Courtney, I've been informed that in the modern age, the number of posts a forum member has is apparently proportional to said members implied credibility (much like other modern day institutions where the number of words someone says carries more weight than someone elses experience...). Hence why we see our newer members attempt to get a post or two on every single thread in the forum, regardless of the merit of the post itself. T93 isn't on his lonesome in this regard, but it always sort of screams 'walt' to me when I see it happening.

I've not heard from Engines or the others lately, what is the current state of affairs regarding the F135? A little bird tells me there is go/no go decision to be made regarding the engine and a no go is a potential 'show stopper'.

Any truth on a serious redesign? Is this even viable this late in the project or has the Hydra already grown too many heads to kill?

I suspect that if P&W has to do a major redesign that RR and GE will step back into the picture with their F136 design*.


* That never should have been canceled in my view.

I'm rereading "The Air Force and the Great Engine War" by Drewes. It seems that Pratt has not fundamentally changed its business culture. The F100 was having issues - potentially grounding both the F-15 and F-16 - yet Pratt spent more time trying to derail a competitive engine than fixing the problems. Sounds eerily familiar.

That was the early F100-PW-100 engines. Like this, the problems were due to the advanced nature of the engine and the massive step up in power to weight from anything produced before. Those issues were solved without a major redesign and it may well be that F-135 will go the same way. A component refinement could be the answer. As yet we don't know. I wouldn't write P&W off just yet. This is a very challenging design.

What I would still wonder about is the version in the B model, with massive load from engaging the lift fan. I know it's been flying for a while now, I would love to hear if anyone has any thoughts on what might crop up with it.

Edit: I should mention that I have many hundreds of hours in front of 2 F100-PW-100s. Apart from the JFS (jet fuel starter) they were sweet.

TBOs will be shortened. Hope there is a plan to have plenty of spare parts and additional engines available nearby…

"Hopefully" indeed.

Courtney,

You might have felt slightly different if you were seated over one F100-200 in an F-16. Originally, the problem was compressor stalls when operating within the flight envelope, which got fixed, but the real driver for the USAF to bring on the F110 engine were HPT blade failures that P&W had a hard time eliminating in a timely manner. It had to do with the basic turbine blade material used and accountability for presumed casting defects during the design phase.

Oh, yes, I'm sure I would have done. Apart from anything else, a good input to the 1 v 2 engine debate. Was it an increase in pressure ratio or purely a materials issue? It sounds like there's more to this. :ok:

I was close to Engine War 1 in the early 1980s. Every time I braved the gators in the parking lot and visited WPB, Pratts were sure they had it sorted. Changes in scheduling. Inspections. Fadec... I don't recall all the details and the notes are in storage, but it was not until GE was seriously funded that they got religion and made the -220 and the -220E upgrade kit.

Some good material here:

http://www.dtic.mil/dtic/tr/fulltext/u2/a282467.pdf

As for the current issue, the longer it drags on the worse it looks.

Hi Courtney

You may know what follows but for the benefit of others....

The fan is connected to the engine by a clutch as part of the computer controlled 'conversion' process of the whole aircraft to the STOVL mode. It is done at low engine power. Once the motor car type clutch slip has spun up the fan in this low power configuration some pins are fired into the clutch plates locking them up into a positive mechanical drive condition. Only then is the now semi 'turbo prop' type engine given its head.

Let's not be tough on T93 - he writes like one considering his future. And the one-multi-role-type argument versus the several-single-role-type argument is one that the experts have banged their heads against for decades.

For instance, which equivalent-cost air force would you prefer: 100 F-35s, or 60 F-35s and 80 JAS 39Es?

Well you have more patience the me LO!


I totally agree on the numbers game. It seems we are in a death spiral of:


1) " we are getting short on numbers, better make sure that the kit we buy is multirole"


2) " these multirole machines are expensive to buy and keep going, shame we can't afford many of them"


Goto 1


In many ways I think the USAF is heading for a train crash. They have been keeping kit past its sell by date and now have many platforms they would like to replace soon - KC-135, T-38, B-52, B-1, B-2


Throw in F-15/16/ A-10 all to be replaced by the wonder jet and that the budget is shrinking and something will have to give.


Probably numbers in a big way?


