Mosquitos and Griffons?

[pigsty]

The lift does not come from the air passing under the wing, but because the flow over the wing is faster than the flow underneath, creating less pressure above than below. The air that has past through the propeller is travelling faster than the surrounding air, so pushing more air under the wing will reduce lift.

Whoops! I forgot - it's slower air over the wing that creates the low pressure that creates the lift. Just when I thought I was beginning to understand aerodynamics ...

[Test Graham]

Bernoulli's theorem linking speed and pressure: if you want to understand aerodynamics that's a pretty basic place to start from.

Faster air over the wing, slower air under. Thus by subtracting the surrounding airspeed the wing flow can be represented by a circulation which appears at the tips as a shed vortex - as seen at airshows on damp days. Or just heard......

[Edgar]

I thought the pitch-down effect was because the centre of lift is generally aft of the centre of mass.

As far as I know, this is a fairly new phenomenon; in the 1940s, the aim was to keep the centre of lift/pressure as near to the CofG as possible, otherwise the workload on the pilot would have been intolerable. Nowadays, with computers doing all of the hard work, it's less important.

According to "Mike" Crosley, adding hooks, etc., to the Seafire caused a rearward shift of the CofG, so the elevators had to be continually worked, to keep the aircraft level, and this was done by adding a bigger bobweight in the elevator control system. Post-war it was realised that this caused other problems, but it had already been cured by the substitution of the original tailplanes, by a bigger set, on the last Seafires & Spitfires. Spitfire tailplanes had a neutral aerofoil section, and zero (+/- 20', later reduced to 10') incidence, so it gave neither positive or negative lift.

Edgar

P.S. Dragging this back on-thread, I've checked on Kew's website, and, as far as I can see, there's no Ministry (or anybody else's) file on a Griffon Mosquito, so, if there were plans, they don't seem to have been taken very seriously; a visit to the Mosquito Museum might turn up something, of course.

Edited December 13, 2011 by Edgar

[StephenMG]

The lift does not come from the air passing under the wing, but because the flow over the wing is faster than the flow underneath, creating less pressure above than below.

Without getting into a discussion on aerodynamics and prolonging the off-topicness (!) I'll just say, for completeness, that Bernoulli's Principle is not strictly the whole story, although it is the 'popular' explanation. The angle of attack of the wing surfaces also generates an upward force (lift) based on Newton's Laws and sometimes known as airflow 'turning'. This is very significant of course because, with Bernoulli's Principle alone, an aircraft would never be able to fly inverted.

In reality there are many principles which play a part in generating lift in an aircraft wing, and the flight regime of the aircraft design will dictate how 'much' of each principle is incorporated into its design.

[Test Graham]

StephenMG: Agreed, but the law is needed as a starter for the subject.

Edgar: This is not a new thing, but basic to all aircraft. You are quite right that the distance between the cg and the aerodynamic centre was kept small to reduce trim loads, but not too small. As the a.c. approaches the cg, the stability decreases and so does the reaction time required. Modern electronics permits continuous instantaneous monitoring of the state of flight, even with negative stability, but this requires the controls moving much more rapidly than any pilot with WW2-period controls could achieve. Modern fighters cannot be flown manually: should the electronics fail the only route left is to eject - and pretty rapidly at that. It is possible to fly unstable aircraft of earlier periods - if not too unstable - but the workload on the pilot is severe and cannot be maintained for long.

[Edgar]

Edgar: This is not a new thing, but basic to all aircraft.

Thanks; that will help to demolish the ravings of a certain French-Canadian, who shall remain nameless.

Edgar

[mhuxt]

Thanks; that will help to demolish the ravings of a certain French-Canadian, who shall remain nameless.

Edgar

Celine Dion posts here?

[stevehnz]

Not sure what you mean about it not having a smaller prop. According to what I can find knocking about the internet it had a 3.0 metre diameter prop off a 109G. That is smaller than any of the props fitted to the Spit Vb in service.

Yes, but not smaller diameter than planes normally fitted with the inverted V engines, so back to the original premiss, a mosquito knock off with DB605s would surely have had broadly comparable performance to a DH Mosquito, smaller diameter props not withstanding. Lets face it, later Fw190s & Bf 109s with their oversized underpropped inverted V engines seemed well capable of holding their own against allied fighters assuming comparable piloting skills & numbers, which of course was seldom the case.

Steve.

