Hi fellow simmers !I am patiently learning to master the art of simulated flight, a great thanks to Avsim and all of you for this great forum; you help a lot !Now, back to the business: I have started flying above FL30 with the stock 737 and I must be doing something wrong. No matter what I do, the plan will stall when I reach FL39.... I had a look at the FS9 manual and I can not find any hint...Please please Help !Thanks muchMike the rookieSpecialized in lawndarts

A couple of things to note,The 737-400 usually cruises no higher then FL370 and that is with a relatively light fuel load. If you try to climb too high with heavy loads, then you will stall. In the real world an aircraft will step climb, meaning at the beginning of the flight when heaviest the plane may only climb to FL300 until some fuel is burned off and then step climb once or even a few times during a long haul flight. The 737NG's will cruise as high as FL410 with light loads, but again the second generation 737's usually stay at FL370 or below.There are many sites that have information that could help you with aircraft specifications/limitations and help you with the learning curve quite a bit. I have attached a link to one such site below.http://www.b737.org.uk/Regards,Van LatendresseYeoDesigns/AFG GroupPanel/FDE Designer

I'm not surprised at a 737 having difficulties above 39000, what I don't understand is why the Posky 757 struggles beyond 20000 feet.I'd started with 70% fuel and progressively wound the climb rate back to 600 fpm and deicing on.With engines apparently running at full bore on autothrottle, it struggles to hold 200 knots IAS and eventually pitches up to a stall.This has happened to me twice (out of 2).Anydody else having that problem with the 757?

Funny you mention that. I've been flying the Posky 757s for about a week now. I've twice stalled the Eastern Airlines version at around 27K feet, but the ATA version is rocksolid. I've also had the problem with other A/C as well. The best I can figure, you've got to let the plane accelerate after takeoff and be prepared to dial back your rate of climb after you get above, say, 15K.

I am not sure if this has anything to do with it, but if under realism settings you have show indicated airspeed unchecked, you may have difficulties at high altitudes. Your plane should stall out at some point with that option unchecked.

I replaced the Posky aircraft.cfg file with the one supplied with the Lonny Payne panel and now it climbs like a rocket, although I still wind the rate of climb back from the default 1800 feet per minute to 800 or 1000 fpm as the altitude increases. I understand this is a realistic requirement.I compared the two files and I can't see any significant difference, so maybe it's irrelevant.Does anyone know what the default rate of climb in the aircraft.cfg actually does? I know it sets the autopilot, but does it do anything else? I did notice that the Posky file has a default of 800 fpm whereas Lonny Payne's has a more realistic 1800 fpm. What happens if you climb an aircraft which has been told its default is 800 fpm at, say, 1200 fpm at >25,000 feet? I'm not talking about aircraft where 800 fpm is the true default, just a 757 that THINKS 800 fpm the best it can do?What does the flap type in the aircraft.cfg do? I have a feeling that's just the method of actuation?As to building speed before climbing, I can't believe that's necessary in a 757, bearing in mind it's a twin jet, which usually have plenty of reserve power to cope with a single engine failure. Now my problem is fixed, I have to throttle back soon after take-off to keep below 250 knots at an 1800 fpm climb rate - which is as it should be. From memory, the autopilot is now climbing the plane happily at 80% EPR or thereabouts.

Which does that automatically, doesn't it?In any event, whether you have indicated or true airspeed showing, wouldn't the autopilot adjust?After all, there is no point having an "easy" setting whereby the aircraft stalls on the autopilot!

Hi,The default rate of climb in the aircraft cfg is for the vs area of the autopilot and nothing more. The flap section of the aircraft cfg does many things, including proper animation of flaps and slats as well as affecting the flight dynamics in a proper way when any amount of flaps are selected. The system type will have no impact on the way the aircraft flies ie: stalling while climbing.One thing I need to mention is, if you are looking at realism then that goes rignt out the door by using the vert speed portion of the autopilot for climbing (and many other aspects of a flight) as in the real world pilots seldom use that particular function. Pilots will usually hand fly the aircraft to FL100 then engage the autopilot along with LNAV and VNAV (FMC controlling navigation and climb rate/engine thrust etc.). Pilots will use VNAV and switch if need be to FLCH (flight level change) below FL100 still allowing the FMC to do it's job rather then using vert speed. The only time a pilot may use the vert speed option is when he is perhaps making a very minor change from say 2000ft to 1500ft at -300fpm usually on approach. The main reason vert speed is not selected in most aspects of a given flight is, there is no speed decay protection when in that particular mode. If you set the vert speed for a 1800fpm climb rate, then you will stay at that angle of attack regardless of speed decay until you eventually stall if there is no pilot intervention. Now in VNAV mode the aircraft will climb as it should and at higher altitudes the climb rate will decrease appropriately to maintain speed.Unfortunately the default MSFS panels haven't an fmc or any of the above features I mentioned, so there's nothing much that can be done for a realistic flight experience, the same is true for most freeware panels. If a simmer is looking for maximum realism then you usually need to go the payware route as I did many moons ago. I use the PIC panel with both the 767-300 and Posky's new 757 (with my own FDE) and the immersion factor is fantastic and the birds fly very close to real world numbers.Regards,Van LatendresseYeoDesigns/AFG GroupPanel/FDE Designer

Hi fellow simmers,Thanks for all your recommandations and ideas.By the way, I proceeded with trial and errors and I may have an answer to my question. I Want to share with you and maybe get the opinion of someone knowledgeable enough about real-life flight physics.I am using True Airspeed instead of Ground Speed (you can check this option in the setup menu under realism) and usually fly around 300 knots. By using the auto-throttle, the autopilot will maintain this speed.So when reaching FL300, I noticed that my plane had a high AOA (above 10

