FS-KBT P-3 runaway

[SSI01]

A recent post about problems with adjusting a recip-engine aircraft's power-idle settings got me to thinking about a problem I've experienced with one of my turbo-props. The FS-KBT P-3 is a fine aircraft, its' only problem is the absolute charge it does in my FS9 down the taxiway at 60 or 70 knots even with the throttle pulled all the way back. Using the "Groundhandling" add-on and setting the taxiing speed to 10 kts results in a series of head-bows until arriving at the EOR. After seeing the other post, I ventured into the aircraft cfg file's [propeller] section. I've set the beta_min (hopefully, that's what I'm supposed to adjust) as low as 6.000 but still experience the nodding. There isn't a condition lever setup on the panel I have, just thrust levers. I can fine-adjust pitch using ctrl-F2/F3, it does slow things down a slight amount, but only by a few kts. The only seeming fix I've found, in conjunction with the Groundhandling add-on, is to turn on the deicing switch on the panel, which brings things down speed-wise but results in a higher power setting to taxi.

[pfflyers]

I got this "fix" from another FS forum; it seems to work for me.

I set "beta_min=8.0" and "minimum_on_ground_beta=-0.2"

With these settings my P-3 is as docile as a C150 on the taxiway and still seems to fly ok.

PF

[SSI01]

Thanks, pf. Those settings are in fact the default for my aircraft. It's nodding furiously due to constant intermittent brake apps while taxiing. I've got it running on the sim as I write this. If I hit ctrl-F1, I can taxi using Groundhandling set at 3kts but we're bouncing up and down at the nose. The crew must be getting awfully sick! Guess we'll just have to live with it.

[Navtech]

Same problem here ....
Stop two engines can help :)

[SSI01]

I even tried recalibrating my joystick, figuring maybe the throttle slider was telling the sim it was at 25% power, or some other setting, when it was in fact back against the "idle" stop. No soap - even after recalibration the bird still gallops down the taxiway.

Interestingly - the Groundhandling gauge is set at "3" for taxi speed, yet the aircraft taxis at "8".

FS-KBT, if you somehow review these posts - can you take a look at this please?

[p3aewguy]

I have been adjusting the aircraft config on this for a little while. One thing that's way off is the fuel quantities and the weight. The outboard tanks hold 10,000 lbs each and the inboards 11,500 lbs on the real a/c. The center tank holds 16,000 lbs. A normal training flight would have a fuel load of 28,000 lbs. A long range transit flight would have up to 55,000 lbs. The max gross weight is around 132,000 lbs. empty weight is around 62,000 lbs. If there's interest I could post the relevant config entries.

Dave
P3aewguy

[Navtech]

If there's interest I could post the relevant config entries.

Yes .. post them ... but I have a doubt that this will solve the taxi speed ... :running:

[SSI01]

p3, I'd be very interested indeed in those correct weights. I'd like to join the chorus asking you to post the updated config file fuel cell figures and weights. The info you've provided re: what fuel load for what purpose is also valuable. I would include that as a note in my aircraft folder for reference purposes, depending on what kind of flight I have planned. I have heard P-3s, after they arrive on station and begin their patrol patterns, can and do sometimes shut off two engines to reduce fuel consumption and loiter on the other two fans for a while. If this does in fact occur, which ones do they shut down and does that change the fuel draw sequence - which tanks are emptied first?

[Navtech]

can and do sometimes shut off two engines to reduce fuel consumption and loiter on the other two fans for a while. If this does in fact occur, which ones do they shut down and does that change the fuel draw sequence - which tanks are emptied first?

From memory ... it's a very special operation and the economy of consumption is near to nil
This operation follow a strict protocol .. about speed .. altitude .. when the 2 engines must be stopped and restarted
Some searches on the internet will be a + for know the exact sequence ....
Some infos:
http://www.pprune.org/archive/index.php/t-536998.html

[SSI01]

navtech, p3, et al - p3, I took your fuel weight numbers and plugged them in to the KBT P-3's config file. Next thing was to reset the two values - beta_min and minimum_on_ground_beta, as suggested in an earlier post - went to the sim, started the bird - and it doesn't charge down the taxiway any more!! It takes a bit of a prod to get it moving at 100% fuel load, as would be expected. Once moving, adjusting the pitch as suggested by Milton to "ground fine" using ctrl-F2/F3 and a bit of juggling results in a taxi of about 6-7mph at about 50% power. Takeoff run is now longer and needs a bit more nose-up trim than before, and climb-out is definitely not like a fighter - but then it wasn't meant to be. This thing at full load handles like a big Cadillac - very pleasureable to fly. I'd still like to see those fuel/weight figures if you've still got them. The extra weight makes a definite difference in taxi.

My no's are: Center tank - 16,000 lbs/2,666 gallons; wing mains - 11,500 lbs/1,916 gallons each; wing aux - 10,000 lbs/1,666 gallons each.

P3 - is this close?