[Jennings Heilig]

It was absolutely considered, engineered, and built. There just aren't many photos of them

[kitnut617]

I am currently in the progress of building a DH.101 Sabre Mosquito in 1/72 scale. I'm using information that has been discovered during the last five years or so and working from some drawings that were found at the same time which Tony Buttler was very kind in supplying me with a copy. Even though it was said to be a scaled up Mosquito, it has a number of subtle differences that make it fairly different. To use a base model for the build you need a 1/60 scale kit of a DH.98 Mosquito but as everyone probably knows there's no such animal, I'm building mine from scratch.

From what Tony Buttler has written about (and can be found in the Sharpe/Bowyer book [Putmans too]) the project came to grinding halt when De Havilland were told the particular engines that was planned for the DH.101, they weren't going to get and D.H. were told to consider using Griffons. The Sabres have been described as being a two-stage, three speed variant and this matches with the Sabre VII and VIII engines, both producing a bit more than 3000 hp. While doing some research for my build I found that the engine cancellation coincides with the time English Electric bought out Napier (in 1942 IIRC) and all development was stopped by EE so that the Napier engineers could concentrate on making the Sabres already in production, much more reliable. It doesn't surprise me at all that D.H. cancelled the DH.101 because the Griffons would have been about 600-1000 hp less powerful (and that's each engine).

The DH.101 was designed to carry 8000 lbs of bombs inside the bomb bay, plus two underwing pylons to carry an additional 1000 lbs each.

As far as can be determined, quite a bit of design work was done on the DH.101 and when DH stopped work they started the DH.102. This was to be Griffon powered and contrary to popular belief, wasn't a DH.98. It was actually a scaled down DH.101, still bigger than a DH.98 though. At the time the drawings for the DH.101 were found, so were drawings of the DH.102 and what was called the Jet Mosquito. This was a development of the DH.102. Even though the DH.101 was 1.2 times bigger than the DH.98, it still used the same canopy as the DH.98. Some differences in the design are the top line of the fuselage is dead straight and not tapering off like the DH.98, and it was to have single leg undercarriage, similar to the DH.103 Hornet but bigger (the DH.102 drawing also shows single leg undercarriage). The wheel sizes on the drawing measure out to be close to B-25 Mitchel in size, or the same size as the wheels found on the amphibian Catalina. The tail wheel measures out almost exactly as the front wheel off the Catalina. The contra-rotating props (not counter-rotating) would have been the same diameter as the Hawker Tempests, around 14 feet in diameter and the spinner almost matches the spinner found on the Centuarus Tempest, just a little bit longer but the shape is the same.

Unfortunately, I can't show you any of the drawing as Tony has asked me not to, not until he publishes it along with an article he is putting together all about the DH.101, DH.102 and Jet Mosquito.

[jenshb]

Interesting drawing Jennings - moving the engines lower and a Seafire 47 style intake would probably reduce the frontal area slightly even if the smaller airintake is more attractive.

Jens

[Jennings Heilig]

Jet Mosquito.

We had those when I lived in Florida

[kitnut617]

We had those when I lived in Florida

Joe Cherrie has built a model of the Jet Mosquito and you can find photos of it in the BSP-Fighters & Bombers book.

[grahamf]

I think it never happened as Rolls Royce would have to have made A Griffon that rotated in the opposite direction, I could be wrong on this but If you think about the multi engined Avro Shackleton it uses contra props.

Graham

[StephenMG]

I think it never happened as Rolls Royce would have to have made A Griffon that rotated in the opposite direction, I could be wrong on this but If you think about the multi engined Avro Shackleton it uses contra props.

Graham

It's all hypothetical of course, but that wouldn't have been too difficult to do. They did it with the Merlin for the Hornet simply by adding an idler gear to the propellor reduction gear. That's why the Hornet's starboard engine nacelle is longer than the port one.

Edited December 15, 2011 by StephenMG

[SimonT]

Very interesting thread indeed this!!

Unfortunately, I can't show you any of the drawing as Tony has asked me not to, not until he publishes it along with an article he is putting together all about the DH.101, DH.102 and Jet Mosquito.

Any idea when said publishing is due? Will be interesting reading.

Thanks

Simon

[mhuxt]

The Germans also speculated about what a Griffon-engined Mossie could do, according to this assessment from the BAMA archives:

[kitnut617]

Very interesting thread indeed this!!

Any idea when said publishing is due? Will be interesting reading.

Thanks

Simon

It is to appear in a future issue of Aviation News, but when exactly I'm not sure. Tony had done a previous article about the DH.101 sometime ago, maybe as much as five or six years ago, and his latest one is a re-vamp of this article. Once I get my model finished I will be sending him photos of it, but I also think Joe Cherrie is building one too, so that might be the model pics that Tony will use (as he's used a lot of Joe's model pics in his books)