# Service based failures - going over 250 hour maintenance period

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Hi guys.

I'm assuming that going over the 250 hour maintenance period and failing to service will increase the chance of component failure. Does anyone know exactly how this works?

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"Service Based failures will provide you with a highly realistic simulation of failures on and operational airplane. As you fly the simulator, the total flight time and system operation of the airplane is tracked. The combination of factors will be compared against known data predicting the Mean Time Before Failure for every component on the airplane."

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I've read that before, and no it doesn't, not quite.

So you get to 250hr mark, then what happens?:

• You run the service, does the MTBF restart for all components?
• You run the service, MTBF clock continues to run, but based on correctly serviced parts (less likely to fail)
• You don't run the service, the MTBF conftines to run, but parts are not correctly serviced (more likely to fail)

The above should hopefully clarify what I'm trying to understand.

I want to encounter some failures so just want to figure out what's going on. Am I better off running a higher time multiplier, not servicing, or both, for example.

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I'd like to know more about it as well. Service based failures are very interesting but could use some explaining.

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It is useful to review the meaning of MTBF here: https://en.wikipedia.org/wiki/Failure_rate

An item with a MTBF of 100 hours does not necessarily fail every 100 hours.  Rather it means that the failure rate is 1/100=0.01 and the failure rate is not a probability of a failure (it can be greater than 1). The probability of a failure within a give time depends on the hazard function, for example a typical hazard function has a higher probability at first call infant mortality, then decreases until late in the life cycle where it wears out. This distribution is a bathtub, and is most common in electronics for example.  I bring this up in this manner because I do not know what PMDG uses for the hazard function, it could be a flat or sloping linear function or nonlinear. Without know that there is no way to anticipate when a failure will occur even knowing the MTBF and  the interval of time being evaluated.

The clocks are simply runtimers.  The only way to reset a run timer is to replace an item such as a tire or after a failure which resets the clock.

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The failure will not happen when you want it to, or hope it does.

You will be on a nice relaxing flight showing a new girlfriend this beautiful plane and she will be feeling romantic because you are flying her to Paris when it fails.

You will not be ready and while you are looking through manuals you will lose control and crash.

She will question the feasability of dating a guy who doesn't maintain something as important as a commercial airliner and wonder:"Will he maintain a car, the house, the family?"

Then she will suggest just being friends.

LOL

I hope you encounter a failure soon.

• 4

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It is useful to review the meaning of MTBF here: https://en.wikipedia.org/wiki/Failure_rate

An item with a MTBF of 100 hours does not necessarily fail every 100 hours.  Rather it means that the failure rate is 1/100=0.01 and the failure rate is not a probability of a failure (it can be greater than 1). The probability of a failure within a give time depends on the hazard function, for example a typical hazard function has a higher probability at first call infant mortality, then decreases until late in the life cycle where it wears out. This distribution is a bathtub, and is most common in electronics for example.  I bring this up in this manner because I do not know what PMDG uses for the hazard function, it could be a flat or sloping linear function or nonlinear. Without know that there is no way to anticipate when a failure will occur even knowing the MTBF and  the interval of time being evaluated.

The clocks are simply runtimers.  The only way to reset a run timer is to replace an item such as a tire or after a failure which resets the clock.

Given the depth PMDG go into I wouldn't be surprised if they've researched all the above details for each component.

I would suggest in this case that the clock is more than just simply a run timer. As stated in the wiki article you linked, MTBF is based on parts operating under specified conditions. MTBF for a real part is clearly going to be different for parts that are correctly serviced and those not serviced at all. Again I wouldn't be surprised if PMDG have considered both, but this is exactly why I'd like to know how the service based failure system actually works.

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I use service based failures on all of my PMDG products. Great fun!

But on the 744 I've noticed the timer resets after every flight. :(

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Ummm....how do you enable this?

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Ummm....how do you enable this?

cant be certain of  the correct location but  iam sure  its  in the simulation  option in the cdu,  if  not  just check out  the other  options, its  expalined  also in the introduction manual as well

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The failure will not happen when you want it to, or hope it does.

You will be on a nice relaxing flight showing a new girlfriend this beautiful plane and she will be feeling romantic because you are flying her to Paris when it fails.

You will not be ready and while you are looking through manuals you will lose control and crash.

She will question the feasability of dating a guy who doesn't maintain something as important as a commercial airliner and wonder:"Will he maintain a car, the house, the family?"

Then she will suggest just being friends.

In that case, I don't have much to worry about, seeing as I've never had a girlfriend and don't see myself having one anytime soon. I don't crash planes, either.

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In the FMC: PMDG Setup->Aircraft->Failures->All Systems

But yes in the manual you can find extended explanation about it.

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In the FMC: PMDG Setup->Aircraft->Failures->All Systems

But yes in the manual you can find extended explanation about it.

Thanks, I only recently got the NGX again after a few years away (move from FSX to P3D).  Much to catch up on.

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But on the 744 I've noticed the timer resets after every flight.

I think the only thing that can cause this is not running the sim with admin rights, therefore it cannot update the hours files.

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I think the only thing that can cause this is not running the sim with admin rights, therefore it cannot update the hours files.

Funny is that on NGX and 777 I dont have that problem. Only on the 744, but I'm gonna check if with admin rights it will work.

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I'm looking at it now as well.  Seems my QFA -400ER has had several flights but the NEXT SERVICE IN value remains 250 hours.

EDIT:  Reason for that is I have not selected service based failures.  The 250 service is only required when service based failures are active.  Inside the hours file I see that the run timers are zero, which I'll check now that failures are enabled at the end of flight.

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Update:  After enabling service based failures the hour file is updated when P3D closes as expected.

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