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svfranchini

737-700 Minor Bugs

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Some little details/bugs I have noticed when flying this bird:

 

1.- Trim settings are too low for T/O. Ex: FMC value gives a T/O trim of 4.5, when the aircraft really needs more than 5.0 or 5.5. This is not happening with other versions.

2.- Extremely hard rate of descent & pitch down (4000 feet per min or more & 5° or 6° nose down). Inclusive with max load.

3.- Left Retractable Landing Light contour textures flashing (day and night)

 

Probably these Items could be fixed in SP2.

 

 

Thanks

 

 

Santiago

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1.- Trim settings are too low for T/O. Ex: FMC value gives a T/O trim of 4.5, when the aircraft really needs more than 5.0 or 5.5. This is not happening with other versions.

 

Can you provide a little more hard evidence as to why it "needs" said trim? Are you using Boeing CG/Trim tables, or are you just assuming?

 

 

 


2.- Extremely hard rate of descent & pitch down (4000 feet per min or more & 5° or 6° nose down). Inclusive with max load.

 

That's not a normal behavior. My guess is that something is misconfigured on your system. See below.

 

 

 


3.- Left Retractable Landing Light contour textures flashing (day and night)

 

This is not a normal behavior, and this looks fine on my system. This is the first time I've heard of this, actually. Are you at an add-on airport? Are you using DX10 preview or other texture mods?

 

 

 


Probably these Items could be fixed in SP2.

 

Honestly, it sounds more like something on your system. What you're explaining sounds a lot like when people configure a flaps axis in FSUIPC, which can cause issues with the NGX. Do you have a flaps axis configured through FSUIPC?

 

In the future, it's usually best not to call things bugs until they're worked through and verified as bugs.

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Thanks Kyle for answering.

 

1.- If you use the FMS T/O page trim value as I do with other versions, it seems that the -700 nedds more trimming settings after airbone. Try to put that value for T/O and you will see what  I´m talking about. Porbably the FMS values on the -700 is not correctly modeled.

 

2.- 3.- No. I´m not using DX10 preview or other texture mods. No  FSUIPC module is installed. the problem is only with the -700.

 

Someone else has these problems?

 

Santiago

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Someone else has these problems?

 

I've been flying the 700 since the day it came out and I haven't seen these problems. If these were actual bugs, I'm relatively sure they would've shown up on the forum well before now.

 

You might want to submit a ticket to support.precisionmanuals.com to see what some of our support techs have to say.

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Some little details/bugs I have noticed when flying this bird:

 

1.- Trim settings are too low for T/O. Ex: FMC value gives a T/O trim of 4.5, when the aircraft really needs more than 5.0 or 5.5. This is not happening with other versions.

2.- Extremely hard rate of descent & pitch down (4000 feet per min or more & 5° or 6° nose down). Inclusive with max load.

3.- Left Retractable Landing Light contour textures flashing (day and night)

 

Probably these Items could be fixed in SP2.

 

 

Thanks

 

 

Santiago

I've been fly'n the '700' for a couple of months with 100+ landings (almost all at MGLW)and haven't had any problems with it. The '700' is by far the best of the bunch. It's kind of the sweet spot for the PMDG B737. Some of the airports I use are MHTG, MGGT, SKBO, SEQM, SPZO, SLLP, SLCB, SLSU, PAYA, PAEN, PAJN, PAKT and KJAC.

 

I use the FMC trim settings and have not experienced any trim problems. I do load the fuel/cargo/passenger using the FMC.

 

Billy Bluestar

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Billy,

 

Once airbone, try to put the yoke to Neutral position. Do not apply elevators  nose-up. You wil experience a nose down behavior. Try with -600 & -800 series it works fine.

 

Santiago

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Hi,

"Can you provide a little more hard evidence as to why it "needs" said trim? Are you using Boeing CG/Trim tables, or are you just assuming?"

I agree with Kyle...and I add: are you a real world B737-700 pilot to be so sure that what you're noted are bugs?

Which is your real world B737-700 experience to be sure about what you're talking about?

If thousand of costumers haven't noticed those "bugs" and you've and you're not a real pilot i think (not criticism here but I think that before defining "a bug" you need yo have strong evidence about it i.e. as Kyle has outlined by reference to FCOM values, real experiences etc. etc.), is highly probable you've a problem in your controls settings...

