Tornado F3 - asymmetric engine configuration ?

[Fonsini]

An F-14 exchange pilot was talking about his time on an F3 squadron around about the time that the squadron relocated from Coningsby to Leuchars. He admittedly poured scorn on the abilities and lack of sophistication of the F3 compared to the F-14D he transitioned from, but reserved especially harsh comments for the donks claiming that the 2 engines were not only grossly under-powered at altitude (hardly a new critique) but were also asymmetrically configured, one optimized for low level flight and the other for high level flight, even to the extent of one intake being fitted with strakes to optimise airflow while the other was not.

This doesn’t make much sense to me but the guy had over 600 hours on type over a period of 3 years so I assume he knew what he was talking about, is there any truth to this set-up in the F3 and if so what is the logic behind it ?

[ASRAAMTOO]

Its been a while, but my recollection is that the intake strake arrangement did differ. If there were no strakes the port engine intake would present airflow to the face of the compressor right to left as viewed from the front and the starboard one left to right as viewed from the front. Both engines rotated in the same direction so without strakes the airflow would differ as it entered each engine.

[ORAC]

From elsewhere - There are fences in both intakes But in different places. One intake is optimised for high AOA, and the other for low speed airflow. The idea is that it's less likely that gross mishandling will flame-out both engines at the same time.....

Cowl fence in the left hand intake, duct fences in the right. (P1420 below)

http://www.icas.org/ICAS_ARCHIVE/ICAS1982/ICAS-82-4.8.1.pdf

[ORAC]

https://cimg7.ibsrv.net/gimg/pprune.org-vbulletin/1600x1200/image_e9431689ede7d0066857a37b72f9b7180b150ef1.jpeg



https://cimg2.ibsrv.net/gimg/pprune.org-vbulletin/1024x768/image_94ed4f162c1f93890c71fec5c84f7d3aa2cb051f.jpeg

[Lima Juliet]

Those intakes were highly classified for a while. You had to have them covered at Airshows in the really early days.

[Minnie Burner]

Those intakes were highly classified for a while. You had to have them covered at Airshows in the really early days.
Is that an engine or an APU?

[alf5071h]

The Lightning evaluated, and possibly used anti swirl vanes as standard in the engine intake.
I recall 'sitting in' on the RR trials in a T5; the modifications were proposed for T55 (circa 1971)

The engine tests were at low level and started at 650 kts with max power; cut to idle and then slam back to full power. Not even a rumble.
The modification was for several large swirl vanes positioned on the lower surface of the intake aft of the radar bullet ( left side only ?); was this a fleet-wide mod in later years ?

[iranu]

I was a member of the RB-199 Repair Engineering team at RR Filton towards the end on the 1990s. I never came across anything to suggest that individual engines were configured for low v medium/high altitude performance other than the difference between engine marks as part of the development/upgrade path (including mods).

[NutLoose]

As an ex Sootie, that must have made crawling down the intake with the vane interesting..
crawling down the stb Jaguar one was fun enough without steps.


..

[Fonsini]

Excellent information as always, thanks all. My guess is that the asymmetric intake configuration somehow got him confused. I managed to track down the interview on YouTube if you can spare 15 minutes to watch it he makes some interesting observations, not least of which is his statement that the RB199 is in fact a turbojet - oops.

F-14D pilot on the Tornado F3

[Broomstick Flier]

Did the GR versions have the fence too?

[just another jocky]

Did the GR versions have the fence too?

Yes.

Never heard of his assertion; I'm not sure there was anything you could do with the RB199 to make it perform better at altitude....other than replace it with a better engine.

[just another jocky]

Is that an engine or an APU?

16,000lbs thrust......you tell me. :}

[Timelord]

I haven’t seen the interview but could “high and low alpha(or attitude) ” have been misheard as “high and low altitude”? Two nations separated by a common language and all that!

[57mm]

Never had a issue with the donks on the F3, apart from the odd VIB or fire warning in 2500+ hours driving them. The donks on the F2, however.......

