Now now no need to put the guy down.

Now now no need to put the guy down.

I know... Frustration. If the guy won't read...I'm willing to help him though.Best regards,Robin.

Yeah sorry for typing on my phone........its just as easy as a fullsized keyboard. Squirilly is just as expression and im sure we can agree that its not even a real word. The whole "American thing" was uncalled form i already said that i stand corrected about the main prinicple of it all However i get this whiole write up about how airspeed and graphs and air density and it al comes down to speed decreasing aoa and not altitude. Thats at least what i got out of the whole thing. Like i said...ill be sure to carry a fullsized keyboard with me where ever i go and to not use expressions.......wow seriously guys. All this started out with a joke with all caps and a very broad explination of aoa.

Matthew,I just looked up squirrelly and it's odd, crazy etc and I wouldn't call principles of flight that! Both Bernoulli and Mr. Newton would turn in their graves from listing to you. Still it is progress that you admit you were wrong and that is a step in the correct direction. Now if you really intend to teach people about priniciples of flight I suggest you go and read books about it. There is a lot more to aerodynamics than any PPL (or indeed ATPL) book will teach you. Get the book called "Handling the big jets" by D.P. Davies. Feel free to ask us any questions regarding principles of flight or indeed any other subject to do with aviation.

Get the book called "Handling the big jets" by D.P. Davies.

+1It's a great read for any pilot.Best regards,Robin.

As i said before i stand correct and i was horribly off in my understanding of the subjext at best. That being said, this sort of new knowledge will make me a bettsr pilot. However i dont know if it will make be able to type on a phone better. Anyways does anyone have a latter so i can get out of this hole i dug for myself?

No. Speed does NOT decrease AoA.As I clearly stated before, TAS determines lift, NOT IAS!!!! IAS measures the PRESSURE of the air entering the pitot tube. Lower air density, lower pressure, thus lower reading on the IAS display. TAS however must increase with altitude (as a result of reducing air density), and is a measure the velocity of what air remains. The actual molecules of air are hitting the aircraft at higher and higher speeds, and must do so in order for the wing to continue generating sufficient lift as the air gets thinner.It is this fact that the air flow is increasing in velocity (and more critically, relative to local speed of sound) as the air density reduces that means the stall AoA reduces, because the air flow is less able to follow the curvature of the wing. The separation of the boundary layer *IS* what a stall is. Behind the separated airflow is turbulence and drag, and results in an *increase* in the relative pressure over the top surface of the wing, reducing lift. The speed at which this happens increases merely as a symptom. It is NOT a cause!I really should sit and write a book.From your profile:Yes... VERY long term...Best regards,Robin.

i agree with that its TAS not IAS.....never didnt.

Your point. Im well aware of that. However critical AOA doesnt change.

Oooh! Feisty! :( I was agreeing with you; my comment was just friendly humor adding fun to your past statement, mate! :(

It is this fact that the air flow is increasing in velocity (and more critically, relative to local speed of sound) as the air density reduces that means the stall AoA reduces

Not defending on the person you replied to, but I think you are yourself going slightly in a wrong direction right there.The stall speed of any aircraft can be expressed as IAS, CAS, EAS or TAS. None of this has anything to do with higher stall speeds (smaller AoA) in high altitude, when compared to a fixed IAS stall speed at SL. You are talking about the difference between IAS and TAS, basically.What affects the stall in high altitude, in high speed is the compressibility, as you already have pointed out. There are two factors to the higher IAS stall speed, both related to compressibility.1. compressibility effect on the pressure pattern -> wing "effective weight" increases -> leading to higher stall speed and stall at lower AoA2. compressibility error on the instrument itself, ie the difference between IAS and EAS is exaggerated due to compressibility -> stall at higher IASBut... in relation to the higher velocity of air flow in a less dense air (in high altitudes) when keeping IAS unchanged, it's essentially a description of TAS. That does not have anything to do with smaller than usual stall AoA at high altitudes. Those are two different and unrelated things.Tero

This really is getting ridiculous. Think about it - how many times in the past year (or even ten years) has anyone heard of a stall involving a Boeing 737? Some of these requests for some specific kinds of failures (eg smashed windscreen from bird strikes or flameout due to too much wind coming up from behind the engine) are getting beyond a joke now. PMDG is making an airline simulation - not a failure scenario simulator!!!

