BAe Systems Nimrod MRA.4 (Nimrod 2000)

[Hobbes]

The normal problem is not with pitch, but with yaw in the case of the failure of an outboard engine on take off and therefore at max thrust The one good feature of Nimrod/Comet engine architecture was a nice small (low parasitc drag) fin.

True, but look at the 737 MAX and its pitch problem due to its lower thrust line...

 

[red admiral]

The one good feature of Nimrod/Comet engine architecture was a nice small (low parasitc drag) fin.

Which was still small in the much bigger and heavier MRA4, resulting in a need for a completely new fly by wire FCS.... Which is almost never mentioned but took significant resources and time

 

[taildragger]

The normal problem is not with pitch, but with yaw in the case of the failure of an outboard engine on take off and therefore at max thrust The one good feature of Nimrod/Comet engine architecture was a nice small (low parasitc drag) fin.

True, but look at the 737 MAX and its pitch problem due to its lower thrust line...

I believe that the MCAS system, the apparent source of the 737s troubles, was added due to aerodynamic lift produced by the larger nacelle's at high AOA. This caused non-linear stick forces which is frowned on by the certification rules and threatened to increase the training requirement for pilots transitioning from earlier models of 737, threatening the airplane's economic case. I don't think the different thrust line is a factor.

 

[Hood]

Maybe look back at the thinking behind the MRA.4? Pure parochial politics. Why take a 40 (50?) year-old design and update it? B-52 - hang new turbofans on it. C-130 - stick new turboprops on it. Ditto P-7. P-8 - mate wings and modded fuselage of same basic aircraft. None required the complete redesign of the engine installation and wing. The MRA. 4 sounded great on paper but like many aerospace projects nobody said 'Stop this nonsense' until it was too late.

Are we turning this beast into a millennial TSR. 2?

It just seems easier to tinker with what you've got rather than going to the effort and expense of starting from a fresh basis. In reality it is a false economy and intellectual laziness, but for the bean counters and salesmen its an easier job to make and sell a well known brand. The Hercules, Chinook, Apache, F/A-18, F-16, F-15, B-52, 737, even the A320 too (I would add the MiG-29 and Su-27 to this list too, but their rejuvenation is slowing down), are all good examples of continual resuscitation that still outlive any attempts to replace them. One wonders when, if ever, they will finally die out? Even in 2050 the odds are that a quarter of my listing will still be in production in some form, somewhere.

And yes, MRA.4 is the TSR.2 of our times. This thread has been the most informative and useful on that programme I think I have ever read with some very interesting insights.

 

[galgot]

why did it need four engines anyway (rhetorical question, but I'm interested in the answers)

At the time the RAF didn’t believe in ETOP’s, there were too many horror stories of Nimrod’s limping back hundreds of miles with engines taken out by bird strikes and the south Atlantic is a very unforgiving place to be a long way from home flying a single.

I see their point as the basic ETOPs safety case doesn’t have a bird strike risk and has minimal change in engine thrust, it’s a very constant environment unlike low level.

I can see the advantage of the Kawasaki P-1 then.
How do they manage that with the P-8 now ? Have they made the engines much more resistant to bird strikes ?

 

[Zoo Tycoon]

why did it need four engines anyway (rhetorical question, but I'm interested in the answers)

At the time the RAF didn’t believe in ETOP’s, there were too many horror stories of Nimrod’s limping back hundreds of miles with engines taken out by bird strikes and the south Atlantic is a very unforgiving place to be a long way from home flying a single.

I see their point as the basic ETOPs safety case doesn’t have a bird strike risk and has minimal change in engine thrust, it’s a very constant environment unlike low level.

I can see the advantage of the Kawasaki P-1 then.
How do they manage that with the P-8 now ? Have they made the engines much more resistant to bird strikes ?

I understand that the P8 has done quite a bit on the systems side to enable more medium altitude operations, in particular with regards to accuracy for sonobuoy placement from higher altitude and data links. On all the USN aircraft there’s no MAD which is low altitude for only system, (yes I know it’s an option ) again to keep em high.

 

[Grey Havoc]

The P-8 is also supposed to be able to deploy and/or use drones that operate at lower altitudes which are equipped with MAD & other sensors. The idea hasn't worked out that well in practice so far though.

