Spitfire Compared to Hurricane in the BoB

[GregP]

The stressed skin was better vs. machine gun bullets as well -- deflecting a proportion at shallow angles.

Firing trials vs. Hurricane and Spitfire fuselage
Direct astern, 7.92mm AP

Spitfire
49% of bullets were deflected
15% of bullets (or bullet fragments) reached the armour
7% of bullets (or bullet fragments) penetrated

Hurricane
37% of bullets were deflected
61% of the bullets (or bullet fragments) reached the armour
19% of bullets (or bullet fragments) penetrated

The Spitfire's skin was noted as the reason for the higher percentage of deflections.

Source?

 

[Thumpalumpacus]

And when performing fabric repairs, even simple ones, there are environmental (temperature and humidity) considerations when applying dope.

... and gluing wood, for that matter.

 

[MIflyer]

I think it was in the book "Druid's Circle" that described where they were having a problem with a Mosquito that exhibited some vibration at times, but not consistently. It was the squadron commanders' airplane. One day the engineering officer said he was taking the ship up and going to figure out what the problem was once and for all. He dove it into the ground from high altitude and was killed. They later figured out that it was a flaw in the wooden rudder that manifested itself only under a particular condition of humidity and temperature. There was some separation of the structure that swelled and produced the vibration under the right conditions.

 

[FLYBOYJ]

The stressed skin was better vs. machine gun bullets as well -- deflecting a proportion at shallow angles.

Firing trials vs. Hurricane and Spitfire fuselage
Direct astern, 7.92mm AP

Spitfire
49% of bullets were deflected
15% of bullets (or bullet fragments) reached the armour
7% of bullets (or bullet fragments) penetrated

Hurricane
37% of bullets were deflected
61% of the bullets (or bullet fragments) reached the armour
19% of bullets (or bullet fragments) penetrated

The Spitfire's skin was noted as the reason for the higher percentage of deflections.

And those "deflected" bullets - did they still damage structure?

 

[Greyman]

That information wasn't looked at in the test unfortunately -- this was just testing the efficacy of the 4-mm seat armour in each aircraft.

 

[Greyman]

Source?

NOTE ON ATTACK OF ARMOUR INSIDE AIRCRAFT STRUCTURE
R.D.Arm.3.d.
Orfordness Reseach Station, Orfordness
26/2/41

 

[MiTasol]

Former Fitter with No 145 Sdrn, Eric Marsden: "If we'd had nothing but Spits, we'd have lost the fight in 1940. The turn around time on the ground was so poor that Jerry couldn't have failed to get us. The Spit I and II took 26 minutes to turn around, compared to the Hurri's 9 minutes ... that is a complete service -- re-arm, refuel, and replenish oxygen -- from down to up again."

I'll bet a P-39 could have done it in five minutes!

View attachment 680025

Given those ammo boxes can be filled on the ground and are interchangeable between aircraft I would say that is a staged photo to illustrate how much ammo it will hold - especially seeing the guy on the wing is "loading" 50 cal ammo into 30 cal guns.

 

[yulzari]

I won't comment upon comparative servicing between the Hurricane and Spitfire but I do note that no foreign made Spitfire ever existed but the Hurricane was manufactured not only in Britain but separately in Canada, Belgium and Romania.

 

[MiTasol]

Looking at the Spit V maintenance manual and the Hurri II maintenance manuals. The Spit V uses a pneumatic system for the brakes, flaps, guns, cine camera, and retractable landing lamps. The Hurri II uses the pneumatics for just the brakes and the guns.

So the Spit probably required more charging of the pneumatic system bottles than did the Hurri.

