Armor Protection and Self-Sealing Tanks

[ohogain]

When did armor protection and self-sealing tanks become standard on fighter aircraft? For instance, the Gloster Gladiator did not have either, if I'm not mistaken, nor did the Seversky P-35, and I'm not sure, but I don't think the Curtiss P-36 did, either, so it looks like it was immediately before WW2 that both became common. The P-38, P-40 and P-51 all started out without armor or self-sealing tanks. In rough numbers, what kind of weight penalty did armor and self-sealing tanks impose on the aircraft?

 

[stona]

On Hurricanes and Spitfires armoured windscreens, pilot armour and self sealing tanks (only one of the two on the Spitfire) started being fitted/retro fitted around the outbreak of the war (for the British). I can give you specific dates for these modifications later.

The Air Ministry did not consider armour for the pilot to be necessary as it didn't believe another fighter would be able to get behind one of its new high speed fighters. Luckily for many RAF pilots a certain A.C.M. Hugh Dowding did not agree.

Cheers

Steve

 

[Greyman]

I don't think the P40 started out with armour standard, did it?

 

[oldcrowcv63]

From what I've read in R.S Dann, the P-40 (Tomahawk I) armor began to appear in the P-40B (or C?) (Tomahawk II) models. I didn't realize any unarmored 'P-40' variants had been in combat but evidently the RAF RCAF flew some Tomahawk I's in combat as CAS a/c, with some used as recce a/c. AHT seems to suggest that armored P-40B/Tomahawk IIAs began to appear in late 1940 for the RAF and early 1941 for the USAAC.

 

[davebender]

Armored fuel tank and self sealing fuel tank are two different things. However it's possible for fuselage mounted tank to have both characteristics.

 

[Lefa]

As I remember rigth the P-36 was the pilot's armor protection, but only 8 mm thick (1/3 ").
The Finns removed armor around the same time when they changed the cowling machine-guns in 12,7 mm machinegun (0.50 ").

Reason of the Removal was, close shot the 7.62mm machine gun passed through to the armor.

Edit!

 

[fastmongrel]

Most early protection was just splinter and fragment protection I dont think proper protection came along till about mid war and even then it was probably only heavy machine gun resistant. I dont think any WWII fighter pilot or fuel tank was protected from cannon fire apart from maybe the late war FW190 bomber interceptors.

 

[stona]

Initial Spitfire armour, factory fitted as of February 1940, was the fixed plate behind the pilots head and the removable plate behind the seat. Further armour, under the seat and behind the pilot's lower legs, wasn't fitted until late 1942 (would have to check for a date).

That initial plate weighed over 70lbs, but the biggest speed penalty was incurred by the externally fitted armoured windscreen. Then there was the sheet of aluminium 'deflection'armour fitted externally over the fuel tank. It was only an eighth inch (3mm) thick, but it is visible and most model/modellers miss it. The pilot armour plate was quarter inch (6.5mm) behind the head and three sixteenths of an inch (4.5mm) behind the seat. Someone else might know what that sort of steel armour could or could not stop.

Putting a material like 'Linatex' in or around a solid metal fuel tank and calling it self sealing was a bit optimistic, though better than nothing. Solid tanks still tended to be burst by the energy of the projectile passing to the tank and its contents. The entry and exit holes were not really the problem. This was only overcome later with self sealing soft fuel cells or bags.

Cheers

Steve

 

[Shortround6]

The Russian I-16 may have been the first fighter (aside from WW I trench strafers) to have pilot armor but in general it was not until late 1939 and early 1940 that European fighters began to be fitted with both types ( pilot and fuel tank) of protection. As mentioned above some was better than others and protecting against rifle caliber hits was much easier than protecting against large caliber weapons. By some point in 1941 the US caught up and any plane not fitted with protection was pretty much classified as a trainer. Pilot armor could be a bit thinner than ground (armored vehicle) armor as the bullets that hit the pilot armor often had to go through the aircraft structure to reach the pilot armor. This had various effects. The US .50 cal being rather noted for the bullets 'tipping' between going through the aircraft skin and hitting the pilot armor. bullets don't penetrate well when going sideways

Pilot protection effectiveness depending on type of gun and type of ammo used, angle of impact, intervening structure and equipment ( a number of pilots may have been saved by their radios) and so on.

 

[Greyman]

Bullets hitting the aircraft skin at shallow also deflects a lot more rounds than most people realize, I'd bet.

Stona, are you sure the 'over 70 pounds' is just the rear pilot armour?

The two figures I have are 41.0 pounds and 41.2 pounds (this is pre seat-extension armour which added another 6-mm plate at 8.5 pounds).