 

[exkiwiforces]

Thanks for a very interesting thread and I’ve learnt a few things about MR4 so far. As I was always been led to believe that wings couldn’t match up with the fuselage as the fuselage was hand built.

Again many thanks and I look forward to the next post on the sorry saga of MR4 project.

 

[CJGibson]

Engine or engines?

Chris

 

[CJGibson]

Just noticed this.

The MRA.4 was fly-by-wire?

Chris

 

[FighterJock]

Just noticed this.

The MRA.4 was fly-by-wire?

Chris

That is the first time that I have heard that the Nimrod MRA.4 was fly-by-wire. Maybe that explains how the MRA.4 went over budget in the first place.

 

[Zoo Tycoon]

No it was controlled with tug by cable, with the exception of the rudder which was tug by cable plus a bit of electrickery to make sure the pilot got what he really wanted.

In the very early days we wanted fly by wire ailerons but the customer firmly rejected this saying it was too complicated/expensive. However given the roll control problems experience during flight testing, history proved that tug by cables was far more expensive........it took about 4 years to sort that which added 2 plus a bit years to the overall project delay.

 

[CJGibson]

Interesting, state of the art 1940s fly-by-cable. FBW would quite possibly have saved it. Anyway, back to the engines. I asked 'engine or engines' because I'm curious about incidences of post-birdstrike of contagious failure.

Chris

 

[Forest Green]

One story I heard about the reasons for the cost overruns was that BAE Systems was very proud of their advanced production methods ensuring precision and uniformity of parts... only to discover that each airframe had been virtually built by hand and therefore no two were exactly alike, or at least the differences were far outside their tolerances. Is this true?

Completely true. Basically, they tried cut costs by reusing MR.2 fuselages and ironically it was that which made the project more expensive than developing a stealth bomber from scratch because of all the problems it introduced.

 

[Forest Green]

At the beginning of Nimrod 2000 we were well aware of this. Indeed in the latter part of 1996 I was involved in a fleet measuring survey (using Portable Ziess laser measuring equipment) to validate the original build records. The often reported stories of discovery mid project, this causing the wings not to fit, and leading to the years of delay are utter nonsense.

Errr... what? I was on the project. They built sets of wings that didn't fit at all. The fuselages were completely the problem. Even after the problem with the wings, they had to introduce SAS and SIDD systems just to make the damn thing fly straight rather than wobbling through the air like a banana going down the rapids. Then the IFR probe was flagged up as a problem following an incident in Afghanistan. A myriad of issues all stemming from using existing fuselages rather than just going for a new build.

Some fuselages were round, some were elliptical, some egg-shaped and some banana-shaped. This meant that basically every MRA.4 built was a different aircraft apart from the on-board systems.

 

[Forest Green]

Just noticed this.

The MRA.4 was fly-by-wire?

Chris

Had to be. Damn thing would dutch roll and generally fly like a banana without it. A new aircraft design would have cost less. What they tried was akin to attempting to develop a 1960s Ford Anglia into a modern rally car. Much easier to start from scratch.

 

[red admiral]

Just noticed this.

The MRA.4 was fly-by-wire?

Chris

Pretty sure it was in the end. I used to work with one of the ex-BAES flight control engineers who left when it was cancelled. Apparently needed fbw to fly safely. And the finlets on the tailplane

 

[zebedee]

Might as well drop these here as its as good a place as any. Some photos I took of the MRA4 Flight Dynamics Assessment Rig in 2012. Based on an unknown Comet/Nimrod nose* it was gifted to a North West University's Engineering Department for flight simulator development work. They did eventually get it to work, however it's now being converted into a 737 sim as they can't dispose of it due to "contractural issues". The MRA4 equipment is being saved should it be decided to rebuild it at a later date...

Zeb

*This has been the subject of great debate on a number of forums with suggestions ranging from XV147, XV263, a former Farnborough water tank airframe (6402) or an ex Singer Link Miles AEW3 Simulator...

 

[Zoo Tycoon]

Oh

Just noticed this.

The MRA.4 was fly-by-wire?

