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aurel42

Failures: MTTF/MTBF as timerange for a "realistic" experience?

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Hi,

 

if I set the "Fails in" timeranges for failures from 0 to <a ridiculously large number of minutes>, will I end up with an approximation of a realistic failure rate?

 

Without having done any research, let's assume typical mechanical instruments had an average of 10,000 hours between failures, can I set the "to" argument to 600,000 minutes for all mechanical instruments and end up with a failure rate that feels realistic?

 

I assume P3D rolls the dice on session start on when in the given time range a component will fail, and I will only experience the failures (if any) that fall into the first few hours of that very long time window? 

 

My goal is to have a (very small) risk of component failure, not a certainty either way. I want the sim to keep me on my toes, to surprise me long after I have forgotten about this setup change. I kinda want to experience the panic and/or confusion when it happens. I'm sure that will be very instructive.

 

Is this something you do, and, if so, how? Or is it a stupid idea, and, if so, why?

 

Bonus question: will the behaviour be more realistic if I always save the scenario at the end of a flight and always continue from this saved state? (in other words: are the dice that P3D rolled persistent across sessions if I continue a scenario?)

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I don't believe P3D keeps track of failure item data between sessions, at least I've never seen mention of it and do not know of the file that it would keep this information in between sessions. They do keep scenario errors in the saved scenario file, but I don't think this has anything to do with reliability.

 

Failure rate is a little more complicated than the model used by P3D, which is basically a random event time with a minimum and maximum time window.

 

The PMDG NGX and 777 have a very comprehensive failure feature and since they do keep track of failure item data between sessions for each individual tail number you have a lot more flexibility in designing your scenario.

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The PMDG NGX and 777 have a very comprehensive failure feature and since they do keep track of failure item data between sessions for each individual tail number you have a lot more flexibility in designing your scenario.

 

I'm vaguely aware of that, but I find no joy in flying airliners -- and I've tried! I have to make do with what I've got.

 

I'll just try experimenting with ridiculously large numbers, I guess I will have to see how P3D behaves.

 

Thanks for your advice!

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I am confused, you said you will experiment with ridiculously large numbers which led to me believe you hadn't read the section in the Learning Center > Getting Started > Aircraft > Setting Failures.

 

For equipment for example, you can set a failure to occur between a minimum time and a maximum time.  Using a very large time number, at least one longer than the length of your session, is the same as not having a failure.  P3D doesn't model a failure rate in any realistic manner.

 

But I am glad you set me straight and that you already understand this.  Let us know how the large number works.

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Oh, we've come full circle quickly.

 

 

For equipment for example, you can set a failure to occur between a minimum time and a maximum time.  Using a very large time number, at least one longer than the length of your session, is the same as not having a failure.

 

That's not my understanding. Example: I set a minimum time of 0 and a maximum time of 100 minutes for the failure of a component, then I do a 50 minute session. As I understand it, I end up not with the certainty of having a failure, or the certainty of not having a failure, but a 50% chance (or risk) of having a failure.

 

My original question was about this and about approximating (not simulating!) realistic failure rates by using much higher numbers than 100 minutes, ie. numbers like real-world MTBFs, in the thousands or tens of thousands of hours.

 

I'm grateful for your explanations about my "bonus question" from the original post, about failure data being persistent when saving sessions. I know now what I can't do. I can't use an aircraft without a "virtual overhaul" between each of my sessions, since P3D's failure "prediction" will be reset whenever I start a new session. 

 

I have to check and see what I can do. I still don't know, for example, if P3D actually handles a maximum failure time of 600,000 minutes correctly, or if it caps that number internally, and if it does, whether it caps the times before or after creating its set of failures for a session. If it doesn't save that failure information anywhere, I have no idea how to check this.

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I set a minimum time of 0 and a maximum time of 100 minutes for the failure of a component, then I do a 50 minute session. As I understand it, I end up not with the certainty of having a failure, or the certainty of not having a failure, but a 50% chance (or risk) of having a failure.

 

I agree with that, sorry I got off on the wrong track focused on it not providing a realistic failure rate. Since each session is an mutually exclusive trial, it will remain 50% each time and you'll probably have a failure in two to four sessions which becomes a Poisson distribution.

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Turns out, if I had done more than just the most superficial research, I wouldn't have had to ask that question. I learned two things:

 

1) P3D truncates my large numbers already when entering them. The "to" value is capped at 600 minutes. That's not enough for what I tried to do.

 

2) P3D doesn't seem to save individual failure configuration at all. No matter what I enter, when I quit and reload P3D, all the failure configuration is reset. So there's probably no way to circumvent the cap in the GUI.

 

There goes my dream. I guess I have to find a GA plane that simulates damage "externally", like the mentioned airliners do.

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There are a few possibilites. First, there's the freeware Maintenance and Income Tool (http://www.fsdeveloper.com/forum/threads/released-m-i-t-maintenance-and-income-tool.434351/)

This plugin can create random failures and also checks for damage (i.e. landing too hard). It's been a while since I've used it but I think you can configure the random failures rate as well as most other things. I think this may be just what you are looking for.

 

There are other tools available as well, such as Perfect Flight (payware), which can create random failures as part of it's features.

 

Last but not least, if you want a truly realistic simulation of failures in GA aircraft, there's no way around A2A's range of GA offerings. They have a full maintenance and failure simulation and are well worth the price. Also highly recommended is the Aerosoft DA-20 Katana 4X, which is every bit as sophisticated as the A2A addons.

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There are a few possibilites.

 

Thank you very much, I will look into all of them.

 

I did have A2A on my list of publishers to try, but I wasn't aware their aircraft came with maintenance and failure stuff -- is that what they call "Accu-Sim"?

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is that what they call "Accu-Sim"?

 

Yes, exactly. It models a lot of the aircraft's systems (such as oil, spark plugs, etc.) and almost anything can fail. I've had flap failures, fuel pump failure, instrument failures, and even an elevator failure (that one was scary!).

 

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Uh, I checked out this "Maintenance and Income Tool". I might be running a lot of confused code on my machine and never know it, because it's hidden behind a polished GUI, but in this case the confusion is so obvious that I'd rather not try.

 

Instead, I picked up the A2A Comanche. Thanks again for your advice, Don!

 

(The Katana isn't available for P3D. It seems updating the installers of their legacy products isn't among the highest of priorities for Aerosoft.)

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