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737-300 Classic - New and Improved

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Re: 737-300 Classic - New and Improved

Postby Pierre.Mueller » Sun Dec 29, 2013 6:07 pm

Soitanen wrote in Fri Dec 27, 2013 9:17 am:e-pilot, please, make changes in fdm file...


Now, that explains a lot!!

e-pilot was using a very, very old version of the 737-300! That's why I never experienced the problems mentioned here.
The problems mentioned usually appear when approaching much too fast. So keep to the Vref speeds given in the help-menu of the 737-300 available here or via FGData.

But according to the GIT-history (https://gitorious.org/fg/fgdata/history ... 37-300.xml)
the fdm never had the bug with the wrong ground effect on lift table.

With other words- the one in FGdata is and was working correct.

I hope still for a correct 737-classic. With realistic MCP-Panel (not the one from the 777!!) , PFD, steam gauges and realistic working Autoflight System. All informations needed are available on the web! :D

Cheers
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Re: 737-300 Classic - New and Improved

Postby Soitanen » Mon Dec 30, 2013 8:06 am

Pierre, you are not right. Mistake is not in lift table, but in drag table and git version also have this error. So it needs to be fixed in git also.
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Re: 737-300 Classic - New and Improved

Postby Pierre.Mueller » Mon Dec 30, 2013 1:31 pm

Soitanen, you are right, I'm sorry!
Mr. Culp said that the bug should be in the ground effect lift table, so I looked there.

Nethertheless, I tried the corrected fdm, and from my subjective point of view I don't see much difference than before. (What is good, as it behaves like described by many pilots; flightmanuals etc...)

It does not surprise me much:
h_b-mac-ft is actually the ratio of height of AeroRP over the wingspan - the bug appears only between 0 and 0.1 "h_b-mac-ft"- means at 0 "h_b-mac-ft" it got factor 10 less drag (kCDge), at more than 0.1 it got factor 1.
On normal ground run I only see a difference of factor approx. 4 of kCDge. (now 0.48 kCDeg vs former 0.18 kCDge)

The bug started at 0.1 "h_b-mac-ft" which is is about 15ft AGL- a height where you usually begin to put the thrust levers back to idle.

So the effect of this bug does not completly explain why you got trouble landing the 733. Even with the bug I never could reproduce you experience

Are you aware of that?:
737-Classic landing technique: http://www.b737.org.uk/landingtechnique.htm#Flare_and_Touchdown
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Re: 737-300 Classic - New and Improved

Postby Soitanen » Mon Dec 30, 2013 1:53 pm

My bug was, that on full flaps and idle thrust I can fly along runway with very little deceleration. Speed didn't drop, and I can fly half of runway. Now speed drops normally and landing seems to be realistic.
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Re: 737-300 Classic - New and Improved

Postby e-pilot » Tue Dec 31, 2013 3:51 am

Thank you very much for finding that bug Soitanen and Pierre - I have corrected the drag due to ground effect table. I have over 1000 landings in the 733 with the bug in place and have not experienced what you describe, but I have fixed it anyway as it is an obvious bug in the code. Pierre, my 733 does not have a 777 MCP - it is an exact replica of a 737-300 MCP and so is the PFD. If you have that in yours it is not the one I have been working on.

http://www.aesoft.net/temp/737-300.zip
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Re: 737-300 Classic - New and Improved

Postby Honzaku » Wed Jan 01, 2014 11:41 am

Hello guys,
I have to tell sorry to you and particularly to Soitanen that I incorrectly claimed the neutral position of the control column stays same regardless to the trim settings. I is not true. Mach trim actuaator is connected through a mechanical linkage to the stabilizer, so every particular stabilizer position has its own neutral position of the elevator and controll column. It is described explicitly in the document 27-31-00 on this adress:

http://www.pulsaraviation.com/techdata/ ... 1/main.htm

read espetialy pages 9 and 15 it is explained there.

All the best in the new year 2014

Honza
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Re: 737-300 Classic - New and Improved

Postby Soitanen » Wed Jan 15, 2014 11:49 am

Hello all!

