Improved Skua for FAA?

[Geoffrey Sinclair]

From Norman Friedman,
The propeller for the centre shaft of Illustrious had been removed before the ship was hit by a Kamikaze. It was operating on two shafts, top speed around 25 knots and at 19 knots significant vibration started. The shaft had been distorted in the January 1941 attacks. The flight deck armouring was the area between the two lifts. Apart from the hits there were a number of near misses causing damage to the hull, First attack,

1) 1,000 lb bomb on S.2 pom pom mounting
2) 1,000 pound bomb through the front flight deck, exited then exploded 10 feet above the water
3) 1,000 pound bomb through the after lift, which was on the way up with a fighter, exploded 10 to 20 feet below the lift platform. The fighter and its pilot simply vanished.
4) 1,000 pound bomb passed through the armoured flight deck, burst 10 feet above the hangar deck.
5) 500 pound bomb hit the edge of the after lift.
6) 1,000 pound bomb went through P.1 pom pom, hit the armour belt, failed to explode but did start a fire.
7) 1,000 pound bomb near miss starboard side aft
8) (Second attack, later that day) 500 pound bomb down the remnants of the after lift.

9) (6 days later in Malta) several near misses then a 1,000 pound bomb through the aft flight deck, exploding 13 feet below the Captain's day cabin.
10) (Also at Malta) several more near misses then a 1,000 pound bomb very near miss port side, opening up the plating, causing immediate 5 degree list to port, shock effects cracked the port turbine feet and caused other machinery damage.

All up 83 men killed. Left Malta 2 weeks after the first attack, doing 24 knots, to Alexandria for a while then to the US, arriving in May and leaving in November.

"The centreline shaft was repaired but it was never satisfactory, and it later caused severe vibration when run at high speed. The gland packing of the centre shaft deteriorated so badly that the centre propeller was actually removed before the Okinawa operation"

 

[EwenS]

There has been a lot written about the Illustrious class, much of it critical and a lot of it undeserved in my view. With regard to Illustrious, I don't think there is quite such clear cut a link between the 1941 damage to Illustrious and the final speed reduction in 1945 nor to the claims of ongoing vibration problems postwar or to much worse claims of twisted keels etc in both her and Formidable. I don't think anyone has really done a deep enough dive into the archives to discover the full story.

Let me start by saying that no carrier suffered so heavily and from such large bombs as Illustrious did in January 1941 and still stayed afloat. Built to withstand 500lb bombs she was hit by bombs up to 2,200lb as was Formidable. See the damage reports.

Report:

HMS Illustrious, January 10, 1941, Damage Report (Bomb & Shell)

www.armouredcarriers.com

Most of the hits were outwith that part of the flight deck covered by 3" armour plate. So there was bound to be heavy damage. The question is how well that was repaired while she was at Norfolk. And how did it affect the ship in future years.

Many ships suffer from vibrations in various parts of their structure. Often they manifest themselves far from the cause. This can usually be resolved while they are on trials. ISTR reading many years ago that the 5 British carriers that used a three shaft layout suffered in various ways. Mostly they go unremarked on. I've linked some relevant articles at the foot of this response about causes. Ark Royal for example from Poolman about her trials:-

"There were some teething troubles. The forty-foot overhang of the flight deck astern and the position of the rudder immediately abaft the centre screw put an unusual strain upon her lightly built structure aft, and it was necessary to stiffen some of the lighter plating."

Most famously the US battleships North Carolina & Washington experienced terrible vibration problems while brand new out of the yards on trials. It took months of trials to resolve with the eventual solution being a new design of propellor with 5 blades for two of her shafts.

There is a comment on the Royal Navy Warship Histories page for Illustrious for 24 May 1940:-
"Final acceptance trials. (Note: Excessive vibration was noted particularly in the Bridge Structure. This problem was never completely resolved during subsequent service.)"

Such was the urgency to get Illustrious to sea that her trials were cut as short as possible (2 days) and she sailed for work up in the Caribbean less than a month later.

It is the only record I've found to date of such a problem that early in her career but it is curious and raises the possibility of an underlying problem even before she was bombed.

