looking for information on the General Electric MF-295 turbofan engine

[Pioneer]

G'day

I'm looking for information on the defunct General Electric MF-295 turbofan engine, which was a contender to power the USAF/USN TFX /F-111. I've never picked up on this before, in regards to the TFX/F-111 program, until just now :-[

"The MF-295 was in early phase of development but promised significant size, weight, and performance advantages. All the bids [for TFX] except General Dynamics bid used the MF-295 engine....."

(source: Boon Seh Choo et al, 2003. F-111 Case Study

Is there anything already existing on this forum in relation to the GE MF-295?

Regards
Pioneer

 

[GeorgeA]

I haven't found much. There's a meh picture in GE's internal Eight Decades of Progress book and a small writeup -- simply that the MF-295 was a late entry in the first round of the TFX competition, was "smaller, lighter, and more powerful" than the TF30, and was Boeing's preferred option. It was going to be about two years late relative to the TF30 simply because GE got a late start on it.

 

[sferrin]

"McNamara presented his case in favour of
the General Dynamics/Grumman proposal
and won his adversaries over, citing better
fatigue life, higher maximum speed, lower
radar signature and superior electronic
countermeasures capability.
McNamara conceded that the Boeing
proposal appeared to have superior ferry
range, loiter capability and low speed
handling – at least on paper – but he was able
to convince the hearing that Boeing's costings
were unrealistically optimistic. That turned
the tide in favour of his original selection.
Hindsight tends to confirm McNamara's
opinion. Boeing's proposed powerplant, the
General Electric MF-295 turbofan, existed
only as a set of specifications at the time and
would not have been ready to fly before 1967,
while General Dynamics' Pratt & Whitney
TF30 was at an advanced stage of design."

From AeroAustralia re. the F-111B.

 

[Dynoman]

Another couple of issues with the MF-295 was that Boeing planned for the TFX to have inflight thrust reversing for deceleration instead of an airbrake as General Dynamics had proposed. Concern over the impingement of the exhaust around the flight control surfaces and that it had not been implemented in to fighter aircraft of the age were concerns for the DoD. Boeings design also included a dorsal mounted inlet with a subsonic diffuser system that the DoD believed could cause distorted flow to the engines at high angles-of-attack. The M-295 engines were smaller and possessed higher technology (I believe it had more titanium in the engine, as well as in the wing pivot box), but as mentioned before, it was just a proposal and its associated development risk was too much for the DoD to consider against GD's more conventional engine design. The AF liked the smaller engines as it reduce fuselage diameter, thus reducing drag and increasing range.
GD's MF-295 was supposed to use components of the J-79 and J-93 engines in order to make it less 'risky' for DoD planners. The GE design was thought to be such a good concept that Lockheed, North American Aviation, and McDonnell Douglas also considered the MF-295 in their designs.

 

[GeorgeA]

From Eight Decades of Progress:

. . after originally submitting the J79 and not having it selected by any of the competing airframe companies, General Electric promptly came up with a new design, the MF295, a dual-rotor, front-fan power plant.

The Fortune article said, " . . . MF295 was several hundred pounds lighter than the Allison or Pratt & Whitney engine, and was smaller in both length and diameter. This promised relief from the crushing limitation on weight, and it also permitted the narrow fuselage so critical to the Air Force's supersonic requirements." . . .

Boeing . . . decided to switch to the MF295 . . . other contractors apparently shared Boeing's views, for North American, McDonnell, Douglas, Lockheed, . . . eventually switched to the MF295.

GE proposed the MF295 over the strong objection of a number of veteran engineers and some management within the company. The design represented two concepts -- the dual rotor . . . as a way of achieving increased compressor pressure ratio, and the front fan-- both differing from GE design principles at the time.

 

[Pioneer]

Thank you gents for your feedback and input!

Boeings design also included a dorsal mounted inlet with a subsonic diffuser system that the DoD believed could cause distorted flow to the engines at high angles-of-attack.

Considering the distorted flow to the engines issues the General Dynamics F-111 had, which necessitated extensive research, development which lead to the Triple Plow fix, one might wonder if the DoD's concerns were overly conservative, considering the technological advancement of the TFX program - period!

Regards
Pioneer

 

[Dynoman]

True the F-111 inlets could have been designed better during the preliminary design phase, with engineers having to move the inlet further outboard away from the boundary layer of the fuselage and away from the wing glove as development continued. The Boeing 818 dorsal inlets were probably designed around the original mission of strike-interdiction as opposed to a fighter design with maneuverability as a design driver. Inlets on the top, mounted far reward, works to eliminate radar reflections from the bottom of the aircraft. Careful design of leading edge extensions can help to re-energize the flow of air to the dorsal inlets at increased AoA to control pressure recovery and dynamic distortion, allowing the design to reach comparable angles found in fighter aircraft. However, in the early 1960's, there were too few practical designs of combat aircraft to compare the Boeing dorsal inlet proposal to, resulting in its inlet's general rejection.

 

[Pioneer]

True the F-111 inlets could have been designed better during the preliminary design phase, with engineers having to move the inlet further outboard away from the boundary layer of the fuselage and away from the wing glove as development continued. The Boeing 818 dorsal inlets were probably designed around the original mission of strike-interdiction as opposed to a fighter design with maneuverability as a design driver. Inlets on the top, mounted far reward, works to eliminate radar reflections from the bottom of the aircraft. Careful design of leading edge extensions can help to re-energize the flow of air to the dorsal inlets at increased AoA to control pressure recovery and dynamic distortion, allowing the design to reach comparable angles found in fighter aircraft. However, in the early 1960's, there were too few practical designs of combat aircraft to compare the Boeing dorsal inlet proposal to, resulting in its inlet's general rejection.

Interesting Dynoman

Thank you for your input.

Regards
Pioneer