The R.A.F's fighter defence aircraft saving Malta

[Guns'n'Props]

Another factor one may overlook (being aircraft enthusiasts) is AAA. According to the History of the Royal Artillery In Malta by Dennis Rollo, by mid '42 there existed a rectangle stretching roughly between the Grand Harbour and Ta' Qali airfield in which 80+ 3.7 and 4.5 inch heavy AA guns could be brought to bear. Now in actual terms that's only about 5 miles by 3miles max but the concentration of guns putting shrapnel into that bit of sky was said to be greater than that protecting London.Basically even without the RAF in the air the skies over Malta could be rather dangerous.

 

[Glider]

I totally agree with the previous two postings. During the month of April the AA gunners excelled themselves. With Ammunition resupplied from the MW10 convoy, two years of daily practice and the massive attack on the airfields, the weight of the defence fell on their shoulders.
In April they were credited with 102 victories, 12 probables and 69 damaged whilst the fighters were credited with 53 victories. It wasn't all one way with 100 AA gunners being killed during the attacks.

 

[pbfoot]

The following is a little snippet from a book I'm reading from library the speaker is
John McElroy RCAF finished war with about 15 E/A and his time on Malta



"And some of those raids! You no sooner call "Hello Condor-Tigers airborne". When he would come back with "Go to 20 Mac I have 80 plus for you" That was enough to scare the daylights out of the four of you...

....and Jimmy Ballantyne , whom I found floating in a dinghy one day out 20 miles from home I stayed with him for nearly an hour giving him cover , and knocked down a Me 109 that came to close . Meanwhile Jimmy was practicing back dives off his dinghy into the warm Mediterranean and thumbing his nose at me every time I went by......
'....Some compensation for months of two meals a day , dysentary , no beer, and 5 smokes a week!

 

[Goofy]

Very interested in Malta as well, I recently received a log-book of a 229 Squadron pilot, flew in Malta from the end of 42 till the invasion of Sicily in 1943, very interested reading and loads of annotations on engagement where the odds where 1:3, he was quite thrilled by it though. "Spitfires over Sicily" by Brian Cull is another good book!! Here are some pages of the log-book....

 

[Guns'n'Props]

I'm not too sure how true this is but I heard that pilots were meant to hand in their log books to the RAF.
Unfortunately some time after the war the Air Ministry supposedly burnt quite a lot of them. Luckily many a pilot hung on to his log book(s).

Have you heard anything similar or to the contrary ?

 

[Nikademus]

Another factor one may overlook (being aircraft enthusiasts) is AAA. According to the History of the Royal Artillery In Malta by Dennis Rollo, by mid '42 there existed a rectangle stretching roughly between the Grand Harbour and Ta' Qali airfield in which 80+ 3.7 and 4.5 inch heavy AA guns could be brought to bear. Now in actual terms that's only about 5 miles by 3miles max but the concentration of guns putting shrapnel into that bit of sky was said to be greater than that protecting London.Basically even without the RAF in the air the skies over Malta could be rather dangerous.

Agreed. AA tends to get overshadowed because their success factor tends to be limited in many views to actual kills vs. the broader impact of AA on enemy air formations. (aka....breaking up raids....thwarting attacks.....impeding accuracy etc etc)

For example, For the 1940 -41 period I confirmed 27 Axis planes brought down. (there were probably more but these represent kills that could be traced directly or indirectly to AA damage). On the face it seems paultry....but AA remained critical in importance and was instrumental in thwarting the Axis attacks during the "Illustrious blitz" in particular.

AA was often most important in what it prevented from happening.

 

[Goofy]

No...pilots could keep their log-books, the ones you are referring to are the ones that were left after crews were KIA, these logbooks went to the RAF depository and labelled. The family could claim them. Some 20 years ago all the unclaimed ones (must be some 40 to 50.000 were all destroyed.......

 

[Goofy]

Actually it was 6500 feet of shelving...see this link...it will make you cry...get some hanky's.....

Aircrew Logbooks

 

[Guns'n'Props]

On the face it seems paultry....but AA remained critical in importance and was instrumental in thwarting the Axis attacks during the "Illustrious blitz" in particular.

AA was often most important in what it prevented from happening.

I was lucky to be acquainted with a certain Richard Everson who served in Malta between 40-43 with the 11 Heavy Artillery Regt (I believe) Royal Artillery. Richard once described how the gunners were ordered to create a "creeping" barrage over the Illustrious that swept an arc and changed altitude. Other HAA units would be doing the same thing but at different altitudes and arcs. Consequently they were able to cover a large volume of sky effectively.

