Over the weekend I finished the first round of testing of my revised engine failure settings, and so far, I like the results.

Although my player-controlled aircraft had 0 failures in 11 missions, totaling 10.8 hours of flight (not unexpected, given I would have normally expected just 1 failure in 10 hours of flight), 60 AI aircraft experienced 6 failures in approximately 65 total hours of flight, which is right in line with what we would expect for a 10% per hour failure rate.

Of the six failures, five were "minor" failures, while one could be considered "major" (no fire), although the aircraft was able to successfully land at a nearby airbase.

I think I may tweak the settings slightly, in order to slightly reduce the chances of minor failure and to just slightly increase the chances of major failure.

Of course, keep in mind that any set of given findings can vary extremely widely, given the limited sample size, so we will have to see what happens with further testing.

OK BuckeyeBob, that sounds very promising

B.

Although I have made a few tweaks to the engine failure rules, I continue to get good results for the 10% failure rate setting. I estimate that my current failure rate, using these settings, is around 8%. More details later.

Sounds interesting BB -- haven't had much time (yet) to explore the engine failure mod. in detail, beyond my few posts early in this thread, but I definitely look forward to further results. Thanks for testing those various nos. further. Also worth keeping in mind, considering that your 10% failure rating is giving "real-world" (i.e., in sim) results of around 8%, is that there may be some kind of offset happening as I briefly speculated in one of my posts -- brief summary follows below (apologies for quoting myself):

"@All, speaking from the perspective of an old-school Mac user (thinking here in terms of object-oriented/end-user results in software) -- [but it may be the case that] the ratio between failure nos. in xdp (also in the sim.xml file) in WoFF and actual, in-sim failure results is not 1:1 but perhaps something like 1.2:1 or 1.5:1, depending on how failure algorithms/randomizations work in WoFF - [...] -- think of it as 'randomization offset' (offsetting for randomization that will err on the side of not giving engine failure, as opposed to giving engine failure)."

Anyway, one of these days I will pop into the simulation.xml file the nos. sets that I posted many posts back and that Bletchley suggested gave an ave. of 13% failure -- but will include some of your modifications BB to alter in favor of minor, as opposed to major, engine problems -- and will tweak/add about six or so individual engine failure nos. for some further aircraft xdp files (such as early Eindeckers) -- giving those about 15-16% ave. failure rate -- will then do some testing to see if that gives me overall "real-world/sim" results that are anywhere between 10-12% (nos. that I will be aiming for and that should give me a nice combo. between fairly historical nos. and seat-of-pants flying). Might take me several weeks to get to that however -- will continue reading this thread in the meantime and thank you to all who are contributing tests and number crunching to this thread -- "you've all done very well!"

Cheers,
Von S

I have completed approximately 20 hours of flight time for my aircraft and roughly 124 hours of total flight time involving 135 AI aircraft, with the following failure rules:

<FailureRule SystemID="engine_one" average_hrs="35" damageAmount_pct="12" dump="y"/>
<FailureRule SystemID="engine_one" average_hrs="60" damageAmount_pct="30" dump="y"/>
<FailureRule SystemID="engine_one" average_hrs="200" damageAmount_pct="62" dump="y"/>
<FailureRule SystemID="engine_one" average_hrs="150" damageAmount_pct="5" frequency_secs="112" dump="y"/>
<FailureRule SystemID="engine_one" average_hrs="275" damageAmount_pct="8" frequency_secs="30" dump="y"/>
<FailureRule SystemID="oil_reservoir" average_hrs="75" damageAmount_pct="6" frequency_secs="45" dump="y"/>
<FailureRule SystemID="oil_reservoir" average_hrs="125" damageAmount_pct="50" dump="y"/>

Here are my results:

My personal aircraft had 3 failures during my 20 hours of flight. Two of these were minor engine failures (the top line) and one involved a more serious failure (the fourth from the top).

The AI had a total of 10 failures in 124 hours of flight time. Five were minor engine failures (top line again) and five were more serious. Only one AI aircraft fatally crashed as a direct result of an engine failure, as best as I can determine.

