CFS1 Curtiss-Wright AT-9 "Jeep" Work In Progress.

Tweaking the .air file for the AT-9A

Hi Ivan,
I was a bit wary about tweaking the .air file for the slightly upgraded Fledgeling AT-9A, but after your comments I thought I´d give it a try, and it has been surprisingly straight forward! I´m very pleased with the results.

Specifications state a slight increase in power of 5 hp, and 3 mph in top speed - i.e. 200 instead of 197 mph, which incidentally you thought would be a bit more. Then, there is no mention as to any increase in the 2300 max RPM, which is probably to be expected.

So: I slightly reduced Zero Lift Drag from 77 to 74, slightly increased Engine Torque from 0.65 to 0.658 and slightly reduced Engine Friction from 8 to 7.7.

The results were great: (500 ft level-flight test)
Power went up from 294 to 300 hp,
Speed rose from 199 to 205.5 mph, and
RPM stayed the same at 1294 RPM!

I thought that was quite amazing. It perhaps shows how nicely one can get even tiny adjustments realistically right in the CFS1 FD... Of course, once one knows what to do after being properly shown how to do it, ha ha!

Cheers,
Aleatorylamp.
 
Change ONE Thing at a Time?

I am a bit curious: Why did you change so many parameters at one time?
The end result at 205 MPH sounds a bit higher than you were going for.
Also, is the maximum speed at the same or a higher altitude?
Although I do not believe your climb rate has changed much, I would be very surprised if your ceiling has not changed a touch.

I would have just increased engine efficiency to start and see where that got you. That is a pretty logical reason for a slight increase in engine power with a naturally aspirated engine. (Cleaned up intakes, better induction, cleaned up exhaust or better scavenging, that kind of thing is pretty common for small improvements to an engine.)

It certainly is amazing the kind of control we have for tuning engine power. The only big issue that I still have is the lack of ability to implement multi-speed superchargers.

- Ivan.
 
Hi Ivan,
Thanks for the quick reply!
I had interpreted the comment in your e-mail about the 5 hp and 3 mph increase, that there would be more than just 200 mph, so I thought 205.5 was, even though specs state 200 mph.
The test results are all at 500 ft, with the engines flat-out, not in continuous high-speed cruising.
So I should then rather go for a more moderate number, say 201 mph?
Anyway, I´ll try another tweak with only an engine efficiency adjustment.
Thanks again!
Aleatorylamp
 
Hello Aleatorylamp,

Actually my opinion is that 200 MPH and 205 MPH are the same for all practical purposes.
My first comment was meant to suggest that 5 HP probably would not increase maximum speed by 3 MPH. I would have guessed more on the order of 1 MPH at most.

My second comment was not to suggest that 205 MPH is too high. It was an expression of surprise that with a stated goal of 200 MPH, you were that much higher when I KNOW that it is possible to tune maximum speeds closer. It would make sense if you were trying to match speeds at other altitudes, but you didn't make that statement.

- Ivan.
 
Hello Ivan,
Thanks for your clarification and suggestion. I had understood just the opposite in both cases! Sorry!
OK, then. So what I´ll do, just so as not to put in the same .air file for both planes, even though this could serve for practical purposes, is to tweak the .air file a bit less to account for the slight difference, which seems to be lower than what I came to think recently.
Cheers,
Aleatorylamp
 
AT-9 vs AT-9A level flight 500 ft

Hello Ivan,
Following the argumentation in your suggestions, I returned Engine Torque and Zero Lift Drag back to their previous values, concentrating exclusively on Engine Efficiency (Friction) at 2300 RPM.
Now, exactly as you said, there is only 1 mph difference! (of course...)

AT-9 Lycoming R680-9 (Engine Friction at 8.0; Test flying at 500 ft)
RPM: 2289
Hp: 294
Vmax: 201.8 mph

AT-9A Lycoming R680-11 or -13 (Engine Friction at 6.5; Test flying at 500 ft)
RPM: 2289
Hp: 300
Vmax: 202.8 mph

In view of this success, the AT-9A´s .air file should now be fine. Would you agree?
Thank you once again for your counsel and patience!
Cheers,
Aleatorylamp
 
Hello Aleatorylamp,

Hmmmm.... I think you misunderstood my recommendation. Perhaps I was not being very clear with bad terminology.

