Yesterday, I received this message from SimBrief when planning a flight from SKBO to SKBQ using a B-737-800 (PMDG). Runway selected was 14L in SKBO. According to SimBrief, the TOW was 150,091 lbs, and the maximum TOW was 174,900. The departure was planned against the wind direction. The rwy lenght is 12,467 ft. I don’t understand why the departure rwy may be inadequate for takeoff. What is the meaning of this message?
174,900 is the structural MTOW of the aircraft, not the MTOW for that runway on that day in the specific conditions.
The latter can be found in the Takeoff and Landing Report section of the OFP, as PMRTW and/or PMTOW, in hundreds of pounds for some reason.
Yours was probably less than 150,091, so PRMTW/PMTOW of 1500 or lower.
That means, with the given weights, selected runway and weather conditions, your plane would not have been able to legally take off.
In practice, a regular takeoff probably would have gone fine; but an aircraft must be able to reject a takeoff at V1 and still stop before the end of the runway.
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Minimum V1 - the minimum permissible V1 speed for the referenced conditions (temperature, wind, pressure altitude, weight, thrust, runway etc) from which the takeoff can be safely completed after the critical engine has failed at the designated speed (VEF)
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Maximum V1 - the maximum possible V1 for the referenced conditions at which a rejected takeoff can be initiated and the aircraft stopped within the remaining runway (or runway plus stopway where available)
Presumably, Simbrief’s takeoff performance calculator determined that this was not possible, i.e. there was no valid V1 speed (the minimum V1 was higher than the maximum V1) for a takeoff weight of 150,091 lbs, on that runway, with the wind and other weather conditions on that day.
Regards,
Tim
You are right. I checked the Takeoff and Landing Report and: 1.- The runway was wet, and thus 2.- The PMTOW was lower than 150,000 lbs. In fact, 148,600 lb. Thanks for your complete explanation of the SimBrief message.
Not to mention the 8300 foot elevation. Altitude robs a lot of power from the engines too, thus causing a longer takeoff run since you don’t have the same takeoff thrust as lower airports.