I have found interesting graph, which shows wind speed, on which parked plane will make nose-up, due to stabilizer position and CG position (5% and 30% MAC located).
Image
Weight was written, so I calculated actual moments from weight, lift and drag forces and calculated force, that stabilizer generate. After that I recalculate this force into moment and change it due to different gear and CG position, and have graph, showing efficiency of stab due to it's position.
Image
May be I miss something and my whole calculations are wrong? I tried to fly with it, making my mixture control knob on joystick as stabilizer control. It's too sharp, becasu of too small resolution of the knob. Where I can find actual stabilizer change speed?

to e-pilot: may be you can make repository on github with this 737-300, it will be easier to contribute to it. I see some errors and I want to improve aircraft.
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Re: 737-300 Classic - New and Improved

Postby Honzaku » Thu Jan 16, 2014 12:12 pm

Hello Soitanen,

Facts about stabilizer kinematics:

  • The full trim range is 0-17 units. The scale of trim indicator in the cockpit is in these units.
  • 1 unit is equal to 1 degree of stabilizer incidence.
  • If the trim indicator in the cockpit indicates 0 units the stabilizer is +3deg from the fuselage axis (Leading Edge of STAB is in the most upper position)
  • If the trim indicator in the cockpit indicates 3 units the stabilizer is 0deg ( STAB chord parallel to the fuselage axis)
  • If the trim indicator in the cockpit indicates 17 units the stabilizer is -14deg from the fuselage axis (LE of STAB is in the most bottom position)
  • Permissible take-off range of trim for 737-300 is from 1 (CoG at rear limit) to 6 1/3 units (CoG at forward limit)


The Boeing documentation says:

Boeing 737-30/-400/-500 Operations manual:
The authority for each mode of trim is limited to:

  • Main electric trim (switches on the yokes):
Flaps retracted 2.5 - 12.5 units (model 737-300)
Flaps retracted 2.8 - 12.5 units (models 737-400/-500)
Flaps extended 0.25 - 12.5 units (all models)

  • Autopilot trim: 0.25 - 14 units
  • Manual trim (trim wheels on the main pedestal): 0 - 17


Boeing 737-300/400/500 Aircraft Maintenance Manual, Section 27-41: Horizontal stabilizer trim control, page 1:
Normal electric trimming of the stabilizer is done at one of two rates as controlled by flap position. Trim
rate with flaps retracted is 1/3 the trim rate with flaps extended. The autopilot actuator also trims at
one of two rates as controlled by flap position. High speed autopilot rate is equal to the normal electric
low speed rate. The low speed autopilot rate is 1/2 the rate of the high speed autopilot rate.


Boeing 737-300/400/500 Aircraft Maintenance Manual, Section 27-41: Horizontal stabilizer trim control, page 170:
(SUBTASK: 27-41-98-715-030) (EFFECTIVITY: 001999 )

(19)Do a test of the high (flaps down) stabilizer trim rate:
(a) Move the stab trim switches on the control wheel to the NOSE UP (stabilizer leading edge down) position and hold until the stabilizer stops.
(b) Do the following to measure the time it takes for the stabilizer to move from the leading edge down position to the leading edge up position:
1 Move the stab trim switches on the control wheel to the NOSE DOWN position and hold until the stabilizer stops.
2 Make sure that the time from the start to stop of stabilizer movement is between 17 and 24 seconds.

(SUBTASK: 27-41-98-865-031) (EFFECTIVITY: 001999 )

(20)Do this task: "Retract the Trailing Edge Flaps" (AMM 27-51-00/201).

(SUBTASK: 27-41-98-865-032) (EFFECTIVITY: 001999 )

(21)Move the stabilizer to 4 units of trim, or more.

(SUBTASK: 27-41-98-715-033) (EFFECTIVITY: 001999 )

(22)Do a test of the low (flaps up) stabilizer trim rate:
(a) Move the stab trim switches on the control wheel to the NOSE DN (stabilizer leading edge up) position and hold until the stabilizer stops.
(b) Do the following to measure the time it takes for the stabilizer to move from the leading edge up position to the leading edge down position:
1 Move the stab trim switches on the control wheel to the NOSE UP position and hold until the stabilizer stops.
2 Make sure that the time from the start to stop of stabilizer movement is between 43 and 57 seconds.


From these information you can easily calculate stabilizer rates (speeds) in units of trim per second.

