3 Drop Tanks Range

A while back I read a comment in a thread saying that you have to be careful using 3 drop tanks in the hornet cause you could actually end up with LESS range than using 2 drop tanks if not configured correctly. My understanding is you had to triage the tanks by draining them separately.

Is there a way to do this in the hornet if this is true?

Why sould it matter from which tank you drain fuel? Neither total weight nor air resistance is affected by the choice of a specific fuel tank.

Why sould it matter from which tank you drain fuel? Neither total weight nor air resistance is affected by the choice of a specific fuel tank.

The idea the OP was referring to is this:

You have 3 droptanks and they are filled up. It would be wise to first consume the fuel from one tank exclusively (center tank) and drop that as soon as it is empty. That way you get rid of the drag as soon as possible.

However, I believe many folks are under the impression that dropping/jettisoning an empty drop tank is part of normal procedures while I think it is not. Since drop tanks like everything else, especially on a boat are limited in supply, you normally don‘t punch them off once empty. I believe you really only do that in an emergency or when you are desperate enough in a dogfight where that extra drag might make give the other guy the edge.

Yep, drop tanks stay ON the plane ;)

It was also a question in the fighter pilot Podcast but please do not ask me which episode exactly ^^

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However, I believe many folks are under the impression that dropping/jettisoning an empty drop tank is part of normal procedures while I think it is not. Since drop tanks like everything else, especially on a boat are limited in supply, you normally don‘t punch them off once empty. I believe you really only do that in an emergency or when you are desperate enough in a dogfight where that extra drag might make give the other guy the edge.

I also think it is not usual to drop them IRL unless you really need to. Thats why I was asking

cheers

To answer the original question: A1-F18AC-NFM-000, 2.2.4 External Transfer. You can choose your external tank feed order. There are switches to enable (or not) the wing and C/L tanks separately.

"Be careful" means you can't cruise too fast and carry too many other stores. External fuel tanks hold fuel but provide drag. The extra fuel required to overcome the drag of a third tank may exceed the fuel contained in that third tank in some circumstances but not in general. If you want to fly across the Atlantic like an airliner triple tanks absolutely has better range than two. Entire mission below 500' at 550 knots? Maybe the drag penalty eats up most or all of that extra fuel. You could find the exact crossover point at various speeds and altitudes where the drag is more than the fuel is worth.

Deliberate planned tank jettison is a theoretical capability to increase range but it's not done in practice. An F/A-18CD will takeoff and land with three tanks unless something doesn't go to plan like a bandit gets inside 10nm or whatever.

Now maybe some CF-188 patrolling over the homeland takes off with 3 tanks and chooses to empty the wing tanks first on the off chance that something happens (interception, mechanical fault) and he's happy to shed two of them empty and still get home on a full centerline and that drag reduction makes the difference. Any fuel tank jettison is an exciting day and one which may have been a very bad one.

Maybe the CG - centre of gravity plays its role here. Like airliners use to say:

As a wise man's rule, aft CG saves fuel.

Don't know anything about the Mass & Balance of the Hornet but having the CG more in the back reduces the pressure to equal the lift of the elevators - less fuel consumption. For most planes.

Surely this is more for airliners but aerodynamics work here as there the same way.

Hornet automatically distributes internal fuel to control cg. Hope that helps.

Hey guys how about we directly answer the question, disable your feed from the ext wing tanks, wait for the center-line to empty, jettison it and then enable the wing tanks again.

These checklist elitists might bicker about it not being procedure, because drop tanks cost money. But you know what the nice thing about the playing a flight simulator video game is, you don't have to pay the bill to replace a virtual fuel tank... Why people let the way they want to play the game get in the way of answering a technical question, I do not know.

I haven't managed to find a drag index for the hornet, but someone dredged up one for the 3 bag F15 debate, and the centerline tank on the 15 had slightly less drag than the 2 wing tanks... combined...

So you will definitely see a performance increase by getting rid of the centerline first, over doing it the other way around as it will likely nearly halve the added drag from the bags overall. Without even accounting for the fact it will take less time to empty it.

Why people let the way they want to play the game get in the way of answering a technical question, I do not know. .

Because many of us are driven to demonstrate how much we think we know-to the exclusion of all other considerations :)

Because many of us are driven to demonstrate how much we think we know-to the exclusion of all other considerations :)

#chairforcepilots

:megalol:

#chairforcepilots

Hey guys how about we directly answer the question, disable your feed from the ext wing tanks, wait for the center-line to empty, jettison it and then enable the wing tanks again.

 

These checklist elitists might bicker about it not being procedure, because drop tanks cost money. But you know what the nice thing about the playing a flight simulator video game is, you don't have to pay the bill to replace a virtual fuel tank... Why people let the way they want to play the game get in the way of answering a technical question, I do not know.

 

I haven't managed to find a drag index for the hornet, but someone dredged up one for the 3 bag F15 debate, and the centerline tank on the 15 had slightly less drag than the 2 wing tanks... combined...

 

So you will definitely see a performance increase by getting rid of the centerline first, over doing it the other way around as it will likely nearly halve the added drag from the bags overall. Without even accounting for the fact it will take less time to empty it.

Interesting.

Given that information, if applicable to the hornet, best to use wing tanks period.

Sounds to me like the benefit of the extra centerline gas is countered by the extra fuel used to have to carry the center bag.

