kill.
 
I just did a quick, highly unscientific, statistically insignificant search through the NTSB databases using engine out for searches for a twin and single engine aircraft. For the singles 12 out of the 40 accidents examined were fatal. For the twins it was 23 out of 30. This may suggest that twins are indeed less, not more safe than piston or turbine singles.
 
How about a Cessna Caravan ? I think they are very cool. They also boast the best dispatch rate in class.
 
lancefisher said:
And the whole thing flips over once you're out of the terminal environment leaving the single turbine less "safe" than the piston twin. Assuming most of your trips are long enough to spend the vast majority of flight time in cruise, that alone might tip the safety based preference towards the twin.
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I agree with most of your post, Lance, but I have to take issue with this statement. I see no evidence that the chances of a single turbine failing in cruise are any greater than a double piston engine failure. Both are so exceedingly remote as to be unmeasurable for all practical purposes. Those few that happen are almost always tied to another system -- fuel contamination, for example. Mechanicaly, there are only the odd fluke occurrences, nothing we can hang onto firmly enough to declare one "safer" than the other.
 
steingar said:
I just did a quick, highly unscientific, statistically insignificant search through the NTSB databases using engine out for searches for a twin and single engine aircraft. For the singles 12 out of the 40 accidents examined were fatal. For the twins it was 23 out of 30. This may suggest that twins are indeed less, not more safe than piston or turbine singles.
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That's statistics for ya. What you are completely missing is the number of twins that suffered an engine failure and didn't even make it into the database. The only thing supported by your numbers is the notion that if you crash bad enough to get the NTSB's attention in a twin you are 2-3 times as likely to die, and I do believe that's true. It's probably also true that if you crash a fast turbine single you are more likely to die than if you crash a 172 (but maybe not 3 times as likely).
 
I have personally made it to runways on one blower (OEI) TWICE and therefore didn't show up in the NTSB.

However, I have a theory about the real safety. It's called the "random walk" hypothesis. Pilots assess the risk and apportion their choice of operations among ME and SE ops and are very efficient in equalizing risk.

The more under-competent/under-proficient ME operators die, the higher insurance rates go. The more SE operators land out and +/- get injured the higher the SE rates go. Pilots are efficient at equalizing risk in their selections and so the true risks get equalized.

It's sorta like how the stock market evaluates a particular stock.
 
A turbine powered Bo probably has a much lower chance of having an engine failure than a piston powered Bo. But a much lower chance is not zero chance. PT6s do fail in real life. I've seen more than one king air come back on one engine. So if you go with the Bo, you're basically saying you expect to be lucky because, if the fire goes out, you're landing whether there's an airport under you or not.

On the other hand, if you're going to go with a twin, you absolutely must keep your skills sharp or your chances of surviving after losing an engine go down significantly.

So in order to answer this question you have to decide whether you're better at controlling your level of skill or your level of luck. Personally, I'll take skill over luck any day.
 
This whole point brings up another question:

Why would I shell out "similar" cash for a turbine prop versus a VLJ?

I have a few pre-baked answers (2 engines instead of 1; better cabin amenities; short field performance; insurance), but the one thing that I can't shake is - if I was the type that NEEDED an aircraft to get me places, why would I want a turbine that flies at 24k and nails all the nasty weather, versus something that can put me up around 35k and over 95% of the weather?

Cheers,

-Andrew
 
I can think of two:
  • The difference in the price of admission.
  • The cost & time to get a type certification for turbfan aircraft.
 
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jdwatson said:
I can think of two:
  • The difference in the price of admission.
  • The cost & time to get a type certification for turbfan aircraft.
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For # 1... (comparing a "cheapest" on the market):

http://www.aso.com/i.aso3/aircraft_view.jsp?aircraft_id=107010

versus

$1,520,000 for a delivery position in a NEW Eclipse.

