DCS P-51D Landing Physics and Ground Handling

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.

Here is the track of Analysis video 3:

http://www.mediafire.com/download/q1ss152hsvv1k8k/P-51_Bounce_Test_3.trk

Thanks midnabreu for the rational and measure tone you've used throughout this discussion to bring up your concerns. As a simmer who wants the absolute best numbers I can get for the simulation of these aircraft I'm very happy that people will question if they feel something is missing.

FWIW, I have no clue if this CG issue is an issue or if it isn't, however I hope your well reasoned argument will get a review ... just in case. And the review shouldn't just entail "we have a bunch of Mustang pilots who said it's good" .. because a good real life pilot may not have the muscle memory for a joystick on a PC .. despite being an ace in the real thing. :)

In retrospect I recall that IL2 had a bunch of endorsements from pilots who'd flown the real deal as well. Hitting the right number and getting the feel right are both important ... therein lies the ART of simulation!

That's my take on this.

I'm not wading into the technical discussion on this thread (it's quite interesting) as I don't know enough to comment, but I'm am going to say something about midnabreu's assertions.

From reading midnabreu's posts and watching the videos, there's a flaw in the OP stating there's potentially an issue in DCS: there's an implicit assumption that A2A's version is correct.

From reading this thread, midnabreu has not conceeded the fact that A2A's version may be wrong, or may just simply as good as they could make it when taking into account FSX's limitations.

I'm not saying who is right or wrong (it's entirely possible both sims could be wrong), but there needs to be confirmation that the way A2A's works is correct before you can claim DCS' implementation is flawed.

Hitting the right number and getting the feel right are both important ... therein lies the ART of simulation!

I couldn't have said it any better in one sentence. It's not just about numbers (although they have to be correct). Simulation is truly an art-form and all the developers have my respect when they get it right... 'numbers' and 'feel' combined.

Here is the track of Analysis video 3:

http://www.mediafire.com/download/q1ss152hsvv1k8k/P-51_Bounce_Test_3.trk

At work now do I'll have a look when I get home. In the mean time, you can see my technique here (post #3 in this thread):

Even though I did use 1° nose down trim in this video, it is absolutely not needed. The main difference for me was learning where the ground is, or in other words correctly anticipating contact with the ground. Even when I am off that mark, I can cut power and center the stick slightly higher causing her to drop down - struts will absorb nicely.

If I take a few student out for a spin with a model ( disregard reynolds etc.. for now ) on a teach-student dual Transmitter setup and a fairly easy to land airplane ( high wing, low wing loading, docile ) I get 1 version of how to land per student, and with every try there is one more version.

The longer you fly, dozens and dozens of times with the same airplane, you start to produce a tactile feedback BASED ON WHAT YOU HAVE, if it is not your behind, it will be your eyesight that will notice critical changes and let you react to it.

After 10h training mostly take off and landing, you will see that most students suddenly are very alike in approach, touch down and roll out. The more you look & learn the more you get to the few left possible ways to land successfully.

I think it is the pilot and his skills, whenever I mess up the Pony it's my own fault and I usually know 3 seconds before impact what I did wrong, born out of laziness cuz its only virtual and not real, be it a model or a RL AC. There is a BIG difference on how much brain one involves in solving such situations. I can only tell about the difference of a respawnable P-51 and my 2-year Balsa glue and sand period that it took to build that plane in my logo. It costs me 180 € every time I bounce the gear and about 3 month until I get that gear back to germany from kentucky where the company sits that fixes it. 180 € gear, 40 € prop, 20 € small parts, dozens of hours fixing it, rebalance CG for-aft left-right ( lateral balance ).

It makes me think 3 x as fast and precise to land that P-47 D23 compared to any standard landing in DCS, especially VA-Server where no story is behind the flight. It somehow gets more intense when I fly back a crippled Su-25T or a Ka-50 but it never mobilizes all that brain power, concentration etc. as it does when doing it "life". That is a totally different mind set, no respawn, no 2nd chance, money involved, people in danger if you really mess it up... that makes you a totally different pilot.

Now replace model with RL-AC and you are another 5 steps higher in what your brain can do and how fast you can think compared to arm-chair pilots at 8pm after full meal and a lazy brain.

Bit

Here is the track of Analysis video 3:

http://www.mediafire.com/download/q1ss152hsvv1k8k/P-51_Bounce_Test_3.trk

The track just shows the first part of the Analysis video 3 - followed by a failed TO attempt.