[p3aewguy]

navtech, p3, et al - p3, I took your fuel weight numbers and plugged them in to the KBT P-3's config file. Next thing was to reset the two values - beta_min and minimum_on_ground_beta, as suggested in an earlier post - went to the sim, started the bird - and it doesn't charge down the taxiway any more!! It takes a bit of a prod to get it moving at 100% fuel load, as would be expected. Once moving, adjusting the pitch as suggested by Milton to "ground fine" using ctrl-F2/F3 and a bit of juggling results in a taxi of about 6-7mph at about 50% power. Takeoff run is now longer and needs a bit more nose-up trim than before, and climb-out is definitely not like a fighter - but then it wasn't meant to be. This thing at full load handles like a big Cadillac - very pleasureable to fly. I'd still like to see those fuel/weight figures if you've still got them. The extra weight makes a definite difference in taxi.

My no's are: Center tank - 16,000 lbs/2,666 gallons; wing mains - 11,500 lbs/1,916 gallons each; wing aux - 10,000 lbs/1,666 gallons each.

P3 - is this close?

That's pretty much spot on what I have right now. I need to pull out my NATOPS manual and get the exact numbers. I don't have it dialed in fully, but it flies much more realistically. I'm going to apply the prop mods you mentioned also. I think I also changed the fuel consumption scalar some to get a more accurate fuel burn rate. I'll check the manuals this weekend and post the numbers.

About the loitering of engines, it was common on longer patrols to shut down #1 engine. The number 1 engine doesn't have any accessories on it, so killing #1 engine didn't have a detrimental effect on aircraft systems. #2 & 3 have the cabin pressurization engine driven compressors and a generator on each one. #4 has a generator only. Any loss of compressors limits pressurization and air conditioning. Any loss of electrical power generation can cause "load monitoring" and securing of different electrical buses. Consequently, the two inboards are never "loitered" and only shut down for emergencies. The same goes for #4 engine.
.
As far as fuel loads for missions, a "ramp" load is normally 28k. This would be used for most training flights. Depending on distance, transit flights would be 40-45k for a 5-6 hour transit. An 8-9 hour tactical mission would be 55k- max fuel depending on other loading (ordinance, extra crew, sonobouys, etc)

I'll research and post some numbers later this weekend.

Dave

[SSI01]

Many thanks! Will check periodically for the no's, no rush.

[p3aewguy]

Okay, finally dug out the old NATOPS manual. Here are the published fuel capacities:





Tank / FS tank name




U.S. Gallons




Weight (JP-4: 6.5 lbs. per gal.)






Tank 5 / Center1




2646




17,199






Tank 2 / Left Main




1671




10,861






Tank 1 / Left Aux




1606




10,439






Tank 3 / Right Main




1671




10,861






Tank 4 / Right Aux




1606




10,439









total




9200




59,800





Fueling procedure have you filling the wing tanks first, then tank 5 and transfer the fuel from tank 5 to the wing tanks as soon as possible, this was an aircraft structural requirement. We routinely kept 1500 lbs. in the center tank to keep the bladder wet. It was transferred to the wings after take-off. All of this is not applicable to FS, just some background info!

Here are the published Aircraft weights:




Weights




P-3C, P-3B Heavy weight




P-3A/B Light weight






Max Take-off




139,760 lbs.




127,500 lbs.






Empty (Zero Fuel)Weight




77,200 lbs.




71,584 lbs.





Zero Fuel weight is Max Gross weight minus all fuel (with Zero fuel). This was a not to exceed limitation. Use it as an empty weight value!

Hope this helps!

Dave

[p3aewguy]

Okay, finally dug out the old NATOPS manual. Here are the published fuel capacities:





Tank / FS tank name




U.S. Gallons




Weight (JP-4: 6.5 lbs. per gal.)






Tank 5 / Center1




2646




17,199






Tank 2 / Left Main




1671




10,861






Tank 1 / Left Aux




1606




10,439






Tank 3 / Right Main




1671




10,861






Tank 4 / Right Aux




1606




10,439









total




9200




59,800





Fueling procedure have you filling the wing tanks first, then tank 5 and transfer the fuel from tank 5 to the wing tanks as soon as possible, this was an aircraft structural requirement. We routinely kept 1500 lbs. in the center tank to keep the bladder wet. It was transferred to the wings after take-off. All of this is not applicable to FS, just some background info!

Here are the published Aircraft weights:




Weights




P-3C, P-3B Heavy weight




P-3A/B Light weight






Max Take-off




139,760 lbs.




127,500 lbs.






Empty (Zero Fuel)Weight




77,200 lbs.




71,584 lbs.





Zero Fuel weight is Max Gross weight minus all fuel (with Zero fuel). This was a not to exceed limitation. Use it as an empty weight value!

Hope this helps!

Dave




Actually, it would be better to subtract about 6000 lbs and use that for empty weight. Zero fuel weight includes crew and any other payload. FS only has an empty weight and separately loads crew and payload at the various stations. Sorry for any mixup.

Dave