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[RESOLVED] VREST VL/VTO F+W Error


Castello
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The F + W Values for both Wet and Dry (displayed in the respective VREST Sub-Meus), for both VTO and VL do not change with any changes to:

  • Altitude
  • Stores
  • Adjusting BAW to match OWT
  • Adjusting BAW/OWT above actual values
  • Changes to onboard fuel

The VL and VTO F+W Weights displayed seem to be swapped. As the VTO Fuel restriction is greater, and therefore the allowed maximum F+W calculated should be a lower value.

What actually appears to be happening is that the VTO F+W Displayed is consistently higher than the VL F+W Displayed.

 

I will try and attach a Track as soon as I can.

 

For example:

  1. BAW and OWT are 14200lbs
  2. Maximum Dry VTO F+W is displayed as 4400lbs
  3. This would imply that the maximum GWT for Dry VTO is 18600lbs
  4. Dry VTO was actually achieved at 22500lbs GWT

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  • 4 weeks later...

In this track file you can see that even after adding stores the calculated F+W never changes. It stays at its value. Also you can see that you are able to perform a vertical takeoff while being massively over the weight limit: Fuel set to F+W and 4 GBU-38+litening+gun.

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  • RAZBAM_ELMO changed the title to [REPORTED] VREST VL/VTO F+W Error
  • 5 months later...
  • myHelljumper changed the title to [RESOLVED] VREST VL/VTO F+W Error
Il 22/6/2021 at 14:18, myHelljumper ha scritto:

Hi, I'll move this into the resolved section, if you find that the bug is still there, post it here and I'll reopen the report.

I did some tests and i think the way F+W is calculated is not correct, please read the following and tell me what do you think about this.

 

From NFM-000 (2-77)

Cita

The maximum F+W is calculated as follows: first the hover weight is calculated. This is done by calculating the maximum rpm limited by ambient temperature, then calculating the maximum rpm limited by jet pipe temperature limiter settings. Since either of these parameters may limit the maximum rpm, the smaller of the two is used in the equations to calculate the hover weight. The hover weight is then adjusted for either the takeoff or landing calculations. For a vertical takeoff 97 percent of the hover weight is used. For a vertical landing approximately 95 percent of the hover weight is used. The adjusted hover weight is used along with the aircraft gross weight, fuel weight, and water weight to calculate the maximum fuel plus water weight at which a vertical operation can be executed.

 

As far as i can understand, the mission computer should consider current GWT to calculate the F+W.

Right now, it would seem that the mission computer is limited to determining the hover weight and then subtracting the BAW (basic aircraft weight) from it to get F+W.

 

Instead I think it should do someting like this:

 

1) Determine hover Weight , i've decided it is 18500lbs in our case

 

2) Break Down GWT 

 

BAW = 14804 lbs

Stores = 1000 lsb

Fuel = 3000 lbs

Water = 500 lbs

GWT = 19304 lbs 

 

The MC should break down the GWT as shown above, excluding from the calculation the current fuel and water  but considering stores and BAW. The difference between Hover weight and GWT without current fuel and water should be the calculated F+W.

 

3) Calculate F+W

 

HoverWeight - (GWT - CurrentF+W) = CalculatedF+W

 

so, considering 18500 lbs of calculated hover weight:

 

18500 - (19304 - 3000 - 500) = 2696

 

 

Of course I'm not sure about all this stuff, just asking for your opinion.

 

Thanks

--

[sIGPIC][/sIGPIC]

36° Stormo Virtuale - Italian Virtual Flight Community

www.36stormovirtuale.net

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Those calculations look right.

 

To add on to this there should also be separate calculations for take off and landing. At the moment one calculation is done for both, and both VTO and VL are boxed at the same time on the VREST page (should only be one boxed at a time).

 

The individual calculations would then be:

 

VTO page:    Max F+W = (0.97 * Max Hover Weight) - (Gross Weight - Fuel - Water)

VL page:       Max F+W = (0.95 * Max Hover Weight) - (Gross Weight - Fuel - Water)

 

@myHelljumper

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  • myHelljumper changed the title to [INVESTIGATING] VREST VL/VTO F+W Error
  • 4 weeks later...
  • myHelljumper changed the title to [RESOLVED] VREST VL/VTO F+W Error
  • 3 months later...
8 hours ago, Kappa said:

@AlphaJuliet @Hornet81

Resuming this topic since i've noticed that in VREST - BNGO Page, Drag Index is not updated.

In CRUS page DI is updated correctly when stores are loaded, in BNGO DI is not.

I think that’s correct as is. The bingo calculations assume that the aircraft is clean (NFM 2.20.1.4 is the ref) whereas the cruise page accounts for stores.

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