[ORAC]

Those will be the early ones with a time between changes of around 70-80 hours, before the ones with single crystal turbine blades developed with Saudi money started to reach the front line?

[Hot 'n' High]

As an ex Sootie, that must have made crawling down the intake with the vane interesting..
crawling down the stb Jaguar one was fun enough without steps. ..

Sooties? We Fairies had to go down there to check the TAT probe was warming up. You either went in 30deg roll right or 30deg roll left. And it always seemed a blooming long way down to the compressor face, the probe being not far in front of it. Of course, you also hoped the ladder was still there when you'd reversed all the way back after the check which, in itself, only took 30 seconds or so. Transit time was quite a bit longer!!! :}

[Peter G-W]

I remember starting the APU with a guy deep inside the right hand intake. He came out in far less than 30 seconds and didn’t require a ladder

[Buster15]

Its been a while, but my recollection is that the intake strake arrangement did differ. If there were no strakes the port engine intake would present airflow to the face of the compressor right to left as viewed from the front and the starboard one left to right as viewed from the front. Both engines rotated in the same direction so without strakes the airflow would differ as it entered each engine.

Exactly. The intake strakes were required to reduce engine surges.

[Buster15]

Yes.

Never heard of his assertion; I'm not sure there was anything you could do with the RB199 to make it perform better at altitude....other than replace it with a better engine.

The engine cycle was optimised for fuel efficiency and range. That is why it had the high bypass ratio.

[just another jocky]

The engine cycle was optimised for fuel efficiency and range. That is why it had the high bypass ratio.

Yes, I know. It was a very focussed aircraft/engine design which showed up when you took it outside its originally intended domain.

[NutLoose]

I remember starting the APU with a guy deep inside the right hand intake. He came out in far less than 30 seconds and didn’t require a ladder

That was always my fear on Jags, I used to let people know in no uncertain terms I was down the intake.

[Buster15]

Yes, I know. It was a very focussed aircraft/engine design which showed up when you took it outside its originally intended domain.

That is quite true. However, its inherent design did allow it to become pretty flexible and adaptable to role changes over its 40+ year life cycle.
But the laws of physics will always apply.

[AnglianAV8R]

I remember starting the APU with a guy deep inside the right hand intake. He came out in far less than 30 seconds and didn’t require a ladder

Thankfully, it is almost Christmas and somebody will buy me a new keyboard.

[iranu]

Yes.

Never heard of his assertion; I'm not sure there was anything you could do with the RB199 to make it perform better at altitude....other than replace it with a better engine.There were a number of programmes ongoing throughout the life of the engine to improve performance and reliability. Need to get my post count to 10 before I can post pictures/urls as I found some info about this on Flight Global via the 'Wayback Machine'.

[iranu]

I remember starting the APU with a guy deep inside the right hand intake. He came out in far less than 30 seconds and didn’t require a ladderHe wouldn't have required a ladder coming out the other end either. :yuk:.

[NutLoose]

Having done a little deep strip on the RB199 you wouldn’t get in the aircraft if you saw the state the innards got to.

[Hot 'n' High]

I remember starting the APU with a guy deep inside the right hand intake. He came out in far less than 30 seconds and didn’t require a ladder

Pete, wasn't me down there - coz you are still alive!!!!! :ok:

Question? I'm sure the TAT probe was only down the Port intake. Not sure what it fed but why only one? Never thought about that!

[Buster15]

Having done a little deep strip on the RB199 you wouldn’t get in the aircraft if you saw the state the innards got to.

You have to remember the the RB199 really was pushing the boundaries of what was possible given the technology at the time and the way the aircraft was being operated. The engine itself is pretty tolerant to the thermal and mechanical loads. And of course there were two of them.

