Misunderstanding of Summary Page?

[Bingo 3]

Hi,

 

I’ve been using the PFPX and TopCat for many years now. It is the best dispatch software on the market today.

 

It is particularly very useful in planning flights for heavy freighters like the PMDG 747-400. For every flight, I always load it up with maximum cargo to fit the route distance required, plus insuring that I have at least 30,000 lbs. of fuel remaining at the destination airport. This extra fuel is required to keep the main fuel pumps submerged to prevent overheating.

 

For me, the “Summary” page is a very important tool to make sure I do not exceed, zero fuel weight, take-off & landing weights , or anything else of importance. After several iterations of calculating and re-planning, I come up with the correct weight configuration. I like the way PFPX denotes items in “red” that exceed limits.

 

Note - A while back this page was removed because it was thought to be unnecessary. However, enough users complained and it was reinstated…….I was very thankful.

 

I have discovered an issue, or possibly something I don’t understand. Attached are two image files of the Summary page, one is a “Prior to Topcat, Update & Release,” and the other is After Topcat, Update and Release. The Topcat part is where you get the takeoff and landing data prior to Updating and Releasing the flight plan.

 

What doesn’t make sense to me is when the following occurs before and after Topcat Take-off/Landing, Update and Release (note the red lines denoting the weights on the two image files):

 

Take-Off Weight Limit at KSDF changes from 874,999 to 768,669

Landing Weight Limit at KBOS changes from 662,197 to 805,121

 

Also attached is the PDF of this flight plan.

 

Appreciate your thoughts,

Bill Clark

 

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UPS581 KSDF-KBOS (04-Jul-2018) #1.pdf

[Mklemme 9]

Hi Bill,

 

On the OFP where the takeoff and landing performance data is placed you see that FIELD is the limiting factor. This means that runway length or obstacle height for the given conditions is limiting the max allowable weight. So for takeoff, before the update and release the MTOW limit is the structural limit of the plane (ie 874,999 lb) whereas after the update and release the MTOW is reduced to 768,699 lb due to runway length available for the conditions, obstacle height, engine out requirements, etc. I can't explain the landing limit however as it is higher after update and release which shouldn't be the case, so maybe something has gone haywire in transposing the figures from TOPCAT to PFPX or there is an issue with the aircraft profile perhaps.

 

Michael.   

[Bingo 3]

Quote - On the OFP where the takeoff and landing performance data is placed you see that FIELD is the limiting factor. This means that runway length or obstacle height for the given conditions is limiting the max allowable weight. So for takeoff, before the update and release the MTOW limit is the structural limit of the plane (ie 874,999 lb) whereas after the update and release the MTOW is reduced to 768,699 lb due to runway length available for the conditions, obstacle height, engine out requirements, etc. I can't explain the landing limit however as it is higher after update and release which shouldn't be the case, so maybe something has gone haywire in transposing the figures from TOPCAT to PFPX or there is an issue with the aircraft profile perhaps.

 

Hi Michael,

 

Thanks for your response.

 

Yes, the departure/arrival “Fields” could or would impose limits on weights as you stated for those good reasons.

 

We do know PFPX is aware of the runway lengths at the departure and arrival airports in making its initial calculations, and since Active Sky is providing weather information to PFPX, then a lot of data is available. That raises a good question about the higher landing weight as to why?

 

The runway lengths are pretty long, and according to Foreflight (iPad real world flight planner) they are:

 

KSDF RWY 17R = 11,887 x 150 ft.

KBOS RWY 22L = 10,001 x 150 ft.

 

Attached are 3 new images of my 747-400F weight data:

 

TopCat  weight data

PFPX weight data

PMDG weight data

 

There are some minor differences with Empty weight versus Dry Weight, but everything is in alignment.

 

I hope the Aerosoft moderator can also provide some insight to this as well as your thoughts?

 

Bill Clark

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