I think these are acceptable numbers for a 10% failure rate. I particularly like the addition of the minor engine failure in the top line because I think it simulates quite nicely a "rough engine" due to a bad cylinder, valve, spark-plug, etc. I was still able to fly the plane and didn't really even notice the loss of power all that much, although I wouldn't want to fight a dogfight with it! There may be some room to perhaps increase the chances of a major engine or oil system failure a bit, but these numbers seem to work well, without being a source of frustration for the player. Keeping in mind that the number of failures depends, in part, on the number of aircraft in each mission, on average, one of the aircraft in either A or B flight experienced some kind of failure approximately once every two missions, with one stretch where my squadron experienced a failure in five out of six straight missions, with three of the five being minor failures.

BB

Looking good BB

I like the idea of your 12% damage line, it looks like a great addition.

I will add your numbers to my ongoing campaign and give it a whirl.

B.

I think I will lower the line

<FailureRule SystemID="engine_one" average_hrs="275" damageAmount_pct="8" frequency_secs="30" dump="y"/> to

<FailureRule SystemID="engine_one" average_hrs="250" damageAmount_pct="8" frequency_secs="30" dump="y"/>

but will otherwise leave these settings alone and keep on testing.

Thanks for your continued work on the engine failure mod. BB -- looking forward to further results. While tinkering with the Italian front mod. in PE/UE 4.18, I have in the meantime plugged in the following variation on stock UE/PE-era engine damage nos., and it immediately results in a world of hurt, so to speak:

<Failure weight="1.0" masterdisable="n">
<FailureRule SystemID="engine_one" average_hrs="40" damageAmount_pct="36" dump="y"/>
<FailureRule SystemID="engine_one" average_hrs="70" damageAmount_pct="75" dump="y"/>
<FailureRule SystemID="engine_one" average_hrs="100" damageAmount_pct="10" frequency_secs="106" dump="y"/>
<FailureRule SystemID="engine_one" average_hrs="140" damageAmount_pct="14" frequency_secs="30" dump="y"/>

<FailureRule SystemID="engine_two" average_hrs="40" damageAmount_pct="36" dump="y"/>
<FailureRule SystemID="engine_two" average_hrs="70" damageAmount_pct="75" dump="y"/>
<FailureRule SystemID="engine_two" average_hrs="100" damageAmount_pct="10" frequency_secs="109" dump="y"/>
<FailureRule SystemID="engine_two" average_hrs="140" damageAmount_pct="14" frequency_secs="30" dump="y"/>

<FailureRule SystemID="coolant_reservoir" average_hrs="50" damageAmount_pct="9" frequency_secs="27" dump="y"/>
<FailureRule SystemID="coolant_reservoir" average_hrs="45" damageAmount_pct="55" dump="y"/>
<FailureRule SystemID="oil_reservoir" average_hrs="100" damageAmount_pct="10" frequency_secs="45" dump="y"/>
<FailureRule SystemID="oil_reservoir" average_hrs="45" damageAmount_pct="55" dump="y"/>
</Failure>

Failure nos. above, plugged in to simulation.xml in PE/UE 4.18, gave a total of three engine failures for various flights of eight aircraft total (both friendly and enemy flights; this was in the Zepp-busting mission for the Italian mod.). One Alb. D.II experienced engine failure, as well as a standard Alb. D.III, and a SPAD VII. Two SPADs XIII, two Alb. D.V (170hp) variants, and an OAW-built Albatros continued along merrily. In short, the no. of aircraft failing was horrendous (37.5%) and immediately seen. Will perhaps post a few pics. under the Italian mod. thread. Moral of story: will leave stock UE/PE engine failure nos. alone in my PE/UE 4.18 install since the failure rate is already, with those nos., anywhere from 9 to 12% on average, I would say, given various factors and variables - possibly closer to about 15% in actual, in-sim results in my PE/UE install.

