Engine spooling
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Thanks for the feedback everyone. The engine response times are custom-coded based on videos taken in the real RJ. It would be expected for the spool times to be much quicker than higher-bypass engines that you would find on an A320 or 737 as there's a lot less rotating mass in the LF507s by comparison. I will bring this up with our development team though just to double-check everything.
With regards to some systems (like the TRP and YD) not being functional following a change of aircraft state on the EFB, this possibly could be misunderstood for the FGC test. If the aircraft's power supply is changed when switching states (such as Cold and Dark > Turnaround) an FGC Test will be triggered once the power is restored. Off the top of my head, the FGC Test takes 45 seconds to complete after power has been applied to the aircraft and during that time, a few systems such as the TRP and YD will not be functional. Once the FGC Test is complete, an FGC PASS message will appear at the top right corner of the PFD.
I suspect it may be possible to confuse the FGC Test logic if a change of aircraft state is made before an FGC test is completed (I.e. if the aircraft state is changed from Cold and Dark > Turnaround, then 10 seconds later to Ready For TO). I doubt it would be an issue if only one aircraft state change was made every minute. We'll do some tests with this to see if we can break that logic and if so, prevent that from occurring in the future.
Mark - Just Flight
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Hey Mark and team, just wondering if you had managed to double check this with the development team? It really does feel like the spool up and down at low n1 values is a bit too quick? I appreciate these are small engines, but every video i've seen (and admittedly old memories of being a pax on an RJ) the spool at low n1 values was quite a bit slower... Appreciate your input
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There aren't any plans in place at the moment to revisit the engine spool times in the RJ. From the data we have and the input from the pilots on our testing team, the fast engine spool is accurate to the real aircraft. As you say, they are smaller engines, so there isn't as much mass to rotate as there would be in larger engines.
Mark - Just Flight
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Hi Mark,
I understand your point about the smaller engines having less rotating mass, but on the real aircraft the spool-up is still not instantaneous.For example, in this video at 16:35(https://youtu.be/W1koU46-7Gs?si=qym4gmRV2FtKUPGc&t=991), you can clearly see that there’s a noticeable delay in N1 acceleration compared to what we see in the sim. It’s of course quicker than on a big turbofan, but still progressive and not “immediate.”
Maybe the current model could benefit from a slightly more gradual response to better match the real behaviour.
TY
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Hi, pauleti68,
Something to consider is how the Thrust Levers are handled by the Pilots. Yes, I could slap the levers forward and get the thrust I want very quickly. On the other hand, I could be less aggressive with the Levers and achieve a slower acceleration. What I'm trying to say is every application of thrust is variable. But having over 2000hrs on these planes, I can confidently say the simulated rates are very accurate. As has been mentioned, they're small engines. There's not a lot of energy needed to get them rotating. There's a slight difference between the 146 and RJ, as the RJ's have FADEC. You could even argue there's a difference between the 507 engine variants on the 146 (different engine fuel system, not pilot controlled), but that's getting too deep into it. -
Hi Mark and team,
I've had a bit of a breakthrough realisation with regards to my above comments... For context, I'm an audio guy, and I use my ears for a lot of cues when simming.....
The engine FADEC n1 spool does seem correct - what seems to be incorrect is the sounds....
To demonstrate: Set a view so you can see both the thrust levers and the engine instruments... Now, advance your hardware throttle rapidly to 50%, and observe the n1 and listen to the sound. The sounds will almost instantaneously increase in pitch/volume, whereas the n1 indication is still spooling up.
This makes me think that the engine sounds are (currently, wrongly) tied to thrust lever position rather than n1. I would suggest that the engine sounds should be linked to the n1 behaviour.
Here's a short video that demonstrates this:
https://streamable.com/ihpe3a
Be interested to hear your thoughts - happy to explain further if it's not clear from my description/video.
Thanks!
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I have posed this query to our sound developer, and they confirmed that the engine sound in the RJ uses parameters from the flight model (N1, N2, etc). The actual thrust lever position isn't considered for the engine sound itself.
They do note, however, that upon increasing throttle from ground idle, there is an initial rumble to indicate an increase in fuel flow (combustion), which could be perceived as an increase in N1.
Mark - Just Flight
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Hi Mark,
Thank you for your reply and investigation. However, I’d urge you/your sound engineer to watch the video I linked again, and watch the Engine n1 gauges whilst listening to the audio. Something’s definitely not right… The audio is responding much too quickly when compared to the gauge reaction, which is what leads me to hypothesise that it’s “wired up” to the thrust lever position at the moment.
Solutioning aside, I’m sure you’ll agree it’s not correct in my video. Not sure if this is specific to my environment or if it’s a product wide bug?
Many thanks
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Our sound developer read this thread and watched the video prior to my previous response. As they said, the engine sounds are directly linked to the parameters outputted by the flight model. There may be a small delay between the flight model outputs and the indications on the PED, which is causing the behaviour you are reporting.
Mark - Just Flight
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The reason for this is that the engine response close to idle is instant, unrealistically so.
This can easily be verified watching any video from the real aircraft.
Yes the engines should respond quickly but not as quickly as it currently does at low RPMs.
