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ESzczesniak

Boeing 737-700 Takeoff Performance Calculations

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I know this is a topic that comes up from time to time and was hoping that the state of these calculations had improved since a year or two ago when I last saw a topic on this.  I fly the PMDG 737 almost exclusively (hard waiting for it in V4).  I tend to fly in some smaller airports.  A lot around Alaska at places like PASI and PAJN.  I'd love to be defaulting to the 737-700 over the 737-800, as some of these runways either require a turn around on the runway or are a bit shorter.

Problem is that I have a decent calculator for the 737-800 (rather good actually, TOPCAT), but not the -700.  The TOPCAT profile is for the CFM56-B22, not -B24 engines modeled on the PMDG.  So my question is what resources do you guys have for calculating derate, assumed temp, and/or both?  I'm happy to do it by hand, but haven't been able to locate the materials for this.  Or is there a way to mess with the TOPCAT profiles?  I very much wish we could get a -700 -B24 profile in TOPCAT, but it looks like that development is dead.  Thanks for any help!


Eric Szczesniak

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I use TOPER, it does model the -7B24 engines for the -700.  However, it only provides a temperature derate and not a flex derate.  Also, it does not include obstacle clearance which TOPCAT does provide.  However, it will give you a DTO temperature and V-speeds although I stick to the V-speeds given to me by the FMS after I set the temperature.  TOPER also does the -600 variant with the 7B22 engines, which is what I fly a lot of in BBJ livery.


Dan Downs KCRP

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Thanks!  I perhaps should have mentioned that I've been eyeing that.  I really wish it would do flex as well as assumed temp.  It seems it's likely the best option, but for some reason I do like the flex derates. 


Eric Szczesniak

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15 hours ago, ESzczesniak said:

Thanks!  I perhaps should have mentioned that I've been eyeing that.  I really wish it would do flex as well as assumed temp.  It seems it's likely the best option, but for some reason I do like the flex derates. 

The differences between flex and derate are there but they are subtle, but as long as you don't need to bump the thrust (fire wall the levers) I consider N1 the same as N1.  For example, TOPPER  gives me DTO+60C, I will enter 60C and note the N1 and then find perhaps a DTO2 with the same N1, maybe it is DTO2+34C (I don't have the NGX running right now to check).  Or you can just accept that it is a simulation and takeoff with DTO+60C.


Dan Downs KCRP

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