Risk Tolerance

EdFred said:
If P is .5 how can you end up with a greater than 100% chance? [(2*.5) + .25] You can't. Well, evidently YOU can.

Going past 50%, you're saying there's a more than 200% chance that something will occur if the probabilities are 75% for each one.
.75 + .75 + .5625

Recheck your math.
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Ed, if you'd learn a little math, you might have noticed that I made a sign error. The correct equation is 2P - P^2 and I've corrected my post above. It does NOT change my conclusion that a twin is twice as likely to have an engine failure as a single, a statement that you called "bad math." In the case of engine failures, P is a small number and the P^2 term becomes insignificant for the quality of our data.

In the coin example you seem to like, 2P - P^2 = 2(0.5) - (0.5^2) = 0.75. In the case of larger values of P, such as P=0.5, the P^2 term is not insignificant.

BOTTOM LINE - a twin is indeed twice as likely to experience an engine failure as a single. You have said that is "bad math" but you have yet to show "good math" that justifies a different conclusion.
 
Half Fast said:
Ed, if you'd learn a little math, you might have noticed that I made a sign error. The correct equation is 2P - P^2 and I've corrected my post above. It does NOT change my conclusion that a twin is twice as likely to have an engine failure as a single, a statement that you called "bad math." In the case of engine failures, P is a small number and the P^2 term becomes insignificant for the quality of our data.

In the coin example you seem to like, 2P - P^2 = 2(0.5) - (0.5^2) = 0.75. In the case of larger values of P, such as P=0.5, the P^2 term is not insignificant.

BOTTOM LINE - a twin is indeed twice as likely to experience an engine failure as a single. You have said that is "bad math" but you have yet to show "good math" that justifies a different conclusion.
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I knew you made the math mistake with the +/- from the beginning. Whether p² is significant or not doesn't change that it's not exactly twice as likely.
 
EdFred said:
I knew you made the math mistake with the +/- from the beginning. Whether p² is significant or not doesn't change that it's not exactly twice as likely.
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When did he say "exactly"? Here's what he actually posted:
Half Fast said:
Twins are twice as likely to have an engine failure and more difficult to handle when it happens.
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He then clarified that:
Half Fast said:
Neglecting that tiny additional P^2 term, the probability of an engine failure in a twin is indeed approximately twice the probability of an engine failure in a single.
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Here is how a lawyer might write @Half Fast's first post: "The following statement is a close approximation for values of P <= 0.1, which is an assumed upper bound on the probability of failure of an airworthy airplane powerplant, such assumption being fundamental to the following statement and therefore, if and to the extent such assumption is disproven by real world numbers or otherwise inapplicable to a specific powerplant, the following statement shall not be relied upon in any way by any person, and furthermore where 'close approximation' is defined to mean that the rate of error in the following statement is no more than the assumed rate of error for available data regarding P, which is assumed to be >= 5%, such assumption being fundamental to the following statement and therefore, if and to the extent such assumption is disproven by real world numbers or otherwise inapplicable to a specific powerplant, the following statement shall not be relied upon in any way by any person: Twins are twice as likely to have an engine failure."

I think that most people read @Half Fast's post with all of the italics in mind as the application of common sense to the numbers we are talking about in this thread. But there are certainly people who require an explicit and detailed expression of common sense to go along with basic statements. That is why a lawyer wrote a 10-page operator's manual for my snow shovel, and frankly it's why I have a job. So, on behalf of lawyers everywhere, we thank the 1% of people who give us 99% of our work. (Such statement being a close approximation &c. &c.)
 
Mongoose Aviator said:
While flying my twin, if one of the engines goes out, I am not looking for the closest place to land. I am looking for the best place to land. I would prefer a 6000' runway with emergency equipment available in case I botch the single engine landing. I am capable of flying extended distances on one engine. I have also done actual engine shutdown and restart in-flight while training such that depending on the reason for the engine failure, there is plenty of time to try an in-flight engine restart. A significant restriction on my twin when flying or landing on one engine is a seriously reduced rate of climb so as to make a go-around most unlikely to be successful. Hence, if I am coming if for a landing on one engine, I will get one attempt.

