Quote from Hangar45 Admin on December 14, 2017, 8:35 am

(Original thread started on 12-30-13 by Jaap)

I was wondering if anyone has the same idiotic climb rate when activating Level change as I do. Flying level at for instance 7000ft 250Kts I set the altitude to say 20000ft and press FLC.

 

Throttle goes up immediately and aircraft starts to climb. I keep speed set at 250Kts but it still accelerates to about 280-290 Kts and keeps climbing faster and faster to a climb rate of over 6000 ft/min. This is not normal is it?

 

I checked the .air file with Airwrench and there it says to have a standard climb rate of around 15000 ft/min. I dare not change it, cause as soon as I activate the edit button all kinds of settings change from green to red. I use the .air file provided by Per Alm by the way, which gives me overall good results, except for the climb rate that is. I also tried it with the default .air file which gives the same crazy climb rates. Did anyone ever notice this, and is there maybe a solution (as in a better .air file or something?)

 

(Posted by Eric Tomlin on 12-31-13)

Are you using Project Magenta? I ask because I know of no software that has a FLC for the LJ45.

 

(Posted by Jaap on 12-31-13)

Yes, that's correct. Actually in PM it is called LVL CHG. But I have mapped that button to my Lear MCP where it is called FLC. I gather by your question that you think maybe PM is the culprit? Probably the Jet45 software does not give these problems? But what about the .air file then? If I compare airfiles with Airwrench to a Boeing or CRJ700, the values I find in the Max Climb rate seem fairly normal. At least not 15000 ft/min

 

(Posted by Eric Williams on 12-31-13)

I can only vouch for using standard FSX and autopilot controls. On my setup when I engage the ALT autopilot control, it follows the vertical speed exactly as I have selected.

 

(Posted by Jaap on 01-02-14)

When (with active Autopilot) I select an altitude and a vertical speed, my Lear follows that without problems too. But as soon as I select an altitude and press FLC it goes wrong. I have totally removed the FSX panel and I don't remember the FLC button being present in the on screen panel. Is it there? And if so, could someone maybe test what happens when you press it?

 

I have the distinct impression that MS never really finished the .air file of the Learjet. For as far as I can understand the values in the air file, there are some things that just don't add up. I have been trying a couple things with editing the original air file, but whenever I think to have one thing right, another thing went bad.

 

When I enter all the data of the real Aircraft (for as far as possible) in the air file, it is hardly flyable anymore, very strange. I take it you use the Jet45 software, is the FGC ( I take it that's what it is called in the Lear instead of MCP) completely handled with that? Also the switching from left to right FD? I'm struggling with that too. Currently I'm checking if that is possible with FSUIPC advanced options, or maybe with a LUA.

 

(Posted by Randy Buchanan on 01-03-14)

One thing, that I am surprised nobody mentioned is that the Lear45 does not have autothrottle. So your comment, "The Throttle goes up immediately and aircraft starts to climb" could have raised a question. In FSX you can use that air speed function on the autopilot panel but in the real airplane the throttle does not move on its own. If your Lear45 climbs at 15,000 a minute it is not a Lear45, more like a F15.

 

The published rate of climb is 2,800 but our sims will go to I want to say 5 to 6 thousand feet per minute. It make me wonder what the power on stall rate is. We could test it and get back to you. Here is part of what the manual says "Depressing the FLC button once engages the normal climb/descent profile on both PFDs. Depressing it a second time selects the high speed climb/descent schedule. A third depression deselects the mode. The FD chooses between the climb and descent schedule based upon the airplane’s present altitude and the pre-selected target altitude. And the normal target rate of climb is 1500 feet per minuet so maybe the 15,000 rate is a typo.

 

(Posted by Jaap on 01-03-14)

Thanks for your answer, and you're correct: The Lear45 has no Autothrottle. Something we did not know when we started our build ( And I still don't know much about the FADEC etc., so sorry if I'm totally off track..). Nice to know though that the one Button actually has three functions.

