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DCS P-51D Landing Physics and Ground Handling


midnabreu

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Sorry, but you are deeply wrong... there is a great, profound difference between the tricycle gear plane and the tail dragger. The difference is in their CG position. As you can see, the taildragger has it aft the main wheels, tricycle - forward. (Why am I explaining it... there are a lot of sites where taildragger guru tell the same!).

 

Yes I understand about CG Yo-Yo, thank you for clarifying this point because its important.

This is very counter-intuitive to tricycle gear pilots like myself who are taught to hold full gradual back pressure upon touch down.

 

 

type 1 to pitch-down reducing AoA and lift and pitch-up..........Type 2 requires stick forward light movement at touchdown to glue the plane to the ground. Some risky guys even use to brake wheels a little before touchdown

 

This make the absolute difference. I always thought to just neutralize the elevator upon touch down, and never to push/shove/force the nose down upon touchdown to "glue" it to the ground because of fear of nosing over. I noticed last night while watching the Mustang 2 point landings demonstrated that pilots would purposefully "push" "shove" the nose down past neutral upon making contact with the ground. If this is proper technique then I want to learn it :smartass:

 

 

 

I did some testing and the P-51D Mustang requires significant nose forward on contact with the ground (the TF-51 can be neutralized with full flaps and it "sticks")

 

There will be a final analysis video demonstrating these techniques.

 

Yo-yo, thanks for the wise insight and critique. :thumbup:


Edited by midnabreu
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You are welcome!

Yes, the only difference with TF-51 and P-51 is their weights at the same fuel quantity UNTIL YOU BEGIN TO FILL THE FUSELAGE TANK (68%) not only increasing the weight but moving CG aft.

 

You can gradually test 2-point landing starting from TF-51 7% (typical for airshow landings), 50%, then P-51 50% , 80% (!) and 100%.

 

By the way, Dora was landed in RL exclusively in 3-point attitude because of increased wheels-CG distance in comparison to English and American planes.

But in DCS some guys are happy to perform wheelers in Dora (not me, though, I find it very difficult in comparison to Mustang, possibly due to poor framerate at my rig :)).

 

I remembered the video

 

THe slightest pulls of the stick just after touchdown causes tail-down rotation and bouncing/ballooning.

 

In this channel you can find several examples of landing.


Edited by Yo-Yo

Ніщо так сильно не ранить мозок, як уламки скла від розбитих рожевих окулярів

There is nothing so hurtful for the brain as splinters of broken rose-coloured spectacles.

Ничто так сильно не ранит мозг, как осколки стекла от разбитых розовых очков (С) Me

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But in DCS some guys are happy to perform wheelers in Dora (not me, though, I find it very difficult in comparison to Mustang, possibly due to poor framerate at my rig :)).

 

Guilty! :joystick:

 

I don't find it any more difficult than P-51D. Must be your FPS then.

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i think in dcs some things are overdone.

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You are welcome!

Yes, the only difference with TF-51 and P-51 is their weights at the same fuel quantity UNTIL YOU BEGIN TO FILL THE FUSELAGE TANK (68%) not only increasing the weight but moving CG aft.

 

You can gradually test 2-point landing starting from TF-51 7% (typical for airshow landings), 50%, then P-51 50% , 80% (!) and 100%.

 

THe slightest pulls of the stick just after touchdown causes tail-down rotation and bouncing/ballooning.

 

 

Yo-Yo, I discussed this with a P-51D owner and I am almost certain like you stated its related to the dreaded CG modifications inflicted by the aft center line tank.

I was aware of this phenomenon for the WWII era P-51, but apparently DCS is modeling this nightmare aft CG phenomenon, hopefully accurately.

 

 

FLIGHT CHARACTERISTICS (Page 101)

As new equipment was added to the aircraft over the course of its development, in particular the radio equipment and the fuselage tank installed aft of the cockpit, the center of gravity (CG) has been moved back. This has resulted in decreased back pressure required to move the control stick. Instead of a force of 6 lbs. per G of acceleration, the required force in the P-51D is only 1 ½ lbs. Additionally, the stick forces begin to reverse as acceleration exceeds 4G. Great care must be taken not to black out or over-stress the airframe in sharp pulls and turns.

