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06 Jul 2022, 20:40 [ UTC - 5; DST ]


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 Post subject: Re: Cirrus G6 2022
PostPosted: 23 Jan 2022, 12:57 
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Username Protected wrote:
So are you arguing that half the engines don't statistically equal half the failures?

If so, I'd love to hear your logic as to why?


Actually, yes, I believe that is correct.

This topic came up recently amongst some friends of mine. One of whom is a math whiz that pointed us to a Binomial Calculator to solve for this.

https://stattrek.com/online-calculator/binomial.aspx

I'm open to being wrong here and invite anyone to show me how I am. I was originally surprised to hear that the idea of 2 engines doubling your failure probability was technically incorrect. This is NOT my area of expertise.

The FAA tells us that a piston engine fails in 1 of every 3200 flight hours.

In a Single Engine Piston, that gives us roughly 63% cumulative probability of experiencing one or more failures in 1 of 3200 flight hours.

In a Twin Engine Piston, that gives us roughly 86% cumulative probability of experiencing one or more failures in 1 of 3200 flight hours.

I recognize that there are dozens of other variables which would likely change these probabilities (i.e. forced induction vs. NA, compression ratios, engine size, cooling process, etc.)...we simply used the easiest-to-obtain data available to us from the FAA.


Very well then. Let's use your numbers.

In a piston single, one has a 37% chance of avoiding an engine failure in one of 3200 flight hours.
In a piston twin, one has a 14% chance of avoiding an engine failure in one of 3200 flight hours.

You're 2.6 times as likely to avoid an engine failure in a single vs a twin. :thumbup:

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 Post subject: Re: Cirrus G6 2022
PostPosted: 23 Jan 2022, 15:25 
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Username Protected wrote:
In a piston single, one has a 37% chance of avoiding an engine failure in one of 3200 flight hours.
In a piston twin, one has a 14% chance of avoiding an engine failure in one of 3200 flight hours.

You're 2.6 times as likely to avoid an engine failure in a single vs a twin. :thumbup:


Haha. I’m ASSUMING you forgot to green text that. :ohno:


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 Post subject: Re: Cirrus G6 2022
PostPosted: 23 Jan 2022, 15:26 
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Username Protected wrote:
You're 2.6 times as likely to avoid an engine failure in a single vs a twin. :thumbup:

This analysis makes a lot of assumptions, so it is superficial at best.

Also, avoiding engine failure is not the same as avoiding an accident caused by engine failure. The single might have fewer engine failures, but a higher percentage of them might end up as accidents because the twin can fly to an airport and land with an engine out.

Still, go read through the CAPS history. A LOT of engine issues preceded chute deployments. Indeed, the last 3 chute deployments have all been engine related.

Mike C.

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 Post subject: Re: Cirrus G6 2022
PostPosted: 23 Jan 2022, 15:33 
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There is a lot of selection bias on CAPs use.

An engine failure is probably the most likely thing to cause CAPS activation. Structural failures can happen , but are pretty rare. Not clear if CAPS is what you want in an in-flight fire.

CFIT kills a lot of people but doesn't activate CAPS.

VFR into IMC - most pilots will turn on the autopilot.


Engine failure rates are complicated for all the reasons discussed.


Username Protected wrote:
You're 2.6 times as likely to avoid an engine failure in a single vs a twin. :thumbup:

This analysis makes a lot of assumptions, so it is superficial at best.

Also, avoiding engine failure is not the same as avoiding an accident caused by engine failure. The single might have fewer engine failures, but a higher percentage of them might end up as accidents because the twin can fly to an airport and land with an engine out.

Still, go read through the CAPS history. A LOT of engine issues preceded chute deployments. Indeed, the last 3 chute deployments have all been engine related.

Mike C.


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 Post subject: Re: Cirrus G6 2022
PostPosted: 23 Jan 2022, 15:50 
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Joined: 12/19/11
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Company: Bottom Line Experts
Location: KTOL - Toledo, OH
Aircraft: 2013 SR22T G5
This single engine vs twin engine failure is another bottomless black hole with no good data to rely on for insight and will likely always be that way.

I had an engine failure in my Seneca II a minute after takeoff. I caged the engine, told ATC I was coming back, landed and taxied back with no issue. My heart was definitely thumping but I didn’t declare an emergency and it was mostly not a big issue. You won’t read about that failure in any report or database just like you won’t with many engine failures in twins.

Mike is right that quite a few CAPS activations have occurred due to engine failures or engine troubles. I don’t know the exact number but it’s a healthy percentage. I’ll see if I can dig it up on COPA.

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Don Coburn
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2013 SR22T G5


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 Post subject: Re: Cirrus G6 2022
PostPosted: 23 Jan 2022, 16:55 
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Username Protected wrote:
In a piston single, one has a 37% chance of avoiding an engine failure in one of 3200 flight hours.
In a piston twin, one has a 14% chance of avoiding an engine failure in one of 3200 flight hours.

You're 2.6 times as likely to avoid an engine failure in a single vs a twin. :thumbup:


Haha. I’m ASSUMING you forgot to green text that. :ohno:


Why?
It's mathematically accurate. If you disagree please show me why.

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 Post subject: Re: Cirrus G6 2022
PostPosted: 23 Jan 2022, 16:58 
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Username Protected wrote:
You're 2.6 times as likely to avoid an engine failure in a single vs a twin. :thumbup:

This analysis makes a lot of assumptions, so it is superficial at best.

Also, avoiding engine failure is not the same as avoiding an accident caused by engine failure. The single might have fewer engine failures, but a higher percentage of them might end up as accidents because the twin can fly to an airport and land with an engine out.