Then on top of that, if you choose NOT to jettison....you'll use an awful lot of needless fuel dragging along all that dead weight.

Interesting.

 

Given that information, if applicable to the hornet, best to use wing tanks period.

 

Sounds to me like the benefit of the extra centerline gas is countered by the extra fuel used to have to carry the center bag.

 

Then on top of that, if you choose NOT to jettison....you'll use an awful lot of needless fuel dragging along all that dead weight.

Not true at all. The range and loiter time with the addition of a cetner-line bag definitely increases, but the performance hit is greater than that of individual wing bags, given that they hold the same amount of fuel. Ferry ranges all increase with 3 bags compared to 2 under wings only... otherwise, they'd never carry 3 bags.

From my not so scientific research and experience in the DCS Hornet the centerline tank is not behaving like it may on the F-15. I'll try and do some more unoffocial testing tomorrow night.

On this i wonder if a drag index could be added when choosing loadouts?

Interesting.

 

Given that information, if applicable to the hornet, best to use wing tanks period.

 

Sounds to me like the benefit of the extra centerline gas is countered by the extra fuel used to have to carry the center bag.

 

Then on top of that, if you choose NOT to jettison....you'll use an awful lot of needless fuel dragging along all that dead weight.

Upon further investigation, I believe the above information is not applicable to the hornet specifically.

My search did not show any difference between wing & center tanks on the Hornet C model.

You do use a lot of needless fuel dragging around dead weight.

Here is what else I was able to find out about the external bags:

The external tanks are referred to as "drop tanks" (jugs) for just that reason.

But they are never dropped unless max speed is needed or a combat situation requires it.

The drop tank adds to "air superiority" (range & loiter time) but also at times may "hinder maneuverability". They increase the moment of inertia, thus reducing roll rates.

Drop tanks limit your G force turning to about 5Gs. Anything beyond that and you can damage the hard points & air frame.

SOP is to draw fuel from external tanks first.

I am told the center-line tank burns fuel quickly, and it has a minimal impact on performance in the hornet. So apparently not the same as the F-15.

Primary disadvantage is that drop tanks impose a drag penalty on the aircraft.

Some of the fuel in the drop tank is used to overcome the added drag & weight of the tank itself.

Drop tank drag varies as the square of the aircraft's speed.

Drop tanks also increase the aircraft's radar signature.

I was amazed that I could not find a drag chart/graph that showed this as it related to the Hornet's external drop tanks.

Haven't looked at Hornet Limitations closely, but generally speaking, every aircraft I flew had a prohibition against cat shots or traps with partially filled drop tanks, or field or carrier landings or touch and goes with full or partial tanks.

If the tank wasn't in the proper config in blue water ops, then you'd jettison it.

At the field, you'd do a flared, minimum sink rate landing. The fuel slosh even with internal baffles overstressed the tank and hard points. This explains why you use the drops first so you can land in due course.

The idea the OP was referring to is this:

You have 3 droptanks and they are filled up. It would be wise to first consume the fuel from one tank exclusively (center tank) and drop that as soon as it is empty. That way you get rid of the drag as soon as possible.

 

However, I believe many folks are under the impression that dropping/jettisoning an empty drop tank is part of normal procedures while I think it is not. Since drop tanks like everything else, especially on a boat are limited in supply, you normally don‘t punch them off once empty. I believe you really only do that in an emergency or when you are desperate enough in a dogfight where that extra drag might make give the other guy the edge.

That's true, and other other certain circumstances can cause a fuel tank in one spot of the aircraft to be worse than if it's placed at a different spot even with the same aerodynamic shape. This is why you will never see a 3 bag F-15E, the center tank combined with the nav and targeting pods gives so much interference drag, it actually gives nearly 0 benefit to range. It would help if you fed fuel only from the center tank until it was empty and then drop it but like you mentioned, dropping tanks isn't a common occurrence IRL.

I have seen this idea some times now, though with other planes. There is onekind of logic there, as we see in RARE cases of rocket staging, where outer tanks are used first and then weight/drag is dropped of as it goes on. Theoretically it makes sense if one wants to keep certain speed x, and max the range->but (in this exmpl) you can / will throttle off and keep the same speed. IRL dunno how much this is used, in airplanes itself. What I do know that it is true that tanks are not dropped, if not mission designed so, or close contact / emergency. Other point is to drain fuels first from certain points of plane (or dropping tanks..) , is making wings etc to get your point of gravity go where you want. In hornet i could assume, that a pilot would like it more center, while f-18 (C atleast) wings are kinda light / thin (one could assume, that normally the point of gravity is kinda in center, at least in empy hornet). F-22 actually can "slosh/move" fuel around, like ballast, (ofc other planes also, but f-22 is very good example) so fcs can keep point of gravity, where it wants it (in f-22 MIT lecture, f-22 testpilot tells more about this, check youtube "MIT f-22 pilot flight school") It is one way for fcs to keep balance, for example after firing a weapon, and that way it (f-22 computer in this case) can also "trim" the plane. And ofc thats very usefull, you know how it is to FLY hornet after dropping 2000 pounds from one wing, it gets kinda wobbly, though one trims the plane go straight. And this is just the thing where that grav.point adjust of f-22 fcs helps. These were just couple examples that came to my mind while reading this thread.