[jhb] Re: Which Speed?
- From: "bones" <bones@xxxxxxx>
- To: <jhb@xxxxxxxxxxxxx>
- Date: Sun, 1 Jul 2007 14:48:42 +0100
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
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