Unfortunately Richard passed away last year. He had also served in France and Germany in 44-45.

 

[Guns'n'Props]

Some 20 years ago all the unclaimed ones (must be some 40 to 50.000 were all destroyed.......

Bl**dy hell all that 1st hand material gone up in smoke What a waste. They could at least have put it on micro fiche (or better some computer media) if storage was an issue.

 

[Juha]

Computer wasn't a viable option at that time.

Juha

 

[Guns'n'Props]

Computer wasn't a viable option at that time.

Juha

Yes but Microfiche or microfilm was. A huge undertaking admittedly, but just think of the value of that material etc. What research could have told us

 

[merlin]

Also performance of the Gladiators would be improved as many had been refitted with 3-blade variable-pitch props and with 100 octane gasoline the Mercury could make nearly 1000 hp up to ~9,000 ft.

Off thread - but as same engine - what difference would the changes with the prop. and 100 octane fuel make to the Gloster F.5/34 ??

 

[Shortround6]

Off thread - but as same engine - what difference would the changes with the prop. and 100 octane fuel make to the Gloster F.5/34 ??

Short answer= Not enough.

Longer answer, some sources say the Gloster F.5/34 already was fitted with a 3 blade Vairable pitch prop.

THe best any Mercury engine did with 100/130 fuel was 965HP. It did allow about 2lbs more boost than 87 octane fuel. Air cooled engines never got the same level of improvement from better fuels that liquid cooled engines did. The Mercury's air cooled 1520 cu. in. was just too small to compete with the Merlins liquied cooled 1650 cu in.

 

[fibus]

We should note the role of Sir Keith Park in the Battle of Malta.

 

[vanir]

Also there is a point where boost pressure is limited by cylinder temperatures induced by fluid dynamics rather than octane rating of the fuel, in other words its porting, cam timing, comp chamber and piston crown design, intake piping, etc.
The ideal is to match octane to engine, for an engine to be able to make use of higher octane with dramatic boost increase it has to be a really good engine design in these areas to start with.

As an example the DB-601 started pinging at about 1.55atm on C3 fuel, where the DB-605DB or ASB could handle 1.8atm on C3, both without MW50. The big change here was firstly head redesign and revision of valve timing profiles, then revised piston crowns and chambers to get from about 1.7 to 1.8atm.

It's also noteworthy that octane increase actually reduces specific power output, but provides a net power gain due to other modifications like boost increase and etc. The lower the octane, the more explosive the fuel, so the better power. Problem is of course if the octane is too low you get pinging (predetonation). If it is too high for your engine, what happens is you actually lose power.
At the point where an octane increase can only provide a couple of pounds extra boost, you're probably losing out by using it. Not to mention higher octane tends to oil plugs and corrode valves more quickly, which may reduce serviceability, and the modifications associated with higher octane can otherwise dramatically increase the stresses on the engine.

Put simply you need a pretty special engine to be able to vastly increase octane and supe it up for a dramatic performance increase. The generally accepted method is to properly redevelop or re-engineer the motor on the workbench and place a higher performance derivative into production.
Engines like the Merlin, Allison, Daimler, these were pretty special cases as they were all ultimately based on mid-thirties racing motors and introduced production techniques in the same way Honda 1.6 V-tec is based on formula 1 technology and is nothing like a Datsun 1600, or a Flathead is nothing like a Can Am racing Cleveland.
In something as small and light as a Gladiator you would apparently really feel what is probably a marginal increase in engine output for some loss in serviceability, but in this case survivability was much worse if you didn't take some measures.

Also noteworthy is that octane and boost increase tends to lower the critical altitude of a given engine. In the Daimlers you lose up to 1km of critical altitude by going from B4 to C3 with an associate boost increase on what is otherwise a fairly identical engine. I'm not sure if this holds true for radial engines, as far as I know the critical altitude of a B4 running 801 is the same as running on C3, but most of the engine/supercharger settings between these two fuel types didn't change. The greatest reason for the fuel change was probably the hot running of the engine in its tight installation, so bench performance wasn't being achieved on B4. Here is the example that cylinder temperatures also have something to say about suitable octane irrespective of other factors.