As for the stern gland packing failing, this is a regular maintenance item for ships. I've seen articles saying it can need replaced as frequently as every 3 years. And it would appear that there had been plenty of opportunity to address any issues. Illustrious had refits in early 1943 (3.5 months), late 1943 (3 weeks) and autumn 1944 (8 weeks at Durban). Yet by Feb 1945 the problem was so bad the prop had to be removed while at Sydney. Why the sudden deterioration in the space of 4 months? Was removing the centre prop merely a precautionary measure to ensure it wsnt going to be a bigger problem when she was fat from a dock?

I have harboured doubts about the intention to send Illustrious to the Pacific in 1945 in the first place. RN plans for the BPF always revolved around the core of a 4 fleet carrier task force. The only reason I can see for sending Illustrious, given that that prop had to be removed, was due to delays with Formidable. Never much mentioned is the fact that Formidable suffered a major machinery failure (some kind of turbine failure IIRC) after she left the UK at the end of Sept 1944. She then spent 3.5 months at Gibraltar being repaired before continuing her journey east. Had she arrived on schedule Illustrious could have been sent home.

Incidentally, the reduction in Illustrious's speed to 25 knots is not the big issue that it might first appear. Carrier Task Force standard operating procedures saw operations generally carried out at 15-25 knot range. Many reasons for that particularly fuel burn, AS escort limitations to name but two as I've noted previously on other threads.

Now Friedman. Yes she had her centre propellor removed and the shaft locked while at Sydney in Feb 1945 due to a vibration problem. Everyone agrees about that. But just what was the cause of the vibrations leading to the speed reduction to 19 knots?. What Friedman actually says is this:-

"Illustrious suffered Kamikaze damage on 6 April 1945, a bomb-carrying Judy (D4Y3) skidding past her superstructure into the water The only immediate apparent damage was a large hole in the 272 radome forward of her bridge. However, the Kamikaze's bomb exploded underwater near the ship, causing severe shock damage. The outer hull was opened up and some of the frames cracked; Illustrious was limited to 19 knots."

So the speed reduction comes after the kamikaze strike. The bomb has been variously rated at 1700-2000lb in different publications. In suicide form the D4Y3 could carry 800kg (1,764lb). It exploded about 50 feet from the ship. The extent of the hull damage only became apparent when they put divers down after the ship arrived at Leyte Gulf on 16 April. That was the final nail to end to her wartime career. For comparison, look at the hull damage she suffered while at Malta from a near miss from either an 1,100lb or 2,200lb bomb. If the 1945 damage was comparable then it is small wonder she had a vibration! And she escaped from Malta in 1941 at 20 knots.

And the bomb that caused the Malta damage was only supposed to be 1,100lb. Is it small wonder therefore that her speed was further reduced if damage was on this kind of scale?

And now we come to postwar. She spent 12 months under repair and refit at Rosyth from the end of June 1945. There is a passage in an article refuting many of the comments about Illustrious in an article written by Stuart Slade. It is worth repeating here, but I've provided the links below for anyone wanting to read more.

"Of the British armored carriers, Formidable and Illustrious were write-offs due to war damage. By the end of the war, Illustrious was in very poor condition; her centerline shaft was history due to structural deformation and her machinery was shot.

- Illustrious had been at war since 1940 and Victorious and Formidable since 1941. Naturally, they had been "used" much harder than 1943/44 Essexes which served shorter combat careers (many not more than one operational war deployment). So it is natural for their post-war condition to be poorer than the Essexes.

A more accurate 'tour of duty' comparison would be with the treaty ships Enterprise and Saratoga.

- The unique circumstances of Illustrious's battle damage has already been referred to (but not mentioned by Slade). Her centreline shaft had to be cut away in 1945 to reduce vibrations. Ironically, it was a US solution for severe vibrations in its own warships that was applied in late 1945 to fix Illustrious - a five-bladed propeller was affixed to her repaired centre shaft. Vibrations returned about three years later due to wear on the wing shafts."

As I noted above replacing the stern gland packaging is a regular maintenance item for ships so not necessarily indicative of a hangover from wartime damage.

