Jet Lancaster range?

[Admiral Beez]

Is that why the B-36 used a combination of propellor and jet engines?
My dad was in the USAF during those years and he said that B-36 pilots would often cut the prop engines and coast on the jets alone, once they reached altitude.
It was a fuel saving strategy.

That was my thinking. Though the B-36 used turbo props and jets, so the same fuel could be used. Our hybrid Lancaster/Lincoln would need to carry two fuels.

edit… my bad, the B-36 was Wasp powered, so also dual fuel.

 

[z42]

Seems like the hypothetical jet Lancaster would need a redesign of the undercarriage. The Merlin Lancaster had the main gears in the inner nacelles, behind the engines. Doesn't work for a jet, obviously. Secondly IIRC the early tail dragger prototype of the Me 262 had issues with melting the tarmac. So you probably want a tricycle gear designed from scratch.

All in all, I think we're getting close to the point where a from scratch design is less work..

Hurrying up the Canberra project was probably the best way forward they had for getting a jet bomber ASAP.

 

[Shortround6]

I've been reading Stanley Hooker's "Not much of an Engineer" & he describes tests with a Lancaster converted to run with two turbojets in place of two of the Merlins. Calculations showed a 4 jet version would have a speed in excess of 400mph at 30,000ft with a full bombload making it 'essentially uninterceptable'. Great and all but there's no mention of range.........

Sure, there's a lot to be said about the plausibility (or otherwise) of the hypothetical scenario - but would anyone care to take a guess at a 4 jet Lancasters combat radius in say 1944-45?

A few Lancaster's and more than the few Lancastrians were used as testbeds, but just about all of them flew after WW II. They also flew with a wide variety of engines.
Derwents may not have been one of them.

VH742 didn't fly until Aug 1946 and used Nene engines.
The Nene was a 5000lb thrust engine and at full power (sea level) burned 1.05lbs/lb. thust/hr.
They first started a Nene engine on Oct 27th 1944.
Nene was about 1600lb engine and was 49.5in Dia.

You might get a 400mph "Lancaster" It might also burn around 2000lbs of fuel per engine in cruise at altitude (8000lbs per hour).
As far as getting off the ground?
In the initial planning stages they were thinking about fitting rocket engines to the DH Comet airliner to get it off the ground because of the poor take-off capabilities of the engines being planed for use. Engines got a lot better in just a few years in late 1940s and they were able to ditch the rocket booster.

Other Lancastrians flew with DH ghosts, RR Avons, Bristol Saphires and several turbo-props.

 

[don4331]

Is that why the B-36 used a combination of propellor and jet engines?
My dad was in the USAF during those years and he said that B-36 pilots would often cut the prop engines and coast on the jets alone, once they reached altitude.
It was a fuel saving strategy.

B-36 cut prop engines as the big cigar would cruise on just a couple Wasps. (which says a lot about the efficiency of the airframe.

Note: Jets were just used for takeoff and for the dash over target. The rest of the time, the jets were shutdown as they were too inefficient to run. Early jets had great power to weight, atrocious fuel economy.

 

[don4331]

Seems like the hypothetical jet Lancaster would need a redesign of the undercarriage. The Merlin Lancaster had the main gears in the inner nacelles, behind the engines. Doesn't work for a jet, obviously. Secondly IIRC the early tail dragger prototype of the Me 262 had issues with melting the tarmac. So you probably want a tricycle gear designed from scratch.

All in all, I think we're getting close to the point where a from scratch design is less work..

Hurrying up the Canberra project was probably the best way forward they had for getting a jet bomber ASAP.

The melting the tarmac is a minor problem - the issue is no airflow over the horizontal stabilizer/elevators. see post 31 in thread

Me.262 had to accelerate down runway until it got to >100km/h, then pilot had to slam on the brakes to pop the tail up (without hitting them so hard that the plane nosed over) to get elevators to function. After which the jet would lift off runway. It wasn't discovered initially as 1st planes had a Jumo 210 in nose (Jumo jets were so unreliable at the time, that an ICE instead of armament was prudent) Galland commented that the slow acceleration to relatively high speed with tail down (very high risk of ground loop), then braking to lift the tail was altogether too exciting.

Yes. a tricycle gear design is a requirement for a jet Lancaster. My assumption - when you designed the tricycle gear, you resolved the issue with main gear in inner nacelle.

 

[EwenS]

Avro's Postwar design evolution can be seen with the Tudor airliner. Tudor began as a tail dragger powered by 4 Merlins. Tudor 8 (a single converted Tudor 1) was re-engined with 4 RR Nene engines in twin nacelles. Then the tricycle Tudor 9 was developed as the Ashton.

Tudor 2

Tudor 8

And finally the Ashton

 

[Admiral Beez]

B-36 cut prop engines as the big cigar would cruise on just a couple Wasps. (which says a lot about the efficiency of the airframe.

Note: Jets were just used for takeoff and for the dash over target. The rest of the time, the jets were shutdown as they were too inefficient to run. Early jets had great power to weight, atrocious fuel economy.

