[jhb] Re: Which Speed?
- From: "bones" <bones@xxxxxxx>
- To: <jhb@xxxxxxxxxxxxx>
- Date: Sun, 1 Jul 2007 18:57:51 +0100
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
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
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