DH.98 Mosquito questions

[Julian Smith]

I have a few questions about the DH.98 Mosquito that i haven't seen asked anywhere, so i thought i'd try here:

1. On the right hand side behind the wing there is a horizontal stiffener for the access door, which spoils the smoothness of the fuselage. Why did they not incorporate this into the inside of the fuselage instead?

2. Could they have gained a little extra speed by making the tail wheel fully retract behind doors, like (for example) on a P-51?

3. Many models (maybe those without a second supercharger stage on the back of the engine?) have only 5 exhaust ports on each side of each engine, with the rearmost one looking like it handles two cylinders. There looks to be less space on the inside due to the radiators, but it seems curious to have quite different exhaust airflow for the two rearmost cylinders?

4. This is hypothetical - if an inverted engine was used with lower exhausts, could the exhausts point directly backwards rather than slightly downwards, and so give slightly more useful thrust?

5. If the navigator had been put directly behind the pilot instead of abreast (assuming this could be done given the wing structure etc), could this have given a speed increase?

Thanks in advance for any information.

- Jules

--

Julian Smith's home page

 

[Crimea_River]

1. The stiffener spans over two internal bulkheads which protrude through the inner skin and are glued to the outer skin. A proper stiffener would have had to pierce the bulkhead material, resulting in a need to change the production forms and bulkhead designs. It is much easier to simply attach the strip on the outside after the shell was glued together and I'd suggest the cost in drag is minimal.
2. Not much room in the tail for fully retracting wheel. A bulged door would likely have been needed adding weight and complexity. Again little gain for pain?
3. On the single stage Merlin Mossies there was no room for the 6th stack on the rear inner cylinders because of the extended radiator fairing so, yes the exhaust for the 5th and 6th cylinders were combined. This need was eliminated with the 2 stage Merlins as the cylinders moved forward allowing individual stacks for the rearmost cylinders.
4. No comment. Hypothetical and assumes Brits had inverted V's.
5. No room behind the pilot for crew. The wing spar was less than 2 feet behind the pilot's armour plate and the seat butted right up against the forward bomb bay wall. You'd need to extend the nose for a tandem arrangement.

In general, the Mosquito's performance was such a step forward at the time that there would have been little incentive to make small tweaks to gain a few more MPH. Later mods would have been difficult due to needed changes to the production moulds and wing structures.

 

[MiTasol]

1 -- the airflow in that area is fairly turbulent so the stiffener probably has no noticeable effect.

5 -- the nav is partly behind the pilot so there was a small amount of width saving. Obviously dH decided that was the most efficient way to do it. Remember that making the fuselage narrower reduces the width of the bomb bay and the maximum length of that is constrained by the CG problems that would result from one bomb that hung up on the front or rear bomb shackle(s) in a longer bomb bay.

 

[PStickney]

1 -- the airflow in that area is fairly turbulent so the stiffener probably has no noticeable effect.

5 -- the nav is partly behind the pilot so there was a small amount of width saving. Obviously dH decided that was the most efficient way to do it. Remember that making the fuselage narrower reduces the width of the bomb bay and the maximum length of that is constrained by the CG problems that would result from one bomb that hung up on the front or rear bomb shackle(s) in a longer bomb bay.

Since the Mosquito's fuselage width was dictated by the size of the bomb bay, even if it were practical to consider a tandem cockpit layout, it wouldn't have made much of an improvement. Better to have the advantages of the Pilot and Nav/Bomb Aimer able to coordinate better with the more or less side-by-side layout.

 

[Crimea_River]

And a tandem arrangement would have made bomb aiming by the observer a bit of a challenge.

 

[wuzak]

I have a few questions about the DH.98 Mosquito that i haven't seen asked anywhere, so i thought i'd try here:

1. On the right hand side behind the wing there is a horizontal stiffener for the access door, which spoils the smoothness of the fuselage. Why did they not incorporate this into the inside of the fuselage instead?

2. Could they have gained a little extra speed by making the tail wheel fully retract behind doors, like (for example) on a P-51?

3. Many models (maybe those without a second supercharger stage on the back of the engine?) have only 5 exhaust ports on each side of each engine, with the rearmost one looking like it handles two cylinders. There looks to be less space on the inside due to the radiators, but it seems curious to have quite different exhaust airflow for the two rearmost cylinders?

4. This is hypothetical - if an inverted engine was used with lower exhausts, could the exhausts point directly backwards rather than slightly downwards, and so give slightly more useful thrust?

5. If the navigator had been put directly behind the pilot instead of abreast (assuming this could be done given the wing structure etc), could this have given a speed increase?

Thanks in advance for any information.

- Jules

--

Julian Smith's home page

1. The stiffener was an afterthought.

The prototype W4050 damaged its fuselage when taxiing over rough ground due to the tail wheel. The fuselage broke around an access hatch on the right hand side. To keep the testing program moving forward, W4050's fuselage was replaced with the first production fuselage, which then had the stiffener added.


3. IIRC, they could have run the 6 ejector stacks on the inside of the nacelles, there was sufficient space to do so. But the proximity of the exhaust to the radiator would have reduced radiator effectiveness, so they siamesed the last two exhausts.

The original exhausts used a manifold system where all ports on one side led into a common exhaust pipe, which exited low on the nacelle.

And later there were the "saxophone" exhausts, used for night operations.

 

[Wurger]