[bridgets boy]

Left and right hand engines rotated the same way, they need airflow coming in at the optimum angle, which could have been facilitated in one intake, but not so in the other, hence the fences to present the airflow at a better angle (but with some energy losses).
We did not learn in 2 generations of aircraft that you need a convergent-divergent nozzle on a fighter jet's engines to work well at altitude. Think Spey Phantom vs J79 Phantom. RB199 vs anything. Not worth it if you stick to low level, the weight and complexity will not pay off vs the marginal advantage, but as soon as you switch from Norfolk Land Shark to fighter mode, con-di nozzle is the way.

[iranu]

Here's the info regarding RB-199 post introduction development:


https://cimg1.ibsrv.net/gimg/pprune.org-vbulletin/791x1018/1986_08641024_1_f3cd802a93895140f09d82f164c2942bc0e4c11a.jpg
https://cimg3.ibsrv.net/gimg/pprune.org-vbulletin/790x1011/1986_08651024_1_c7779355bdab1d1405634a67bfb63861f4b65016.jpg

Iirc the original 'on wing' time was around 100 hours due to the original Mk101 being immature, but that grew considerably throughout the engine programme as the Mk 103/104 came into service and there were some engines which were hitting well over 1000 hours before the GR4 was scrapped. The 1980s XG engines and other varients all contributed to the success of the EJ200.

[Buster15]

Here's the info regarding RB-199 post introduction development:


https://cimg1.ibsrv.net/gimg/pprune.org-vbulletin/791x1018/1986_08641024_1_f3cd802a93895140f09d82f164c2942bc0e4c11a.jpg
https://cimg3.ibsrv.net/gimg/pprune.org-vbulletin/790x1011/1986_08651024_1_c7779355bdab1d1405634a67bfb63861f4b65016.jpg

Iirc the original 'on wing' time was around 100 hours due to the original Mk101 being immature, but that grew considerably throughout the engine programme as the Mk 103/104 came into service and there were some engines which were hitting well over 1000 hours before the GR4 was scrapped. The 1980s XG engines and other varients all contributed to the success of the EJ200.

That is really interesting.
Yes the Mk101 had a number of issues. In particular the Oil System which was not all attitude and so for inverted flight, it had a couple of accumulators to maintain oil supply. That was completely revised on the 103. In order to increase on-wing life, some 101's were do- rated.
Certainly the Mk103 was a better engine in most areas but as expected, the equiaxed high pressure turbine blades still suffered from thermal fatigue.
Introduction of the single crystal blades greatly improved reliability.
Nevertheless, the engine was operated for a great deal of the time at its temperature limit due to the high proportion of time spent at low level.
Surprisingly, the GR4 programme did not include any engine enhancements despite the additional weapons capabilities.

[LOMCEVAK]

There was another asymmetric aspect to the Mk 104 engines in the F3 and that was the surge boundaries. At the tested conditions (21 AOA in a turn, and either slam max dry to idle and when just sub-idle reslam to max dry or slam max dry to sub idle, sweep the wings by one angle change then immediately reslam to max dry) for a given standard of DECU software one engine would always surge at a consistently higher airspeed than the other ie. was the 'critical' engine for surge. However, we did see that following one software upgrade (cannot remember which one) the critical engine swapped from one side to the other with no hardware changes inside the intakes at all. I never did hear a convincing explanation for this.

[Buster15]

There was another asymmetric aspect to the Mk 104 engines in the F3 and that was the surge boundaries. At the tested conditions (21 AOA in a turn, and either slam max dry to idle and when just sub-idle reslam to max dry or slam max dry to sub idle, sweep the wings by one angle change then immediately reslam to max dry) for a given standard of DECU software one engine would always surge at a consistently higher airspeed than the other ie. was the 'critical' engine for surge. However, we did see that following one software upgrade (cannot remember which one) the critical engine swapped from one side to the other with no hardware changes inside the intakes at all. I never did hear a convincing explanation for this.

How interesting. Can you remember approximately when this was. And was it a repeatable event.
And when you say 'sub-idle' can you recall the actual NH.
And lastly, and I apologise for testing your memory, were both engines pilot levers moved in the same way at the same time.
Thank you and thank you for your post.