FDE update 737NG

[Guest Mazurek]

Hi , since the new 737NGX is going to take a while to be relased I was wondering if you guys from PMDG could make a FDE update improving the climb performance , especially on the 800/900 version.I know that one or two guys did it on their own , but they were prevented to release here at avsim because PMDG would not alow any changes on the software. So , if you are not going to do it , at least let somebody else do it. That way we can make better use of the software in hand and stay "pacient" waiting the NGXFernando

[Balint 18]

Hi FernandoWhat's the problem with the FDE, especially with the climb performance? I haven't noticed any problems with it so far.Cheers,

[onurksn 1]

Hello FernandoCould you be more specific about the climb performance issue. What kind of problems are you experiencing?I can't say anything about the 747, but I've read in various posts that the 737's flight characteristics are pretty close to real. These include insights from actual 737NG pilots.As for climb performance I'm sure you are bearing in mind that load and fuel figures tend to affect this a lot. Finally the 900 is a big aircraft compared to the 600, so difference is expectable.That said, of course there is always room for improvement in any science. RegardsOnurLTBA

[Guest Mazurek]

Well is not a problem that I am experiencing , It

[onurksn 1]

Hmm,Fernando, I see your point. I've also seen flights in the U.S at 40000 feet for pretty short distances. Between FL200 and FL300 I'm able (depending on the winds) to obtain 2000FPM which seems fair enough. I've timed my climbs on numerous occasions and compared them to my real life experiences as a passenger. Generally it takes around 15 minutes before the seatbelt signs go off (for a cruise altitude of 33000 feet).As a fact climb rate is less above FL340. My only guess is that this could be something to do with the weather engine in FS9. This also effects performance as far as I know (air density, humidity and so forth). As you should have experienced yourself sudden wind changes within realtime weather in FS9 does effect this.Other than that, I'm curious about what PMDG has to say about this.RegardsOnurLTBA

[Mats_J 2]

Fernando,Without knowing anything about your winds or temperatures we can not tell you what you experience is right or wrong. This discussion has been brought up before and if I remember correctly the PMDG NG is behaving as the real one considering all influencing factors.As for the FMC I think (someone please correct me if I have it wrong) it calculates the enroute segment as a 10 min segment when determining the TOC and TOD. The PMDG NG does not have the option of selecting enroute segment length (and I do wonder if the pilots can select that in the real FMC. I have not seen any reference to this functionality in my manuals).During a short flight just now without weather from SBGL RWY 10 via MARIC1 and BOTOM to SBGR (200 nm) with the -800 at a GTOW approx 45 tons with derated CLB-1 I still managed to reach FL 370 on the calculated TOC. TOD was at that point 60 nm ahead for a direct descent to SBGR.So somethings going on with your flight. I would look at winds and temperatures aloft.For anyone interested I'll attach the -700 FPPM table for Short Trip Cruise Altitude:http://forums.avsim.net/user_files/184459.jpgHope it helps,

[Guest Mazurek]

Sir , the route in question was SBGR to SBGL , your rote it

[onurksn 1]

Hello Fernando,I find this topic very interesting, especially after Mats's reply.Now, could you please give further information on what type of weather scheme you use during your short hop.On a flight with a cruise altitude of 37000 feet you should begin your descent at around 125 nm (depending on the winds of course).Considering that distance to cruise altitude is roughly 70-75 nm, well than your observations are true. Again I must emphasize that weather has effect so if you get the chance please bring up the weather issue with real world pilots. BTW while making any comparisons, on what criteria did you do this and have these pilots you've encountered tried out a PMDG 738.I'm going to try your route this evening and I'll let you know how everything went.RegardsOnurLTBA

[Guest Mazurek]

I Use ActiveSky and online weather , and sometime I don

[Mats_J 2]

Fernando,There are so many things you're not considering. What engines do your pilot friends fly? The NG comes with a variety of engine sizes. My route was approximately 20-30 nm longer than direct. That will not explain the difference between FL300 and FL370. I used a derated thrust mode which means my climb was slower than can be achieved and I still had 60 nm between TOC and TOD. With unrated climb thrust I would have reached FL370 earlier (or climbed to a higher altitude). I was using FS9 with no weather meaning I flew in a standard atmosphere which is the only way to compare the FDE without any influences by temperature and winds. My gross take off weight was 45.500 kg which is almost empty and barely enough fuel to make it without any reserves. I'll try your route but after the test yesterday I am positive I will achieve FL370. Please provide us with the full details when you and 'everybody else' did experience this anomaly and maybe we can figure out what's going on. Hope it helps,

