A feature common to most Tier 1 air combat/fighter aircraft is the ability to takeoff with full internal fuel and full payload.  Most have a margin in excess of this ‘total load’ figure which allows for growth in weight over the aircraft's service life.

Weight is one of the easier aspects of aircraft design to understand, unlike others which are often made intentionally confusing by the maker, his statements then being unfortunately taken on face value and repeated by the potential purchaser. Such design characteristics include the more emotional 'stealth', 'supercruise', 'network centric system of systems', and advanced radars such as 'AESA Radars', which makers describe in confusing technical jargon, implying capabilities to their aircraft which they do not have in the true sense.

What is called the aircraft's Empty Weight is one of the most basic and important aspects of aircraft design.  This is the weight akin to what is seen at a ‘Biggest Loser’ type weigh in; the ‘down to your skivvies’ weight, which for aircraft is without fuel or other payload such as bombs or missiles, sensor pods, external fuel tanks, or crew.  The Empty Weight is fundamental to how well the aircraft will aerodynamically perform, how much fuel and payload it will be able to carry, and how much growth it can accommodate throughout its life.

Weight, however, is such a predominant design objective/factor that it may alone determine whether or not an aircraft will proceed to the production stage. In these cases, the designer just cannot meet the operational requirements within the maximum weight constraint. Where the designer strikes serious weight problems, it behoves the potential purchaser to exercise more than usual caveat emptor, that is exercise greater due diligence when monitoring the program.

Not surprisingly, the JSF Program has had weight issues.  In 2003, the STOVL JSF was declared overweight and the SWAT (STOVL Weight Attack Team) was formed to perform a Biggest Loser miracle.  At the end of 2004, the SWAT declared they had removed ‘over 2,700 lbs’ off the STOVL aircraft's weight, with commensurate weight reductions for the other two models; the Carrier Variant (CV) and the one which Defence and the Government say we will buy, the Conventional Take Off and Land (CTOL) variant.  The news that the JSF had faced its Biggest Loser weight challenge and won was spread far and wide by the manufacturer's men and those of the prospective customers alike.  Now that all the hoopla, hype and weight reduction dust has settled, a look at the “weigh in”records of all three variants shows a somewhat different story -

Design Configuration Design Target Not-to-Exceed (NTE) Empty Weight (incl. 3% IOC Margin)	#240-1 (CY-2002) [lbs]	#240-2 (CY-2003) [lbs]	#240-4 (CY-2006) [lbs]	% change since 2002	Max Fuel Load (Internal) [lbs]	MTOW [lbs]	Weight Growth Factor	Inverse Payload Factor
CV JSF	30,049	30,700	32,072	6.7%	20,120	Classified	Negative	>0.75
STOVL JSF	29,735	30,500	32,161	8.2%	13,966	Classified	Negative	>0.75
CTOL JSF	26,500	27,100	29,036	9.6%	18,448	Classified	Negative	>0.75

These weight figures are from the JSF Program Office annual presentations to the US Air Force Association and are the design target weights for the three aircraft variants.  With an overall increase of 2,536 lbs (about 10%), the CTOL JSF is certainly not going to win the Biggest Loser competition.  In fact, all three aircraft designs have shown progressive and steady increases in their design target empty weights over the past 4 years.  Columns for the other two important weight parameters - maximum internal fuel load and maximum take off weight (MTOW) - are shown with MTOW, somewhat surprisingly, being declared to be ‘classified.   MTOW being held so close is a sure sign of an aircraft development program with weight problems.

Back in 2002, when the then senior Defence leadership convinced the Government that the JSF was the way to go, the MTOW was stated as 60,000 lbs. In the recently posted RAAF data sheet on the CTOL JSF, the MTOW is stated as in excess of 22,700 kgs (50,000 lbs).  Splitting the difference (55,000 lbs) makes for some interesting hypotheticals, which will become high risks for Australia if they turn out to be true.

Even at a MTOW of 60,000 lbs, none of the three JSF model designs present with an aircraft that is able to take off with full internal fuel and its full external payload, let alone internal and external payloads, together. The latter would not be possible even if the MTOW were 66,000 lbs.  Similarly, all three variants have a negative weight growth factor, that is, there is no margin in the design for increases in weight over the aircraft's life, whereas aircraft like the F-22A, F-15C/E and F-111, as well as the Russian Su-27/30 family of aircraft, have significant margins for growth.

The other parameter shown in the above table is referred to as the Inverse Payload Factor which is an engineering means of comparing different aircraft on the basis of their payload capability relative to fuel load and combined structural/systems weight.  A factor of 0.7 or less is common for aircraft that have distinguished themselves in service, principally due to efficient and effective design, with aircraft like the F-15E and F-22A scoring well at less than 0.65. In fact with the additional considerations of significant thrust available and a maximum zero fuel weight of around 48 klb, the design latitudes within the F-22 present an aircraft of awesome capabilities and growth, both for now and into the distant future.

APA has sought comment from both the JSF developer/manufacturer and the Department of Defence on the issue of JSF weight and the results of its analysis but, to date, has yet to receive any response.