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Grumman Northrop E-2 Hawkeye walkaround and scimitar propellers

1 October 2012

Grumman Northrop E-2 Hawkeye walkaround and scimitar propellers

The Hawkeye is a workhorse carrying a crew of five and some of the world’s most advanced avionics — it is also the one of the heaviest carrier borne aircraft in the U.S. Navy, and likely in the world as well. William Ridge (see credits, below) notes that catapults seem able to launch any weight but it is the landing weight which is critical. The main electronic asset in the Hawkeye is the Airborne Tactical Data System (ATDS) and ties to the Naval Tactical Data System at fleet HQ giving a step up to the concept of the Combat Information Center. Communications involve a broad spectrum or radio frequencies as well as satellite. The signature characteristic is the 24 foot diameter (~7.3m) rotodome (housing various antennae) which revolves at 3-6 rpm providing for 360º coverage. The four fin tail is necessary in order for the best radar performance.

Patrol duration is approximately four hours flying oval patterns which are about 50 miles (80km) long. The radar works best when at a 3º angle of incidence so the E-2 is trimmed with the aid of 10º of flaps during patrol.

E-2C Hawkeye at the Cradle of Aviation Museum, an early Charlie model as denoted by the conventional propellers — photo by Joseph May

Although I’ve seen a few Hawkeyes on the ground at airshows I only just recently saw one flying — and heard it! 

I had two immediate impressions. This E-2 Hawkeye was accelerating rapidly and only a few hundred feet above ground level while departing from Moffett Field when the pilot easily banked the aircraft by 25º or so. The speed and turn appeared effortless and nimble — performing more like a fighter as opposed to a cargo aircraft. The second impression was the noise signature since I had not heard one like it. Not the whine of a turboprop or the percussive beat of propellers — but a hum.

Yes, an energetic hum — not a buzz — of medium frequency.

Cool :)

Later I learned a nickname of the Hawkeye was Hummer.

The signature sound is due to modern propellers with progressively increasing sweep angles toward the tips. Propeller tips travel at much greater speeds than the rest of the blades. In fact, each portion of the blades travel at a faster rate then the part nearer the hub and slower than the part further away from the hub. Propeller blades greatly lose efficiency as the tips near supersonic velocities.

Enter the scimitar propeller design with significantly swept multiple (much beyond four) blade design. It is easy to say the sweep, just like swept wings on a fast jet, enable the propeller to be more efficient at higher speeds but the danger is overlooking the technical advances making the design possible. Carbon fiber construction reduces weight (reducing spinning mass is more critical than trimming static mass) as well as adding structural properties where needed, and modern fabrication allows for a balanced propeller (balancing becomes more of a challenge with each additional blade).

Naturally the most obvious feature of the Hawkeye is its signature rotodome (which contains a radar array) that enables the E-2 to accomplish its mission as an airborne early warning (AEW) aircraft. The E-2 is the only carrier based aircraft equipped with a pedestal mounted radome in the world and enables the aircraft to survey a great amount of airspace, sea surface and land cover — AEW is not about early warning any longer, it is about situational awareness with command and control of military assets. The aircraft has a typical mission of flying on station about 200 miles (320km) from ship for up to four hours — with the capability of tracking several hundred targets and directing 40 intercepts simultaneously. This AEW aircraft/aircraft carrier synergy helped to finally retire the seaplane/seaplane tender pairing.

Each Hawkeye has a crew of five — two pilots and three equipment operators (who face to port). Entry and exit is from a single portside main entry hatch, which is also way out of the aircraft by manually deployed parachute in the air. Three escape hatches, one aft of the radome pedestal and one above each pilot, are utilized for egress after ditchings. More will be written about the crew positions and life aboard the Hawkeye in Friday’s posting.

E-2C with the eight blade scimitar propeller at the 2008 Stuart FL Airshow. The large scoop behind the cockpit  provides the air supply for the heat exchanger to cool the electronics. The starboard scoop provides air for the Radar Liquid Coolant System (RLCS — and is mission critical) as well as a turbine used to air condition and pressurize the E-2 — photo by Joseph May

Grumman C-2 Greyhound (cargo  carrying version with a widened fuselage and cargo ramps but same wings and engines) with the conventional four blade prop at the 2008 Stuart FL Airshow with folded wings — photo by Joseph May

The Hawkeye’s 24 foot (7.3m) rotodome, the E-2 is the only carrier based aircraft equipped with a pedestal mounted rotodome — photo by Joseph May

The Hawkeye’s characteristic four finned tail — photo by Joseph May

My thanks to Steeljaw Scribe for supplying the technical information used in this post. His blog is one of the best written regarding the U.S. Navy and Naval Aviation.

My thanks, also, to William “Bill” Ridge (who commanded E-2B Hawkeyes from 1967 to 1982) for providing insightful information as well as verification for much of what is contained within this post.

Additional flight characteristics are documented in this publication E-2c Flight Characteristics from the Naval Heritage & History Command

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3 Comments leave one →
  1. Marty Davis permalink
    1 October 2012 16:19

    Excellent write-up! I enjoyed your explanation of the propeller design in particular.

    • travelforaircraft permalink*
      1 October 2012 17:20

      Thanks, especially about the props. I’d seen them but never looked to see what they were about before I started writing the post. Then, I learned about how they wouldn’t be possible without space-age like manufacturing methods. Cool :)

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  1. Hawkeye Week! « Steeljaw Scribe

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