With two engines, I am comfortable landing on a narrow 2500' runway. For a single engine landing in the twin, I would prefer a wider 6000' runway. I fly in the NE portion of the US such that a good selection of airports is very feasible.
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I like to see how far away the 11,000' long military runway is. I can deal with paperwork and dudes with Berretas if that gets my family home safely.
 
MIFlyer said:
I like to see how far away the 11,000' long military runway is. I can deal with paperwork and dudes with Berretas if that gets my family home safely.
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Absolutely! I've always contended that I'd answer any questions, spend time in the clink, pay a fine, give back my certificates, or whatever ... but if I must land there right now to keep me and my passenger alive ... here I come!
 
I just want to survive long enough to attend the hearing.
 
Albany Tom said:
I'm going to make a different argument. If you're flying for fun, it should be for fun. If it's not fun, then don't do it. Maybe you just need a break, or should take some time to do something else. I believe that sometimes in hunches or bad feelings, we're got some data in our head that we've processed as a set of things that are "weird" and put fear around that, that could be justified and real. But we don't know what it is, because we don't have enough information about it to come to a clear conclusion. Just my 2 cents.
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That "Hunch" "Weird" feeling is where the "PAVE" and "IMSAFE" acronyms come into play along with the excellent risk/Mitigation example flyingcheesehead posted above. PAVE and IMSAFE are really just the FAA trying to put "Common Sense" into specific thought or actions. When you have these feeling these tools will often provide specific data as to why you feel that way, or with the risk/mitigation example may help you decided that you can or cannot mitigate the risks acceptably.

an example from a while back, considering a afternoon Glider flight...

Short version I just don't really feel like flying the glider this afternoon even though it is forecast to be a good soaring day.
Longer version
P - Pilot
I- Illness - No
M - Medication - No
A - Alcohol - No
S - Stress, My Wife just called and let me know my 18yr old son was in a motorcycle accident, He is not hurt, but they are going to retrieve the damaged motor cycle. Don't need anything from me, just letting me know.
F - Fatigue I have been up since 6am instructing in a Champ for the past 3 to 4 hours in Windy conditions.
E - Emotion, How is my sons accident and not know more details affecting me?
A - My Glider - Ready to go, Batteries charged, just need to assemble (in the wind), Glider doesn't do very good in crosswind landings (limited rudder authority)
V - Environment - Good soaring conditions forecast, but windy, wind currently down the runway but always have concern of it shifting later in the day when I am returning. Windy conditions often break up the thermals making it more work to stay in the lift and climb,
E - External Pressures - The other glider pilots would really like me to go fly with them

result: Help the other glider pilots launch, go home and watch their online flight traces to see how they are doing.

Brian
 
iamtheari said:
Here is how a lawyer might write @Half Fast's first post: "The following statement is a close approximation for values of P <= 0.1, which is an assumed upper bound on the probability of failure of an airworthy airplane powerplant, such assumption being fundamental to the following statement and therefore, if and to the extent such assumption is disproven by real world numbers or otherwise inapplicable to a specific powerplant, the following statement shall not be relied upon in any way by any person, and furthermore where 'close approximation' is defined to mean that the rate of error in the following statement is no more than the assumed rate of error for available data regarding P, which is assumed to be >= 5%, such assumption being fundamental to the following statement and therefore, if and to the extent such assumption is disproven by real world numbers or otherwise inapplicable to a specific powerplant, the following statement shall not be relied upon in any way by any person: Twins are twice as likely to have an engine failure."
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I love that lawyer-y description :D and a great way to end a spirited nerd fight.

But on that note I need to go take a bath with my toaster since nothing on the box warned me against making waffles in a submerged environment.
 
Mtns2Skies said:
Any recommendations on having healthy fear without it ruining it? Should I just STFU and press onward?
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How about doing what they teach students -- plan for the failure. Google Maps is free and easy. Plot your course, look for places where you could put it down along the way. As you're flying, keep looking for places where you could land. Practice power-off approaches and see how far you can glide.

In my early student days, I was skittish about stalls and worried about spins. Well, my CFI took advantage of this and that's all we did for the next two days until it became a non-event.
 
