YF-22 vs YF-23

[zero-one]

Unrelated question.
Metz said the ATF program was a competition on 3 systems
-Engines
-Airframes
-Avionics.

The goal was to develop next generation versions of all 3.
Regarding engines, the YF-119 was deemed more conventional.

So I tried to dig up what advantages it may have against the YF-120 if any?
The only thing I found was that the 119 seemed to be the first to use Single-Crystal super alloys while the 120 did not.
I know someone here already said the EJ-2000 and I think F414 also used this.

I can't find specific figures for the YF-119 but compared to production F-119 vs YF-120, the former has a higher thrust levels both dry and wet
Dry: 26,000/23,500
Wet: >35,000 /35,000
I think these are both uninstalled static, sea level rates

Anyway, is the use of super-alloys the only thing that made the 119 "next gen" technology?

[marsavian]

And yet Northrop's better broadband stealth won them the B-2 over Lockheed's design.

Yes but
https://aviation.stackexchange.com/ques ... -trim-drag

Lockheed was floored by this as they thought they beat them hands down in radar testing

I believe that quote actually came from this link

https://foxtrotalpha.jalopnik.com/lockh ... 1534057907

Both teams walked away very proud of their designs, but the contest was clearly closer than the XST competition years before. Then the results were released. Underdog Northrop was selected to produce the Advanced Technology Bomber. Lockheed was floored by this as they thought they beat them hands down in radar testing and their design was cheaper and less risky having leveraged lessons learned during the then budding F-117 program. Northrop disagreed with Lockheed's complaints, with management saying that they (Northrop) dominated Lockheed not just for radar cross section (RCS) testing but also in performance and overall capability.

The tailless Northrop design was more efficient, with claims of 5-10% better aerodynamic performance, and their rounded solution for reducing radar reflectivity, born in the XST program and refined with "Tacit Blue," was seen as more effective against multiple bandwidths of radar emissions, not just the ones that are the most threatening historically. Additionally, this "broadband" stealth capability, although less effective than a tailor made aircraft specifically configured to defeat certain radar bands from certain angles, was thought to be more resistant to potential future enemy radar capabilities aimed at spotting stealth aircraft. Northrop also had an advantage over Lockheed when it came to sensor integration for their design. Tacit Blue was basically a nearly invisible flying radar surveillance platform. Northrop had made great strides not only in making the aircraft hard to detect, but also making Tacit Blue's radar emissions near-undetectable. This was a major advantage considering the ATB would be fielded with hugely powerful radar arrays for targeting. Stealth is worthless if your radar emissions give your position, or even your presence away. Metaphorically it would be like being invisible in the middle of a football game while screaming at the top of your lungs. You may be a little harder to find but with all those alert people on the field it won't take long till someone hears you.

Finally, Northrop's flying wing was a larger aircraft than Lockheed's, with more range and payload, but it was also expensive. Very expensive. Lockheed's estimate to put "Senior Peg" into production was $200 million a copy, a number Ben Rich's Skunk Works team was very confident with after bringing the F-117 into production. Northrop's bid was about double that figure. Yet this was during the dawn of the Reagan era, where defense spending was about to super-nova. During this time of great investment into the US military, the DoD was no longer interested in the "affordable" solution, they wanted excess capability, even at great cost. Thus, Northrop would proceed on to produce the B-2 bomber as we know it today.

[mixelflick]

I got the impression GE''s engine suffered from the same issue as the YF-23A itself: It was too far of a reach, with some unknowns that represented unacceptable risks. Maybe I'm wrong about that, but it's what I gathered after everything I read.

Both engines were monsterously powerful, at least equal to what's being tested today in Russia. And this was 30 years ago!

[quicksilver]

‘More thrust’ is less difficult than ‘more thrust w/ more component/hot section life’.

[zero-one]

‘More thrust’ is less difficult than ‘more thrust w/ more component/hot section life’.

well the 119 did have those super alloys for the hot section. I'm not sure if the 120 had it too. So far my limited research yielded no mention of the YF-120 using it

I got the impression GE''s engine suffered from the same issue as the YF-23A itself: It was too far of a reach, with some unknowns that represented unacceptable risks.

