The Legendary Avro 6 Bomb Carrier for the Mosquito

[wuzak]

This is the arrangement for carrying a single 1000lb TI in a standard (Mk.XX) Mosquito bomb bay. Some changes were required to the stiffeners of the bomb bay doors to enable the bomb to fit.

Also, the twin carrier shown in the OP was to be able to carry two:
1000lb TI
or 1000lb MC
or 1000lb Mk. VII Mine.

Does anybody have any information about the latter?

To carry the MC bomb new hinges were required to give additional clearances over the bombs (17.5" diameter).

 

[Gnomey]

Great information! Thanks for sharing.

 

[Shortround6]

Another tanks for the information and effort.

 

[wuzak]

You're all welcome.

 

[wuzak]

I have obtained some more documents from the National Archives.

These relate to the bombing and pyrotechnic installations of various Mosquitoes.

Report #2, dated 6 December 1941, investigated the bombing installation of Mosquito W4087. This was done by AAEE Boscombe Down.

The bomb sight installed on W4087 was the Course Setting Bomb Sight (CSBS) Mk IXA. Immediately it was realise that this sight was not suitable for use in the Mosquito as supplied as it was limited to a bombing speed of 240mph TAS. To use the sight would require false settings for speed, height and wind.

The sight was positioned in the centre of the bomb aimer's position, which was found to be generally satisfactory, though sighting the target from long range was difficult. It was recommended that the sight be moved 1.5in to the right to ease this issue..

Heating in the bomb aimer's position was considered good, sighting was thought excellent - leaning forward the bomb aimer could see the release of the bombs. W4087 was fitted with an electrically heated window, which was thought to be distracting and an impediment to bomb aiming, and so its removal was recommended. Additional lighting in the bomb aimer's position was also suggested.

The bomb doors were considered slow in operating. It took approximately 20s to both lower and raise the doors, which would mean a minimum of 40s would be required for an emergency jettison of the bombs. Since the speed of the Mosquito was reduced by approximately 20-25mph with the bomb doors open, this was considered unsatisfactory. Recommendations for improving the operating speed of teh doors and their impact on the aircraft's speed were made.

Bombing trials consisted of several drops from low level (~250ft) with release by the bomb aimer or the pilot, and from medium altitudes (~6000ft) with release from the bomb aimer.

Low level drops by the bomb aimer without use of the sight had an avergae error of 40 yards. This was done in adverse conditions "bumpy" with low cloud.

With the pilot releasing the average error was 44 yards.

From medium altitudes it was found that the error was around 200 yards on average. It was found that, due to the higher speed of the Mosquito, that lining up on target could be difficult as small course corrections required a longish period of time, and could result in the aircraft still correcting when bombs were released. Large bank angles used to speed up the correction caused the bomb aimer excessive G forces.

Fudge factors were required for speed and height for the CSBS. A strong recommendation for the use of the Mk XIV bomb sight was made.

 

[wuzak]

Mosquito DK 290 was used in bombing trials by the AAEE in late October/early November 1942.

The trials focused on the bomb combination of 1 x 1000lb GP bomb + 2 x 500lb GP bombs, all short tail versions.

The 500lb GP bombs were fitted to the rear of the bomb bay, and placed symmetrically on the centreline. The 1000lb bomb was fitted to the forward part of the bomb bay and offset 3.5in to port. Presumably this was done to clear the bomb door edge stiffeners.

The report describes the doors as being "dished" internally for clearance, this not changing the outside profile of the doors.

The bombs needed to be crutched 5° nose down to ensure clearance for the doors.

The standard winch was considered satisfactory for the 500lb bombs, but it was thought that the cable of insufficient strength for repeated use with 1000lb bombs. The winch itself was considered marginal, and stress tests were recommended.

It took a team of 3 armourers 25 minutes (from doors open to doors closed) to install the 500lb bombs. Considerable difficulty was experienced loading the 1000lb bomb, some 1 hour 20 minutes being taken. It took 2 men 1 hour 15 minutes to locate the pin which locates the release shackle to the beam. This was with one side 4°, so it was redone on a level hangar floor and found to take 4 minutes. This would be unsatisfactory for operational use, as level surfaces would be rare and the time otherwise is too long.