I was bouncing all over the place on my landings when i first started the p-51.

The key is to do an overly pronounced flare when you're about to touch down. I thought my flare was enough but it wasn't. You really need to pull the stick back to the point where it seems excessive. That way you land on all three wheels and don't bounce.

This thread is for 2 point landing dicussions. 3 point are helpful but you have more control over the aircraft in 2 point configuration. Biggest tip I've seen and what I do is always center the stick right before touchdown. Now right before I mean that first mm of tread is about to touch. Others have said slight stick fwd and that works great too! just remember slowest possible speed, slowest descent rate and right before touchdown either stick center or slightly fwd.

We would need a real Mustang pilot tell us about his or her experiences. From my personal experience I know that most of the sims are underdone in regards to bouncing and DCS is the first one that makes the ground handling very similar to what I experienced in RL.

Firstly FSX planes are glued to the ground the moment the touch the runway surface. I have't had much chance to test A2A birds, but from what I heard they behave much more realistically.

In RL to doesn't take much to bounce. A few years ago, what still on my PPL course, sometimes I taught I flew a perfect approach to only be surprised by a big bounce on touchdown. Usually it was because I was going to fast. 10 kts was sometimes enough to make a difference.

Moreover, those warbirds were mostly operated form grass fields and these are much more forgiving. Soft ground dissipates a lot of energy, even if you screw up your landing. ;) In DCS all the runways are paved.

I watched a documentary once, about a RAF pilot who flew in Battle of Britain Memorial Flight. He was converting from Hurricane to Spitfire and I remember clearly that he mentioned landing on a paved runway as one of the most challenging in his carrier.

The issue with paved runways isn't one of energy dissipation. A grass runway is not exactly spongy, so no significant help there.

The benefit of grass w/ regards to taildraggers is that you have less friction. For a given side force, you have a significantly larger slip angle (i e the tyres go more sideways) or, to put it another way, you get less side force for a given amount of getting it sideways. You can get away with being significantly more sloppy on grass than on concrete/tarmac in a taildragger.

On the downside, many grass runways will give you a roller coaster ride to remember. When you think you have landed, the runway disappears from under you... :D

On the downside, many grass runways will give you a roller coaster ride to remember. When you think you have landed, the runway disappears from under you... :D

True. I experienced that a few times. :D

9 x [2 point] landing demonstrations

HERE IS MY TRACK (right click & save as)

- Rudder trim used only on initial TO. No trim on all landings / following TO.

Featuring deliberate hard landings:

1. RW 04: hard landing on usually normal approach (neutralized the stick too soon / high)
   
2. RW 22: bounce and recovery (neutralized the stick too late, shallow approach)
   
3. RW 04: dropped her really hard, similar to no.1 (this time >500 ft/m descent upon touchdown)
   
4. RW 22: similar to no. 2, unable to recover - go around
   
5. RW 22: same approach, slightly faster speed - neutralized the stick in time
   
6. RW 22: again, same approach, similar to no. 4 - but this time I showed the stick forward, not just neutral
   
7. RW 04: again hard landing
   
8. RW 22: another hard landing and gear finally gave in, right wheel did not retract
   
9. RW 22: small bounce, was more focused on the gear and making sure it locked
   

^^

Featuring VH-ROCK's awesome Gunfighter skin.

EDIT: After some more analysis on my end, I came to the conclusion that bouncing occurs when trying to land at too low speed and at a very shallow angle. In such an approach the AoA quickly becomes too high and the tail will want to drop down thus causing the undesired "balooning" effect. This needs to be counteracted with shoving the stick forward upon or moments before touchdown to prevent the tail going down and changing AoA. With heavier loaded P-51D best approach speed is between 130-140 MPH indicated and not cutting the power until the wheels are securely on the ground. Normal or steeper approaches are more forgiving allowing you only to neutralize the stick for a two pointer.

^^

Featuring VH-ROCK's awesome Gunfighter skin.

Thanks bud, glad to know they're used and appreciated

Thanks midnabreu for the rational and measure tone you've used throughout this discussion to bring up your concerns. As a simmer who wants the absolute best numbers I can get for the simulation of these aircraft I'm very happy that people will question if they feel something is missing.

Thanks bro, my rational my be completely wrong, but my intuition as a (very low time PPL) pilot and long time flight simmer is usually right when it comes to judging the "feeling" of flight. Again, this may be completely pilot error and I certainly want to find out to improve my skills with the Mustang, but if there is something amiss with the flight model, I want to ultimately help the community (and my DCS Mustang of course :thumbup:).

