A couple of MB notes...

Rami

Rami

Administrator
Staff member
Hey gang,

My life has calmed down just enough so that I am starting to work in MB again. With that said, I've run into a minor problem that I want to ask about...

1) Does MB have a "hard" altitude cap? I want to get my B-17s and B-24s to bomb from real "nosebleed" altitudes of 30,000-31,000 feet, but CFS2 seems to have a hard cap of about 28,000. I tried adjusting the [MISC.DATA] sections of the .dp files, but that didn't seem to help. Is this a hard-wired setting? Can it be changed?

2) Has anyone noticed that the "late" version of the FDG2 B-17G has severe pitch oscillations and "porpoises" at bombing altitude?

Just venting...
 
Reply....

Herr Dirt,

Thanks, but I'm not talking about free flight. I'm referring to the maximum altitude that you can set aircraft flights in Mission Builder. I want to get them close to or above 30,000 feet, but I am wondering if it is not possible to do so.
 
It's depenent on the flight model of the aircraft being used. The Alphasim B17G tops at 37,000, the updated Gnoopy B-29 at 45,000. I checked these in MB
 
Reply...

Kurt,

This is the original "misc.data" section of the FDG B-17 (And the Alphasim B-24s, for that manner)

[MISC_DATA]
unit_family=2
category=2
allegiance=7
max_group_size=8
min_speed=240
cruise_speed=343
max_speed=515
min_alt=50
cruise_alt=5689
max_alt=8534
entered_service=5/1/42
crew=10

Now, I know how to adjust the altitude settings, (which are in meters) but when I do this, it still will not allow me to set the AI height above that 8,534 meter cap.
 
Rami,

Try looking at the DP for the bomber you are flying. In the DP section look in the [MISC_DATA] section for:

[MISC_DATA]
unit_family=2
category=2
allegiance=3
max_group_size=8
min_speed=140
cruise_speed=220
max_speed=500
min_alt=250
cruise_alt=10000
max_alt=39000
entered_service=1/1/44
crew=11

The above data are from the Gnoopy-Ghostrider B-29. Perhaps some tinkering with cruise and maximum altitude entries would help get your plane a bit higher.

In looking back at my old Defense of Japan campaign, I see that the WP altitudes for the AI aircraft are at a maximum of 27,500' ASL. As I recall, I had wanted to use 30,000' when I made it, so I ran into the same problem that you are having now.

As for the marine mamal tendencies of your B-17G, have you tried a different flight model? It sounds like a center of ballance issue.
 
Drew: I just tried a quick test of the FDGv2_F6F-5_VF-12 Hellcat at 32,000 ft in MB. It set and saved okay.
We discussed this on SKYPE last night and worked on the assumption it was dictated by the dp or the MB engine. Apparently the second choice is not true. Maybe Captain K is right and it's mdl or the airfile?
 
Reply...

I checked the airfile and there's nothing about ceilings. However, it seems to work on my laptop, so I'll have to check it out when I get home.
 
Use AirED

Open the Engine CFS+ Piston Engine tab and change the *Critical Altitude=35000.000000.

View attachment 30889

Also delete your *.CDP file in your aircraft folder. Also update your *.Dp file to reflect this change. Even the experts forget to do it from time to time.
Then open MB and create a "NEW" mission with just the aircraft your attempting to get to cruise at 30,000 create a couple Waypoints that reflect this altitude and check the box "enable warp" then create 1 or 2 events with triggers that allow you to enable warping to these Waypoints.
I just had the very same issue not to long ago with a different aircraft.
I found that after changing the air file and creating a new MB mission that the problem was gone. It worked for me and I hope this works for you.

Steve2112
 
Reply...

Got it taken care of. Thanks, fellas!

Steve2112,

Thanks, but that advice is actually not sound, and I'd like to explain why. That "critical altitude" is not a reference to the aircraft's operating height.

Critical altitude - "The maximum altitude at which a supercharger can maintain a pressure in the intake manifold of an engine equal to that existing during normal operation at rated power and speed at sea level without the supercharger. "

In layman's terms, "critical altitude" actually refers to the highest height at which the supercharger can "trick" the engine by compressing the incoming air to the point that the engine can reach its maximum rated power with the throttle wide open.