Stock UE/PE damage nos. follow below:

<Failure weight="1.0" masterdisable="n">
<FailureRule SystemID="engine_one" average_hrs="60" damageAmount_pct="31" dump="y"/>
<FailureRule SystemID="engine_one" average_hrs="90" damageAmount_pct="70" dump="y"/>
<FailureRule SystemID="engine_one" average_hrs="120" damageAmount_pct="5" frequency_secs="111" dump="y"/>
<FailureRule SystemID="engine_one" average_hrs="160" damageAmount_pct="9" frequency_secs="35" dump="y"/>

<FailureRule SystemID="engine_two" average_hrs="60" damageAmount_pct="31" dump="y"/>
<FailureRule SystemID="engine_two" average_hrs="90" damageAmount_pct="70" dump="y"/>
<FailureRule SystemID="engine_two" average_hrs="120" damageAmount_pct="5" frequency_secs="114" dump="y"/>
<FailureRule SystemID="engine_two" average_hrs="160" damageAmount_pct="9" frequency_secs="35" dump="y"/>

<FailureRule SystemID="coolant_reservoir" average_hrs="70" damageAmount_pct="4" frequency_secs="32" dump="y"/>
<FailureRule SystemID="coolant_reservoir" average_hrs="65" damageAmount_pct="50" dump="y"/>
<FailureRule SystemID="oil_reservoir" average_hrs="120" damageAmount_pct="5" frequency_secs="50" dump="y"/>
<FailureRule SystemID="oil_reservoir" average_hrs="65" damageAmount_pct="50" dump="y"/>
</Failure>

I will do some tests of the missions I am tinkering with, for the Italian mod., with the top set of failure nos. included in this post, in BH&H2, to see if the damage/failure results are not as drastic, on ave., as they are in PE/UE 4.18 -- and also to see if the nos. are a better alternative for BH&H2 than stock UE/PE failure nos. copied over -- if the 13% theoretical failure rate of that first set of nos. results in actual in-sim failure rates of about 10 or 11% in BH&H2, I will be pleased. I am/will be testing these nos. via the simulation.xml file -- will look later on into individual failure rates plugged into xdp files for some aircraft -- perhaps after I finish with my missions pack for the Italian mod.

NOTE: impressions above are for modified failure nos. in PE/UE-era WoFF -- future tests will involve plugging in such modified nos. into BH&H2.

Cheers all,
Von S

Impressive.

I can see why these settings generated such a high failure rate in UE/PE. It will be interesting to see them in BHAH2.

The current settings I am testing in BHAH2 to produce an average 10% failure rate have an hourly failure range of between 35 hours and 250 hours (I will probably bump up the lower number to 40 hours). I see that yours range from 60 to 160, with five of the eight being under 100 hours. You may want to increase those a bit or your AI pilots will have a very rough time, indeed!

Between helping take care of my dad and work on updating version 2.9.2 of the OCM, I haven't had much of a chance to do any significant testing of the engine mod. However, now that I made most of the changes I wanted to make to the cloud mod, I should have a little more time to do some testing.

Sounds good BB -- with real work and my on-and-off tinkering with the Italian mod., I haven't had much time to test the various engine mods. extensively on my rig -- so I look forward always to any results posted under this thread. Hopefully by the fall/winter I will have more time to start testing engine mods. too, more consistently than before.

Cheers all,
Von S

I have been using your figures BB, and have nothing untoward to report, but I am thinking that as your extra failure line results only in a loss of power of 12%, and does not generally force AI pilots or the human player to abandon the mission, this line might be added as an extra (e.i. not as part of the 10% failure rate) : so, major failures would still add up to 10% in early rotaries, with the added line as an extra chance of failure on top. As these minor failures appear to have been very common (often caused by dirt or ice in the carburettor or fuel line) it might be another 10% on top? (so, total chance of failure in early rotary !0% major failure + 10% minor failure, total 20%; but in late war stationary engines 2.5% major + 10% minor, total 12.5%) : <FailureRule SystemID="engine_one" dump="y" damageAmount_pct="12" average_hrs="10"/>

B.

I have noticed that when leading a flight, and having a 12% engine failure, the rest of the flight immediately de-select me as flight leader and choose a new one. I guess this must also happen to an AI flight leader - but does the former AI flight leader 'go home' or does he stay with the flight? As the former flight leader I managed to complete the Recce mission without lagging behind the flight, as we were already at cruising altitude when I had the 12% engine failure.

In my experience, flying as flight leader but leaving the AI in control of the plane, my AI pilot remained with the flight after a 12% failure. In fact, I didn't even notice that I wasn't flight leader anymore or that I had a failure until I reviewed the mission log.

