I agree. The recorded figures are correct, having been reproduced several times. The effect of the weight variations on stall speed, ie the reaction of the model, isn't credible.
BTW, am I correct in assuming that V1 values have available runway length as a component? If so the Vspeed gauge doesn't require it so can't calculate it.
Gerry Winskill bones wrote:
If you can vary the weight between 246,000 and 400,000lbs then your stall speed figure variation of just 18kts is seriously wrong. bones -----Original Message----- From: jhb-bounce@xxxxxxxxxxxxx [mailto:jhb-bounce@xxxxxxxxxxxxx] On Behalf Of Gerry Winskill Sent: 01 July 2007 18:42 To: jhb@xxxxxxxxxxxxx Subject: [jhb] Re: Which Speed? But at Actual All Up Weights varying between 400,000lbs and 246,000 lbs, depending on fuel loaded, which is quite a large variation. It's just payload, not fuel, that can't be reduced, though it can be increased. Gerry Winskill bones wrote:Except that will explain why your speeds are so narrow - the aircraft is always operating at max payload weight. bones -----Original Message----- From: jhb-bounce@xxxxxxxxxxxxx [mailto:jhb-bounce@xxxxxxxxxxxxx] On Behalf Of Gerry Winskill Sent: 01 July 2007 17:33 To: jhb@xxxxxxxxxxxxx Subject: [jhb] Re: Which Speed? The Max AUW is the same as quoted by Airbus. I'd guess he's just aken the fuel wt from MAUW and put the rest in as aircraft weight, including an unspecified load weight. It handles and performs so I'm not too bothered about his shortcut. Gerry Winskill bones wrote:If it is overweight with just full fuel and no payload then he's either got fuel capacity wrong or the Max AUW. bones -----Original Message----- From: jhb-bounce@xxxxxxxxxxxxx [mailto:jhb-bounce@xxxxxxxxxxxxx] On Behalf Of Gerry Winskill Sent: 01 July 2007 16:32 To: jhb@xxxxxxxxxxxxx Subject: [jhb] Re: Which Speed? That was the first and obvious route I tried to take. To my surprise the FSX Payload Settins menu just has a single Staion 1 slot and that contained a default value of zero. Which didn't leave much scope for reduction. A check on a Default A321 shows it has a six slot variation capabillity, with a Default total passenger load of 14340 lbs. At least the A350 designer hasn't just used a default model, as many do. Gerry Winskill bones wrote:Surely it would have been better to reduce passenger payload? Or was the aircraft over MAUW with no pax on board? bones -----Original Message----- From: jhb-bounce@xxxxxxxxxxxxx [mailto:jhb-bounce@xxxxxxxxxxxxx] On Behalf Of Gerry Winskill Sent: 01 July 2007 13:50 To: jhb@xxxxxxxxxxxxx Subject: [jhb] Re: Which Speed? Definitely! I've just made one change to the aircraft.cfg. If full fuel loaded it exceeds MTOW, so I've reduced the centre tank capacity to correct. Gerry Winskill Alex Barrett wrote:Gerry, I was always taught that a general figure for Vr would be 1.1 x the aircrafts stall speed with flaps retracted. I actually downloaded the A350 yesterday and have started doing a repaint for it, but haven't yet flown it. In your opinion is it a "goer" as they say? Alex Gerry Winskill wrote:Having decided not to make assumptions about Vr, I ran a series of tests, at max and minimum takeoff weights, to find the takeoff speeds at the various permissable flap settings. I ran the tests hands off, with elevators trimmed up at 60%. I've got decent rpeatabillity, so..... I know it's nowhere as simple as a linear relationship but is there a reasonable difference I can apply to the takeoff speeds, to get to Vr? V1 and V2 are not, I guess, capable of being arrived at by rule of thumb. Gerry Winskill Gerry Winskill wrote:A couple of days ago I downloaded the FSX version of the wide bodied Airbus A350. It looks good and flies well. One advantage of the Airbus familly, to users of Fsim, is that commonality of panels etc is a real aircraft feature. That left me needing to modify the Vspeed gauge, to reflect the A350's weights and V numbers. I've not managed to unearth any V number data but weights and performance are available, from the Confidential sale contract conditions that have found their way onto the Net.. For Vr I'm assuming that the numbers won't be far off those for the rest of the familly. Producing Vref data should be straightforward, since all I have to do is determine the dirty stall speed, at the same altitude and with zero wind, for a set of All Up Weights. Only it wasn't straightforward. The aircraft.cfg gives the dirty stall speed as 124 kias, without reference to any weight. In fact there seems to be no Aircraft.cfg facillity for varying stall speed with weight. The difference between the stall speeds I determined and the Aircraft.cfg figure were big, to enormous! At Max Permissable Landing Weight of 400,000 lbs it stalled at an indicated 99 kias, with the Stall Warning following a few knots below that. At the bottom end of the weights, with just the minimum permissable fuel reserves, it stalled at 80 kias. As if that isn't bad enough there was a discrepancy between the AIS / Map indicated speeds and the Ground Speed recorded in my Checks gauge. When ASI read 99 the GS was 110. With ASI at 80, GS was 88. Where does that leave me? It seems reasonable to take the actual stall speeds recorded, as the route to calculating the Vref figures for the simulated aircraft, but should I use the ASI or the higher GS figures? In passing, the figures for dirty stall speed in most of the aircraft I fly seem to be higher than the actual speed at which the stall occurs. Which explains why I can seldom hold off enough to get the Stall Warning klaxon to sound, when landing. Which makes it seem likely that the actual stall speed data is held somewhere other than the Aircraft.cfg. The fact that there is an actual variation of stall speed with weight seems to bear this out, since that ain't possible from the data held i the Aircraft.cfg. This is a serious limitation of FSX and its predecessors, since lapses of concentration allowing the speed to fall to the stall don't produce the wake up effects of a real life lapse! Gerry Winskill-- Alex Barrett Turbine Sound Studios (+44) 0121 288 3195 alex@xxxxxxxxxxxxxxxxxxxxxxx http://www.turbinesoundstudios.com