Slade article History and Technology - Were Armored Flight Decks on British Carriers Worthwhile? - NavWeaps
Response refuting many of the criticisms raised by Slade Report:

Another aspect of the Illustrious class that is only rarely touched on is the problems Victorious, which suffered no major hull damage during the war, had with her rudder starting in Aug 1944. From McCart "HMS Victorious 1937-1969":-

"...the Victorious suddenly hoisted 'Not Under Control' balls at the masthead as her rudder had jammed. It was the first indication of a problem which was to stay with her for the rest of her career."

She then immediately spent about 2 weeks at Colombo for "maintenance" followed by a month Nov/Dec in the dry dock at Bombay to try to fix it. She had then been scheduled to have a 7 week period in dry dock at Sydney from mid-Aug 1945 after the operations off Japan. That was to have included fitting a new rudder shipped out from the UK. That refit was cancelled. Instead she carried it home, suffering more rudder problems in heavy weather en route to Colombo. It was finally fitted Oct-Dec 1945 at Devonport as part of the refit she received there.

So the question I have is, was there some kind of design weakness in these 5 carriers (Ark & the 4 Illustrious) around the stern section as a result of choosing a three shaft layout in the first place? Perhaps it was made worse in Illustrious by virtue of her bombing off Malta. But none of it seems to add up to the claims of bent & twisted keels etc. If things had been that bad why hasn't it appeared in official documents that the likes of Hobbs & Friedman can reference. If I've missed something I'd like to hear about it.

It is interesting that both the other great carrier navies, Japan & the USA, came to see the advantage of flight deck armour if not the full blown armoured box hangar on British carriers. The Japanese did come closer with splinter protection to the sides of the hangar and making the flight deck the strength deck in Taiho. On the subject of flight deck armouring all the British, American and Japanese ships fitted with armour on the flight deck restricted it to the areas between the lifts. The advantage that Japan & the USA had was that they could build a bigger ship being free of Treaty limits by the time that thay were laid down.

History and Technology - Shake, rattle and Roll: Vibration in ships - NavWeaps

www.navweaps.com

History and Technology - Designing a Propeller - NavWeaps

www.navweaps.com

History and Technology - Shafting a Ship - NavWeaps

www.navweaps.com

 

[Macandy]

The vented blast myth.

Here are some excerpts from the damage report for the Enterprise when it was struck by a kamakazie on May 14, 19445
View attachment 673755
View attachment 673754
The famous photo of a portion of the elevator 400 feet in the air.
View attachment 673762
Note the flight deck was bulged upwards by 3 and and half feet
View attachment 673758
Full report is here: USS Enterprise CV6 War History 1941 - 1945
From the Wasp lost in action report
View attachment 673757
Elevator blown up and over. Side venting doesn't seemed to have helped.

http://www.ibiblio.org/hyperwar/USN/rep/WDR/U.S.S.%20WASP%20(CV-7),%20TORPEDO%20DAMAGE%20-%20South%20Pacific,%20September%2015,%201942%20(LOST%20IN%20ACTION).pdf

The statement that
" the shock was fed down through the armoured box into the hull causing structural damage like bent shafts, twisted keels and other not good outcomes.
The other thing was a fire in the hanger - it didn't vent and temperatures reached such high levels, yet again, twisted hull" is not true . Bent shafts were caused by underwater explosion from near misses. What specific references to you have for twisted hulls from hanger fires?

As to your statement that the US didn't want armored flight decks here is an excerpt from the USS Franklin damage report
View attachment 673759
Report is here: USS Franklin CV-13 War Damage Report No. 56
Actually the USN was 'stupid" enough to follow the RN. Every USN fleet carrier after the Essex class was fitted with an armored flight deck. It was a decision based on experience with the survivability of RN carriers. Note that the strength deck was still at the hanger level on the Midway class, the armored flight deck was pure superstructure .
It also important to note that the USN carriers were struck with smaller bombs (500lb) than the RN were hit with in the Med. The destructive power of a 1000 lb bomb was more than twice that of a 500 lb. NO carrier suffered any where near the number of bomb hits the Illustrious took on January 1, 1941 and lived to tell the tale.
As to the closed hanger the USN spent a lot of money post war turning their Essex class carriers into Illustrious look alikes.