 

Anyhow, it would seem to me that in order to keep a desired speed the aircraft needs to add power when a higher altitude is set and FLC is pressed. In our pit, the throttle handles move, in the real pit you would probably hear it by engine sound and see it on the engine displays. Undoubtedly there are more differences but this is how I see it now. You also mention "the normal climb descent schedule". What might that be at normal climb rate? 1500ft/min? And at high 2800 ft/min? I wish my plane did that.

 

What puzzles me by the way is that no one here has mentioned in so many words that his sim obeys these rates when FLC is used. And 15000 was not a typo I'm afraid. The attached image is the first page of Airwrench with a standard FSX lear.air file:

 

I hope you can see it, but at about half the picture on the left side you see: Target Climb Rate (FPM) 14212.8 and Max Climb rate 14213. Add to that the target/optimum climb speeds of 397.1 Kts and you must agree that this are hardly realistic figures for a non military A/C.

 

So what I am interested in is if anyone can take a look at the standard on screen Panel, see if FLC is there and if yes, start a flight, set an altitude that is at least 5000 ft. higher than you're flying at that moment, press FLC and see what happens. If it does work for you with normal rates, the problem must be in my PM software somewhere. If it does not, then clearly the air file is bad. I have tried altering the air file, but this is not easy to do. Almost every value you change has other (mostly undesirable) results. I'm curious to see your reactions!

 

(Posted by Eric Tomlin on 01-03-14)

There's several things going on here which is why I did not reply more than just guessing that Project Magenta was being used. I will try to be as logical as possible to address the original issue as well as some that have been added to the conversation.

 

1) The default LJ45 has no Level Change function. Therefore, you must use an autopilot (external) that does. This is what let me onto Project Magenta, as the PMRJ suite does have a Boeing-style MCP available, which is turn offers the Level Change function. I also knew that JET45 does not currently have a released FGC software, so this was all be process of elimination.

 

2) The LJ45 is a high performance aircraft both in the RW and FS. The aircraft can certainly climb at 6000' per minute if loaded lightly. It would be uncomfortable for the folks in the back, but yes, it can be done. In fact, per the Honeywell P1000 User Guide:

 

"Vertical Speed Digital Display – A digital display of the actual VS value is located in a box, on the zero reference line. This data is a magnification of the digits on the scale and is readable to a 50 fpm resolution. The digits are white. The maximum value is 9900 fpm.  For values between ±500 fpm, the digital display is removed. At values beyond ±500 fpm, the digital value of vertical speed is displayed."

 

Furthermore, from the Flight Safety Training Manual-

"VS (Vertical Speed) Depressing the VS button engages the vertical speed hold mode on both FDs. The FD commands pitch changes to hold the vertical speed that existed at the time of engagement. Once engaged, the vertical speed bug positions on the inner side of the vertical speed scale and a digital readout appears above the vertical speed indicator (Figure 16-34). The maximum selectable vertical speed is + 6,000 fpm."

 

As such, I cannot vouch for the info in the air wrench file (15000 ft/min). There's no telling where that entry came from and I cannot fathom the airplane being capable of climbing that fast under any circumstances.

 

3) Your original issue of  "Flying level at for instance 7000ft 250Kts I set the altitude to say 20000ft and press FLC.

 

Throttle goes up immediately and aircraft starts to climb. I keep speed set at 250Kts but it still accelerates to about 280-290 Kts and keeps climbing faster and faster to a climbrate of over 6000 ft/min. " is something that likely represents some sort of incompatibility or poor tuning between the aircraft's FDE and Project Magenta's MCP software. I wish I could offer more, but I do not have experience with it.

 

4) Per Randy, "The published rate of climb is 2,800 but our sims will go to I want to say 5 to 6 thousand feet per minuet."

I would like to see where this is published, because I cannot find reference to this in any of my LJ45 materials. I understand that published figures and possible figures are totally different sometimes, but I cannot fathom that Bombardier would publish such a low climb rate for this aircraft.