I suppose the use of pneumatics in the Spit and Hurri as well as the Mossie reflected a British preference for that over electrics, as compared to US aircraft. Why they did that I do not know. Perhaps cost was a factor. While I worked on USAF aircraft pneumatics, the only aircraft I can think of that used pneumatics for actuators was the F-106, which used high pressure bottles to supply the flight control Feel Force system and the weapons launching system. Pneumatics can be made capable of very fast operation compared to electric or hydraulics., which was a big advantage for launching missiles. Another engineer told me he was supposed to work on the F-106 missile launch actuator but was scared to do so. I asked why and after looking at the manual I had to agree with him. The actuator used what I think was the unique approach of applying the same pressure to both sides of the piston, using the difference in area to determine which way the piston moved. This had the advantage of sending part of the air back into the pressure bottle rather than dumping it overboard, but if you were testing the actuator on the ground and figured, "Shucks, I don't need to hook up the line to the port that sends it back up since I can do that by hand." then that long length of polished solid steel was going to come out of that cylinder and just keep right on going, through anything in its way.

All brit aircraft with pneumatics had engine driven compressors, usually Heywood, so charging the system on the ground was not required unless there was a leak and then that had to be fixed before flight.

 

[MiTasol]

The Hurricanes big advantage was battle damage that required tinwork on a Spitfire was dope and a cloth patch on a Hurricane.

The Spitfire was a magnificent aerodynamic achievement, but not a thought had been given to manufacture and serviceability.

Amen to that. Worst aircraft I have worked on for structural restoration. Lots of small fiddly parts that are in hard to access locations. Access panels were the absolute smallest they could get away with so servicing was also difficult.

 

[SaparotRob]

Amen to that. Worst aircraft I have worked on for structural restoration. Lots of small fiddly parts that are in hard to access locations. Access panels were the absolute smallest they could get away with so servicing was also difficult.

They could've made them smaller but there was a war on, mister!

 

[MiTasol]

One item I recently read was that an RAF pilot said one thing he really liked about the Hurricane was that it had dual controls. The elevators operate separately, so even if one got shot out you would have the other one. I'll admit that idea never occurred to me.

Crap with a capital K

 

[MiTasol]

Getting a damaged steel tube out of the Hurricane might take a few hours to take the skin off, get the wooden bits out of the way, change the steel tube (bolts) and then replace the formers and start applying the fabric.

Even a grazing hit by a few machine gun bullets might call for the replacement of several of the wood formers and or fairing strips.

Not claiming the Spitfire was bullet proof, just that the claims of ease of repair might be pushing things once we get past the hand full of bullet holes in the skin stories.
You can fly the Hurricane with the bulges in the skin from broken wooden formers since the strength is in the steel tubes. But would you want to considering the loss in performance (extra drag) or chances the fabric would rip with more flutter of the fabric.

Changing any steel tube on the Hurricane is a very major operation. Yes it is mainly bolted but there are also tubular rivets in places. The side diagonals are probably not too difficult but first you must release all the bracing wires in the area which leaves the aircraft in that area all "floppy". The longerons run full length and the cross tubes have end fittings that fit though the longerons. After the tube is replaced then all the diagonal bracing wires must be retensioned in order to square the structure - a long slow job that cannot be rushed.

I much prefer a welded steel cluster joint as it does not have all the bracing wires and mickey motion required by non-welded structures. And replacing in between the clusters is dead easy. Some cluster joints are difficult and some impossible except with jigs but on the other hand if the joint is not destroyed it can usually be scab patched.

The wood formers on the Hurricane were easy to replace once you got the capstrips free but repairing them would require a jig as they have internal structure covered with light plywood. Some of the internal structure was just square stock but a lot was laminated strips and shaped blocks.

As for repairs on the Spitfire - I would FAR rather repair any of the American aircraft.

 

[MiTasol]

Forgot to mention that the woodwork on the Hurricane was essentially in large sections. Most belly sections came off for maintenance but the complete side panels could also be removed relatively easily. The top section includes the large rollover structure behind the pilot and also comes free relatively easily. I do not know if the sides and top were skinned with fabric separately with tape over the joint or if they were all skinned as a single assembly. If the former then a panel replacement would be fairly quick. If the latter far from quick.

