Aerodynamics question...

[Larry Gude (Premo)]

OK, it's 1700 mikes from BWI to ABQ. It took 4 hours 20 minutes from take off to touchdown to get there, an average ground speed of about 400 mph on a plane designed to fly, what 600? The pilot told us we had a 120mph head wind, so, does that make air speed 520 or so?

And on the way back it took 3 hours flat, or 570 mph ground speed.

Now, does all that sound right, am I using correct terms and facts, ground speed, air speed, commercial aircraft speed limits, and is it a simple aerodynamic fact that the plane can't cover 570 mph ground speed with a head wind of 120 or do they not go faster because it is too inefficient?

Thanks in advance.

[Bustem' Down]

Originally Posted by Larry Gude

OK, it's 1700 mikes from BWI to ABQ. It took 4 hours 20 minutes from take off to touchdown to get there, an average ground speed of about 400 mph on a plane designed to fly, what 600? The pilot told us we had a 120mph head wind, so, does that make air speed 520 or so?

And on the way back it took 3 hours flat, or 570 mph ground speed.

Now, does all that sound right, am I using correct terms and facts, ground speed, air speed, commercial aircraft speed limits, and is it a simple aerodynamic fact that the plane can't cover 570 mph ground speed with a head wind of 120 or do they not go faster because it is too inefficient?

Thanks in advance.

What kind of plane?

[Bustem' Down]

Boeing 737, 767and McDonnell Douglas MD-80 all have cruising speeds under 550 mph.

[MMDad]

Wirelessly posted (Mozilla/4.0 (compatible; MSIE 6.0; Windows CE; IEMobile 7.7) 320x240; VZW; Motorola-Q9c; Windows Mobile 6.0 Standard)

Due to lower air pressure at altitude, indicated airspeed is far lower than true airspeed. For example, an indicated airspeed of 350 at 40K feet is roughly equivelant to 630 knots. That's why you cruise at high altitude - the lower pressure means you can travel at speeds that would be supersonic at lower altitudes.

[huntr1]

headwind = slows them down
tailwind = speeds them up

best I can do for ya.

[Larry Gude (Premo)]

Originally Posted by Bustem' Down

What kind of plane?

...SR71 or a 737. One or the other. I can't quite remember...

[Larry Gude (Premo)]

Originally Posted by MMDad

Wirelessly posted (Mozilla/4.0 (compatible; MSIE 6.0; Windows CE; IEMobile 7.7) 320x240; VZW; Motorola-Q9c; Windows Mobile 6.0 Standard)

Due to lower air pressure at altitude, indicated airspeed is far lower than true airspeed. For example, an indicated airspeed of 350 at 40K feet is roughly equivelant to 630 knots. That's why you cruise at high altitude - the lower pressure means you can travel at speeds that would be supersonic at lower altitudes.

...Ok, obviously, I didn't have a clue of the indicated airspeed, so, I mean, I'm just working off of miles from A to B and time. What you're saying here is 350 indicated is covering 630 in terms of actual distance from A to B?

[Larry Gude (Premo)]

Originally Posted by huntr1

headwind = slows them down
tailwind = speeds them up

best I can do for ya.

...I knew that part. I'm just finding myself curious if they Can't go any faster in terms of how much ground they are covering into a head wind due to the fact that 400 mph forward into a 120 mph head wind is the equivalent of the plane flying, going through the air at 520 and that they just can't go any faster which seems obvious the more I think about it...

[Gwydion]

Better question is what happens when you put a plane on a treadmill.

[Pete]

Originally Posted by Larry Gude

OK, it's 1700 mikes from BWI to ABQ. It took 4 hours 20 minutes from take off to touchdown to get there, an average ground speed of about 400 mph on a plane designed to fly, what 600? The pilot told us we had a 120mph head wind, so, does that make air speed 520 or so?

And on the way back it took 3 hours flat, or 570 mph ground speed.

Now, does all that sound right, am I using correct terms and facts, ground speed, air speed, commercial aircraft speed limits, and is it a simple aerodynamic fact that the plane can't cover 570 mph ground speed with a head wind of 120 or do they not go faster because it is too inefficient?

Thanks in advance.

The airframe of the plane is load limited to a particular airspeed. It is not so much the engine that limits speed in the air it is the max speed the airframe is rated to before the wings peel off. To an airplane groundspeed means nothing, airspeed (IAS)means everything. I don't think a 737 can hit 600 IAS more than likely it is just over 500 IAS and that is full throttle. Cruising at max speed all the time would be inefficient. The engines and airframe are engineered for a modest airspeed capability with reasonable fuel efficiency.

So on your trip you were probably flying at 520 IAS, factoring in the headwind going west of 120 your groundspeed was 400.

Coming back you had a groundspeed of 570 MPH but because of a tailwind coming east the IAS was under 500 mph. The tailwind got you more giddyup and saved them a bunch of fuel.