HI Matthew Bellette,May I point you to the Amsterdam accident of the Turkish 737NG ? and also the Airbus A320 accident near Perpignan? We are not asking for specific kind of failures. Just pointing out that FSX aerodynamics is flawed. How PMDG has decided to work around this we don't know yet. And IMHO I belive that proper aerodynamic charactaristics are way more important than a birdstikes. Kenneth Smith,I suggest you also read the mentioned books and pdf files. Critical AOA does not change with low speed flight (ie where you PPL's are), but when the compressability takes effect it does change. Don't make Newton and Bernoulli turn again. They must be really tired by now.Regards

Robin quoted: "And IMHO I believe that proper aerodynamic charactaristics are way more important than birdstrikes."+1Also, I'm still wandering if indeed PMDG has altered the FSX coding to accommodate the aerodynamic forces of the 800 NGX as stated in my very first posting at the beginning of this topic as stated by RSR:" Regards,jen noulet

Robin quoted: "And IMHO I believe that proper aerodynamic charactaristics are way more important than birdstrikes."+1Also, I'm still wandering if indeed PMDG has altered the FSX coding to accommodate the aerodynamic forces of the 800 NGX as stated in my very first posting at the beginning of this topic as stated by RSR:" Regards,jen noulet

Sorry about that: I meant Kenneth quoted: "And IMHO I believe that proper aerodynamic charactaristics are way more important than birdstrikes."Regards again,jen noulet

Kenneth Smith,I suggest you also read the mentioned books and pdf files. Critical AOA does not change with low speed flight (ie where you PPL's are), but when the compressability takes effect it does change. Don't make Newton and Bernoulli turn again. They must be really tired by now.Regards

Martin,I'm sort of curious where that came from; I don't remember participating in the AoA debate at all short of a coffin-corner comment. :( I believe you may have named the wrong guy in your reply, but since I love aerodynamic books, you got yourself a deal anyways. I wouldn't want Newton and Bernoulli to turn in their graves again, not after what we did during the "Pitch for Speed" debate! :(

Sorry about that: I meant Kenneth quoted: "And IMHO I believe that proper aerodynamic charactaristics are way more important than birdstrikes."

Jen, I think you got it right the first time! I'm not nearly smart enough to make such a brilliant statement - I believe the true owner of that comment belongs to Robin, not me. :(

Martin,I'm sort of curious where that came from; I don't remember participating in the AoA debate at all short of a coffin-corner comment. :( I believe you may have named the wrong guy in your reply, but since I love aerodynamic books, you got yourself a deal anyways. I wouldn't want Newton and Bernoulli to turn in their graves again, not after what we did during the "Pitch for Speed" debate! :(

Hi Kenneth,I think you agreed with the guy who started all this with this line: "However critical AOA doesnt change."and this statement does not belong to Robin (although I think he will agree), but me: "And IMHO I believe that proper aerodynamic charactaristics are way more important than birdstrikes."

Hi Kenneth,I think you agreed with the guy who started all this with this line: "However critical AOA doesnt change."and this statement does not belong to Robin (although I think he will agree), but me: "And IMHO I believe that proper aerodynamic charactaristics are way more important than birdstrikes."

Martin,You're right (Why am I not surprised?) - I promise to spend my next flight on the ground reading "Handling the big jets" by D.P. Davies (And maybe a book on reading comprehension while I'm in the library). While I do that, maybe PMDG can work some of their magic (As Robert calls it) to try and work around this FSX Limitation. They did something similar for the aircraft slats, if I remember. :(

... May I point you to the Amsterdam accident of the Turkish 737NG ? and also the Airbus A320 accident near Perpignan? ...

To your list one might add several of the 737 stalls noted here - http://www.b737.org.uk/accident_reports.htm - such as Algiers in 2003, Nigeria in 2005 and it's not just a third world thing either: see for example Pittsburgh, PA in 1994, Washington, DC in 1982 and Chicago Midway in 1972, where stall was also a factor.As I understand it, the training of commercial airline pilots concentrates on the approach to stall but leaves trainees relatively unexposed to the stall regime itself. Both of them are fundamental risk areas in real life yet, according to some of the posts at pprune to which I referred previously, the second of them in particular tends to be neglected (no doubt, relatively rather than absolutely) or imperfectly understood.I would have thought that simulator accuracy both in the approach to stall and in the stall regime itself is far more important than many of the arcane details with which the NGX is apparently replete, such as which bus supplies electricity to which light bulb and other details far removed from the "critical path" of safety. So I am sure that PMDG will want to model the stall behaviour as accurately as they can within the limits of what is achievable under FSX.I am sorry if the above sounds "off-topic" but I think the OP raised an interesting point which has not been answered yet. People use FSX with different priorities in terms of fidelity of experience. My own perspective is that FSX when combined with high-fidelity products such as PMDG's, is mainly educational as it engages with a wider interest in airline safety. Understanding the limits of the fidelity ESPECIALLY at and beyond the margins of the aeroplane's normal performance envelope, is therefore of interest, IMHO.Tim

2. compressibility error on the instrument itself, ie the difference between IAS and EAS is exaggerated due to compressibility -> stall at higher IAS

Any aircraft with ADCs usually display EAS actually, which is the IAS corrected for position, error and compressibility. The speed you see on the PFD is actually CAS/EAS, not IAS.Besides - I can't see what relevance that has - it is still measuring pressure sensed at the pitot head.

1. compressibility effect on the pressure pattern -> wing "effective weight" increases -> leading to higher stall speed and stall at lower AoA

Source? Nowhere in the lift equation do I see weight/mass as a variable.

the second of them in particular tends to be neglected

IMHO they should practice it more often, same as takeoffs/landings.Best regards,Robin.