Crumpp

The P-51 is bouncy and likes to float, that is a fact. I am out of practice so it took me three times to do it without bouncing. I did a nice wheel landing and was going to post the track but the DCS 1.5 track bug just shows a fireball, LOL. The FW-190 does nice wheelers, btw. Much easier to get a nice one than the P-51. Wheel landings are fast compared to a 3 pointer. It does not really matter what your trim is set too or if the aircraft is parallel to the ground. In fact it will not be because the speed should be too slow and the AoA high. Fly the plane to the runway, let the mains settle, and as soon as they touch, move the stick slightly forward to pin the mains to the runways. As the plane slows, move the stick back. Rudder for directional control until the speed bleeds off and then transition to the brakes. You should be fully stick back by the time the tail settles to the ground. A wheel landing simply takes more runway and is not short field technique. The P-51 has a steerable tailwheel so once it is on the ground you can use it for directional control. It is a dance compared to a tricycle gear aircraft.

Are you guys putting a little forward stick into the aircraft on wheel landings? Try that and see if does not eliminate the bouncing. http://www.taildraggers.com/Documentation.aspx?page=Landing

Need to market a Force Feedback seat cushion.....

I am pretty sure Yo-Yo knows the ailerons of the FW-190 utilized push rods. Push rods do tend to have lighter forces than conventional cables are immune to stretch. That is only part of the picture. The ailerons are aerodynamically balanced (Frise Type), mass balanced, a proper hinge location, aileron sizing, and torsional stiffness for both the aileron and the wing. All of that combined adds up to careful attention to the hinge moments (control forces). It is a lot more than just push rods. That being said, the FW-190 was laterally unstable at the stall and aileron vibration (flow separation) along with the corresponding rolling moment was the first indication of the stall point. Sort of like the Spitfire tail buffeted first warning of the impending stall, the FW-190's ailerons experienced the first signs of flow separation. Additionally, lateral instability occurred at high altitude and Indicated air speeds. I would have thought that was a mach effect but it appears related to the rigging as in badly adjusted ailerons, it is present on take off. Maybe an overbalanced??

I have had much success using a lag turn against the P-51 in the FW-190D series in DCS.

It was a joke bongodriver, not a comment on the structural integrity of biplanes. Yes you can easily do aerobatics in an LE slat equipped aircraft and you can do them at speeds a non LE slat wing cannot.

There is no agenda. This is not personal to me so do not make it so. Get that nonsense out of your head, please. Yes, you can find the %MAC for any aircraft design. That is the beauty of it and why the NACA choose that method in the absence of RAE data. They simply had to load the aircraft normally, pull out a tape measure and some scales to get all the weight and balance information required to do their testing.

Here bongodriver.... This may help you to understand. The RAE used 84inches for their MAC. Load condition A: 39.2% of an 84" MAC = 84in * .392 = 32.92in We have a distance of 32.9in from our LEMAC to a point that equals 12.2in aft of the RAE datum. 32.9in - 12.2in = 20.7inches for the LEMAC Substituting that LEMAC into the MAC forumla gives us our ability to convert CG LOCATION. I am very patiently trying to explain this to you. Maybe you will understand it and it will not be such a personal event.

You must have missed reading the answer to your question. You are confusing methods, bongo. The RAE used the same datum point for their Arm/moment methodology and MAC methodology for expressing the CG location. That does not mean they used the same LEMAC. The LEMAC will then change to maintain the non-dimensional ratio % MAC is expressed in.

Ohh, I bet that would create an issue. The tiger moth only has slats on the top wing so you might find yourself going from a biplane to a monoplane real quick!

NO, the MAC is fixed to the design of the wing. It is a function of the wing's chord. http://www.airfieldmodels.com/information_source/math_and_science_of_model_aircraft/formulas/mean_aerodynamic_chord.htm LEMAC is measured from a point to the MAC, usually the nose or front of the aircraft. You have to know the LEMAC and the MAC for the system to work properly. Mixing up the values like Fredrick and JtD did will produce an error. In the case of the Spitfire, it is measured from the intake. Just think, by the time this thread is over, you will learned how to actually calculate this stuff, LOL. It does both for different reasons, bongodriver. When the RAE tested that elevator design they tested three devices to increase the stick force gradient. 1. Inertial weight 2. Control cables as tight as possible 3. Friction device at the elevator cross shaft All three of those changes increase the hinge moments to increase the stick force gradient. You can think of the Rear CG limit as the minimum stick force gradient the designer will accept.

