Project Dornier Do-17z2

[Ivan]

Armament and Autopilots

Hello Aleatorylamp,

A couple of my mechanics and a pilot decided to check out your Dornier 17Z.

The pilot came back after his first flight muttering something like "etwa unstabil".
The mechanics then did a few checks and here is what they found.
The Moments of Inertia were quite a bit off from where the mechanics had calculated.
The numbers they calculated were
27950 -- Roll
30200 -- Pitch
56766 -- Yaw

What they found was
48674 -- Roll
60982 -- Pitch
81478 -- Yaw

The chief mechanic's comment was that if something were a couple thousand off, it wasn't a big deal because the numbers are estimates anyway, but when the numbers are 50% to 100% off, they need to be corrected.

That by itself cured most of the Autopilot issue, but changing the Trim Pitch Effect per Notch from 0.25 to 0.30 made things become stable more quickly and did not seem to hurt anything.
The aeroplane still will not stabilize below about 3-5 feet per minute climb but that can be cured by setting the autopilot to descend and then quickly changing back to hold altitude. It is much like giving the TV a rap on the side and having things clear up.

The pilot also commented that he didn't like the way the Dornier was sitting.
There was a noticeable jolt as he entered the aeroplane, so the mechanics adjusted the ground angle slightly.

Let me know if my revisions address the problems on your autopilot as they did on mine.


Regarding Armament:
It isn't a matter of selecting three swivel guns.
It is a matter of there being ONE Dorsal Gunner, One Ventral Gunner, and One Nose Gunner who has to decide which position to occupy.
You ARE the designer though, so if you decide that your crew will be located differently with no one to man the ventral gun then who am I to tell you that you can't do it?
It is no more illogical that my declaration that my FW 190A would not be clean without any ETC racks installed.
Then again, I don't know that I have EVER seen any FW 190A in CFS with a bomb rack installed.

- Ivan.

 

[smilo]

for some reason, i'm unable to open the file.

 

[Ivan]

Eeek!

I also can't open the other file.
I resent via email to both of you and attached another ZIP to this post.
I don't have WinZip on my laptop so this was done with 7Zip.
Hope it works.

- Ivan.

 

[aleatorylamp]

Hello Ivan,
Thanks for e-mailing the .airfile. I only have Winzip like Smilo - maybe I should install 7zip as well!

Thank your mechanics very much for the new MOI´s, the ground angle and the elevator trim.
I´ve just tested the aircraft and it flies nicely. The Autopilot, however, keeps doing the same thing as before, and requires a bit of manual damping with the joystick to reduce the oscillation, and it helps to go to 4x sim rate to quickly stabilize it to near zero.

I don´t want to argue, but I still don´t understand why you would like only one swivel gun.
With 4 guns and 3 gunners, one position would be unmanned, so I thought that was to be the only fixed one.
If we were bombing or operating the top front gun, we would have a bombardier/front gunner sitting next to the pilot, so the top front gun would be the swivel gun, and the lower one would be unmanned. The other two gunners would the rear gunners, ventral and dorsal one, so they would be swivelling too. That´s why I thought 3 swivel guns.

Thanks again!
Cheers,
Aleatorylamp

 

[smilo]

having a middle of the night,
old man moment...old men understand.
as always, am awake for an hour or so.

i don't think the issue with the air file download
is Win7. i have Win7 on my laptop
and couldn't open the file.
i got the email and am testing it now.

once again, i engaged ap while climbing.
got severe bucking.
throttled back to 80%
disengaged altitude hold
and manually leveled out to a very slight climb.
then, reengaged altitude hold.
am currently cruising at 6560 feet
with a very slight altitude increase.
i can live with that.

i am not using an ap gauge.
merely, keyboard commands
for ap master and altitude hold.
i have no doubt,
settings would be fine tuned
with an ap gauge.

thank you for your work, Ivan.
as you said, you may not be
an armament expert, but,
you're a hell of an air file technician.

 

[Ivan]

Hello Guys,

Try the second attachment It should work. I have no idea what happened to the first attachment.
It was created on a machine I normally use only for games. I don't know if I have ever used that copy of WinZip before.


Hello Aleatorylamp,

I think there is a lot of miscommunication going on here and I am probably the guilty party.
From your last post, it sounds like we are in pretty good agreement here.
I was just trying to point out the two aft facing gun positions manned but now I think you already agree there.


