C152 - "Aircraft System Failure; Engine Malfunction" error

Bug Reporting Hub Aircraft & Systems
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1

ISSUE DESCRIPTION

Description of the issue: Flying the C152 in MSFS 2024 in Free Flight. Regularly (every 2nd to 3rd flight) encounter “Aircraft System Failure - Engine Malfunction” error mid-flight. The throttle is not on full power or full rich mixture in cruise, the weather conditions are clear with temperature and dewpoint outside of icing conditions, engine status is 100%, fuel is 50%, fuel selector is ‘Both’ and altitude no higher than 3000 MSL in the Mid-Atlantic region. If I let the plane crash, the flight resumes/restores from a point shortly before the crash with odd settings (trim, altitude, attitude, etc.). If I instead follow normal emergency procedures and land (random field or other), there is not a possibility to repair that I have found, so I end up having to restart the flight.

I have disabled (yes, ‘enabled’ the ‘Disable’ option) for Engine Damage and Icing to test. Realism is set to ’Modern’. Program restarted, system restarted, caches flushed, no mods, SU4, no double bindings on HOTAS or keyboard, not in developer mode and no developer options enabled.

How often does this occur for you (Example: Just once, every time on sim load, intermittently)?Routinely (every 2nd to 3rd flight).

YOUR SETTINGS

[PC Only] Are you using Developer Mode or have you made any changes to it? NO

[PC, MSFS 2020 Only] Are you using DX11 or DX12? DX12

[PC Only] What GPU (Graphics Card) do you use? GeForce RTX 5070Ti

[PC Only] What other relevant PC specs can you share? Ryzen 7 9800X3D, 64G DDR5, MAG B850 Tomahawk Max Wifi, X-56 Rhino, Honeycomb Alpha Lite/Bravo Lite, PiMax Crystal Light, 1GB coax cable internet.

Thank you in advance for your time and any input you may have to resolve this situation.

2

Exactly the same issue, only I was cruising at about 5000 ft.

The Engine Malfunctions, and ther is absolutely no way to restart the engine either manually or with Ctrl-E. All the gauges were normal before the crash. It crashed first with 51% fuel. Then with engine dead i CRASHED rthe plane on purpose, it restarted at 1000ft with engine running. Went up to 5000ft, everything normal except of course now 47% fuel, all gauges normal, and after about 10 minutes of cruising Engine Malfunction again. This is a systematic bug IMHO.

PC, no Developer Mode, no addons installed at all, CPU Intel i5-13500, GPU AMD 6750. I am a retired IT specialist, I run gadgets that show no abnormality. This is not a hardware issue. Please note that I have 34 years of experience flying every existing Microsoft Flight Simulator (except 2000).

Common bug with the Beechcraft V35B (also aspirated with manual mixture).

3

Can replicate the issue (SU5 Beta), after maybe 10 minutes of flight in normal conditions engine started to fail:

4

Did 2 more flights more than 20 minutes duration and no issue. Seems a random issue.

5

Yeah. I did three (3) ~30 min flights yesterday and on flight #3 it happened again. Luckily, I was on the taxiway as it was a short field. I even tried to lean the fuel for the cruise part of the flights and then return to rich in the pattern. Almost got tricked into thinking that was it. Tried it with ‘Auto Mixture’ setting and still happens. Rules that out, I guess. Lol

Will be interesting to see if it continues to happen when I upgrade my plane. I wouldn’t be sad if it was an optional setting you could toggle on or off. When on, it may occasionally have a failure and if you are able to successfully do an emergency landing then it gives you a badge or reward or something and then sets you back to as you were right before it happened to continue your flight. But having a goal/planned flight and then getting stuck in a field or on a road with no way to move on is a bummer. So I just let it crash and then let it spawn me back to some point shortly before the crash and try to recover the rest of my flight/altitude/cruise/trim/etc.

6

I have tended to see this issue when adjusting mixture at higher altitudes. The last time I ran into this, I had more than 50% fuel. I have been flying the default C152 when I’ve seen this. I have flown the aerobat C152 a little, but not frequently enough to know if this is an issue. Since CopernicoLucca suggests it’s occurred in the Beechcraft V35B, has anyone seen it in the C172 variants or other naturally aspirated airplanes? Based on my experience, it seems like it’s related to leaning mixture.

7

I appreciate everyone’s input on this. I am currently grinding through a refresher for stick and rudder pilotage in GA using NeoFly missions. So the C152 is perfect to force some of those habits instead of relying on Autopilot/G100/etc.

