Lifting off before VR

[karakayab 0]

Hi,I tried to find clear solution or an advice for my problem but no clear info anywhere.... so as you can see topic title aircraft lifts offf automatically before Vr.... everything is ok ( FMC settings, speed and fuel calculations and trim )Problem accours every take off.... automatically lifts off and I lost control but I try to manage good climb but almost it is tail strike :(you can find below some value from my latest test flight to show you problem... I think it is trim problem but I didn't understandI have been using Level-d 767 since 2004 and I haven't this kind of problem with 767... everything is ok....Units: LbsLPPT / Runway03ZFW: 486.268Payload : 92.180 ( pax+cargo)Fuel : 265.880 ( calculated for LPPT>SBGR )Reserve Fuel : 33.4Flaps: 10 ( or 20 it doesn't change )V1:148 VR: 162 V2:175Trim: 6.0 CG: %23Thanks

[scandinavian13 5,192]

Hardware trim axis assigned?

[Superpilotv2 2]

Trim: 6.0 CG: %23

You set the trim to 6 up? This setting is way too high. Try a lower setting like 4 and it will change.

[basa 0]

You set the trim to 6 up? This setting is way too high. Try a lower setting like 4 and it will change.

6 seems to be a correct trim setting as per the table in page 1-4 of the manual for a CG of 23% and a TOW of 320000 kg.

[SGrindstein 0]

Remeber at lift off befor VR happends in real life to. Especially if it's windy. Trim calculation does not take into account windSteinar Grindstein

[NedH 0]

Remeber at lift off befor VR happends in real life to. Especially if it's windy. Trim calculation does not take into account windSteinar Grindstein

That raises an interesting question: Suppose for simplicity that VR is 150kts and you have a headwind blowing down the runway at say 25 kts. When you reach VR, your ground speed is only 125 kts. What's your airspeed when the wheels leave the ground? And more importantly will the plane fly then?

[basa 0]

That raises an interesting question: Suppose for simplicity that VR is 150kts and you have a headwind blowing down the runway at say 25 kts. When you reach VR, your ground speed is only 125 kts. What's your airspeed when the wheels leave the ground? And more importantly will the plane fly then?

You are ready to go lined in the runway end, and there is a headwind of 150 kts, now you just pull back the yoke to raise the aircraft nose and...ooops you are flying, aren't you?.

[karakayab 0]

Hardware trim axis assigned?

through FSUIPC ? No.... I haven't enough info what do I do about it

[scandinavian13 5,192]

To those discussing airspeed, remember that it is AIRspeed. This has nothing to do with wind at all. Vr is an airspeed, not a groundspeed, so winds are irrelevant. V1 may take into account winds in its calculation, because it should take into account the amount of ground covered on that particular runway (or a runway of that length), but after its calculation, there is no wind adjustment. That's a slight simplification of everything, but for all intents and purposes, once you have the numbers, ignore the wind's effect on them.If you're standing still (not moving) and the wind is blowing by you at 40 knots, your airspeed is 40 still knots, despite your lack of movement across the ground. I can take a 152, put it in slow flight with a stiff headwind (at altitude) and fly "backwards" (relative to the ground) if the wind speed is greater than my airspeed.

through FSUIPC ? No.... I haven't enough info what do I do about it

A trim axis assigned in FS would be enough. A trim axis defined anywhere really. The post earlier about your trim (6.0) being too high is more likely the answer, however.

[El padrino 2]

The post earlier about your trim (6.0) being too high is more likely the answer, however.

I've put the approximate figures in a small excel I've done (based on the PMDG manual) and it calculates, given the weight and the CG, that the trim should be 6. Was wondering whether the 23% CG is correct. Seems a bit low to me. Maybe somebody can tell us the range of normal CGs...

[SGrindstein 0]

If the wind speed and direction have changed after the FMC has been completed and the new wind is not loaded into the box, the speed you got the first time may be too high in relation to current conditions at take-off, and when you will get the lift off before a calculated.Steinar Grindstein

[scandinavian13 5,192]

If the wind speed and direction have changed after the FMC has been completed and the new wind is not loaded into the box, the speed you got the first time may be too high in relation to current conditions at take-off, and when you will get the lift off before a calculated.

You will lift off before the calculated runway distance, but not the calculated speed.As mentioned above, the speeds are airspeeds. As such, if the wind is stronger, your airspeed will be higher from the very start (standing still at 0GS with a 10KT headwind means your airspeed is 10), and you will still lift off at that calculated speed.

[MrKen 3]

Just out of curiosity, I plugged those weights into the PMDG load manager & both CG and trim are correct. On the Takeoff Ref page on the FMC I got trim:6 @ 21% cg.I was using the sliders & fudged the numbers a bit, but they're pretty close, maybe 1-2k lbs change each on zfw, pax/cargo & fuel load.

[captainklm 1]

Takeoff may seem easy but I have a small question. How much do I pull back on the yoke? Defiantly not all the way back. On videos I see the elevators and They don't go up much. Only 1/4 or something. How much do you guys pull back on the yoke and how long for on average?

[yos233 1]

Takeoff may seem easy but I have a small question. How much do I pull back on the yoke? Defiantly not all the way back. On videos I see the elevators and They don't go up much. Only 1/4 or something. How much do you guys pull back on the yoke and how long for on average?

Pull back far enough to achieve 3 degrees of pitch per second. The amount changes with differing COG.