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Ward86IND
Topic Author
Posts: 231
Joined: Thu Apr 27, 2006 6:13 am

AirTran 737's And De-Rated Takeoffs

Tue Jun 09, 2009 3:49 am

So I work at IND and am around the airfield a lot. I watch takeoffs all the time and have found that out of all the aircraft, AirTran's 737's eat up the most runway, even more than AA and DL's MD-80s (and most of the time even FX DC10s!), and on a consistent basis. One day I was watching beside 23L and as most aircraft used between 5500-6500 feet or so for takeoff (including CRJs, ERJs, A319s, 737s (SWA) etc), Airtran's 737 used at least 8000 feet. After seeing this again today, I went onto flightaware and saw that the flight was to Atlanta....it's not like it was fully loaded. By comparison, SW's 737NG's usually use somewhere between 5000 and 6000 feet for takeoff. The 737NG has plenty of power, so obviously there is a substantial derate taking place consistently. Also, Airtran's 717's seem to eat up not nearly as much runway, so this is specific to the 737NG of Airtran. I wonder if this is some kind of company policy, and, while clearly other carriers use derated takeoffs, why none of them seem to derate to the extent of Airtran. Clearly there is a cost benefit with maintenance, but at what point do the elongated takeoff rolls and slow climb begin to cut into fuel costs, tire costs, etc.?
 
OPNLguy
Posts: 11191
Joined: Tue Jun 15, 1999 11:29 am

RE: AirTran 737's And De-Rated Takeoffs

Tue Jun 09, 2009 4:18 am

All 737-700s are not created equal. What engine variant do the AirTran 737-700s use? 22K? 24K? 26K? 28K?
 
Mir
Posts: 19491
Joined: Mon Jan 05, 2004 3:55 am

RE: AirTran 737's And De-Rated Takeoffs

Tue Jun 09, 2009 6:21 am



Quoting Ward86IND (Thread starter):
I wonder if this is some kind of company policy

From what I've heard, AirTran leases their engines, and they pay based on how much power they use. So would make sense for them to derate the takeoffs as much as possible.

-Mir
 
DescendVia
Posts: 141
Joined: Sun Jan 18, 2009 4:26 am

RE: AirTran 737's And De-Rated Takeoffs

Wed Jun 10, 2009 1:09 am



Quoting Ward86IND (Thread starter):
By comparison, SW's 737NG's usually use somewhere between 5000 and 6000 feet for takeoff

Using them is like comparing apples to bananas. WN does not derate the take off as I know it.


Quoting Ward86IND (Thread starter):
I wonder if this is some kind of company policy, and, while clearly other carriers use derated takeoffs, why none of them seem to derate to the extent of Airtran

It all depends on engine out data. The parameters are obviously met so they derate to the max. It also depends on the engine manufacturer. For example our 757s (UA) were limited by P&W to a max of 48*C but about a year ago we were allowed to increase this to 65*C. So there are many variables.
 
EA772LR
Posts: 1285
Joined: Wed Mar 07, 2007 2:18 am

RE: AirTran 737's And De-Rated Takeoffs

Wed Jun 10, 2009 4:19 pm



Quoting OPNLguy (Reply 1):
All 737-700s are not created equal. What engine variant do the AirTran 737-700s use? 22K? 24K? 26K? 28K?

FL has the CFM56-7B rated at 26K, but their MTOW is also listed at 155K, so I highly doubt that their engines are rated at 26K.

http://www.airtran.com/aircraft/boei...g_737_aircraft_specifications.aspx

That is probably just a misprint. That would be an excessive amount of power. I'd be willing to bet FL's 73Gs are rated at 22K, maybe 24K and are probably either de-rated, or FL has cut back on takeoff thrust to lower fuel/mx costs.

By the way OPNLguy, there is no CFM56-7B rated at 28K, although I wish there was, as a 28K engine would be handy on the 739ER.
 
Ward86IND
Topic Author
Posts: 231
Joined: Thu Apr 27, 2006 6:13 am

RE: AirTran 737's And De-Rated Takeoffs

Wed Jun 10, 2009 11:25 pm



Quoting Mir (Reply 2):
From what I've heard, AirTran leases their engines, and they pay based on how much power they use. So would make sense for them to derate the takeoffs as much as possible.

-Mir

This would make a lot of sense.

Quoting DescendVia (Reply 3):
Using them is like comparing apples to bananas. WN does not derate the take off as I know it.

Actually WN does derate whenever possible, even at MDW! (I know because I picked a WN captain's brain a few months ago while waiting for a flight)

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