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View Full Version : Extra Ammo in P47 Makes You Heavier But...



MisterMark
10-16-2009, 12:37 AM
as you expend it does it make you lighter?

Thanks,

Mark

na85
10-16-2009, 12:47 AM
Easy way to test:

Set unlimited fuel, but limited ammo. Go into QMB, see how fast you can get the 47 to go in level flight.

Then shoot all your ammo, and see how fast you can get it to go in level flight. If it's faster after shooting your ammo, it is lighter.

Let us know what you find out.

BillSwagger
10-16-2009, 04:06 AM
The trade off is very slim to none. Normally, i always use extra ammo settings, but sometimes i forget, and i notice no performance gain by using the default ammo load.

This doesn't mean there isn't a performance gain, its just not that noticeable. I'm not in flight, and suddenly telling myself, "oops i forgot to load twice as much ammo again". Not til the 'out of ammo' warning pops up.

Come to think of it, i don't think the plane is any faster or slower, but the roll performance might be slightly better.
It would be an interesting test.

DKoor
10-16-2009, 04:25 AM
The diffs in performance besides speed and roll, should also mainly be noticed in climb and turn.
It should be rather easily to check via device link.

MisterMark
10-16-2009, 07:09 AM
Device link?

Frankthetank36
10-16-2009, 07:12 AM
Default is less than 100%? Hm, no wonder my Seafire runs out of ammo so quickly after getting a kill or two in campaigns.

TinyTim
10-16-2009, 07:27 AM
Originally posted by Frankthetank36:
Default is less than 100%? Hm, no wonder my Seafire runs out of ammo so quickly after getting a kill or two in campaigns.

It's only a few planes with an "extended ammo" option. P-47 for example has 200rpg on "normal" and 425rpg on "extended" option. Some other planes that come to mind are some versions of P-39 and a Mossie, maybe also Beaufighter. Stock Seafires should have standard 120rpg for cannons.

DKoor
10-16-2009, 11:23 AM
As I assumed (judging from past experiences) level speed is virtually the same... @ SL it is 584kph for both fully loaded 47 (extra ammo) and 47 on Extra Ammo that shoot out all ammo.

However huge gaps are observed in climb ability;
From take off position to 4000m;
1000m 1:56 2:04
2000m 2:44 2:58
3000m 3:34 3:53
4000m 4:24 4:49

First time column is for 47 with Extra Ammo that emptied the guns prior to take off, second is for 47 that is fully loaded with Extra Ammo.

Main conclusion: difference in weight is modeled.

Linked to this, turn ability is probably also modeled as well, because lower RoC will impact turn times.

M_Gunz
10-16-2009, 11:30 AM
Originally posted by DKoor:
As I assumed (judging from past experiences) level speed is virtually the same...

+1 -- as it should be. The Lead Sleds hurt more in acceleration and climb and benefit in dive.
The thing is that compared to the unloaded weight of a P-47, what percent is a couple thousand rounds of 50 cal?

na85
10-16-2009, 11:48 AM
Originally posted by DKoor:
As I assumed (judging from past experiences) level speed is virtually the same... @ SL it is 584kph for both fully loaded 47 (extra ammo) and 47 on Extra Ammo that shoot out all ammo.

Wow, I really would have thought that the extra weight would cause more drag and affect the 47's top speed.

M_Gunz
10-16-2009, 12:27 PM
At high speed the difference in AoA needed to make the extra lift is tiny. In a slow plane perhaps it does? Crumpp!

DKoor
10-16-2009, 02:14 PM
LoL I just re-read my post above and boy I've made one of the most confused posts I ever posted here http://forums.ubi.com/images/smilies/53.gif .
I guess that's all part of that "English not being primary language" thing. http://forums.ubi.com/images/smilies/16x16_smiley-indifferent.gif

na85
10-16-2009, 02:23 PM
Originally posted by M_Gunz:
At high speed the difference in AoA needed to make the extra lift is tiny. In a slow plane perhaps it does? Crumpp!

