How was CG balancing handled in WW2 aircraft?

[bustr]

Recently I read a conversation on a warbirds forum where it was pointed out the owner of a P51 wanted to remove the guns. So he had a mechanic take them out and he went up for a ride. Seems the mechanic did not add weight to the tail and the owner of the P51 had a very scary ride and landing along with a visit from the local FAA rep.

Is this real in terms of P51's and removing the guns in the first place? Secondly, how was this handled with all the external ordinance many aircraft carried for specific roles? 109's and their gondola. 47's/51's and drop tanks, bombs, rockets. 190's and removing the outboard cannon. Tiffy firing rockets and so on.

What happened to the CG balance when the weight of ordinance suddely was gone and the pilot had to dogfight?

[curry1]

Recently I read a conversation on a warbirds forum where it was pointed out the owner of a P51 wanted to remove the guns. So he had a mechanic take them out and he went up for a ride. Seems the mechanic did not add weight to the tail and the owner of the P51 had a very scary ride and landing along with a visit from the local FAA rep.

Is this real in terms of P51's and removing the guns in the first place? Secondly, how was this handled with all the external ordinance many aircraft carried for specific roles? 109's and their gondola. 47's/51's and drop tanks, bombs, rockets. 190's and removing the outboard cannon. Tiffy firing rockets and so on.

What happened to the CG balance when the weight of ordinance suddely was gone and the pilot had to dogfight?

Why would adding weight to the tail help; after you have already removed weight from the front/center of the aircraft?

[Tupac]

Seems like you would just want to add some weights in the gun bays - dont see why you would add it in the tail.

[Charge]

They added ballast to the tail if the nose was too heavy. If the tail was too heavy, well I don't know.... Maybe all planes had a ballasted tail were it could be easily reduced if needed?

Ballast weights were used at least in 109s and Spits.

http://www.spitfireperformance.com/ab197.html

Considering ordnance the placement of ordnance should have been near CoL or forward of CoL if possible (eg. ME410 bomb bay). Having tail weight was considered very dangerous and more so in aircraft which already had a tendency to be tail heavy. E.g Yak was known to be a tail heavy aircraft making it somewhat unbalanced in maneuvers as it tended to tighten the turn by itself and had to be "pushed out" of turn. Having a heavy nosed a/c would make it sluggish in maneuvers but sometimes when loaded with ordnance that would also be desirable. Weight distribution was one of the defining qualities of a good combat aircraft and also one of the limitations where the ordnance could be carried and also in which order it had to be dropped if the weight was distributed length wise, which it usually wasn't but all stacked near CoL.

In some aircraft all the new additions posed new problems, as in P-51 when additional internal fuel was required the tank was added behind the pilot and it moved CoG aft and the aircraft would become dangerous in maneuvers when the tank was full. Same with FW190 with additional fuel tank.

Maybe they should have removed ballast from tail in P-51 gun case?

-C+

[dirtdart]

http://www.engbrasil.eng.br/index_arquivos/rs/rs4.pdf

Great link to remind me of why ditching math class was a bad idea.....

Anyway, what was the MAC of the 51D?  How much weight did the removal of the guns contribute to one side or the other of the CG range?  I did about 5 minutes on line and did not find anything free or unsubscribed that may have talked CG range on a real mustang.  

[icepac]

There was probably more going on than just the weight.

Did they do more than just remove the guns? ......or did they just take them out.

[pervert]

I always wondered how a liquid moving around (fuel) affected the COG or stability in an aircraft, especially the camel in WW1 at slow speeds and in stalls.

[BravoT]

The short answer is that every aircraft has a Weight & Balance chart, and so long as things are loaded properly (and not overloaded), the aircraft will be within CG design limits.  There will of course be performance differences for a heavier aircraft than a lighter one, but presumably WWII pilots (like modern day pilots) were trained on both "clean" and "heavy" aircraft.

As to fuel, I've never felt or perceived any effects on stability from it moving around in the wing tanks of a Cessna, whether fast, slow, stalls, spins, etc.  So long as it stays within the CG limits (which it will, regardless of how much sloshing is going on, because it's confined to the fuel tanks), I don't see how it would make much difference.

[pervert]

The short answer is that every aircraft has a Weight & Balance chart, and so long as things are loaded properly (and not overloaded), the aircraft will be within CG design limits.  There will of course be performance differences for a heavier aircraft than a lighter one, but presumably WWII pilots (like modern day pilots) were trained on both "clean" and "heavy" aircraft.

As to fuel, I've never felt or perceived any effects on stability from it moving around in the wing tanks of a Cessna, whether fast, slow, stalls, spins, etc.  So long as it stays within the CG limits (which it will, regardless of how much sloshing is going on, because it's confined to the fuel tanks), I don't see how it would make much difference.

The difference is I have read modern aircraft have baffles in the tanks to restrict fuel moving around as one mass, in a WW1 fighter as far as I know it literally was just a steel box. This a model but show were the 2 tanks are positioned.

[BravoT]

The difference is I have read modern aircraft have baffles in the tanks to restrict fuel moving around as one mass, in a WW1 fighter as far as I know it literally was just a steel box.

True, but the tanks in modern aircraft are a lot larger than a WW1 era aircraft, both in terms of size and capacity.  And if baffles are part of the design to meet acceptable CG parameters, then it is what it is, and that was a design choice/compromise made by the designer.

Still, any aircraft design will take into account changes in CG throughout flight and what the limitations are before flight becomes unstable.  I fly Cessnas (and not Camels or P51s or F15s) so I certainly can't speak about all aircraft, but I do know that I do one Weight & Balance check as part of a pre-flight, and then don't worry about CG since any changes within flight are necessarily within the flight envelope.

[Babalonian]

I'll need to look it up, but if I am recalling correctly they had to put an additional heavy counterweight in the tail of some P-51s to offset very heavy ordnance options (150gal DTs, 1000lb bombs, rockets + 500/250lb bomb combos, etc.).  Mostly to prevent ground looping/nose planting I think.

As it sounds like this particular mustang was purchased from the military by the owner with the guns, it's more likely it saw actualy use by the military, and more likely it had this modification already made and possibley even the mechanic had no knowledge of it's existence or installation on the aircraft.

But even then, so much more doesn't make sence about this and more information is truely needed if we're to understand and make some of it...  If it had the 50-cals, it probabley also had the auxiliary fuel tank in the aft fuselage as was GI.... a relatively small tank, but it amongst many other things that were removed by private aviators do add up...  it's anyone's guess if the heavy/clunky original GI radio set was or wasn't still crammed behind the pilot/cockpit or if it had been converted to a spare seat and he had a passenger, etc., etc., etc.. 

[RTHolmes]

How was CG balancing handled in WW2 aircraft?

Trim

[RTHolmes]

I did about 5 minutes on line and did not find anything free or unsubscribed that may have talked CG range on a real mustang.

try http://www.wwiiaircraftperformance.org/. if the document exists, its probably on there somewhere

[Wmaker]

Trim

Trim is to make the control forces manageable. Aircraft design and load management keeps the CoG in check.

[MachFly]

Trim

The only thing trim does it takes the extra force off the controls, it has nothing to do with CG. If your aircraft is unable due to CG the only thing you can do the help it is remove/add some weight or move some of the weight to a different part of the aircraft.