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I noticed that the A20 and P39 (both for BOK) do not have tail wheels.

These are the first nosewheel planes made by this team.

Is there a difference in approach and handling compared to the tail wheel planes.

Will it land with a nose up config, does it taxi different?

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Airplanes with a nose gear are easier to to taxi, and easier to land. The reason is the Center of Gravity (CG) is forward of the main gear. The P-39 is unique in that the engine is behind the cockpit, putting the CG further aft. It pretty much puts the CG over the main gear.

 

It is considered bad form to land nose wheel first. And when I write bad form, I mean don't do it. So to answer your question, yes you try to land with the nose up allowing the main wheels to touch first and then relax back pressure to let the nose gear touch down.

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The P-39 is unique in that the engine is behind the cockpit, putting the CG further aft. It pretty much puts the CG over the main gear.

 

I'd like to see a source for the P-39 CG being any further aft than a conventional fighter. Because it is the tradeoff between stability and manoeuvrability in the pitch axis which limits the possible CG range, and you can't just move the CG backwards for convenience sake.

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I'd like to see a source for the P-39 CG being any further aft than a conventional fighter. Because it is the tradeoff between stability and manoeuvrability in the pitch axis which limits the possible CG range, and you can't just move the CG backwards for convenience sake.

To avoid any hurt feelings, let's agree that I've not suggested anybody simply moved the CG for convenience sake. And I completely agree that there are CG limits both forward and aft.

 

I confess I don't have the P-39 tech manual in my possession. I think it's a fairly logical inference the CG is further aft (than say a Cessna 206 or pick your favorite tricycle geared prop, maybe a T-28) based upon the simple WAM equation. For the non-pilot, that's Weight times Arm equals Moment. And from reading contemporaneous reports on the handling and flight restrictions by 5th Air Force pilots (see William Wolf's Fifth Fighter Command in World War II Vol 3).  I'll see what I can dig up for you. Hopefully me being a member of the Commemorative Air Force, I can reach a P-39 expert with the CenTex Wing.

 

But to be fair, I could be totally wrong, you could be totally correct. 

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I'd like to see a source for the P-39 CG being any further aft than a conventional fighter. Because it is the tradeoff between stability and manoeuvrability in the pitch axis which limits the possible CG range, and you can't just move the CG backwards for convenience sake.

 

It was fairly impossible to have the CG more forward on the P-39 even with the M4 gun installed. P-39 needed to keep the empty shell casings of the 37mm in the nose otherwise it became very unstable.

Well, I don't got any documents neither but an engine behind the pilot is more than enough evidence for me.

 

Look at that gear and compare it to other planes gear, a taildraggers gear is a lot more forward:

 

img_3774-800x.jpg

Edited by 216th_Jordan
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Like I said, I'd like to see a source actually discussing the relative position of the CG in the P-39 relative to contemporary fighter aircraft. From a brief look around it appears there was a problem with the CG moving backwards as ammunition was expanded, but the idea that the designers purposely built the aircraft with unacceptable pitch stability characteristics doesn't make sense. When you design an aircraft, you determine the aerodynamic characteristics you want, and then adjust the mass distribution to get the CG position required. 

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You land it the same as any other aircraft in game... follow the recommended approach and landing speeds etc, keep the nose up as you flare out, the only difference being, instead of gently pulling the stick towards you as the aircraft settles, you gently push the nose down until the nose wheel makes contact, roll out with any brakes and rudder input to keep it straight down the runway...

 

I remember years ago when I was doing my ppl, having flown the P-39 in IL2, how I chuckled to myself when I got to land my little Cessna 152, and how the principles where very similar in real life :)

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The position of the main gear in regards to the wing seem the same as other tricycle planes, somewhere just aft of mid point of wing. I have to think it is a pretty fine balance, too far back and hard to rotate the aircraft. The wing itself is mounted more midpoint of aircraft which makes sense given where the engine is. 