Tell us and we could help you (I hope)

Best Regards

 

Andrea Buono

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Billy,

 

Once airbone, try to put the yoke to Neutral position. Do not apply elevators  nose-up. You wil experience a nose down behavior. Try with -600 & -800 series it works fine.

 

Santiago

Santiago it sounds like you may not be trimming the aircraft's elevator correctly. When I fly an aircraft (sim/real world) I am constantly trimming the elevator to where there is no pressure on the yoke. By this I mean in any phase of flight I can let go of the yoke and the deck angle will not change. I have found the -700 to be the same as the other PMDG B737 variants. Even back in the early '70 when I was flying C-47/R4-Ds I was constantly trimming the elevator. The C-47 was so sensitive that I could feel the CE walking from one end of the aircraft to the other. :-)

 

To answer your question I flew one leg in the -700 with it trimmed correctly and the nose did not drop.

 

Billy Bluestar

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Never have noticed those issues here. And the takeoff trim will vary a good bit depending on

pax, cargo weights. I've seen some takeoff trim settings below 5, but I see just as many above 5.

Never have noticed any problems after takeoff using any of the various settings, and never have

noticed any hard pitch down behavior. Never have seen the retrac light issue you describe.

I flew the 700 today with a fairly light load, "BBJ rig", and if I remember right, the takeoff trim was

about 5.6. It varies with every flight, so I wouldn't really consider a trim setting below 5 as "wrong"

unless a real worlder claimed to never see a trim set that low with a similar load and balance.

And below 5 is still well in the "green" area as I recall.

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Santiago it sounds like you may not be trimming the aircraft's elevator correctly. When I fly an aircraft (sim/real world) I am constantly trimming the elevator to where there is no pressure on the yoke. By this I mean in any phase of flight I can let go of the yoke and the deck angle will not change. I have found the -700 to be the same as the other PMDG B737 variants. Even back in the early '70 when I was flying C-47/R4-Ds I was constantly trimming the elevator. The C-47 was so sensitive that I could feel the CE walking from one end of the aircraft to the other. :-)

 

To answer your question I flew one leg in the -700 with it trimmed correctly and the nose did not drop.

 

Billy Bluestar

What Santiago is referring to is that the aircraft should be roughly in trim after takeoff at V2+10. It's not that he isn't trimming properly, he feels the recommended trim position is too much nose down.

 

I tried a flight in the -700 yesterday. At 48.6 tonnes ZFW and 10 tones of fuel it gave me a stab position of 5.06 units. After takeoff it was a tad nose down but not excessively so.

 

It could be he's found a configuration that's more out of trim than usual and the aircraft may be the same in this config. Boeing don't test every possible CG and weight combination. Or it may be an error in the FMC takeoff trim calculation. Either way, it's up to the pilot to fly the plane and adjust trim accordingly. The takeoff trim setting is a starting point only.

 

It would be interesting to know what weight and CG he is using to test if this is repeatable on other users setups.

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Kevin,

 

One of the things I do is set the ZFW that I want and let the FMC do the weight distribution.  This leaves only very minor adjustments that I need to make.  Keeps the aircraft in the designed flight envelope. :-)

 

Billy Bluestar

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Kevin,

 

One of the things I do is set the ZFW that I want and let the FMC do the weight distribution.  This leaves only very minor adjustments that I need to make.  Keeps the aircraft in the designed flight envelope. :-)

 

Billy Bluestar

Hi Billy,

 

Interesting surname. ;) That's what I do too, keeps things easy. Santiago hasnt said what weight and CG he used but I'd expect he did the same. But if the CG was out of limits then the FMC calculated stab setting might well not be a good value. Also much of the stab setting data in the manuals would be created by calculation, not from flight test, so it's quite possible settings between flight test data points might not be as accurate and the aircraft more out of trim than expected. Also this is a sim so the relationship between CG and stab setting will not be perfect.

 

All good reasons for a variation in performance. I think this kind of thing makes the sim seem more real. In reality the CG won't be exactly as per loadsheet so trim after takeoff won't be exactly correct.

 

Cheers

 

Kevin

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Kevin

 

You are completely Right!

 

That´s the point.

