Jump to content

Sign in to follow this  
strider

Problem with take offs.

Recommended Posts

First, thanks to everyone who helped me with the FMC...I got it completely configured for a flight and it worked as advertised. The main problem I'm having, and have had for every 737-800 flight (only 737 I've tried, to date), is that the aircraft goes way past Vr and eats up all sorts of runway before it will rotate and lift off. This isn't an FMC issue as it happens when hand flying OR with a fully programmed FMC and TO/GA activated. I've triple checked all my take-off settings for my GW, CG and OAT against the charts and all looks good to me. A bit of info from my last attempt (fully programed FMC and TO/GA activated after 40% N1 reached):737-800KBOS 04LGW= 152,000 lbs.OAT= 15* CFlaps= 10*V1= 145Vr= 146V2= 154 (FMC agreed with these chart numbers within 1 KIAS)Trim= 4.9Wind= 0CG= 26.5 I throttled up to 40% N1 and stabilized, activated TO/GA and engines spooled up to 98% N1 (agreeing with the charts). At 146 KIAS I pulled back on the stick, at 150 KIAS the end of the runway, and the river beyond, was getting very close. At 156 (approx....I was a little busy ;-) ) she finally rotated and left the ground. I'm pretty sure the mains got a nice washing in the St. Charles River before being stowed! So, what am I missing/doing wrong? On a side note...Is there a "spot" on the panel to adjust trim or is it keyboard or contoller buttons only? Thanks for looking! Vic


Victor Buck

Share this post


Link to post

Vic,Sounds like a trim issue or you have your load center of gravity misconfigured. Try trimming 5.5 or 6 before takeoff and tell us if that improved the takeoff run.Hope it helps,


Mats Johansson
PMDG Flight Test Dept
Boeing777_Banner_BetaTeam.jpg

| Asus Z270-A | Intel i5-7600K @ 4.8 GHz OC/H2O | nVidia Geforce GTX 1070 8GB OC/O2|

Share this post


Link to post

That was going to be my next attempt at solving this...but why wouldn't it work with the 4.9 trim figure given by the fully programed FMC? Does the CG 0f 26.5 look out of line? In your experience with the 737, do you normally have to add .5 to 1.0 trim above and beyond what the FMC says is good? The documentation stops giving TO trim settings after the -700 so...That's the one setting I don't have a chart for in the -800 or -900. I use the load configurator to load the aircraft, I assume it would do so in a balanced manner (as far as PAX)? Anywho, I'm off to try with more nose up trim. Thanks!! Vic


Victor Buck

Share this post


Link to post

No joy. Same weight, temp, flaps and CG info but went to 7.0 trim...still didn't rotate until over 164 KIAS. Washed the mains in the river again. I'm completely baffled...not that this is a NEW state for me :( . I have no idea where to go from here. I can't safely fly the aircraft this way. Vic


Victor Buck

Share this post


Link to post

Vic,The trim and CG figures in the NG are fixed values. Have you used any third party cargo/pax loader? Can you attach the Weight and balance section of the aircraft.cfg file for the aircraft in question so we can take a look at it?Hope it helps,


Mats Johansson
PMDG Flight Test Dept
Boeing777_Banner_BetaTeam.jpg

| Asus Z270-A | Intel i5-7600K @ 4.8 GHz OC/H2O | nVidia Geforce GTX 1070 8GB OC/O2|

Share this post


Link to post

Mats, I didn't use a third party loader, just the PMDG "Load Manager".I've pasted in the Weight and Balance section from the 737-800 (no winglets) below. Let me know if any other information would be helpful. Thanks!![WEIGHT_AND_BALANCE]reference_datum_position= 52.786, 0.000, 1.861 // Vector of Boeing RFP to visual mode centre !! People DO NOT TOUCH !!empty_weight_CG_position=-57.770, 0.000, 0.000max_number_of_stations=50empty_weight=91300.000empty_weight_roll_MOI= 1630328.70empty_weight_pitch_MOI= 2103844.05empty_weight_yaw_MOI= 1754301.78empty_weight_coupled_MOI=202.00//station_load.0=1440.0, -57.450, 0.000, 1.050//max_gross_weight=173000.000CG_forward_limit=0.133CG_aft_limit=0.330station_load.1=18180.0, -57.450, 0.000, 1.050station_load.2=4990.0, -57.450, 0.000, 1.050station_load.3=4977.0, -57.450, 0.000, 1.050 Vic


Victor Buck

Share this post


Link to post

Vic,I tried a takeoff with the load config as stated and the data posted in your initial post. Trim set to around 5 and I took off well before runway end. I got a lower Vr (149 knots) than you and she was a bit lazy on the rotation but overall a good t/o.Have you tried to reinstall?Hope it helps,