I also believe that AI pilots who experience the 12% failure who aren't the flight lead remain with the flight. I'll have to check and see if an AI pilot with a 30% damage amount leaves the flight or not.

Depending on whether you think this is a good thing or a bad thing, we might consider raising the damage level to 14% or 15%.

I am OK with the AI rejecting me as Flight Leader (sniff!). I am quite happy to tag along and complete the mission that way. The only problem is that I generally ignore the waypoints when Flight Leader, so if it happens some way in to the mission the new AI Flight Leader will promptly turn the Flight around and head back to the forming up point before setting off again for the objective. If that happens I sometimes carry on towards the objective on my own, and take the risk of doing the mission solo.

Just to add, no, I am good with the 12% damage line. If the AI pilots stay with the flight, as you say, and try to complete the mission that is cool, I like it

I think I may have made a mistake, confusing the 31% damage effect with the new 12% damage effect - must have been looking at the wrong line in the log. I have just a flown a mission where I received 10% engine failure and, like you BB, I noticed no difference until I landed and checked the log. I have upped the damage to 20% just to see what happens now! I guess there must be a threshold level with engine damage where you get the clunk-clunk sound effect, and where the AI falls out of formation with a 'go home' instruction (and where the player or AI Flight Leader looses Flight Leader status).

One other idea - instead of (or as well as) the one-off 12%, you could have a small but cumulative damage effect: say, 1% damage repeated every 60 seconds. After this was triggered you would have a gradual loss of power, unnoticeable at first, until you hit this threshold level, and then you would get the above sound and other effects kicking in but damage would continue to accumulate only slowly. You could have this as an extra line, or replace the existing line <FailureRule SystemID="engine_one" average_hrs="120" damageAmount_pct="5" frequency_secs="111" dump="y"/> with <FailureRule
SystemID="engine_one" average_hrs="10" damageAmount_pct="1" frequency_secs="60" dump="y"/>

I have tested the above : <FailureRule SystemID="engine_one" average_hrs="10" damageAmount_pct="1" frequency_secs="60" dump="y"/> and I think it works well. With damageAmount_pct="1" frequency_secs="60" you are alerted to something being wrong with a "system failure" message that repeats every 60 seconds, and after about 20 mins the clunk-clunk engine sound effect kicks in. The engine very gradually looses power until the aircraft cannot hold altitude, and eventually you are forced to land - but not for a long time. I had the 1% engine failure start shortly before reaching target altitude, but managed to get up to altitude, fly to the target, complete the mission (a photo recon mission over a friendly airfield) and get back to base. I then flew round and round the home airfield, gradually loosing height and power, until I had to land. There were no further 'threshold effects' other than the clunk-clung rough engine sound, and this continued for the whole flight until I eventually landed and switched off the engine. I had thought that when I reached further damage thresholds I might get oil splatter or engine fire, but I didn't (or maybe I just didn't reach those shresholds before being forced to land). My AI wingman had a one-off 20% engine failure whilst climbing to altitude, and this initiated an immediate LeaveFormation and InitGoHome. He landed successfully back at the home base.

A further observation : I sometimes fly the two-engines Caudron, and I have noticed that when one engine suffers a failure, so does the other one. Although there are two separate lines (engine_one and engine_two) failures do not appear to happen individually. I am not sure if having the two separate engine lines means that the chance of that type of failure is then doubled for two-engine aircraft, or if the second line is redundant. I think I might test to see what happens to two-engine aircraft when there is only the engine_one line (i.e in this case does only one of the two engines fail, or do both still fail in tandem despite the absence of the engine_two line?).