The idea I was intending is this:
If you have the same basic engine in an "improved" version, you will likely find changes that affect "Efficiency" or the amount of Torque produced because restrictions would hopefully be reduced with the newer version.
(Record 508)

THIS is what I meant by increased efficiency.

Friction would likely remain the same (unless you need to tune it to accomplish something else).
(Record 509)
On a supercharged engine, Friction is actually more likely to INCREASE because although a later model may produce more power,it also may have to drive a larger supercharger.

Of course, once you get your basic numbers, you may want to balance the two to get the altitude performance you are looking for.
http://www.sim-outhouse.com/sohforums/showthread.php?77148-Engine-Performance-Tuning-Tutorial

Someone should sticky that thread. I find that I am pointing back to it very often. It saves a lot of typing.

Once you have got your proper engine output, THEN you adjust your Drag values to get the level speed you want. There is nothing wrong with 205 MPH, but I just did not see it as being a simple consequence of an engine power increase. Adjusting the Drag once you have proper engine performance makes perfect sense.

On a different but related note, the altitude at which a particular power reading is achieved is very important because that is what will affect level speed. This is more important on supercharged aeroplanes which this one is not but there my be a slight Ram effect which means the engine puts out slightly more power or have a slightly higher critical altitude because of the dynamic pressure on the carburetor scoop opening due to forward speed.....

By the way, don't get me wrong here. The values you got are entirely reasonable and also as the author, you get to do pretty much what you want.

- Ivan.
 
Hello Ivan,
Well, well... not to worry. The misunderstanding was understandable then... Thanks!
As an author I can do what I want... but prefer to keep my adjustments within feasibly argumented lines and not just haphazardly applied!
So, I´ll just conduct another test, this time only increasing the torque a little, and leaving the friction at the old 8.0 value. At the moment Torque is at 0.65, and I´ll see what happens with a little more.
In theory, I don´t really want to change much else because effectively, the airframe and everything else is the same!
...as before... let´s see what happens now - It´s fun anyway!

Update:
-------
OK, I´ve just done it. The results are almost identical except for the slightly higher RPM, which would also seem more correct now, but with a more logical argumentation!

To use the previous report-template:
AT-9 Lycoming R680-9 (Engine Friction at 8.0, Torque at 0.65; Test flying at 500 ft)
RPM: 2289
Hp: 294
Vmax: 201.8 mph

AT-9A Lycoming R680-11 or -13 (Engine Friction at 8.0, Torque at 0.661; Test flying at 500 ft)
RPM: 2299-2300
Hp: 300
Vmax: 202.8 mph

I suppose that it would now be more fitting.
Also, this most probably also coincides with the reported increase RoC, but I haven´t tested that in depth yet. It is specified at 1162 fpm for the AT-9, and 1325 fpm for the AT-9A on Paul Matt´s drawings, so that should be OK too, but I´ll test it just in case.

Cheers,
Aleatorylamp
 
Hello Aleatorylamp,

I guess now is the time to drop the drag slightly to get your 205 MPH.... ;-)

In case you are wondering, I have not had a chance to look at or do anything with your AFX yet.
The night before last, the blower motor for the house Air Conditioner / Furnace stopped working.
The temperature where my development computer lives is normally about 5 degrees hotter than the rest of the house even when the AC is running. The rest of the house is 85-90 degrees at the moment so there really isn't a point in trying to start up and work on that computer. The Warhawk has taken a break for the same reason.

I did have a chance to install and check out your latest installation of the "CW-25".
My comments are the following:
1. The revised Nose to Windshield contours look very good.
2. The underside of the Fuselage also looks excellent.
3. The highlights you have on your paint job also look very good.
4. The animated Pilot's Head (Rudder) looks good. I was actually about to suggest doing that but you beat me to it.
5. There is a small hairline crack / sparkly on the underside of each wing immediately behind each Engine Nacelle.
6. The Propellers bleed slightly through the Wing Roots when viewed from the rear. Not sure how to fix that....
7. The Insignia Star doesn't look very good. I revised it slightly on my machines here.
(Don't need the Development machine to do it.)

I'll send you the revised textures if you want to use them.
Incidentally, it is a bit strange to have both Instructor and Student with identical mustaches....
Perhaps the Student should shave?
Neither Mustache would be acceptable in the modern US Military but I am not sure the same rules were in effect back in WW2.

