What do you think of the bell p-39 was it a good dogfighter

[plan_D]

That was 1st Squadron, not 111th Squadron. Every Hurricane thereafter had seat armour.

[lesofprimus]

Cool info....

[FLYBOYJ]

Originally Posted by JamesBlonde

Removing a bit of armour shouldn'y make much difference.

I hate to say it James but that is wrong. As little of 5 pounds removed or added can shift the center of gravity out of limits. If the aircraft gives little or no stall warning, this could be disastrous during landing and especially if a green pilot is flying.

This is 4x more critical on helicopters, just ask Adler!

[DerAdlerIstGelandet]

Originally Posted by FLYBOYJ

I hate to say it James but that is wrong. As little of 5 pounds removed or added can shift the center of gravity out of limits. If the aircraft gives little or no stall warning, this could be disastrous during landing and especially if a green pilot is flying.

This is 4x more critical on helicopters, just ask Adler!

That is absolutely true! On helicopters if the CG is only a little bit out it completly changes the flight characteristics of the aircraft. For instance it can make it harder to pull out of a roll or a sharp turn, which can be very deadly.

We actually had our whole fleet grounded shortly after we got back from Iraq because we had removed the ballistic armour installed while we were there but there were areas around the cockpit that could not be removed so there was like 80 extra pounds in the cockpit. This screwed up our CG way crazy and our QC shop and the Lar had to figure out a way to modify the aircraft to get the CG into limits. Eventually we were able to get the stuff out and work something out. All is good now!!!

[wmaxt]

You have to take into consideration where in relation to the CG the weight is. 5 pounds in the tail is may affect the CG more than 100lbs 1 foot aft of the CG.

In the P-39 the armor was very close to the CG and made little if any difference in it. Modified P-39s were very fast, after the war they won many air races. Speeds comparable to P-38s anf F2Gs and normaly faster than the P-51s until the more modified P-51s started showing up.

In the hands of a good pilot it was pretty effective and quite maneuverable, though it had been hurt badly by the Engineers at Wright Patterson AB with "It looks Good" engineering. When used in a way that matched it's capabilities it was an effective aircraft!

wmaxt

[FLYBOYJ]

Originally Posted by wmaxt

You have to take into consideration where in relation to the CG the weight is. 5 pounds in the tail is may affect the CG more than 100lbs 1 foot aft of the CG.

In the P-39 the armor was very close to the CG and made little if any difference in it. Modified P-39s were very fast, after the war they won many air races. Speeds comparable to P-38s anf F2Gs and normaly faster than the P-51s until the more modified P-51s started showing up.

In the hands of a good pilot it was pretty effective and quite maneuverable, though it had been hurt badly by the Engineers at Wright Patterson AB with "It looks Good" engineering. When used in a way that matched it's capabilities it was an effective aircraft!

wmaxt

I agree for the most part however even with the armor close to the CG, I believe the CG envelope of the 39 was only a few inches. Removing the armor and flying the aircraft full of fuel or with minimal fuel could produce undesirable results. I would like to get my hands on a P-39 W&B chart and find out how much armor was actually carried on the -39....

The post war 39s and 63s were very fast and when they were modified, and I'm sure that when armor and guns were removed, in some cases ballast had to be added as well.

[FLYBOYJ]

Originally Posted by FLYBOYJ

I agree for the most part however even with the armor close to the CG, I believe the CG envelope of the 39 was only a few inches. Removing the armor and flying the aircraft full of fuel or with minimal fuel could produce undesirable results. I would like to get my hands on a P-39 W&B chart and find out how much armor was actually carried on the -39....

The post war 39s and 63s were very fast and when they were modified, and I'm sure that when armor and guns were removed, in some cases ballast had to be added as well.

Stumbled on this from a former P-39 pilot....

"The center of gravity of the Cobra was exceptionally rearward. We even had 10 kilos of lead weight mounted in the forward portion to unload the tail. Sometimes this center of gravity created problems with the wing and in inverted flight. Once again, during non-combat flights, don’t place any load in the empty rear portion of the fuselage. Somebody didn’t do it and couldn’t make it back. The airplane flew as if balanced on a tip of an awl. Later we gained experience and loaded everything in the forward compartment."

[wmaxt]

Originally Posted by FLYBOYJ

I agree for the most part however even with the armor close to the CG, I believe the CG envelope of the 39 was only a few inches. Removing the armor and flying the aircraft full of fuel or with minimal fuel could produce undesirable results. I would like to get my hands on a P-39 W&B chart and find out how much armor was actually carried on the -39....

The post war 39s and 63s were very fast and when they were modified, and I'm sure that when armor and guns were removed, in some cases ballast had to be added as well.

The weight and Balance sheet and the armor location/weight charts would tell us if ballast was required.

The P-39 though didn't have issues like the P-51 where the fusalage tank could actually go from one extreme to the other. I've just never heard of serious problems with the P-39 regarding CG issues. Removing the armor was common on P-39s.

My main point is that CG issues could be major but normaly they just need to thought out and approached carefully. It's also true that designers like to place things that change in flight, like fuel, in locations that are nuetral to the CG and things that don't change, like armor, in places that affect the CG more. Research is important here.

wmaxt

[FLYBOYJ]

Originally Posted by wmaxt

The weight and Balance sheet and the armor location/weight charts would tell us if ballast was required.

The P-39 though didn't have issues like the P-51 where the fusalage tank could actually go from one extreme to the other. I've just never heard of serious problems with the P-39 regarding CG issues. Removing the armor was common on P-39s.

wmaxt

And I could tell you in "basic pilot 101" reward CG is not a good thing, especially for newer pilots. I also found data that the Russians issued directive to P-39 pilots not to pull out of dives in a left turn...the tail could be pulled off!

[wmaxt]

Originally Posted by FLYBOYJ

And I could tell you in "basic pilot 101" reward CG is not a good thing, especially for newer pilots. I also found data that the Russians issued directive to P-39 pilots not to pull out of dives in a left turn...the tail could be pulled off!

I agree 100%, and forward CG can get real interesting when you take power off as well. I was never suggesting flying anything out of balance. I was just commenting on the possible effects:

First the effects are variable depending on distance from the CG.

Second is that the pilots armor in a P-39 is very close to the CG.

Third the resulting effect might not be that great. If ballast is required, a 5lb weight in the nose/tail may be enough to countor a reduction of 100lbs, 6 inches off the CG (using examples for discussion here not actual numbers)

I'm more aware of the P-39 than knowledgable and I am not debating that removing the armor may have an effect (other than just weight reduction) or that it might be a lot just that it probably isn't a big deal if it's done right.

wmaxt

[FLYBOYJ]

I think we agree to agree!

When I was looking up information on the P-39 I found that aces Yeager and Anderson really liked the airplane. I always felt it got a bad rap. I thought the P-63D was the Bell answer to the P-51, but too little, too late.

I'll try to find the site I got some of this data from...

[DerAdlerIstGelandet]

Ah the Weight and Balance Sheet! I hate it, I hate it, I hate. So important yet so tedious!

[FLYBOYJ]

Yep!

[DerAdlerIstGelandet]

We have to update our 365-4 and -17's every 90 days and it can be a real headache.

[FLYBOYJ]

I found on www.zenowarbirdvideos.com a sample P-39Q W&B chart. This aircraft calcualtes horizontal AND vertical CG. The page is difficult to read but it looks like the horizontal CG envelope is about 1 inch (133.56/ 134.22 from what I could read)