Now, I realize this is a bad comparison. A more recent TBM would run you $1.8-$2+M right now, but you'd have it now, versus 1.5 years for an Eclipse.

The payload is different, for sure. But, if I *had* to be places, why would I want to go in a turboprop when I can go by jet? That's the crux of my argument, and I wonder if the cost differential between the two washes out when you add the convinence factor.

Cheers,

-Andrew
 
i dont know andrew, i think a pressurized turboprop could top any weather that is worth messing with. plus the short field performance is much better than a jet and speed usually isnt that much lower.
 
And now my two cents!

Dr. Bill said:
We live (and die) by statistics. I am convinced the statistical liklihood of losing BOTH engines in a twin is LESS than losing THE ONE in the single.
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It's always been my thinking that in a twin, you are TWICE as likely to loose one than you are in a single. And in a twin with an engine out, unless you do some things pretty much exactly right, pretty quickly, you're better off just pulling BOTH throttles to idle. The light twins we are likely to fly have marginal single engine performance at best.

Just an opinion. Given the choice provided, I'd also go with the turbine single.
 
My non-pilot girlfriend figured out the answer to this question on her own. Women are smart that way.

We were walking across the ramp, which had 3 planes on it. The 182RG that we were flying in, a military fighter jet, and a twin turbo-prop. I asked which plane we should take home. She said "the one you know how to fly".

Twin, single, piston, turbine, blah, blah, blah. It's the nut between the yoke and the seat that's the single point of failure most likely to take you down. You have to consider the level of commitment you're willing to make to maintain legitimate proficiency in whatever plane you select, as that's likely to be the overriding factor determining the safety of pilot and passengers.
-harry
 
Andrew:

I've been looking into this and getting pretty frustrated in the process! The TBM is here now, but a new one is a bit more than what you may think. If you want to compare used to new, that's not apples to apples, but is valid in that you can get something now vs in the future.

It all comes back to mission and cost. Most folks don't understand the capability differences and cost differential. Part of the reason is the manufacturer still hasn't released the POH on the Eclipse; TBM has it on their site. TBM is proven; Eclipse isn't.

The Eclipse offers the redundancy and dependability of two jet engines. As dependable as TBMS may be, many people still want two fans and will pay for that. TBM is French; parts, availability, price changes due to foreign currency translation all comes into play. Eclipse is US. Eclipse seems to be efficient at FL350; the TBM would be more efficient lower. TBM is a bit slower, but has better range. Avionics are different. TBM would do shorter runways easier.

Lots of things to look at. The VLJs sound great, but still don't have much on the ramp other than Mustang (which says it's not a VLJ). If one wants proven performance; VLJs are still a pipe dream. A new plane will most likely depreciate in value quite a bit in the first couple years; the used counterpart may be more stable in price.

I'm watching because I could be in a position to play with a partner, but I'm pretty cautious. Wouldn't want to spend that much and not be happy. In my mind, what's out there isn't proven enough for me to risk that much money; I don't need to have it; it's optional. If I did want it, I don't like the pre-purchase terms I'm seeing. Some don't specify any substantial performance terms; just big picture stuff. So, I'm just not a test buyer of million dollar plus stuff.

Best,

Dave
 
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Another aspect of cost to be aware of: I was flying a Bonanza for someone who told me they were buying a Pilatus. I was excited, as I'd be flying it. What fun. He told me it was quoted to him, new, at $1.9 million, and there would be one partner [co-owner] that we'd share it with. This was some time ago, perhaps 1999 or 2000, I don't recall exactly, so I'm not crazy mentioning that particular price, as I'm sure they've gone up since then.

But the problem was, the buyers didn't realize, and they weren't told by the sales rep', and they are both hard-core, astute business people and no dummies, was that the price was for the basic airplane...no paint [except basic white for protection], interior [except a seat for the ferry pilot to sit in], and avionics except the minimum needed to fly for delivery. The upshot was, the finishing of the plane was estimated to be an additional $ .6 million, or $600,000. They walked [sniffle]. In the case of my employer, it was less the total cost [though that was a factor] than the idea they were "sold" on the plane with price comparisons between the Pilatus and competing aircraft, including King Airs and etc. And comparisons of performance, usefel load, and short field abilities [a big one with us].

