Fuel tank performance hit?

[Lucican]

I know that adding additional fuel tanks on an F-15 will limit the acceleration of your aircraft since your plane has to push more fuel tanks, but I'm wondering if they really affect the aircraft's performance aerodynamics wise. Is it just plain better to eject all fuel tanks when starting a dogfight?

 

If newb question, sorry, I'm not very experienced.

[Robin_Hood]

Oh, yes, it will really affect aerodynamics, if only because it will lower your thrust-to-weight ratio quite a bit (esp. if they are full), and increase your drag, which will decrease significantly your turn and acceleration performance.

 

As for dropping them , I would say yes, if you intend to engage in a prolonged close-in dogfight. If staying BVR, I think you can delay dropping them and see if you can win the fight with them (BVR combat is less demanding performance-Wise, especially if you do everything right, ie. not getting shot at).

 

I'm not used to flying with drop tanks, though (Su-33 is my main aircraft), so others might have more educated opinions.

[104th_Maverick]

Yes as Robin says you should always drop those tanks if you find yourself in a BFM situation.

Especially if you have 3 tanks on board, trying to fight with any fighter carrying 3 tanks is a fast way to die!

 

You also want to consider doing this if your denfensive and being chased by a bandit, carrying the fuel tanks will not only slow your acceleration down but it will also limit your top speed.... so when the sh!t hits the fan, drop your tanks and GTFO of there ;)

[TAW_Blaze]

Once you drop the tanks you're flying a different plane :)

 

Can be handy in BVR to surprise your enemy with the insane energy gain and top speed, but most often you'll drop them to either run or start a brawl.

[GGTharos]

BVR is quite demanding performance-wise, just in a very different way. A better performing aircraft can shorten the opponent's e-pole, thus 'squeaking in' with a marginal but deadly advantage.

 

If staying BVR, I think you can delay dropping them and see if you can win the fight with them (BVR combat is less demanding performance-Wise, especially if you do everything right, ie. not getting shot at).

[Exorcet]

If staying BVR, I think you can delay dropping them and see if you can win the fight with them (BVR combat is less demanding performance-Wise, especially if you do everything right, ie. not getting shot at).

Dropping tanks for BVR certainly helps. BVR is pretty energy intensive if your target knows how to fight. You want to give your missiles a better chance of hitting than yours. More energy means your missiles have a better Pk and you shrink the other guy's engagement envelope.

 

However, keeping the tanks gives you a lot of fuel to play with. I feel comfortable in the F-15 with two tanks or less. 3 tanks though, especially if they're nearly full, feels like flying a bomber.

[GGTharos]

3 tanks are so draggy it's not funny. They're also not exactly good for maneuverability (And if the AFM does deal with them, then 3 tanks should make the plane more unstable - that's what I mean by not good for maneuverability ... they increase your probability of departure). They're fine I suppose if you're doing a north pole/Icelandic bomber intercept or ferrying.

[Cali]

That is one reason why the external tanks feed first, so if something does happen they are empty and you have more internal fuel.

[TAW_Blaze]

Indeed. Although I'd love if they didn't drag fuel simultaniously from all 3 tanks but rather in a sequence (ie wing tanks first) so you could drop the wingtanks and keep the centerline up. But I guess it works this way for a good reason.

[Cali]

In FC2 after the F-15 fed down to ??? lbs, you could drop the centerline tank and the wing tanks would still be full. Haven't played FC3 enough to find out if it works the same way.

[FLANKERATOR]

Sometimes dropping all your payload (missiles included) and dumping fuel will be necessary to survive, every pound counts when it comes to maneuvering and acceleration.

[BitMaster]

Hey,

 

the main reason why you HAVE to drop external fuel tanks in RL is that they are NOT self sealing and any bullet or shrapnel would let the tank explode and your AC with it ! Just saw a dogfight video ( one of a few dozen I watched ) and the pilots explained the non self sealing issue as critical.

 

Also, they are VERY heavy when full and the hooks would not be able to carry them through a 9G turn, they would damage the pylons and AC.

 

Empty externals first, drop them as soon as you know ANY combat is imminent, even BVR. Your radar cross section is significntly higher with external drop tanks, I think this also applies for the sim and not only RL.

 

Bit

[Exorcet]

FC3 has constant RCS and no issues with frame stress.

 

When the AFM patch comes to FC3, the F-15 will probably have finite stress limits, but RCS probably won't change with or without tanks.

[GGTharos]

People tend to underestimate how much g the eagle can apply even with tanks on-board. Not to mention that in combat, they're not likely to be full.

[Robin_Hood]

Hey,

 

the main reason why you HAVE to drop external fuel tanks in RL is that they are NOT self sealing and any bullet or shrapnel would let the tank explode and your AC with it ! Just saw a dogfight video ( one of a few dozen I watched ) and the pilots explained the non self sealing issue as critical.

