Nimrod MR2 based on what?

[Shaggy Sheep Driver]

I always though it was the Comet 4 airframe that formed the basis of the Nimrod MR1 / 2. Today I found it was a Comet 4 wing on a 3 fuselage, which led to instability in pitch and yaw due relatively short fuselage moment arm for the wing. And it was made worse in yaw when the refueling probes were fitted, hence the tailplane mini-fins and ventral fin.

If that's true, why did they not use the '4' fuselage? And I understand that the instability was even worse on the MRA4 with its Airbus-designed wing and the original fuselage, but was corrected by the electronic flight control system.

[Allan Lupton]

Not really my subject, as a civil aeroplane man, but the Nimrod used the Comet 4C fuselage - or at least the first two development aeroplanes did, as they were the last 4Cs taken from the line for that purpose. I can't remember if all production Nimrods were 4C length.
The huge radome/bomb bay fairing below the fuselage (lost of side area right at the front) would seem to me to be the natural source of any yaw stability problems.
I would point out, when you refer to "Airbus-designed wings," that all the wings of Airbus types have their aerodynamic origins at Hatfield - the first were designed there and later types were designed by substantially the same team, relocated to Filton.

[Dash8driver1312]

Ref 'Nimrod Rise and Fall' by Tony Blackman, the problem was with the new keel area added by the lower fuselage lobe.

There was also an issue for in flight refuelling caused by the original aileron-rudder hearing carried over from the airliner and left unmodified in the Nimrod.

[Dash8driver1312]

Gearing*. iPhone spellchecking is never your friend...

[Shaggy Sheep Driver]

I think only the prototypes used 4C airframes, built from a couple of unsold Comets from Hawarden. The rest were built from scratch as MR1s at Woodford, the design being based on (if my info is correct) Comet 3 fuselages and Comet 4 wings?

[Jn14:6]

The Comet 3 and 4 had identical fuselage length, 33.98m. The 4B/C was 35.97m.
It was on the 4C that the Nimrod was based and had an overall length of 38.6m, the difference being accounted for by the lower fuselage extensions and the 'stinger.'

[Shaggy Sheep Driver]

So the info that they used a '3' fuselage design on a '4' wing is incorrect? The airframe used the 4C design entirely, with the pannier, nose, and MAD extensions?

[Allan Lupton]

Quote
So the info that they used a '3' fuselage design on a '4' wing is incorrect? The airframe used the 4C design entirely, with the pannier, nose, and MAD extensions?

Yes, whoever told you they used a Comet 3 hadn't thought his idea through:
a) aerodynamically the 3 and 4 were identical.
b) we only made the one 3 (06100/G-ANLO) and that was some 15 years earlier
c) however, as I just found, when the 3 was broken up its fuselage was used as part of a Nimrod mock-up at Woodford, so that'll be what started this hare.

[WH904]

I'm confused now (as usual):)
As I understood it, the Nimrod fuselage is shorter than the Comet 4C ?

[mickq]

I did the stressing on the fuselage of the first 'converted' Comet. Although my memory fades somewhat it was a lengthy Comet already manufactured (4C?) that we shortened. I remember that the skins didn't overlap and was a clean circumferential joint. This had some of us in the Stress Office a little concerned.
mickq

[PEI_3721]

http://tinypic.com/view.php?pic=33jp7jq&s=5#.UpTNvOI8Gpo
http://i43.tinypic.com/33jp7jq.jpg
MR2 fuselages at Woodford (with sibling), awaiting MR4 status.

Allan, the MR4 flight deck mock-up which I saw was at Warton, and IIRC was based on ‘147’ (ex Woodford). This forward fuselage generated many problems (unknown at the time) for the MR4 as the original ‘Comet’ / Nimrod was built by hand, and the nose section fettled +- ¼ inch. Thus when the MR4 avionics were fitted – they didn’t, because the 1thou precision of CAD was unaware of the actual dimensions.

[Shaggy Sheep Driver]

Bill Gunston's book says Nimrod's was a 4C airframe, but 6 feet was deleted from the fuselage forward of the wing. One wonders why.

This would fit mickq's memory of shortening the 4C fuselage for the 2 prototypes (which were converted Comet 4Cs, whereas production Nimrods were built from scratch as Nimrods to the 4C design less 6 feet of fuselage). But if anything, that would improve the directional and yaw stability, surely?

[GOLF_BRAVO_ZULU]

The rest were built from scratch as MR1s at Woodford

A minor correction; they were built at Hawarden on the original Comet 4 jigs, except the tailplanes and engine intakes that were similarly built at Hatfield. They were transported to and assembled at Woodford with Nimrod unique parts (eg the panniers) supplied from Chadderon.

[Shaggy Sheep Driver]

Interesting. How did they transport the partially-completed airframes (winged fuselages) from Hawarden to Woodford?

At least one book (Gunson's or Blackman's?) says the Comet jigs were moved from Hatfield and Hawarden to Woodford.

[GOLF_BRAVO_ZULU]

The mainplanes and fuselages (including the centre section) were moved seperately on low loaders. On my way to Gliding School at Sealand on Sundays in the mid-late '60s, it was normal to see a Nimrod fuselage travelling along the A556 in the opposite direction as a "wide load". I never saw mainplanes as they must have moved at different times/days.

Moving the jigs and building the big bits at Chadderon would have been interesting as DH built aeroplanes differently to AVRO. Chadderton made great use of Fairey envelope jigs but I believe that they were alien to Hatfield and Hawarden.

[spekesoftly]

How did they transport the partially-completed airframes (winged fuselages) from Hawarden to Woodford?If you scroll down the following link there are several photos of Nimrod fuselages being transported from Hawarden to Woodford:-

The TruckNet UK Drivers RoundTable ? View topic - British Aerospace - Chester (http://www.trucknetuk.com/phpBB/viewtopic.php?f=35&t=34917&p=534989)

[Shaggy Sheep Driver]

Fantastic! Thanks very much for those pictures.

[Groundloop]

Bill Gunston's book says Nimrod's was a 4C airframe, but 6 feet was deleted from the fuselage forward of the wing. One wonders why.

Virtually reduces the fuselage from a 4C to a 4!!