Hey fellows,

so basically the way that i setup my stabilizer trim for takeoff is by pressing double click on the fmc button near the stabilizer trim on the takeoff page (after filling all of the perf init page: weight, runway...) but recently i was trying to make it be more realistic, so i took the page that i printed using Topcat, and filled with the number for the stabilizer trim setup for takeoff, for instance 27.46

the number that i get 4.81 is not match the 5.33 that i get if i am double clicking.

i filled the payload/pax correctly.

basically my question is: should i use topcat to calculate the stabilizer trim, and the v's speeds for takeoff? or should i rely the FMC?

which method are the pilots using?

i am truly sorry if it has been asked before i couldn't find any threads on the topic.

cheers.

I have noticed that TOPCAT often gives me wrong V speeds (especially the V1) with the PMDG:s 744X. They are often very close to each other but I always use the FMS calculated speeds. I haven't checked the trim setting difference but you should go with the FMS calculated trim setting as that is the real one calculated for that specific configuration.

Honestly guys as long as its in the ballpark it doesn't really matter - the takeoff trim isn't something you can actually set precisely to the hundredths place or whatever in the real airplane. The scale on the pedestal is totally analog and as long as it's reasonably close to the correct setting you're going to be fine. 4.81 vs. 5.33 are going to feel nearly identical - you'd just compensate if it felt a bit to heavy in either direction once you get into the air.

Ryan, that's true but with computers we don't get the real feedback on how heavy or light it feels and that's why I want to have the exact settings. Of course we learn to know the plane by time but anyway I always go with PMDG figures over TOPCAT.. I mostly use TOPCAT for FLEX and braking calculations.

Ryan is right. Real life or sim, the trim setting is just a starting point. It puts you roughly in trim for initial climb. Once flying you trim as normal. Setting to one or two decimal places makes no difference. Same with V speeds (in the sim). In real life they need to be set accurately for safety. TOPCAT is based in real data, but that may not work too well in the sim.

As Ryan mentioned, as long as the trim setting is close to the calculated figure then you will be fine. In the sim it is fairly pointless trying to find the perfect take off trim setting because we all have different hardware, null zones & sensitivity settings. Just use the TOPCAT do PMDG figures and Stick with it.

 

Regarding V speeds, it is definitely better to stick with TOPCAT rather then the PMDG FMC calculated speeds, TOPCAT is calculating your minimum climb gradient on a single engine.

Thanks everyone, Ryan thanks for responding to my thread.

my last unasnwered question is, are the pilot using to calculate those values? thanks again, cheers.

Depends on the airline, Dispatch provide the load sheet, many now use onboard laptop or iPad software like TOPCAT, some still use the runway specific charts, you can also have the data uplinked.

We use the Boeing OPT (Onboard Performance Tool) to calculate Assumed Temperature and Vspeeds. Trim we get from the FMC once weight and ZFW CG is entered.

Depends on the airline, Dispatch provide the load sheet, many now use onboard laptop or iPad software like TOPCAT, some still use the runway specific charts, you can also have the data uplinked.

thanks very much!

 

We use the Boeing OPT (Onboard Performance Tool) to calculate Assumed Temperature and Vspeeds. Trim we get from the FMC once weight and ZFW CG is entered.

that's my experience with pilots when i am lucky enough to get into the cockpit, so that's great to know! thanks' cheers.