Halifax as a Dambuster

[fastmongrel]

This is not a what if and I am not suggesting that the Halifax should have been used by 617 squadron.

What I am interested in is what modifications would be needed to fit the Upkeep mine and later the 12,000 lb HC blast bombs and MC Tallboy bombs. I have the suspicion that the only modification possible would have been to lift up the Halifax nameplate roll away the bomber and roll a completely different aircraft underneath the nameplate.

First it's going to need the later extended wing tips and extended tailplanes just to be safe to fly with such a big load at low level.

I am not sure what engines should have been used the Hercules or Merlin.

 

[Admiral Beez]

First it's going to need the later extended wing tips and extended tailplanes just to be safe to fly with such a big load at low level.

I thought at low level a shorter wingspan was better, within reason.

 

[fastmongrel]

I thought at low level a shorter wingspan was better, within reason.

The Halifax had problems with spiral dives when making strong rudder movements. This I believe was cured by the extended wing tips and the squared tailplanes.

I have read the problem was known as rudder reversal and below 5,000 feet manoeuvres were limited to straight and level as it took about 5,000 feet to sort out the spiral dive.

Hardly going to be much fun diving into a valley in the dark if you knew too much rudder and or aileron will put you in the water at 180mph.

Edit: the problem was not called rudder reversal but rudder over balance. The rudder control had a very light touch (compared to the elevators and aileron) too heavy a control input could push the rudder to it's maximum stop point. The rudder would stick and only a dive could force the rudder back to a neutral position.

 

[pbehn]

You may need to move the dams closer to the coast.

 

[Admiral Beez]

I imagine the Halifax would be a better choice than the Short Sterling.

Short Stirling - Wikipedia

 

[fastmongrel]

You may need to move the dams closer to the coast.

The Halifax might have the range with Upkeep but I think the 12,000lb bombs would cause problems.

 

[pbehn]

The Halifax might have the range with Upkeep but I think the 12,000lb bombs would cause problems.

I don't really know if the Grand Slam would have been made, it was designed for a Lancaster to drop it. If people were absolutely determined to drop something like Grand Slam and Upkeep I suppose a lot more modification could have been done to the Halifax bigger wings, more engines … just a matter of how determined they were to do it.

 

[Dash119]

Tallboy - 12,000 Lbs.
Grand Slam - 22,000 Lbs.

 

[Admiral Beez]

The Halifax might have the range with Upkeep but I think the 12,000lb bombs would cause problems.

Are we hitting the dams with 12,000 lb bombs? I thought this was Dambusters and the 9,000 lb rotating bomb?

EDIT, ah I see it now in the first post.

 

[nuuumannn]

I am not sure what engines should have been used the Hercules or Merlin.

You'd definitely want the Hercules engined one, but! Merlin engined Halifaxes were a mixed bag of inconsistency and varied interims of equipment fit and standardisation. With the Halifax III things settled down on the production line and aerodynamically the aircraft behaved itself with all the modifications that had been brought into play with each successive model of Merlin engined aircraft, but the Mk.III didn't enter service until November 1943, which is too late for Chastise.

The early B.Is and B.IIs before the modified tails and the reduction of the rudder overbalance issues just cannot be considered. In the B.II Series IA the Merlin engined Halifax reached its zenith in terms of development, the aircraft has been modified to carry heavier loads and a few drag reduction measures have been put in place. The next step was the Hercules engined Mk.III, which was in fact intended as an interim until the Halifax Mk.IV, which was intended on having Griffons, but this was modified to 60 Series Merlins, but the prototype became the Mk.II Series II, which was cancelled in favour of series production of the interim Mk.III.

Fitted with a fully glazed nose, Boulton Paul Type A mid upper turret, 'D' shaped fin arrangement, which not only diminished the tendency to overbalance but promoted better stability and thus better accuracy, and various drag reduction measures, the B.II Series IA is the best choice within the time frame and by May 1943 is already in RAF service for several months. Incidentally, B.II Series IAs were among the first Bomber Command types to have been fitted with H2S, but that wouldn't have been of too much use for Chastise.

