I''m openning this topic to collect all flight model feedback in one place, and make the FM discussion more productive.

1. Thank you all for input. If you'll find a consensus we can do whatever it is: less power/more power etc. But if we are talking some FM realism here let's wait for feedback from atleast 2-3 real B-52 pilots. After that we'd adjust some things.

2. Please note, part of the B-52 flight model comes from .air file, regardless of aircraft.cfg values. Some of these numbers mean nothing.

3. Also please note some FM characteristics are interconnected, cutting low level performance you'll damage altitude ones.  

4. Believe us FSX flight model is not about finding real B-52 numbers in wikipedia and putting them somewhere, it's way more complicated unfortunately.  

No big problem here, I roughly altered the thrust value which was stated as "rough" because I don't have an insight on the drag components on this bird (and those would be the ones to look at for a "fine" solution").

No big deal, talking about a fun product here but if CS goes for some changes in 1.1, I suggest to leave the thrust value were it is and go for some more drag to avoid those 500 knots climb phases.

Another one could be the rollout phase of the automated flight were the commanded heading is established fairly late because the (in my eyes) too soon reduction of the roll rate.

My 2 Cents:

I’ve been poking around in the air file with airwrench, and comparing the acft.cfg files. I’m a Flight Engineer by trade and have 5,000 hours flying USAF aircraft. I’m not a BUFF guy, but I slept at a Holiday Inn Express last night so this should be easy.

Conceptually, the mighty BUFF was created as a high altitude, long range, nuclear bomber. It performed admirably at this, but as the world changed, so did BUFFs missions. Over the last 50+ years it has been used (just to list a few) as a low altitude conventional penetrator, high and low altitude cruise missile delivery platform, and mainstay of the Manned Strategic Bomber portion of the (MSB) Single Integrated Operation Plan (SIOP). What do all of these roles have to do with the choice of high or low altitude performance? They all start out at high altitude, and the transition to the low altitude mission profile. I.E., A B-52C departs after a Klaxon en route on the assigned mission profile. They take off, climb, and maintain high altitude for the entire sortie. A B-52C departs after a Klaxon en route on the assigned mission profile. They take off, climb, and maintain high altitude up to the IP, then they descend to low level for mission execution, climbing back to high altitude for the trip home. Substitute a B-52H and these two scenarios are the same profiles flown today. In both cases, it’s the high altitude, not the low altitude that drove performance. The low altitude portion is simply considered a performance penalty similar to flying with a landing gear down, and the tanker schedule is adjusted as necessary.

Most simmers seem to fly high altitude long range as an MO. I have tried a few low-level routes with the CS B-52, and it is possible. The new radar works well but requires some creative interpretation to figure peaks and ranges. I still haven’t taken it to the Grand Canyon yet…

Wheeeew, ok, after that diatribe here is what I can see from a quick skim of the .cfg and.air currently supplied. All external numbers quoted are from 1B-52H-1 5DEC1982, and 1B-52H-1-1, 1JUN2006.

I have done a little bit of testing so far, here is what I have:

Takeoff Trials:
Computed: EPR=1.745, S1=125, S2=162, S2 Distance=7300 ft Minimum Runway Available= 8400ft, 18 Seconds from 70KIAS too S1 @ KJFK 22L (8400Ft):

Attempt 1: Abort at S1 (Using 1.74 EPR indicated)= Data Invalid. 1.74 EPR is 65% N2, basically flight idle.

Attempt 2: Abort at S1 (Artificially using 1.85 EPR, maximum for 25F)=Data Invalid, never reached 125 before running out of runway.

Attempt 3: Abort at S1 (Artificially using full throttle)= Data Invalid, Acellerated to S1, (125), aborted using idle thrust, drag chute, full spoilers and brakes. Departed runway at 70Knots.

Attempt 4: Abort at S1 (Artificially using full throttle)= Data Invalid, Accelerated to S1, (125), aborted using idle thrust, no drag chute, full spoilers and brakes. Departed runway at 55Knots. (Apparently the drag chute is only for show)

Attempt 5: 70Kt to S1 timing (Artificially using full throttle)=Data Indeterminate, time= 13 seconds, 5 seconds faster than predicted.

Attempt 6: 70Kt to S1 timing (Artificially using full throttle)=Data Indeterminate, time= 14 seconds, 4 seconds faster than predicted.

Attempt 7: S2 7300 foot unstick point (Artificially using full throttle)=Data Valid, unstick and liftoff occurred at about 7300 ft, albeit in a nose up attitude

I have yet to get the flaps in starting at 180Kts, and full up by 200. You have to almost go to idle after gear retract to keep from over speeding the flaps.

I have not done any climb, cruise or fuel trials yet.

Thrust:
Both in .air and .cfg, 30,000 lbs per pod is almost perfect. Charted thrust for the TF-33-P-3 (JT-3D) at standard day (Sea Level, 15C, 29.92) is 14,550lbs / engine, which is 29,100lbs/pod. 900lbs of thrust per pod X4 pods is a net difference of 3600 lbs of thrust, not enough to keep us over speeding so consistently. The absolute thrust could be tweaked a little, but that’s not the root. However; Takeoff EPR at KEDW (My preferred test base) was computed at 1.82, that setting was reached with the throttles at 12 o’clock (about ½ travel); from there until full throttle a maximum of 2.0 EPR was reached. There is an issue with the scalar (not the .cfg, the .air) somewhere that needs to be tweaked.

Drag:
I suspect that this may be a factor in the “over performance” but nothing jumped out at me from a quick scan, other than default values for tuning etc.