 ^Airabonita Collector aircraft for Midway...  :tease:

Edited by II./ZG1_HarryM
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I remember reading 'To Fly and Fight' by American ace Bud Anderson.

He flew the P-39, and although many pilots didn't like it, he loved it... I'll let you lot read the book, but some of the stuff he did in it was quite hilarious.

He said it was great when taxiing, 'you could wind the window down, put your elbow out and drive around like you were in a cadillac'

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I remember reading 'To Fly and Fight' by American ace Bud Anderson.

He flew the P-39, and although many pilots didn't like it, he loved it... I'll let you lot read the book, but some of the stuff he did in it was quite hilarious.

He said it was great when taxiing, 'you could wind the window down, put your elbow out and drive around like you were in a cadillac'

 

Yup, in the P-39 you could at least see where you were going on the ground without having to weave all over the place.

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Like I said, I'd like to see a source actually discussing the relative position of the CG in the P-39 relative to contemporary fighter aircraft. From a brief look around it appears there was a problem with the CG moving backwards as ammunition was expanded, but the idea that the designers purposely built the aircraft with unacceptable pitch stability characteristics doesn't make sense. When you design an aircraft, you determine the aerodynamic characteristics you want, and then adjust the mass distribution to get the CG position required. 

Come on Andy...nobody in this thread is making that suggestion, you're making inferences that no one is implying. You're trying to make comparisons to the CG of tailwheel aircraft (which is in fact aft of the main gear) and I posted about the fact the CG for airplanes with a nose wheel is forward of the main gear. How far forward of the main gear? "It depends" on the airplane, but the CG of the P-39 (in my educated estimate) is much closer to the mains, albeit forward of the gear. I'm not sure what you think I was trying to say. The little tail draggers I currently fly handle differently (specifically wheel landings vice three point landings) depending where the CG is in a very small tolerance (inches not feet) window. 

 

I apologize for being a bit thick, but I really do not see where you are trying to take this thread with your tangent. I was trying to answer the OP about the ease or difficulty of landing an airplane with a nosewheel.

 

To reiterate, the CG of airplanes with a nose gear is FORWARD of the main gear. Whilst the CG of conventional (tailwheel airplanes) is AFT of the main gear. Having a nose wheel generally makes landings much easier.

Edited by busdriver
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Just to show it could be done, a 'P-39' with taildragger landing gear:

Bell_XFL-1_Airabonita.jpg

 

https://en.wikipedia.org/wiki/Bell_XFL_Airabonita

 

 

Yes, it is in the front of the Wing but the wing is rather rearward to deal with the rearward CG.

 

messerschmitt-bf109_9.jpg

FW_190_A8_1.jpg

 

 

P-38 for comparison with more forward CG and tricycle.

 

32_1.jpg

 

 

As you can see the wing is the best indication of the CG (as it should be.)

What is important for an aircrafts pitch stability is its Center of Lift on the Wings in relation to the CG AND how much mass is outside of CG in relation to it. (Mass inertia = m * r^2) So the engine (heaviest part of the plane) being basically over the CG will in almost all cases cause instability problems of some sort. On the other hand you can pull that little more lead you need to make that victory, before you stall out, with a short pull on the stick.

 

That said, I love the P-39.

Edited by 216th_Jordan
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"the CG for airplanes with a nose wheel is forward of the main gear." Indeed. Not least because if it wasn't, the plane would tip on its tail. And I'm not trying to take this thread anywhere - I merely asked for a source to back up your claim that the P-39 CG is "further aft". A source. Not waffle about 'WAM equations' and 'educated estimates'. If you don't want to provide a source, fine. But don't expect me to accept it just because you say so. 

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"the CG for airplanes with a nose wheel is forward of the main gear." Indeed. Not least because if it wasn't, the plane would tip on its tail. And I'm not trying to take this thread anywhere - I merely asked for a source to back up your claim that the P-39 CG is "further aft". A source. Not waffle about 'WAM equations' and 'educated estimates'. If you don't want to provide a source, fine. But don't expect me to accept it just because you say so. 