 

Special Flight Conditions (Page 107)

Full Fuselage Tank

Special care must be taken with the control stick when the fuselage tank contains more than 25 gallons of gas. In such cases, the flying characteristics of the aircraft change considerably – increasingly so as the amount of fuel in the tank is increased. When carrying more than 40 gallons of fuel in the fuselage tank, it’s necessary to avoid any high performance maneuvers. The fuel weight shifts the CG back, making the aircraft highly unstable during maneuvering (I might add during take off and landing as well).

 

Also note, "are NOT permitted unless the fuselage tank contains less than 40 gallons of fuel or if external fuel tanks and/or bombs are carried. An 85 gallon fuselage fuel tank is located aft of the cockpit"


Edited by midnabreu
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Depending on AC, skill and knowledge some pilots on certain planes employ tactics you would not consider unless explained why & how this works.

 

CG is not a static point, it is rather a span with max forward and max aft positions. It does shift during flight due to fuel burn, dropped ballast and rounds fired. The more you get rid off of anything the more your CG usually shifts back as the plane is balanced dry/empty and upside down if a low-wing design. It would never stay in balance upright since the CoM is above the wing.

CoM and CoG are 2 different things you should know about when talking about finding your CG and it's limits. The hard coded CG is the absolut max aft position you can still control the airplane, any pound added aft will render the AC uncontrollable by design, you would need a FbW system to keep control, if at all. You can add literally as much weight as you want to the nose up to that point where you have difficulties on the strip to get fast enough to have enough pressure on your elevator so you can lift the nose, that is the only physical limit to forward limits of CG. Usually you get rid off all that ballast during flight and upon landing your CG is far enough backwards so that you have authority over AoA by elevator. If you are a bit nose heave you have to come in faster to have more pressure on the elevator and look for a LONG RUNWAY. If you are way too heavy and your elevator can't induce enough pressure down to lift the nose you will end as a lawn dart, no way out.

 

The best way to land a tail dragger is a 3-point landing with an induced stall 1 foot above the tarmac combined with full UP elevator after touch down to break each and any lift that could build up. You will find that your stick is almost all the way back when slowing down and nose high anyway, due to less efficiency while slow you have to pull way more stick compared to normal speed, the closer you get to stall speed the more you pull to have the same lift-my-nose momentum. The skill is to time the actual drop due to stalling with that 1 foot above tarmac.

Too high and you will bounce..Monday-Tuesday-Weednesday or even worse, cause the plane to rotate around the fuselage and have a wing-tip stall --> disaster. You pulled too much too high above the tarmac.

 

You only land 2-wheeled if either the plane makes it hard to flare for some reason, be it design or config/damage/skills or if you have to come in fast for any reason. The difficulty on 2 wheeled landings is that your speed that you touch down with is the same that you lift off with, now figure what will likely happen if you gain any AoA upon touch down. It is a lot harder to have 2 wheel landings without trouble than a 3-point landing, just because of the bouncing.

 

Talking about it and doing it are also 2 different things, it takes practice practice and more practice and some self criticism to keep learning.

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This is why I wish we had a cg plot in the aircraft configuration screen like we have for the weight. It would tell us where the cg is for the chosen loadout and how close we are to the aft or forward limit. It is the duty of the pilot to know the configuration of his aircraft's weight and balance. It would be great to show the weight/cg burn line to show the weight and cg shift with fuel burn and with and without weapons. It would be nice to have that in dcs mission planning.


Edited by Buznee
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Im not even going to get into the things you high light other than the fact that I have witnessed first hand 11+ full time display pilots who fly the Mustang and have said that the modelling is accurate.

 

Also see this thread:

 

http://forums.eagle.ru/showthread.php?t=111388

 

Sorry to say it but your experience in a nose wheeled Cessna is almost irrelevant, the only time in my flying I have found anything close to relevant is when I fly the super cub.

