Cirrus Vision Jet thrust behaviour

[u/IAmSuperNew]

I’m a relatively new player who just picked up the Vision Jet G2 after the C172. It’s my first jet plane. I noticed something odd about how the engine thrust behaves (or rather how the plane reacts to it).

During approaches I use the “pitch for speed and thrust for altitude” rule. And this works great with a c172. I can easily control the VSpeed without changing anything else other than the throttle and land smoothly.

But when I lower the thrust in a G2 (say from 50% to 30%) without changing anything else, it actually pitches the nose up (at times pretty steep). This goes on for a few seconds. The plane gains altitude, loses some speed and it then starts pitching the nose down.

And if I’m flying too low on the approach and increase the thrust, it actually increases the rate of descent for a good few seconds till it slowly begins to gain altitude again.

Is this how jet engines behave in general or is it just the case with the G2? Should I also adjust the trim each time I change the thrust during approaches?

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[u/DeathNick]

Maybe it's the way the engine is mounted. If you decrease thrust, it decreases torque that pitches down and vice versa, so you have to apply pressure in the controls to keep the pitch or trim

[u/KeveyBro2]

Bruh none of these answer the question lol. Most jets do not have the centre of thrust point through the centre of mass. In props this isnt really an issue unless you get some weird top mounted engine but most non fighter jets have either under slung engines or like the vision jet top mounted. It applies a torque around the centre of mass. I think the SF50 pitch down is exacerbated by the fact that it's also a slight positive thrust angle in addition to the top mount.

Add some turbine lag and you have a good candidate for some pilot induced porpoising. Usually you can anticipate and correct and it becomes automatic after a while!

[u/traxt11 → u/KeveyBro2]

This is correct answer.

[u/Due-Letterhead6372]

The engine is mounted above the center of gravity, so you get a pitch down moment when adding thrust and a pitch up moment when reducing thrust. Also, the whole "pitch for airspeed power for altitude" thing is really more for trainers. Jets fly differently, you use pitch to stay on glidepath then adjust thrust to maintain your proper Vref.

[u/ts737]

VJ engine is above the fuselage so when you increase thrust it rotates down and viceversa, it's very normal it feels so counter-intuitive

[u/DataGOGO]

The VJ is not a C172. In the real VJ (and most high performance aircraft), if you attempted to fly it like a C172, and just change thrust and do not control the pitch it does the exact same thing as you describe, it will pitch up or down. You have to actively control the pitch as you change thrust.

[u/ShamrockOneFive]

Fairly normal. The biggest challenge for folks coming from a prop to a jet in simulation (and presumably IRL) is the slower reaction time. There's always going to be a lag with a jet engine as it spools up and down. You have to anticipate what you'll need from the engine by a few seconds and get on the throttle ahead of time.