Hello captains,At the moment I'm flying hight altitude airports in the Andes and have odd problems while taking off. Due to short runways related to the altitude I'm selecting an empty aircraft, 1/3 of fuel and follow all settings the FMC calculates (I even checked it against the books). However. When taking off (first 40%, then TOGA) the plane starts running but does not lift at all when reaching V2 even if I'm pulling the throttle back as far as I can (as the normal soft movement does not work at all). What is going wrong? BTW, it's not depending on the service pack, it was before as well. It seems to be linked to the load. I already opened an other thread quite a while ago but did not find it right now.

Did you set trim?

Hello captains,At the moment I'm flying hight altitude airports in the Andes and have odd problems while taking off. Due to short runways related to the altitude I'm selecting an empty aircraft, 1/3 of fuel and follow all settings the FMC calculates (I even checked it against the books). However. When taking off (first 40%, then TOGA) the plane starts running but does not lift at all when reaching V2 even if I'm pulling the throttle back as far as I can (as the normal soft movement does not work at all). What is going wrong? BTW, it's not depending on the service pack, it was before as well. It seems to be linked to the load. I already opened an other thread quite a while ago but did not find it right now.

Probably just a typo, but you should be rotating at vr, not v2, then positive rate shortly thereafter.

What conditions, weight and airport?

Check your takeoff page in FMC during preflight. Usually you´ll need a pretty high flap setting for such conditions (Flaps 10 or greater), check your CG, trim, use of assumed temperature or derated takeoff etc etc. Depending on your local conditions and rwy lenghts you might want to advance throttles to 70% manually while stepping on toe brakes and then letting the plane lurch forward as you set to/ga. Yes, this is done in real life. Also, consider using an SFP 800 with 27.000 lbs of thrust. This might be more realistic for Andes ops

Probably just a typo, but you should be rotating at vr, not v2, then positive rate shortly thereafter.

Agreed, it was a typo.

What conditions, weight and airport?

I'll come back to it this evening (in Europe) - my work will not run away...

Check your takeoff page in FMC during preflight. Usually you´ll need a pretty high flap setting for such conditions (Flaps 10 or greater), check your CG, trim, use of assumed temperature or derated takeoff etc etc. Depending on your local conditions and rwy lenghts you might want to advance throttles to 70% manually while stepping on toe brakes and then letting the plane lurch forward as you set to/ga. Yes, this is done in real life. Also, consider using an SFP 800 with 27.000 lbs of thrust. This might be more realistic for Andes ops

The density altitudes at certain times of the day will prohibit real world operations for airports at high altitudes because the runway is simply too short for the take off run required to get airborne...You certainly do not want to derate or use assumed temperatures at high density altitudes. You want max power, particularly on shorter runways...Andrew

Hello Axel:I regularly take off from high altitude airport in the Andes (-800WL) in Bolivia and Peru such as SPZO, SLLP, SLCB, SLSU and SLTJ without problems. I never load more than 40% total fuel in the tanks. Most flights from these airports are in the 350nm to 400nm range in real life for this very reason.As you program the FMC, it is quite important to check the trim recommendation it gives you and set it properly as acceleration at those altitudes is noticeably slower and you find that rotation happens quite late on the runway. Try SLLP (La Paz) which is quite high (13,300 ft) and has a long runway and see what happens there. Make sure that TOGA is indeed giving you full power.With regards to shorter high altitude and/or short runways, some airlines have special kits installed on their aircraft. Check the -800WL PMDG liveries and you will see that there is one for GOL, the Brazilian airlines that has such a version.Good luck and please report back!Roberto

At the moment I'm flying hight altitude airports in the Andes

Sounds fun, which airports?

Check your takeoff page in FMC during preflight. Usually you´ll need a pretty high flap setting for such conditions (Flaps 10 or greater), check your CG, trim, use of assumed temperature or derated takeoff etc etc. Depending on your local conditions and rwy lenghts you might want to advance throttles to 70% manually while stepping on toe brakes and then letting the plane lurch forward as you set to/ga. Yes, this is done in real life. Also, consider using an SFP 800 with 27.000 lbs of thrust. This might be more realistic for Andes ops

Victor,The airport is SLSU, ele 9524 ft, rwy lenght 10319 ft, settings exactly as calculated by the FMS when loading 1/3 of fuel and an empty aircraft (the -600), no reductions set. What you can see in the picture is the end of a "dynamic process" as I tried urgently to lift the plane by setting the trim from the calculated (and that was exactly the pre-set) 3.56 to 5.4 after it broke through all calculated speeds (it even reached the upper red tape). I slightly pulled the yoke when reaching Vr, a bit later I even pulled it to its extend while trimming until it rotated.What is going wrong there?