You may have come across accounts of aircraft like the P-39 and P-40, whose Allison engines were equipped with a single speed, single-stage supercharger. The net effect of this was that the engine (and consequently, the aircraft's) performance fell off rapidly after 12,000 feet, for exactly the reason I stated in the previous paragraph.

The P-51 (Merlin version) Mustangs were equipped with two-stage, three-speed superchargers which allowed their engines to "breathe" efficiently up to the thin air of 25,000-30,000 feet over Europe.

Make sense?
 
Ah ha nice

Good to know - I will have to correct that then in my air file. So what did you do to correct your intial the problem?
 
Answer...

Steve2112 said:
Good to know - I will have to correct that then in my air file. So what did you do to correct your initial the problem?
Click to expand...

I altered the [MISC.DATA] section in the .dp file so that the maximum operating ceiling for the B-17f is 37,500 feet (11,430 meters) and the B-17G is 35,600 feet. (10,851 meters)

I also changed the P-51d Mustang's data to reflect a maximum operational ceiling of 41,900 feet. (12,771 meters) Its top speed was also WAY too low, it was set in the .dp file for a max speed of about 370-375 MPH, I altered it so that it tops out at the stated max speed...437 MPH (703 km/h).
 
Hi Rami,

Regarding the porpoising, I looked into the flight model. The model's flight model aerodynamic balance is off. The COG is set at -0.83 (aft) instead of 0.0. The MOI (moments of intertia) are set at only about half of what it should be for the pitch. Roll and yaw are also not where they are supposed to be. In other words, it does not have a stable fight envelop.

You could completely redo the flight model, or you could try this quick and dirty adjustment to the aircraft config file pitch and trim scalar to tame the pitch porpoising. It's cheating sort of, but it does work. Adjust the numbers until you are happy with the effect:

[flight_tuning]
cruise_lift_scalar=1.0
parasite_drag_scalar=1.0
induced_drag_scalar=1.0
elevator_effectiveness=1.0
aileron_effectiveness=1.0
rudder_effectiveness=1.0
pitch_stability=4.0
roll_stability=1.0
yaw_stability=1.0
elevator_trim_effectiveness=4.0
aileron_trim_effectiveness=1.0
rudder_trim_effectiveness=1.0

It slows the pitch down to a slow movement instead of porpoising, and the trim effectiveness increases to where it can be trimmed level fairly quickly. It still takes off and lands easily.

It would also be good to have an autopilot added to the panel so you could peg the altitude while you are sighting for your bomb run. But that's another story.

Let us know if it works for you. :wavey:
 
Reply...

Cody Coyote said:
Rami could you post the [MISC.DATA] sections here for both B-17's and the P-51 you modified?
Click to expand...

Cody Coyote,

Certainly! :salute:

This for the Ac Wai P-51d

[MISC_DATA]
unit_family=1
category=1
allegiance=7
max_group_size=8
min_speed=160
cruise_speed=530
max_speed=703
min_alt=50
cruise_alt=5893
max_alt=12771
entered_service=3/3/44
crew=1

(This is in the metric system)

FDG B-17F (Early)

[MISC_DATA]
unit_family=2
category=2
allegiance=7
max_group_size=8
min_speed=240
cruise_speed=343
max_speed=515
min_alt=50
cruise_alt=5689
max_alt=11430
entered_service=1/1/42
crew=10

(This is in the metric system)

FDG B-17F

[MISC_DATA]
unit_family=2
category=2
allegiance=7
max_group_size=8
min_speed=240
cruise_speed=343
max_speed=515
min_alt=50
cruise_alt=5689
max_alt=11430
entered_service=5/1/42
crew=10

(This is in the metric system)

FDG B-17G (Early)

[MISC_DATA]
unit_family=2
category=2
allegiance=7
max_group_size=8
min_speed=240
cruise_speed=343
max_speed=515
min_alt=50
cruise_alt=5689
max_alt=10851
entered_service=7/1/43
crew=10

(This is in the metric system)

FDG B-17G

[MISC_DATA]
unit_family=2
category=2
allegiance=7
max_group_size=8
min_speed=240
cruise_speed=343
max_speed=515
min_alt=50
cruise_alt=5689
max_alt=10851
entered_service=1/1/42
crew=10

(This is in the metric system)
 
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