The closest I can get to 70 pounds is the windscreen armour and the cowling 'armour' sheet, which added together is 69.0 pounds. This combination was often refered to as 'Pilot Armour' before work on the rear armour started in earnest, and this early nomenclature might be what threw you off.

 

[stona]

The 73 pounds is the weight of the various steel armour plates. This includes the removable plate behind the seat, the fixed head armour and the plate protecting the glycol header tank. It doesn't include 'external' armours such as the aluminium armour over the upper fuel tank or the laminated 'armour glass' bolted to the windscreen.
This all contributed to the roughly 350lbs of extra weight that the Mk 1s being delivered post Dunkirk had put on compared with the earlier ones as they had been delivered from the production lines.
Cheers
Steve

 

[Greyman]

The figures I have are:

- 10.5 pounds for the header tank plate
- 14.7 pounds for the rear head plate
- 26.5 pounds for the rear body plate
- 8.5 pounds for the rear extension plate
- 30.0 pounds for the ammunition tank plates

 

[stona]

The extension plate and ammunition box armour were not fitted in 1940. Maybe my 'internal armour', Dr Price's description, not mine, includes the windscreen which did become internally fitted ?
Cheers
Steve

 

[stona]

Bullets hitting the aircraft skin at shallow also deflects a lot more rounds than most people realize, I'd bet.

Tests conducted at Orfordness indicated that both .303 and 7.92mm AP bullets had some problems penetrating the structure of a Blenheim bomber. Both guns were fired at a range of 200 yards (180m) through the rear fuselage at the 4 mm armour plate protecting the rear gunner, which was angled at 60º to the line of fire. Only 33% of the .303" rounds reached the armour (the rest being deflected or absorbed by the structure) and 6% penetrated it. In contrast, only 23% of the 7.92 mm bullets reached the armour, and just 1% penetrated.
Cheers
Steve

 

[Greyman]

The extension plate and ammunition box armour were not fitted in 1940. Maybe my 'internal armour', Dr Price's description, not mine, includes the windscreen which did become internally fitted ?
Cheers
Steve

This could also include the fireproof bulkhead, which I've seen many sources include in the 'armour' category for the Hurricane and Spitfire.

 

[stona]

This could also include the fireproof bulkhead, which I've seen many sources include in the 'armour' category for the Hurricane and Spitfire.

Good point, though that was a late 1940 modification it might be included.

Cheers

Steve

 

[Lefa]

Did any found of the P-36 armor thickness. I can not find the place where I read it sometime.
The page was the Finnish and it's pretty official page, not a blog.

Does anyone know, Juha?

 

[Juha]

Sorry Lefa
I didn't find that info from the papers of the 2 Hawk 75As I looked, only that self-sealing for Hawks was ordered on 10 Sept 41 and the removal of the pilot's 2-part back armour was ordered on 24 Dec 43. The two 12,7mm Colt Brownings were installed into noses during the summer of 43 in the cases of Cu-502 and -575. Some CUs had got Berezinas already in 42 but that installation was problematic.

Juha

 

[ohogain]

http://www.wwiiaircraftperformance.org/f4f/f4f-3-detail-specification.pdf lists the armor plate for the F4F-3 to be 155 lbs., but it doesn't specify what is included in that number.

 

[Garyt]

Tests conducted at Orfordness indicated that both .303 and 7.92mm AP bullets had some problems penetrating the structure of a Blenheim bomber. Both guns were fired at a range of 200 yards (180m) through the rear fuselage at the 4 mm armour plate protecting the rear gunner, which was angled at 60º to the line of fire. Only 33% of the .303" rounds reached the armour (the rest being deflected or absorbed by the structure) and 6% penetrated it. In contrast, only 23% of the 7.92 mm bullets reached the armour, and just 1% penetrated.

Interesting, Stona.

In answer to the original question, how much did self sealing tanks and armor add as far as weight goes - I've read the hellcats armor added 200 pounds. I wonder how accurate this is, as 200 lbs does not seem to mean much on a plane that empty weighs 9500 lbs. I think I recall reading somewhere that this was also about the weight of self sealing fuel tanks.

Seems for something like the Zero, an extra 200 pounds for the tanks would make sense, though they may have their range reduced. Seems as if the Japanese preferred range over anything else.

I'd also add that the "weight" of armour and self sealing tanks would be extremely variable. Armor would vary based on area covered and thickness of course. Both an A6M3 Zero and the Hellcat had armor - though I'd guess the Hellcat's armor covered more and was thicker, and of course weighed more.

As far as self sealing tanks go, I know Japanese had kind of an "interim" self sealing fuel tank, not as effective as the US but I think lighter. It did not equip Zeroes of Vals or Judys, but some of the mid war fighters. It's late war planes had self sealing tanks that seemed to perform and weigh similar to the US ones.