Conspicuous by Their Absence

Big wooden propellers

Hi Ivan,

I was already very satisfied with the Giant´s performance with the 8ft propeller.
The only specification I have as to the rate of climb is as follows:
Climb to 3,000 m. (9,840 ft.): 43 min - that would make it 229 fpm (average).
Ceiling: 4,320 m. (14,170 ft.).

Possibly at altitudes lower than 4300 ft the climb rate would be quite low, maybe 100-150? and higher up perhaps 240?

At the moment, with the 8ft propeller, the Giant seems to settle for 106-114 fpm at low altitude (600 ft), and at 5000 ft it´s about 135-145 fpm. It could be a little on the low side, I presume.
The one who wrote the FS98 .air file set it up as: Climb is at about 215 ft/min at 53 kts.

I´ll install the new propeller and study your post again, and see what seems best. It looks even more satisfying though, I must say!

Thanks and cheers for now,
Aleatorylamp
 
Climb Performance

The Climb Performance is only going to get a LOT worse with the new 14 foot propellers.
First enable the autopilot if you haven't already. Send me your current AIR file. I might be able to help tune a few things as long as you are otherwise satisfied with the handling.

I am guessing with your time to altitude that your initial climb is going to be closer to 300 or 350 feet per minute or maybe even higher considering that power will drop off at altitude with an un supercharged engine.

I take it we are still going for 225 HP at Sea Level and 267 HP at 4300 feet with a maximum speed of 84 mph at 4300 feet?
I presume service ceiling is 100 feet per minute?

This is the part I really hate because it involves sitting there with a stopwatch.

- Ivan.
 
Rate of climb and performance specs

Hi Ivan,
An interesting path is never free of obstacles, thus allowing a tea-break -- this just occurred to me now, it´s not a proverb...

Regarding the general 4300 ft specs, I´d say yes, 225 hp low down and 276 hp at rated altitude.
You are of course right about the climb rate being much higher initially, and lower later. My mistake, sorry!
Anyway, I finally found what I was looking all along about the rate of climb specs, although they are for both engines that were used (BMW Maybach MbIVa rated at 8200 ft with 245 hp and "our" Mercedes DIVa):

- Max. speed: 135 km/h (84 mph; 73 kn)
- Range: 800 km (497 mi; 432 nmi)
- Endurance: 7-10 hours
- Service ceiling: 4,320 m (14,173 ft)
- Rate of climb: 1.67 m/s (329 ft/min) - that presumably would be initially
- Time to altitude: :*10 min to 1,000 m (3,281 ft) - that would be 328 fpm.
23 min to 2,000 m (6,562 ft) - that would be 252 fpm for the next 1000 m.
43 min to 3,000 m (9,843 ft) - that would be 164 fpm for this next stretch.
2 hr 26 min to 4,320 m (14,173 ft) - here the average goes way down to 16 fpm, and I suppose that 100 fpm would be at around 11000 ft maybe.

The reason we are using Mercedes engines is that both livery (conspicuous colour splinter lozenge) and the twin fin tail (not 3 fins) configuration corresponds only to the 7 Schütte Lanz built units which used Mercedes engines.
I hope this helps...
Cheers,
Aleatorylamp
 
Last edited:
Climb Rates

The correct power is 267 HP, not 276 HP, Right?
Also, is the climb rate with or without bomb load?
What is the flying weight for these tests?

If you send me your Giant Aeroplane again, I will see if I can improve the climb rate a bit.

- Ivan.
 
flying Weights for the Giant

hi Ivan,

From what I can gather, the climb rate is for standard bomb load of 2200 lb (allowing 568 USG fuel)

MTOW: 25200 lb

17600 ; empty weight ready for service including engine coolant etc
1400 ;crew including flying clothing
480 ;6 machine guns and ammo
2200 ;normal bombload which allows for 586 USG fuel.

total 21680 lb. dry weight for a standard load.