Perhaps this was simply an eager salesman, or maybe all the makers do this? In any case, the lesson is, be sure just what you are figuring to pay when you decide.... I must say that the Bonanza I was flying was new, or was when we began flying it, and that was not how things went at Beech.
 
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Ken Ibold said:
I agree with most of your post, Lance, but I have to take issue with this statement. I see no evidence that the chances of a single turbine failing in cruise are any greater than a double piston engine failure. Both are so exceedingly remote as to be unmeasurable for all practical purposes. Those few that happen are almost always tied to another system -- fuel contamination, for example. Mechanicaly, there are only the odd fluke occurrences, nothing we can hang onto firmly enough to declare one "safer" than the other.
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I have to admit that I don't have any handy data to back my suspicion, but if you exclude pilot induced failures that affect both engine simultaneously (e.g fuel exhaustion, mis-fueling, etc) then the odds of a dual failure are approximately the square of the chance of a single failure. Given that piston engines are fairly reliable squaring that chance results in a really, really tiny probability of a simultaneous (occurs on the same flight) failure. Let's say the chances of having a single piston engine fail on any trip are as bad as 1 in 10,000. That puts the chances of both failing for independent causes on the same trip at 1 in 100,000,000. I doubt that turbines are that reliable.
 
lancefisher said:
I have to admit that I don't have any handy data to back my suspicion, but if you exclude pilot induced failures that affect both engine simultaneously (e.g fuel exhaustion, mis-fueling, etc) then the odds of a dual failure are approximately the square of the chance of a single failure. Given that piston engines are fairly reliable squaring that chance results in a really, really tiny probability of a simultaneous (occurs on the same flight) failure. Let's say the chances of having a single piston engine fail on any trip are as bad as 1 in 10,000. That puts the chances of both failing for independent causes on the same trip at 1 in 100,000,000. I doubt that turbines are that reliable.
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Well, if you couch it in terms of catastrophic engine failure alone, you're probably right. I was looking at it in terms of sudden lack of propulsion for whatever reason, which is really the bottom line.
 
Well, if you couch it in terms of catastrophic engine failure alone, you're probably right. I was looking at it in terms of sudden lack of propulsion for whatever reason, which is really the bottom line.
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The 2006 Nall report says that there were 31 fatal multiengine crashes in 2005. 4 of these (about 12%) were attributed to fuel management (running out of gas).

For all GA fixed wing, 6% of fatals were attributed to fuel management, and another 5% were attributed to engine-related mechanical causes.

So the real question is, if we assume that engine redundancy completely eliminates the chances of an engine-related accident, and we've thus eliminated 5% of the causes of fatal accidents, how much does the added complexity add back in to our risks?
-harry
 
mantakos said:
The 2006 Nall report says that there were 31 fatal multiengine crashes in 2005. 4 of these (about 12%) were attributed to fuel management (running out of gas).

For all GA fixed wing, 6% of fatals were attributed to fuel management, and another 5% were attributed to engine-related mechanical causes.

So the real question is, if we assume that engine redundancy completely eliminates the chances of an engine-related accident, and we've thus eliminated 5% of the causes of fatal accidents, how much does the added complexity add back in to our risks?
-harry
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First of all, when using Nall reports or any stats, you really have to scan at least 10 years in order to draw any conclusions. The data fluctuates wildly year to year because the sample sizes are small. I mean, 4 accidents? One guy opts not to fly and your group of victims drops by 25%.

Be that as it may, that added complexity is the whole issue. Go back to those 31 and see how many were Vmc rollovers and how many were due to lack of SE proficiency. THAT is your added risk.
 
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