2 questions!

[Vicpdx17 0]

Hi,

So I was wondering about 2 things.

 

A: Is there anyone that could do a repaint for the NGX 737-600 in Southwest Canyon blue colors?

 

B: Why is it that the NGx can only go up to 340 knots, on a flight tracking app it shows that a 737-700 can go up to 400 knots.

 

 

Victor S.

[Flamin_Squirrel 71]

B: Why is it that the NGx can only go up to 340 knots, on a flight tracking app it shows that a 737-700 can go up to 400 knots.

 

That'll be ground speed or true airspeed, rather than indicated airspeed.

 

I don't have any good links, but if you're not sure of the difference it's worth reading up on.

[Michar83 7]

I'll let A, hopefully, be answered by someone else.

 

B: Your flight tracking app will most likely show you ground speed.

Where as the 340 knots you're talking about (you're probably reading that off of your PFD) is your IAS or Indicated Air Speed.

Those two are differently measured, hence the difference.

[Vicpdx17 0]

Well for B I actually ment on the flightView app in the real world it shows as a sotuhwest in air that it is going 350-400 knots.

[hopskip 253]

Well for B I actually ment on the flightView app in the real world it shows as a sotuhwest in air that it is going 350-400 knots.

 

Yes. 400 knots ground track speed. It could even be 500 knots with enough tailwind. up at 30,000+ ft there are sometimes things called "Jetstreams" which are large columns of air, sometimes half a continent long, and maybe hundreds of nm wide, that can travel more than 100 knots (knots is a speed, not a distance).

 

The speed you see on the primary flight display of a 737-800 is Indicated Airspeed. It's how many air particles are striking an air pressure sensor at the front of the plane compared to air particles open to ambient air pressure on the side of the plane.

 

To see the ground speed, look at the top left of the Navigation/Ground display. You will find something that sais "GS". This is the groundspeed that FlightView is displaying. It will probably be a couple of hundred knots faster than the indicated airspeed tape on the PFD if you are at 35,000ft.

 

Flaps extension, maximum Mach, KIAS, stall etc speeds are measured by the Indicated speeds. You will stall at 160 knots flap up indicated airspeed wether you have a 100 knot headwind (Groundspeed 60) or a 100 knot tailwind (260kts groundspeed).

 

Indicated airspeed is all about how many air particles are going past you.

Ground Speed is all about how GPS and similar systems are measuring you passing ground terrain.

 

Avoiding stall, overspeed etc is all about air particles interacting with the wings. Wings generate lift by air. Air doesn't care how fast you are moving between cities, just how many air particles are being pushed over your wing surface. Ground speed cannot measure the air.

 

The higher you go, the less air there is. This is why people climbing Mount Everest have issues breathing and often need pure oxygen. Everest is about 29,000ft tall.

 

At 39,000ft theres way less air than on the ground. Less air particles striking the air pressure sensor at the front of the plane, and less air particles going over the wings to produce lift. The air particle "airspeed" indicator gets less stuff striking it, and so reads a lower number, and the air going over the wing is less, so less lift is being produced.

 

The wing will stall when a certain amount of air pressure can't be created over the wings anymore (simplified explanation) and the Airspeed indicator still shows a similar "number" when the lift runs out because it too is effected by the lower air pressure.

 

The Ground speed is still a GPS showing your exact location, which is still moving at 450 knots or whatever it is with all the wind and stuff.

 

The indicated airspeed sensor isn't measuring how "Fast" the air particles are going past, it's measuring "How many" are passing through the sensor, because this is the major part of creating air pressure, and air pressure is the major factor in producing lift. Not producing lift = stall.

 

Stall has nothing to do with engines. Gliders can stall.