 

[Shortround6]

It's also noteworthy that octane increase actually reduces specific power output, but provides a net power gain due to other modifications like boost increase and etc. The lower the octane, the more explosive the fuel, so the better power. Problem is of course if the octane is too low you get pinging (predetonation). If it is too high for your engine, what happens is you actually lose power.

I am not sure that this is so. Gasoline can be made-up from a combination of several hundred different chemical molecules. It is quite possiable to get fuel with the same octane rating with widely different chemical compostion. THe BTU rating per lb can vary a bit but has little to do with the octane rating. Octane helps mesure the temperature at which a fuel will auto-ignite. THe lower the octane the lower temperature at which it will ignite with no spark or other source of ignition. Aircraft fuel was blended to have a lower volatility than motor gasoline. The higher the volitility the easier (lower pressure and temperature) the fuel will vaporise and form an explosive mixture. In aircraft they were worried about higher rates of evaporation at higher altitudes.

At the point where an octane increase can only provide a couple of pounds extra boost, you're probably losing out by using it .

I don't believe that this is so.
1. In the case of the Mercury it doesn't agree with the published perfomance figures.
2. It doesn't seem to follow logic. The Mercury with 87 octane fuel was limited to about 4 1/2lb of boost for a total manifold pressure of 19.5 lbs. Using 6 1/2 lbs of boost gives a maniflold pressure of 21.5. just over a 10% increase. This means that the engine is burning 10% more fuel in a given time period. Which should lead to 10% more gross HP. THe Idea that the 100 octane fuel is 10% or more less powerful ( or that much lower in btus per pound) doesn't seem to make sense. Becasue the power losses (internal friction, pump drives, supercharger drive power,etc) stay the same the net power increase should be more than 10%.
EDIT>I would imagine that the BTU per pound of fuel was in the fuel specifications. IT certainly was post-war, otherwise you have to reset the carburator/fuel injection for each different batch of fuel. Using a constant BTU per pound requirement for most fuels would make things easier for everbody; engine designers, fuel refiners and suppliers, mechanics, etc.<edit

Not to mention higher octane tends to oil plugs and corrode valves more quickly, which may reduce serviceability, and the modifications associated with higher octane can otherwise dramatically increase the stresses on the engine.

I beleive you ment "foul" the plugs and not "Oil"

The extra stress on an engine doesn't come from the octane rating but from the extra "boost" when used which dramaticly increases the pressures inside the cylinder which results in higher loads on on the pistons, connecting rods, crankshaft, bearings, crankcase, cylinder hold down bolts etc. and the fact that if you are burrning 10% more fuel you are creating 10% more heat which the cooling system (fins or liquid) might not be able to get rid of.

In something as small and light as a Gladiator you would apparently really feel what is probably a marginal increase in engine output for some loss in serviceability, but in this case survivability was much worse if you didn't take some measures.

While a 10% increase in HP probably didn't make much difference in level speed (5% or less) it probably helped the climb performance a bit more.

Also noteworthy is that octane and boost increase tends to lower the critical altitude of a given engine. In the Daimlers you lose up to 1km of critical altitude by going from B4 to C3 with an associate boost increase on what is otherwise a fairly identical engine. I'm not sure if this holds true for radial engines, as far as I know the critical altitude of a B4 running 801 is the same as running on C3, but most of the engine/supercharger settings between these two fuel types didn't change. The greatest reason for the fuel change was probably the hot running of the engine in its tight installation, so bench performance wasn't being achieved on B4. Here is the example that cylinder temperatures also have something to say about suitable octane irrespective of other factors.

Actually when going to the higher octane fuel the original power rating of the engine doesn't change. See the Merlin III in the Spitfire. On 87 octane it gave 1030 HP at 16,250ft using 6lb of boost. The engine was limited by the supercharger. The supercharger could only supply enough air at that altitude to produce 1030 hp no matter what kind of gasoline was in the tank. When using 100 octane fuel the power at 16,250 ft and above was the same as when using 87 octane fuel. At lower altitudes where the supercharger could supply higher boost the power ratings did go up. THe lower the altitude the more air (boost) the supercharger could supply and the more power could be made until the engine reached either it's cooling limit or it's structural strength limit.
Try graphing the power ratings of Diamler engines in question. Plot their power ratings at altitudes with the end point ( 0 HP) at about 55-56,000ft and see if the HP curves either match or are very close to each other.

AIr cooled engines didn' behave like liquied cooled engines for the Allies either
A bit counter intuitively air cooled engines were known as severe duty engines while liquied cooled engines with much higher boost pressures were known as mild engines.