 

After takeoff the aircraft is not maintaining a proper trimming position as Kevin and I stated above. I say again, this problem is not happening with other NG variants. All flight I do are planned accordly with real world procedures. Probably the FMC takeoff trim calculation might not be accurate, just saying.

Try all ZF weights. Ex: 51.4 Kgs.

 

About descent pitch & rate of desc here is a screenshot:

 

https://fbcdn-sphotos-g-a.akamaihd.net/hphotos-ak-xap1/t31.0-8/10900094_594527654013440_6316890047133082797_o.jpg

 

 

Thanks Kevin!

 

Santiago

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Santiago,

 

Your picture does not tell me anything.  I do not see a problem.  A/S is stable, about 7 degrees nose down, the engines appear to be at flight idle and the aircraft is on profile in a descent to 22.  That is what it is suppose to be doing, BWDIK. :-)

 

Billy Bluestar

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After takeoff the aircraft is not maintaining a proper trimming position as Kevin and I stated above. I say again, this problem is not happening with other NG variants. All flight I do are planned accordly with real world procedures. Probably the FMC takeoff trim calculation might not be accurate, just saying.

Try all ZF weights. Ex: 51.4 Kgs.

I've tried various weights and flap settings, none give me unusual pitch down after takeoff. It's not exactly in trim but it's close, just as with the other variants.  The FMC stab trim setting agrees well with the FCOM tables.

 

The thing is the stab trim setting gives you an initial trim position. However you are in command and if it's out of trim for some reason you need to adjust. I don't see and error with the -700 version on my installation, never have.

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About descent pitch & rate of desc here is a screenshot:

 

 

 

https://fbcdn-sphoto...133082797_o.jpg

Santiago,

 

Two things struck me from your screenshot (which really should have shown weight in the FMC to be more help). Your descent speed is very high and your Vref is very low (108). That is the lowest Vref published for the -700 and equates to a weight of 90,000 lbs at Flap 40. So your aircraft is virtually empty. The descent profile indicates you have a Cost Index of around 100, which is high for a 737.

 

High CI means a very high descent rate. The sim is doing exactly what it should, there is no bug. The low weight also ties in with the stab trim setting you were reporting (4.5 units). I would suggest you fly the -700 at more normal weights and with a much lower CI (I usually use 30). You will also find it much less sensitive in pitch when you takeoff.

 

Kevin

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Yeah, I think the -700 is one of the sweetest to fly. Never noticed a trim problem on T/O (errr... unless I forgot to set it). In reality, if it's in the green band you're good to go. Once airborne trimming becomes so automatic that I never notice it.

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I've never noticed any real difference in takeoff trim with any of the four variants.

I fly the 700 the most out of the four, and I might be trimmed just a tad low sometimes,

but only a slight amount to make me a bit below the target looking at the HUD.

And that could be the way I fly too.. I've always tended to fly out just a tad low for some

reason rather than higher. But I can let go of the yoke and still be fairly stable say if going

to LNAV/VNAV at 400 AGL. And all the other variants act the same as I fly them.

It's only after I start picking up more speed that the trim needs to be adjusted a bit.

And I've always set the takeoff trim according to the performance page.

 

Kind of agree about the variants.. The 600 and the 700 are my favorites as far as the

overall feel. The "slipperiness" seems just right. The 600 seems quite realistic, and pretty

much like I'd expect. About like a 500 with a glass cockpit. And as it should be with no winglets,

the 600 is the least slippery of the bunch. The 700 is just a tad more slippery, and I would

expect that being all the ones I run have winglets. I've never actually run the 700,800 or 900

non winglet versions. Not even once..  :/  When I go to the 800, it feels quite slippery in comparison.

Maybe even more than the 900, but I've never really done a hard comparison between the two

longer models to see if the 900 is as slippery as the 800 feels.

 

As far as CI, when playing Southwest buoy, I've been using 36-38 lately.  Don't have a clue

what they actually use in the real world. When I fly the private 600, I usually run about 45.

I like to see in the mid 290 knot range + - as far as the climbs to cruise.. And I adjust the CI for

that. Usually the descents will be around 282-284 + - for the 700, and around 290 for the 600 if

the CI is 45.

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As above, it'd be great it you could post your Cost Index for the above flight. I haven't used much above CI26 when I last flew the NGX and I don't ever recall seeing such high speeds.

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