Aircraft Carrier Intrepid | Intrepid Museum

Commissioned in 1943, Aircraft Carrier Intrepid survived five Kamikaze attacks and a torpedo strike during WWII. The aircraft carrier later served in the Cold War, Vietnam War and as a NASA recovery vessel.

www.intrepidmuseum.org

Note sides are plated and the bow enclosed.
Another thing to note is the appalling casualty rate on US carriers which was far far greater than on RN ships. I have the stats somewhere and will dig them up.

The rebuilt Essex class were fitted with a 1.5" steel flight deck, not because they 'wanted to mimic' the Illustrious design, it was simply needed as a strength deck to operate the much heavier jets.

The Midway design was a disastrous dead end, terrible ships with an awful and vicious roll thanks to being so top heavy with the pointless heavy armoured deck.

No US carrier after the Midway dead end used an armoured flight deck. They all use steel strength decks of 1.5"-2", a simple design requirement due to their huge size.

 

[ThomasP]

The Midway class - as built with a 3.5" thick armoured flight deck - had no problems with rolling as such. The armoured flight deck was not part of the strength girder (it only covered the armoured box between the fore and aft elevators) and it is easy to see the expansion joints in the original deck. The only reason there was a bit of a problem with roll later, was the relatively low freeboard as built coupled with the much widened and angled flight deck after rebuild. As built the deck forward and aft of the elevators was only .75" thick. The entire widened angled flight deck after rebuild was 1.5" thick (I think). The widened and angled flight deck was designed as a "semi-strength deck".

The Forrestal class was the first US carrier design (that was also built) that incorporated an armored flight deck as part of the hull girder. The flight deck was of homogeneous quality 1.8" thick plate.

The Forrestal and all subsequent US carriers incorporated the British idea of an armoured flight deck and enclosed hangar/hurricane bow, although they used deck edge elevators.

Armour thicker than 1.8" was used in the flight deck in the Enterprise, and in all later US CV/CVNs. The current operational CVNs have armoured flight decks of significantly increased thickness. (The actual details are still classified.)

Incidentally, the UK's new Queen Elizabeth class CVs also have armoured flight decks.

 

[Admiral Beez]

The Skua was a dead end in development terms - might as well investigate a new airframe altogether.

Indeed. But if if they persisted, I wonder if a single seat fighter variant would have looked like a single-seat, narrow-bodied Balliol.

And I thought the Firebrand had a disproportionately tall tail.

 

[SaparotRob]

It does look better.
I like big tails and that I can't deny.

 

[Snautzer01]

It does look better.
I like big tails and that I can't deny.

Yeah some kid made a song about that.

 

[nuuumannn]

I like big tails and that I can't deny.

You an' me both, bruthah...

 

[nuuumannn]

And I thought the Firebrand had a disproportionately tall tail.

Dunno how Blackburn got that so wrong. Horrendously over engineered aeroplane. Brown, resident FAA test pilot du jour had little nice to say about flying it.

The Balliol on the other hand was a nice aeroplane to fly, apparently, although with the Mercury was underpowered. It was a retrofit because the Mamba turboprop was taking too long and the decision was made to equip production aircraft with Merlins instead. I think it looks good with a round engine.

 

[SaparotRob]

Dunno how Blackburn got that so wrong. Horrendously over engineered aeroplane. Brown, resident FAA test pilot du jour had little nice to say about flying it.

OOOH, OOOH, I know!! Put 20 pounds of crap into a 5 pound sack, per government specification?

 

[nuuumannn]

OOOH, OOOH, I know!! Put 20 pounds of crap into a 5 pound sack, per government specification?

Brown said it was built like a battleship... And flew like one, too!

 

[Reluctant Poster]

The rebuilt Essex class were fitted with a 1.5" steel flight deck, not because they 'wanted to mimic' the Illustrious design, it was simply needed as a strength deck to operate the much heavier jets.

