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Ballast and Pylon Weights?


Frederf

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Ballast is used in the F-5E-3 depending on loading of certain stores to improve CG balance. The figure of 15,170 lbs. in the editor suggests that this ballast is included at all times, even when wing tanks are not used. For maximum performance when wing tanks are not used 97 lbs. of nose ballast may be remove which would result in a basic airplane weight of 15,073 lbs and the CG moving aft by as much as 1.4%. Is this modeled?

 

Also noted is that weight of airplane is not seeming to increase by weight of pylon when for example bombs are attached. With and without bombs the wing pylons are and are not present but the reported weight is only increasing by the weight of the bomb itself.

 

However the MER when carrying 5xMK82 seems to be included at 200 lbs.

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The figure of 15,170 lbs. in the editor suggests that this ballast is included at all times, even when wing tanks are not used. For maximum performance when wing tanks are not used 97 lbs. of nose ballast may be remove which would result in a basic airplane weight of 15,073 lbs and the CG moving aft by as much as 1.4%. Is this modeled?

 

For takeoff performance calculation purposes I have always assumed the DCS F5 has the ballast installed. Just as you say, the DCS F5 with full internal fuel is 15170 lbs, which matches exactly the aircraft average gross weight given on A1-8 of 1F-5E-1. Taking that F5 with full internal fuel and adding the 2 275gal pylon tanks yields a gross weight of 19178 lbs. That means DCS thinks the 2 drop tanks weigh 4008 lbs. This matches almost exactly with the values given on page A1-8A, 3549 usable pounds of JP4 plus 454 pounds of tank, for a total of 4003 lbs.

 

So if DCS modeled the ballast, either the empty weight should be 97 pounds less or 97 pounds should be added in addition to the ~4000 pounds of tank and fuel when the pylon DTs are installed. Since that isn't the case, I have always assumed the variable ballast is installed all the time.

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...The figure of 15,170 lbs. in the editor suggests that this ballast is included at all times, even when wing tanks are not used. ...nose ballast may be remove which would result in a basic airplane weight of 15,073 lbs and the CG moving aft by as much as 1.4%. ...

 

 

There is fixed nose ballast and variable nose ballast.

 

NOSE BALLAST [E][E-2] T.O. 1F-5E-594 J and [E-1][E-3]

In addition to the fixed nose ballast, additional variable nose ballast must be installed when inboard pylon fuel tanks are carried.

 

 

A1-8 weight 15,170 (W/BALLAST) includes the fixed nose ballast, so 15,170 is the gross weight. Variable nose ballast must be added to that when inboard pylon fuel tanks are carried...

 

We already know pylons are currently weightless, so it seems likely the additional variable nose ballast is also absent.

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NOSE BALLAST [E][E-2] T.O. 1F-5E-594 J and [E-1][E-3]

In addition to the fixed nose ballast, additional variable nose ballast must be installed when inboard pylon fuel tanks are carried.

 

Interesting, is that a quote from F5AAA-1? 1F-5E-1 isn’t that specific, I had missed the difference between the fixed ballast which seems to be there and the variable ballast, but your explanation certainly makes sense.

 

Do you have any insight on how the variable ballast functions dolfo? To me the name implies that it would move its weight as the fuel burned out of the pylon tanks to compensate for a shift in CG, but of course that is just speculation.

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That was from 1F-5E-1 page 5-12 change 6.

 

1978 Original - Page 5-10: In addition to the fixed ballast, approximately 80 pounds of variable ballast... nose section can accommodate aprox. 240 pounds of fixed, variable or future growth ballast. 1-1B-40 should be consulted for exact amount of ballast lead weight to be installed.

 

So variable as in how many plates you want in the nose.

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As I understand it: Variable ballast just means ballast that can be added or removed by ground crew before flight and carried throughout. Fixed ballast is permanently affixed to airframe and is not changed regardless of loading. There's no indication of ballast that may be removed or discarded during flight.

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