Once in position, the bombs had the following clearances:
500lb
Diving 55°
Climbing 28°
Rolling 15°

1000lb
Diving 15°
Climbing 20°
Rolling 16° port, 30° starboard.

The 1000lb bomb was fitted with a flat nose plug rather than the standard plug, which would have reduced the diving clearances.

The beam carrying the 1000lb bomb allowed some twisting movement, so strengthening would be required to be able to withstand evasive manouevres.

Though the MAP had not requested it, the AAEE test fitted a pair of 160lb SBCs on the 500lb bomb racks. It was found that the strengthening band around the SBC interfered with the rear crutch of the bomb carrier, the crutches for the 500lb carrier being closer together than normal practice.

A list of modifications were given to improve the installation.

No actual drop tests were conducted, as the aircraft was being used for performance tests and was unserviceable for a period of time.

Given that the only 2 1000lb GP bombs dropped from Mosquitoes (that I know of) was on the Oslo raid in December 1944, it is doubtful that this installation wa sinvestigated further.

Also, the 1000lb GP bomb was an older type bomb, with a charge-weight ratio of 33% - a filling weight of 357-378lb HE compared to the 1000lb MC bomb's 475-525lb HE.

The MC bomb was also 1.6in larger in diameter and length, which may have made it too large for a similar installation.

 

[Shortround6]

Once again, thank you for your efforts and time in bringing this information to us.

 

[nuuumannn]

Great info Wuzak.

1000lb Mk. VII Mine. Does anybody have any information about the latter?

An air dropped mine based on the Mk.V and introduced in 1944; it had a warhead of around 675 lbs. Standard weapon used by the RAF for aerial mining operations, carried out by Bomber Command rather than Coastal Command. Found this whilst looking for a picture:

"The British accomplished almost all allied mining in the European theater. The Royal Air Force (RAF) quickly adapted to the task, and Bomber Command laid 47,307 mines--eighty percent of the total offensive effort. In 1936, an officer in the Air Ministry had been the first to advance the idea of air--dropped magnetic mines. In 1939 that same airman commanded No.5 Group--the sole bomber unit charged with aerial minelaying. He was Arthur T. Harris, who quickly ensured all Bomber Command aircraft could carry mines once he became commander-in-chief in 1942. From the first few mines laid by his Handley Page Hampdens on April 13, 1940, Harris raised the number delivered to just over 1,000 in 1941, and then an average of 1,000 per month for the rest of the war.
***
Bomber Command dropped mines along the Norwegian coast, in the Baltic Sea, Heligoland Bight, the Bay of Biscay, and the Mediterranean along the Italian-Sicilian coasts. As an example of tactical support, the RAF laid nearly 4,000 mines between April and June 1944 to prevent interference with the Normandy landings. The British also mined inland waterways, in particular the Kiel and Koenigsberg Canals, and the Danube River. Thus, the objectives of minelaying varied, from threatening warships and U-boats, to disrupting Germany's ability to import raw materials, transport supplies, or move troops."

"For the effort, (about five percent of Bomber Command sorties), the RAF could eventually claim 762 Axis ships sunk and 196 damaged.(Altogether, British mines in the European theater totalled 260,000--mostly defensive--and ship losses from them numbered 1,590). In addition to sinking ships, the mines disrupted sea communication and blocked transportation on inland waterways. Another effect was tying up a large German minesweeping force, which comprised forty percent of all German Navy activity by 1945."

From here: EagleSpeak: Sunday Ship History: Mines from the Sky

 

[wuzak]

Mosquito B.IX LR495 (standard bomb bay) was used for trials of several different stores.

LR495 was fitted with 4 x Handley Page 500lb Universal Carriers in the fuselage and one Universal Carrier Mk III on each wing.

• 100lb AS - could not be carried in the fuselage stations as the rear crutches didn't meet the bomb. Also could not be carried on the wing due to fouling the fairings.
  
• 120lb Smoke Bomb - the rear crutches of the HP carriers sat on the tail unit - which was deemed unacceptable. Flight tested to 350mph on wing stations.
  