Just so I understand, you accept that I posted the CG on a tricycle gear is FORWARD of the mains. whew...

 

But you want a source that specifies how far forward of the mains the CG of P-39 is? Correct? I don't have the W&B data set for the P-39, but hold the opinion, educated opinion based upon my reading and a tiny bit of flying experience, the CG for the P-39 is closer to the mains than say the T-28. Why? Because of the location of the engine, and the fact expended shells would be retained for ballast. Why retain ballast FORWARD of the mains if the CG were not closer to the mains (the essence of my "further aft" remark)? I have no expectation that ANYONE will believe anything I post.

 

Cheers

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Just so I understand, you accept that I posted the CG on a tricycle gear is FORWARD of the mains. whew...

 

But you want a source that specifies how far forward of the mains the CG of P-39 is? Correct? I don't have the W&B data set for the P-39, but hold the opinion, educated opinion based upon my reading and a tiny bit of flying experience, the CG for the P-39 is closer to the mains than say the T-28. Why? Because of the location of the engine, and the fact expended shells would be retained for ballast. Why retain ballast FORWARD of the mains if the CG were not closer to the mains (the essence of my "further aft" remark)? I have no expectation that ANYONE will believe anything I post.

 

Cheers

 

Yes. I accept the blindingly-obvious thing I've already stated. As for the rest, I'm not interested in guesswork, educated or otherwise. Or in arguments about aircraft I've not even mentioned. So unless you have a source for your original assertion, I suggest you consider this discussion closed, since it is clearly going nowhere useful.

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In order for an airplane to be stable, the CG has to be ahead of the center of lift - otherwise it would "fly" like a leaf in the wind. The center of lift can roughly be estimated at the 1/4 chord line of the wing (Probably the #1 reason the wing sits so far back in the fuselage).  I don't know exactly where the CG is on the cobra, but it is certainly ahead of the 1/4 chord, which is also ahead of the main gear.

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Also, look at spin recovery at about 13.47... I've stated this before, but it's completely different from your standard spin recovery, due to where it's engine is located in the airframe.

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Yes. I accept the blindingly-obvious thing I've already stated. As for the rest, I'm not interested in guesswork, educated or otherwise. Or in arguments about aircraft I've not even mentioned. So unless you have a source for your original assertion, I suggest you consider this discussion closed, since it is clearly going nowhere useful.

 

Notice where the green arrow is pointing. Note the short distance forward of the main gear. Draw your own conclusion whether this fits a description of "putting the CG further aft," as I posted in my first reply to the OP.

 

 

post-19230-0-16247600-1475034004_thumb.jpg

Edited by busdriver
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I think any reasonable person would conclude that you have failed to show anything of significance, beyond the fact that the CG of the aircraft is shown somewhere around 25% of wing chord, and the mainwheels are at about 50%. But don't let that stop you feeling that you've proved yourself right, if it keeps you happy. 

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@ Busdriver; I can also attest that being retired and still alive is a very good way of spending time. As much as possible.

I agree: Life is good.

;)

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Can someone explain to me, why having a larger portion of the aircraft's mass placed very close to the CG would lead to stability issues? I'm not an engineer, and don't know much about the topic, but common sense (which might very well be wrong) would suggest, that concentrating the mass around the CG would be more stable, not less.

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6./ZG26_Klaus_Mann

Can someone explain to me, why having a larger portion of the aircraft's mass placed very close to the CG would lead to stability issues? I'm not an engineer, and don't know much about the topic, but common sense (which might very well be wrong) would suggest, that concentrating the mass around the CG would be more stable, not less.

Inertia. Think of a Smart Car and a Volvo Station Wagon in the Snow. The Volvo with it's long Overhangs and widely distributed Mass will tend not to enter a Spin easily, but when it does it's also hard to Stop, while a Smart Car with it's centered Weight and squarish stance will be less stable, but easy to control and recover. 

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