How does a jet engine spool up when starting in real life compared to Microsoft Flight Simulator?

N918KT

N918KT

Line Up and Wait
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Airline pilots, I have a question for you.

In real life, how does a jet engine spool up on an airliner when you start the engine, compared to starting a jet engine in Microsoft Flight Simulator?

In Flight Simulator, when you start the engine, the engine spools up slowly to say 5% or 10% N1 then suddenly roars to life, stabilizing at around 20% or 25% N1, if I remember correctly.

Is it like that in real life? Or does a jet engine spool up slowly and steady until it stabilizes at 25% N1?
 
Yup, roars to life because fuel has been introduced. Pretty much as you described, I can do the engine noise, well, I can ask @SixPapaCharlie to do the engine noise for you as it spools up if you want. I forget the exact numbers but that's basically it. Engine temp (ITT) is what we really watch for so it can be shut down if it heads for a hot start. Same for turboprops.
 
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Depends on the engine. The CRJ-7/900 take a life time longer then the 200. This is partly due to the fact the 7/900 engines are FADAC controlled. The 200 kinda just dumps fuel in and jumps to life unlike the 7/9 that slowly wakes up.

N1 rotation is only really important in the 200 before you throw fuel in. 7/9 you won't see N1 rotation until about 30/35% N2. Everything is based off %N2 and ITT in my plane

It's fun to watch a new guy start a 200 from behind. Sometimes you'll get a 20' ball of fire if he forgot to arm the ignition! The smart ones will abort the start but sometimes you'll get a good light show from a newbie.
 
That is one thing Microsoft did get wrong. Every turbine on the sim surges when it starts. The only thing that spikes like that in a real turbine is the ITT, but not the N1 or N2 as the sim does.
 
ARFlyer said:
It's fun to watch a new guy start a 200 from behind. Sometimes you'll get a 20' ball of fire if he forgot to arm the ignition! The smart ones will abort the start but sometimes you'll get a good light show from a newbie.
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Does that cause an exceedance and require the plane go in for maintenance?
 
MassPilot said:
Does that cause an exceedance and require the plane go in for maintenance?
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I don't think you want the honest answer to that question, industry wide. Certainly not in the case of some of the more razor-thin revenue margin FFD outfits. After all, there is a reason they're doing on the job training with paying passengers in the back.
 
it varies from engine to engine even on the same airframe. the cfm engines on he bus spool up quickly and smoothly. the IAE engines spool up in stages, it rises very slowly at first, the stagnates for a second when the ignition comes on the and then spools up faster. the IAE take forever to start compared to the cfm engines.

bob
 
midwestpa24 said:
That is one thing Microsoft did get wrong.
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It is one of MANY that Micros*it got wrong. Besides what you mentioned, there are many many others. Just a few to get you started. :)
- Starting a turboprop, propeller does not move with starter engaged and engine at a few percent N1.
- Adjusting prop RPM on a piston does not change engine sound. Adjusting MAP does. LOL Morons. Total morons. Those programmer kids have never seen an airplane before, let alone know how it works. :)
- OAT gauges are usually just painted on so you have no idea when to turn on de-icing. You need to wait for your engine to quit.
- Ldg gear indicator lights do not extinguish with master off. The glow nicely green.
Based on these, I would venture a guess that they did all their testing on the default 172. :)

LM did not fix anything useful after they bought FSX and re-released it as expensive P3D. They slowly started making small changes to the engine but no fixes to the blatant design flaws in airplane behavior.
Crossing fingers that they jump on that next and turn it into a useful simulator.

</rant>Sorry.
 
N918KT said:
Is it like that in real life? Or does a jet engine spool up slowly and steady until it stabilizes at 25% N1?
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Eight Kilo Tango, you have the whole Internet at your disposal, I think you'll love watching some YT videos of jet engine starts or turboprop starts too.
There are many good and famous pilots out there who post nice footage and they have engine starts too, with gauges and explanations. Very educational.
 
BigBadLou said:
It is one of MANY that Micros*it got wrong. Besides what you mentioned, there are many many others. Just a few to get you started. :)
- Starting a turboprop, propeller does not move with starter engaged and engine at a few percent N1.
- Adjusting prop RPM on a piston does not change engine sound. Adjusting MAP does. LOL Morons. Total morons. Those programmer kids have never seen an airplane before, let alone know how it works. :)
- OAT gauges are usually just painted on so you have no idea when to turn on de-icing. You need to wait for your engine to quit.
- Ldg gear indicator lights do not extinguish with master off. The glow nicely green.
Based on these, I would venture a guess that they did all their testing on the default 172. :)

LM did not fix anything useful after they bought FSX and re-released it as expensive P3D. They slowly started making small changes to the engine but no fixes to the blatant design flaws in airplane behavior.
Crossing fingers that they jump on that next and turn it into a useful simulator.