Report back: With the engine_two line taken out a two-engine aircraft will only suffer failure to engine_one. So it is necessary! Further testing indicates that with two-engine aircraft failures to either engine CAN occur independently (see above)

I am now testing the one-off 12% failure line, changed to 15% to see if this initiates a Go Home event (20% does, 12% doesn't)

Report back: 15% doesn't trigger a Go Home event. I will try values between 16% and 19%

B

Just to pull together a few observations on the damage effects caused by various types of engine failure:

Damage to oil or cooling systems causes immediate heavy damage or lesser damage that accumulates quickly, resulting in immediate or within a short period of time (few minutes) a Leave Formation and Go Home

Generic engine damage requires at least 30 'hits' to the engine before any damage is done. but once damage has started it accumulates (if it is not a one-off event) and may or may not initiate a Leave Formation and Go Home either immediately or at some later point

This means that a one-off 'hit' of 12 will most likely have no apparent immediate effect (unless it is followed up by further 'hits', either by another engine damage event or by combat damage). It requires a one off 'hit' of at least 30-40 to cause damage and, possibly, initiate a Leave Formation/Go Home

A 'hit' of 1, with a repeating 'hit' of 1 every 60 seconds will produce no apparent effect for the first 30 minutes, but between 30-40 minutes in it will start to cause damage, but only slowly, and may initiate a Leave Formation/Go Home at some point (threshold for this appears to be variable)
.
Sound effect of damaged engine appears to kick in at the point that the engine starts to take damage (so, after 30-40 mins in the above case)

These can all combine I think in a random way - so, for example, a one-off hit of 12 would cause no immediate damage effect but could be followed at some point by an accumulating hit of 1 every 60 seconds...or oil/coolant failure...or another one-off hit, but I don't think having one increases the chance of having the other. Can also, I guess, combine with damage caused by AA or in combat with other aircraft.

B.

Thanks, B. I didn't realize you had added a bunch of information to your post of September 21st until I saw your post today. I was also distracted by my work on the cloud mod update, and I also got caught up in my investigation of the AI crashes during airfield and railway station attacks.

Lots of stuff to parse in your above two replies. In no particular order: first, I am confused about two-engine aircraft failures. Does damage always effect both engines, or just one? At first, you seemed to indicate that damage always occurs to both engines, but then you said failures "can occur independently (see above)." To what "above" are you referring to?

Interesting stuff about the "one-off" and accumulating damage effects. I could be wrong, but I don't think any of the one-off events--even the ones with high damageAmount percentages--eventually lead to catastrophic engine failures (I'm not sure about 50% damage to the oil reservoir--that could be an exception). In regard to your proposal of an engine failure that starts out very small and gradually accumulates (1% with a time interval of 60 seconds), I think I like that, but I may need to think about that a little more. You may wish to consider bumping it up to 2%, with a time interval between 90 or 120 seconds, so as to reduce the frequency of "system failure" messages a bit. I guess it will vary from aircraft to aircraft, but at what point would you say that engine damage affects your ability to fly: 20%, 30%, 40%, not to mention the mysterious "Go home" trigger?

Some quick calculations:

1% damage with 60 seconds frequency: 20% engine damage in 20 min, 30% in 30 min, 40% in 40 min, etc.
2% damage with 90 seconds frequency: 20% engine damage in 15 min, 30% in 22.5 min, 40% in 30 min
2% damage with 120 seconds frequency: 20% engine damage in 20 min, 30% in 30 min, 40% in 40 min (same time to failure as your proposal, but 1/2 as many system failure warnings).
3% damage with 120 seconds frequency: 20% engine damage in 13.33 min, 30% in 20 min, 40% in 26.67 min

The other thing to take into account, as you point out, is that all damage to a component, from whatever source, is cumulative. Therefore, if a bullet strike causes 3% of damage to an engine that already has had a system failure of 40%, you now have an engine with 43% damage (and only 57% as much horsepower)!

In regard to the 12% "minor" failure rule, I sort of like that it doesn't trigger an automatic "go home" event, allowing you to choose whether to continue the mission or not. One caveat, however: I don't know if the AI is smart enough to make that decision! I suggest either keeping it the same or setting it to a value somewhat short of the automatic go home trigger.

BB

I've done a little more testing and I am now pretty sure (Hidden to avoid spoilers. Click at your own risk)!



I think something like <FailureRule SystemID="engine_one" average_hrs="20" damageAmount_pct="2" frequency_secs="120" dump="y"/> represents the best compromise for this approach.

Cheers!

Edit:The above rules apply only to engine failures. The failure rules affect engines somewhat differently than other components such as oil or coolant reservoirs.

Hi BB, my last but one post was something of a stream-of-consciousness effort - I was just appending to it as I went along, over a number of days, so the end of it rather contradicted the beginning, as I found out more!

