morrisond wrote:Actually the ACAP agrees with WIKI - if you go to 3-62 in the Boeing ACAP it shows 8,500' at ISA standard and 0 Elevation as well.

Originally I as looking at the wrong table as well (I went to the last one 3-65) and thinking 10,250' was optimistic.

Good catch, but I think we need to be specific here. There is no "wrong table" as such, only 2 different ones.

There is a table for the 25k lb thrust LEAP which shows the 737-9 take off at 0ft altitude as 10,250ft

There is ALSO a table for a high thrust variant with a 28k lb thrust LEAP which shows the 737-9 take off at 0ft altitude as 8,500ft

Useful information.

So we have a comparison.

Base 737-9 at 88t and 25k lb thrust at 0 ft altitude is

**10,250ft**

Base A321NEO at 93.5t and 33k lb thrust at 0 ft altitude is

**7,250ft**

High thrust 737-9 at 88t and 28k lb thrust at 0 ft altitude is

**8,500ft**

This of course compares the basic 737-9 with the highest thrust to an A321XLR which is 2 weight growth increments up on the basic NEO with the lowest thrust (33k lb)

The A321NEO is also available with 35k lb thrust if required - a 6% increase.

If the 737-9 12% thrust increase delivers 1,750ft better field performance, I'd expect the 321NEO's 6% increase to deliver something like 750ft, giving

High Thrust A321NEO at 93.5t and 35k lb thrust at 0 ft altitude being

**6,500ft**

Flightglobal state that the design intent for the high lift system is that V1 stays the same for the XLR as it is for the standard NEO

https://www.flightglobal.com/analysis/a ... 41.article

He adds that the intention with the switch to the single-slotted inboard flaps on the A321XLR is to reduce weight and complexitywithout exceeding the V-speeds of the original A321.

As V is constant, acceleration will be inversely proportional to mass.

The mass increase from 93.5t to 101t is 8%

Acceleration will be down 8%, and time will be up 8%

distance will be proportional to acceleration x time^2

i.e 0.92 x 1.08^2.

The increase in take-off distance will be 7%

Which means that

Base A321XLR at 101t and 33k lb thrust at 0 ft altitude is going to be (7,250ft x 1.07) =

**7 750 ft**

High thrust A321XLR at 101t and 35k lb thrust at 0 ft altitude is going to be (6,500ft x 1.07) =

**7 000 ft**

Considerably less than the 737-9 MAX, and squarely in 757-200 field performance territory

757-200 figures from here

https://www.boeing.com/resources/boeing ... 757_23.pdf

Base 757-200 at 116t and 37k lb RR 535E4 at 0ft altitude being

**7,250ft**

Base 757-200 at 116t and 37k lb PW 2037 at 0ft altitude being

**9,500ft**

High thrust 757-200 at 116t and 40k lb RR 535E4B at 0ft altitude being

**6,500ft**

High thrust 757-200 at 116t and 40k lb PW 2040 at 0ft altitude being

**7,500ft**

If the XLR calculation above is valid, that will put the XLR field performance somewhere between the RR powered 757-200 and the P+W powered 757-200.

The XLR of course flies a LOT further and therefore is disadvantaged in this comparison

Rgds