Still, go read through the CAPS history. A LOT of engine issues preceded chute deployments. Indeed, the last 3 chute deployments have all been engine related.

Mike C.


I didn't do any analysis. I just used the FAA analysis that Robert quoted.

And terms like "A LOT" and " The last 3" are the very definition of anecdotal and superficial evidence...

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 Post subject: Re: Cirrus G6 2022
PostPosted: 23 Jan 2022, 17:10 
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Username Protected wrote:
Why?
It's mathematically accurate. If you disagree please show me why.


You had previously shown a curiosity about the logic behind why half the engines doesn’t equate to half as many failures statistically. I simply shared the math that was recently presented to me on this exact topic. All things being equal, I’m confident that the math I shared checks out. But how often is everything equal in this world of aviation?

Beyond that, I’m not interested in a long form discussion about the probabilities surrounding engine failures in singles vs. twins. It’s practically an endless argument.

The fact that you were able to take 23% and manipulate it to 250% only proves my point that this can quickly become a rabbit hole discussion.


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 Post subject: Re: Cirrus G6 2022
PostPosted: 23 Jan 2022, 17:20 
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Username Protected wrote:
Why?
It's mathematically accurate. If you disagree please show me why.


You had previously shown a curiosity about the logic behind why half the engines doesn’t equate to half as many failures statistically. I simply shared the math that was recently presented to me on this exact topic. All things being equal, I’m confident that the math I shared checks out. But how often is everything equal in this world of aviation?

Beyond that, I’m not interested in a long form discussion about the probabilities surrounding engine failures in singles vs. twins. It’s practically an endless argument.

The fact that you were able to take 23% and manipulate it to 250% only proves my point that this can quickly become a rabbit hole discussion.


I didn’t manipulate anything. I used the numbers that you provided from the FAA research. The fact remains that if it’s 63% likelihood of an engine failure in a single then you are 37% likelihood to avoid an engine failure over those 3200 hours.
And if you are 86% likelihood to have an engine failure in a twin then you are 14% likelihood to avoid an engine failure in a twin in that same time span. So 14% is 2.6 times as likely to have the engine failure as 37%.
Is that not correct?

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 Post subject: Re: Cirrus G6 2022
PostPosted: 23 Jan 2022, 19:48 
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Joined: 01/01/18
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Location: West Long Branch, NJ (KBLM)
Aircraft: 1960 Twin Bonanza
Maybe we should only fly with one magneto as our risk of failure is double if we have two. Or start removing our 2nd vacuum pumps or alternators for fear of an increased likelihood of failure. When you remove your 2nd one, I’ll remove mine.

Any level of redundancy increases the risk of failure.

I don’t see a lot of single engine traveling jets out there, wonder why?

In the last 18 months I’ve had two engine shutdowns, both times my second engine brought me home. I am OK if the odds of a failure are double, so long as the odds of making it home to my dinner table are double for me as well.

With that said I I have no qualms flying cirrus aircraft, the chute certainly makes me happier when I’m not within glide of an airport or a road.

Back to topic now???

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 Post subject: Re: Cirrus G6 2022
PostPosted: 23 Jan 2022, 20:12 
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Username Protected wrote:
Maybe we should only fly with one magneto as our risk of failure is double if we have two. Or start removing our 2nd vacuum pumps or alternators for fear of an increased likelihood of failure. When you remove your 2nd one, I’ll remove mine.

Any level of redundancy increases the risk of failure.

I don’t see a lot of single engine traveling jets out there, wonder why?

In the last 18 months I’ve had two engine shutdowns, both times my second engine brought me home. I am OK if the odds of a failure are double, so long as the odds of making it home to my dinner table are double for me as well.

With that said I I have no qualms flying cirrus aircraft, the chute certainly makes me happier when I’m not within glide of an airport or a road.

Back to topic now???


all true. This quick little discussion detour was specifically about whether having two engines will double your chances of an engine failure, not whether that engine failure will end up killing you or whether it’s a good or bad idea to have a second engine. Obviously I feel that a twin is better than a single all things being equal. I have about 300 hours in twin piston aircraft and now about 500 hours in Twin turbine Aircraft . I also feel very safe flying the cirrus in many weather conditions. As long as the aircraft is well-maintained and often flown, I have no qualms about flying either one at any given time. It's all about the mission.


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 Post subject: Re: Cirrus G6 2022
PostPosted: 23 Jan 2022, 20:21 
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Joined: 01/01/18
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Location: West Long Branch, NJ (KBLM)
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Ready to trade an hour in the queen air for 15 minutes in the jet?

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CFII MEI


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 Post subject: Re: Cirrus G6 2022
PostPosted: 23 Jan 2022, 22:06 
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Username Protected wrote:
With that said I I have no qualms flying cirrus aircraft, the chute certainly makes me happier when I’m not within glide of an airport or a road.

Back to topic now???


In todays insurance environment, one of the least talked about aspect of pulling the chute to me is that the second you pull that you have to check the yes box next to “have you had a claim or a hull loss in your history”

Curious to hear from a pilot who pulled the chute as to how the process of replacing and reinsuring then next airframe went, I’m willing to learn or be surprised here


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 Post subject: Re: Cirrus G6 2022
PostPosted: 23 Jan 2022, 22:16 
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Can’t fully answer except to say every insurance company I looked at said no deductible if you pull. Assume that’s to encourage an airframe loss vs injury or death, but can’t answer for them. My insurance $2m smooth, was reasonable. Also always came with a $3m smooth option.


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 Post subject: Re: Cirrus G6 2022
PostPosted: 23 Jan 2022, 22:56 
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Username Protected wrote:
Ready to trade an hour in the queen air for 15 minutes in the jet?


No trades needed. Lmk when you're around.


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