Well that implies that the YF-23 and YF-120 were more advanced designs, I don't necessarily agree with that. I think both designs had their own share of advancements over the competition. The YF-120 may have been more risky but risk does not necessarily equate to being more advanced.

By the way is Variable Cycle and Adaptive Cycle engines the same thing? If so, why is ADVENT still under development stage

[sprstdlyscottsmn]

By the way is Variable Cycle and Adaptive Cycle engines the same thing? If so, why is ADVENT still under development stage

because the YF120 was scrapped and was designed 30 years ago. Anyone who worked on that is likely retired so all institutional knowledge is lost. ADVENT is a clean sheet development trying to bring back what YF120 promised.

[quicksilver]

What I was trying to get at was/is that the ‘juice’ of ‘more thrust‘ isn’t always worth the squeeze if it is not accompanied by equivalent or better reliability. Engine makers can ‘turn up the wick’ very easily, but that almost automatically comes at the expense of life/MTBR.

Similarly, there are some technologies that may be demonstrable at a given technology readiness level that don’t necessarily translate to a production equivalent — for that reason...the practical matters of reliability and/or maintainability.

[f119doctor]

Unrelated question.

So I tried to dig up what advantages it may have against the YF-120 if any?
The only thing I found was that the 119 seemed to be the first to use Single-Crystal super alloys while the 120 did not.
I know someone here already said the EJ-2000 and I think F414 also used this.

I can't find specific figures for the YF-119 but compared to production F-119 vs YF-120, the former has a higher thrust levels both dry and wet
Dry: 26,000/23,500
Wet: >35,000 /35,000
I think these are both uninstalled static, sea level rates

Anyway, is the use of super-alloys the only thing that made the 119 "next gen" technology?

Single crystal super alloys predated the YF119 engine. Pratt & Whitney introduced the use of single crystal turbine blades on the commercial JT9D-7R4 engine. The F100-PW-220 introduced them into military engine usage using the PW proprietary 1480 superalloy, which was part of the improvements that extended the core overhaul interval from 1800 TAC cycles to 4000 TAC cycles with the -220 engine. The improved PW 1484 alloy is used in the turbine airfoils of the F100-PW-229 engine, the F119, and most if not all of the current production commercial engines. I'm sure that the YF120 had single crystal turbine airfoils.

There are many advances that were incorporated in the YF119 Dem/Val engine and further advances in F119 EMD / production engine. Integrally Bladed Rotors in the Fan and High Compressor with advance aerodynamics provided high airflow and high pressure ratio. Advanced cooling and superalloy / single crystal airfoils in the hot section enable reliable and durable operation at unprecedented turbine inlet temperatures. A low bypass ratio (i.e. large core module) optimized the engine to maintain Mil Power high exhaust velocities and thrust under the high temperature inlet conditions of supercruise (approximately 100F at 40K, 1.5 Mn at standard day conditions).

During the YF-22 / YF-23 Dem/Val flight test, the YF120 was a larger engine than the YF119, which had been sized for a 50K gross weight aircraft and was undersized for both of the aircraft with their weight growth. The production F119 has approximately 10% higher airflow than the YF119, along with other design improvements that significant increased the thrust from Dem/Val, while decreasing the specific fuel consumption. And, as Quicksilver notes - the F119 meets its durability targets and routinely makes it to its module overhaul target of 4325 TCY cycles.

While the YF120 with its variable cycle was arguably the more advanced engine, it may not have demonstrated that feature translated into higher performance throughout the flight envelope. I remember that Aviation Week published an article when the YF-22 with the YF120 demonstrated the 1.58 Mn supercruise point, they listed the fuel flow number at that condition. It just so happened that we had our YF-22 with the YF119 at the exact same altitude and Mn that week. The YF119 could not maintain that speed at Mil power, but could at Minimum AB. However, the YF119 engines were burning 1000 lbs/hour less fuel, even at the Min AB setting. While not technically supercruise, burning less fuel supersonic was the whole point.

