I’m having reduced power / RPM compared to what’s expected in Cessna 172 Classic.
Starting at parking area of CYXH ~2300 ft MSL, plane is off. Live weather enabled, outside temp is -4 or -9 celsius (tried two different days), air pressure 29.85, calm winds. Go through the startup procedures per ingame checklist. What I’m finding is at full throttle, while parked, I can only get up to ~2100 rpm, and ~2300 rpm if I try for a take-off (which actually is a very bad idea at this poor performance… can barely climb). Fuel flow seems slightly reduced, it’s at ~17.5 per the guage. Screenshot attached. Maybe someone can see a problem in the settings or guages? I tried all sorts of different mixtures, didn’t help.
If I start on the runway with the plane pre-started, I get what I think is normal performance, i.e. parked full throttle rpm is ~2300, and 2500-2600 rpm in motion and no problem climbing out as usual. I notice that fuel flow is maxed out on the guage in this scenario, not pictured.
You don’t believe me when I said I tried multiple mixture settings? It’s a single screenshot. Do you need a photo of it in every position? As stated, I tried multiple mixture settings. It didn’t help.
Okay, does anyone else have different ideas? Because this ain’t it.
Here’s a silly thought: sort of like Sherlock Holmes’s "When you have eliminated all which is impossible, then whatever remains, however improbable, must be the truth .”…
The C172 is fuel injected so carb icing SHOULDN’T exist (or even be possible), but maybe the model is incorrect? Just seeing the ice on the windshield made me wonder. In real life, carb icing should also not be an issue at temperatures that low, but who knows what is modeled?
Two possible tests:
Try the keyboard shortcut for carb heat (because the aircraft does not have a carb heat lever) for a while at high power and try again without it
Go for custom weather and bump up the temperature to +20°C and try again
I know this is unlikely to the point of absurdity, but nothing else jumps out.
Thank you, will try your suggestions when I have a chance. I can tell you that previously when I bumped the outside temp to +14, things gradually improved over a few minutes, so I suspect it is weather related BUT worry that something is not being modelled correctly.
I also don’t understand all the ice, just sitting in the dry cold Albertan air on the tarmac. But that is another issue for another day.
Good thought. I didn’t inspect after engine stop, but from pilot’s seat it looked normal before starting. Also, didn’t notice ice elsewhere on the plane on exterior view. Though, it’s a white livery…
You could, with mixture, as a suggestion, change it to let the sim manage this for you and see if that makes a difference.
I suggest this as I had the same issue last evening in NZ and it was snowing. I changed the mixture setting to let the sim manager it… it don’t make a difference
I didn’t have any issues with those settings at that airport. I used full mixture, since your density altitude at those settings is slightly below sea level.
Regards
Amazing. Thanks for checking. But to confirm, did you start cold and dark? I do see your fuel flow meter is full, unlike mine, and also your EGT is not bottomed out like mine is. And it’s colder outside today it seems!
Is it possible I just need to run the engine for much longer time? I had mine at least 5 minutes going and still EGT was bottomed out.
BTW how to post full res screenshot? Mine sized down, not helpful when I’m asking others to scrutinize my cockpit.
I didn’t start from cold/dark. I’ll give that a try.
My normal screenshot program (basically from the gamebar WIN+ALT+PRT SCRN), gives me a png file, then I crop it down in paint 3d to what I want to show, and use the slider to enlarge the shot, then “save as” and select “image” to get a JPG (which is a lot smaller too), so I can delete the png file.
Anyway, I’ll run the sim again later today to start from parking and see what happens.
Regards
Thanks, yeah I only had the problem from cold and dark. When I loaded on the runway with plane running, seems normal.
That’s why I’m wondering if I did something wrong procedurally. Or there is some bug occuring.
I did check, the C172 POH stated startup procedures are not different in cold weather.
Ok, started from cold/dark. I was seeing your picture as -9C, so that’s what I ran (old eyes!). Anyway, I ran startups from -9 to +9C to see what I would get. At +9, it normally gives me about 2350 RPM, and if I lean it some I can get just under 2400. At -9C I got a little under 2500 without significant leaning.
The leaning portion isn’t in the startup section (or didn’t use to be!), but is normally found under the section that addresses “leaning for ground operations” (or that’s what it used to be called). Anyway, in this case of the sim, it didn’t give too much more RPMs, so probably not a specific issue here.
Regards
Looking at your EGT gauge the engine must be running very rich.
Otherwise you should see much higher temperatures in the exhaust gas.
There is of course no carb icing in a fuel injected engine, but there is induction icing….which also restricts air flow to the engine and will cause it to run rich.
At those temps and elevation the mixture in real life would certainly be full rich on the ground for run up and takeoff….but in FS you also have to lean the Cessna quite aggressively even just 2000’ up.
So I would try again full power and then lean until the rpm drops further and watch rpm and egt as you slowly do that.
Just did a quick cold & dark start with the steam C172 at Medicine Hat: could not replicate the issue. Ground run gave 2,400 RPM and EGT mid range of gauge. It did take a few seconds for the EGT to get there though, which is not completely unrealistic at those temperatures I suppose. This was at full rich: manual leaning behaviour was as expected FWIW.