I was thinking more along the lines of more weight = more lift = more induced drag.

na85
10-16-2009, 02:24 PM
Originally posted by DKoor:
LoL I just re-read my post above and boy I've made one of the most confused posts I ever posted here http://forums.ubi.com/images/smilies/53.gif .
I guess that's all part of that "English not being primary language" thing. http://forums.ubi.com/images/smilies/16x16_smiley-indifferent.gif

Don't sweat it. Your english is very good.

M_Gunz
10-16-2009, 03:21 PM
Originally posted by na85:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by M_Gunz:
At high speed the difference in AoA needed to make the extra lift is tiny. In a slow plane perhaps it does? Crumpp!

I was thinking more along the lines of more weight = more lift = more induced drag. </div></BLOCKQUOTE>

It does and there is that CL squared term in the induced lift formula too. But as was finally hammered into me by Ugly_Kid,
the ratio of induced to parasitic drag is so low at high speed that even to double it has little meaning.

na85
10-16-2009, 03:32 PM
Originally posted by M_Gunz:

It does and there is that CL squared term in the induced lift formula too. But as was finally hammered into me by Ugly_Kid,
the ratio of induced to parasitic drag is so low at high speed that even to double it has little meaning.

Works for me.

AndyJWest
10-16-2009, 04:25 PM
I've done a little testing on the effect of weight on max airspeed in IL-2, and as the theory says it should, you only get a noticeable effect at high altitude. I don't have the figures to hand, but it is simple enough to reproduce.

Does anyone know the correct technique for measuring roll rate, though? As has been said, this should change with ammo load in a P-47, but I'm not sure how you would measure it.

megalopsuche
10-16-2009, 11:18 PM
If you're going to fly the P-47, take the extra ammo. It's a big plane with 33% more firepower than the P-51D. Forget your gunnery % and blast away. http://forums.ubi.com/groupee_common/emoticons/icon_cool.gif

TgD Thunderbolt56
10-20-2009, 09:09 AM
I would take it a step farther and say if you're going to take a P-47, and not going to take ordnance, then always take the extra ammo loadout.

So what if it affects your turn radius or roll rate. If your turn radius (or lack thereof) is contributory to your demise in the jug, that's your fault...not the extra ammo's.

Fly it high, fly it fast and use it for what it does better than any aircraft in the game...which doesn't involve very much turning. http://forums.ubi.com/groupee_common/emoticons/icon_wink.gif


p.s. Oh yeah...I'm back. http://forums.ubi.com/images/smilies/partyhat.gif

BillSwagger
10-20-2009, 01:13 PM
Historical load outs were somewhere between 300 and 400 rpg depending on the ordinance.
I'm not sure why 200rpg is the default, as that usually represents a very heavy load, ie rockets/bombs and a drop tank.

For that reason i usually take extra ammo, when not taking any other ordinance.

Not to brag but my online personal best is 7 planes in the same sortie with this plane using the extra ammo. I know that's not that much, as i'm sure there are other pilots out there who can top that in their bird of choice, but it was interesting cause I had to return to base for more fuel, while i probably still had about ten seconds of firing time, guesstimate.

M_Gunz
10-20-2009, 02:11 PM
Originally posted by AndyJWest:
I've done a little testing on the effect of weight on max airspeed in IL-2, and as the theory says it should, you only get a noticeable effect at high altitude. I don't have the figures to hand, but it is simple enough to reproduce.

Does anyone know the correct technique for measuring roll rate, though? As has been said, this should change with ammo load in a P-47, but I'm not sure how you would measure it.

Use sustained climb at 400+ IAS (parasitic drag using up much engine power, less weight difference should show more?)
and two separate runs to have the same basic amount of fuel each time. We know that fuel used does lighten the planes
in IL2.

BillSwagger
10-21-2009, 03:49 PM
I kept this in mind when i flew a P-47 last, and there is no obvious difference in rate of roll between empty, default or extra ammo load outs.

I didn't have a stop watch but i used a more informal method of recording tracks and relying on the clock timer in the ntrk. I performed rolls at 2000-3000ft at 200-250IAS, with and with out rudder. It ranged between 4-5 seconds to do one complete roll.