 

Pman

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Thank you midnabreu for starting this thread, and to everyone that replied in a positive manner. Reading the responses taught me a lot about landing these tail draggers and the role of CoG at the point of touchdown.

 

Until now I'd basically figured out the three point landing for myself from a comment I heard or read in the past where the phrase that stuck was "hang it then drop it". However. I could never figure out how to do the two-point landing because I didn't realise that what was happening was the momentum dragging the tail own and increasing AoA resulting in ballooning. It's trivially obvious really but I was just being an idiot and not thinking it through.

 

For those of us who are less in the know the conversation (and many invaluable accompanying videos) has proved to be very enlightening indeed.

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CoM and CoG are 2 different things you should know about when talking about finding your CG and it's limits.

 

You are right that there is a difference between mass and gravity center, but that only applies to flight way out the gravity field... CoM and CoG are interchangable in atmospheric flight

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As others pointed, the techniques used for landing a tricycle plane like Cessna 172 you can throw out a window when landing a tail dragger. A buddy of mine flies both, these are his comments when I asked him about comparison:

 

For reference, my tailwheel time is in a Citabria Explorer, so mileage may vary, especially when compared to a much heavier, more powerful warbird. Anyway, when taking off, you start with the stick held full back (or to the left/right rear corner of its travel in the event of crosswinds) to keep the tailwheel locked (I believe this is how the P-51 and 190D are modeled in DCS.) and smoothly but quickly go to full power. Generally speaking, you need to be much more active on the rudder in a tailwheel than you do in a nosewheel, so I don't remember if that exact phenomenon of initial pressure and release occurs, because it's also blended in with just keeping everything pointed the way it is supposed to be. Once you get a little speed, you push the nose down and get into a level attitude, again with a lot of rudder activity. Shortly after that, you will notice that the plane will start to become light on the wheels, and you can take off almost just by releasing the forward stick pressure, although we always climbed out at a relatively aggressive rate compared to a 172.

 

 

On another note, I don't think P-51 was designed to carry that fuel tank in the back. Hence such a CoG shift and the reason to drain it first after take off (you take off with left wing fuel tank - always). If you think the empty fuel tank is a CoG problem, try taking off with it half or full. :)

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WWII bomber formations | DCS P-51D: [TEST] TO distance / gross weight / temperature

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As others pointed, the techniques used for landing a tricycle plane like Cessna 172 you can throw out a window when landing a tail dragger. A buddy of mine flies both, these are his comments when I asked him about comparison:

Speaking of which...

 

You only land 2-wheeled if either the plane makes it hard to flare for some reason, be it design or config/damage/skills or if you have to come in fast for any reason. The difficulty on 2 wheeled landings is that your speed that you touch down with is the same that you lift off with, now figure what will likely happen if you gain any AoA upon touch down. It is a lot harder to have 2 wheel landings without trouble than a 3-point landing, just because of the bouncing.

It is true that wheel landings can be more challenging in some respects, but they do have some advantages that you may or may not be aware of. Primarily, the slightly higher approach speed is desirable in gusty wind conditions, and in general allows you to retain more control authority. There is a definite mushiness in the Citabria at a 3-point approach speed that is not there when coming in slightly faster for a wheel landing. Another good reason for doing wheel landings is improved visibility over the nose/down the runway. Something else to consider is that the tailwheel is relatively fragile compared to the mains, and it is generally a good idea to minimize extra stress on it, although this is less important in a sim.

 

Of course, the key to a good wheel landing is to have an appropriate descent rate and to pop the stick forward as soon as the mains make contact with the ground to avoid a bounce. This certainly takes some practice (in the about 60 landings it took to get my endorsement, maybe only 10 or so were 3-pointers because they are generally easier), but the results are well worth it, as a properly executed wheel landing just feels much more solid and satisfying than even the best 3-pointer.

 

All of that being said, it's worth mentioning that the best type of landing for any given situation depends heavily on factors such as wind conditions, runway surface, and aircraft type.

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Im not even going to get into the things you high light other than the fact that I have witnessed first hand 11+ full time display pilots who fly the Mustang and have said that the modelling is accurate.

