This latest report confirms the F-35 is not as maneuverable as legacy fighters. All three variants “display objectionable or unacceptable flying qualities at transonic speeds, where aerodynamic forces on the aircraft are rapidly changing.” One such problem is known as wing drop, where the jet’s wingtip suddenly dips during a tight turn, something that can cause the aircraft to spin and potentially crash.
Transonic speeds, just below the sound barrier, are the most critical spot of the flight envelope for a fighter plane. These are the speeds where, historically, the majority of aerial combat takes place. And it is at these speeds where the F-35 needs to be the most nimble to be an effective fighter.
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The program has attempted to fix the maneuverability performance problems by making changes to the F-35’s flight software rather than by redesigning the actual flight surfaces that are the cause of the problems. The software, called control laws, translates the pilot’s stick commands into behavior by the aircraft. One would expect that certain force by the pilot on the stick would result in an equivalent response by the plane. Because of the software changes, that’s sometimes not the case. For example, if a pilot makes a sharp stick move to turn the plane, the control law software now results in a gentler turn to prevent problems such as (and including) dig-in. F-35 apologists try to dismiss such issues by claiming that the F-35 was never intended for close-in aerial dogfighting, a claim belied by the Air Force’s insistence that the jet be equipped with a short range air-to-air gun.
As an air-to-air fighter, the F-35’s combat capability is extremely limited because at the moment the software version only enables it to employ two missiles, and they have to be the radar-guided advanced medium-range air-to-air missiles (AMRAAMs); in the future it will carry no more than four if it wants to retain its stealth characteristic. The F-35’s capability as an air-to-air fighter is currently further limited because the AMRAAM is not optimized for close, visual-range combat. (Eventually, upgraded software versions will allow the plane to carry missiles other than AMRAAMs, but not any time soon.) This means that any fight the F-35 gets into had better be short, because it will very quickly run out of ammunition.
Its gun would be available in close-in fighting as well, but it’s not currently working because the software needed to effectively use it in combat hasn’t been completed. The cannon in the F-35A sits behind a small door on the side of the aircraft that opens quickly an instant before the cannon is fired—a characteristic intended to keep the aircraft stealthy. Test flights have shown that this door catches the air flowing across the surface of the aircraft, pulling the F-35’s nose off the aimpoint resulting in errors “that exceed accuracy specifications.” Engineers are working on yet more changes to the F-35’s control laws to correct for the door-induced error. Making these changes and performing the subsequent “regression” re-testing to confirm the effectiveness of the changes have delayed the actual gun accuracy tests. Until these tests occur, no one can know whether the F-35A’s cannon can actually hit a target.
The F-35B and F-35C will both use an externally mounted gun pod rather than an internal version like the Air Force model. Because of differences in the shape of the fuselage of the two models, the Marine Corps and Navy will use different model gun pods. Both have been test-fired on the ground, but the flight tests to see what effect the pods have on the jet’s aerodynamics are only just now beginning. DOT&E has warned that, as happened with the gun door on the F-35A, unexpected flight control problems are likely to be discovered. The fixes to these will have to be devised and then tested as well. Only then will the program be able to begin the fuller in-flight accuracy testing, which is necessary to determine whether the gun pod is accurate.
Developmental testing delays, and the process of fixing the problems that testing will likely uncover, are severe enough that the program may not have an effective gun for Initial Operational Test & Evaluation. This could not only further delay scheduled testing but also, more importantly, prevent the aircraft from reaching the warfighter any time soon.
Ineffective as an Interdiction Bomber
There are several major reasons F-35s will have extremely limited interdiction usefulness—the Air Force’s and Marine Corps’ declaration of “initial operational capability” notwithstanding.
For instance, defense companies in Europe, Russia, China, and even Iran have been hard at work for years developing and producing systems to defeat stealth aircraft. And they have had some success. We saw this clearly in 1999, when a Serbian missile unit shot down an F-117 stealth fighter with an obsolete Soviet-era SA-3 surface-to-air missile (SAM), a system first fielded in 1961. Serbian air defense crews discovered they could detect the stealth aircraft by using their missile battery’s longwave search radar. Then, using spotters and the missiles’ own guidance radars, the Serbian forces were able to track, target, and kill one stealthy F-117. To show that was no fluke, the Serbian SAMs hit and damaged another F-117 so badly it never flew in the Kosovo Air War again.
Unaffected by the special shapes and coatings of modern stealth aircraft, these search radars easily detect today’s stealth airplanes, including the F-35. Since WWII the Russians have never stopped building such radars and are now selling modern, highly mobile, truck-mounted digital longwave radars on the open market for prices as low as $10 million. The Chinese and the Iranians have followed suit by developing similar radar systems.
An even simpler system that is even harder to counter than a long wavelength search radar is a passive detection system (PDS) that detects and tracks the radio frequency (RF) signals emitted by an aircraft—radar signals, UHF and VHF radio signals, identification-friend-or-foe (IFF) signals, data link signals like Link-16, and navigation transponder signals like TACAN.
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A good example of a modern PDS is the VERA-NG, a Czech system being sold internationally that uses three or more receiving antennas spaced well apart to detect and track and identify the RF signals emitted by fighters and bombers. The system’s central analysis module calculates the time difference of the signals reaching the receivers to identify, locate, and track up to 200 aircraft transmitting radar signals. The VERA-NG is only one of many types of PDS used throughout the world: the Russians, Chinese, and others produce PDSs, as well, and these have been widely fielded for several years.
The beauty of a PDS, from the perspective of an adversary employing one, is that radar stealth is irrelevant to it ability to detect and track aircraft. If the aircraft has to use its radar, radios, data links, or navigation systems to accomplish its mission, the PDS stands a good chance of being able to detect, track, and identify it by these emissions. Every aircraft in the world is susceptible to PDS, stealth and non-stealth alike, and the F-35 is no exception.
The F-35’s main air-to-air weapon, the AIM-120, is a beyond visual range radar missile; as a result, the F-35 has to use a large radar transmitting high-power signals in order to detect airborne targets and then guide the missile to them. Likewise, the aircraft has to employ high-powered ground mapping radar signals to find ground targets at long range. Moreover, if the plane’s systems have to communicate with other aircraft in the formation or with off-board supporting aircraft like AWACS, it has to use its radios and data links. The F-35 is thus likely susceptible to detection by passive tracking systems. Several of these passive detection systems are significantly less expensive than search radars—and they are virtually undetectable electronically.
The DOT&E report also lists several major reasons for the limited interdiction usefulness.
One such reason is that the F-35’s Block 2B (USMC) and Block 3i (USAF) software prevents it from detecting many threats and targets while severely limiting the kinds of weapons it can carry. For example, the F-35 can currently only carry a few models of large guided direct attack bombs. None of these can be launched from a distance like a power guided missile. Rather they fall on a ballistic trajectory from the aircraft to the target, which means they can only be released at relatively short ranges in view of the target. For now F-35 pilots “will be forced to fly much closer to engage ground targets and, depending on the threat level of enemy air defenses and acceptable mission risk, it may be limited to engaging ground targets that are defended by only short-range air defenses, or by none at all.”
The small number of weapon types the F-35 can carry also limits its flexibility in combat. The current software can only support one kind of bomb at a time, which DOT&E says is only useful when attacking one or two similar targets. So, for example, when a flight of F-35s departs loaded with bombs designed to destroy surface targets, they wouldn’t be able to also destroy any hardened or bunker targets because they wouldn’t have the heavier bombs required.