Chris

Pretty sure it was in the end. I used to work with one of the ex-BAES flight control engineers who left when it was cancelled. Apparently needed fbw to fly safely. And the finlets on the tailplane

Oh no it wasn’t

 

[Zoo Tycoon]

So

At the beginning of Nimrod 2000 we were well aware of this. Indeed in the latter part of 1996 I was involved in a fleet measuring survey (using Portable Ziess laser measuring equipment) to validate the original build records. The often reported stories of discovery mid project, this causing the wings not to fit, and leading to the years of delay are utter nonsense.

Errr... what? I was on the project. They built sets of wings that didn't fit at all. The fuselages were completely the problem. Even after the problem with the wings, they had to introduce SAS and SIDD systems just to make the damn thing fly straight rather than wobbling through the air like a banana going down the rapids. Then the IFR probe was flagged up as a problem following an incident in Afghanistan. A myriad of issues all stemming from using existing fuselages rather than just going for a new build.

Some fuselages were round, some were elliptical, some egg-shaped and some banana-shaped. This meant that basically every MRA.4 built was a different aircraft apart from the on-board systems.

So tell me which one of the eight wing to fuselage attachments didn’t fit ? Not what I remember, did you actually attend any of the fuselage to wing join ups ? I did

Any one connected to the project would know it was not a fly by wire control system.

 

[Mike Pryce]

Just noticed this.

The MRA.4 was fly-by-wire?

Chris

Pretty sure it was in the end. I used to work with one of the ex-BAES flight control engineers who left when it was cancelled. Apparently needed fbw to fly safely. And the finlets on the tailplane

David Craddock

craddock.it

 

[zebedee]

This might also be of interest...

Flight Testing the Nimrod MRA4 - Andrew Gill / Alex Bellamy

Zeb

 

[Mike Pryce]

At the beginning of Nimrod 2000 we were well aware of this. Indeed in the latter part of 1996 I was involved in a fleet measuring survey (using Portable Ziess laser measuring equipment) to validate the original build records. The often reported stories of discovery mid project, this causing the wings not to fit, and leading to the years of delay are utter nonsense.

Errr... what? I was on the project. They built sets of wings that didn't fit at all. The fuselages were completely the problem. Even after the problem with the wings, they had to introduce SAS and SIDD systems just to make the damn thing fly straight rather than wobbling through the air like a banana going down the rapids. Then the IFR probe was flagged up as a problem following an incident in Afghanistan. A myriad of issues all stemming from using existing fuselages rather than just going for a new build.

Some fuselages were round, some were elliptical, some egg-shaped and some banana-shaped. This meant that basically every MRA.4 built was a different aircraft apart from the on-board systems.

As I heard it, the pressurised part of the fuselage was the key component in certification for considering it a Nimrod variant rather than a new aeroplane.

 

[Zoo Tycoon]

Ah no, the pressure floor (catenary floor) was not part of wing attachment;- it bridged across the two major frames which where wing pick up points. The catenary floor was a new build component, made at Preswick. It’s manufacturing problems where the redux gaps whereby the modern methods couldn’t achieve the original drawing dimensions.

 

[Zoo Tycoon]

Just noticed this.

The MRA.4 was fly-by-wire?

Chris

Pretty sure it was in the end. I used to work with one of the ex-BAES flight control engineers who left when it was cancelled. Apparently needed fbw to fly safely. And the finlets on the tailplane

David Craddock

craddock.it

A stability augmentation system is not fly by wire;- 737’s MCAS provides a function of applying an extra tug on its cables at an opportune time determined by a computer but this doesn’t make 737 fly by wire.

 

[Mike Pryce]

At least on Nimrod the SAS was recognised as safety critical and made quadruplex. On the MAX they seem to have made a full authority system simplex.

 

[Mike Pryce]

Ah no, the pressure floor (catenary floor) was not part of wing attachment;- it bridged across the two major frames which where wing pick up points. The catenary floor was a new build component, made at Preswick. It’s manufacturing problems where the redux gaps whereby the modern methods couldn’t achieve the original drawing dimensions.

But I think the main fuselage 'tube' needed to be kept.

 

[Rickshaw]

I wonder why there is no good 3 view drawings of the MR4?