(max authorised bombload 2000Kg = 4400lbs allowing 220 USG fuel)
(max payload = 6280lbs)
(zero fuel weight with max payload= 23,880lb)

I put in 22000 for dry weight, which could perhaps be reduced to 21680 lb - in fact, it´s probably a good idea to do so!
Cheers,
Aleatorylamp
 
CFS versus FS98 Weights

Hello Aleatorylamp,

Combat Flight Simulator works a bit differently that Flight Simulator 98 in that the Gun Ammunition and Bomb Load Weights are specified in the DP file. Also, when selecting the aircraft, you can change the default bomb and ammunition loads.
For defaults, I typically use full Gun Ammunition and Zero Bomb Load with the expectation that the Aircraft Commander (Player) will select the appropriate load for the mission.

You can of course select a maximum bomb load and only partial fuel to stay under MTOW.

[ Ivan.
 
weights

Hi Ivan,
Thank you very much for your clarification - I was completely under a different impression.
So in the .air file, what has to be placed in the dry weight would be:
17600 lb empty weight ready for service including engine coolant etc
1400 lb crew including flying clothing
-----------
19000 lb total
-----------
OK, so then the Dp files then take care of the rest. I took the Dp files that someone had written for the Gotha bombers some years back, and carefully adjusted all the damage boxes and gun positions. I hadn´t expected that these files would also define the different payloads. Come to think of it... I wonder what´s in the payloads of all the other planes I´ve uploaded.

I´ve just looked - there´s no payload at all defined in any of them. If I understand correctly, (correct me if I´m wrong) this would then mean that the player can define what he/she deems necessary. I hope it doesn´t mean that the plane is useless for carrying anything!

Cheers,
Aleatorylamp
 
Prop efficiency Table 511 adjustments

Hi Ivan,

I just noticed my dislexic Hp quote... yes, 267 hp, not 276! That took a while too...

On the new 14ft prop with the new Torque parameters you set up, I´ve been working with the Prop Efficiency Table. I incremented the 0.2, 0.4 and 0.6 AR parameters by 0.05 a time, and I´m happy to say that this quite soon started giving significant performance improvements, upto a point where speed is now being maintained during a more normal rate of climb. At the moment it´s at .5 .7 and .95, and I´ll start balancing it with Drag now. It´s looking very much better!

Thanks for your on-going help and suggestions!
Cheers,
Aleatorylamp
 
Maximum Efficiency

Hello Aleatorylamp,

You might need to back off a bit with the Propeller Efficiency entries.
Propellers back in the days of the Great War were not particularly efficient.
Even during WW2 and today, a really good Propeller wont get much higher than 85% efficiency at best and then only in a VERY narrow optimum operating range. Typically this would be at Cruising speeds.
I don't believe that 14 foot piece of timber would ever exceed 75% efficiency and I doubt it woul really get that high considering the very low advance ratios it would be operating in.

Also, you are really trying to boost the mid range thrust for climbing instead of thrust at maximum level speed.

- Ivan.
 
75% efficiency, and weight again

Hi, Ivan!
Yes, thanks - I did notice it was too much! I only mentioned it as it was suddenly getting much better: The plane got off the ground correctly at 48 kt, the rate of climb was starting to be maintained instead of falling back down, and 4300 ft performance was also improving - finally too much, as you have already deduced, so now I´m finding the optimal point in order to then adjust the Zero Lift Drag like you said. To understand the existence of a 100% point somewhere in the numbers, however, is a bit too abstract for me, so I have to go by trial and error.

But wait, weight!! Before I do it, however, there´s the flying weight question again, regarding the Dp files:
The ones I´m using include no payload - they were written by someone else some time ago and I hadn´t a clue. I only corrected the damage boxes and gun positions. Do such Dp files need payload being included in the .air file or not? Once the payload is taken out of the .air file - dry weight going down from 21680 to 19000 for the Giant, for a mission then, simmers could put in their own, I gather. But what happens when I test the plane in free flight? Would it be empty? Where is the standard 2200 lb bombload I need to test it properly?