Weight:
A minor tweak, crew members should be 270lbs, not 170. Don’t forget all of the ancillary equipment that goes with each crew member. Heck, I weigh more than 170 nekked, and I’m in shape according to the USAF fitness regs. The current acft.cfg doesn’t allow for any weapons load. I would like to see stations for weapons added. The BUFF can only carry a full fuel load with no weapons. This was the result of the concept of carrying 1 or 2 nukes weighing a couple of thousand pounds each. When you pack on 70,000lbs of old fashioned iron headache, you must reduce the fuel load to compensate. This was a part of every B-52 mission planning phase, determining fuel loads, tanker points etc. How does this affect performance? See the next section, balance.

Balance:
The nose down climbing attitude of the B-52 is a well-established characteristic.  FSX is reporting a full-load CG of about  30% MAC, which is within limits of 22.9-35% MAC. Airwrench is reporting a 50.57% MAC for the same conditions. The visual model is performing as if it has a 50% MAC CG. The fuel tanks are currently not located realistically. I assume this is to keep it easy to fly; by locating the centroids so close together you essentially can’t run the CG out of limits. I am willing to bet the takeoff attitude will be corrected with a CG adjustment.

In light of this, here is my vote:

Make two .cfg and .air files available. Why?

The mighty and venerable BUFF is a handful when operated realistically, it requires a crew, much more so than a 777 or A340. Therefore, to keep a “Fun” model available the master set should be left alone, so that folks who don’t want to worry about fuel sequence and CG, wing flutter and bingo fuel prior to AR can fly a masterfully created model and enjoy it.

The second set should be added as a separate .cfg and .air for the realism craving airplane geeks like myself. I think it is safe to say that most of the enthusiasts out there would have no trouble swapping these two files.

--Dan

Very good post, HvyEng.

I just like to add that you must forget all EPR values on FSX engine model planes, they will never get accurate and all available payware birds using them suffer from this lack of accuracy.

The only accurate addons are the ones which use their very own engine model, not just some FSX altered values for the generic "jet engine" there.
You will be too low powered if you use those readings in FSX on the standard models. N1 comes closer to somehow realistic data but this still isn't a thing which can be called accurate.
I don't blame CS planes here. As said, most of nowadays addon planes go standard FSX there but you can check any other CS plane you own to see that even the 767 and 757 don't develop normal (realitstic) readings related to the actual thrust available.

I think that the drag tuning and maybe some CG one too can give this B-52 a more realistic feel but all things further than this will be too much for a fun and low priced product in my eyes.

Even on the more detailed models a development of a special engine model is to question as surely a big amount of users just "throttle up" at takeoff.
I would applaud to it though but I know that there is quite some development necessary to achieve that just some users ever recognize the change while others might struggle then.

One can recognize this standard engine model on his planes by manually starting the engines.
If they go "bam" and are running, you surely use the generic jet engine here.
A real engine spools up slowly and loses it's EGT over quite some time when shut down. Our current ones here and on most payware stuff do this in seconds.
So be aware of the limitations and expect some effort on more effective fileds of tuning. Drag and CG were mentioned and I think you have quite some expertise to help there.  

So while we expect this addon to become more realistic, we have to stay like this too and don't expect huge development efforts on lower priced products.
I appreciate the thread opening from the Captain Sim side, so there is some interest in enhancing the fun experience it seems.

Would you please share your cfg changes.

Thanks

Russ

RIPPDOFF wrote on Dec 15^th, 2010 at 10:41pm:

That's normal, the F-16 only has one engine, they hate us for the seven others.  

Great offer there, HvyEng.

Seems like you are really getting on this. Maybe the "Driver" is followed by a "Captain" product then, would be nice to see.

Looking at the first video, I'd say that we definitely need more smoke.  
Funny thing to see that this vid is old, nowadays two guys getting that close to such smoke exhausts would sue the company and the pilots while those two seem to enjoy the hot stuff.  

I've used the suggested fuel_flow_scalar   = 1.66 value from HvyEng on my last flight from Melbourne to Christchurch and must say that the fuel consumption now looks a lot better.

But the "Total Fuel Flow Indicator" doesn't represent the individual values of the engines, with or without the tweaked value.
It reads 17.000 while e. g. the individual gauges show around 24.000.

Interesting findings, Lost in Isaan.
I think we could use some charts to compare the fuel burn to the sim values.
I was at a FL490 cruise with 0.85 and had around 21.00lbs/hr on the individual gauges while the sum up gauge showed 17.000 or so. I have no idea if this is close to real, but at least it's far away from the too economic flying with 0.60. Would be interesting to find out which fuel burn rate is closer to the real values there to pinpoint the faulty gauge.

I think if CS alters the fuel burn and the drag curve at lower altitudes, this fun thing will be as realistic as it could be for the placement in the market and the very nice price.

I don't know if the relationship can be described that easy, Mark. But you right, the edited fuel flow might have to be edited again if CS increases the drag component.

My problem isn't the overall speed of the bird (it's a powerful one, no doubt) but the too fast acceleration after TO and with gear and flaps going up.
Normally, setting climb thrust and pitching the plane up will establish ATC approved speeds but on this one, it all happens too fast from e. g. 180 knots to 300.
I can't remember any B-52 videos where the engines where throttled back that much together with a need to pitch up by such huge amounts.

So an increased drag should hold back this fighter like acceleration tendency in the sim, not more, not less.
The later climb phases look good to me, the initial 10.000ft are the problem in my eyes.

No bank issue here but I'll try that fuel flow value, thanks.

So is there any verdict?

I assume everyone went with TurboFanDude's mod file and settled with that.

I've just started flying this bird and find it like a rocket. I'm overspeeding and ruining flaps in just a few seconds after leaving the ground for pete's sake.