 

Also, they are VERY heavy when full and the hooks would not be able to carry them through a 9G turn, they would damage the pylons and AC.

 

Empty externals first, drop them as soon as you know ANY combat is imminent, even BVR. Your radar cross section is significantly higher with external drop tanks, I think this also applies for the sim and not only RL.

 

Bit

 

Not sure you're talking about the F-15C specifically, but...

 

In Vietnam, the F-105s (I believe) tried hard to bring back their droptanks back to the homeplate, and did not drop them unless they absolutely had to. And I'm talking about keeping drop tanks during a bombing pass over Hanoi in a high AAA and SAM environment.

 

So as far as dropping your tanks at the first sign of combat, your mileage may vary (or maybe doctrine has heavily changed since then - quite possible). Of course, drop tank design, attachment, and a whole lot of other factors must be taken in account, and for sure an F-15C is not a F-105.

[pepin1234]

If you talk about the F-15 of FC3. You can do whatever you want with 3 fuel tanks. I have seen them climbing till 13000m really fast. Shooting down everybody ( they just Need Launch the Aim-120 at 25 km range, the R-27ER have a new Speed of match 3 in the encyclopedia :-). they can turn with 3 fuel tanks like a real Mig-29.

Edited January 20, 2014 by pepin1234

[GGTharos]

No, they can't. But I'm sure you'd know that if you actually compared the EM diagrams :)

 

Unless the tanks are empty, in which case there's a huge amount of drag, but not weight. Flying at 13000m is not a problem for an F-15C unless it's also hauling CFTs.

[pepin1234]

But I'm sure you'd know that if you actually compared the EM diagrams :).

 

not sure what you mean

 

Unless the tanks are empty, in which case there's a huge amount of drag, but not weight. Flying at 13000m is not a problem for an F-15C unless it's also hauling CFTs.

 

Why empty? I am talking about guys that just take off and go into combat without Problem. Turn, climbing and runaway at 1400 km/h dont seem a Problem for our F-15 with 3 fuel tank.

[lunaticfringe]

not sure what you mean

 

Wicked shocker, that.

 

Go here: http://www.avialogs.com/

 

Select "Library". Select "Aircraft". USA. McDonnell Douglas. F-15. TO 1F-15A1 Flight Manual.

 

Two thirds of the way through, you'll find lots of pretty charts and diagrams, along with instructions on how to read them. Give it a shot.

[GGTharos]

The F-15C has no problem doing 1400kph with 3 tanks. They regularly practice running around at M1.6 with 2 tanks. I don't know what your objection is. The F-15C is very well tuned to its real performance in this respect.

 

Why empty? I am talking about guys that just take off and go into combat without Problem. Turn, climbing and runaway at 1400 km/h dont seem a Problem for our F-15 with 3 fuel tank.

[pepin1234]

The F-15C has no problem doing 1400kph with 3 tanks. They regularly practice running around at M1.6 with 2 tanks. I don't know what your objection is. The F-15C is very well tuned to its real performance in this respect.

 

Thats not possible man. All the running are at sea Level and they can get this speed with 3 full tanks and 80 % internal fuel at 1400 Km/h at sea Level. Thats only happen with the super F-15 of FC3, BUT the acceleration is suddenly, must see.

Edited January 20, 2014 by pepin1234

[GGTharos]

I don't have a chart for 3 tanks at sea level. I don't know if 1400kph is possible, but it is not out of the realm of possibility - it's M1.14. The biggest problem with the tanks is not weight, it's drag. Drag reduces top speed, weight reduces acceleration.

 

Thats not possible man. All the running are at sea Level and they can get this speed with 3 full tanks and 80 % internal fuel at 1400 Km/h at sea Level. Thats only happen with the super F-15 of FC3, BUT the acceleration is suddenly, must see.

[TAW_Blaze]

In FC3 the externals are drained simultaniously, was experimenting to drop the wing tanks with weapon jettison (that way the centerline tank is still there, unlike using fuel tank jettison). For instance if you drop the wing tanks at 15000 lbs it generally goes down to 14000.

 

I don't know how this works on the real Eagle, but it makes no sense to me. The only sensible explanation would be to keep the center mass under control but even then draining the 2 wing tanks only would nearly do the same while leaving you with much more freedom to manage. That way you could drop the wing tanks around 16-17k lbs to get rid of your "airbrakes".

 

@GG, can you inform us how it goes on the real one?

[GGTharos]

I don't recall, but no one takes 3 tanks to combat anyway.

[TAW_Blaze]

Indeed. I'm dirty for using way too much burner :D