V-REF speeds. What am I doing wrong?

[NicholasB 0]

Hi Folks, I am finding that the NGX does not seem to like the calculated V-REF speeds from the FMC CDU. I will try to illustrate what I mean, however, I am sure I am the one at fault. Lets say that the recomended V-REF speed for flap setting 30 as depicted in the CDU is: 139 knots. I get myself fully configured in flap 30 and maintain the 139 knots as required. Nevertheless, this combination of flaps 30 and 139 knots always has the aircraft in a nose down pitch in what seems like is going to be a nose wheel first touchdown. In fact regardless of what the recomended V-REF speed is, the aircraft is always nose pitch down for short final. I have found that a speed that is between 5-10 knots slower than the calculated (FMC) V-REF speed produces the best and smoothest touchdown and gentle flare. In another experiment I maintained the advised V-REF speed (lets say 139 knots again) right until the very last moment before I put the power levers to idle, hoping the speed would again bleed of nicely during the flare, yet I Found by doing so that the aircraft would gain a little altitude due to pitch and the 139 knots which seemed to be to fast for a smooth touchdown. The aircraft would not hit tera firma untill the speed was at about 125 knots. So repeating the above, I have found that if I V-app at 130 knots instead of the suggested 139 knots I have a much better and what appears to be safer landing. I have studied these landings allot in replay comparing the different speeds and my conclusion ( I am mistaken i"m sure) is the the NGX seems to prefer slower V_ app and V-ref speeds that what is advised in the FMC. What am I doing wrong here? I have performed trials in both full autoland and manual and the result is the same each time. Also for these expirements I have been using only the default fair weather conditions in FSX and using the active runways. so calm winds I would really love for someone to clear this up for me and help a fellow sim pilot out. Many Thanks, Nicholas Boskovic P.S I hope the above makes sense!!

Edited August 16, 2011 by NicholasB

[henri5 16]

It could be the trim setting... Are you using the values from the Approach page that comes on during the flight? How did you get the VREF value? henri

[NicholasB 0]

It could be the trim setting... Are you using the values from the Approach page that comes on during the flight? How did you get the VREF value? henri

Hi Henri, Yes I am using the values on the approach page from the FMC CDU then i select the v-ref speed, in the scratch pad from the value depicted next to flaps 30 and then insert that in the blank space below on the same page. that value is also then depicted on my PFD. I am at a loss. Thanks,NIck

[Paul Deemer 13]

I had this problem with the Level-D. Are you using the FMC options to set your Fuel, Cargo, and Passengers Configuration? Once you do that write down the following information. Your ZFW weight and CG Percentage as you will need this info later when entering all the info into the FMC. The problem with the Level-D was I was nose heavy. I did not realize that unlike the PMDG 747-400 where the Pax and Cargo pages are seperate, the Level-D Pax and Cargo is all the same thing. So when I was loading up for a cargo run I had full cargo but what I didnt know was i had full pax too so i was way heavy. Once I got rid of the pax the problem went away. So if you are nose heavy it sounds like either you are exceeding the MTOW or your not loading the plane correctly. Example of the flight I am Flying right now. Manchester (EGCC) to Madeira (LPMA)For a 4 hour flight with a 1 hour reserve I have it setup as follows 30,000 lbs FuelCargo, 14,000 (6,500 lbs AFT / 5,500 lbs FWD)Zero Fuel Weight is 133.7 Gross Weight 163.7 and the CG is 24.1% The FMC currently shows me a Reserve of 10,000 lbs which is a little more than I need because 6,800 lbs will give me about an hour of reserve flight time.

[martin-w 3,234]

Strange one, flown several flights now and found VREF to be smack on. In fact the correct approach speed should be VREF+5 I believe. Martin Wilby

[scandinavian13 5,192]

Is your speed set to True or Indicated in the FS Options pane?

[lassekronborg 43]

I tried this with the SFP installed. The FMC calculated Vref seemed about 10kts to high. I have no landning attitude problem with the non-SFP aircraft //Lasse

[NicholasB 0]

Is your speed set to True or Indicated in the FS Options pane?

indicated airspeed is set in the FSX options bar in the fsx game menu, so I assume that is not the problem. Lasse, when you say SFP do you mean "special field performance package"? if so, I'm not sure if the aircraft is configured as such or not. Still hoping for a definitive answer for this. Any of the PMDG boys can chip in here? Thanks, Nicholas Boskovic