• 200lb Smoke Float - could only be carried on front fuselage and wing stations. American lugs and suspension band had to be removed to allow closing teh bomb bay doors.
  
• 250lb SAP - Can be carried on all stations, but wing mounted bombs must have 2 bladed arming vanes and 1/8" depth studs on safety clips.
  
• 250lb LC - can only be carried in forward fuselage stations, owing to length, and wing stations. Needs tail shortened by 7" to allow carriage on all stations.
  
• 250lb B.III - can be carried on external carriers, without fairings. Cannot be carried in fuselage owing to large diameter.
  
• 250lb DC - cannot be carried externally with fairings in position.
  
• 250lb SCI - wing fairings must be used (this is an external store only). Crutch adaptors for the Universal Carrier Mk III are required to carry this bomb.
  
• 325lb DC MkXVII - could only be carried on wing carriers. There was some difficulty in fitting the bombs to the carriers.
  
• 400lb SCI S/L - front fuselage and wing stations only. Reduction of tail length by 12" required for fitting to all carriers.
  
• 500lb SAP - front fuselage and wing stations only. Reduction of tail length by 7" required for fitting to all carriers. Wing mounted bombs must have 2 bladed arming vanes and 1/8" depth studs on safety clips.
  
• 500lb AN M43 (US) - can be carried on wing stations with vanes at 45°. Doors cannot close when carried in fuselage stations owing to size of tail.
  
• 500lb LC.II - can only be carried on forward fuselage and wing stations. Reduction in tail length by 11" required to fit all stations. Farings have to be removed for wing carriage.
  
• 500lb SCI - wing fairings need to be removed to fit this bomb
  

Order of release of bombs was:
No 1 - rear starboard fuselage
No 2 - rear port fuselage
No 3 - forward port fuselage
No 4 - forward starboard fuselage
No 5 - starboard wing
No 6 - port wing

 

[wuzak]

Summary of bombs which could be carried by the Mosquito with standard bomb bay.

No   Type               Stations
2*   100lb AS           5-6
6*   120lb Smoke        1-2-3-4-5-6
4    200lb Smoke Float  3-4-5-6
6    250lb SAP          1-2-3-4-5-6
4    250lb AS           3-4-5-6
4    250lb LC           3-4-5-6
2*   250lb B            5-6
6*   250lb DC           1-2-3-4-5-6
6    250lb GP           1-2-3-4-5-6
2*   250lb SCI          5-6
2    325lb DC           5-6
4*   400lb SCI S/L      3-4-5-6
6    500lb MC           1-2-3-4-5-6
4    500lb SAP          3-4-5-6
2    500lb AN M43       5-6
6    500lb AN M58       1-2-3-4-5-6
4*   500lb LC.II        3-4-5-6
6    500lb GP           1-2-3-4-5-6
2*   500lb SCI          5-6

* fairings for wing mounts have to be removed

 

[wuzak]

Canadian built Mosquito MK XX VB328 was checked for its bombing installation and found to be be the same as the IX.

Tests conducted were with standard bombs - 500lb MC/GP and 250lb GP/SAP, 500lb SAP as well as the 250lb SBC. It was noted that the 500lb SBC could only be fiteed to the forward carriers, as when fitted to the rear they fouled the hydraulic door mechanism. It was noted, from prior experience, that 4 of the 160lb SBC could be carried, though they didn't have any to test.

 

[parsifal]

This is amazing stuff thanks so much for bringing this forward.

Do you have similar information for RAAF mossies?

 

[wuzak]

This is amazing stuff thanks so much for bringing this forward.

Do you have similar information for RAAF mossies?

I have no specific information about RAAF Mosquitoes.

These are all tests at the Aircraft Armament Experimental Establishment (AAEE) Boscombe Down. So it is not specific to the RAF or a unit.

 

[wuzak]

Mosquito DZ594 was a converted B.IV with the bulged bomb bay. It was used for trials of the alternate bomb installations of 1 x 4000lb HC/MC/GP bomb or 4 x 500lb MC/GP bombs.