Recently I received a Honeycomb Alpha Lite and Bravo Lite, which makes things a lot easier to apply to flying as opposed to my X56 HOTAS in VR. I am currently thinking the same thing regarding the mixture being the culprit, so I am making sure to lean the mixture in the cruise part of the flights (per normal operations) to see if that is, in fact, the culprit. However, I have previously tried to utilize the Assistance option in MSFS 2024 for Auto Mixture and that did NOT remedy the situation.

FYSA. In my testing since using the Alpha/Bravo and after about 6 flights leaning the mixture 30-50% in cruise, I have NOT had any Engine Malfunction issues so far. I will continue to evaluate to ensure consistency and better validation of the potential solution.

I have not done testing with other aircraft as of yet but shortly I will set some time aside to test with more GA aircraft, specifically with respect to mixture settings and this problem. I have the C172 and Baron in mind for the initial aircraft to test the theory with.

I will provide updates as soon as I have done some testing. For reference, my flights are usually 30-50 nm and around 3,000 MSL (for the missions). I plan to extend those a bit with the faster/more capable aircraft as well since there will be different characteristics to take into consideration.

I will say that I am not mad if it IS, in fact, just the realistic representation and enforcement of proper aircraft operations and procedure. I actually find this encouraging as a learning lesson for users to reinforce realistic flight operations and awareness. My only critique, if that is the case, is this: If you include an option to enable Auto Mixture in the Assistance options it should remove any effects mixture should have on your aircraft. If it is me being a ■■■■■, I will gladly own that and adjust to improve my piloting operations knowledge.

8

I have been able to reproduce an engine failure 3/3 times with the default 152. I tried once with the C172 and once with the Aerobat 152 - those did not reproduce the issue like this. I’ll continue testing with both the default and Aerobat to see if those are different.

STEPS TO REPRODUCE:

  • Start on ground at KMSN parking lot 70+ East ramp.
  • Remove chocks and cover.
  • Enter plane - set full fuel, 175 lbs pilot, 20 lbs center cargo
  • Start engine - taxi to active runway.
  • Take off full power, trim for 68-70 knots.
  • Climb past 3000 feet - adjust mixture for 3000 feet while climbing.
  • Climb past 5000 feet - adjust mixture for 5000’ feet while climbing
  • Climb to 7,500 - 7,600. Reduce throttle to ~ 2500 RPM. Adjust mixture for 7,500 feet.
  • Trim for level flight.
  • Fly level 7,500 feet for 30+ minutes After about 15-30 minutes, an engine failure occurs.

This may be related to the amount of time the engine is at full/high throttle. Climbing higher requires more time at full throttle. I also found the DEV mode and the aircraft status screen for the engine. It has a lot of statistics and graphs. I noticed some changes in both, but was not watching close enough to determine what changed when the engine failed.

9

One additional factor - the C172s is fuel injected. C152 has a carburetor. Unsure if that matters, but it’s a difference in the engines.

10

Interesting. I wonder if it is a combination of factors. Carb Heat and Mixture. I can see where mixture would play a role at lower altitudes and so far (6 flights with reducing Mixture during cruise) I have not had an engine failure. All of the flights have been under 4000 feet. The temp/dew point have all had at last 3 degrees of positive separation.

At higher altitudes, I wonder if the engine failure is because of carb heat needed for lower temps (possible engine icing) and leaner mixture in a carbureted engine? I will have to continue to play around with it and see. I will post my findings from my experiences when I have some more data. Hopefully it, and the gracious input from all of you, will provide a minimal baseline aid for others to help make their experience more fun and less confusing/frustrating.

In the meantime, I have gotten in my stick and rudder pilotage refresh in and also have tuned my Alpha Lite and Bravo Lite to an acceptable level that I like. With that in mind, I am going to move on to the C172 and start the process over again shortly, since that is what NaviGraph Academy (academy.navigraph.com) uses for their integrated MSFS 2024 Virtual Private Pilot (VPPL) course which I am interested in taking through the paces.

11

I’ve had this happen several times over the past week. A trend I’ve noticed is altitude, although I haven’t tested it thoroughly.

All flights were operated at 75% power, slight lean of peak, and with more that 50% fuel. Flights above 4000 ft failed between 20 - 120 min after takeoff. All failures resulted in a red text box citing engine malfunction. All flights at 3000 ft had no failures, same power and mixture as failures.

No flights were conducted in freezing temperatures and I’ve experienced failures in both live and custom weather settings. Failures continued to occur after I disabled the engine wear and damage setting, as well as the icing setting.

