HIGH ALTITUDE TAKE-OFF & LANDINGS

[Guest november678x]

>Yes, you enter the distance from the runway threshold in >hundreds of meters. Valid entries according to the manual >are -30 to 30 (i.e. -3000 m to 3000 m). In the PIC FMC it says FT for the RWY/POS field. If it

[Guest Martin]

The REF OAT one page 2 seems to be just that: a reference outside air temperature. It is used for V speed calculations. Since there is a field for assumed temperature on page 1, I assume (:-roll) that the REF OAT field should not be used for assumed temperatures, but for actual outside air temperature. (And if I'm not mistaken, isn't this field automatically filled in, at least in PIC? I guess you can enter another temperature if the temperature on the EICAS is incorrect.)Martin767 fetishistIt's a lot like life and that's what's appealing

[Guest Martin]

I suppose it's in meters on aircraft with "metric" configuration, and in feet on aircraft that use imperial units.Martin767 fetishistIt's a lot like life and that's what's appealing

[crvm]

degrees Celsius for a 4000m runway and a short hop. Note, to use the new engine performance data, you must select N1 on the A/T panel prior to takeoff. This will set thrust to the calculated derated N1 value." I think you meant to say 53 degrees Celsius?? Best Wishes,Randy J. [email protected]" A little learning is a dangerous thing"

[Guest november678x]

Ok I got it now Thanks, just 1 more thing lets say you take-off from a runway that is about 7000ft long, since it is short I need a higher thrust setting. Can I leave the assume temperature field for reduced thrust blank? Or you must enter at least the current temperature. The FMC PIC manual does not really say if you can leave it blank it just says you can enter any temperature from current to 64C. Thank You:-wave

[Guest Martin]

In real life the appropriate assumed temperature and/or V speeds is usually determined from a table that is unique for every runway (taking into account not only runway length but also surrounding terrain, obstacles etc.).In FS we don't have this "luxury", but we also don't have to care about engine wear and tear. So in FS, if you feel the runway is short, feel free to use full takeoff thrust (i.e. assumed temp = actual OAT), and if you think you have more than enough runway, feel free to reduce thrust as much as you think is reasonable.Martin767 fetishistIt's a lot like life and that's what's appealing

[Guest CYOW_pilot]

november678x,Vr is an aerodynamic speed approx 1.2 x the stall speed and since we are dealing with indicated airspeeds as such will only vary directly with weight. As weight goes up, stall speed goes up (for a given configuration / g and therefore so does Vr. Thefore, the FMC calculated Vr will be the same at sea level or 5,000 ft or at -40 or +40C.Similarly, Vref and V2 are aerodynamic speeds (Vref based on 1.3 x stall speed for that weight and configuration). They will not vary with temperature or altitude. Technically V2 could vary based on temp etc (thrust effects)if it starts tocome within the region of Vmca if you are very light, but we can disregard that for now. The FMC calculated data should be correct for Vref and V2.From my experience flying B707s/AWACS, these speed were simply looked up in a table with the only variable being weight. Similar deal for Vref.V1, however, will vary quite a bit since it must take into account the distance to stop (which will depend on winds, slope, temperature, weight etc) as well as to get airborne on one engine. V1 will therefore vary depending on altitude, temperature, thrust setting, runway contamination, runway length, runway slope and rotation speed, to name a few. Obviously PIC767 cannot account for all these variables so it probably gives a standard V1 for a non-critical runway length, dry level runway at ISA conditions. For high/hot, contaminated or short runways it will probably be too high (ie, V1 should be lower than the FMC calculated one).All in all, the FMC calculated speeds should be relied upon, with the exception of V1, which because of the factors mentioned above, will most likely be in error on the high side.Hope that helps you feel better about those FMC speeds.Kevin in CYOWKevin in CYOW

[Guest Martin]

>From my experience flying B707s/AWACS, these speed were >simply looked up in a table with the only variable being >weight. Similar deal for Vref. But, as I mentioned in this thread, the charts for the 767 also have altitude, temperature, takeoff wind, and runway slope as variables for the takeoff speeds. Of course, the only "big" variable is weight.Martin767 fetishistIt's a lot like life and that's what's appealing

[Guest november678x]

Thanks for the reply's they are very informative. Does anyone know where I can get performance charts for the 767-300ER? I have checked smartcockpit.com but nothing in there. Thank You:-wave

[Guest Martin]

Are these good enough?http://library.avsim.com/search.php?Search...=Root&Go=SearchAt least it covers the basics.Martin767 fetishistIt's a lot like life and that's what's appealing

[Guest november678x]

Yea those are perfect! They have a lot of information in them. Thank You :-)

[Guest CYOW_pilot]

Martin,I suspect the changes you see in the charts are very minor (a knot or two) (except for V1). I also assume we are not talking about "optimized" V speeds that may be used in cases of excess runway length.Technically, Vr must not be less than:a. V1;b. 1.05 Vmc;c. the speed required to accelerate to V2 by 35 ft; ord. a speed to ensure Vlof is at least 1.1 Vmin unstick (2 engines) or 1.05Vmin unstick (one engine out).Density altitude (temp/pressure) will have some effect on the engine thrust available and thus will have an affect on the acceleration to V2. Lower density alitudes = more thrust = quicker accleration to V2 which could allow for a slightly lower Vr (if the other factors are not limiting). Given the relatively short period of time we are talking about from Vr to V2 the change in thrust would likely only result in very minor changes to Vr.In the end, and in response to the originator of the thread, I would say that the FMC numbers are accurate enough (within a couple of knots)for take-off and Vref will not change with density altitude (weight dependent only) so the FMC numbers should be correct in all cases (I don't have access to an 767 AFM to confirm that though).Kevin in CYOW

[Guest Martin]

>I suspect the changes you see in the charts are very minor >(a knot or two) (except for V1). I also assume we are not >talking about "optimized" V speeds that may be used in cases >of excess runway length. Correct and correct. :-) For a given weight V1 varies with around 8-10 knots, Vr with around 5-6 knots, and V2 is usually the same.But V1 should also be adjusted for wind and runway slope which can change V1 with up to 11 knots (runway slope is of course not modelled in FS2002, but I don't see why the FMC shouldn't be able to use wind, temperature, and altitude in its takeoff speed calculations).Martin767 fetishistIt's a lot like life and that's what's appealing