You may be interested to read this discussion as well over on the X-Plane forums. I went on a deep dive into radial engine descent practice recently and found this interesting. It also touches on gear speeds and such but I have tried to apply similar principles to the 18 and other radials as well.
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For VFR, I find I have to set MP down to about 15" Hg to get speed down to 109 KIAS to put gear down. I leave RPM at what I had set at cruise (~1850). This number is what I got out of various references, but in the sim, you can actually do that at higher speed (say 120 KIAS which Iām starting to use). I try to do this before entering the pattern and on downwind then lower gear and start bringing in flaps, and then raise MP to ~20" Hg or whatever needed to maintain desired descent rate and airspeed (~90-100 KIAS). Below is a exerpt from a checklist I cobbled together from various sources (other checklists, a couple of Youtube videos, various POHās):
Before Entering Traffic Pattern
Radios Set
ATIS Checked
Flight Instruments (Altimeter, etc.)** Checked & Set
Fuel Quantity** Check
Fuel Selectors (L&R)** Front Tanks
Tail Wheel** Locked
Brakes Check
Park Brake Off
Fuel Cross-feed Off
Seats and Seatbelts Check Secure
Fuel Booster Pumps** On
Mixture** Full Rich
Throttle** Reduce to Obtain 105 KIAS
(MP ~15-20ā Hg)**
Manifold Heat** On (Hot ā Down)
Downwind
Enter downwind @ 1000 ft AGL. When even with runway threshold:
Throttle** Reduce to descend (~15ā Hg)
Prop** 2000 rpm
Landing Gear** Down / Check
Flaps** 15Ā°
Landing lights On
Nav lights Flashing
Airspeed** 90-100 KIAS
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I finally had a chance to check out the latest version more thoroughly and really like the new features of the miniflow_L. The debug mode is very useful. Today I was starting engines on a hot day in Houston (>90 deg F) and the engines were not cooperating and eventually quit altogether before I even got a chance to taxi. I was able to use the debug mode to see that the issue was detonation caused by both high carb air temperatures and high CHTās. After repairing the engines, got things going again and with a few changes in procedure to avoid detonation, things worked just fine.
Would you please elaborate on this a bit more?
I had an engine failure in flight and suspect detonation as well.
Presumably you are familiar with the debug mode in the miniflow_L. You can find relative causes for high detonation rates in submodes 3 and 4 (see p . 37 of Denarq mod v1.5 manual). My overall detonation level (submode 2) was >5 for both engines with high D.RAT (high manifold pressures at low RPM) the highest (>4) contributor and carb temp the next highest >2).
Now, having said the above and reconstructing what happened, Iām not able to recreate the incident. When I started the engines, the outside air temp was ~90-95 deg F and the oil pressure would barely rise above 50 - definitely below the green. I thought maybe increasing rpm would increase oil pressure, so I opened the throttle more. I admittedly went too far and saw high manifold pressure (up to ~30" Hg) at rpm <1000. Clearly high enough for detonation.
After the engines quit, I repaired them and restarted and everything worked fine and I was careful not to open the throttle too quickly. However, the oil pressure came up to normal pressure right away. I donāt know what caused the low oil pressure initially - I had ~7.4 gal oil for each engine and engine wear was around 99% for each engine.
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Any chance this mod will be included in xbox someday? 
The market place enrolling process takes years for many developpers and itās only for payware products.
If they allowed freewares, that would be thousands and thousands more.
I donāt think weāll ever see that.
Yeah, unfortunately, based on Jorgās comments in the last Developers Q&A, it doesnāt sound like they will actually develop a freeware Marketplace. I think they realized itās just too much work and they feel the benefit for users to cost ratio isnāt worth it for Microsoft to implement it.
They are, however, adding a limited number of packages from freeware developers to the Marketplace. I think thereās a thread somewhere where you can vote for particular packages to be brought to the Marketplace. I recommend finding that thread, or starting a new one, and letting them know youād like this package to be brought to Xbox users.
But, given the restriction given from Microsoft for this to be developed to remain as freeware, since itās derivative of a Microsoft product, it may not be able to. Then again, given Jorg has a pretty big heart in regards to supporting users, and that he allowed this to be released in the first place, he might agree anywayā¦
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I figured out what caused my low oil pressure: I had inadvertently started the engines with the props at maximum pitch. I had my home cockpit controls (Honeycomb Bravo throttle quadrant) set to min pitch / high rpm before I spawned into the sim. The controls in the plane were set max pitch and, skipping in the checklist right to start engines, I never moved the prop levers, so they stayed on high pitch in the plane even though my throttle quadrant the prop levers were full forward. At least this is what I think happened as I have managed to do this againā¦ but now I know better.