Absolutely! And the lower pressure is responsible for the difference between IAS (indicated air speed) and TAS (true air speed). The speed of the aircraft is measured with the pitot tube, the pressure at the end of the tube is proportional to the airspeed at a given altitude. That means that 200 knots true air speed at 1013 mbar (sea level) would give the same pressure (and thus speed readout) as 400 knots at 507 mbar (round about the pressure you

>In the end, I guess it has to do with air density at high>altitude. The higher the altitude, the lower the air density,>the higher the required speed to avoid stall.>Any comment ?>>Mike the rookie>Specialized in lawndartsCorrect !Once above 10,000ft and 'released' from the 250kt airspeed limitmost planes stop using ias in kts, and go to ias in mach numbers instead, this proves to be more reliable.This might help explain that a bit more,its' not too technical;"The reduced density of the atmosphere at high altitude means that the aircraft has to fly at a higher true airspeed to obtain sufficient lift; lift being proportional to the density of the air as a square of the velocity of the speed. An aircraft's stalling speed remains at a constant indicated airspeed up to any altitude.The speed of course is that at which the lift derived is no greater than the weight of the aircraft. As the density of the air drops to one quarter of that at sea level,so the true stalling speed of the aircraft is doubled. Thus if the true stalling speed were 100mph at sea level,it would be 200mph at 40,000ft although indicated airspeed would still be 100mph. Taking this concept further,the stalling point at 60,000ft would have risen to half the speed of sound,and at 80,000ft the stalling speed would be Mach 0.8. An aircraft is ultimately restricted by its' sonic or aerodynamic ceiling-the height at which the normal stalling speed and critical Mach number co-incide"This explains what 'critical Mach number' is;"Air deflected over the 'hump' of the wing has to travel faster than the surrounding airflow. The highest velocity at a point on the wing's surface may be as a third faster than the true airspeed of the aircraft.This means that the effects of compessibility and shock waves are experienced long before the aircraft is anywhere near the speed of sound. They may occur at a Mach number of anything from 0.7 to 0.8 according to the aircraft design.The speed at which an aircraft first experiences compressibility effects is known as its critical Mach number"This explains how Mach is derived;"The speed of sound is not constant.Changes in air temperarure at different altitudes consequently result in decreasing the speed of sound from 760mph at sea level, to 660mph at 36,000ft,above whichto all intents and purposes the speed of sound remains constant""As rapidly increasing performance in both altitude and speed began to take aircraft within striking distance of the velocity of sound,it became necessary that a pilot should have some means of relating his own true airspeed at any height to that of sound. A system originated in the nineteenth century by Dr. Ernst Mach,an Austrian physicist who first related the angle of the shock wave of a bullet to the velocity of sound,was therefore adopted. This gives the varying velocity of sound the constant factor of Mach 1, and relates to the true local speed of sound that it represents,the true airspeed of the aircraft. The aircraft's speed at any height is thus divided by the local speed of sound. Therefore,if the local speed of sound is 750mph an aircraft's true airspeed of 375mph will be shown as Mach 0.5Again, an aircraft flying at 340mph where the local speed of sound is 680mph will also register a Mach number of 0.5"From the book "The Sound Barrier" by Neville Duke and Edward LanchberyHope this helps:-wavePete

>Which does that automatically, doesn't it?>>In any event, whether you have indicated or true airspeed>showing, wouldn't the autopilot adjust?>>After all, there is no point having an "easy" setting whereby>the aircraft stalls on the autopilot!On easy setting I am 99% sure that the option for indicated air speed is unchecked.And negative, AFAIK, with true airspeed showing the AP will not adjust. I am willing to be that is your problem right there ;-)

So I am 99% sure I was working to IAS - unless I had made a temporary error.The aircraft & panel are now working well but I have no idea what caused the initial problem. I can only speculate:a) Something in the Posky aircraft.cfg file, which I have since replaced with Lonny Paynes': there are some minor differences, but nothing which I could point at, apart from the default rate of climb, which I'm told affects only the autopilot setting when a flight level is selected and not the flying characteristics of the aircraft itself.:( That I did have the spoilers deployed - although I inspected the aircraft from an external view and didn't see them. Flaps can I think be ruled out, as I have since found that the cockpit has a warning for excessive speed with flaps extended, and I'm sure that would have tripped at some point.

I wasn't using the rate of climb feature directly, but setting the flight level required.This brings the default rate of climb in from the aircraft.cfg file.My point was that a)800 fpm isn't realistic as an INITIAL rate of climb and is likely to get you "hurry-up's" from ATC - so I had manually increased it to 1800 fpm and :( as higher altitude I had would this back to around 1000 fpm and maybe less - partly because this is what aircraft really do, albeit automatically, and partly because I wasn't sustaining a sensible airspeed.

Another dumb question from a "wannabe" big iron jockey. I've had stalling problems as well at higher altitudes and posed the same question a month or so ago. I worked around the problem by filing lower flight plan altitudes (I fly 2K2 so don't have the option that I understand is now in FS9 to request higher altitudes en-route), and also watching the attitude indicator. As soon as I notice it creeping up during the upper ends of the climb I back off the climb rate to stop the plane from stalling. Having said all that, a comment earlier about heating the pitot tube has me thinking. Should I turn Pitot Heat on at high altitudes? I bet that's part of my problems, assuming the simulator has that function enabled. Any thoughts?