Terrible Jet Engines of the Fifties

[Steve jahn]

I've been re-reading a lot of my books on the early jet fighters of the fifties. As a lot of you know, terrible engine designs were the death of some of these planes. I have read a lot about the F7U-1 Cutlass and again, the Westinghouse J-46 did not allow the plane to perform like it should have. When I set my Ginter book on the F7U-1 on my desk, it landed next to an F-86 book I was also looking at. A bell went off in my head. J-46 engine, sucks. J47 in the F-86, great engine. Why did no one suggest, hey, lets try the J47 in the Cutlass. It would have been a perfect engine. Just seems like an obvious choice to me. What do you think?

steve

[Fellow Hobbyist]

It would not have been a simple proposition to do that.

For one thing the physical dimensions and weights of the two engines are very different. The J47 is approximately 50" longer than the J46, the difference in diameter between the two engines is 5" and the J47 weighs 600 lbs more than it's predecessor. Designers could not simply pull out the two J46 engines from the Cutlass and bolt in the two J47. Much of the airframe would have to been redesigned to accommodate the larger, more powerful engine.

The end result might be an entirely different airplane all together. But as history would have it designing an entirely new plane to replace the Cutlass was exactly what Vought did.

Edited May 27, 2013 by Fellow Hobbyist

[ross blackford]

:D, Australia in the 1950s went through exactly those dramas when we decided to replace the J-47 engine with the RR Avon in our Sabres. Some 65% of the Sabre's fuselage design had to be changed to fit the Avon in but it did give us probably the most powerful and useful Sabre variant until perhaps the F-86D and F-86K came along a couple of years later.

I think I read somewhere that our Sabres were also the only ones to carry Sidewinder missiles. I can't say that for sure but I do remember seeing them armed with Sidewinders in the late 50s and again as an ATC cadet in the mid to late 60s when I did a couple of camps at Williamtown. That's the reason why the RAAF said a resounding "no" to Dassault's suggestion that they power the Mirage IIIO with the Avon as well, even though Dassaults had already done all the hard work on the conversion and had built a company funded prototype of the Avon powered Mirage IIIO.

Another reason is that the Avon didn't offer that much more performance than the Atar did so it wasn't considered worth the effort to make such a change, even though the RAAF still had Avon powered Canberras very much in service when the Mirages came into service in the early 60s and this was also the reason for re-engining the Sabres. Because of the small size of the RAAF they wanted economies of scale by having a common engine in their fighter and bomber fleets. Sometimes it is just easier and quicker and cheaper to design a new aircraft than to play around with such conversions. Although, having said that there probably would have been more dramas to convert the cutlass to the J-47 than there were to convert the Sabre to the Avon. And there were enough dramas doing that.

,

Ross.

[Johnopfor]

I think I read somewhere that our Sabres were also the only ones to carry Sidewinder missiles. I can't say that for sure but I do remember seeing them armed with Sidewinders in the late 50s and again as an ATC cadet in the mid to late 60s when I did a couple of camps at Williamtown. :cheers:/>,

Ross.

Taiwanese and Pakistani Sabres saw combat armed with the AIM-9B.

[ALF18]

I found this interesting little thread that talks in general about several early jets, particularly the failed Westinghouse ones.

http://www.secretprojects.co.uk/forum/index.php?topic=5976.0

Jet engines of that era were far more delicate than today's. The worst were the centrifugal flow engines - instead of an axial design with the air flowing through a series of compressor blades to the combustion chamber, they had a huge impeller that threw the air outboard and compressed it at the same time, like a huge vacuum cleaner. One example I have flown was the Nene 10 engine in the Canadian T-33 jet trainer. It idles at 20% RPM, while axial flow engines I know idle much higher in RPM (the J-85 on the Tutor and F-5 at 50%, the F-404 in the Hornet at 62%).

So idle at 20%, but the pilot had to advance the throttle to 26% to get the generator to come on line (any slower, and it would kill the engine). Engine acceleration from idle to about 70% was PAINFULLY slow. The throttle had to be advanced in small, slow increments, with exhaust gas temperature (EGT) rising in little spikes toward overheating/toasting the rear end with each advance of the throttle, until the RPM slowly caught up to the higher fuel flow.

By the time you got to 65 to 70%, you could advance the throttle more quickly, but still gingerly, until you hit max RPM. And even then, you had to inch it back from the forward stop, because it would overspeed if left at the forward limit of throttle travel.

In short, it had very manual control. An approach to a touch-and-go landing was not simple in the T-33 when it came to engine handling. Even when you had too much power (i.e. you were a bit fast and high), you were forbidden to reduce the throttle below 65% by standard procedure, because the spool-up time from idle to 65% was so slow you would never get any useful thrust before crashing if you needed to overshoot. When landing was assured, you could reduce the throttle to about 30%, but not any lower unless you wanted to drop the generator off line. After you touched down, you struggled to hold the nose off the ground, slowly advanced the throttle, and hoped it would not overtemp as the runway disappeared behind you, as you slowly gained flying speed again. It was possible to do it by sound; the engine would emit a throaty roar as it teetered on the edge of overtemping as you advanced the throttle as fast as you safely could, and too much of a roar signaled an overtemp. When you got to 70%, you could move it smartly forward to get enough thrust to take off again, then had to pull it back to avoid overspeeding in RPM.

Contrast this to the J-85, J-79, J-57, F-404, etc (all modern jet engines). From idle, you could literally slam the throttle to full forward as fast as you could move the lever, and the fuel control unit provided just enough fuel flow to accelerate it quickly to full military power, without any fear of an overtemp or overspeed. My father told me how in the CF-104 they did their best to slam the throttle quickly from idle to high thrust with the brakes off before rolling on take-off, to make sure the engine was behaving, before chopping it to idle, then slamming to full mil and then afterburner for take-off. They would sit on the runway belching black smoke and howling away as only Starfighters could, then shook the whole world as they blasted off. A far cry from the temperamental old engines on the 50s vintage jets.

My hat's off to the engineers who have created worry-free jet engines for us.

ALF

[ross blackford]

:D, Thank you for that snippet of info Johnopfor. I was aware that Sidewinder armed RAAF Sabres flew out of Ubon in Thailand on clandestine mission over Vietnam early in that war but was unaware that any other nation had Sidewinder armed Sabres. You learn something new every day.

,

Ross.

[Tailspin Turtle]

Some background on the Westinghouse engines: http://thanlont.blogspot.com/2011/03/from-hero-to-zero.html

[Bad Turbine]

Lets not forget the Allison XT-40 Turboprop which was two engines going into a common gearbox. Problems with that thing caused the cancellation of half a dozen programs.

[Steve jahn]

Some background on the Westinghouse engines: http://thanlont.blogspot.com/2011/03/from-hero-to-zero.html

Tailspin.

That was an excellent article on Westinghouse.

Steve