Embraer 175/195 Ejets V2 - how do I get 100% n1 thrust for takeoff?

[UnstableNuclearHedgehog]

Hi all! Recently purchased the Ejets V2 through steam. Loving them so far, except for one thing...

I like to do real-world flights as much as possible. My latest one i'm enjoying is London City airport to Dublin (EGLC to EIDW). 

EGLC has a VERY short runway, and requires steep climbout after takeoff (at one end is water and the other high buildings). Because of this I want to be using maximum takeoff thrust - 100% N1.

No matter what I do, I CANNOT get the aircraft to give me 100% N1. Even with the autothrottle off the it still limits me to the T/O setting in the MCDU! I even tried fiddling with the FLEX settings to increase it, but the most I can get is 95.1% N1.

Can anyone tell me how I get the aircraft to allow me to get the 100% takeoff thrust I really need at this airport?

Edited August 14, 2017 by UnstableNuclearHedgehog

[UnstableNuclearHedgehog]

Bump...

So can anyone tell me how I can get maximum thrust from the engines? There's got to be a way!

[Emiflyer]

Hi there.

Although the Ejets Embraer is fun to fly, there are many things that are not simulated realistically/correctly. So as long as simple autopilot/Lnav/Vnav/etc behavior is not updated, I think it is too much to ask for realistic N1 values in the Ejets.

But to answer your question:

In the real world:

The required TO thrust for a specific runway is calculated depending on ambient conditions (temperature/wind/etc), aircraft weight, runway length and obstacles in the area. The interesting part about the required performance calculation is that with the calculated FLEX setting (which results in a certain N1 setting) it must be possible to lift off and clear obstacles even if one engine fails at V1!

So knowing this you should not have a problem taking off from London City with 95%N1 in FSX as long as you do not have an engine failure :-)

In FSX:

I have not tried London City in FSX but you can use Flaps1,2,3 or 4 for take off. Just experiment until you find a flaps setting that lets you lift off quick enough while not reducing climb performance too much (In FSX you can experiment...in the real world not).

 

As far as 100% N1 concerns:

100% N1 is the absolute rotational limit the rotors should spin at (to prevent damage). But there are other engine limits like temperature and max rated thrust (which is the max power (for example 18.500LBS) the engine can produce without causing damage). Depending on ambient temperatures , 100% N1 rotational speed could give more than max rated thrust (on a cold day) and thus N1 must be reduced to 99-98-or maybe even 95% N1 to keep the produced thrust within limits.

I don't know at what temperature you are taking off and I don't know what kind of logic Feelthere has programmed into the TO N1 calculation. So I cant say if those 95% you are seeing are in fact the max N1 for the real world engine under the same conditions or not.

To get max thrust, first of all, use TO1 in the MCDU (not TO2 or TO3). TO2 and TO3 are called "derate" and basically tell the engine to reduce its maximum output (even at full throttle) to extend engine life. Second, try toggeling FLEX OFF at TO1. And third, you can try increasing the outside air temperature in FSX and setting this temperature also under MCDU/TO Dataset/TO temp. See if increased temperatures will give you more N1 (but do understand that you could be having the same amount of maximum thrust (18.500LBS for example), just at a slightly higher N1 (96 or 97% or whatever).

 

Last but not least, page 59 of the Ejest manual mentions that your joystick or thrust levers must be full forward for the simulation to achieve its full thrust.

 

Hope this helps.

 

Ps if I find the time then I will try and see if I can 100% N1

[UnstableNuclearHedgehog]

Hi,

Thanks for your reply.

I am aware of the sort of factors that affect engine thrust, and that the MCDU function is not 100% correctly modelled. The reason I want 100% N1 or as close to as possible is because of how short the runway at London City really is! And the air temperature is currently around 18C there, so I should be able to get close to 100%, as AFAIK maximum thrust is calculated at 15C and ought to equal 100% N1 at that point. At the moment, using Flaps 4 I can takeoff pretty smartly, but I'm still not sure V1 comes soon enough to stop in time. This is particularly unappealing when taking off on runway 09 which is bordered by the river thames. (I suppose I ought to test it really!)

