English Electric Canberra and Hawker hunter

[kengeorge]

Earlier on today I was perusing the Secret projects website and found this:

https://www.secretprojects.co.uk/threads/keeping-the-hunter-and-canberra-longer.35182/page-2

This led me to an idea, which is a dangerous thing to do at my age. So here's my idea, what engine(s) could replace the RR Avon in the Hunter and Canberra, with a timeframe of mid/late 1070's? I know the Avon has the following specs  Length: 3,200 mm (126 inches) Diameter: 910 mm (35.7 inches) Weight: 1,310 kg (2,890 lb. Power was between 7,350 lbf (32,700 N) to 12,690 lbf (56,400) dry.

I'll go further, the reason is, upgrading both aircraft with modernish avionics, new wing skins, the ability to carry an increased variety of ordnance, to provide cost-effective aircraft for friendly countries that couldn't afford the more expensive kit used by others, to counter Soviet influences

So what do you think of my idea and what are your opinions?

Over to you

Ken

[Old Wombat]

Mid/late 1070's?

You're looking at a horse for speed, or an ox for power, or a mule for reliability (although they can be twitchy on start-up).

[Jeffry Fontaine]

 J57 or the TF33 would be my guess for the American B-57 Canberra.  The main issue being where the engines are mounted limits rather quickly the size of the engine to replace the original engines.  For a British Canberra the same physical contraints would apply. 

[apophenia]

Something to keep in mind on Canberra re-engining options is that the Avons were mounted in front of the main spar. Aft of that spar is a simple jet pipe. That means that re-engining the Canberra with larger-diameter (compared with the original Avons) turbofans would be comparatively simple (as shown by Jeff's TF33 example from the RB-57F).

The obvious Avon replacement option would be the Rolls-Royce Spey. Putting out slightly more than the 7,400 lbf RA.7 Avon Mk109 turbojet would the civil RB.168 Mk 555 (9,850 lbf). But the USAF example shows that the airframe could absorb much more power.  This suggests that the military RB.168 Mk 250 (12,160 lbf) would be a better option - which also gives you engine commonality with the Nimrod MR.1.

[kengeorge]

Thank you for the replies, I'm thinking, purely academically, replacing the RR Avon 207 with the Avon 301 used by the  Lightning, as it has a bit more power. Ordnance wise, upgrading to Republic of Singapore Air Force standard, Six underwing pylons and a centreline pylon with a twin Bomb rack (2x500lb). Air-to-air, maybe Redtop or Firestreak AAM, as offering Sidewinders may cause an issue with US weapons being used by Goverments not that friendly to the US.

As For the Canberra, the Spey is a good call. However, as Avons are ahead of the forward main spar, would there be an issue in centre of gravity shifting rearwards? Would replacing the Canberra forward fuselage with a B-57 style FF counteract the CG problem?

[Jeffry Fontaine]

I have taken a look at my own Academy Hunter on several occasions to see what could be done with modifications.  One of the things that bugged me with the Hunter was the four gun arrangement inside the fuselage.  This got me to thinking that perhaps just two guns might be better and added on to the sides of the fuselage a little bit aft of the original gun pack location.  These gun pods would be sourced from the Hawker Harrier and if possible some of the Harrier stores pylons too since the Academy Hunter kit stores pylons are a bit generic in appearance and lack details you would expect on a modern aircraft. 

[apophenia]

Thank you for the replies, I'm thinking, purely academically, replacing the RR Avon 207 with the Avon 301 used by the  Lightning, as it has a bit more power...

The RA.29 Avon Mk 301 is fun idea but its reheat adds 225 kg (500 lbs) aft of the c/g. In any case, reheat is not all that practical as a retrofit for the Hunter airframe.

... Ordnance wise... Air-to-air, maybe Redtop or Firestreak AAM, as offering Sidewinders may cause an issue with US weapons being used by Goverments not that friendly to the US.

Few early AAMs were cheaper or lighter than the AIM-9B. But, being designed for a completely different role provides Firestreak or Red Top with advantages that are now largely forgotten. First is that they could slaved to radar for launch (unlike early-model Sidewinders). As a result, the British missiles "outperformed the US missiles in both maximum engagement angle and against supersonic targets." That was partly because Firestreak or Red Top were slightly more manoeuvrable than AIM-9B (15 G max overload vs 10 G).

The downsides were the sheer size of the British missiles ... although that provided them with space for much bigger warheads (22.7 kg warhead vs 4.5 kg). That size and warhead had also dictated by the anti-bomber role for Firestreak or Red Top.

As For the Canberra, the Spey is a good call. However, as Avons are ahead of the forward main spar, would there be an issue in centre of gravity shifting rearwards? Would replacing the Canberra forward fuselage with a B-57 style FF counteract the CG problem?

I don't think that any airframe changes would be required to maintain c/g. Like the TF33s, Speys would also be mounted forward of that spar. The Spey Mk.250 is only 128 kg (58 lbs) lighter than the original Avon 207. That slight difference could likely be accommodated simply by moving some equipment about.

[kengeorge]

My Hunter upgrade was to have a dry Avon 301, mainly because of fuel consumption issues, as the Hunter dosen't have a lot of internal fuel anyway, and airframe restrictions.

As for the Canberra, I nanaged to missunderstand what you meant when swapping out the Avon for the Spey, as for some reason I thought the Spey was going to fit between the spars, and not where the Avon was, ahead of the fwd spar. Must have been a senior moment for me!

Would there be an advantage offering the option to replace the Canberra Forward fuselage with the B-57 FF anyway as some Air Forces may prefer two pairs of eyes in the cockpit instead of one and the other in the 'coal hole' original?

[apophenia]

My Hunter upgrade was to have a dry Avon 301, mainly because of fuel consumption issues, as the Hunter dosen't have a lot of internal fuel anyway, and airframe restrictions...

Gotcha on the unreheated Avon 301 - my senior moment auto-inserted that R suffice 

When I prepared a Rolls-Royce 'RB' designation list for SPF, I came across mention of an RB.146. This was to be an improved-compressor Avon 300 series development producing 12,690 lbf. In a way, the RB.146 was a second kick at the can for the RB.106 'drop-in' Avon replacement project. Perhaps with a big enough market (ie: Lightning plus upgraded Hunters), the RB.146 project might have been resuscitated?

... As for the Canberra, I nanaged to missunderstand what you meant when swapping out the Avon for the Spey, as for some reason I thought the Spey was going to fit between the spars, and not where the Avon was, ahead of the fwd spar. Must have been a senior moment for me!

Would there be an advantage offering the option to replace the Canberra Forward fuselage with the B-57 FF anyway as some Air Forces may prefer two pairs of eyes in the cockpit instead of one and the other in the 'coal hole' original?

On the tandem cockpit idea: With the kit of the day, the WSOp was going to have his head down most of the time anyway. The big advantage would be that both crew have ejection seats. That 'both crew' is important, though. A key issue would be whether the RAF was willing to sacrifice the Canberra's third crew member.

[GTX_Admin]

Depending upon era, you might be able to fit a non-after burning GE F404-GE-100D instead of the Avon. 

[elmayerle]

If you are rebuilding the Hunter, how about incorporating the CFE's suggestion of a three-foot extension of the fuselage tank, moving the joint between the cockpit section and the center fuselage that much farther forward?  It would at least allow greater range.  For reengining the Hunter and staying within the max. envelope of the Avon, perhaps a P&W J52?  IF you didn't mind  a slightly larger envelope diameter, how about a dry J79?