I am sure some in the light blue are sympathetic to the idea of buying a light (cheap) fighter for (the majority) of jobs where stealth is not needed.


Perhaps a Hi (F-22)/ Mid (F-35)/ Low (Gripen) Mix

Of course, now that so many F-35s have been ordered, the competition is preaching the benefits of mixed/diverse fleets and Team F-35 is going on about the economies of scale. They have to, because the F-35 that rolls off the line today is extremely expensive.

However...

Aircraft manufacturing is an interesting business that is low-volume at best. The highest-rate aircraft lines in the world are almost an order of magnitude lower in rate than Lamborghini or RR Motors.

Aircraft are largely hand-assembled from parts that made in very similar ways from one aircraft to another and often come off the same supply chain. The key to reducing costs is keeping things simple, holding the parts count down, managing the supply chain well and keeping assembly efficient - but that means "lean" rather than a huge automated Toyota-type line.

In the olden days, too, keeping aircraft flying involved a big engineering infrastructure that you did not want to duplicate (by adding an extra type) unless you had to. Digital engineering data and parts tracking, and high-speed delivery, make that less of an issue. (There aren't many airlines any more that standardize on one manufacturer's jets.) So a mixed fleet may be less of a burden than it once was.

Courtney,
The F100 problem of stagnation and/or stall could be certainly related to nuances of a higher pressure ratio engine and not having the experience as to cause and what the fix ought to be. Keep in mind that GE had a very sound and well tested high pressure engine in the F101 with a good stall margin from which the F110 evolved. The material issue came along as the F100 morphed into higher thrust versions to match the thrust of the F110-100. This entailed using new materials and advanced casting processes such as DS (directionally solidified) and then SC (single crystal) in the production of turbine blades. GE was able to not launch into these advance processes and materials as early as P&W did and therefore had time to avoid some pitfalls P&W incurred. The F110-100 engine was unique in that engine power was controlled by measuring the actual temperature being experienced by the HPT blade, not EGT. If the temperature got too high, fuel flow was reduced accordingly.

LO,
Thanks for the "good material", it was an interesting read and history recall.
So was I and into the 90s.

Fast forward to the F135 engine on the F-35. P&W had good engine knowledge going in considering the real time experience gained on the F-22. I suspect that changes to save weight and other enhancement considerations have lead to the problem/problems currently being experienced on the F-35 engine. I can't help but think the fixes may not be so simple by the silence of the L-M normal propaganda as well as the DoD's silence.

Surely directionally solidified blades were not exactly new technology at that time? They were first used in 1969.

I'm not sure about unique. The RB199 first ran about seven years earlier and used optical pyrometers to read blade temps and to control fuel flow accordingly.

A hypothesis.

The F135 has no margin left, in fact the main point of the F136 was the performance margin for growth in the design. A weight increased on the F35 they increased thrust by thrust by pushing the engine to the limit - but the stealth design limits the heat absorption limits of the airframe so that it can't disperse any more, so the main engine components are running at or beyond design limits - and it looks like they can't take it.

Developments for the next generation engine might help - eventually - but only with a major slip and redesign/cost. In the short term the question is what level of heat/thrust is acceptable to maintain a minimum acceptable TBF.

IRRC the original Tornado F3 RB199 engines were having to be changed about every 70 hours till the Saudi funded replacement blades were fitted...

That is feasible. I remember that in 1987 on the lower thrust RB199 Mk101, the average time between HPT blade failure was 124 hours. The Mk 103 and Mk 104 produced more thrust (higher blade temp).

I can't remember when single crystal blades were introduced to the Mk103 and Mk104 engines but I know that they all had them by the start of GW1. They made a huge difference with 300 hours being easily reached. I found myself briefly back on Tornado a couple of years ago and some engines were managing 1000 hours.

Orac & TD...

Those observations correlate. Also consider that there have been known redesigns to various parts of the engine, that may have induced different loads and temps downstream.

Cross wind, wet runway trials
 

Looks like a B has done some cross wind and wet runway trials at Edwards AFB. Looks like a pretty good cross wind from the approach shots- a good amount of crabbing and it is interesting to watch the control surface movements.


The "bin lid" on top still looks so wrong....

Up to 120 knots? That really puts the R in RVL...