For Those Questioning F-35 All Aspect Stealth
Earlier, I found myself engaged in a most entertaining discussion. The gist of this conversation revolved around all aspect stealth on the F-35, or as the blogger claimed, lack of all aspect stealth. Uninformed people make the world spin on, right? As this blogger, as he has done to a whole host of other respondents, has banned me, I will give my little lesson here.
F-35 critics love to harp on and on about the woes of the Joint Strike Fighter Program. Recently, their main complaint of per airframe cost was dealt a serious blow. Critics being critics, they are forced to move on to other complaints, forecasting doom and gloom. A lack of rear aspect Radar Cross Section (RCS) reduction is not a new complaint from the ranks of JSF critics. Another intrepid blogger stated ‘From the rear, the F-35’s traditional round engine makes it as stealthy as most other single engine fighters, which is to say, not at all’. What few of them realize, is that this claim they love screaming to the heavens is not only incorrect, but misinformed.
As evidence of their claims to support a lack of rear aspect stealth, photos of other low observable aircraft are presented. These examples are used by critics to show what ‘rear aspect RCS reduction looks like’. Here are a few of those.
Use of this example by critics is amusing for a number of reasons. First, critics fail to take into account the fact that the F-117 was an aircraft limited by design compromises brought about by the technology of the time. Designers buried both engines deep in the fuselage, to mask highly radar reflective turbine blades behind special intake screens. To reduce infrared and radar exhaust signatures, several methods were used. For IR reduction, bleed air was mixed with exhaust gases, to cool exhaust temps. These slight exhaust ledges, along with intake issues and a lack of afterburner, limited the F-117 to subsonic speeds. Notice, the F-35 is not a subsonic limited aircraft.
The very bold critic will point to the B-2 Spirit as a prime example of rear aspect stealth. While that is true, this argument is one they base on assumption alone, for those who have never had any connection to the B-2. Photos of the B-2 from the rear are forbidden by the Air Force. While I acknowledge the B-2 as a good example of rear aspect stealth, it is not one that represents an honest apples to apples comparison for the F-35. I say this, because like the F-117, the B-2 is a subsonic limited platform. Like the F-117, the B-2’s engines are also deeply buried within the fuselage, and shielded by several intake and exhaust shrouds. If it isn’t an afterburner equipped mach capable platform, it isn’t an honest comparison.
Here we have the backend of the F-22 Raptor. This is the example from critics I love the most. Certain critics point to the thrust vectoring nozzles as their claim of rear aspect RCS reduction. Sadly, that is simply not entirely correct. Thrust vectoring nozzles on the F-22 do offer a bit of RCS reduction, due to shape. Their primary function is what? To vector thrust! Consult the above video as reference. If you click on and enlarge the F-22 rear aspect photo, you will light colored bars seated within the aircraft. These are rear radar blockers. These serve to block radar return from the F-119’s powering the F-22. That is a large portion of the Raptors rear aspect stealth. Critics using the F-22 example make the assumption that the F-35 exhaust, being dissimilar from that of the F-22, are not stealthy because they are different. Unfortunately, the critics are wrong once again. Have I mentioned how much I love simple people?
Now lets move on to the F-35. Here are a few photos. Direct your attention to the rear exhaust, and the exhaust/fuselage junction. Once again, you will want to enlarge the photos to take in the small details. The devil is in the details, as they say.
Notice the sawtooth features that ring the exhaust nozzle, and can also be seen at the nozzle/fuselage junction? That is an RCS reduction feature! Similar use of the sawtooth setup can also be seen on the F-117, at the canopy junction, and the landing gear doors. These sawtooth notches that ring the exhaust nozzle consolidate the exhaust into the ‘spike’. These systems, in conjunction with built in measures and coatings, not only reduces rear aspect RCS, but also minimize the F-35’s IR exhaust signature. Its a two for one deal. Somewhere out there, a critic is asking how did this come to be, and how much this costs. How this came to be, I will cover in a moment. As for cost, it is a sunk cost, invested nearly two decades ago, so nothing to get your panties in a bunch over.
In 1996, a Lockheed Martin/Pratt & Whitney team along with the Office of the Joint Strike Fighter Program, began a project called LOAN. This stands for Low Observable Asymmetric Nozzle. The purpose of LOAN was to develop technology to bring about significant RCS, IR, and greenhouse gas emissions reduction. Their mandate was to deliver this technology at an affordable cost. Flash forward nearly two decades, and we see that they succeeded wildly.
During testing, the F-100-200 engine taken from an F-16C was used. IR cameras monitored test runs at full afterburner, measuring nozzle and nacelle temperature. Using geometry, advanced cooling systems, and special coatings both inside and outside of the nozzle, significant temperature reductions were noted. Due to the effectiveness of these temperature management and reduction measures, a savings in maintenance costs over the lifetime of the nozzle was realized. It’s worth pointing out that the end product of LOAN can not only be used on the F-35, but also the F-16.
Now you see the technology critics either refuse to acknowledge, or are too ignorant to believe exists. Claims for a lack of rear aspect stealth for the F-35 are not only wildly inaccurate, but outright incorrect. F-35 is an all aspect stealth platform, and nothing critics spout will change that fact. In the future, I hope the critics peanut gallery at least makes claims that are difficult to disprove. That would keep things interesting. Until then, I content myself with pointing out the flawed thinking of certain wayward individuals.