Hello Axel:I regularly take off from high altitude airport in the Andes (-800WL) in Bolivia and Peru such as SPZO, SLLP, SLCB, SLSU and SLTJ without problems. I never load more than 40% total fuel in the tanks. Most flights from these airports are in the 350nm to 400nm range in real life for this very reason.As you program the FMC, it is quite important to check the trim recommendation it gives you and set it properly as acceleration at those altitudes is noticeably slower and you find that rotation happens quite late on the runway. Try SLLP (La Paz) which is quite high (13,300 ft) and has a long runway and see what happens there. Make sure that TOGA is indeed giving you full power.With regards to shorter high altitude and/or short runways, some airlines have special kits installed on their aircraft. Check the -800WL PMDG liveries and you will see that there is one for GOL, the Brazilian airlines that has such a version.Good luck and please report back!Roberto

Hello Roberto,Yes (at least I believe) that I did all of the settings as they should. I just made the same t/o from SLSU with 1/3 of fuel and 50% load. The trim was calculated with 4.40 and v2 with 116 kn now (@ 15° flaps). It was almost the same - with a strange difference: at Vr the plane lifted slightly the front wheels and dropped back again with the same results as above described.

You certainly do not want to derate or use assumed temperatures at high density altitudes. You want max power, particularly on shorter runways...Andrew

That´s only partially true. A 600 with only about 9k lbs of fuel and no payload or pax will probably be able to use assumed temperature and/or derate depending on rwy extension even at high density altitudes. I say probably because I do not have the charts or topcat (which is based on Boeing figues) to back me up on this at this moment. But I find it highly unlikely that it would not be able to. Unless of course we´re talking about taking off from a 2500 ft rwy in La Paz on a bright hot summer day with high local pressure.

Victor,The airport is SLSU, ele 9524 ft, rwy lenght 10319 ft, settings exactly as calculated by the FMS when loading 1/3 of fuel and an empty aircraft (the -600), no reductions set. What you can see in the picture is the end of a "dynamic process" as I tried urgently to lift the plane by setting the trim from the calculated (and that was exactly the pre-set) 3.56 to 5.4 after it broke through all calculated speeds (it even reached the upper red tape). I slightly pulled the yoke when reaching Vr, a bit later I even pulled it to its extend while trimming until it rotated.What is going wrong there?

Axel, I don´t have any documentation with me right now, but I will try to reproduce your takeoff once I´m off call and get back home. With a 10,000 ft rwy you should´ve been able to takeoff using no derates and no assumed temps considering your TOW and takeoff flaps. I have no real or sim experience with high altitude airports, and as long as I don´t have the bibliography with me this remains an educated guess. But considering a certain Brazilian company that gets an 800 off the ground using a 1400ft rwy on very hot and humid days with 196 pob and 6000kgs of fuel, I still think you should´ve pulled it off.

Axel, I don´t have any documentation with me right now, but I will try to reproduce your takeoff once I´m off call and get back home. With a 10,000 ft rwy you should´ve been able to takeoff using no derates and no assumed temps considering your TOW and takeoff flaps.I have no real or sim experience with high altitude airports, and as long as I don´t have the bibliography with me this remains an educated guess. But considering a certain Brazilian company that gets an 800 off the ground using a 1400ft rwy on very hot and humid days with 196 pob and 6000kgs of fuel, I still think you should´ve pulled it off.

Thanks in advance. I'm sure that the error sits in front of the screen but I'm quite slow-witted as it seems at the moment. Of course I know that some airlines are flying under those conditions and I already used GOL's -800 having the SFP.

Ok, I gave it a try at 110,000 pounds in a -600. I used the same loads as you and it worked fined. Normal rotate and climb without any problems. Temp was 14C.