[Mats_J 2]

Fernando,Try this flight without any weather and you'll see that you'll get to FL370 or above. Online weather can give you false readings and if the OAT at high levels are way off you may experience difficulties reaching altitude. AS has been reported to give too high OAT values in some cirumstances.Hope it helps,

[Guest Mazurek]

Johansson , the problem is call FDE , the company my friends fly is call GOL and they use CFM56-7 engines. Your route is a longer route and you as well as I can make it to FL300 before leaving the TMA , the route i

[Mats_J 2]

Fernando,I do not use videos to verify the PMDG NG. I use Boeing Flight Planning and Performance manuals and Boeing Aircraft Specifications.TOC and the green arc use two different prediction methods. The green banana is simply predicting your level off distance based on current vertical speed. As you climb the vertical speed will decrease. The TOC is estimated taking into account entered weather and aircraft performance specs. They are most likely not going to match in climb. The FMC will continously update the TOC postition based on input from sensors while in flight thus moving the TOC as flight progresses.The CFM56-7 is rated with takeoff thrust from 18,500 to 27,300 lbf (82 kN to 121 kN). It's probably either the B24, B26 or the B27 type. Depending on type it will make a difference on performance. I can't recall from the top of my head the engine type for the PMDG -800. It may be the B24.I'll report back after trying your route tonight.

[Guest Mazurek]

And as a Performance Manual reader , you have never saw anything different? For you the aircraft FDE is perfect? The green line and TOC dot will have to match at some point sir. If you don

[onurksn 1]

Gentlemen,Ok, I've done a test flight. Here are my results:I kept my aircraft a little heavy for a harsh test :GW: 130 lbsFuel: 11.9 lbsZFW: 117.7 lbsFuel reserves: 1.8Weather is FS9 default.Fernando, I followed your route, your SID and STARS and the total distance was 185nm, a bit shorter than your's.As you can see from the figures I tried to push everything further for more challenge.I conducted a 141 knot V2 take off from RWY 09L at SBGR, maintained runway heading until turning to SJC VOR and continued my climb to Peres. All the way above 3000 feet I had a slight tail wind (25knots) to make things more difficult. I used Auto climb thrust. (BTW Mats, PMDG 737-800 is 26N) My climb speed was 250/0.65mach and I was able to maintain 3000fpm up to FL200, 2500fpm up to FL300 and 1500fpm up to FL370. So yes, I was able to climb to FL370 by Peres. With a slower speed I could have climbed at a higher rate.I must note that as I entered the given route, my FMC gave me a "unable CRZ altitude" warning. Therefore I did things manually with pitch mode LVL CHG.As soon as I reached my CRZ altitude I had to start my descent, and a pretty fast one too. The magenta was way below by that time.On the Jeppesen charts I noticed 2 holding points, one at Mango and another one at Tubo. I didn't need to hold since I wasn't respecting speed restrictions. Note that these 2 holding points will make the overall distance longer.At 3000 feet I flew over the NOA NDB and banked slightly right to intercept RWY 15 for landing. Everything went well, but I did have to use extra drag to slow down (In this case speedbrakes between 10000 and 5000 feet).My conclusion is the following:- The PMDG is capable of climbing to that altitude. However in real life it would be absurd to do it my way (start descent just after leveling off).- Having a little knowledge about flights in Europe it seems to be rare for a 738 to CRZ at FL370 for 200nm. I don't recall having heard about it. But maybe this could be otherwise in Brazil.- Again and again I believe that weather is an important factor. If I had had a headwind I could have reached CRZ altitude before Peres due to a slower ground speed.- I must also state that I'm not an expert aviator, I'm just a modest flightsimmer who has a lot of hours on PMDG 737's since I don't fly anything else (Because it's by far the best modeled short-medium haul add on). I do check out cockpit videos but I'm not going to base anything on them because I'll be unaware of a lot of factors concerning these flights.- As Mats has said, different engines and N1 rates can make differences. So it would be unwise to say anything without knowing every key factor.So guys, I really don't have an answer, I'm pretty much convinced that our aircraft is not underpowered compared to it's real life counterpart. That said Fernando, by no means I doubt your statements. But as Mats said if the model is based on official Boeing information I'll be more than convinced since I also know that PMDG should have conducted tests with a real 737. Maybe due to FS9 restrictions (If there are any concerning this issue) certain things could have been "eased".I cannot comment on how perfect FDE is, but I'm sure it's pretty good hence the succes.I will keep on testing on this particular route and I'll let you know if I find out anything different.Thanks for your input and best regardsOnurLTBA