Hi Derek,

SimBrief provides both the D-TO2 *and* Assumed Temperature. However, only one can be used at a time. Using the assumed temperature, the Thrust Limit page on the CDU will show a D-TO N1 %. Selecting the TO-2 option, the inserted assumed temperature gets deleted and (again) a D-TO N1 % will be shown for this option, which is very close to the assumed temperature value. Hence, either method can be used.

I can look into (obsolete) KLM Aircraft Operations Manuals [AOM], with Flaps 20 data only. I can also look into KLM’s FCOM, which only contains data for self dispatch Flaps 10 takeoff performance at Maximum Takeoff thrust - and intended only as last resort data (when the normal performance tool [LINTOP] is not available).

KLM does not allow fixed derate takeoffs so I have no data available for D-TO1 or D-TO2.

Using KLM’s AOM and a Flaps 20 Takeoff Speeds Chart, values are given for V1 DRY, V1 WET, VR, V2 for Takeoff Weights between 450 MT and 200 MT. Corrections to V1 and VR have to be applied, based on the calculated assumed temperature and Pressure Altitude. On top of that, corrections to V1 for wind and slope have to be applied. If the resulting value for V1 is less than VMCG, determined at the *actual* OAT, V1 has to be increased to VMCG. Similarly, corrections to VR are based on the assumed temperature.

For the Pax/Combi version of the 747-400 at EHAM, Flaps 20 and 22 degrees OAT, VMCG equals 125 KIAS. VR and V2 MIN are 125 and 145 KIAS. These values only decrease as Pressure Altitude increases.

Although the FCOM Flaps 10 data - both for the Pax/Combi and Freighter versions - is for maximum takeoff thrust and actual OAT, looking at an actual temperature of 50 degrees VMCG = 123 and VR MIN = 128 kts (Freighter), or 116 and 116 KIAS (Pax/Combi).

If you’d like to discuss these data tables in more detail, I would prefer to do this outside of this forum.

Kind regards,

Simon