I have learned some more about the debug mode and detonation in this airplane. It seems that a normal start of the engines will cause some detonation (DET1 or DET2 value between 4.5 and 5) with D.TM1 or D.TM2 between 0.3 and 2.5 seconds. I could see the MP get up to ~33 or 34 "Hg immediately after start before it settled down to idle (<1000 rpm). Looking at submode 3, only the D.RAT values were >1.
This didnāt cause engine failure, but Iām wondering if this would cause faster engine wear. When I spawn in on the runway with engines already running, I donāt see the high DET values.
Also, various aspects of a run-up seem to cause a bit of detonation as well. Testing the manifold heat and mixture also caused some detonation. In the case of manifold heat, of course, the D.CAR value was >1. Again, I did not see any adverse effects and the detonation (per D.TM values) lasted only a few seconds (total <10 s including engine start and runup).
Is this expected behavior? Am I causing additional engine wear?
I can see the same and wondered the same.
Guys, you just found a problem that was masked to me because of the way I start my engines.
If you let the starter start the propellers and only after a few revolutions (above 400 rpm)of the propeller turn on the magnets to start combustion, there isnĀ“t any problem.
But being this a simulator, usually because we canāt use our hands to operate switches like we would in a real airplane, the majority of people usually start the magnetos before the engine starter.
Iām guessing this is the way you start your engines.
Doing this way, there is a momentary surge in magnifold pressure right before combustion start, reaching very high values.
This should not occur and for now I donāt know why this is happening. It doesnāt occur on the default Beech so is definitely something in my code causing it.
Iām going to investigate to fing the solution.
In the meantime, if you canāt bind any button to both magnetos and if you donāt want this to happen, you can start using the starter without magnetos, and once RPMs are around 450 you can use just one magneto to start combustion. One single magneto has enought power to start the engine. Of course you will need to start the second magneto after that.
As soon as I have the solution Iāll update the mod in flightsim.to.
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Pretty much every page I turn on Iāll Take the 18 I think of flying this plane in MSFS with your mod. Itās such an excellent experience. Itās so cool to see that pages of this book have made it into the logic behind your tuning of the airplane.
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Question - possible to mount the GTN750 in this plane with the Denarq mod?
This mod doesnt but Jaydees mod might:
Guys, I believe the problem with detonation and manifold pressure surge on startup is fixed. Iām going to do a few test flights and I hope an update will be release later today.
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New update v1.5.1 is out.
This update only fixes new found startup bugs and includes flightmodel changes already addressed on post 945 of this topic.
Denarq Enhancement Beech D18S
Log V1.5.1
Improvements:
(Both these two improvements are the same already addressed on a temporary file available on MSFS fĆ³rum)
-Improved ground handling when using free castering tail wheel.
-Improved flight model to reduce roll rate.
Fixes:
-Improvement in detonation calculation to avoid non-existent detonation during engine start-up.
-Correction of the rought-engine formula to prevent manifold pressure surge during engine start-up.
18 Likes
Just wanted to say thank you a thousand times for this mod. Itās really awesome and gives the D18 real character. Iāve flown the heck out of it and love it.
Do you have recommendations for good climb and cruise power settings. I seem to be beating my engines up quite a bit more than I expected. Iāve been running at 28" and 1800rpm at ~75 degrees lean of peak and Iām wondering if thatās too high a MP to RPM ratio.
Also, another oddball issue Iām having. Neofly and your mod seem to conflict when trying to add fuel & oil through the W&B interface. I suspect itās Neofly trying to govern the fuel settings and somehow conflicting with the oil level checking routine youāve included with the oil cutoff knobs. My workaround is to accept a mission in Neofly, close Neofly, set the W&B, fuel, levels, then reopen Neofly. Itās clunky, but it works.
The problem seems to have gotten worse after installing the Sky4Sim virtual tablet with Neofly. Though uninstalling it completely and removing all related files didnāt seem to undo the issue.
Slightly off topic, but there is a NF setting that is supposed to try and sync fuel settings with the sim. If thatās on, turn it off and see if that fixes the problem.
I bet that will do it. Thanks for the heads up! Iāll give it a shot.