Mtns2Skies said:
As I'm getting older my risk tolerance is declining, particularly with relation to potential engine failures. More and more of my night flights and flights in the middle of nowhere with only forest below are me with an internal monologue of "An engine failure would really, really suck right now"... so much so that this stuff just isn't very fun in a single, and it's removing some of the joy of flying. I'm not sure that I can really afford to own or operate a twin right now, though that would certainly assuage some concerns. I didn't used to be such a scaredy cat, and it seems to be particularly surrounding an engine failure more than anything else.

Any recommendations on having healthy fear without it ruining it? Should I just STFU and press onward?
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The irony of this post does not escape me.
 
Salty said:
The irony of this post does not escape me.
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Greg, before you start down this road. My whole argument was that you increased the risk of your situation and acted unprofessionally, NOT that it wasn't a risky one to begin with. So clearly you are unable to see the irony of your own actions.

I have no idea why you are unable to have option 3 in your 2D mind which is 'You both did something wrong'.
 
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I believe I have made it clear that I do not want to use that name on this forum. It is EXTREMELY disrespectful to continue to do so.
 
Salty said:
I believe I have made it clear that I do not want to use that name on this forum. It is EXTREMELY disrespectful to continue to do so.
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It's also extremely disrespectful to carry over your petty butthurt into other threads after you got yours shut down.
 
Mtns2Skies said:
It's also extremely disrespectful to carry over your petty butthurt into other threads after you got yours shut down.
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So, it's ok for you to disagree with me in my thread, but not for me to do so in yours?

You were even willing to disagree with me without understanding the order of events. Your disagreement was based on your complete lack of actually trying to understand what happened. And even after that was made clear, you never admitted your mistake.
 
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Salty said:
So, it's ok for you to disagree with me in my thread, but not for me to do so in yours?
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You aren't talking about my thread, or disagreeing with it. You're lobbing petty BS that has nothing to do with this thread.


But since you want to open this can of worms too should we talk about risk tolerance with regard to unporting fuel causing an engine failure? Because that's not a risk I'm willing to accept either.
 
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Mtns2Skies said:
You aren't talking about my thread, or disagreeing with it. You're lobbing petty BS that has nothing to do with this thread.

But since you want to open this can of worms too should we talk about risk tolerance with regard to unporting fuel causing an engine failure? Because that's not a risk I'm willing to accept either.
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Safety is safety. Even if you choose to ignore the safety of others and I do not. Absolutely related. You weren't talking about my thread when you didn't bother to read well enough to understand the order of events described.

And you know more than the NTSB, who is actually inspecting my aircraft, but has not yet managed to make the conclusion you have. Is there a depth to which you will not sink? I'm sure we'll find out soon.
 
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People who live in glass houses shouldn't throw stones.
 
dtuuri said:
You could just schedule your night frights with this: 2023 Moon Phases - Calendar-12.com. That should help.
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I do look at the phase of the moon and the time of moonrise/moonset for night flights. Good light from a moon just makes everything a little bit easier. Not the only factor in my decision of course but certainly relevant to be aware of when planning and deciding whether to go or not.
 
Gentlemen, I enjoy both of yours posts and your contributions to the board, but IMHO it’s time to take this one private and settle things on PM.
 
Here is some comforting math. The fatal accident rate for GA is in the neighborhood of 1 per 100,000 hours (it's actually a little less than that, but let's keep the numbers nice and round). Powerplant failures are a small fraction (about 1/6) of that number according to the FAA. So your chance of a fatal accident, with average maintenance and average pilot skills, for a 1 hour flight is 0.001%. Now let's suppose you fly 1,000 hours over time. Your cumulative probability of a fatal accident, making assumptions of average maintenance and pilot skill, is (1-0.99999^1000) = 0.0099, or about 1%. You can improve your odds significantly by being "above average", that is (1) not becoming a member of the fuel exhaustion club, (2) not flying VFR into IMC conditions (3) meticulously maintaining your engine, (4) seeking regular proficiency training, etc.
 
I'm betting people who join the fuel exhaustion club are also more likely to belong in clubs #2, #3 and #4. Based on my observations in life it's quite rare to meet someone who is reckless in one area and Mr Captain Safety in another. And the more times you throw a coin with elevated risk - the more you're disproportionately begging for a crappy outcome.

Kind of makes me suspect the average stat might be misleading (overly pessimistic) for the true average pilot, whilst the risky pilot might get a false sense of comfort in believing they have a 99% chance of survival over 1000h of reckless flying.
 
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