I will do some more fiddling with settings and see what I come up with!

[Emiflyer]

I ran some real world E195 software.

At 18C and 1013 QNH, no wind, the E195 with 18.500LBS of thrust can take off from:

Runway 09 with max 39.670Kg, Flaps 4, TO1 no FLEX, stop margin 0 Mtr and results in 90.86% N1

V1 110kt, Vr 115kt and V2 122kt

 

Runway 27 with max 39.900Kg, Flaps 4, TO1 no FLEX, stop margin 1 Mtr and results in also 90.86% N1

V1 110kt, VR 115kt and V2 123kt

 

So in either case max thrust is achieved at 90.86% N1....it can not/is not allowed to do more than that.

 

In both cases a real life aborted take off at V1 is a very close call and it sure would not look like you could make it due to the non existant stop margin....but you could make it ;-)

You can also throw away your brakes after that and call the fire department :-)

 

 

[UnstableNuclearHedgehog]

1 hour ago, Emiflyer said:

I ran some real world E195 software.

At 18C and 1013 QNH, no wind, the E195 with 18.500LBS of thrust can take off from:

Runway 09 with max 39.670Kg, Flaps 4, TO1 no FLEX, stop margin 0 Mtr and results in 90.86% N1

V1 110kt, Vr 115kt and V2 122kt

 

Runway 27 with max 39.900Kg, Flaps 4, TO1 no FLEX, stop margin 1 Mtr and results in also 90.86% N1

V1 110kt, VR 115kt and V2 123kt

 

So in either case max thrust is achieved at 90.86% N1....it can not/is not allowed to do more than that.

 

In both cases a real life aborted take off at V1 is a very close call and it sure would not look like you could make it due to the non existant stop margin....but you could make it ;-)

You can also throw away your brakes after that and call the fire department :-)

 

 

Wow! Thats very interesting, thanks!

My own investigation of the aircraft in sim reveals the TO-1 setting shows as 17000 lbs thrust (annotated on the MCDU as 17K0). 

I set the aircraft up for a real world flight, London City to Dublin. This gave a ZFW of 36164 kg and a GW of 40192. So slightly above what you've got in your calculations. Maybe I'm a little generous with the reserve fuel, as this only represents 50 pax and 30% cargo in the load manager! Flaps 4, V1 was 113, VR 116 and V2 122.

OAT 15C, QNH 1013. I adjusted the takeoff temp in the MCDU to 30C. This allows 95.1% N1. 

On RWY 09, rejecting takeoff immediately before V1 and applying full reverse thrust allowed me to stop with maybe 15m to spare. The same relying solely on the brakes saw me take a dip in the thames! I didn't have time to test RWY 27 tonight. 

Think I need to lower my takeoff weights - hand luggage only, people! And no fatties! 

Edited August 18, 2017 by UnstableNuclearHedgehog
Spelling and other errors

[Emiflyer]

haha, yep pretty critical flight.

You are correct, the Ejets seem to have different engines but pretty cool that you are getting those realistic speeds and performance out of FSX....I am impressed that the aircraft stopped with 15mtrs to spare....that is really good for a simulation!

By the way, for a take off that is this critical, you should set take of thrust with brakes set and then let go of the brakes (no rolling take off). Recalculating with that I can actually take off with 41.540Kg from R09 and 41.300Kg from R27 (with slightly higher Vspeeds)

[UnstableNuclearHedgehog]

1 hour ago, Emiflyer said:

haha, yep pretty critical flight.

You are correct, the Ejets seem to have different engines but pretty cool that you are getting those realistic speeds and performance out of FSX....I am impressed that the aircraft stopped with 15mtrs to spare....that is really good for a simulation!

By the way, for a take off that is this critical, you should set take of thrust with brakes set and then let go of the brakes (no rolling take off). Recalculating with that I can actually take off with 41.540Kg from R09 and 41.300Kg from R27 (with slightly higher Vspeeds)

Thats the technique I used, and without reverse thrust I couldn't stop in time. Although the sim doesn't model ground friction properly, and you start to move slowly a couple of seconds before you reach maximum thrust even with the brakes on. Which doesn't help!