My guess is that this is a bug, as I’ve not experienced it in any other aircraft. This all occurred on an Xbox Series X. Also, all flights started cold, shutdown on a parking ramp at the same airport.

I’ll follow up with updates in the near future.

12

This feels like a new issue. Several years ago I used Neofly to do a whole career, i recently came back and pretty much no matter what i do if i follow the flight plan to 3k ft within 20-30 minutes my engine dies and wont come back. Basically makes the plane unflyable.

13

Interesting. Try leaning the mixture after climb. Pull the mixture (red knob) out what looks like about 2-3 finger widths between the lock ring and the firewall/dash during your cruise. That is what worked for my testing (finally). Then in descent, I put it back to full, per procedure.

I am not sure this will work for you as well, but it does provide more data to the topic. Appreciate the input.

Neofly is a great free tool. I have enjoyed it for years. I recently coupled it with SayIntentions (since I do VFR/GA and waiting for BATC to complete their VFR) and it is super helpful in getting the cobwebs out and learning. I have also been using Navigraph Academy (free) for training in their virtual PPL course. It is good, but could use some polishing for maximum benefit. Will be interesting to see how their IFR courses turn out when complete.

14

Looking at the Wear & Tear display in dev mode, it seems the default C152 is set to have a fairly severe overstress effect when the engine is at max power, which will break the engine in a matter of minutes.

Screenshot from 2026-05-03 22-16-02x
Screenshot from 2026-05-03 22-16-02x1168×434 73.4 KB

Pulling the power back to 2600 RPM moves back out of the overstress zone.

Screenshot from 2026-05-03 22-16-11x
Screenshot from 2026-05-03 22-16-11x1130×443 71.7 KB

Standing still on the ground, I found max power only reaches 2600 rpm, and the overstress effect doesn’t occur, so it can only be experienced in flight.

This overstress effect does not occur in the Aerobat version of the 152.

I recall from the MSFS2020 flight training mode, that the instructor said that the C152 “needs full power to climb,” not just on takeoff, but any climbing at all. I think the overstress effect in the default C152 is probably a bug rather than intended, or at least, the engine health drain rate should be many times smaller than it is.

For now, I guess we’ll have to stick to 2600 RPM even in climbs.

EDIT: Disabling Aircaft Stress Damage in Assistances stops the entire wear & tear system, so that’s a solution in free flight, though it also means you’ll lose other damage effects like flap overspeed that you might want. (Disabling Engine Stress has no effect, funnily enough.)

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Hi Magenta Line - thanks for that tidbit on the Aircraft Stress Damage. I have about 200 hours of real C152 time - I can confirm the airplane should have no problem at full throttle - should be able to run all day long as it’s governed. The real risk is actually overheating on a warm day - those rentals ran hot in the summer.

16

I’m experiencing a similar issue with the C152. However for me the engine dies nearly instantly when I pull out the carb heat. Once the engine dies, it refuses to restart either manually or using the engine auto start shortcut.

I tried reducing the RPM slightly and leaning the engine for the altitude (lean of peak RPM) before engaging the carb heat but it still happens.

17

This is interesting. So here is what I tried, in an effort to understand your symptoms, and the results.

Carb heat pushed in; Master (Alt and Batt) switches on; Mixture full; Throttle at idle; Start

This started the engine and all was working fine, as expected. Carb heat pulled out - 100 RPM loss (expected). Pulled out Mixture and engine died (expected). Set Mixture back to full (in) and turned key to Start. Started the engine, as expected.

Carb heat pulled out; Master (Alt and Batt) switches on; Mixture full; Throttle at idle; Start

This started the engine and all was working fine, as expected. Carb heat pushed in - 100 RPM increase (expected). Pulled out Mixture and engine died (expected). Set Mixture back to full (in) and turned key to Start. Started the engine, as expected.

From this, I would recommend that you ensure that your Mixture is mapped correctly and used correctly. I am sure it is probably not the issue, but the first thing I would make sure was correct is that the Mixture setting is considered ‘rich’ when it is pushed all the way in and ‘lean’ when it is pulled all the way out. I had a friend that though it was reverse and also would pull the Mixture out more than half to lean which both led to the engine quitting.

Typically, I only use the Carb heat on approach to landing (low power/throttle conditions) and in icing conditions aloft. But don’t forget to ensure the Mixture is full (pushed in) if using Carb heat on approach.

I hope this helps. If not, please provide the system (console/PC) and scenario so I can better replicate to test. It may be a bug, but hopefully we can find a resolution.