Thanks for the compliment, just trying to keep it professional for the community and not be a whining critic who is unsympathetic to the hard work DCS has put into this model. There are enough naysayers and hard core self proclaimed experts out there.

Crashing and burning in flight sims since 1984 ...

:joystick: I love your signature man! 1984. Wow, I've been doing flight sims since 1996 and I thought that was a long time. :pilotfly:

but it never mobilizes all that brain power, concentration etc. as it does when doing it "life". That is a totally different mind set, no respawn, no 2nd chance, money involved, people in danger if you really mess it up... that makes you a totally different pilot.

 

Now replace model with RL-AC and you are another 5 steps higher in what your brain can do and how fast you can think compared to arm-chair pilots at 8pm after full meal and a lazy brain.

 

 

Bit

I appreciate what your saying BitMaster, there is certainly an inherent "brain laziness" in sims because although really immersive, you ultimately know its a sim. Virtual reality helmets like the Oculus Rift might change that with augmented reality immersion as documented in this video: https://www.youtube.com/watch?v=4xiV5Y4nhQE

Because the peripheral vision is surrounded by the virtual pit, ones brain feels more like its really in an aircraft.

From reading midnabreu's posts and watching the videos, there's a flaw in the OP stating there's potentially an issue in DCS: there's an implicit assumption that A2A's version is correct.

 

From reading this thread, midnabreu has not conceeded the fact that A2A's version may be wrong, or may just simply as good as they could make it when taking into account FSX's limitations.

 

I'm not saying who is right or wrong (it's entirely possible both sims could be wrong), but there needs to be confirmation that the way A2A's works is correct before you can claim DCS' implementation is flawed.

Buzzles, your right, theories usually come with an assumption, and my assumption or rather (my hypothesis) is that the A2A is correct and the DCS is wrong. However, hypotheses are proven wrong often, but sometimes they are right. I am very aware of FSX limitations which is why I fly IL2, DCS and BMS far more often because of the "feeling flight in these sims. However, A2A does incredibe work and they have created extremely realistic models tested by real pilots as well.

I am open to criticism I am just pushing a challenge based on this theory and what I feel needs to be corrected. Again, I may be totally off here, but its worth exploring.

We would need a real Mustang pilot tell us about his or her experiences. From my personal experience I know that most of the sims are underdone in regards to bouncing and DCS is the first one that makes the ground handling very similar to what I experienced in RL. ...

Agreed. All other sims I've tried are very forgiving. Only in DCS I've experienced ground loops and balooning/bouncing. Once you follow said procedures and technique on how to fly tail draggers DCS is enjoyable in that regard alone. Can't think of any other sim I've had so much fun simply TO and land lol.

^^

 

 

Thanks bud, glad to know they're used and appreciated

You are welcome. One of my favorite skins btw.

Okay looks like I'm not the only one that has fun taxiing in DCS. Once you get the hang of the toe brakes and pulling the stick back to lock the tail wheel it's really fun.

The track just shows the first part of the Analysis video 3 - followed by a failed TO attempt.

This is the track for Analysis video 2:

http://www.mediafire.com/download/1zx6dt2zuevgcka/P-51_Bounce_Test_2.trk

EDIT: After some more analysis on my end, I came to the conclusion that bouncing occurs when trying to land at too low speed and at a very shallow angle. In such an approach the AoA quickly becomes too high and the tail will want to drop down thus causing the undesired "balooning" effect. This needs to be counteracted with shoving the stick forward upon or moments before touchdown to prevent the tail going down and changing AoA. With heavier loaded P-51D best approach speed is between 130-140 MPH indicated and not cutting the power until the wheels are securely on the ground. Normal or steeper approaches are more forgiving allowing you only to neutralize the stick for a two pointer.

Thor,

I did check out your track video and you have some excellent landings. Thank you for taking the time to record and upload it.

I still think this could be a CG/touchdown/elevator down-wash issue or my pilot in-experience, but I will keep testing and will implement this constitutive criticism. I will certainly attempt your techniques for the higher approach with a normal glide-slope, not cutting the power until wheels touch down seems like it would provide sufficient airflow over the elevator to keep the tail up.

Thanks again for the feedback and analysis.

Following Thors advice above, the Mustang will perform a smooth 2 point landing at the higher 150mph airspeed leading me to believe that the nose will not come down at Pilots Operating Handbook recommended approach speed of 100-120mph due to a elevator down-wash issue/maybe aft CG issue. Seems like the extra speed causes sufficient airflow to keep the nose down.