So, swap out the four Merlins for a pair Griffons driving five blade contra rotating props and a pair of jets.

 

[Shortround6]

So, swap out the four Merlins for a pair Griffons driving five blade contra rotating props and a pair of jets.

Doesn't do what you want it to do.

When you are building bombers you need a lot of cruising power or long term power, not 5 -15 minute "sprint' ratings.
And cruise power for range means maximum lean power, nor maximum rich cruise power or combat power.

Griffons tended only give about 100-150hp more in lean cruise than the Merlin did.
What you can do on maritime patrol vs what you can do over hundreds of miles of hostile land mass are rather different things.

In WW II your jet engines didn't provide enough power to swap them for the extra two Merlins.
The first production Meteors used Welland engines of 1600lbs thrust, after the first 15 Meteor 3s they got 2000lb thrust Derwent Is.
The 3500lb Derent 5s (scaled down Nene) started going into the Meteor IVs.

Now as a very crude estimation of what could have been expected we can look at the Avro Canada C.102 airliner.

First flight was in Aug 1949.

From Wiki.

• Capacity: payload 12,700 lb (5,761 kg)[16]
• Length: 82 ft 5 in (25.12 m)
• Wingspan: 98 ft 1 in (29.90 m)
• Wing area: 1,097 sq ft (101.9 m2)
• Empty weight: 27,427 lb (12,441 kg)
• Gross weight: 55,000 lb (24,948 kg)
• Powerplant: 4 × Rolls-Royce Derwent V centrifugal-flow turbojet engines, 3,600 lbf (16 kN) thrust each (later fitted with 2x Derwent 8 {#2 & #4} and 2x Derwent 9 engines {#1 & #3})

Performance

• Maximum speed: 417 mph (671 km/h, 362 kn) at 30,000 ft (9,100 m)
• Cruise speed: 376 mph (605 km/h, 327 kn) at 30,000 ft (9,100 m)
• Range: 1,680 mi (2,700 km, 1,460 nmi)
• Service ceiling: 40,300 ft (12,300 m)

Another old book gives somewhat different figures but then we start getting into actual aircraft and "planned/later development".
Normal fuel may have been 2,352 imp gal. and normal range 1250 miles, speeds are a bit different.

But in WW II or even 1946 you don't have the Derwent 5 engines. You have roughly 2000lb thrust engines and corresponding lower powers at 30,000ft.

 

[MiTasol]

I've been reading Stanley Hooker's "Not much of an Engineer" & he describes tests with a Lancaster converted to run with two turbojets in place of two of the Merlins. Calculations showed a 4 jet version would have a speed in excess of 400mph at 30,000ft with a full bombload making it 'essentially uninterceptable'. Great and all but there's no mention of range. AIUI they were facing increasing problems with German Nightfighters late-war. I recall a discussion in another forum years back with someone who might have been uncharitably called a 'wheraboo' who argued that in a straight Britain vs Germany drawn out fight (the scenario given was Khalkin-Gol erupts into a Soviet-Japanese war resulting in no Pearl Harbour, Hitler dies accidentally & Goering thinks it better to try a Mediterranean strategy than Barbarossa. Britain is left with Lend-Lease, but not enough U.S divisions onside to try Sicily or D-Day) the Germans would have ultimately been able to stop Bomber Command & so win.

Sure, there's a lot to be said about the plausibility (or otherwise) of the hypothetical scenario - but would anyone care to take a guess at a 4 jet Lancasters combat radius in say 1944-45?

I just realised the highlighted quote is actually rather ambiguous.

It could mean 4 jets and no Merlins, as we have been discussing, or it could mean a 4 jet version of Shortround's post 43 layout, retaining the inboard Merlins.

The latter would gain a lot in takeoff performance over a jet only version, solve the landing gear retracting into the nacelle problem and allow the aircraft to return home over friendly territory using just the Merlins which would extend the range. I expect the Merlins would have needed to been shut down and feathered at high speed. Unless they could produce a very wide range variable pitch prop the Merlins would be driven by the props and would create a lot of drag and probably serious engine overspeeds.

Remember also a lot of early jets ran on avgas though that reduced turbine life and effectively reduced fuel capacity as you needed more avgas than kerosene to get the same thrust/range.

 

[ThomasP]

re weights and types of early US & UK jet fuels

see "Jet Lancaster range?"

The RDE/F/KER/210 specification was the first real UK jet fuel spec - it was issued in late-1943.

The first real US jet fuel specification was JP-1 (aka AN-F-32A) issued in late-1944 (I think). Density of JP-1 was .85, so weight was ~7.1 lbs/USgal.

RDE/F/KER/210 and JP-1 were both high aromatic content kerosenes.

JP-3 (aka AN-F-58) was the first 'wide cut' US jet fuel, used operationally from 1947. It was a blend of kerosene and cracked low octane gasoline (usually about 70 octane but it could vary, hence the different densities) with a density of between .728 and .802, so the weight was between 6.07 and 6.70 lbs/USgal.

 

[MiTasol]

Aromatic fuels contain benzene, toluene, xylene and isomers of xylene. None of those compounds is good for you.