As for climb the only noticeable difference was above 5000m. I didn't do any comparisons but using a default load out, i noticed it zoomed upward much more quickly when i threw it into WEP. Something to consider when "weighing" your options.



ahhh puns.



Bill

Treetop64
10-22-2009, 08:09 PM
Originally posted by na85:
Easy way to test:

Set unlimited fuel, but limited ammo. Go into QMB, see how fast you can get the 47 to go in level flight.

Then shoot all your ammo, and see how fast you can get it to go in level flight. If it's faster after shooting your ammo, it is lighter.

Let us know what you find out.

No offense, but that is not a very good benchmark for measuring the weight of the aircraft after expending ammunition. It would probably be more noticable to gauge the up-trim behaviour of the aircraft in level flight at a consistent speed and throttle/prop/mixture settings. Either way, however, the benefits of the lack of weight from expended ammo are minimal at best, and is pretty much just academic.

Kettenhunde
10-22-2009, 08:38 PM
The weight is significant and easy to calculate.

HarryVoyager
10-24-2009, 04:19 PM
The weight is about 200kg, which in a plane with a takeoff weight of 6 tonns, really isn't that significant, especially given that it more than doubles your fire time.

M_Gunz
10-24-2009, 05:00 PM
Originally posted by na85:
Set unlimited fuel, but limited ammo.

I should have caught that trick first time around! Very neat!

Kettenhunde
10-24-2009, 07:56 PM
What will a 4% change in weight do to the performance of my airplane?

V2 = V1 * SQRT W2/W1 = 95 mph EAS = 83KEAS* SQRT 10000/9600 = 83 (1.04) = 85 KEAS = 98 mph EAS

Positive Limit:
LLF2/LLF1 = W1/W2
LLF2/6G = 10,000lbs/9,600lbs
LLF2 = 6 * 10,000/9,600
LLF2 = 6.25G

Negative limit
LLF2/LLF1 = W1/W2
LLF2/3G = 10,000lbs/12,000lbs
LLF2 = 3 * 10,000/9,600
LLF2 = - 3.125G


In parametric study of zoom climb from 250 KEAS to stall speed our airplane at 10,000lbs can zoom to 5606ft.

At 9,600lbs our airplane reaches a zoom height of 5960 ft or a gain of 354 ft.

Our climb performance is reduced as well when we add weight.

ROC = 33,000 (1955lbs 525lbs) / 10,000lbs = 4719fpm

ROC = 33,000 (1955lbs 525lbs) / 9600lbs = 4915fpm

In fact the entire envelope is shrunk when we add weight to an airplane.

Learning to do the math will help to eliminate much of the idle speculation and guesswork. Of course you still have to contend with those who will go to great lengths like re-inventing EAS to prove any point for their team.

All the best,

Crumpp

JtD
10-25-2009, 01:11 AM
Originally posted by BillSwagger:
Historical load outs were somewhere between 300 and 400 rpg depending on the ordinance.
I'm not sure why 200rpg is the default, as that usually represents a very heavy load, ie rockets/bombs and a drop tank.

AF documents say 267 standard, 425 max. This applies for both 6 and 8 guns. Now the funny thing is that 6*267 = 8*200 = 1600; maybe the folks at 1C thought that 1600 rounds were standard outfit no matter how many guns installed.

Did you know that the ammo and fuel aboard a P-47 weighs as much as a whole Ki-27 fighter plane (roughly 1.5 t)?

BillSwagger
10-25-2009, 01:50 AM
Originally posted by JtD:
Did you know that the ammo and fuel aboard a P-47 weighs as much as a whole Ki-27 fighter plane (roughly 1.5 t)?

While observed in the wild, the P-47 feeds on many small planes including 109s.

Xiolablu3
10-25-2009, 04:14 AM
Originally posted by BillSwagger:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by JtD:
Did you know that the ammo and fuel aboard a P-47 weighs as much as a whole Ki-27 fighter plane (roughly 1.5 t)?

While observed in the wild, the P-47 feeds on many small planes including 109s. </div></BLOCKQUOTE>


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