Flap15 approach too fast.

[martin-w 3,234]

Just got the PC-12 the other day, so far liking it.

 

Certainly very pleased that the characteristic 2-3 degree pitch down on approach is correct.

The only issue I've spotted is approach speed at flap 15, according to my research, I suspect it's 15-20 knots too fast. Flap 30 and flap 40 are correct.

110knots is the correct approach speed for zero flaps, not flap 15.And at max landing weight, not 8500lbs.

The PC-12 in the sim is 8500lbs, at that weight, at flap 15 it shouldn't be 110 knots.

I could be missing something of course, I wouldn't be surprised.

[Flyfox 114]

Martin, have you tried with the modifications in aircraft.cfg, which mainly add more drag caused by the flaps (see http://forum.avsim.net/topic/454990-odd-pitch-on-landing/)? My landing experience is significantly more realistic since I added those mods.

[martin-w 3,234]

Hi Felix.

 

The landing experience is realistic except, hypothetically at this stage,  for flap 15 approaches.

 

The mods you mention are in the flap.0 section, so they will impact all flap settings. Flap 40 is correct, as is flap 30, it's just flap 15 that's too fast. Pitch is correct at flap 15, 2-3 degrees down]   AoA indicator is correct, just approach speed too high.
 
The other point of course is that modifying drag scalars impacts other parameters, for example engine power. More power will be required to counter the drag, and thus more inaccuracy is introduced.
 
I believe the guys were trying to overcome what they perceived as excessive pitch down on approach. My tests tell me that the pitch on approach is correct. as confirmed by two real world PC12 pilots and video evidence. I commented in that thread actually.


More drag will merely be countered by engine power and not impact pitch on approach, so not sure why they added that parameter.

 

If I am correct [still not definitive] then what would be required is modifications that impact flap 15 approaches only. A quick glance of the cfg and I see there is only a flap.0 section. My experience tells me that to impact flap 15 only would require an additional flap section. Not sure if that's feasible without corresponding air file entries.

 

At this stage though, I'm just trying to determine if I am right or wrong, if flap 15 approaches are too fast.

My logic here [or lack of] is based on information on the Pilatus website. Stall speeds were available at various flap settings and weights. From that information I determined approach speed, which is 1.3 times stall speed, or 30% higher in other words. 

 

We have to remember of course, that the Carenado bird is at 8500lbs, not max landing weight, and many of the resources available apply to max landing weight. Hence why I calculated approach speed from stalls speeds that were available.

[martin-w 3,234]

http://www.pilatus-aircraft.com/#196

 

Weight in the sim is 8500lbs.

 

 

Stall speeds.

 

Flap 40 = 59

Flap 30 = 63

Flap 15 = 66

 

Approach speeds should be + 30%

 

Flap 40 = 77

Flap 30 = 82

Flap 15 = 86

 

At flap 15 I see 110 knots.

 

 

if I'm missing something anybody know what?

[Gregg_Seipp 565]

These might help your discussion. 

 

http://pilatusowners.org/wp-content/uploads/2014/10/new-pc12-45-check-list.doc

 

http://quizlet.com/11322883/pc-1245-numbers-flash-cards/

[martin-w 3,234]

Thanks Greg, certainly does, that's a great help. I see from your normal procedures checklist...

Flap 15

Vfe 163

Vref 98

Vref Ice 108

 

 

It's not clear at what weight though, I suspect it would be max landing weight, so 9921lbs. So at 8500lbs in the sim, that would suggest we are seeing an approach speed that is way too high.

 

In the sim we are 14% lighter than max landing weight, so that would equate to 85 knots at 8500lbs. Close to what I estimated above. This is looking more definitive.

 

I see Vref at 0 flaps is 118. Haven't tested that yet. Would be less at 8500lbs of course.

 

It's not a huge deal to me in the sim, as I usually land Flap 30 or 40, but you would think something so fundamental would be right.

 

We are talking a huge 25 knots too fast!

[Gregg_Seipp 565]

 

 

I see from your normal procedures checklist...

 

That's a real world checklist...not mine.  Perhaps there's more info out there somewhere.

 

Gregg

[martin-w 3,234]

That's a real world checklist...not mine.

 

 

 

 

Yes I thought it was Greg, I meant "yours" in terms of you posted it. It was very useful.

 

Hell of a cock up if I'm right.

 

We may not land Flap 15 that often, but when we do, it'sonly reasonable to expect a semblance of realism.

[Gregg_Seipp 565]

 

 

We may not land Flap 15 that often, but when we do, it'sonly reasonable to expect a semblance of realism.

 

Can you not reduce power to get the right approach speed?  Does it throw AOA way off? 

[martin-w 3,234]

Well, we are talking about 25 knots too fast, which is a lot, so if you simply reduce power and fly at what should be the correct approach speed, lift is reduced and thus angle of attack increases, pitch would then be higher than is realistic for the PC-12. And yes, the angle of attack indicator on the PFD would indicate inaccurately.

 

What most of us would like as simmers, is of course something as fundamental as approach speed to be correct.

[Gregg_Seipp 565]

Might be worth a try to increase the 'flaps 15' setting to flaps 18 or 20 (in the config file)...just to see what happens.  Truly, if you think about it, flaps are nothing more than 2 pieces of metal that are stuck out at a particular size, position and angle.  The fact that they work well at 2 settings and not at a third seems weird and something wrong with the way FSX is crunching the numbers.  I suspect it has more to do with FSX than this airplane.

 

Gregg

[Bert Pieke 7,584]

I think you need to get an experienced PC12 captain into this discussion to arrive at anything substantial... doing this from checklists, tables, and youtube videos is going to be inconclusive at best.

 

As you mentioned, this is all going to depend on weight and balance in the airplane, so I would suggest that you fly the airplane, and learn to handle it the way it behaves with different loads - just like in the real world.

 

I always land this plane with 15 degrees of flaps (no modifications) and find that it handles nicely..

 

Now, I fly by the seat of my pants mostly, and let it bleed off speed from 90 knots over the runway lights.. just hold it off the runway, until it settles.

[Gregg_Seipp 565]

 

 

I think you need to get an experienced PC12 captain into this discussion to arrive at anything substantial... doing this from checklists, tables, and youtube videos is going to be inconclusive at best.

 

Truly, that would be ideal.

[martin-w 3,234]

I suspect it has more to do with FSX than this airplane.

 

Gregg

Well no, not really. It's not an FSX issue, it's the flight model. I know of no other add on that is on the numbers at all but one flap setting.

 

 

I think you need to get an experienced PC12 captain into this discussion to arrive at anything substantial... doing this from checklists, tables, and youtube videos is going to be inconclusive at best.

 

As you mentioned, this is all going to depend on weight and balance in the airplane, so I would suggest that you fly the airplane, and learn to handle it the way it behaves with different loads - just like in the real world.

 

I always land this plane with 15 degrees of flaps (no modifications) and find that it handles nicely..

 

Now, I fly by the seat of my pants mostly, and let it bleed off speed from 90 knots over the runway lights.. just hold it off the runway, until it settles.

Landing isn't an issue Burt, I have no issue landing. This is about realism.

 

Weight and balance isn't the issue when it's smack on the numbers at 30 and 40 flap. Weight is a variable I have accounted for.

 

If it complies with the tables and POH at 30 and 40 but not 15, then I'm suspicious.

 

There may be something I'm missing, but as yet nothing has surfaced.

[Bert Pieke 7,584]

I understand your frustration, but I think you might as well put this issue aside,

and enjoy flying the airplane..

 

Just my opinion.. B)