- Ivan.
 
No hurry!

Hello Ivan,
No hurry for the SCASM processing - it´s just as well, as it gives some time to do final corrections, apart from allowing you to fix the climate-machine in your house (good luck!).

Thank you very much for your feedback!
Well, if you think it´s a good idea to get the AT-9A reaching 205 mph, I´ll go for it!
Update: With 0 Lift Drag at 75 instead of 77, there´s 205.3 mph flat out at 500 ft, so then that´s fine now. Incidentally, putting in the generic 2-engined control gauges, apparently the prop and mixture levers are never at 100% when starting, so that can be confusing.

Now for the AT-9:
- There´s not much I can do about the wingroot/prop bleedthrough seen from behind. The culprit is the family grouping of props in Nose left/right. It´s the same reason like for the tailplane/elevator bleedthrough seen from behind, as for minimum bleeds, the animated elevator has to be grouped in Tail left/right and can´t be inside the glue-sequence with the fin and tailplanes in Tail).
There´s another prop-blade/undecarriage-strut bleedthrough seen from the front, now that the props not a component. Maybe reversing the glue/blade order to favour the bottom blade will help.
- The underside hairline crack behind the engine nacelle should be no problem.
- I´d forgotten to mention the animated pilot´s head! I´d also thought of doing the other one with the ailerons, but perhaps that would be OVERdoing it a bit.
-It would be great if you could send the Star insignia, thanks a lot! I had a bit of bother with that - it was even worse before. I just noticed from Paul Matt´s comments: The Star was on all wing surfaces.
- I´ll shave both crew-members´mustachios off - it´s the same bitmap.

Then I noticed another "holy" part seen from below, under the tailplane, where one of the fin structures meets the fuselage. I´ll try to adjust that.

OK, there´s time to fix your "Klimaanlage" (German for AC-Heater) before I send the new AFX for SCASMing!
Cheers,
Aleatorylamp
 
Last edited:
Anlage.... I see that word a lot in manuals. ;-)

We had a technician in yesterday but he could not get the parts easily because he was not a dealer for this brand.

The really sad thing is that this is a top of the line Lennox "Signature" series furnace and it isn't even 6 years old yet.
I tracked down the original installers yesterday and a technician from their company should be here in a few minutes (in theory).
I figure the original installer should have no issues getting the parts,

The manufacturer told me yesterday that the major parts have a 10 year warranty so hopefully the labour for diagnosis and

... That was the technician(s)

Motor is bad. Now let's see of they can get the parts easily and without cost to me.

- Ivan.
 
Hi Ivan,

Hopefully it´ll be OK soon. The good thing is that it didn´t happen in the middle of a cold winter, and you´ll have a new motor for when the snow comes. Good luck with the warranty!

I just saw I´d run into confusion with the nosetip in the AT-9 AFX - I put the numberless nosetip from the AT-9A onto the AT-9, and it should have been numbered. That was because I´d been skiving... I had both models in one construction folder, with confusing stwitch-arounds for the different textures all the time. However, now I have intelligently got two properly separated construction folders, which I should have done ages ago.

Cheers
Aleatorylamp
 
Hello Aleatorylamp,

The furnace was replaced in December 2009 (the middle of Winter). The part has been ordered. It should arrive for installation tomorrow and I will be $350 poorer. (Part is under warranty. Labour is not.)
The dead motor actually was pretty close to new. These things should last decades.
Middle of Winter is a better time for a failure because people can wear more clothes or use small space heaters. Without Air Conditioning or a major air mover of some kind, it is much more difficult to keep cool.
Luckily, todays temperatures are lower.

As long as I am off-topic:
I received a strange call from a HVAC service company the day before yesterday. They claim to have done maintenance work on my furnace and offered us a deal to inspect the equipment for $50..
I told them that we were NOT a customer of theirs and never had been. They claimed to have replaced the igniter in our furnace back in 2012..... Hmmmmm....
The conversation did not end well.... for the telemarketer.

Are your AT-9 and AT-9A models that different? Visually, there should not be much difference.
It sounds like one model has a fore-aft texture on the Nose and one is a left-right texture. Is that correct?
I still have not tried to do anything with the Development computer yet.

- Ivan.
 