Mats Johansson
PMDG Flight Test Dept
Boeing777_Banner_BetaTeam.jpg

| Asus Z270-A | Intel i5-7600K @ 4.8 GHz OC/H2O | nVidia Geforce GTX 1070 8GB OC/O2|

Share this post


Link to post

I'll try to re-install later this week, I'm going to the mountains for the rest of the weekend. Should I use the "removal tool"...or is that not necessary? We'll get this working yet! Vic


Victor Buck

Share this post


Link to post

Yes please use the removal tool. If you have the 747 installed as well you might need to reinstall that on top of the NG. See http://ops.precisionmanuals.com/wiki for details about the NG and 747 installs.Hope it helps,


Mats Johansson
PMDG Flight Test Dept
Boeing777_Banner_BetaTeam.jpg

| Asus Z270-A | Intel i5-7600K @ 4.8 GHz OC/H2O | nVidia Geforce GTX 1070 8GB OC/O2|

Share this post


Link to post

John... I checked my calibration and it looks OK (recalibrated anyway, while I was there). This brings up an interesting point. I have, in my, FS9.cfg, the line "STICK_SENSITIVITY_MODE=0", under the {CONTROLS} heading. I have used this for years as it "de-sensitizes" the controller and makes it much more realistic (it was always too sensitive without the line added). I've never had a problem with this entry, before, but I've never had the PMDG 737 before, either. Also, regarding the FS9 "sensitivity" sliders, my understanding is that you can have the SENSITIVITY sliders less than full right (max) and still get full control surface travel. I've always set these to more accurately reflect how I would expect a certain aircraft to react to control surface inputs (having NO clue as to how they really do!). Is it true that full control surface travel is possible with less than "max" sensitivity? Is there a place, in the cockpit displays, that will show control surface positions? I haven't noticed it...doesn't mean it isn't there. ;-) Mats, I'd like to investigate the possibilities John raises before doing a complete re-install of the 737. I don't own the 747 so it should be a straighforward operation using the "removal tool" as you suggested. Thanks gang! Vic


Victor Buck

Share this post


Link to post

AHA!! We may be onto something here. I found the "control surface position" indication...apparently it's only available in the lower EICAS window when in "over-under" mode? Anywho, I stroked my flight controls with my usual sensitivities settings (about 60%) and they DO NOT go to full deflection as I had assumed. I put my aileron/elevator/rudder sliders to full right (max) and they then had full range of movement. If I had to guess...this would be my problem?? :-lol I'll try it here, shortly, to see. While you're here...are the switches in the screenshot below supposed to work? They don't for me and I have yet to find a mention of them in the manuals. http://forums.avsim.net/user_files/159425.jpg


Victor Buck

Share this post


Link to post

Vic,Glad you've found the culprit. The joystick settings in FS is quite crude. If you would like some more options you should consider buying a registered version of FSUIPC where you can change slope, curvature, sensititvity and so on.The DU switching is not implemented on the PMDG NG.Hope it helps,


Mats Johansson
PMDG Flight Test Dept
Boeing777_Banner_BetaTeam.jpg

| Asus Z270-A | Intel i5-7600K @ 4.8 GHz OC/H2O | nVidia Geforce GTX 1070 8GB OC/O2|

Share this post


Link to post

Mats, Boeing Fixer... The sensitivities were the culprit. With them at 100% she rolled right up and lifted off...at the indicated Vr speed! I'm happy we found the solution. I have had a registered FSUIPC for years but never got that deep into the "controls" portions of it. I have a new set of CH pedals, yoke and throttle quadrant waiting for me to figure out how to set them up. That has been another "learning experience" that's nowhere near to being finished. Thanks guys!! Vic


Victor Buck

Share this post


Link to post

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this  
  • Tom Allensworth,
    Founder of AVSIM Online


  • Flight Simulation's Premier Resource!

    AVSIM is a free service to the flight simulation community. AVSIM is staffed completely by volunteers and all funds donated to AVSIM go directly back to supporting the community. Your donation here helps to pay our bandwidth costs, emergency funding, and other general costs that crop up from time to time. Thank you for your support!

    Click here for more information and to see all donations year to date.
  • Donation Goals

    AVSIM's 2020 Fundraising Goal

    Donate to our annual general fundraising goal. This donation keeps our doors open and providing you service 24 x 7 x 365. Your donation here helps to pay our bandwidth costs, emergency funding, and other general costs that crop up from time to time. We reset this goal every new year for the following year's goal.


    2%
    $715.00 of $25,000.00 Donate Now
×
×
  • Create New...