Article 3550 of rec.aviation.military:
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From: jfb@usgp1.ih.att.com (Joe Baugher)
Subject: Bomber Series--Consolidated B-24 Liberator (6 of ??)
Message-ID: <Cxn3sK.uz@ssbunews.ih.att.com>
Summary:  XB-24B, turbosuperchargers
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Organization: AT&T
Date: Fri, 14 Oct 1994 01:50:44 GMT
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Disappointed at the XB-24 prototype's relatively slow maximum speed of 
273 mph instead of the 311 mph originally estimated, on July 26, 1940, 
the Army recommended that some changes be made to the aircraft to 
improve its performance, especially at high altitude.  

First and perhaps most important of these changes was the introduction 
of engine turbosuperchargers to give the aircraft a better 
high-altitude performance.  Accordingly, the XB-24 was re-engined with 
1200 hp Pratt & Whitney R-1830-41 (S4C4-G) radials which were equipped 
with General Electric B-2 turbosuperchargers which replaced the 
mechanical two-speed superchargers of the earlier engines.  The 
turbosuperchargers were mounted on the lower surface of each engine 
nacelle.  The oil coolers were relocated to the flanks of the front 
cowlings and the air intakes for the turbosuperchargers were placed on 
the sides of the engines, which gave the nacelles a characteristic 
elliptical cross-section, which remained with the Liberator all 
throughout its production career.  

The Army also directed that Consolidated eliminate the "wet" wing and 
install self-sealing fuel tanks in the wing.  The engine controls were 
modified so that they permitted at least 60 percent engine power even 
if the controls were shot away.  Electrical engine primers were added, 
and the engine nacelles were redesigned.  The tail span was increased 
by two feet.  

With all these changes, the XB-24 was redesignated XB-24B and 
reserialed 39-680.  The first flight of the XB-24B took place on 
February 1, 1941.  The performance was markedly improved.  With 
turbosuperchargers fitted, the original takeoff power of 1200 hp could 
be maintained to well above 20,000 feet, resulting in an increase in 
maximum speed to 310 mph.  Turbosuperchargers remained a feature of 
all later production Liberators.  

Problems with the R-1830-41 engines led the Army to replace them with 
the more reliable 1200 hp Pratt & Whitney R-1830-43 engines.  

Sources:

    Famous Bombers of the Second World War, William Green, 
    Doubleday, 1959.

    Liberator: America's Global Bomber, Alwyn T. Lloyd,
    Pictorial Histories Publishing Co, Inc, 1993.

    B-24 Liberator in Action, Larry Davis, Squadron/Signal Publications
    Inc, 1987.

    General Dynamics Aircraft and Their Predecesssors, John Wegg,
    Naval Institute Press, 1990.

    Consolidated B-24D-M Liberator IN USAAF-RAF-RAAF-MLD-IAF-CzechAF
    and CNAF Service, Ernest R. McDowell, Arco, 1970. 

    United States Military Aircraft Since 1909, Gordon Swanborough
    and Peter M. Bowers, Smithsonian, 1989.

    American Combat Planes, 3rd Enlarged Edition, Ray Wagner,
    Doubleday, 1982.

    Jane's American Fighting Aircraft of the 20th Century,  Michael
    J.H. Taylor, Mallard Press.


Joe Baugher			  **************************************
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