It´s great to have someone coaching me along as things progress - in fact it would be impossible to do otherwise!
Cheers,
Aleatorylamp
 
more moderate Propeller Efficiency

Hi Ivan,
In order to illustrate the logic behind my higher AR settings, here are more detailed results of my Table 511 trials - dry weight at 21680 lb in the .air file (payload included), and without Dp files. (A cook says:"In case of doubt, throw it out!"). I deduce from your comment, that the values in the AR tables are percentages, and I suppose .8 would be the maximum to put in.
Different settings for AR=0.2, 0.4 and 0.6 positions.

Values .3, .65 and .8 - No useable rate of climb.
----------------------------------------------
Sea level: Rotation OK at 48 kt, level flight Speed OK.
4300 ft: 1439 rpm , 263 hp. Level flight speed OK.
BUT: can´t maintain even a very low rate of climb.

Values .4, .7, AND .8 - Low rate of climb, still no good!
----------------------------------------------------
Sea level: 1280 rpm, 221 hp.
Climb: 87 fpm at 53 kt

4300 ft: 1436 rpm, 264 hp
Climb: 128 fpm at 56 kt
BUT: Level flight 86kt - too fast.

Values .5, .75, and .8: Better rate of climb, but still not good enough.
------------------------------------------------------------------
Sea level: 1284 rpm, 216 Hp
Rotation at 45-46 kt.
Initial climb: 164 fpm at 50-57 kt
Later: 1309 rpm, 225 hp,
175-190 fpm at 54-55 kt.
BUT: Level flight too fast at 84 kt

4300 ft:
Climb: 260 fpm with 1418 rpm, 259 Hp at 57 kt TAS
Level flight: 1439 rpm, 264 Hp. 91 Kt - MUCH too fast and would obviously need Zero lift Drag regulation.

Incidentally, none of the Autopilot gauges I have work in FCS1 even though activated in the FD, but that doesn´t really matter, so I use manual trim.

Cheers,
Aleatorylamp
 
Last edited:
Zero Fuel Weight

Hello Aleatorylamp

Here is a thread worth browsing that might give some detail as to how I calculate the Zero Fuel Weight that I use in the AIR file:
http://www.sim-outhouse.com/sohforums/showthread.php?84748-Focke-Wulf-190A-Revisited

Posts 5 and 7 are probably the most relevant.
I suspect you will be able to better on some of the reference material than I was. My German is mediocre at best.

The Zero Fuel Weight in CFS is a "Normal Loaded Weight" but with
Empty Fuel Tanks - No Explanation Necessary
No Bomb Load - Obviously
Gun Ammunition Fired Off - On some aircraft, ammunition weight includes drums and / or boxes. The only weight removed from our total is just the cartridges and links if guns use a disintegrating link belt.
On a Mitsubishi Type Zero, the Wing Cannon in the beginning used a 60 round or 100 round drum. The weight of the drum has to be added to the Zero Fuel Weight because when the ammunition is expended, the drum remains on the aeroplane. The Messerschmitt 109E has the same situation.
The guns are obviously also not discarded when empty either.
The numbers from the stock DP files are pretty wrong because they only account for the weight of the PROJECTILE.

For your DP file, you will need to find out how many rounds of ammunition are carried on your Giant Aeroplane.
I use 1.12 Ounces (Weight Unit in DP Files) for a single round and link for a 7.92 mm x 57 gun. I still have a few rounds of 7.92 ammunition in the basement, but they are not likely to be the same configuration as the German ammunition.

As for default ammunition loads, I typically set full gun ammunition as default and zero bombs.
Some sources (such as US Navy manuals) list only partial fuel and partial ammunition loads for their "Fighter" configuration. As another example, the default ammunition load is 250 rounds per .50 caliber MG on the P-38 even though the full load is 500 rounds per gun. My DP file completely ignores that partial ammunition load.
My crew chiefs have been taught to load full gun ammunition on all missions and even on ferry flights unless specifically ordered not to.