[zero-one]

I remember that Aviation Week published an article when the YF-22 with the YF120 demonstrated the 1.58 Mn supercruise point, they listed the fuel flow number at that condition. It just so happened that we had our YF-22 with the YF119 at the exact same altitude and Mn that week. The YF119 could not maintain that speed at Mil power, but could at Minimum AB. However, the YF119 engines were burning 1000 lbs/hour less fuel, even at the Min AB setting. While not technically supercruise, burning less fuel supersonic was the whole point.

thats amazing, so the production F119 was even more efficient despite being bigger than the YF119?

I've read on other forums that the SFC was indeed the tipping point, as the YF-120's VCE efficiency was only available at very specific conditions where as the 119 was more efficient at most conditions.

However they could not present any sources to those claims,

[f119doctor]

By the way is Variable Cycle and Adaptive Cycle engines the same thing? If so, why is ADVENT still under development stage

because the YF120 was scrapped and was designed 30 years ago. Anyone who worked on that is likely retired so all institutional knowledge is lost. ADVENT is a clean sheet development trying to bring back what YF120 promised.

Variable / Adaptive Cycle is challenging to make work well.

1. For subsonic cruise, you want high airflow / low pressure ratio fan for propulsive efficiency, and a small hard working core (high pressure ratio, high turbine inlet temp) for thermal efficiency.

2. For supercruise, you want a high airflow / high pressure ratio fan for high exhaust velocity / supersonic thrust, and a large core module with the power to drive that demanding fan, with enough rotor speed and temperature margin to maintain that power to 100F inlet conditions at 40K, 1.5 Mn supercruise conditions.

The challenge is that when you open up Adaptive Fan airflow path for the subsonic cruise optimization, it takes less power to run the fan. As the large supercruise core module is run at this lower power condition, the lower pressure ratio and turbine temperatures drive the thermal efficiency of the engine way down. What you gain in propulsive efficiency is offset by the lowered thermal efficiency. While I don't know this for a fact, this may have been one of the shortcomings of the YF120.

In my opinion, to make the Adaptive cycle live up to its potential will require a design that makes the core module effectively smaller (lower airflow), while maintaining a high pressure ratio. I know that P&W has a concept to achieve this, and it will be interesting to see if this can be developed into effective and durable hardware for the XA101.

[f119doctor]

thats amazing, so the production F119 was even more efficient despite being bigger than the YF119?

I believe that the part power and Mil power SFC is better for the F119 than the YF119. Specific values have not been released publicly, but a lot of work went into the F119 during EMD to improve SFC. But it is not magic - the numbers are same ballpark as other low bypass turbofans.

However, since the F119 does make more thrust than then YF119, it likely has a higher Mil power fuel flow

[zero-one]

Thanks F119doctor.

I take it that you were involved in ATF program in one capacity or another. If you read my other post, I noticed that YF-23 and YF-120 camp had been more vocal about the advantages of those designs compared to the winning proponents.

The YF-22 and YF-119 seem to be very hush about the topic. It's possible that they simply don't want to add insult to injury but if I may have your opinion, What set the YF-119 apart from the YF-120 that gave it the edge?

The common notion is that it was simply the safer, lower risk option, there may be some truth to that but I would like to know your personal opinion

[quicksilver]

Zero, ‘FSR’ = Fleet (or Field) Service Rep. ‘Tech Rep’ in my world; the best ones were/are life-savers.

[f119doctor]

Zero, ‘FSR’ = Fleet (or Field) Service Rep. ‘Tech Rep’ in my world; the best ones were/are life-savers.

Thanks for the kind words Quicksilver. I spent over 30 years as a P&W Tech Rep, mostly with the USAF at Luke, Edwards (twice), and Nellis (three times), and helping the customer keep the engines running right was one of the best jobs in the world.

Thanks F119doctor.

