At around 15 miles to my IAF, I started the descent from 9500 to 4000, and I also want to reduce the speed to 135 from 180. So, in set mix to 80%, prop control to 95%, and cut back on the throttle to just a bit above idle. Above 2.5 minutes later, a big noise was heard and both engines went. Took a look at the temps. The oil temp went throught the roof. My question is. Is the FSD's engine damage modulling based on CHT and Oil temp only? Both are more affected by prop rpm than other factors. Also, in a real situation like this, will engine damage occure?

Ummmm.Good question.I would suggest that you enter this on the FSD forum and/or shoot them an email off of their web page link.Let us know the answer.RTH

You wouldn't descend any turbocharged piston engine this way unless you're really into buying new engines frequently. FSD may have put shock cooling into the engine damage modeling and although this in itself wouldn't cause an engine failure it certainly would cause increased wear and tear. In most turbocharged piston aircraft the descent portion has to be planned carefully and in most aircraft you will not have the option of descending and slowing down at the same time, pick your poison. Rule of thumb for descent in any turbocharged piston engine is reduce MAP by 2" every two minutes till below 25" at which point you can reduce MAP with less worries, leave rpm in cruise position, advance mixture as you descend. Descend to traffic altitude for your airport of choice if flying VFR (and conditions allow) or your IAF altitude, then let the aircraft slow down and extend flaps, then gear when slow enough. You shouldn't run into cooling problems on descent but you will notice the engines running hotter as you slow the aircraft. Open the cowl flaps as necessary to keep the temps down.

You cannot treat TC engines the they were treated in this example. Shock cooing can indeed produce catastrophic engine damage, but as with engine abuse generally, that damage typically is cumulative to the point of unforeseen failure. Yes, these variables are modelled and this sort of abuse does accumulate damage points. The guidelines quoted above are a very good summation of how to treat an engine and they demonstrate the importance of good descent planning......Regards,http://www.fsd-international.com/team/Steve_signature.gif

OK. Got it and thank you all.BTW. Shock cooing is modelled.

Isorright, you're welcome. It's odd that they both failed ... the damage modelling parameters call for a failure of the left or right engine depending on accumulated damage : in the event they have both been treated the same, and accumulated damage units equally, the model calls for a failure of one or the other but not both simultaneously as you report. That is what our testing has demonstrated again and again, but in view of this report, we will look at the math model again.Thanks for this report !Best,.....Regards,http://www.fsd-international.com/team/Steve_signature.gif

I think my engine failure was due to high oil temp cause by high prop rpm (above 2200 but still in the green zone) on both engines.

This is really an evolutionary process and we do think it is worth continuing to refine it (damage modelling) rather than discontinue what is, for many, something seen as adding another dimension to FS. When we are able to offer the FSX versions of our products, all versions will incorporate as much as the new simulator will allow given that what we are doing (damage, pressurisation, hydraulics, complex electrical etc) isn't part of the standard FS environment. There have been evolutions in the C337 and Porter V2 that the Navajo does not include at this time. Exactly how far we can further refine this for FSX won't become clear for a little while yet, but we are committed to refining engine & systems damage modelling further......Regards,http://www.fsd-international.com/team/Steve_signature.gif

Steve,It's good to hear that FSD will continue with the engine damage modeling. I have left the failure modeling off in MSFS because I didn't feel it was very realistic in its application but I have used FSD's engine failure modeling since the first versions appeared and while I've had to perform maintenance I have had very little problems with the damage programming. I also appreciate the modeling of pressurization, hydraulic and advanced electrical systems and look forward to seeing what FSX will allow you guys to do.

Great. Looking forward to it. What are the extra system modulings in the C337 and the Porter V2 that are not in the Navajo? I have neither of them and your website is not exactly clear on the extra features.

In those later aircraft there is a much more realistic probability generator. Quite a bit more sophisticated. Also, it is not possible to have both engines fail except under some really extreme circumstances. In other words you will probably never see that happen, which is pretty much true in real life.The FS X upgrades will include a lot more systems modeling and failure possibilites. How expensive depends on the capabilities of FS X, which we won't know until it is much closer to release.http://www.fsd-international.com/team/TD_forum_sig.gif