From memory many of the cross tubes on Hurricane were ball and socket so easy to replace but that meant undoing a lot of the diagonal bracing wires so that the side frames were able to be jacked apart enough to get the part out/in. But I might be remembering the Hawker Demon. For the rear one or two this would not be possible, and probably not for the first behind the wing.

 

[MIflyer]

Maybe the fabric covering acted like a bullet magnet and diverted bullets away from the metal parts?

Crap with a capital K

From the Hurricane II Maintenance Manual, Section 7, Chapter 1, Paragraph 10:

"10. Fiber fairleads for the elevator and rudder DUPLICATE control cables are mounted between two small L-section members which are clipped between side struts LM...."

"

 

[MiTasol]

yes - duplicate cables but when you look at the elevators themselves they are joined in the middle.

 

[MIflyer]

I think it was Bill Gunston that said you could just about build a Hurricane in your garage, using a hacksaw, vice, files, and other hand tools. But as you describe that does not mean they were easy to duplicate, as these illustrations from the Hurricane Maintenance Manual reveal.

 

[MiTasol]

I think it was Bill Gunston that said you could just about build a Hurricane in your garage, using a hacksaw, vice, files, and other hand tools. But as you describe that does not mean they were easy to duplicate, as these illustrations from the Hurricane Maintenance Manual reveal.

Thanks for those pictures MIF. I have never seen a Hurricane manual so those bring back many memories from 1968/9 in Canada. The good thing is those diagrams clearly show how many of the tubular rivets there are and those are not fun to install. What does not show is that wherever there is a tubular rivet or bolt there is also a tubular spacer inside the structural tubing to prevent crushing/deformation. Getting them in the right position and keeping them there during assembly is what is politely called fun. They also show the various types of plates, brackets, hinges and other mickey motion that the bracing wires are attached to. If the manual does not show the tubular rivet tool the one I used was what looked like a blade screwdriver tip with a handle sticking out the side and a formed end that had a rod sticking out the front of it that was the ID of the rivet. I was fitted to a rivet gun. A little on one end then a little on the other end etc etc etc. Naturally the dolly looked like a heavy version of the snap.

And to keep dissimilar metal corrosion to the maximum most of the tubes are steel, from memory some of the diagonals were alloy, the bracketry was a combination of stainless steel and other steels and many of the internal spacer tubes were alloy.

Gunstan was also somewhat optimistic considering that the tubing is T50 or T55 and that the longerons have to be rolled rectangular in multiple locations. Likewise the ends of the diagonals. When I was involved in creating some of those longerons and diagonals for a Demon we had to build special rollers and run each location about a dozen times to get them to size - using a winch to draw the tube through the roller.

I am sure many here would love to see more from that manual.

 

[MiTasol]

And those "deflected" bullets - did they still damage structure?

That will depend on where they hit. On a skin next to a frame, almost certainly as the skin will deform more than in the centre of a structural panel where the skin can deflect (oil can). In most, if not all, cases the structural damage will be minor.

 

[MIflyer]

As you have described, the Spitfire was not designed for easy field maintenance. Neither was the Merlin. Unlike the V-1710, you could not take the rear accessory case off the Merlin, nor the gearbox, and early Merlins before the introduction of the V-1650 did not even have separate cylinder heads. I guess that since the RAF was focused on defending the British home islands, which are only about the size of South Carolina and North Carolina put together, they figured that the factories would never be too far away.

In contrast, even in locations such as Guadalcanal and India, USN and USAAF field maintenance personnel built "new" airplanes out of piles of wrecked parts.

I recall being astonished when I saw F-18's being produced at St. Louis. I did not know the airplane had a huge bomb bay! But that was not a bomb bay; the whole bottom of the forward fuselage swings open. On the other hand, the Soviets were not big on access panels but preferred to make even very large airplanes capable to being taken apart and shipped back to the factory.