Grumman E-2X Hawkeye

By the 1990s the Grumman E-2 Hawkeye had already been about 30 years old. Also, at the time Grumman had spent considerable research resources into conformal antenna arrays such that the Navy requested that Grumman look into fitting a conformal array to the Hawkeye. Grumman began looking at ways to integrate the conformal array radar while maintaining most of the Hawkeye’s airframe commonality, landing gear and subsystems.

Grumman proposed the E-2X powered by the GE TF-34 turbofan (the same engine that powers the S-3 Viking and A-10). The conformal arrays would be fitted to the leading edges of the wing, fuselage sides, trailing edges and horizontal tail trailing edges. In order to house the array in the horizontal tail dihedral was removed and replaced by the same tail used in the C-2 Greyhound.

Removing the rotodome also had some effects to flying qualities when compared to the original E-2. longitudinal stability in the pitch axis necessitated a wing glove that also had additional fuel (which would make up for the fuel volume lost in the wings from antenna accommodation). The other major challenge in the E-2X was how to accommodate the TF-34 engines with changing the E-2C landing gear:

General Electric TF-34 Turbofan powers both the S-3 Viking and A-10 Warthog.
General Electric TF-34 Turbofan powers both the S-3 Viking and A-10 Warthog.

The solution was to “wrap” the TF-34 engine intake and exhaust ducts around the landing gear utilizing a split fan exhaust system…”

TF-34 cutaway drawing.
TF-34 cutaway drawing.

The resulting drag penalty would be overcome by using a slightly more powerful version of the TF-34.

Placement of the conformal array posed some unique problems. There were some problems with aircraft volume and weight distribution. The proposed number of transmitters posed weight and cooling problems resulting in additional complexity and therefore weight. Not to mention resulting changes to the flight control system based on the constraints of operating from an aircraft carrier.

Grumman's display model of the E-2X Hawkeye.
Grumman’s display model of the E-2X Hawkeye.

The E-2X was presented to the Navy and the E-2X program was shelved.

Source: The Aircraft Designers: A Grumman Historical Perspective.

5 thoughts on “Grumman E-2X Hawkeye”

  1. One strongly suspects that inside the Grumman shop, there was a team advocating for a clean sheet approach to conformal arrays- it would be easier to design.

    In the end, the E-2D, while obviously a compromise, in terms of radar data update rates, provides most of what the fleet needs in terms of surveillance and control. And at a good deal less cost than the notional E-2X would have entailed.

    1. One has to wonder, given the advances in efficency of processors, whether or not the cooling requirements would be less for a comparable conformal array present day. That said the cooling requirent certainly explains why we can’t gone with the arrays in subsequent AWACS aircraft.

    2. I would venture to say that the advances in efficiency of CPU’s doesn’t necessarily mean that they run cooler. For instance, the 386DX40 I had back in 1994 was of similar size to the i7-4770k that I have in my home office workstation today, but it would run just fine all day long crunching numbers without any sort of cooling. It didn’t even have a heat sink on it! By contrast, my i7-4770k has so many fans in it that it sounds like there’s a helicopter taking off in my office, and I still have to watch out for temperature excursions when I’m running long FEA or Moldflow simulation runs, or if I’m rendering something.

    3. Actually the advances in microprocessors and associated electronics involve the consumption of more power, not less. More miniaturization->more transistors per unit volume->more amps->more heat. Even in your regular desktop PCs, power supplies and cooling requirements have increased substantially over the years. If you work in a server room you need hearing protection due to the fan noise.

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