Royal Australian Air Force [RAAF] News, Discussions and Updates

south

Well-Known Member
You are misreading the SAR link. Its says 410 is the Threshold (the min contractual requirement) whereas Demonstrated Performance the column over is 462 nmi. It also exceeded the objective of 425 nmi. In fact, the Super Hornet is one of the few US fighter programmes in recent history to actually EXCEED its objective requirements in numerous areas. Look at the SAR for F-35 - for most areas, it ultimately achieved the threshold numbers but not the objective numbers. You can say the bar was too low for the SH, but Boeing actually did better than what was contractually required!

Which reminds me - let me also give you some insight into how US DOD Acquisitions programmes are run:

The Selected Acquisition Report lists Key Performance Parameters - KPPs - that exist in the Capability Development Document (CDD) which is created at the start of any programme before they enter EMD.

Those KPPs are contractual requirements that the contractor must meet the THRESHOLD requirements, with OBJECTIVE being what is targeted. Not meeting the threshold can hold severe punishments for the contractor - to include breach of contract and termination of the programme entirely.

Each requirement has a specific profile to be flown. The Fighter Escort profile you are mentioning, which is in the Standard Aircraft Characteristics, includes 2 minutes at maximum thrust at Mach 1 at 10,000 feet and a climb back out all of which reduce range. That is a lot of gas burn at 10,000 feet - maximum thrust is in full afterburner, which consumes 3x more gas than at military rated thrust. More below.



50nm each way is 100 nm which at 500 knots ground speed is 6 minutes of flight. At surface level, a jet consumes 3-5x more fuel per engine than in the 30,000s for the same airspeeds. That's the equivalent of going 18-30 more minutes 500 knots if just cruising in the 30,000 feet region (which is why airliners like to fly at those altitudes - they are the most efficient and thus best return on money for a business) - or 150-250 more nm if they simply stayed high instead of descending to do an interdiction then climb back out (which also consumes fuel).

Note that the Hi-Hi-Hi profile with just 2 x AIM-120 (Page 5) shows 574 nm with internal fuel only.



As mentioned, Page 5 shows 574 nm with internal fuel only for the Hi-Hi-Hi profile with 2 x AIM-120. So yes, it quite literally does.

Also, these are Standard Aircraft Characteristics - which is produced by NAVAIR - which are for aircrew to reference for coarse estimates of real world fuel. This is significantly more reliable, realistic, and relevant than programme documents for acquisitions that the SARs report - which contractors can and do optimize for specific requirements because they MUST meet the KPPs - and certainly more reliable than advertisements and slides by contractors selling a product.

Again, in real world operations, there are a lot more variables than single points of comparison in a Selected Acquisition Report. The Standard Aircraft Characteristics alone highlight how different a profile and loadout can affect range and other performance numbers. Real world usage of the Super Hornet - in terms of range - is far closer to the F-35A than commonly held - and can even exceed it in some areas, since the SH has EFTs whereas the F-35s do not.

Edit:

One other point to add: the Super Hornet numbers all assume operations on an aircraft carrier. Aircraft carrier operations involve extra reserve fuel and time holding because aircraft carriers are not airfields that can land aircraft at any time, since the flight deck is not always ready to land aircraft. Those profiles include minimum fuel requirements that are higher for the Super Hornet than the F-35A.

Do you really think the F-35C - with over 1,500 more pounds of internal fuel AND disproportionately bigger lift (wings and horizontal tail) than the F-35A - only gets one more nautical mile of range? Of course not - because its profile flown in the KPP/SAR involves carrier-based operations to include larger fuel reserves.
This is all lovely data, but for starters it’s for the F/A-18E rather than the F. The F holds about 900lb less fuel due to space taken up by the second seat - or about 40-50NM combat radius.

Second, while the F-35C does indeed carry more internal fuel, it has more parasite and lift induced drag. This is because the bigger wing and reinforced structure have empty weights about 5000lb heavier than the F-35A - one only needs to look at the acceleration figures to understand the performance impact. The additional drag tends to offset the additional fuel.

What does this mean in practise, as employed by the RAAF? The F-35A has a larger combat radius, or more loiter time at the same range than the F/A-18F and especially the E/A-18G.

At the end of the day, for the operating environment, all of the platforms are AAR dependent - although the SH/Growlers are more so. I’d double the tanker fleet first.
 
This is all lovely data, but for starters it’s for the F/A-18E rather than the F. The F holds about 900lb less fuel due to space taken up by the second seat - or about 40-50NM combat radius.
Sure, but data is better than people making up whatever facts they want, and the numbers are significantly closer than people are imagining even with the F.

