PMDG 737 flight model question

[threexgreen 3,139]

5 hours ago, Greazer said:

It has nothing to do with "landing technique"

It has everything to do with with the 737's having an extremely unrealistic flight model.  There are Zero 737's that will will Immediately reverse descent at 20 feet and initiate a Climb on IDLE Thrust. To suggest otherwise proves you have Zero knowledge of aircraft physics.

Sorry, but it absolutely does. You don't quite seem to understand why landing technique matters. It's very hard to make it climb in a low energy state at thrust idle, so what you're describing shouldn't happen like that, at least not as easily as that. However, if there is some energy left it can climb a little bit on idle, especially with a strong headwind. If you come in hot (excess energy), you can absolutely still overflare and achieve a positive rate for a moment, even at idle. Idling thrust doesn't equal an instant state of zero energy. The thing has momentum.

That said, from countless flights with the PMDG in P3D and MSFS I can say it doesn't exhibit the behavior you're describing. If you're stable at around -700 fpm at normal pitch, initiate flare at 30 feet by raising the nose two to three degrees max, retard throttles at 10 feet, and increase back pressure to counter the nose drop and maintain flare pitch you're going to nail the touchdown at around -100 to -150 fpm. There is no tendency to float, much less climb. That can only happen with excess energy or by overflaring (disregarding environmental factors for simplicity). That's why I said maybe check your landing technique. If you can make it climb that easily it has a whole lot of energy that shouldn't be there under normal circumstances.

Edited February 26 by threexgreen
added minus to -700 fpm for clarification.

[Greazer 1,321]

737 has too much weight to start a climb on Idle power!

The only way to prove me wrong is to provide evidence of at least One real YouTube video of a 737, or any airliner starting a climb on Idle power, that is Not a go around!

[BrianW 124]

oh my 🍿

 

737 NG Flight Crew Training Manual
Avoid rapid control column movements during the flare. If the flare is too abrupt
and thrust is excessive near touchdown, the airplane tends to float in ground effect.
Do not allow the airplane to float or attempt to hold it off. Fly the airplane onto the
runway at the desired touchdown point and at the desired airspeed.

Edited February 26 by BrianW

[ianb2469 55]

It’s not starting a climb at idle power though, it’s carrying energy from the descent isn’t it? It wouldn’t be a sustained climb mind you. 

[threexgreen 3,139]

13 minutes ago, Greazer said:

737 has too much weight to start a climb on Idle power!

The only way to prove me wrong is to provide evidence of at least One real YouTube video of a 737, or any airliner starting a climb on Idle power, that is Not a go around!

... so you're saying there are go-arounds on idle power? 

Come on, no one is claiming an airplane will climb - like actually climb far out - on idle power, just like your car isn't going to go uphill without hitting the gas. But your car will still keep rolling forward for a bit if you go uphill and take your foot off the gas - it's not going to slam to a halt. It carries energy. An airplane, especially a 130k lbs 737, isn't going to lose all its energy the second the engines hit idle (which is flight idle - so you're not actually even fully at idle). If you carry excess energy or overflare there is still energy left to translate into a short climb even at idle (we're talking seconds). If you're applying correct landing technique and fly a nice flare with engines at idle - you're right, it's not going to climb and you actually have to keep it from dropping its nose. This is exactly the PMDG does, and if you're easily making it climb instead you're carrying excess energy, hence landing technique matters.

It's not rocket science, and a real 737 pilot already gave you all the evidence you need. But it seems you just ignore all of that and keep pushing your narrative that the flight model is junk, so carry on.

[Stearmandriver 2,296]

6 hours ago, Greazer said:

There are Zero 737's that will will Immediately reverse descent at 20 feet and initiate a Climb on IDLE Thrust.

And how many of them have you flown, to prove this?  ;)

[Donstim 109]

8 hours ago, lwt1971 said:

And this is on MSFS 2020.. with 2024 it'll only get better as MS/Asobo revamps the flight dynamics/physics engine and also provides much requested capabilities/flexibility in the SDK for aircraft developers. Some of the 2024 rework such as addressing the one real problem area currently in the MSFS FDE, ground handling, is now partially backported to MSFS 2020 and will release with SU15. PMDG and other devs all plan on taking advantage of this new ground handling in their FMs soon after, so keep an eye out for that in future fix updates.
 

Keep in mind that both CFD and the new ground handling parameters of SU 15 can still have issues that make them either unnecessary or unsuitable for at least some airplanes. The A32NX does just fine, in fact better, without CFD than with. In preliminary tests so far with SU 15, the new ground handing parameters do not appear to adequately replace or improve upon what can already be done pre-SU 15.

[sd_flyer 6,045]

2 hours ago, Stearmandriver said:

And how many of them have you flown, to prove this?  😉

How dare you ? He flown many hours on a passenger seat. He also  has extensive  knowledge “airplane physics” !  His PhD thesis was in “too much weight vs idle trust “ 🙂

[Stearmandriver 2,296]

Guy needs to watch a Bob Hoover performance... Thrust is only one part of the energy equation, and not the most important part 😉.