<FailureRule SystemID="engine_one" average_hrs="10" damageAmount_pct="1" frequency_secs="60" dump="y"/>

I am not sure that the damageAmount_pct="1" represents a 1% loss of power - I think it may be a single 'hit' to the engine (which can sustain 100 hits before it fails completely). From inspecting the log entries I think an engine can sustain up to 30-40 'hits' before there are any damage effects (such as loss of power, or the clunk-clunk damaged engine sound). Look at these log entries for an aircraft that sustained such damage:

At the start

2022/10/02 16:43:07 759.000000 failureStart alb_dva_sq2 0x04011019 engine_one 10.000000
2022/10/02 16:43:07 759.000000 0x04011019 RunFailure AddDamageToSystem_frac 0x00000004 engine_one 0.010000
2022/10/02 16:43:07 759.000000 0x04011019 overallDamage 0 / 10 dontTouchFlag 0 deadFlag 0 deletePendingFlag 0

The second and third line repeats every minute, until

Approx. 30 minutes later, there is a new line added with 1/65

2022/10/02 17:12:07 2499.000000 0x04011019 RunFailure AddDamageToSystem_frac 0x00000004 engine_one 0.010000
2022/10/02 17:12:07 2499.000000 0x04011019 overallDamage 0 / 10 dontTouchFlag 0 deadFlag 0 deletePendingFlag 0
2022/10/02 17:12:07 2499.000000 0x04011019 0x00000004 engine_one 1 / 65

This third line is then present every minute thereafter, but the 1/65 goes up to 2/65 a few minutes later

2022/10/02 17:15:07 2679.000000 0x04011019 0x00000004 engine_one 2 / 65

and then 4/65, after another two minutes

2022/10/02 17:17:07 2799.000000 0x04011019 0x00000004 engine_one 4 / 65

at which point, 2 seconds later, a Leave Formation/Go Home is triggered, approximately 35 minutes after the engine started taking 'hits' (i.e 35 hits, or 6% loss of engine power?)

2022/10/02 17:17:09 2800.687500 AIF::LeaveFormation Jasta 41-C ID(6002) 0x04011019 alb_dva_sq2 1
2022/10/02 17:17:09 2800.687500 TacsPush(TACS_TRANSIT_F) Jasta 41-C 0x04011019 alb_dva_sq2 APPEND
2022/10/02 17:17:09 2800.687500 AI_Formation::InitGoHome(GO_HOME_RUN) Jasta 41-C 0x04011019 alb_dva_sq2 td->code==TACS_TRANSIT_F
2022/10/02 17:17:09 2800.687500 TacsChange(TACS_GO_HOME) Jasta 41-C 0x04011019 alb_dva_sq2 REPLACE
2022/10/02 17:17:09 2800.687500 TacticsGoHome::InitGoHome GO_HOME_RUN Jasta 41-C 0x04011019
2022/10/02 17:17:09 2800.687500 0x04011019 goFriendly run newWayptIx 7 currWayptIx 4 route.size 8
2022/10/02 17:17:09 2800.687500 AIF::InitTransit Jasta 41-C 0x04011019 alb_dva_sq2 7 Landing

The aircraft continued to accumulate 'hits' until it landed with 20/65 which, I would guess, represents a 31% loss of power? I have also seen the "overallDamage 0 / 10" go up to 1/10 or 2/10 when there has been a lot of damage (representing damage to the aircraft structure from excessive vibration?).

So I think it is the 1/65...2/65 that is the start of the power loss, which also triggers the Go Home. The threshold where this starts to happen is not fixed. So far I have seen it occurring around 30-40 'hits', but the variation might be wider. The accumulation of 'effects' figure is not linear in the above example: it remained at 1/65 for three minutes before increasing to 2/65 and then 4/65 two minutes later (but I think it accelerates as time goes by). This makes more sense to me, the engine loosing exponentially more power as damage accelerates rather than a linear gradual decrease in power from 100%-0%. I think only damage types that have this 'accumulator' (frequency_secs=) get worse in this way over time.