 

Also see this thread:

 

http://forums.eagle.ru/showthread.php?t=111388

 

"Well, At Duxford's Flying Legends airshow this year, we finally got around to getting the real Horsemen to try out DCS P-51. To say they were impressed was an understatement! Ed Shipley & Dan Friedkin put the Mustang through it's paces, tried stalls, loops and compared the facts of figures of DCS to the real thing"

 

Sorry to say it but your experience in a nose wheeled Cessna is almost irrelevant, the only time in my flying I have found anything close to relevant is when I fly the super cub.

 

Pman

 

The Horsemen tried stalls and loops, but did they try takeoffs and landings? (I'm not being sarcastic, this is what the topic states, just curious).

 

Real life flying of any sort is not irrelevant. I understand a Cessna 172 is a far cry from a powerful Mustang, but the feeling of flight and intuition of what feels right is there.

I am a beta tester for A2A, and I did some tests on the A2A C-172R and found that upon take off and landing the nose would continue to rise, I was told that my 172P experience had no relevance to the R model.

 

I keep challenging that the aircraft just did'nt "feel" right. Turns out the elevator downwash was coded in reverse and it was causing the nose to rise instead of fall during the round out.

 

My point is that your right, I am not a Mustang pilot or owner, but something doesn't "feel" right about the CG in the Mustang. If it bounced this severely during WWII, we would have alot of crashed Mustangs. I have not read or seen documentaries from WWII pilots stating that the aircraft had a severe bounce to be careful of. They did talk about the Mustangs inherent ability to snap roll during an accelerated stall, but never about this dreaded bounce. WWII pilots also mention the aft CG issues that the Mustang experienced with the aft tank full which is why they eventually took it out of the F-51D as far as I know.

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The Horsemen tried stalls and loops, but did they try takeoffs and landings? (I'm not being sarcastic, this is what the topic states, just curious).

 

Real life flying of any sort is not irrelevant. I understand a Cessna 172 is a far cry from a powerful Mustang, but the feeling of flight and intuition of what feels right is there.

I am a beta tester for A2A, and I did some tests on the A2A C-172R and found that upon take off and landing the nose would continue to rise, I was told that my 172P experience had no relevance to the R model.

 

I keep challenging that the aircraft just did'nt "feel" right. Turns out the elevator downwash was coded in reverse and it was causing the nose to rise instead of fall during the round out.

 

My point is that your right, I am not a Mustang pilot or owner, but something doesn't "feel" right about the CG in the Mustang. If it bounced this severely during WWII, we would have alot of crashed Mustangs. I have not read or seen documentaries from WWII pilots stating that the aircraft had a severe bounce to be careful of. They did talk about the Mustangs inherent ability to snap roll during an accelerated stall, but never about this dreaded bounce. WWII pilots also mention the aft CG issues that the Mustang experienced with the aft tank full which is why they eventually took it out of the F-51D as far as I know.

Yea they did, as has Stephen Gray, Nick Gray, Alan Wade, Steven Hinton, Matt Nightingale, Steveo Hinton (Current Reno champion, in a mustang), Brian Smith, Carl Schofield and Pete Kynsey to name current display pilots who I've witnessed first hand take off, fly and land the Mustang

 

Those are just the names off the top of my head and don't include non display authorised but Capable Mustang pilots.

 

So it may feel wrong to you but I'll take thier word for it especially when Nick know more about Dcs then I do as well lol.

 

Re the rear tank, most were removed after they were sold from the military, 99% of the single sticks kept the tanks while in active service iirc

 

Pman

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Yea they did, as has Stephen Gray, Nick Gray, Alan Wade, Steven Hinton, Matt Nightingale, Steveo Hinton (Current Reno champion, in a mustang), Brian Smith, Carl Schofield and Pete Kynsey to name current display pilots who I've witnessed first hand take off, fly and land the Mustang

 

Thanks Pman, so did they comment on the Mustangs tendency to bounce on landing? In the original WWII POH, the Manual talks about pilot induced oscillation, but does not warn about the Mustangs inherent bounce on a 2 point landing.

