how to tell when an air breathing engine will choke?

[chaoko99]

^ pretty much self explanitory

[GDJ]

On my Jets it will start to yaw either left or right slightly just before the engines sneeze out. Usually that gives me a second or two warning.

Other than that, when my intakes start getting past the 15% air charge I start backing off the throttle.

[Murph]

The best way is to be Chuck Yaeger, borrow some gum from your best mate, jump in, and push it to the limit and slightly beyond. That way you learn fairly exactly where the safe limit is. It varies for every plane, and how you fly the plane (intakes are air speed sensitive). You get early warning signs from the intake air resource, and you can watch the right-click panel on the intakes and engines for clues as well.

When not doing crazy test pilot stuff, you don't have to push it to the very limit. Switching to rockets for space, or going to straight and level cruise for SR-71 flight is best done a little bit below the absolute max limit, without really losing all that much, but gaining certainty and ease of flight. Switching to rockets 1000m or 2000m below the abs max is not going to cost you all that much rocket fuel, and might even save fuel overall, as squeezing that last bit of jet performance out can be quite fuel intensive.

[numerobis]

Right-click on the intake, see the airflow. Right-click on the engine, see the fuel flow. Make sure 15/16 times the fuel flow is a smaller number than what the intake provides. Fuel flow doesn't change nearly as fast as intake air flow, so mostly you just watch the intake airflow.

With turbojets, one intake get you to as high as 21 km at high speed and full throttle. Two intakes at high speed you can reach 25km; throttle back to 1/3 throttle and you can climb another 5km. RAPIER can go higher because its fuel flow is lower -- because its thrust is lower.

[MKI]

On my Jets it will start to yaw either left or right slightly just before the engines sneeze out. Usually that gives me a second or two warning.

Other than that, when my intakes start getting past the 15% air charge I start backing off the throttle.

^this

Even the new RAPIER engine will sometimes give this effect, which is why i keep the "switch mode" toggle on a command group.

I personally push my air intake levels to .## and the number is how many intakes i have. More intakes = more engines, so more demand for air and probably more thrust to spin out.

[JiWint]

Watch the intake air.It's actually to turn off air engines way before it,because the less intake air,less thrust engines give

[Murph]

Watch the intake air.It's actually to turn off air engines way before it,because the less intake air,less thrust engines give

Turning them off way before it runs out isn't necessarily fuel-optimal. As the air runs out, so does the atmospheric drag, so the loss of thrust isn't always a major issue. Since jets are hugely more fuel-efficient than rockets, cutting them out too early is very bad for fuel efficiency and therefore your payload delivery capability. I think it's generally best to stay on jets until the combined rate of altitude and speed gain has slowed down significantly.

[jsfalconero]

The flameout threshold for the turbojet engines is roughly 0.01 intake air per engine. If you click on the resources indicator during flight you can watch the intake air drop toward that point. Of course, intake air is also a function of speed/altitude. Generally I allow myself a safety margin of around 0.02 when I'm at my jet service ceiling.

Another trick if you have 4 or more jets (generally not a good idea, but sometimes necessary) is to toggle one set of jets off on the same action group as your rocket engine -you can sometimes gain a bit more jet they thrust that way before you need to kill the second set of engines and close your intakes. You'll need the rocket engine(s) firing though, as usually one pair of jets won't be enough to keep your TWR high enough to offset drag.

[Anton P. Nym]

One way I tell is a change in the engine sound, it sounds a bit thinner just before it stalls out. That's my cue to throttle back or to switch to the rockets.

-- Steve

[ArmchairGravy]

One way I tell is a change in the engine sound, it sounds a bit thinner just before it stalls out. That's my cue to throttle back or to switch to the rockets.

-- Steve

Yup, when you hear them scream, they're about to go.

[chaoko99]

how to set as answered?

Edit: because I found out my self (when intake flow approaches 0)

Edited December 22, 2013 by chaoko99

[arq]

Watch the intake air.It's actually to turn off air engines way before it,because the less intake air,less thrust engines give

This is actually untrue. What actually happens is turbojets have 50% thrust and 0m/s, 100% at 1km/s, 50% at 2km/2, and then drops off to 0% at 2.4km/s. RAPIERS are the same except that they fall to 0% at 2.2km/s. So what you are actually seeing is thrust decreasing with increasing velocity rather than decreasing air intake.