414 RPM Dropping Over Time

[gavco98uk]

I've updated to the latest version of the 414, but Ive recently been having some problems that are making the aircraft unflyable.

I climb to around 4,500 and turn on the autopilot, and begin flying the route. Over time however, my speed just seems to drop off - RPM drops too, and engine temp is at the bottom of the scale. Slowly the RPM and speed continue to drop off until the aircraft stalls and crashes. 

 

Whats going on? I'm on full throttle. Ive tried adjusting the mix as well as setting auto-mixture, but always the same... speed and RPM just drop right off to the point it stalls. 

I managed to do a few flights in this aircraft a few weeks ago, but now it seems impossible. What am I missing here?

[MaDDogz]

42 minutes ago, gavco98uk said:What am I missing here?

Just a guess based from described symptoms, carb heat? ( never flown it though)

[somiller]

Cowl flaps open/engines over-cooled (does the 414 have cowl flaps)? No idea if his could cause your issue, but just a thought.

[croudson]

Did you check to see that you had not run out of fuel?

[Lerxtwood]

FWIW, I have this exact same problem, but for me it ONLY happens when I'm flying at full throttle with the manifold pressure up around 40-41 inches. If I back the throttle down to set the manifold pressure in the green (26 inches) I don't see the problem.

I have tried messing with the cowl flaps, etc, but nothing seems to change the behavior other than backing the throttle down into the green as I mentioned above. I reported this over on the FS2020 forums and had some other guys try to dupe it as well, but they didn't seem to have the problem even when flying full throttle.

Strange that I consistently have the problem when many others do not though.

For any interested, you can see that conversation starting about here over in the FS2020 forums:

https://forums.flightsimulator.com/t/flysimware-cessna-414a/497038/1411

 

[Adrian123]

10 minutes ago, Lerxtwood said:

I'm flying at full throttle with the manifold pressure up around 40-41

Probably burning pistons flying at that king of MP for any amount of time.. That's what the green is for. TO at 37MP, clm at 34 mp cru at 28mp.

[Lerxtwood]

5 hours ago, Adrian123 said:

Probably burning pistons flying at that king of MP for any amount of time.. That's what the green is for. TO at 37MP, clm at 34 mp cru at 28mp.

Understood. I try to always keep manifold pressure in the green, but just letting the OP know that I see what he sees when I'm wide open throttle (since he also mentioned he's flying full throttle when he sees this).

And, I wasn't sure if engine damage was really modeled in this 414 or if this was just a bug, or unexpected behavior at least, where others have commented that they can fly full throttle for entire flights without ever seeing this problem.

Thanks for the reply!

[TacomaSailor]

The POH shows continuous acceptable power setting to be 38.0" Hg up to 20,000' with a max head temp of 460° and Max oil temp of 240°.

Are you exceeding those limits?

The POH also shows Normal Operating MP is 31.5" to 34.0" at 2200 to 2300 RPM with oil temp 75° to 240°

The upper limit power is 38.0" at 2300 RPM (Red Radial)

Are you within those parameters?

Max NORMAL fuel flow is 186 pounds/hour at 21.1 psi.  

Max allowable fuel flow is 195 pounds/hour at 22.5 psi.  

Is you fuel system delivering that amount and pressure?

[gavco98uk]

On 6/5/2022 at 11:31 PM, Lerxtwood said:

Understood. I try to always keep manifold pressure in the green, but just letting the OP know that I see what he sees when I'm wide open throttle (since he also mentioned he's flying full throttle when he sees this).

And, I wasn't sure if engine damage was really modeled in this 414 or if this was just a bug, or unexpected behavior at least, where others have commented that they can fly full throttle for entire flights without ever seeing this problem.

Thanks for the reply!

thanks - that seems to have helped. I'm just doing another flight, and got the same issue once again. I throttled back to ensure the manifold pressure was in the green, and descended to increase speed (stall warning was sounding). Over time the engine has recovered and EGT has risen from 12 (min) back to the green, and speed has increased to 180.

It seems that this is something that is simulated.