Engine starting/stopping concern(s)

[N602AC]

Hi there.

Before I begin, I'd like to say that this 172 is the best GA aircraft ever made for FSX without question. Everything that A2A has done with it goes so much farther than other developers probably even imagine. This post is in no way meant as negative criticism and should not be viewed as such. This issue has been in my mind since yesterday and I need to let it out on here, where it should go. My only hope with this thread is to voice my opinion on what I view as a very, very, very important yet small change that should/could be made in, perhaps, a core Accusim patch. I grew up flying in all kinds of GA aircraft and have countless memories of engine startups and stops of Cessnas just like this one (one of which I have hours in my logbook from) and many other horizontally opposed aircraft engines and even others. I shall provide some video evidence to support my opinion about the issue at hand as well.

OK.

I noticed this issue first in 172 preview video part 1 of 3.
When cranking the engine, it seems that the starter is very overpowered. Using the starter alone with no fuel and mags off, you can make the engine rotate so fast that the prop becomes a blur.
I got the 172 yesterday and must say I'm very very very impressed with it. But my fears from the video were confirmed. In the real world I have never, ever, ever seen a starter that was able to make the prop spin so fast that it became a blur on any aircraft.

Have a look at this video: http://www.youtube.com/watch?v=B97gTf2DMdY

Notice the sound of the engine very carefully. Also notice how the prop does not become a blur until the engine fires.

Basically what I'm trying to say here is that the starter should turn the engine slower than it does. I have no idea what it takes to program something like that, but if it were at all possible I would say that issue should be addressed in an update along with the torque issue I read about in a different thread.

Also, my other concern is when you finish a flight and pull the mixture to stop the engine, the prop remains as just a seemingly fast moving blur until a fraction of a second before stopping. In the real world, the prop isn't blurred nor is it visibly percieved as spinning so fast for so long, so you can really see the effect of cylinder compression at work. I am sure whoever programmed the compression probably wouldn't want his hard work to be overshadowed by the prop blur not being set up correctly. I wonder if the real problem is just that the threshold at which the propeller becomes a blur should be raised? (EXAMPLE: Prop goes from 3d model to a blur at 100RPM, should be ~300RPM - Just as an example) Here is a video that will support this second point of the blur and compression issue at engine stop. http://www.youtube.com/watch?feature=pl ... eSZRs#t=15

I ask everyone else reading this to please, voice your opinion on this specific issue as well. If anyone needs me to clarify or further explain, please don't hesitate to ask or PM me. It is a great concern of mine to hear what everyone else thinks about this.

Thanks!

[DABspotting]

I second this and agree 100%

[CAPFlyer]

Guys, you are assuming that the graphical representation of the prop is a physically modelled thing and it is not. The prop looks like a blur because FS does not handle a slow turning prop well and thus you have to transition to the "spinning prop" texture at a very low RPM. Maybe they can tweak the texture transition speeds, but the better way to tell how fast the starter is turning the prop is to look at the prop RPM gauge.

[N602AC]

Guys, you are assuming that the graphical representation of the prop is a physically modelled thing and it is not. The prop looks like a blur because FS does not handle a slow turning prop well and thus you have to transition to the "spinning prop" texture at a very low RPM. Maybe they can tweak the texture transition speeds, but the better way to tell how fast the starter is turning the prop is to look at the prop RPM gauge.

Then how is it that the B-17, P-51, and B377 prop behavior on startup is correct?

Also, I just did a little test. Cranked the engine with a full battery, it sustained 100RPM which actually seems what I would think to be perfect. So it seems to me that the blurring is definitely happening too soon. (Like I said earlier, blurring may start at ~100RPM and should start at ~300RPM, just as an example)

[Scott - A2A]

When I first flew the later model Cessna 172R's, I was amazed at the speed of the starter too and it cranks much faster than other aircraft I had flown before. The 172R has a much higher speed starter than showed in that video, approximately 2X faster. The 172R spins the prop so fast, it can develop almost 50psi oil pressure. It is on the edge of blur to our eyes when sitting in the cockpit and what you are seeing is the blur texture kicking in and out in FSX.

When we do the older cherokee or Comanche, for example, it will look almost identical to the video you posted with no blur.

Scott.

[CAPFlyer]

The rotation speed on the radials and the P-51 prior to start is much lower (in the realm of 50-60 rpm max), which is below the transition point for the textures.

As Scott said, the 172R has a very high powered starter compared to most engines. The first video you link is of a C-172N or earlier which has a different starter. Additionally, that battery is definitely drained a bit and the starter worn because I've seen 172N's spin much better than that one.

Also, remember that there's a huge difference between watching a video and seeing it in real life, especially when dealing with digital cameras that are not designed for high frame rate capture. That's why it's so hard to catch things like strobes on even "high definition" cameras.

[N602AC]

When I first flew the later model Cessna 172R's, I was amazed at the speed of the starter too and it cranks much faster than other aircraft I had flown before. The 172R has a much higher speed starter than showed in that video, approximately 2X faster. The 172R spins the prop so fast, it can develop almost 50psi oil pressure. It is on the edge of blur to our eyes when sitting in the cockpit and what you are seeing is the blur texture kicking in and out in FSX.

When we do the older cherokee or Comanche, for example, it will look almost identical to the video you posted with no blur.

Scott.

If you think of a clock that ticks twice every second, (that's 120 per minute) then remember the starter RPM is 100, then thinking of the prop turning 100RPM and being a blur but the engine is only turning a little more than one revolution per second so it just doesn't make sense to me that the prop appears to be a full-on, disc blur. Is there any way for me to adjust the blur threshold on my computer at least? Better yet, can the prop blur be dynamic? So it is only very slightly blurred while starting (the blades appear very individual still) and then blur more as RPM increases?

Thanks..

[CAPFlyer]

Yes, but the Lycoming starters will turn the prop at up to 240 RPM, not 120.

[Scott - A2A]

I went flying today in 74H, which is one of the C172R's we fly. I paid special attention to how the prop looked when it cranked, and it is definitely a blur to my eyes. Now this doesn't mean it would be blurry to everyone's eyes. As soon as I returned to my studio, I cranked the engine over and now remember why I set the blur where I did. Because, when the prop rotates past a certain speed, it's starts being seen as multiple props on the screen due to the framerates. And this just plain looks bad.

But the way we have it tuned now, it looks closest to what I saw just today with my real vision. The 172R has a great starter. Also, keep in mind, a stronger battery also means a faster crank too.

Scott.