[CanadaOne 36]

Well I certainly didn't mean to start a heated discussion, just wanted to know if the plane "felt good" when flying. And it does. The plane feels tight, both in the way it flies and how things work in the cockpit. 

Just had a great night hop from Montreal to Toronto, learning some of the systems, listening to a podcast in the background, very mellow. Good fun. Landing wasn't perfect, but smooth enough.

[Greazer 1,321]

 

Pilot is late to flare 737 and pulls back quick on yoke.

Does the aircraft suddenly climb immediately?

No! Because of Idle thrust. There is slightly lesser hard landing.

If this was Pmdg 737 it would have ballooned up!

Zibo would not do that. 

[Mike_CFII_MEL 789]

22 hours ago, Stearmandriver said:

Oh my friend, if I had a nickel for every time I've seen someone balloon a 737....

A little bit too abrupt of a flare, a few knots of mismanaged energy, and that semi-critical airfoil skips right off ground effect.

Zibo is a great freeware project and so I never like to say anything negative about that project, but if we're comparing flight models... Well, there's no comparison.

There are so many things in the PMDG that are so good, but most people will never even know about unless they can recognize it from the real airplane.  

The PMDG 737 flight model is very good.  Their engine out / V1 cut performance is the best I've seen in any sim aircraft.  

I know people like to nerd out on the Zibo and for freeware it IS incredible... But it's definitely not the same level.

I may not be typed rated in the 737 but I've spent time in multi million dollar simulators and I cannot get my 100K flight deck to mimic that of the multi million dollar sim using MS2020, it is achievable using X-Plane 12 and the Zibo Mod.

I may have lost a few steps due to my health, but I can easily see the zibo-mod as being superior between the two offerings. No fault of PMDG, they have to work within the limits of MS2020 base platform!
 

Edited February 27 by Mike_CFII_MEL

[ha5mvo 254]

There are better ways to evaluate the fidelity of a FM than examining the landing. There are just too many variables involved, too few of which can be reliably quantifiable!

A better approach would be to run easily reproducible tests with published set of data. A good example can be the unreliable airspeed procedure for instance. 

Climb or descent rates under standardized conditions can also provide objective and reproducible information to be compared against published data.

If, for example, a loaded airbus is pitching to 20 degrees on takeoff then you know something's wrong - even if you've heard some youtuber pilot telling you it's "great"!

[g-liner 388]

23 hours ago, abrams_tank said:

Thanks!  Good to know that from a real 737 pilot!  I guess the PMDG 737 is really that good 👍.

Parts are good, other parts aren’t. Remember it’s the poster you’re quoting that nearly got banned from the PMDG forum for pointing out some of the failings in the 737.

I think the PMDG 73 is good and was the bar to achieve but it’s been left behind now by other developers especially on Boeings with the ability to fly RNP ar approaches and rf legs etc.

PMDG seem to me, to be a company that made something great in the past and then haven’t improved it and are just focusing on churning out the same old content on each new sim or the developer that did much of it left and they don’t know how to fix all the things that aren’t right that people now are increasingly pointing out. 
 

The noise and reaction from PMDG seems to indicate the new 777 will just be a rehash of previous versions and still have the same old LNAV, this might be ok for people who aren’t that bothered by realism or don’t want it for more focused training but it’s a real shame they’ve given up on improving their products and instead are focusing on sales of the same old ones. 

[abrams_tank 7,425]

8 minutes ago, g-liner said:

Parts are good, other parts aren’t. Remember it’s the poster you’re quoting that nearly got banned from the PMDG forum for pointing out some of the failings in the 737.

I think the PMDG 73 is good and was the bar to achieve but it’s been left behind now by other developers especially on Boeings with the ability to fly RNP ar approaches and rf legs etc.

PMDG seem to me, to be a company that made something great in the past and then haven’t improved it and are just focusing on churning out the same old content on each new sim or the developer that did much of it left and they don’t know how to fix all the things that aren’t right that people now are increasingly pointing out. 
 

The noise and reaction from PMDG seems to indicate the new 777 will just be a rehash of previous versions and still have the same old LNAV, this might be ok for people who aren’t that bothered by realism or don’t want it for more focused training but it’s a real shame they’ve given up on improving their products and instead are focusing on sales of the same old ones. 

Thanks @g-liner. And if I may ask, what are you type rated for?  I believe you mentioned you also fly an airliner in real life, but I can't recall which plane it was.  I would like to keep track of the respondents in this thread, especially if they are type rated on the 737 (and especially if I read future comments by them on flight models, so I know they are an IRL pilot).  In this thread, Stearmandriver is type rated for the 737, so I would like to know the other respondents in this thread that are type rated for the 737. Thanks!