A/C order question for Delta guys

[BILL LUMBERG]

Only in the nitpicking sense that FDX is the only airline to ever operate the MD-10. Now, if you are talking about a DC-10 that is a whole 'nother issue.


Regards,
Fr8-

If he did ride on one, I'm sure he thanks you for the ride!

 

[igneousy2]

FYI: The NG's are geometrically limited, not aerodynamically limited. They increase the ref speeds so you don't hit the tail. At least that's what I've been told.

I'm going to have to look into this further but that doesn't make sense to me at first glance because tail strikes are a greater concern at lower weights at lower flap settings. Which is the opposite of what I would expect if what you've been told were true.

Additionally, the 400 has a greater risk of tail strike on landing at light weights then the NG's do. Get to slow while you're light on a 400 and you will strike the tail.

 

[CheapFlyer]

. Get to slow while you're light on a 400 and you will strike the tail.

That's exactly the theory on the NG's increased ref speeds. Increase the speed and you won't hit the tail.

 

[SWA Bubba]

FYI: The NG's are geometrically limited, not aerodynamically limited. They increase the ref speeds so you don't hit the tail. At least that's what I've been told.

You're partially right, but actually, it's simple aerodynamics. It's the same exact wing, so if you want to generate more lift to support the greater weight of a stretched NG, you've got to go faster. The other possibilities are to change the shape of the wing (not practical to redesign), or increase the AOA (not practical due to the increased length of the fuselage). So, go faster it is. It's as simple as the higher gross weight, the higher the Vref for a given wing.

As far as geometric limitations, Boeing has pretty much reached it for the 737 in a -900. The landing gear is shorter than an Airbus', so it can only be so long before rotation on its pitch axis causes the rear end to smack. The Airbus 320 family sits on higher gear, so in theory, you can stretch it longer.

Bubba

 

[redflyer65]

Like the A321. I think all economy class it's around 200 pax. Spirit has a couple at full load.

 

[ROSWELL41]

A Spirit A321 holds 218 passengers.

 

[igneousy2]

That's exactly the theory on the NG's increased ref speeds. Increase the speed and you won't hit the tail.

so the saying goes...but you have slightly LESS clearence at LOWER weights...if what you're saying is the entire answer, then I would expect the higher weights to have the least clearence.

 

[CesnaCaptn]

Flaps 30 vs 40 in the -700 only changes ref by a few knots. In the -800 and -900 it makes about a 10 knot difference. That must be because of deck angle on the long bodies. The plane will fly slower at flaps 30, but you would have a tail clearance issue.