 

[Caravellarella]

I wonder why there is no good 3 view drawings of the MR4?

Could it be; the whole sorry affair is too embarrassing? Another source of national shame; best to be forgotten?

Terry (Caravellarella)

 

[Hobbes]

I don't know how good they are (but I'm working on that), but there are 3-views in the brochure and leaflets linked at the start of this topic.

 

[PMN1]

I wonder why there is no good 3 view drawings of the MR4?

Could it be; the whole sorry affair is too embarrassing? Another source of national shame; best to be forgotten?

Terry (Caravellarella)

Well the airframes were cut up with embarrassing/amazing haste behind screens.......

 

[Hood]

The fuselages were completely the problem. Even after the problem with the wings, they had to introduce SAS and SIDD systems just to make the damn thing fly straight rather than wobbling through the air like a banana going down the rapids. Then the IFR probe was flagged up as a problem following an incident in Afghanistan. A myriad of issues all stemming from using existing fuselages rather than just going for a new build.

Some fuselages were round, some were elliptical, some egg-shaped and some banana-shaped. This meant that basically every MRA.4 built was a different aircraft apart from the on-board systems.

I find it hard to believe that the Nimrod fuselages had deteriorated to such an extent that they had become banana-shaped and nobody had noticed.

As far I as I understand it, the pressurised fuselage was made up of more or less standard Comet 4 fuselage sections and that most of the major changes were the unpressurised fairing for the radar, weapon bays etc. and the tail around the MAD etc. Although assembled at Woodford, the fuselage sub-sections were built on the normal Comet line at Chester (as was the wing centre section and they also gained the outer wing production line from Portsmouth), with Chadderton only manufacturing those structural items specially modified or designed for Nimrod. In fact at the time of the Nimrod 2000 bid, BAe were confident the Nimrod was a good choice for upgrading was because the airframes had been supported by Chadderton throughout their lives and that it was, quoting Graham Chisnall, the Nimrod 2000 project manger back in 1996 "probably the best-understood airframe in the RAF inventory."
Source: https://www.flightglobal.com/news/articles/something-old-something-new-something-borrowed-17019/

 

[alertken]

Posts raise 3 history issues, 2 mischieviously by CJG whose Nimrod's Genesis covers much.
Q1. Why did UK choose a 4xengined type in 1965? A1: to rule out the NBMR.2 winner, Avro-involved Breguet Atlantic. There were 49 NBMRs: UK took none.
USN too rejected Atlantic for a 4some. Their "need" for reliable power on long overwater sorties was risible: USN/RAF/FN et al flew Lockheed P2V Neptune wet and wide; longest WW2 endurance-type was Catalina. Atlantic happily served R.Neth.AF/Antilles, France/Caribbean/Nouméa.

Q2. In 1965 why turbofans, when turboprops then had more range. A2: to disqualify P-3 Orion. UK was discussing a massive US package (F-4M/C-130K/F-111K/helis/more). Some jobs at home, please! HS Group Chairman Sir Roy Dobson, balancing his runners - an MR Trident (see: > 2 motors), or an MR Comet 4, contemplated Ministers' wish for a real, not gossamer fixed price, R&D+Production. RR would do that for Spey in either berth: he decided HSAL's risk would be less on Comet base, so that was bid more compliant with MoA's tender terms. No brainer.

Q3. Why a Nimrod base for MRA4. (Start with: Q: why a Nimrod base, 31/3/77 for AEW? A; No brainer: part-built, unwanted East of Suez MR1 airframes, noble work for GEC/BAe, or $ to Boeing:
“in the light (of) continued uncertainty about (NATO AWACS) procurement (UK) decided that we must now go ahead” solo-UK, not wait for E-3). Well, again, Ministers spent much effort trying to do a multi-national solution for MR-2000, and just lost patience against a BAE proposition to retread MR2s, "fixed price", 12/96. No brainer.

Much examination here of structure, but project failure was due to conflict BAE:GEC until "merger", 11/99. As early as 2/97 Boeing's (to be P-8) TCS was chosen by Ministers vice GEC-Marconi suite, thus destroying the "fixed" price.

