MCDU Freeze loading flight plan

[BoeingSpeedbird]

Loaded into EGPH at departure gate. Started to load flight plan into MCDU from Simbrief and MCDU frozen - cannot select or input anything. Having to restart MSFS2020 again. Frustrating. 

[richboy2307]

Hi @BoeingSpeedbird

I have moved the topic from MSFS 2024 to 2020 section as that is the sim you're using.

This does sound like a WASM crash, however we need to determine if this WASM crash is a fault in the aircraft code (and thereby reproducible) or sim code (random, will happen sometimes but not always).

Please see the information below to see if you can reproduce the issue reliably, and if yes, then please post exact reproduction steps. 

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What is WASM? 

Quote

WASM is an acronym for WebAssembly Module, and Microsoft Flight Simulator uses WebAssembly for scripting. Most commonly this means aircraft instruments, such as controls, panels, and displays, will function as intended (without WASM these instruments may not function at all or would function incorrectly). However, WASM usage is not only limited to aircraft. 

- Microsoft FAQ

Why do WASM Crashes happen?

These can be caused by either a) faults in the code, or b) in the way that code is executed by the sim.

a) Faults in Code

While we try our best to find and quash all bugs in code, we are still human. Mistakes or oversights can happen and sometimes these can lead the code to fail in certain specific instances, resulting in a WASM crash. These kind of crashes will be reliably reproducible, meaning you can have the crash nearly every time by executing the same code (e.g. by selecting something on the MCDU, or by pressing certain buttons on the plane, or by flying certain SID/STAR/APPROACH etc.)

These types of WASM crashes are actionable, and dependent on your reports of the steps taken immediately before the crash happened. These, if reproducible on our end by following the same steps, can be debugged and usually resolved in a following update.

b) Faults in the way the code is executed by the sim

Since SU15, we suspect, there have been instances of "random" WASM Crashes caused by a "memory allocation bug", wherein the sim tries to reserve memory (for WASM) that it does not have access to, as a result leading to a WASM crash. These types of WASM crashes are difficult to reproduce and not something we can address as its not an issue with the aircraft code, rather just in the way the sim tries to store and execute it in some instances.

These types of WASM crashes are not actionable on our part and would instead need fixes on the simulator's code (if possible).

So why did you experience a WASM Crash?

As mentioned above, we will first need to find out if the crash was (a) or (b). So you need to take note of exactly what you pressed or things you did, just before you noticed this crash happen.

In case of MCDU Entries, we need the exact procedure entered, and at which step the issue happened (when you selected the runway; or the SID/STAR/Approach/Transition; or when you pressed insert after selecting which exact procedure)

What systems stop responding, or what you cannot click after the crash is irrelevant as the whole WASM has already crashed, so anything using WASM will equally stop responding.

Additionally, please see if you are able to repeat the crash by following those same steps. Once you know, you can mention those steps to us, and we can try to reproduce on our end to see if its actionable.

Thanks!