 

Like I demonstrated, I can land the Mustang in a 2 point landing with immense amount of downward trim, but is this accurate according to the real Mustang pilots?

 

(I also noticed these guys are using the Warthog HOTAS, I know hardware has alot to do with feel, and this accounts for the level of precision and sensation of weight)


Edited by midnabreu
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Thanks Pman, so did they comment on the Mustangs tendency to bounce on landing? In the original WWII POH, the Manual talks about pilot induced oscillation, but does not warn about the Mustangs inherent bounce on a 2 point landing.

 

Like I demonstrated, I can land the Mustang in a 2 point landing with immense amount of downward trim, but is this accurate according to the real Mustang pilots?

 

 

They didn't bounce it on landing, so had no reason to comment (Yes, I was present too). If you land her right, there really is no issue at all.

 

Personally, I land with neutral trim and 9/10 times, I do not bounce. As soon as I touch down, centre the stick.

Virtual Horsemen - Right Wing (P-51)  - 2008... 

Virtual Ultimate Fighters - Lead (P-47) - 2020...

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They didn't bounce it on landing, so had no reason to comment (Yes, I was present too). If you land her right, there really is no issue at all.

 

Personally, I land with neutral trim and 9/10 times, I do not bounce. As soon as I touch down, centre the stick.

 

Right rock, that is exactly what I do just like in the A2A and in IL2. I center the stick, and as long as speed and decent is reasonable, we shouldn't get a bounce. When I center the stick in the DCS Mustang, I get a bonce no matter the speed or decent rate as demonstrated in the videos.

 

I need to use deliberate and forceful nose down to "stick"/force the aircraft on the ground .

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Right rock, that is exactly what I do just like in the A2A and in IL2. I center the stick, and as long as speed and decent is reasonable, we shouldn't get a bounce. When I center the stick in the DCS Mustang, I get a bonce no matter the speed or decent rate as demonstrated in the videos.

 

I need to use deliberate and forceful nose down to "stick"/force the aircraft on the ground .

 

Then there is something going amiss with your specific copy of DCS. It works 90% of the time for me and, when it doesn't, it's always because I've come in 'too hot'. I always aim to touch down at around 90-100 for a two point landing and aim to have a decent rate of less then 500fpm

Virtual Horsemen - Right Wing (P-51)  - 2008... 

Virtual Ultimate Fighters - Lead (P-47) - 2020...

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Thanks Pman, so did they comment on the Mustangs tendency to bounce on landing? In the original WWII POH, the Manual talks about pilot induced oscillation, but does not warn about the Mustangs inherent bounce on a 2 point landing.

 

Like I demonstrated, I can land the Mustang in a 2 point landing with immense amount of downward trim, but is this accurate according to the real Mustang pilots?

 

(I also noticed these guys are using the Warthog HOTAS, I know hardware has alot to do with feel, and this accounts for the level of precision and sensation of weight)

 

 

I use plenty of aft trim in landing and don't seem to have much trouble with bounces. Here is a internal and external of a wheel landing with a 10m/s crosswind from the left and it seems to stick pretty well as long as the speed is under control.

 

 

 


Edited by Cool-Hand
youtubes links

[sIGPIC][/sIGPIC]

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Right rock, that is exactly what I do just like in the A2A and in IL2. I center the stick, and as long as speed and decent is reasonable, we shouldn't get a bounce. When I center the stick in the DCS Mustang, I get a bonce no matter the speed or decent rate as demonstrated in the videos.

 

I need to use deliberate and forceful nose down to "stick"/force the aircraft on the ground .

 

After reading your posts I got up in the Mustang and did some 10 TO and landings, all with a different approach. Not once did it bounce on me even when I "slammed" her onto the runway.

 

Neutralizing the stick works for me every single time. No trim needed. The only way we will know whats wrong if you post a track.

P8Z68 | 2500k @ 4.5 | GTX 1080Ti | 2x8 GB @ 1600 | TM Hog (extended 7cm) & MFG Crosswind (S/N 007) | TIR v5

WWII bomber formations | DCS P-51D: [TEST] TO distance / gross weight / temperature

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