Here is one for gradual coolant loss:

2022/10/02 16:56:51 1583.000000 failureStart se5a_sq1 0x04011034 coolant_reservoir 190.000000
2022/10/02 16:56:51 1583.000000 0x04011034 RunFailure AddDamageToSystem_frac 0x00000002 coolant_reservoir 0.040000
2022/10/02 16:56:51 1583.000000 0x04011034 overallDamage 0 / 10 dontTouchFlag 0 deadFlag 0 deletePendingFlag 0
2022/10/02 16:56:51 1583.000000 0x04011034 0x00000002 coolant_reservoir 1 / 38

The damage accumulates every minute: 2/38...3/38...at which point it gets the Go Home instruction and lands after 10 minutes with a total of 36 'hits' and 9/38 damage (27% loss of coolant? The drop in this case appears to be linear, a constant leak)

The one-off damage events are, I think, just that. I don't have a log entry for one now, but I have noted several including one for your 12% failure line), and they always look like:

2022/10/02 16:43:07 759.000000 failureStart alb_dva_sq2 0x04011019 engine_one 10.000000
2022/10/02 16:43:07 759.000000 0x04011019 RunFailure AddDamageToSystem_frac 0x00000004 engine_one 0.120000
2022/10/02 16:43:07 759.000000 0x04011019 overallDamage 0 / 10 dontTouchFlag 0 deadFlag 0 deletePendingFlag 0

with no further repetition.

A 'hit' of 30+ (e.g. 31) looks like that, but with the extra damage line, so something like

2022/10/02 16:43:07 759.000000 failureStart alb_dva_sq2 0x04011019 engine_one 10.000000
2022/10/02 16:43:07 759.000000 0x04011019 RunFailure AddDamageToSystem_frac 0x00000004 engine_one 0.310000
2022/10/02 16:43:07 759.000000 0x04011019 overallDamage 0 / 10 dontTouchFlag 0 deadFlag 0 deletePendingFlag 0
2022/10/02 16:43:07 759.000000 0x04011019 0x00000004 engine_one 1 / 65

but with no further repetition.

I hope that makes more sense!

So far as the two-engine aircraft goes, I think their engines can fail independently so long as there are two failure lines (one for engine_one and one for engine_two). If there is only a line for engine_one, then engine_two will not fail. But I get the impression that they may not be entirely independent - after one engine fails, I have noticed that the other one also starts to fail either immediately or at a slightly later time. But that may just be coincidence, based on only a very few observations. I will have to test more to confirm if this is the case.

"Damage that accumulates over time, e.g. <FailureRule SystemID="engine_one" average_hrs="150" damageAmount_pct="5" frequency_secs="112" dump="y"/> WILL result in engine destruction and/or fire when the hit points for the engine are eventually exhausted"

That may be so, or the engine might just conk out. We would have to test that. Or engine fires might be another 'threshold' event associated with a particular damage type, such as oil loss. I have not yet seen any engine fires in the logs as a result of engine failure. Does the engine reach 65/65 before it receives 100 hits? Or does one or the other cause an engine fire? I don't know, but I guess we can test for that...

"I think something like <FailureRule SystemID="engine_one" average_hrs="20" damageAmount_pct="2" frequency_secs="120" dump="y"/> represents the best compromise for this approach"

Yes, that would make the warning messages less intrusive - or even damageAmount_pct="5" frequency_secs="300" which would give the same result but even less intrusively.

B.

Good points, B.

Edit: I originally wrote a reply agreeing with almost everything you said in your above analysis, but the short answer is I think we need more testing. For example, what is the specific function of the damageAmount_pct value, and why does it also accumulate over time (not for the "one-off" events, obviously), along with the "1/65" value? BTW, I think the 65 in this case represents the total "hit points" for that particular component. I have noticed that that number varies, depending on what structure it refers to. Once that number is exhausted, the component is effectively destroyed, although it may not always result in a fire or other catastrophic event.

Along with you, I have also noticed that sometimes the 1/65 value ticks up exactly according to the value in the frequency_secs setting, but at other times it does not.

Perhaps the damageAmount_pct value sets an initial level of damage that ticks off only once the 1/65 value starts kicking in? And what determines when the 1/65 value is triggered?

Fortunately, we should be able to figure this out with more testing. Do you think we should move this to a private thread and invite anyone else, like VonS, who might be interested?