Hi,

Does the FMC of the PMDG 737NGX compute the reference speeds for take off and landing according to the altitude of the runway too or only according to the weight of pax and fuel ?

Thanks.

 

Gilles Menghetti.

 

 

Does the FMC of the PMDG 737NGX compute the reference speeds for take off and landing according to the altitude of the runway too or only according to the weight of pax and fuel ?

 

It uses the balanced field method:

https://en.wikipedia.org/wiki/Balanced_field_takeoff

737-800W/CFM56-7B26 FAA

Category C/N Brakes

TAKEOFF AND LANDING Text

 

Flight Planning and Performance Manual

 

 

Takeoff Speeds

The speeds presented in the Takeoff Speeds table as well as FMC computed takeoff speeds can be used for all performance conditions except where adjustments must be made to V1 for clearway, stopway, anti-skid inoperative, thrust reverser inoperative, improved climb, contaminated runway situations, or brake energy limits. These speeds may be used for weights less than or equal to the performance limited weight.

The FMC will protect for minimum control speeds by increasing V1, VR and V2 as required. However, the FMC will not compute takeoff speeds for weights where the required speed increase exceeds the maximum certified speed increase. This typically occurs at full rated thrust and light weights. In this case, the message "V SPEEDS UNAVAILABLE" will appear on the FMC scratchpad and the takeoff speed entries will be blank. Takeoff is not permitted in this condition as certified limits have been exceeded. The options are to select a smaller flap setting, select derate thrust and/or add weight (fuel). Selecting derate thrust is the preferred method as this will reduce the minimum control speeds. Note that the assumed temperature method will not help

this condition as the minimum control speeds are

determined at the actual temperature and therefore are not reduced.

Does the FMC compute reference speeds in the real aircraft or do they still use flip charts?

Does the FMC compute reference speeds in the real aircraft or do they still use flip charts?

Yes, if the airline wants that option. Paper tables are still used, however many operators (mine included) use the Boeing Onboard Performance Tool (an iPad app) for all takeoff and landing performance data.

 

Mike Archer

Yes, if the airline wants that option. Paper tables are still used, however many operators (mine included) use the Boeing Onboard Performance Tool (an iPad app) for all takeoff and landing performance data.

 

Mike Archer

 

The company material i have access too now use the Boeing OPT or EFB on there ipad.

 

They follow the EFB Contingency Flow Chart – App(s) unavailable or EFB(s) unavailable and print out the necessary RTOW charts, Navtech charts and download the PDFs to ibooks. They will always have access to paper trip kits. But if the crew suffer dual EFB failure, the likelihood is the crew will be provided with a replacement EFB device or worst case paper backup documentation

 

Below link is a Europe based company RTOW for KOS in Greece (cutout company name at top)

 

https://www.dropbox.com/s/l6vaajp4umxnbya/Photo%2015-12-2016%2C%2015%2006%2056.jpg?dl=0

Does the FMC compute reference speeds in the real aircraft or do they still use flip charts?

 

Both actually.  We use v-speed from performance data created by our company but there are time when the v-speeds need to be changed after block out for various reasons.  When that happens we use the FMC QRH speeds.

 

 

after block out for various reasons.

 

Like having to depart EWR...always? Haha...penalty boxes are the worst.

Until quite recently we used for landing performance a laminated A4 piece of paper based on our performance preamble and for departure we used aerodrome specific performance booklets.

 

You'd have to go in with your take off weight and starting with 26k then see how much you could reduce thrust by!

 

We operate almost 2000 flights a day and sometimes 6 sectors! Thankfully we went paperless! (OPT)