 

[wuzak]

Was the Halifax bomb bay long enough to fit a 12,000lb HC, 12,000lb Tallboy or 22,000lb Grand Slam?

 

[nuuumannn]

Was the Halifax bomb bay long enough to fit a 12,000lb HC, 12,000lb Tallboy or 22,000lb Grand Slam?

Long enough, yes, but not deep enough. The B.II Series IA was strengthened to enable it to carry two 4,000lb bombs or a single 8,000lb bomb, but the doors couldn't be closed fully. When operating like this the performance and range suffered as a result of increased drag. While the space inside the bay was big, it had a series of longitudinal and transverse frames that crossed it and the bomb shackles sat on these. Modifying it to carry the bigger bombs would have meant carrying out greater modifications than those required for the Lancaster, certainly with the Tall Boy, which just required bulged bomb doors that were already fitted to Mk.IIs. Fitting bulged doors could have been done of course, but why bother when the Lanc already has them?

The problem for the Halifax was drag. Such a massive effort was made to reduce drag and modifying it to carry bigger than standard bombs would have produced some niggly side effects that the designers had worked hard at getting rid of since the prototype appeared.

 

[Milosh]

Bomb load of a Halifax III on a mission to Essen in late Oct 1944.
6 x 500 lb MC bomb
1 x 2000 lb HC bomb
5 x 1000 lb SAP bomb

 

[nuuumannn]

Having looked at this a bit more, one issue the Halifax has with carrying bigger bombs internally, i.e. with the doors completely enclosed was the doors themselves. The Lancaster had two bomb bay doors that fully enclosed the bay, the Halifax had eight. The doors were split into two sections fore and aft because of a pronounced kink in the lower fuselage and each half had four doors, being split longitudinally into a curved upper and contoured lower section. When opening the upper section slid upwards to sit against the outside fuselage, whereas the lower section slid inwards to sit inside the bomb bay against the side wall.

The actuation of these doors was via braced strut assemblies with pivot points actuated by hydraulic rams, the forward doors' foremost actuators were against the forward bay bulkhead, the forward doors' rearmost actuator was on a bipod assembly within the bay itself. The rear doors followed this arrangement in reverse. With a normal bomb load, these actuators and the movement of the doors don't present a clearance issue, but with larger bombs and thus larger doors, they might.

To modify the size of the doors would mean that the lower section of each door, would have to be curved further to necessitate an increase in useable size within the bay and would take up useable space in the bay itself when open. Not only that, but the actuators within the bay, as opposed to those against the bulkheads, would present an obstruction to the movement of the doors themselves if they were enlarged.

This picture illustrates clearly the doors in the open position, with the larger lower doors sitting inside the bay and their actuators visible.

https://live.staticflickr.com/65535/48710752862_80332e9e8f_c.jpg

A terrific image of a fully loaded Halifax with its wing bays open as well. Note the location of the lower door actuators in relation to the bombs within the fuselage bay.

https://i.pinimg.com/originals/9b/84/e8/9b84e8466824a796e8348c62ce52a399.jpg

 

[fastmongrel]

Great post I didn't realise the Halifax bomb bay was so complicated. Of course for the Upkeep mine a lot of that complication would be stripped away.

 

[nuuumannn]

Of course for the Upkeep mine a lot of that complication would be stripped away.

Yup, would make sense to do what they did with the Lanc and put aerodynamic fairings around the bay entrance.

 

[fastmongrel]

Yup, would make sense to do what they did with the Lanc and put aerodynamic fairings around the bay entrance.

The more I look at it the more I realise the elegant simplicity of the Lancaster.

 

[nuuumannn]

The more I look at it the more I realise the elegant simplicity of the Lancaster.

Yup, they really got it right (after all the stuff they had to fix on the Manchester, of course... ahem)