Like THOR stated, a heavily loaded Mustang probably does need more speed on approach like any other aircraft to maintain the same AOA on landing.

The fact that the Mustang doesn't bounce at a higher than recommended approach speed is interesting, as real world experience says that excessive speed or decent rate should in fact cause a bounce. Nonetheless, we have a workable solution until DCS looks at this phenomenon.

And again I will say, this could be pilot in-experience/error.

Here is my final conclusion, Appreciate Thors and everyone elses input on this journey. :smartass::thumbup:

Thank you for comments, I am glad to see it works for you. :)

This is the video where I picked up the "hold power until wheels on the ground" technique:

A couple of thoughts to this discussion:

• TF-51D in my experience will land a two wheeler at about 130 MPH approach speed with touch down at about 110-120 - which nicely correlates with the recommended procedure.
  
• P-51D being about ~1200lb (+573lb for combat eq. and 718lb for ammunition) heavier with ammo, armor and fuel tank in the back requires as you noted 150 MPH approach speed with a touch down at about 130-140 MPH.
  
• Seeing how Mustang can carry a lot of fuel and even with wing tanks 50% full this translates to a lot of weight (don't forget ammunition weight). I haven't yet tested the P-51D without ammo and with 10-20% fuel to see if there is a difference (as in simulating a landing after a combat mission).
  

In the video I linked here, you can see the approach angle, together with more or less curved in or turn to short final - this enables you to keep a runway in sight much easier.

As far as recommended 115-120 MPH approach speed, the way I read it - it is for a 3-point attitude landing (page 58.): https://www.scribd.com/doc/34811808/North-American-P-51-Mustang-Pilot-Training-Manual

Please note the comments on stick movement about "Bouncing" (page 61.), in addition to the "Forcing the tail down" section which is related to the two wheel landing. Also, page 62. says that you should always make a three point landing.

EDIT: After watching your video again, I see that you are approaching shallower than I do. Thus using +30" of manifold. If you check again my track, you will see that I never use more than 10-20".

Thank you for comments, I am glad to see it works for you. :) This is the video where I picked up the "hold power until wheels on the ground" technique:

 

 

As far as recommended 115-120 MPH approach speed, the way I read it - it is for a 3-point attitude landing (page 58.): https://www.scribd.com/doc/34811808/North-American-P-51-Mustang-Pilot-Training-Manual

 

Please note the comments on stick movement about "Bouncing" (page 61.), in addition to the "Forcing the tail down" section which is related to the two wheel landing. Also, page 62. says that you should always make a three point landing.

Excellent power on video, very nice landing. I noticed that almost every airshow P-51D approach Ive seen is a two pointer. Just seems like its much easier like MagnumHB (http://forums.eagle.ru/showpost.php?p=2193337&postcount=39) stated with the forward visibly its much easier to approach and land.

I think your right, the heavier weight corresponds to a higher approach speed, just like an F-16 or a 737, so it should be no different in the Mustang. The POH does mention a 115-120 mph approach speed, but I can imagine they would assume that an Mustang would come back in WWII with full ammo an full fuel. So at the lower weight, 120 mph may be just fine and may not produce a bounce.

I do still notice that the DCS Mustang produces a significant bounce in a 3 point configuration. The POH does recommended 3 pointers for a normal approach, unless there is wind over the runway. So I still think theres something weird with down-wash, elevator neutral state, or CG.

One place where this is really apparent is on take off. The nose should naturally come down on take off after significant speed is built, especially with an empty aft tank. The DCS Mustangs nose refuses to come down without deliberate and forceful nose down on take off.

The higher approach speed absolutely gives us the proper elevator authority, and allows the Mustangs nose to come down, but I would still like to see this addressed officially by DCS devs. :smilewink:

Please note the CAUTION on page 66, and notes about the fuselage tank and reversibility on the next page. With the mentioned fuselage tank over 50% full the plane is unusable for nothing but straight and level flight - and impossible to trim.

I understood the manual always recommending 3 point approach due to shorter landing on short improvised airstrips. There is no recommended landing speed approach for a two point landing. All mentioned landing recommendations are for 3 point attitude.

IIRC TF-51D will lower the nose once you gain speed on take off roll, and the nose will want to fall down after you gear up in P-51D.

With all this said, I am more inclined to believe this is where A2A's recommendation for nose down trim comes from and that DCS has modeled this correctly.