Apr 232011

Sometime in the late 1940’s / early 1950’s, North American Aviation produced these studies for an Airborne Combat Information Center (CIC) / Airborne Early Warning (AEW) aircraft for the U.S. Air Force. Documentation is lacking and we presently only have these general arrangement drawings to go by. These were scanned from microfilm and much of the fine print is illegible. These could be studies for a follow-on to the Lockheed EC-121, though this is pure speculation. It is not known whether these were drawn up for a specific competition or if they were part of a more general series of AEW studies produced for the Air Materiel Command (AMC). As the individual ESO 4705 configuration studies lack a sub-designation to distinguish them, we will refer to them by their blueprint number in the descriptions below.


This was a somewhat dumpy-looking twin boom design with 25 ft radar dish suspended beneath the truncated central fuselage. It was powered by two radial engines of an unspecified type, perhaps the Pratt & Whitney R-2800 that powered the aircraft shown on blueprint D160-3 below.


This blueprint is missing; it may have been an inboard profile of the previous study or a different configuration entirely.


The most unconventional of the three designs, this aircraft had an airfoil-shaped central fuselage of semi-discoidal planform designed to accommodate a 25 ft diameter radar dish, which was suspended underneath the aircraft in a huge cylindrical enclosure. Crew comprised a pilot, co-pilot, flight engineer, radio-navigator, and six Plan Position Indicator (PPI) operators. The latter sat in the leading edge of the airfoil-shaped portion of the fuselage and were provided with an unusual circular passage around the radar antenna to reach the toilets and bunks at the rear. The data in the blueprint’s information block appears to be 1948, but this is definitely uncertain.


The largest of the North American ESO 4705 studies, this huge aircraft had a span of 193.5 ft and a length of 106.2 ft.  Like the previous study, it also had an airfoil-shaped central fuselage (or a very thick center wing section, depending on your viewpoint), though the designer opted for simpler straight leading and trailing edges. The aircraft appears to be powered by two turboprops of an unknown type. An 18 ft diameter radar in a cylindrical enclosure was suspended underneath fuselage.  The artist’s impression in the right hand corner of the blueprint shows six windows on top of the center wing, which were likely for the PPI operators.

There may have been additional configuration studies done under ESO 4705, but these have not been located at the time of writing. In any case, none ever left the drawing board; the Air Force and Navy have generally opted to modify existing transport aircraft for the AEW role rather than build a dedicated platform from the ground up, as it is more economical. Thus, whatever reduction in drag or weight achieved by these designs over a more conventional solution was probably more than offset by the expenditure required to build them.

North American Aviation ESO 4705 CIC/AEW Characteristics

Blueprint No.D160-1D160-3D160-4
Length (ft)61.594.1*106.2*
Span (ft)122.5118.5193.5
Wing Area (sq ft)1,0002,000
Power Plant2 x unknown radial2 x P&W R-28002 x unknown turboprop
Propeller Diameter (ft)16*1617.5
NotesFuel Capacity: 2,600 gals

All images from NARA Archives II, College Park, MD, RG 341

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