I take it that you were involved in ATF program in one capacity or another. If you read my other post, I noticed that YF-23 and YF-120 camp had been more vocal about the advantages of those designs compared to the winning proponents.

The YF-22 and YF-119 seem to be very hush about the topic. It's possible that they simply don't want to add insult to injury but if I may have your opinion, What set the YF-119 apart from the YF-120 that gave it the edge?

The common notion is that it was simply the safer, lower risk option, there may be some truth to that but I would like to know your personal opinion

I was part of the P&W flight test team at Edwards during the ATF Dem/Val and later during F-22 EMD Flight Test. The team consisted of Flight Test Engineers, Performance System Analysis, Controls Engineers, FSRs, and a great group of company engine mechanics that ensured the engines were ready to support the flight test program, and to gather the data needed to achieve the test objectives.

Why did the F119 win ? Remember that the competition was two parts:
1. Demonstration / Validation using the prototype engines and aircraft where you both demonstrated what your product could do, but more importantly validated your performance predictions. While the YF119 was undersized and marginal with supercruise performance, the P&W PSA engineers in conjunction with both Lockheed and Northrup were accurate in predicting the supercruise performance of both aircraft within 1%
2. The Engineering & Manufacturing Development (EMD) proposal for what you were going to build for production. Both Lockheed and P&W were very good at reading the RFP to determine exactly what USAF was asking for, and ensuring that their proposals addressed every point, with the Dem/Val results to back up their promises.

I believe that the YF119 engine was a more complete product than the YF120 during Dem/Val. The Dual Channel FADEC control system was more developed, the exhaust nozzle was more reliable (and even still carried the thrust reversing architecture that was no long an ATF requirement), LO consideration were part of the design if not fully incorporated in the YF119, and the engine was very reliable for being limited production flight test article (only 6 flight engines were built).

The F119, as developed through EMD after winning the competition, is a great engine. Anyone who has worked on it will tell you it is an engine mechanics dream. You can change the Main Fuel Throttle Valve (main engine control) by disconnecting two electrical harnesses and backing out 12 bolts - no fuel lines to disconnect. Same for the Augmentor Fuel Control. No Safety Wire, standard sized fasteners to reduce the number of wrenches needed, no engine trim needed. All LRUs are grouped for easy access on the bottom of the engine, all just one deep so you don't have to remove one component to reach the one you want. Most LRUs can be operationally checked just by starting the engine to Idle power, no need for a high power tie-down. And the performance, as anyone who has seen the F-22 demonstration flight, isexceptional, even though some of the static thrust and weight numbers some people have speculated on this forum are significantly exaggerated.

[disconnectedradical]

Single crystal turbine blades aren’t new for F119, but newer alloys and more advanced cooling would allow higher turbine temperatures. YF120 used single crystal turbine blades too.

YF120 was the more advanced but riskier engine and it showed in Dem/Val. According to Paul Metz there were two incidents with the YF120 on YF-23, one was where one engine went sub-idle and there was loss of hydraulic fluid, though these weren’t inherent problems with the engine. Also the engine control had to deal with the variable cycle design and for the prototype engines that resulted in very big throttle input lags, which made some tasks very difficult, so for aerial refueling in YF-23 with YF120 engine they put one engine in idle and only used the other throttle to adjust speed. These were issues that would get resolved if the engine was actually chosen for EMD but for Dem/Val these shortcomings existed. Also, the EMD F120 reached YF120 thrust level at lower temperatures during ground test runs. Metz doesn’t say it directly but he does seem to put more emphasis on how reliable the F119 is.

By the way is Variable Cycle and Adaptive Cycle engines the same thing? If so, why is ADVENT still under development stage

because the YF120 was scrapped and was designed 30 years ago. Anyone who worked on that is likely retired so all institutional knowledge is lost. ADVENT is a clean sheet development trying to bring back what YF120 promised.

Also, YF120 and ADVENT have different design, YF120 still use two streams with variable bypass but ADVENT is focused on three stream design.