Hope it helped

Honza
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Re: 737-300 Classic - New and Improved

Postby Soitanen » Sat Jan 18, 2014 9:05 am

Honza, thanks for stab speeds! I already had all the info you posted here, only seconds for traveling were missed!

I didn't waited for e-pilot's answer and created repo on github by myself.

git clone https://github.com/soitanen/737-300.git

There is version from e-pilot's link (this morning) and 2 small additions (now, will grow).

1. ASI now correctly operates with Vmo needle. It were absolutely wrong. Now it really calculates 0.82M at aircraft location, makes choise between 340 kts or 0.82M (which is smaller) and point it.
2. VSI now shows direct vertical speed, not barometrical. Real aircraft use IRS for this purposes.
3. ALT pressure knob can be controlled via mouse wheel normally, not too big changes in pressure.

My friend is captain of 737 in Transaero, but he have not Flightgear installed. Soon I have planned meet with he and Flightgear, hope he will help to provide some interesting information.

About stabilizer - it's not in repo now, still experimenting, but seems to be plausible.
Also, I tried to compute Cl max via this formula: Clmax=2*weight/(rho*speed^2*wing_area). I used stall speed for different weights in 737 FCTM. And I found some interesting numbers. Cl max for clean wing is 1.48 (in current FDM we have it only 1.20). But more interesting is flaps infuence: at only 5 degrees Clmax is 2.18! Little table:
Code: Select all
Flaps pos   Cl max    delta Cl
   0         1.48       0
   5         2.18       0.7
  15         2.39       0.91
  30         2.74       1.26

Also at this page http://www.b737.org.uk/techspecsdetailed.htm we can find CLmax (Land @ MLW) - 2.88. So my calculations seems plausible, and I have plans to redo FDM (Lift-Drag values, diferent stab and elevator control).
Boeing 737-300. Reworked cockpit, FDM, autopilot and much more. WIP.
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Re: 737-300 Classic - New and Improved

Postby Soitanen » Tue Jan 21, 2014 10:45 am

I have pushed into github first FDM change. Now trimming acts on stabilizer, not on elevator. Outside animation works properly.
What is realized: different speeds of trimming due to flaps position and autopilot engagement, different ranges of stabilizer movement due to flaps position, realistic (as I have calculated earlier) aerodynamic influence of stabilizer.
What needs to be done: possibility to manual trimming (via mousewheel when pointing on trimwheel), add switch STAB OVERRIDE (now stab can be trimmed in any way not regarding to control column position), add stab position indicator near trim wheel. Unfortunately I have lack of 3D modelling skills. e-pilot, come on, give me your nickname on github, I'll give you push right to work together!

I search for info: what gear ratio have trim wheel to stab? How many turns need to be done to move stab for 1 unit, for example? I have overlooked this document (big thanks Honzaku for the link) 27-41: HORIZONTAL STABILIZER TRIM CONTROL SYSTEM, but I cant find the value...
Boeing 737-300. Reworked cockpit, FDM, autopilot and much more. WIP.
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Antonov An-24B. Made from scratch. Very good FDM. 3D model by Adrian. WIP.
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Re: 737-300 Classic - New and Improved

Postby Honzaku » Tue Jan 21, 2014 1:45 pm

Hello Soitanen,

Not sure if it is somewhere in the manual or not. But I googled following values:

268 revolves per full scale (from 0 to 17 units) here:

http://www.pprune.org/tech-log/303968-7 ... -many.html

Well that is for 737-700 but since this manual trim in Boeings is fossil from the times of the good old 707 and nobody uses it anyway I am pretty sure Boeing engineers left it unchanged within the whole 737 family.

This source refers to some pilot report and gives slightly different number 256 revolves (for 737NG):

http://www.737flightsim.com/StabTrim/stabtrim.html

And finally this source mention 250 turns:

http://www.flaps2approach.com/journal/2 ... -tabs.html

So it gives something between 15 and 16 revolves per trim unit.

Anyway, it could be a question for your friend captain. But I doubt he's ever measured it.

Cheers

Honza
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Re: 737-300 Classic - New and Improved

Postby Soitanen » Fri Jan 24, 2014 1:11 pm

Honzaku wrote in Tue Jan 21, 2014 1:45 pm:Anyway, it could be a question for your friend captain. But I doubt he's ever measured it.