</rant>Sorry.
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The stock planes SUCK.. add on planes like the ones from A2A are a lot more realistic, probably the best you will get with a plastic yoke and rudder pedals with no feedback.
 
I agree with mikea76. The stock planes really suck and aren't good for making an assessment about the usefulness of the sim.
 
BigBadLou said:
It is one of MANY that Micros*it got wrong. Besides what you mentioned, there are many many others. Just a few to get you started.
- Starting a turboprop, propeller does not move with starter engaged and engine at a few percent N1.
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Not true for all turboprops.

Here's one:

Funny thing: That guy knows how to start the engine, but not how to close the sliding D.V. window.
 
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The basic principle of starting a turbine engine is simple. First ensure you have enough cooling, then introduce fuel. That is why you crank up the N1/Ng/whatever to a pre-set value (most PT6 engines for example are around 12-13%) before throwing in fuel. If you put in fuel too early, it will cause a hot start because the gas generator isn't turning fast enough (that is: not pushing enough air through the engine) to keep the combustion liner/turbine cool enough. The airflow is the main factor to cool down the engine internally. After the startup, the engine itself runs on a Brayton cycle so as long as you throw in fuel, the flame will burn.
 
BigBadLou said:
Adjusting prop RPM on a piston does not change engine sound. Adjusting MAP does. LOL Morons. Total morons. Those programmer kids have never seen an airplane before, let alone know how it works. :).
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Not sure I’d be giving those programmers so much **** if I were you.
 
jesse said:
Not sure I’d be giving those programmers so much **** if I were you.
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Elaborate please.
Since in real life, moving throttle in a complex aircraft with a CS prop does not change engine sound (RPM). Moving the blue lever changes RPM and hence also engine sound.
The FSX monkeys got it backwards. Why not give them sh*t? They portray the simulation in a very wrong way. Is calling them out on it too non-PC of me? Should I write them an apology letter? :)
 
Close my eyes and just let FADEC take care of everything...until it fails and you get “shock heating.” :D
 
BigBadLou said:
Should I write them an apology letter? :)
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No, but you might want to read what you actually wrote (as opposed to what you were intending to write). I'll copy it verbatim below:

BigBadLou said:
- Adjusting prop RPM on a piston does not change engine sound. Adjusting MAP does. LOL Morons. Total morons. Those programmer kids have never seen an airplane before, let alone know how it works. :)
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BigBadLou said:
It is one of MANY that Micros*it got wrong. Besides what you mentioned, there are many many others.

LOL Morons. Total morons. Those programmer kids have never seen an airplane before, let alone know how it works.
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Got it. It's a total POS compared to the one you wrote. Where can I get your flight sim again? o_O
 
If I go start the MU-2 this weekend I'll see if I can record the start.

It's not a jet, but it is a turbine. Concept is similar. But all turbine engines are a bit different because of differences in the design.

For most turbines which have two spools (high pressure which drives the compressor, and low pressure which drives the fan or propeller) you care about the core speed during start and watch the EGT/ITT go up and then go back down. On the MU-2 which has single shaft engines, you have more mass to accelerate. Where the core accelerates faster vs. slower depends, as does the rate the EGT/ITT goes up and back down. It's pretty hard to replicate that accurately for all engines.

For example, on a PT-6 you have only half the fuel nozzles injecting fuel during the beginning of the start, and then the other half start injecting fuel somewhere around... I want to say 30-35%. When that happens, the ITT rise accelerates significantly, so does the core speed acceleration. Battery condition matters, or if you're starting on ground power instead of the batteries. For most larger jets you've got an APU that provides bleed air to air starters on the main engines, which helps to make the starts more consistent on those.

As they say, do 100 good starts and you'll know what a bad start looks like.

It'd be nice to have more accuracy in engine starts, but I can forgive that to some degree. It'd be more doable to have some of the appropriate sound changes and simpler to put in calculations for that.
 
BigBadLou said:
You, sir, are one twisted individual.

I like that! :D
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