If your maximum bomb load is 1000 kg, a reasonable choice would be to use 100 kg or 250 kg bombs. You want to be able to select full bomb load as well as partial if the mission calls for more fuel.
DP Files don't have much flexibility, so sometimes you have to make a choice as to where to set the limit. My B-25 Mitchell is not able to carry the full load of ordnance the real aircraft did because it doesn't bother with some of the under wing bomb racks. My B-26 Marauder will also not allow the use of the AFT Bomb Bay because in service those were almost never used. To simulate the weight of a 1000 pound bomb carried by the SBD Dauntless on attack missions, mine has to carry two 500 pounders because otherwise loading the single 500 pounder for scouting missions would not be possible.

**********
 
Test Weight

I believe that just because you don't have a DP doesn't mean you are not carrying around ammunition. The default DP file is used in that case and it has 2 x 20 mm cannon and 4 x .303 cal MGs.

For a service ceiling test, I typically use 50% Fuel + about 15 gallons and full ammunition. The extra fuel is so that the ceiling is reached with just a bit over 50% fuel. If the fuel runs slightly lower, I don't worry about it, but the remaining fuel quantity is always noted in the test record so I can better reproduce it if I need to.

As for your test weight for the Giant Zeppelin, use whatever the weight specified in your reference says. Just keep in mind that they probably didn't use full power during the time to height test.
Most likely is "Climb Power" (Surprise!) or the 30 minute rating I described earlier.

Don't be too concerned if you arrive at numbers a bit higher than the documentation. I also was a bit surprised when I was reading about the flight testing of a B-26 Marauder. The quoted "Maximum Speed" was done at "Military Power" which was a couple hundred HP under what the aircraft REALLY had available.

If you are still having issues with take-off and climb, send me your AIR file. There are a few things that might help though if I post them here, folks might think I was a total idiot. If they work, I will tell you what I did.

- Ivan.
 
Test loads and performance

Hi Ivan,
Your good advice is giving very much better results with my performance testing on the Giant, to determine the best setting for Propeller Efficiency. I got the standard bomb load and the correct full ammo weights into the Dp files, and adjusted the dry weight in the .air file.
Your suggested 50% fuel tankage could perhaps be good not only for ceiling tests, but also for rate-of climb tests, so for the moment I´m trying it with that.
The results now are more meaningful, and I have done tests with an all-round 75% prop efficiency, to establish how much the Zero Lift Drag needs adjusting - It had to be doubled for the moment. As the rate of climb was also too high, especially at and just above the rated altitude, I´m (obviously) reducing prop efficiency, which seems to require more reduction for the AR 0.6 and 0.4 values than for the AR 0.2 values.
Anyway, it´s going rather well, I´d say. Thanks again!
Cheers,
Aleatorylamp
 
Advance Ratios

Hello Aleatorylamp,

Please go back to post #980.
Note that the Giant should never exceed AR of 0.4 in level flight and is more likely to be around 0.25 in a climb.
That is why only the 0.0, 0.2 and 0.4 entries were tuned in Record 512 in the AIR file I sent you.
The same entries in Record 511 are all that are really important as well.
You might want to adjust the other entries to make a smooth transition, but it isn't absolutely essential because your aeroplane won't be seeing 138 mph TAS much if at all.

Glad you are having fun!
- Ivan.
 
