I'm curious to know how realistic is 737NGX in flight behaviour, I just tested the plane by doing TO in various wrong configurations :

 

1. TO with no flaps deployed at all (though the VR are set either at flaps config of 5 deg or 10 deg) and I rotate the plane at VR

2. TO with wrong VR setting by fill in the wrong GW (below the actual GW) and I rotate at the  speed below the requirement VR speed (in other word I rotate the plane before the actual VR requirement)

3. TO with no flaps deployed and rotating the plane before VR

 

Surprisingly I TO smoothly at those wrong configuration

 

My other curious is how realistic actually PMDG simulates 737NGX in stall behaviour, is that just easy to recover the plane from a totally stall situation compared to the realworld counterpart ?

 

Flight dynamics are very good, performance of the aircraft is within 5% of the actual thing. Make sure that your realism settings are maxed out in the settings of FSX.

Flight performances are only tested in normal configuration, out of them, there are a lot of FSX limits that cannot be solved. 5% is in normal condition, I think error becomes 50% and over in some non normal conditions.

I'm curious to know how realistic is 737NGX in flight behaviour, I just tested the plane by doing TO in various wrong configurations :

 

1. TO with no flaps deployed at all (though the VR are set either at flaps config of 5 deg or 10 deg) and I rotate the plane at VR

2. TO with wrong VR setting by fill in the wrong GW (below the actual GW) and I rotate at the  speed below the requirement VR speed (in other word I rotate the plane before the actual VR requirement)

3. TO with no flaps deployed and rotating the plane before VR

 

Surprisingly I TO smoothly at those wrong configuration

 

My other curious is how realistic actually PMDG simulates 737NGX in stall behaviour, is that just easy to recover the plane from a totally stall situation compared to the realworld counterpart ?

Firstly the takeoff speeds are calculated to give you a big safety margin to stall, just like Vref is for landing.  You can fly slower but with less margin.  Not selecting TO flap will not necessarily put you in a stalled condition if you rotate as if flaps are set.

 

Secondly Leading Edge flaps/slats don't actually increase lift (they increase stall AOA) so not having them extended won't make much difference if you rotate normally unless you exceed stall AOA.  For a normal rotation you probably won't exceed stall AOA even with flaps up (around 14 deg).  You may be within a degree or two but the stall warning won't go off and lift will still be sufficient.

 

Thirdly, you may well rotate at indicated (but theoretically low) VR, but that doesn't mean you takeoff exactly the same way.  Lift off speed might be increased by a few knots without you noticiing it.

 

Taking these things into account, it's not surprising you can takeoff in the NGX at these incorrect configurations without too much problem. Safety margins are greatly reduced, but you didn't actually exceed limits.  The NGX flight model is working correctly, and in terms of lift and drag will be fine even if operated significantly off the design optimum.

 

 

Taking these things into account, it's not surprising you can takeoff in the NGX at these incorrect configurations without too much problem. Safety margins are greatly reduced, but you didn't actually exceed limits.  The NGX flight model is working correctly, and in terms of lift and drag will be fine even if operated significantly off the design optimum.

 

Well-written Kevin.  I was about to post similar, but you beat me to it.

Well-written Kevin.  I was about to post similar, but you beat me to it.

Thanks.  I'm almost sorry I did.  I'm sure it would have been a cracker.

:)

Thanks.  I'm almost sorry I did.  I'm sure it would have been a cracker.

 

Not sure.  It probably would have been typically verbose, at least. haha

If you pull the yoke back hard enough, with the engine power up at a high enough power setting on a long enough runway it will either
1: Takeoff
2: Tailstrike... and then eventually takeoff.

What does an aircraft need to fly?

Airspeed, angle of attack....

a 737 on a 12000ft long runway will get airborne at flap 0 given enough airspeed. Depending on how much pitch and elevator force you give it, it may or may not break some stuff like the tail on the way up, but the wings moving through air at 160+ knots will be flying, regardless of what the computer in the FMS thinks about it all, or how many takeoff config warnings are screaming at you.

Now if you do that on a 5000ft runway at MTOW and flap 0, you will probably run out of runway before it gets airborne, but if you keep accelerating and pretend that the grass and dirt at the end of the runway is totally solid and there aren't any fences in the way, same thing. Once there's enough airspeed, the wings start making enough lift to get the aircraft off the ground.

Mightn't be elegant, might be making sparks off the rear fuselage as it makes contact with concrete (not simulated in FSX/NGX btw - sparks that is.) but those wings make lift, flaps or no. Of course they make more lift with flaps extended... but they also make more lift when you go faster.

Though that "meep... mip meep... mip meep..." sound going off during the whole takeoff roll with the flaps up would be scary, or at least drive you batty right?

 

Last WorldFlight I was on a 737sim, and on one flight I was operating we were running a little late at the back of the pack, and trying to get airborne as quick as possible. On application of Takeoff thrust we got the takeoff config warning and without even talking to the other crew member I just chopped the throttle and stopped. (To his credit that other crew member also had his hands ready to grab and chop the throttle if I hadn't, and was on the radio to ATC as soon as it was apparent I was stopping). Got off the runway and started heading back to the holdshort point trying to figure out what was going on. Never found out properly, but we recycled flap up, back to flap 5, opened and stowed the spoilers and checked the overhead. Subsequent takeoff was fine. Never figured out why it was out of config the first time, but the flaps were deployed, spoiler was stowed, autobrake was RTO, Engine ignition was CONT.

 

Figured it might have just been a miscommunication between the simulator hardware and the FSX components. But even in a sim, running late during an event with impatient controllers and aircraft behind me, that alarm going off = stop now and check everything. 

 

Not fearing a crash and death (though that' certainly possible) but I don't like stickshaker at 20ft.

 

 

.... on the other hand a C172/PA28 type aircraft will takeoff with flaps up as a matter of course. Using flap 10 in a C172 will get you off the runway faster, but then you climb slower! Getting to 500ft above ground with flap 10 in a C172 is a much longer process than getting to 500ft on flap 0.

 

Flap makes lift... but it also makes drag.

 

Ok less of a problem on a Jet perhaps, but still a consideration. (This is why flap 30 takeoff is a bad idea).

 

You'll be off the concrete faster with more flap, but it won't help in getting over the fence/trees/terrain past the end of the runway.

 

Here's some fun stuff test pilots do:

 

 

 

Now if you do that on a 5000ft runway at MTOW and flap 0, you will probably run out of runway before it gets airborne, but if you keep accelerating and pretend that the grass and dirt at the end of the runway is totally solid and there aren't any fences in the way, same thing. Once there's enough airspeed, the wings start making enough lift to get the aircraft off the ground.

The difference in lift between flaps 0 and flaps 5 for a given AOA is minimal. You will take off at about the same speed and pitch angle but as I said in my previous post you will be much closer to stalling.

Have a look at this

 

https://www.youtube.com/watch?v=cHhZwvdRR5c

 

No flaps, no engines and still wants to fly. Admittedly it's will be a bit lighter but an aircraft is designed and built to produce lift.