Second, while the F-35C does indeed carry more internal fuel, it has more parasite and lift induced drag. This is because the bigger wing and reinforced structure have empty weights about 5000lb heavier than the F-35A - one only needs to look at the acceleration figures to understand the performance impact. The additional drag tends to offset the additional fuel.
Having seen all the aircraft in this discussion in real operations at some point in a past life, if I may, I can give you some insight into how different real world flying is compared to numbers you see online:

1) The F-35C weighs 5,000 pounds more (16% more than the F-35A) but has 50% more wing area. It more than offsets the weight gain. The F-35C can actually outclimb the F-35A to high altitudes from sea level despite the A beating it in time to climb to lower altitudes - the F-35A is the one that struggles with additional weight and altitude and requires higher throttle settings at higher altitudes. The endurance and range in real world usage is notably different especially where the planes can be flown to be most efficient (high 30s to low 40s is most efficient for range, which is again where airlines like to fly, and the C does a better job there than the A)

2) Look up a drag curve. Induced drag dominates at low airspeeds, parasitic drag dominates at high airspeeds. The bigger wing's induced drag is not the factor at high airspeeds - and the effect of bigger and thicker wings only really show up at the transonic region. Moreover, you forget that the two jets do not fly at the same angles of attack due to this - the A model, with the disproportionately smaller wings for its weight than the C, actually flies at higher angles of attack for the same airspeeds and thus has more induced drag at most of the airspeeds the jets spend the majority of their time in (and fun fact: on approach, despite approaching 20-30 knots slower, the C flies a lower angle of attack than the A). The B, being nearly as heavy as the C, but with the wings of the A, struggles even more - hence why the B is frequently derided by military aviators for its very poor real world range and endurance and not what gets bandied around from acquisition documents and marketing.

3) Speaking of which, since the C has bigger wings, it actually holds turns better than the A despite the worse thrust/weight ratio. This is not just in a turning engagement, but when you are doing real world flying, you aren't just holding straight and level indefinitely. You are probably doing turns over some area to stay within an operating area, border, or other airspace control schema - and the C doesn't need to come up on the throttle as much as the A to maintain turns at optimal endurance altitudes (which are again in the 30s) because its wings generate more lift and can hold a turn better without needing throttle. This all results in notably better endurance in real usage.

4) Acceleration figures being quoted for acceleration in the transonic region, which is largely avoided because of how inefficient it is. They have essentially identical max range and max endurance speeds - and people rarely spend much time in the transonic region. I have to ask: do people here really think these max range and endurance numbers are achieved by flying inefficiently? Any time range/endurance are a factor, pilots fly efficient until they need to go tactical - and tactical acceleration doesn't happen often in real life for a number of reason because even in a fight, you still have to manage your fuel or you won't be sticking around long to actually fight.

And I think everyone would be surprised how irrelevant a 0.9-1.2 Mach acceleration number being quoted is. Both the A and C flight manuals state that the quickest and most efficient way to accelerate through the transonic region is to trade altitude for airspeed while in MAX. Guess who - because it can consistently fly higher more efficiently - actually does this more efficiently? A plane that can consistently hang out in the low 40s versus 30s is going to accelerate more efficiently than the one starting lower and trying to do it level (and it's harder once you get into the 20s in part because you run into q limits and also the increased drag from the thicker atmosphere, so you don't want to descend too low).

Again, real world operational usage is very different from single acquisition numbers being marketed and extrapolated to the entire flight regime, which is a significantly more complex and multi-variable

What does this mean in practise, as employed by the RAAF? The F-35A has a larger combat radius, or more loiter time at the same range than the F/A-18F and especially the E/A-18G.
Surprisingly not necessarily true, especially since range and endurance are not the same thing. Even if we ignore the discussion earlier about the effects of the small wings on the A for its weight, which create a surprising amount of induced drag since the jet tends to cruise at a higher angle of attack than a lot of other airframes and means its struggles with payloads at altitude where even the F/A-18F and EA-18G - oft derided for drag - can do fine with, the F/A-18F and EA-18G - being Navy aircraft - if nothing else, were built with an implicit requirement for endurance (to make no mention of the difference in TSFC between the F414 and F135s). Even with real external payloads, they actually burn similar or less fuel (pounds per minute) at max endurance than a clean and empty F-35A. The biggest reason for the difference for range is that the A cruises at max range airspeeds at 20-50 KCAS faster than the F/A-18 (depending on altitude) - which means it get somewhere quicker for the same time aloft - but actual overall endurance tends to be worse for the same amounts of fuel, and the F and G tend to carry one or two EFTs which brings them to similar or higher endurance than the A.

You can ask some B fliers - who despite having similar internal fuel as an F or G - how often they can get a a 2.0 hour sortie even if they tried flying max endurance throughout in a clean and empty B - whereas an F or G, even with internal fuel only and all the external pylons, will never struggle to get to a 2.0 hour sortie at max endurance.
 
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