The Midway design was a disastrous dead end, terrible ships with an awful and vicious roll thanks to being so top heavy with the pointless heavy armoured deck.

No US carrier after the Midway dead end used an armoured flight deck. They all use steel strength decks of 1.5"-2", a simple design requirement due to their huge size.

I did not state than the Essex class was rebuilt with an armored flight deck. They were rebuilt with closed hanger sides and enclosed bows like the Illustrious.

Your statement "The other thing was a fire in the hanger - it didn't vent and temperatures reached such high levels, yet again, twisted hull time." is physically impossible. The plastic deformation temperature of A36 steel is ~ 200 C (392 F). To distort the hull would require heating thousands of tons of steel to that temperature. The ship would become a gigantic oven baking the crew. Also note that the ship is floating on a giant heat sink. Venting by the way provides oxygen to the fire increasing heat release rates and therefore temperatures. One of the best ways to stop a fire is to cut off its oxygen supply. The various foam and gas fire suppression systems operate on the principle of reducing the oxygen supply to the fire. Venting is done to clear smoke not to stop the fire.

 

[Reluctant Poster]

OOOH, OOOH, I know!! Put 20 pounds of crap into a 5 pound sack, per government specification?

I wouldn't blame the government for the Firebrand. Blackburn simply wasn't the A team when it came to designing aircraft. They were given a reset and came up with the Firecrest which was actually in many ways worse than the Firebrand.

Blackburn Firecrest - Wikipedia

en.wikipedia.org

 

[Admiral Beez]

Blackburn simply wasn't the A team when it came to designing aircraft.

It's amazing that nine years after the Firecrest debacle, Blackburn somehow arrived at one of the superlative postwar low level strike aircraft with the Buccaneer. First flying in 1958, the Buccaneer was still flying combat missions over thirty years later.

I can't think of any other carrier aircraft made by Blackburn that wasn't rubbish. I suppose the Ripon, Baffin and Dart deserve some kudos.

 

[Shortround6]

You can blame the government at least partly.
Blackburn had to submit paper plans before they even got money for a mockup.
Mockup has to approved before they got money for prototypes.
Government had plenty of times to cancel the whole thing before it went into production.
It was the government's idea to turn it into a torpedo bomber.
It may have been the government's idea to use the Sabre engine.
Once you decide to use the Sabre engine a 10,000-12,000lb airplane follows.
Once you have a 12,0000lb airplane the size wing you need for a British carrier follows.
Blackburn may not have executed the idea well but you were not going to get a Seafire out of the air ministry requirements.

Blackburn, Fairey, Gloster, Hawker, Supermarine and Westland had all summited proposals and revisions in 1939.
Blackburn may not have been the best but some of the other companies were judged to busy with existing work.
By the time you get part way through 1940 the official requirements wanted a speed 350kts(403mph) which wasn't going to work with any Merlin they even working on in the summer of 1940 so hypothetical Griffon or Sabre were the only two alternatives.

Supermarine proposals of time (1939) were split between a Griffon powered plane with 120 gal of fuel and a Sabre powered version with 186 gal and Westland came up with a Griffon proposal with 220 gals.
Hawker in Feb 1941 came up with a stretched Typhoon when the Firebrand was having trouble in the design stage.
But they had to put a bigger wing on it (and fold them) and stick 264 gallons fuel in it. And they figured that it wouldn't be ready spring/summer of 1942 AND would only use 25% of the parts of a Typhoon so it wasn't going to get them anywhere.

All of these companies were trying to build what the government told them to build. They were in competition with each other. One company did not come up with a design and tell the Air Ministry "take-it or leave it, now give us the money".

 

[Admiral Beez]

How does Petter's Westland Wyvern compare to Blackburn's Firebrand and Firecrest?

If his Whirlwind, Canberra, Gnat and Lightning are any indication I'd like to think, if temporarily seconded to Blackburn, Petter could have made a better Skua. Though he sounds like a terrible person to work with.

 

[Reluctant Poster]

How does Petter's Westland Wyvern compare to Blackburn's Firebrand and Firecrest?