Lynx as Wildcat...why, I hear you cry, do Ministers keep falling for "simple, cheap, quick retread"? Because that can occasionally happen: This Board oft bewails demise of P.1121, but surely we applaud taking (half-US-subsidised, low-hours) Hunter F.6 and deploying them as FGA.9/FR.10. ex-RAF jungly Merlins. It can work.

 

[Forest Green]

I find it hard to believe that the Nimrod fuselages had deteriorated to such an extent that they had become banana-shaped and nobody had noticed.

As far I as I understand it, the pressurised fuselage was made up of more or less standard Comet 4 fuselage sections and that most of the major changes were the unpressurised fairing for the radar, weapon bays etc. and the tail around the MAD etc. Although assembled at Woodford, the fuselage sub-sections were built on the normal Comet line at Chester (as was the wing centre section and they also gained the outer wing production line from Portsmouth), with Chadderton only manufacturing those structural items specially modified or designed for Nimrod. In fact at the time of the Nimrod 2000 bid, BAe were confident the Nimrod was a good choice for upgrading was because the airframes had been supported by Chadderton throughout their lives and that it was, quoting Graham Chisnall, the Nimrod 2000 project manger back in 1996 "probably the best-understood airframe in the RAF inventory."
Source: https://www.flightglobal.com/news/articles/something-old-something-new-something-borrowed-17019/

I don't know whether they got that way or were built that way but they were not even close to being identical, except when observed from a distance of say 100m. I spoke with a lot of people who'd been on the project from the get-go while I worked on the training system, and the description I got was that some fuselage cross-sections were circular, some were elliptical, some egg-shaped and some of the fuselages were banana-shaped along their length. A brand new aircraft would have solved 90% of the problems encountered. Even after fit was achieved, the aircraft needed stability augmentation systems to prevent pitching and rolling.

 

[Forest Green]

So tell me which one of the eight wing to fuselage attachments didn’t fit ? Not what I remember, did you actually attend any of the fuselage to wing join ups ? I did

Any one connected to the project would know it was not a fly by wire control system.

I worked on the Training System from 2005-2010 at Warton, so whilst I didn't attend directly, I spoke with people who'd been on the project long-term. Depends on the exact definition of FBW, it very definitely was not flown by just by cable, or else what were SAS and SIDD please tell me? The crew would have got sea sick without those systems. So whilst a car may steer by steering rack and throttle cable, there are traction control, ABS and stability control programs smoothing things out. The only difference is that a car only needs those systems 1-5% of the time, the MRA4 needed them all the time.

 

[alertken]

Peas-in-pod. Few aircraft were, pre-CAD/CAM. VC10: weight would be “30% less if designed (now, builders) appear to have adhered only loosely to the drawings (New) parts must be machined to match the unserviceable part” O/C,VC10 Major Svcg.,RAF St.Athan,P63, 3/99 ,Overhaul&Maintenance magazine. Sculpture was not a purely UK art form. Philippine A/L put 5 DC-8/53 into HKG, 1979 to fit Heath Tecna overhead bins, vice hatracks. None, I say, none of the standard kits fitted. Each fuselage was distinctive (though not by a foot!).

 

[Zoo Tycoon]

At the beginning of Nimrod 2000 we were well aware of this. Indeed in the latter part of 1996 I was involved in a fleet measuring survey (using Portable Ziess laser measuring equipment) to validate the original build records. The often reported stories of discovery mid project, this causing the wings not to fit, and leading to the years of delay are utter nonsense.

Errr... what? I was on the project. They built sets of wings that didn't fit at all. The fuselages were completely the problem. Even after the problem with the wings, they had to introduce SAS and SIDD systems just to make the damn thing fly straight rather than wobbling through the air like a banana going down the rapids. Then the IFR probe was flagged up as a problem following an incident in Afghanistan. A myriad of issues all stemming from using existing fuselages rather than just going for a new build.

Some fuselages were round, some were elliptical, some egg-shaped and some banana-shaped. This meant that basically every MRA.4 built was a different aircraft apart from the on-board systems.

As I heard it, the pressurised part of the fuselage was the key component in certification for considering it a Nimrod variant rather than a new aeroplane.