Hi Ivan,
Ooops! Thanks for pointing this out - Sorry! I had automatically ignored the 0.0 AR, thinking that the 3 significant AR´s were 0.2, 0.4 and 0.6. I did however realize that 0.6 was out of engine range, but thought it would maybe "pull up" a possible ficticious 0.5 in-between value. ...which it doesn´t, OK!
No harm done yet anyway! I´m just finishing the fuel and payload weight adjustments before doing any more testing, and figuring out the best range-payload combination as well as the best practical flying weight for simming purposes.
An all-up loaded too-heavy plane would not be much fun to fly, and fun is an important criteria to go by.
Yes, it is fun indeed, thanks! I see you are enjoying this "investigation" too.
Cheers,
Aleatorylamp
 
Hello Aleatorylamp,

Actually increasing AR 0.6 to try to affect the in-between AR 0.5 value is a workable idea, but the problem is that
Advance Ratio 0.5 is 115 MPH True Air Speed, and your Giant will probably not see it much.

Perhaps I am over simplifying.
Your Giant MAY see Advance Ratios higher than 0.4 but if it does, the visits will be very transient and encountered at very low RPM such as at Take-Off or Landing. At full engine RPM and level flight, the Giant should not even see AR 0.4 which is 92 mph, but it might come close.

- Ivan.
 
Tables 511 and 512

Hi Ivan,
OK, I see... or rather, I almost do! It is admirable how you have dedicated so much time in deciphering exactly which positions on these tables affect the low-rpm, low-power huge-propeller powerplants of the Zeppelin Staaken R.VI , and have had the pacience to make them undestandable enough for me to use, even though I still can´t visualize exactly how they work.
I´d say it would take an aeronautical engineer to understand them!

This will not only make it possible to upload the Giant, but will serve for a new CFS1 .air file for the AEG G.IV that I uploaded a few weeks back with FS98 FD, and also for the future Gotha G.IV I´m planning to upload after the Giant, as these two planes also had these engines. Then, it will also be the basis for a future variant of the Giant, which had similar but better BMW engines, the Maybach MbIVa, altitude rated for 245 Hp at 8200 ft. It was slower lower down, but faster higher up at the usual operating altitudes.

Thanks to this, flight tests with the Staaken R.VI have been quite satisfactory, and I am now making further adjustments, which I hope to report on quite soon!

Cheers,
Aleatorylamp
 
Aeronautical Achemy.

Hello Aleatorylamp.

I am only just beginning to Visualise the inter relationships myself. I had almost gotten this far with earlier spreadsheets before my laptop computer died. I am actually getting better results with the current spreadsheet because The earlier one had some kind of formula error I still cannot figure out.

Tonight I started working on the actual problem that had me interested in the Propeller Tables and found that I need to create a couple more spreadsheets to poke around at Engine Power and Constant Speed Propellers. There are at least 4 projects that could use some tuning in this area.

Don't be concerned about needing to be an aeronautical engineer to understand this stuff. I most certainly am not one myself. Then again, there is always the question of whether or not my explanations and recommendations are correct or not....
My original goal was to have enough of a working understanding to be able to tune these tables to produce the effect I want and I seem to have reached that goal at least.

Typing this on an iPad is tough!
- Ivan.
 
Testing the Giant

Hi Ivan,

Well, after further adjustments and some ups and downs, performance seems to be quite well balanced out now, fitting into the Giant´s specifications quite nicely. I´ll do some timed climbing tests now, as a final trial and let you know before uploading.
Thanks again for all your help and guidance, and I´m glad this has also been interesting for you!

A question on Dp files: It seems that after specifying a maximum payload in DpEdit, although I set the default payload to e.g. half, this is ignored by CFS1 and it´s empty. Maybe this is normal and the plane has to be loaded every time you fly?

Edited update: I´ve just found the Help file for DpEdit, and the .ini file was set for CFS2. Set correctly for CFS1, it also seems to ignore the specified default value, but sets maximum load initially instead of zero. Once regulated for what the user wants to fly with, CFS1 keeps the setting until altered again. I´ll tweak my propeller efficiency again, as tests so far were all with zero bombs instead of the 80% standard load I wanted, but that should be no problem!
Live and learn! Never a dull moment...

Cheers,
Aleatorylamp
 
Last edited:
You must log in or register to reply here.
Back
Top