Benzene is a known carcinogen with the US EPA declaring in the 90's that it would be the cause of 4 in every 100,000 people using unleaded automotive fuel to develop leukaemia.

Toluene is much safer so long as there are no catalysts around. MEK as a catalyst caused a wide range of cancers and unpleasant fatalities in the deseal-reseal process at RAAF Base Amberley. The was a high level enquiry on this that was very damning - I cannot remember if it was an Commission of Enquiry or a Royal Commission. I just searched for an online copy but could not find it as I could not find my paper copy. If I find it I will post it.

Xylene vapour causes symptoms such as headache, dizziness, nausea and vomiting. At an exposure of 100 ppm, one may experience nausea or a headache. At an exposure between 200 and 500 ppm, symptoms often include feeling "high", dizziness, weakness, irritability, vomiting, and slowed reaction time.

PPM means parts per million and those levels are low.

There have been numerous reports over the last ten years relating to the hazardous nature of modern jet fuels which contain aromatics

 

[GrauGeist]

We used to use MEK (Methyl Ethyl Ketone) soaked rags to clean and degrease parts.

 

[MiTasol]

yeah - loverly stuff but relatively safe on its own. If you stick your fingers in it then it can be detected in your breath within a very short time - counted in seconds, not minutes.

Another one we used to use was hot trichloroethylene. Those vapours made many people "drunk" and careless. Magic paint and grease remover to prepare items for inspection and painting but caused a mean hangover.

 

[MikeMeech]

We used to use MEK (Methyl Ethyl Ketone) soaked rags to clean and degrease parts.

Hi

MEK, well that takes me back to when I was involved in repairing leaks in integral fuel tanks on in RAF VC 10s, about 1976-77 period. We used to go into the wing tanks and inspect where we had spotted leaks under the wings. It meant taking off the PRC Sealant around joints, fasteners etc. cleaning it off with MEK and reapplying the sealant, the MEK also being used to clean the sealant off your hands. During the period I was involved with this work, I was drenched in fuel from one aircraft as the propulsion people had failed to pump out all the fuel they were supposed to and on another occasion the cold air unit used to pump fresh air through the wing tanks while we worked pumped through its diesel exhaust when the wind changed, not a pleasant experience, although it did result in the powers that be putting me on the Queen's 1977 Silver Jubilee flypast in the back of one of our VC 10's as compensation.
The only time we used breathing apparatus was when we had to check out the fuselage centre tank, which we could stand up in, as it could not be fully drained of fuel and there was always some residue of fuel in the bottom of the tank.

Mike

 

[z42]

There have been numerous reports over the last ten years relating to the hazardous nature of modern jet fuels which contain aromatics

As an aside, I don't think there's any particular useful property of aromatics that's needed for jet fuel, it's just what happens to come out of the distillation process. Removing the aromatics, or converting them to something more benign in some reactor, would work but would also increase cost, so..

(Aromatics are of course useful as a high octane component in gasolines, but, well, turbines don't need octane.)

 

[pbehn]

We used to use MEK (Methyl Ethyl Ketone) soaked rags to clean and degrease parts.

I used to work in a chemistry lab in the steel works as part of my training. As a matter of course in steel analysis you use all concentrated acids Sulphuric, Hydrochloric and Hydrofluoric. Cleaning out the store one day when we had little to do we found a full one gallon "bottle" of Carbon Tetrachloride, it had been outlawed years ago as a cleaning agent, apart from attacking the nervous system and liver at high temperatures in air it decomposes to phosgene. Those were the days.

 

[MiTasol]

Do not forget that carbon tetrachloride was used in many fire extinguishers for many years - including aircraft cabins.

Thankfully we now know how bad some of those "good" things were that we and our parents used so often before we learned our lessons.

And hyroflouric acid is another nasty from memory - never been around it thank goodness but my memory is that it is a major health hazard.

 

[pbehn]

Do not forget that carbon tetrachloride was used in many fire extinguishers for many years - including aircraft cabins.

Thankfully we now know how bad some of those "good" things were that we and our parents used so often before we learned our lessons.

And hyroflouric acid is another nasty from memory - never been around it thank goodness but my memory is that it is a major health hazard.

I worked with HF in training but not in actual analysis. It cant be washed off skin in the conventional sense, you have to use glycerine in the hope that any residual acid reacts with the glycerine in preference to skin. It was used in a reaction that had to be done at high temperature needing platinum crucibles, they looked like knackered small tin cups but were worth a small fortune.

 

[Elvis]

So, swap out the four Merlins for a pair Griffons driving five blade contra rotating props and a pair of jets.

You can, but she'll be woefully underpowered.
The B-36 used 6 P&W R-4360 Wasp Majors @ 3800 hp each.
The jets were J47's, rated at 5200 lbs. thrust, each.

 

[Elvis]

We used to use MEK (Methyl Ethyl Ketone) soaked rags to clean and degrease parts.

I remember using MEK straight out of the can, to get the stickum residue off the gas tanks of the big rigs I used to work on.
Dangerous stuff. We were required to where long gloves, safety glasses and a resperator to use the stuff.