Ah no, the pressure floor (catenary floor) was not part of wing attachment;- it bridged across the two major frames which where wing pick up points. The catenary floor was a new build component, made at Preswick. It’s manufacturing problems where the redux gaps whereby the modern methods couldn’t achieve the original drawing dimensions.

But I think the main fuselage 'tube' needed to be kept.

The catenary floor was integral to the fuselage. They were found to be damaged, I think from activity from the top, so were replaced as part of the overhaul. Being cyclic pressure loaded its particularly sensitive to/intolerant of damage.

About the only original bits of Nimrod MR2 were the fuselage tubes and tank 4a’s. I remember we tried to retain parts from the control system, but one by one it was realised they couldn’t be be used. Finally there was just one piece left. During PA1 build I got a call telling me this last remaining part had been trail installed but failed it’s dynamic clearance check with another new designed part from the primary flight controls (it didn’t foul just a clearance infringement). So the last retained component part from MR2 was reluctantly replaced by a new designed component.

 

[Zoo Tycoon]

So tell me which one of the eight wing to fuselage attachments didn’t fit ? Not what I remember, did you actually attend any of the fuselage to wing join ups ? I did

Any one connected to the project would know it was not a fly by wire control system.

I worked on the Training System from 2005-2010 at Warton, so whilst I didn't attend directly, I spoke with people who'd been on the project long-term. Depends on the exact definition of FBW, it very definitely was not flown by just by cable, or else what were SAS and SIDD please tell me? The crew would have got sea sick without those systems. So whilst a car may steer by steering rack and throttle cable, there are traction control, ABS and stability control programs smoothing things out. The only difference is that a car only needs those systems 1-5% of the time, the MRA4 needed them all the time.

Inaccurate stories were everywhere, even by those working on the project, as I’ve said before I can only tell you what I witnessed.

I’ve never denied the existence of the SAS/SIDD, indeed if you read my posts I’ve made reference to it but it’s not fly by wire. The cable/pulley/servodyne aileron circuit was designed/built/flight tested three times before before they got something acceptable in terms of pilot control force. Each design cycle entails requalification and repeat test flying it amounted to three plus years of program slip. FBW ailerons would have allowed software adjustments and almost certainly saved most if not all of this time.

The RAF and MOD specifically didn’t want FBW as they considered it too complicated/expensive (I remember the meeting where they told us exactly this) . But BAe didn’t have anyone with ground up experience of designing a tug by wire system and it’s no where near as easy as most keyboard experts would believe.

 

[Forest Green]

Inaccurate stories were everywhere, even by those working on the project, as I’ve said before I can only tell you what I witnessed.

I’ve never denied the existence of the SAS/SIDD, indeed if you read my posts I’ve made reference to it but it’s not fly by wire. The cable/pulley/servodyne aileron circuit was designed/built/flight tested three times before before they got something acceptable in terms of pilot control force. Each design cycle entails requalification and repeat test flying it amounted to three plus years of program slip. FBW ailerons would have allowed software adjustments and almost certainly saved most if not all of this time.

The RAF and MOD specifically didn’t want FBW as they considered it too complicated/expensive (I remember the meeting where they told us exactly this) . But BAe didn’t have anyone with ground up experience of designing a tug by wire system and it’s no where near as easy as most keyboard experts would believe.

The people I heard it from had been working change control on the project from day 1, so they would have known what changes went through and why they went through. With an ISO 9001 accredited configuration control system you'd can't just make a change to the design and say, "done." A change request has to be submitted for approval and that change request has to have a reason and a pretty substantial one if it's going to cost a shed load and cause a huge delay. There is even a category system for change requests, and the more expensive the change, the higher up it goes. So it's not like a few guys in a hangar would have been the only ones aware.

I realise what you're saying about FBW but I still stand by the point that it isn't completely cable-driven if two software/electronic systems have to basically unscrew everything after each stick and cable input. FBW probably would have been easier, but then so would building a completely new air frame, or even basing it on an Airbus or something, just anything but a 1950's Comet basically.

 

[CJGibson]

Scarper CJ! You've been rumbled!

Ken, would you include the Puma HC.2 in your success list?

Chris