Hello Ivan,

I didn´t know it was getting so hot up north, but that´s the result of the wierd climatic goings-on we have nowadays. I wonder where they´re coming from...

This modern habit by modern, responsibility-skiving industrials of outsourcing everything to subsidiary services that at best use telemarketing agents, or worse, computerized robot voice programmes, is frustrating and offensive. They only want your money! It´s disgusting and proposterous. When you buy the stuff in the first place, they don´t tell you anything, and you don´t ask, as the whole concept is so far-fetched, that it doesn´t even cross your mind.

Anyway, the AT-9 Jeep:
I got rid of the gap at the fin-base by putting a lid on the main fin component (that was better than re-shaping the tail-cone structure), and straightened out the panel that was bent on the under-wing at the nacelle. Also, I got rid of the hairline crack behind that, which was due to two panels meeting a third one on a slant without enough overlap.

Now parts count is at 149.6% and 149.9% for the AT-9 and AT-9A respectively. I could always eliminate all the lights, gaining 6 and 10 parts respectively, but that won´t be necessary anymore.

Then I returned to the nose-tip with a front/back texture to put on the red passing light, and also shaved off the crew´s moustaches, and put in the trim-tabs on ailerons, rudder and elevator, so it´s looking even better now.

Well then, as soon as you tell me that you´ve got your AC motor sorted out, I´ll send you the AT-9 AFX again for SCASMing. Then with that, I can identify the different sections to perhaps re-label them on the AT-9A SCASM list to run that process myself, for learning practice.

Cheers,
Aleatorylamp
 
Hello Aleatorylamp,

If you think the project is ready, send it. I will get to it when I can.
Hopefully the equipment will be repaired today.

- Ivan.
 
Hello Ivan,
Let´s hope all goes well with your Klimaanlage today!
Very well, then I´ll send the AT-9 AFX as soon as I´m done.
Thanks very much indeed!
Cheers,
Aleatorylamp
 
Well, the motor was installed. The installation took a bit longer than expected but everything seemed to work....

....a couple hours later, with the house nice and cool, we noticed a pool of water on the floor with more dripping from the furnace.
It turns out the bumping and jarring of the furnace must have loosened up some rust which blocked a vent line from the AC coils.
In about 30 minutes, once I figured out what was happening, I cleared out the blocked vent with a zip tie fished into the vent and got out a fair amount of rust. It makes me wonder what is rusting so badly inside though.

Received your email. I will try to address some of it tonight.

- Ivan.
 
Hi Ivan,
So they changed the motor without checking anything else. Would there be a connection between motor´s short life and the rust, which may have been causing excess wear? I remember we got a new fridge about 20 years ago, and the motor only lasted three years instead of at least 15 because it was constantly being overworked - a faulty thermostat hardly allowed it to stop and it overheated and burnt out.
No hurry with the Jeep!
Cheers,
Aleatorylamp
 
Hello Aleatorylamp,

You now have the MDL and the SCX files I was working with.
Let me know if something is still broken.

One thing worth noting is that your Tachometers are inaccurate. That is why I was working on the Gauge Development for the Mitchell and Lightning.
You also do not have Magneto and Starter for Engine 2.

Regarding the motor, the technicians were responsible for the Furnace, not the Air Conditioner.
Both items were running when they left.
It just took a little while for the Drip Tray to fill up. It is amazing, I figure this machine condenses about a liter of water every 5 minutes or so.

It really wasn't their problem and something I would not have been looking for unless there was a problem.... which did turn up of course.

The dead Motor actually looked new. Not a mark on it. The interior of the Furnace looked quite new as well.
After talking to the technician for a while, I suspect the big issue is that this type of electronically controlled Motor isn't very tolerant of power outages and we tend to get a lot of little power hits.

Oh well.
- Ivan.
 
faulty gauges

Hello Ivan,
Yes, that´s the problem with the FSFS twin-engined gauges - inaccurate readout and lack of engine-2 magneto. Such is life...
However, I think I can manage to edit the bitmap with a gauge-bitmap programme I have here. It should be no big deal because I could calibrate it with the Beckwith gauge. As for the second magneto, that´s another kettle of fish!
Thank you for sending the new files for the Fledgeling. I´ll install them and post a reply.
Hopefully the weather machine in your home will be OK then!
Cheers,
Aleatorylamp
 
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