Falcon 50 N1 vs N2 Engine Indications

[tatfsn 2]

Hi fellow Falcon 50 pilots--

 

I've noted, from the first beta release of the FSW Falcon 50, that it isn't possible to spool up to over 91 or 92% N1 without exceeding

the red lines of the N2 indicators.   Obviously, trying to remain below the indicated N2 limits severely hobbles the aircraft's takeoff performance.

I like operating the Falcon into airports with relatively short runways (per the real world information that I've researched on the aircraft),

but in order to do so I always have to routinely bust the red line limits on the N2 indicators.

 

It's even more of a problem in that, in recently doing some additional trials, I was doing  takeoff from runway 31 at KDBQ, which is

all of 6500 feet long.   Gross weight was 36000 pounds, and my calculated Vr was 136 knots.   As an experiment I did the takeoff

in strict adherence to the limits on the N2 indicators, which limited me to about 92% N1.   From experience flying the bird, foregoing

that 7-8% of thrust makes a huge difference.   I ended up using nearly all of the runway, which is clearly unlike the ability of what actual

Falcon 50 jets can do (and what I've seen them do).    I've flown the Maddog X and both FSLabs and Aerosoft's version of the

Airbus A319/A320 and none of those aircraft have used anywhere near the same amount of runway.    I should add that the

ambient temperatures were the same on each of the trials that I did with these respective birds, and that in each case, they've

been derated thrust takeoffs. 

 

Is it normal to exceed the F50 engines' N2 limits on takeoff, in actual practice?    I haven't been able to find any info in that regard.

Any insight would be greatly helpful. 

[capceo 117]

Well, I haven't flown the DA50 in real life, but I do fly the Lear 35 for a living, which has basically the sameengines. Our aircraft are equipped with N1 DEEC's, which are primitive little computers that basically allow you to firewall the thrust levers and it will automatically limit thrust so that N1, N2, and ITT limits are never exceeded. When any of the three reach a limit, it stops the fuel computers from allowing the engine to spool any further.

Having said that, I've never actually seen a takeoff where the N1 even came close to 100%. The closest I think I've ever seen it was 96.X%, even when its really, really cold out. Flew the airplane the other night where it was 30F out, and our maximum available N1 was 94.6%. N2 reached its limit prior to N1 or ITT.

[tatfsn 2]

On ‎2‎/‎25‎/‎2019 at 6:22 PM, capceo said:

Well, I haven't flown the DA50 in real life, but I do fly the Lear 35 for a living, which has basically the sameengines. Our aircraft are equipped with N1 DEEC's, which are primitive little computers that basically allow you to firewall the thrust levers and it will automatically limit thrust so that N1, N2, and ITT limits are never exceeded. When any of the three reach a limit, it stops the fuel computers from allowing the engine to spool any further.

Having said that, I've never actually seen a takeoff where the N1 even came close to 100%. The closest I think I've ever seen it was 96.X%, even when its really, really cold out. Flew the airplane the other night where it was 30F out, and our maximum available N1 was 94.6%. N2 reached its limit prior to N1 or ITT. 

Thanks so much for the reply and the insight; it's especially helpful to hear from a guy who flies birds like this for real!

I once again learned some things I didn't know.   Guess I'll need to look at adjusting my loads depending upon the runways

that I intend to use.    

[dbw1 443]

On 2/25/2019 at 6:22 PM, capceo said:

Well, I haven't flown the DA50 in real life, but I do fly the Lear 35 for a living, which has basically the sameengines. Our aircraft are equipped with N1 DEEC's, which are primitive little computers that basically allow you to firewall the thrust levers and it will automatically limit thrust so that N1, N2, and ITT limits are never exceeded. When any of the three reach a limit, it stops the fuel computers from allowing the engine to spool any further.

Having said that, I've never actually seen a takeoff where the N1 even came close to 100%. The closest I think I've ever seen it was 96.X%, even when its really, really cold out. Flew the airplane the other night where it was 30F out, and our maximum available N1 was 94.6%. N2 reached its limit prior to N1 or ITT.

Just curious. Is there any way to over ride this if you ever had a need? I retired a few years ago after 40 years of flying and there were a handful of times being able to exceed a limet was handy.

[capceo 117]

Well in the Lear, the only way to override the limiters in place from the DEEC's is to turn off the fuel computers. This will eliminate N1, N2, and ITT limiting, as well as underspend and overspeed protection. It also significantly increases the spoolup time.

Edited March 4, 2019 by capceo

[JRBarrett 3,034]

On ‎2‎/‎27‎/‎2019 at 9:47 PM, dbw1 said:

Just curious. Is there any way to over ride this if you ever had a need? I retired a few years ago after 40 years of flying and there were a handful of times being able to exceed a limet was handy.

It's not permitted to take off with the engine computers switched off. If a computer fails on the ground, it is a "no fly" item. If it fails in flight, the aircraft can continue to its destination, but the crew has to exercise caution, as all overspeed protections are lost on the engine with the failed computer.

Some TFE-731 variants in certain aircraft have an "APR" (Automatic Power Reserve) system that permits exceeding the normal calculated N1 of the day, but it only comes into play if there has been an engine failure after V1

[Flysimware 647]