If his Whirlwind, Canberra, Gnat and Lightning are any indication I'd like to think, if temporarily seconded to Blackburn, Petter could have made a better Skua. Though he sounds like a terrible person to work with.

I believe Peter had left Westland before the Wyvern was designed

 

[Admiral Beez]

I believe Peter had left Westland before the Wyvern was designed

He was still on the Westland payroll, but went awol. But I see now that the Wyvern was a Mensford-led design. I always thought the Wyvern didn't share the clean lines of Petter's Whirlwind and Canberra.

So, do we think Petter seconded to Blackburn in 1936 can help the Skua?

 

[Shortround6]

So, do we think Petter seconded to Blackburn in 1936 can help the Skua?

Maybe, maybe not.

Petter did a lot things right. He also did a lot things w..........let's say, not so good, in retrospect.
For the Whirlwind the air intakes to carbs may not have been so hot.
On the Whirlwind prototype the exhaust pipes were certainly streamlined, but running the hot exhausts through pipes (inner and outer) through the fuel tanks and out the back of the wing (and reducing the exhaust thrust) wasn't the best idea by any stretch of the imagination.
Not sure who's idea the Excelsior engine controls were. Made running the controls easy, keeping them adjusted for even a few hours was a problem.
Using the landing flaps as part of the cooling flap to the radiators was certainly innovative and saved parts, cost, and weight.
It also meant you couldn't taxi the plane without overheating the engines unless the landing flaps were down.

Part of the problem he had working with others was that he disliked criticisms of the less that stellar ideas.

Whirlwind had to get special permission to use higher air pressure tires than the RAF used on every other plane to avoid putting ruts in the grass airfields.
Easy to make your plane more streamline if you don't follow the same rules as the other designers ( he got to use smaller rear nacelles to house the smaller landing gear.)

And there was only so much Petter could do if he was forced to use the Perseus engine.
One History says that after the prototype flew a Mercury engine production planes flew with the Perseus because all (most?) of the Mercury production was allocated to Blenheim production. Don't know if that is true. The Wellington and Hampden were probably sucking up the Pegasus engines though?

Part of the problem with the Skua was that ran late. 21 months from flight of prototype to first squadron. IN 1934 when work began they were expecting delivery to start in 1937.
Only 12 were delivered in 1938.
Petter was also busy designing and sorting out the Lysander.

 

[Admiral Beez]

Maybe, maybe not.

Petter did a lot things right. He also did a lot things w..........let's say, not so good, in retrospect.
For the Whirlwind the air intakes to carbs may not have been so hot.
On the Whirlwind prototype the exhaust pipes were certainly streamlined, but running the hot exhausts through pipes (inner and outer) through the fuel tanks and out the back of the wing (and reducing the exhaust thrust) wasn't the best idea by any stretch of the imagination.
Not sure who's idea the Excelsior engine controls were. Made running the controls easy, keeping them adjusted for even a few hours was a problem.
Using the landing flaps as part of the cooling flap to the radiators was certainly innovative and saved parts, cost, and weight.
It also meant you couldn't taxi the plane without overheating the engines unless the landing flaps were down.

Part of the problem he had working with others was that he disliked criticisms of the less that stellar ideas.

Whirlwind had to get special permission to use higher air pressure tires than the RAF used on every other plane to avoid putting ruts in the grass airfields.
Easy to make your plane more streamline if you don't follow the same rules as the other designers ( he got to use smaller rear nacelles to house the smaller landing gear.)

And there was only so much Petter could do if he was forced to use the Perseus engine.
One History says that after the prototype flew a Mercury engine production planes flew with the Perseus because all (most?) of the Mercury production was allocated to Blenheim production. Don't know if that is true. The Wellington and Hampden were probably sucking up the Pegasus engines though?

Part of the problem with the Skua was that ran late. 21 months from flight of prototype to first squadron. IN 1934 when work began they were expecting delivery to start in 1937.
Only 12 were delivered in 1938.
Petter was also busy designing and sorting out the Lysander.

It would have been interesting to see what Petter would accomplish if given strict parameters; single Merlin engine, grass strip capable, etc.