Hello Smilo,

It sounds like you first tried to go from controls deflected for climb to altitude hold by the autopilot.
That doesn't sound like a reasonable thing to do in real life.
Can you tell us what the proper keyboard sequence is for setting autopilot and altitude hold?
I would like to try it out also.


If you want to make the autopilot become stable quicker, the Trim effect per notch can be increased.
What I have seen in other aircraft is something around 0.80 to 1.00 or so.
My FDE notes (in the FDE Control File) say that 0.50 is a pretty normal value.
The value here started at 0.25 which also did stabilize but not quickly and would jump back and forth a notch or two even when stable.
That is why I changed it to 0.30.
0.40 worked about as well, but I thought that Aleatorylamp wanted the finer adjustment.
As the number gets bigger, the adjustment gets coarser but the autopilot finds the center more quickly so as usual, it is a matter of balancing one thing against another.

I am still wondering what is causing the slight climb that doesn't even register on the vertical speed indicator but can be seen in the altimeter.

- Ivan.

 

[smilo]

first off, the trim/auto pilot settings balancing act.
i take full responsibility for the fiasco.
early on, i complained about not being able
to fly straight and level.
(something i've always had difficulty achieving)
Stephan solved my problem
by making the elevator trim more sensitive
and it worked great. unfortunately, later,
when i tried to use auto pilot,
there was a problem with altitude stability.
it's a classic example
of one wanting his cake
and eating it too.
i can only say, i appreciate your efforts
at catering to my whims.

as a general rule, i usually have a functioning
auto pilot gauge on my panel.
with it, i can preset a desired altitude,
heading and climb rate, start the engine(s),
accelerate and take off and eventually,
reach my selected altitude and heading.
the aircraft maintains that heading and altitude,
unless i make adjustments to the gauge settings.
all pretty spiffy for long waypoint missions
and gnats ass accurate bomb runs.

okay, so, i have a basic auto pilot gauge set up
that hubba put together.
with it, you can engage ap,
engage and adjust heading,
and engage altitude hold.
BUT, can not adjust altitude.

next, you need to understand,
i'm a notorious keyboard assignment tweaker.
back in the day, i think it drove hubba crazy.
anyway, i've changed the settings so much,
i can't remember what the default assignments are.

if you go into settings/customize controls/assignments
scroll down to a section for Autopilot assignments.
you'll need to assign a key (i use z) for Autopilot master,
i've selected F9 for Autopilot altitude hold.

notice there is a heading hold option
and, if you scroll down,
Autopilot heading bug increment
Autopilot heading bug decrement
it's your call which, if any, to select.

here's where i have a complaint.
why no altitude increase and decrease options?
so it goes

finally, i forgot to mention,
why the auto pilot fiasco with the do17?
especially, if i use an auto pilot adjustment gauge?
well, i haven't installed an ap adjustment gauge
in the do17 panel, yet.
i'm less than ecstatic about using
the only stock one available.
the lear ap gauge.
another option is one i've downloaded,
the sperry mkIII, which is, at best,
cumbersome to try adjusting settings
and relies on heading and altitude hold.
it looks cool, though.
i'm still searching.

ramble on, milo, ramble on

 

[aleatorylamp]

Hello Smilo, Hello Ivan,
Intesesting information on autopilots, I must say. I was trying corrections in the opposite direction.

I had always had the wrong impression that what caused the porpoising was excessively high trim values that would overshoot the mark and make things progressively worse, but it seems the other way round, that excessively LOW values correct progressively later. It is still pushing in one direction when it should be pushing the opposite way to damp the oscillation instead of helping it.

I´ll experiment with higher settings then.

OK on the guns then - Clarified!

Cheers, and good night again!
Aleatorylamp

 

[aleatorylamp]

Elevator Trim

Hello Ivan,
Yes indeed, a higher setting of 0.40 works very well, and autopilot oscillation wanes quickly!
Strange, back in the days of FS98, everyone started complaining is values were above 0.25. Different Sim, different Values!
Thanks for your trouble.

Hello Smilo,
...and here´s the .air file! I think it will be fine. I also adjusted the other values Ivan mentioned.

Enjoy!
Cheers,
Aleatorylamp

 

[smilo]

thank you, Stephan.
i'll check it out.
just to let you know,
Ivan, emailed his update a few days ago.
if i'm not mistaken,
the email was sent to both of us.

