Subject: Number Eighty-Nine in the Series--Northrop F-89 Scorpion (2 of 10)

From: [email-masked] (Sci.Military Login)
Date: 20 Sep 93 16:21:11 GMT

>From  

The first production version of the Scorpion was the F-89A (Model 
N-35).  Forty-eight F-89As had been ordered on July 14, 1949.  
Production of the F-89A got underway even while the XF-89 and YF-89 
were still under test, but the crash of the XF-89 prototype on 
February 22, 1950 brought the whole program to a halt while the 
problems were being fixed.  

At the time of the XF-89 accident, three F-89As were nearing 
completion.  It was decided that these three machines, acting in 
conjunction with the YF-89A, would be the test force used to wring out 
the problems with the Scorpion.  The first production F-89A was 
accepted by the USAF on September 28, 1950, followed by the second and 
third examples a few weeks later.  

The F-89A could be distinguished from the YF-89A by the mounting of an 
armament of six 20-mm T-31 (M-24) cannon in the nose with 200 rpg.  
Underwing pylons were provided which could carry sixteen rockets or up 
to 3200 pounds of bombs.  An AN/APG-33 radar was fitted in the nose.  

The fix for the tail flutter problem was found to be the fitting of a 
series of external mass balance horns attached to the hinge area of 
the horizontal stabilizer/elevator.  The configuration of the 
underfuselage exhaust deflector fairings was changed, and a number of 
different fairing designs were tried until a final design was adopted.  
The lines of the rear fuselage behind the jet pipes were altered to 
overcome some of the excessive turbulence that had been encountered by 
the YF-89A at high speeds.  With these changes, the fail flutter 
problem was finally believed to be cured, and in January of 1951 
production of the F-89A was resumed.  

In the event, only eight F-89As were actually built.  Subsequent 
machines in the original order of 48 had enough changes so that they 
were designated F-89B or F-89C.  

The engines of the F-89A were originally a pair of Allison J35-A-21s.  
After a rash of engine failures on early F-89As, these aircraft were 
reengined with Allison J35-A-21A turbojets, rated at 5100 lb.st.dry 
and 6800 lb.st with afterburning.  These engines had an engine oil 
scavenging system and different kinds of afterburner eyelids, which 
gave smoother afterburner control.  

The external mass balances on the early F-89As were eventually 
replaced by elevators with internal mass balance which were fitted 
retroactively after having been developed for the F-89C.  

Several obsolete F-89As were later modified into radio-controlled 
target planes under the designation DF-89A.  

49-2438 was used by General Electric for experimental work under the 
designation JF-89A.  

Serials:

49-2431/2438 	Northrop F-89A Scorpion 

Sources:

  United States Military Aircraft Since 1909, Gordon Swanborough
  and Peter M. Bowers, Smithsonian, 1989.
  
  F-89 Scorpion in Action, Aircraft Number 104, Larry Davis and 
  Dave Menard, Squadron/Signal Publications, 1990.

  Fighters of the United States Air Force, Robert F. Dorr and David 
  Donald, Temple Press Aerospace, 1990.

  The American Fighter, Enzo Angelucci and Peter Bowers, Orion, 1987.

  American Combat Planes, Third Enlarged Edition, Ray Wagner,
  Doubleday, 1982.

Joe Baugher		AT&T Bell Laboratories   	
2000 North Naperville Road      Naperville, Illinois 60566-7033