 

As for published Flight Level Change information, it is not given in Feet Per Minute, it's given in IAS or Mach, as seen here-

"FLC (Flight Level Change) Button – Pushing the FLC button commands the system to maintain a predetermined airspeed profile as the aircraft climbs or descends to a selected altitude target. The speed targets are:

- NORMAL PROFILE FLC

- Climb 250 KIAS to 0.70 Mi

- Descend 0.76 Mi to 300 KIAS, to 250 KIAS at 10,000 ft. and below.

- HIGH SPEED PROFILE FLC

- Climb 250 KIAS to 10,000 ft., then 275 KIAS to 0.73 Mi

- Descend 0.79 Mi to 320 KIAS, to 250 KIAS at 10,000 ft. and below.

- The toggle sequence is as follows:

- Normal (FLC) – High Speed (FLCH) – OFF

 

NOTE: A speed target cannot be set with the GC SPD knob when FLC is selected."

 

At the end of the day, I wish we could help you with your issue. That is the great thing about having a forum where at the very least you have a place that you can come to in order to either get some help, or in this case, at least express disappointment and frustration and not feel alone!

 

(Posted by Jaap on 01-03-14)

Thanks for your clarification. So the real Lear [i]is[/i] capable of doing 6000 ft/min, Interesting. Then for that part, the FSX one is accurate. Now to find a way to limit this in my software to 2800 max. Randy is right about the published 2800 ft (MTOW), I found it at my customer CD, see [url=http://members.ziggo.nl/jaap_both/Jaap/Learjet%2045%20Operational%20Analysis%202005.doc]HERE[/url] , page 3, but the 1500 he mentions I can't find either. For the XR it's even lower: 2630 ft/min (MTOW).

 

But there is still a lot wrong with the air file too. I'll keep experimenting with it.

 

Good to know that the FSX Lear panel has no FLC button, that saves me tracking it down from somewhere on my CD's. Sadly this gives me no outcome about where to look: air file or PM files. I tried to limit the climb rates through PM MCP.ini files, but somehow it keeps overwriting the values I set. Since I am a Private customer I don't expect PM to be very helpful with this.

 

But all of this is not a disappointment, it's more like a challenge to get it done anyway! I also thought it wasn't possible to handle both SPD and VSPD with one Rotary, but hey, it is. If I find something worth mentioning on this I'll let you all know!

 

(Posted by Randy Buchanan on 01-04-14)

I agree with you on this statement: but I cannot fathom that Bombardier would publish such a low climb rate for this aircraft. But here is the ad from Bombardier where it appears:

This document can be found HERE

 

So in this ad we see our plane will climb from any takeoff to 43,000 feet in 24 minutes and 36 seconds. What can I say do the math and it turns out to be 1755 feet per minute and this is a real average and you know airplanes climb slower the higher they go, so this becomes a great number I guess.

 

(Posted by Eric Williams on 01-04-14)

When the climb to cruise stats are posted- this is a VERY general statement so customers know what to expect and gives some bragging rights. As Eric T spelled out earlier- there are vastly changing variables for each phase of flight, loading, etc. The possible climb rate will change drastically according to many variables such as cargo weight, fuel weight, temp, altitude etc etc.

 

Overall it's pretty safe to say that the Lear is quite capable of performing similar to a fighter jet if lightly loaded. The power to weight ratio is really very impressive and probably one of the reasons many of us grew to love this aircraft.

 

Jaap- I hope you get your problems sorted out. I can vouch for the stock FSX airfile working fairly well with the standard autopilot controls. Admittedly I do use the "fake FSX autothrottle" very often when using autopilot. I also routinely use a quite aggressive climb rate (depending on ATC). From what I have gathered from Lear pilot articles- it is most often flown in real life at basically wide open or nothing.

 

One item that annoys me tho- the stock config is extremely sensitive to fuel and passenger loading. It has a real tendency to pitch up like crazy after takeoff if the loading isn't just right.