 

[aleatorylamp]

Hello Smilo,
Yes, but the porpoising still set in, and afterwards he suggested increasing the elevator trim value to 0.40, which is what the .air file I posted contains.
Cheers,
Aleatorylamp

 

[smilo]

okay...i'll download and install yours.

 

[smilo]

am running a quick test.
when engaging ap altitude hold,
even in a steep climb,
the aircraft levels out quickly,
with a minimum of oscillations.
...and seems to hold altitude
with a mere 1 foot variation.
excellent work...well done.

if only i could do as good of a job
building a nose glazing bmp
for the bomb aimer panel.

 

[aleatorylamp]

Hello Smilo,
That was thanks to Ivan´s suggestions and your testing!
The Do-17 is certainly getting better and better!
A nose glazing for the Bomb aimer´s panel... Of course, because the Baltimore´s bomber panel is different.
I often cut and paste pieces from other panel struts... but my panels are quite rudimentary.
Anyway, I have to get some sleep.
Good night!
Aleatorylamp

 

[smilo]

yes, she is, isn't she?
i'm very pleased with how she's coming along.

like you, i usually cut and paste parts from other panels.
i've never created one on my own.
i have the basic glazing layout,
but, of course, am not happy with it.
add to that, i have other things going on,
so, naturally, it's on a back burner.

not, out of sight, out of mind,
but, not at the forefront either.

 

[aleatorylamp]

No hurry!

Hello Smilo,

I know the feeling when there are several things going on simultaneously,
added to other extra things like cleaning, shopping, cooking and driving...
No hurry!
Cheers,
Aleatorylamp

 

[Ivan]

Dornier 17Z Model - In Plastic

Hey Guys,

I just received a model of a Dornier 17Z that I ordered about a week or so ago.
Monogram 1/72 Scale.
Haven't had a chance to even open the shipping box yet. Been a busy day.

- Ivan.

 

[smilo]

that's funny, i have one, too.
i bought it years ago when a local hobby shop closed its doors.
is your model Monogram #PA214.150?

 

[aleatorylamp]

Hello!
I remember building a similar model by Revell, the Ju-88 in 1/32 scale - with turning props and retractable gear - amazing technological advances in model building at the time! I never painted models, though. Plain shiny khakhi-green plastic, transparent canopies and lovely decals were better without my painting abilities!
Cheers,
Aleatorylamp

 

[Ivan]

that's funny, i have one, too.
i bought it years ago when a local hobby shop closed its doors.
is your model Monogram #PA214.150?

Hi Smilo,

Mine has the same kit number new in the shrink wrap.
I already have the Matchbox kit but I was thinking that Monogram generally does a better job and the price on eBay wasn't bad.
I suspect this will sit on the shelf for at least a few years like all the other kits have been doing.
I haven't finished a kit since my Son was born and he is now 15.

Hello!
I remember building a similar model by Revell, the Ju-88 in 1/32 scale - with turning props and retractable gear - amazing technological advances in model building at the time! I never painted models, though. Plain shiny khakhi-green plastic, transparent canopies and lovely decals were better without my painting abilities!
Cheers,
Aleatorylamp

Hi Aleatorylamp,

Monogram and Revell merged a few decades ago into Revell-Monogram.
My preference was always for the Monogram kits though; The mould quality / surface finish was better and they seemed more accurate.
Revell's 1/32 scale models were great though. I had a couple of those when I was growing up.
One was the Ki-43 Hayabusa and the other was the Me 109G-6.
I have at least one example of each kit down in my basement and probably should build them at some point.
Even a small fighter in 1/32 scale is pretty big, so that Junkers 88 must be huge!

My assembly and painting skills were never very good though I COULD build a pretty clean model if I tried.
The artistry of painting and weathering was beyond me.
All I ever did was follow the instructions and some of those ideas were pretty worthless.
I still have a few of the built up 1/48 scale Monogram kits from when I was a teen and even a few from my College days.

I always preferred the moving parts in the Monogram and Revell lines to the static stuff in everyone else's kits.
Some folks would say that those features detract from the accuracy of the model and make them toys.
To me, all the plastic kits were toys and I almost never painted any of them beyond the Canopy Frames, Pilot, and Cockpit.

Happy Modelling!
- Ivan.