No it does not have the late war elevator. That modification represents an increase in the stick forces. Check out my first post for the basic explanation of how that works. What that will do is slow the rate at which the pilot can accelerate the stick and make the aircraft more controllable. Instability without control is a bad thing; increase the control and it becomes a good thing for maneuverability. It is still going to have the quirks (double control) but that is the price you pay. That is not an issue and Yo-Yo knows what he is doing. There is a small cadre of members who seem to believe I am on some mission to "destroy" the Spitfire. That is simply a fantasy. The Spitfire was the British F-22 raptor of it's day and represents the pinnacle of British fighter technology for the late 1930's/early 1940's. Stability and Control technology was really in its infancy. There was a common misconception that maneuverability and instability were directly connected. They but only to the extent the pilot can precisely control. This effected the majority of World War II fighters and most of them exhibit some form of instability in their envelope as a result. There was also the erroneous belief that elevator forces had to be reduced at high speed. Some designers broke away from this while others did not. Both of these engineering misconceptions helped shape the personality of the aircraft.

:thumbup:

No I simply converted to the RAE datum/arm so that the CG location could be compared. Doing that has gotten the others whacking away at their calculators without understanding what they are doing. Consequently we have the LEMAC of the Spitfire MkV being used as the LEMAC for the Spitfire Mk IX. Garbage in = Garbarge out

I tried to explain that. Unfortunately that message was pretty much ignored. :( Now we have to see it for ourselves. The LEMAC is not 19.5 for the Spitfire Mk IX. Loading condition A Gear Down: 84in * .392 = 32.92 - 21.2 = 21.72 (7.2in + 21.72) / 84in = 34.4% MAC 84in*.314 = 26.37in - 20.7 = 5.67in 5.67-.6 for Undercarriage UP = 5.07inches Aft of Datum 5.07inches is spot on with the NACA CG location of 4.8inches. Without a change in the aircraft's AC, anywhere the stability margin is equal, the airplanes will have the same have the same stability characteristics.

Steerable tail-wheel makes some difference and can get you in trouble if relied upon too much. That being said, I find the FW-190 is a docile tail-dragger too. Both A/C require normal taildragger control input to me. DCS does an excellent job of modeling the ground handling. The control inputs on take off and landing are pretty much the same ones required for every taildragger I have ever flown in RL.

No issues... The NACA MAC is not in error, they just did not have the RAE numbers. They did it the conventional way by jacking the tail up and taking out a tape measure. First let's prove the LEMAC on the document you posted. It is listed at 19.5in. .317 * 84 = 26.6in 26.6in-19.5in = 7.128in That is a 1% error. We can say the RAE LEMAC Gear Down is 19.5in. 31.4% MAC = 6.87in aft of datum. A normal CG for the Spitfire series undercarriage DOWN. But, that is not the case for Spitfire Mk IX data, it is found undercarriage up just as the NACA MAC is located. But let's look if we use RAE Gear Down LEMAC for our 9.5: [(9.5+19.5)/84] * 100 =34.5% MAC .012/.357 = 3.4% error That does not give very good agreement with the RAE Spitfire Mk IX MAC of 35.7%. Why? Length was added to the engine compartment changing our LEMAC. Simply solving for the NACA MAC gives good agreement with the Spitfire Mk IX data. Using the RAE 84”MAC; the LEMAC is 20.7in vs 21.8in for the NACA LEMAC at 85%. It just does not matter that much and does not change the stability picture of the design at normal to aft CG. 20.7/84 = .257*100 = 25.7% 21.8/85 = .256*100 = 25.6% So no conspiracy theory required.

No, the RAE set their MAC at 84" based the RAE LEMAC. I did not solve for the RAE LEMAC...I solved for the NACA LEMAC. You could do the RAE one with that data easily. It won't change anything. The NACA LEMAC works with the NACA MAC and converts well...just don't use the NACA LEMAC with the RAE MAC. It is accounted for....

I am sorry to hear you lost your job. Go to the majors if you can, life is sooo muuuuch better.... S_P_E_E_D_B_I_R_D....

Yep

7.2lbs per gallon by the weight and balance sheet. That is probably your error. Your fuel is too light.

Corrected. There is about a 3% error in the conversion.

It was not at 7"...it was at 31.4%MAC. That is about ~5.5 inches aft of datum on the RAE scale. I did not convert the NACA location to RAE datum arm... I converted the RAE MAC to RAE datum arm once I calculated the NACA LEMAC and confirmed that LEMAC agreed with the RAE CG calculations. 31.4% RAE MAC = ~4.8 inches aft of their datum point.

Umm, the NACA actually tested at a normal CG location. It is not very far back and certainly is a location that a operational Spitfire would use....

With an empty rear tank you will have a rear CG of ~7.4in just like the RAE says. You can run the math on the weight and balance sheet I posted to confirm it. Do you know how to do it? Your figures above are wrong so I am thinking you might be doing something wrong. Once I determined the LEMAC the NACA was using, I was able to crosscheck that LEMAC with the RAE MAC computations to confirm the accuracy. Yes, there is less than an inch difference between the NACA datum and RAE. The NACA tested the Spitfire at a normal CG location. It was not some wildly aft location, just what you could see flying it.