While FS9 runs like a champ on modern systems at higher resolutions, prop planes can fall victim to what I call "strobing" where the prop blurs tend to just sit there. Strobing is an effect that you could experience by waving a finger in front of a TV screen that runs on a refresh rate of 60 FPS. Props strobe when filmed for TV or movies, they don't strobe in real life.
What's happening tends to depend on your FPS settings, your resolution, and your frame rate. Suppose you run a frame rate in FS of 60 Hz. At 60 Hz the props will strobe when they turn at 3,600 RPM (60 Hz times 60 seconds equals an RPM of 3,600). For display purposes, 3,600 RPM is a bit of a sweet spot for FS prop planes.

You can get rid of this strobing effect in FS9 by simply adding a line to your Aircraft.cfg entries.

For this example, I'll use the WOP B-17G but it will work on any aircraft that features a prop connected to a reciprocating engine. Note that you'll need to add this edit to EVERY aircraft variation in the Aircraft.CFG file. I've tried to add a single line outside of the [fltsim.XX] fields but it doesn't work.

So, if we look at the B-17's config file, it looks like this:



[fltsim.0]
title=Boeing B-17G "Shoo Shoo Shoo Baby"
sim=B17G
model=
panel=
sound=
texture=
kb_checklists=B-17G Check
kb_reference=Reference
ui_manufacturer=Wings of Power
ui_type=Boeing B-17G Flying Fortress
ui_variation=B-17G "Shoo Shoo Shoo Baby"
atc_airline=Air Force
atc_type=Boeing
atc_model=B17G
description=The B-17 Flying Fortress is a very stable and forgiving aircraft which can absorb enormous amounts of battle damage and still make it home. It is truly a pilot's aircraft and is a pleasure to fly. It can be trimmed to fly hands-off for any normal flight regime and, while slow to maneuver, is quite responsive to the controls for such a large craft. While aerobatics are prohibited officially, there are many documented cases of B-17s being put into spins, rolls, stalls, and other acrobatics by instructors and pilots who flew the type. Pilots who flew all of the major American bombers of WWII -- the B-17, B-24, and B29 -- state almost universally that the B-17 was a joy to fly as compared to the other types. The B-17G differed from the B-17F principally in that it was fitted with a nose turret with twin .50 caliber machine guns and was slightly heavier due to this and other additional equipment. Otherwise the two types were similar.
atc_id=232076
atc_flight_number=
atc_heavy=0
atc_id_color=0000000000
visual_damage=0


All you need to do is add the following line:

[fltsim.0]
title=Boeing B-17G "Shoo Shoo Shoo Baby"
sim=B17G
model=
panel=
sound=
texture=
prop_anim_ratio=2.43174
kb_checklists=B-17G Check
kb_reference=Reference
ui_manufacturer=Wings of Power
ui_type=Boeing B-17G Flying Fortress
ui_variation=B-17G "Shoo Shoo Shoo Baby"
atc_airline=Air Force
atc_type=Boeing
atc_model=B17G
description=The B-17 Flying Fortress is a very stable and forgiving aircraft which can absorb enormous amounts of battle damage and still make it home. It is truly a pilot's aircraft and is a pleasure to fly. It can be trimmed to fly hands-off for any normal flight regime and, while slow to maneuver, is quite responsive to the controls for such a large craft. While aerobatics are prohibited officially, there are many documented cases of B-17s being put into spins, rolls, stalls, and other acrobatics by instructors and pilots who flew the type. Pilots who flew all of the major American bombers of WWII -- the B-17, B-24, and B29 -- state almost universally that the B-17 was a joy to fly as compared to the other types. The B-17G differed from the B-17F principally in that it was fitted with a nose turret with twin .50 caliber machine guns and was slightly heavier due to this and other additional equipment. Otherwise the two types were similar.
atc_id=232076
atc_flight_number=
atc_heavy=0
atc_id_color=0000000000
visual_damage=0



So, what's so special about 2.43174? I'm glad you asked. Not much, although its close to being an irrational number.
I could have also used Pi minus one or 11 divided by 7 with similar results.
One thing you should avoid are whole numbers. Using whole numbers can lead to "harmonics" at certain RPM settings.

Its also handy to try different numbers in the same CFG file. That way, you can load one of the entries to see how the effect looks during take off and during flight then switch to another plane in the same CFG file to see which number works better.

One thing that's important- the effect you see will probably be different than what I see. We all run the sim at different FPS. Play around with the numbers you use.