The 4000lb bomb was carried on a EM Release Unit Type F, which was permanently fitted to the bomb bay. Two 2000lb winches were provided for hoisting the bomb. During trials the forward winch slipped when the bomb was almost in position, while the rear winch slipped continuously. Inspections of the units by de Havillands and the winch manufacturer, Stones, came to the conclusion that they were faulty. Once replaced no further issues were experienced.

The crutches worked well for the 4000lb HC bomb, but the crutch pads were at the extent of their travel and only touching on their edge when used with the 4000lb MC and GP bombs. It was recommended that the crutch pads have a universal joint, extra travel and a more useable nut.

The rear fuzing box was incorrectly placed for the MC and GP bombs, being behind the tail drum. This needed to be moved forward of the tail drum.

Flight trials included speeds up to 320mph and evasive manoeuvres. The HC bomb was found to be satisfactory, but the front crutch pads worked loose when trialed with the MC bomb. Recommendations were to add a double lock nut to prevent this happening in the future.

Both HC and MC bombs were dropped satisfactorily from the Mosquito at 290mph IAS.

Tests were done with two experienced sets of armourers to see how long it would take to convert to use the 4 x 500lb option. The times for conversion were 1h50min and 3h, which was considered unsatisfactory.

It was found that the castings for the bomb supports (cross members, I suspect) were not interchangeable and were as much as 1/2" out of alignment. It also required considerable force to install the lock pins.

The crutches for the 4000lb bomb installation had to be put into their stowage position when using the 4 x 500lb option.

The 4 x 500lb installation was, otherwise, the same as the B.IX above.

Flight trials were satisfactory with this installation, the bombs being dropped at 250mph - slow speed due to extremely turbulent conditions.

Hoisting times for 4 armourers were:
4000lb MC - 9 minutes
4000lb GP - 11 minutes
4000lb HC - 6 minutes
4 x 500lb - 35 minutes

Bomb clearences were

	Dive	Climb	Roll
4000lb MC	29°	27°	12°
4000lb GP	30°	36°	17°
4000lb HC	25°	26°	14°
4 x 500lb	33°	33°	15°

It was noted that the tail of the 4000lb GP bomb bears on the bomb bay roof, the doors only just close on the 4000lb HC and much care is required when engaging the suspension lug of the MC bomb with the release unit.

 

[wuzak]

 

[wuzak]

Just reading through one of the files again and I found that TH Dixon and Co of Letchworth supplied six 2,000lb twin adaptors for use with the 2,000lb AP armour piercing bomb.

No mention in teh file as to whether the adaptors were fitted to a Mosquito or whether the installation needed the bulged bomb bay doors. The 2,000lb AP bomb was long and skinny, so it may not have been.

 

[wuzak]

Maybe this is where the idea of the Avro 6 store carrier originated.

 

[GregP]

Wonder if they ever tried another Mosquito airframe? That could be a never-ending search for something that doesn't exist.

I find it strange that the P-38 didn't experience issues if the Mosquito did. Now I'm wondering if the P-38 was bombing, when it did bomb, at 150 knots. We might be able to find something on that one.

Interesting tid-bits to look at.

 

[wuzak]

Wonder if they ever tried another Mosquito airframe? That could be a never-ending search for something that doesn't exist.

I find it strange that the P-38 didn't experience issues if the Mosquito did. Now I'm wondering if the P-38 was bombing, when it did bomb, at 150 knots. We might be able to find something on that one.

Interesting tid-bits to look at.

Issues with what?

 

[stona]

This has been a very interesting read and there is some very useful information unearthed and posted by wuzak, a big thanks for that.

Regarding aerial mines, as far as I can establish there weren't many A Mk VII mines available in 1944. It didn't appear in numbers until January 1945 and then alongside the less sophisticated (certainly in terms of fusing) A Mk V which it was supposed to replace (Hogben and MacBean). Some got sent to the Far East and a number of the 4,374 mines laid in that theatre, a paltry number, were A Mk VIIs.
The Mosquito could carry two, but in the Far East liberators were often used, they could carry six, and for a very long way, over 1,000 miles.

Bomber Command officially took over mining operations from Coastal Command on 25th March 1942.

Cheers

Steve