Hello! I'm sure, that he never try to count number of revolutions to trim the stab :) But I'll ask!

2 updates in github repo:
- new tiller steering menu: now nosewheel can turn from pedals only for 7 degrees (like real one), ground steering must be using tiller. Just open menu, grab knob and rotate it. Number in degrees is current position of nosewheel (you can turn pedals and see changes).
- new spoilers logic: fixed animation of ground and flight spoilers (they were confused). Now keys "j" and "k" controls Speedbrake lever (animation is note done yet). It have 7 positions (can be controlled via property tree, see b733/controls/flight/spoilers-lever-pos, soon position will be seen on screen like flaps). Positions:
0 - down
1 - armed
2 - 25% of flight detent flight spoilers
3 - 50% of flight detent flight spoilers
4 - 75% of flight detent flight spoilers
5 - Flight detent
6 - Spoilers up (flight and ground)
If you set spoilers to armed and land, flight and ground spoilers will automatically deploy.
Boeing 737-300. Reworked cockpit, FDM, autopilot and much more. WIP.
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Re: 737-300 Classic - New and Improved

Postby Soitanen » Wed Jan 29, 2014 5:07 pm

New things in github repo:
- improved stabilizer control. Now it based mainly on JSBSim to avoid bugs with Nasal's interpolate function.
- realistic autobrakes. Now autobrakes do not apply simple value to brake controls, but controls deceleration, like in real plane.
Autobrake 1 - gives 4 ft/sec^2 decel
Autobrake 2 - 5 ft/sec^2
Autobrake 3 - 7.2 ft/sec^2
Autobrake MAX - 14 ft/sec^2 when greater than 80 kt, 12 ft/sec^2 when less than 80 kt
Only RTO applies full braking pressure in shortest time.
Also, brakes will change pressure when you will operate with reverser, or spoilers to maintain target deceleration value.
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Project Russia (some cities, based on OSM with custom objects).
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Re: 737-300 Classic - New and Improved

Postby Soitanen » Thu Jan 30, 2014 5:55 pm

And some new updates again:
- another engine max thrust - 20000 lbs. It's base engine for 737-300. 23500 was never installed on -300 (as I found info in internet);
- some aerodynamic coefficients taken from documents, in which aero data are compared between real (taken from data set for 737-300 simulator) and generated by DATCOM. After some test flights I see no flight bugs and decided to push it in repo.
Boeing 737-300. Reworked cockpit, FDM, autopilot and much more. WIP.
Boeing 737-800. WIP. Canvas PFD and ND.
Antonov An-24B. Made from scratch. Very good FDM. 3D model by Adrian. WIP.
Project Russia (some cities, based on OSM with custom objects).
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Re: 737-300 Classic - New and Improved

Postby Honzaku » Fri Jan 31, 2014 7:18 am

Hello,

Here is a summary of the links to some technical data of B737 I have found (some of theme have already been mentioned in the thread):

Aircraft Maintenance manual Part 1

http://www.pulsaraviation.com/techdata/ ... 1/main.htm

Aircraft Maintenance manual Part 2

http://www.pulsaraviation.com/techdata/ ... 2/main.htm

Structural repair manual:

http://www.pulsaraviation.com/techdata/ ... M/main.htm

Illustrated parts catalogue:

http://www.pulsaraviation.com/techdata/ ... n-main.htm

Wiring diagram manual (electro-installation):

http://www.pulsaraviation.com/techdata/ ... M/main.htm

All the links above come from various parts of this site, where other interesting stuff might be found:

http://www.pulsaraviation.com/techdata/

Maintenance Facility and Equipment Planning Document:

http://amis2000.aerolineas.com.ar/D626A ... PD___N.PDF

Some wind tunnel test results for 737-100 (regrettably, the data are not relevant for 733 due to different wing), for some reason these NASA report links don't work in Firefox, you have to use Internet Explorer:

http://ntrs.nasa.gov/archive/nasa/casi. ... 031373.pdf

few lift and drag coefficient values could be dig out from this book, see pg.227-236:

http://books.google.cz/books?id=V1DuJfP ... ft&f=false

Regrettably, there is absolutely no data for coefficient curves, even bloody basic lift and drag curve vs. AOA are impossible to find.

Honza
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