J79-GE-200 series engines

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nmeier23

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From the G-111 thread: https://www.secretprojects.co.uk/threads/grumman-design-118-not-the-xf12f.491/, the production aircraft was proposed with J79-GE-207 engines.

As far as I know the proposed J79-GE-207 model is the only reference to a -200 series J79 that I know of.

Does anyone have further details of this or any other -200 series of the J79? Is it an evolution of the -7 variant?


Nathan
 
nmeier23 said:
From the G-111 thread: https://www.secretprojects.co.uk/threads/grumman-design-118-not-the-xf12f.491/, the production aircraft was proposed with J79-GE-207 engines.

As far as I know the proposed J79-GE-207 model is the only reference to a -200 series J79 that I know of.

Does anyone have further details of this or any other -200 series of the J79? Is it an evolution of the -7 variant?


Nathan
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The J93 was originally designated J79-X279E (Source: A Brief History of Aircraft Engine Development at General Electric) and came from the earlier J79-X275 enlarged J79.


References in a nuclear aircraft report (ANP) to

"Estimated Performance of J79-X207A Turbojet Engine," GE-AGT, April 15, 1957.
"J79-X207A Bulletin Assumptions and Calculation Methods," GE-AGT, DF57AGT33, April 10, 1957

Several references on the forum to 1956/57 era projects with GE J79-X207 or J79-X207A engines.

From Tony Chong's Flying Wings and Radical Things

NorthropN167.JPG
 
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Of the larger engines the afterburning J79-GE-X207 (thrust 18,000 lbs, T/W = "5.4) was preferred because it was reasonably certain to be available in 1960 and had a good T/W. Further, more advanced derivatives of the J79 being explored by General Electric, such as the J79-GE-X275A, opened up the possibility of appreciable growth potential to J79-GE-X207-equipped VTOL aircraft recommended for development by Ryan.
Click to expand...

 
The J79-X207/X207A was a high performance (16-18,000lb) J-79 derivative project in 1955-1957. If built, it would have got a separate J79-GE-x designation. Earliest mentions are 1955 when it is a higher performance alternative to J79-GE-3.

In fact I think J79-GE-10 (1968?) was the first model to reach these levels of performance.
 
It appears after some study that the GE Jaa-Xnnn designation is a transitional portmanteau form mixing the base military designation of Jaa (such as J79) with an internal GE variant designation X-nnn (such as X-207) to describe an engine that has not received a fully qualified military designation (such as J79-GE-10). After the military designation has been assigned, it appears that the internal GE designation is dropped from all production documentation.

GE apparently dropped the "X" system (possibly circa 1970) and replaced it with a four character alphanumeric system where the first two characters denote the engine type/family and the last two define the particular version (at least that is what it looks like!).

Examples include:
F1D2 -> Unaugmented F404 for the F-117
F5D2 -> F412 for the A-12 ATA

An alternate system appears to be in place for international sales:
INS6 -> F414 for HAL Tejas MKII

This should not be confused with the similar-appearing Pratt & Whitney X-nnn system where nnn was the serial number of a test engine and had absolutely nothing to do with the engine nomenclature, designation or specification.

Clear as mud?
 
Some General Electric J79-X207 specs from the paper VTOL Transport Aircraft, Interim Summary Report No. R-75 by Vertol, dated September 9th 1957, available on DTIC here. Screenshot of the original attached in case the link dies.

The values of specific fuel consumption and specific weight of theGeneral Electric J79-X207 single rotor, high pressure ratio turbojetengine, which is scheduled to con^lete its qualification testing in1959, have been used as control points for Figures V-6, V-7, and V-6,General Electric has estimated the weight and minimum sea level,static performance of this engine as follows:

Rating​
% RPM​
Net Thrust Pounds​
Net SFC lbs /hr /lb​
Maximum
100​
18,000​
1.670​
Military
100​
12,000​
.834​
Cruise
95​
9,475​
.767​
90​
7,500​
.745​
85​
5,280​
.775​

Weight with high augmentation afterburner = 3,500 pounds
Weight as a non-augmented engine = 2,000 pounds
Click to expand...

Courtesy of a paper he produced for the American Society of Mechanical Engineers (ASME) on industrial continuity following nuclear attack we know that the manager of the J79-X207 project within the General Electric Aircraft Gas Turbine division, as of June 1956, was B. W. Bruckmann.
 

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