Battle of Britain film opening sequence.
 

Hi all,

I noticed that during the Hurri's roll over the French refugees, the engine sputters and smokes slightly. My assumption is this was due to the carb running out of fuel in the brief negative G. Weren't all these carbs replaced or modified during the war to resolve this problem? Why would a Hurri in 1969 be equipped with the older style carb?

Cheers,

Greg

For authenticiness? (I'm sure that I've just made that word up!).
Ah, I know, authenticity, that's the word.

Ah yes; Miss Shilling's orifice. :)

Your assumption would be right.

A lady aeronatical engineer, during the war, called Beatrice Shilling, devised an answer to the problem of the Merlin being starved of fuel during inverted flight. She came up with a simple solution of using a metal disc with a hole in the middle that corrected the starvation. Not the complete solution but enough to let the Merlin fly inverted. It was later nicknamed 'Mrs Shilling's orifice.'

RR later solved the problem themselves. But, one should not forget that Mrs Shilling made a very important contribution to air combat with her device fitted in the Merlin. Simple but effective.

Actually, it's not so much fuel starvation as over fuelling. The fuel is regualted by the jet needle which is connected to a float in the float chamber. In normal operation, the float sits on the fuel in the float chamber and regulates the flow into the venturi. Under negative conditions, the float follows the fuel and ends up at the wrong end of the float chamber, thus opening the jet fully allowing unmetered fuel to flow into the venturi causing a ''rich cut''.

If you look closely, you should see a puff of black smoke as the engine picks up as the excess fuel in burnt off. Also, the engine picks up immediately which wouldn't be the case if it was due to starvation.

The loss of the Mosquito at Barton was attributed to a rich cut starting the loss of control, I think.

SGC

Or, was the cause of the accident that the pilot did not maintain positive 'G' during the entry to the maneuver?

Further to PPRuNe Pop's post - there's an excellent piece about "Miss Shilling" in the June issue of Aerpolane Monthly (I would say this months issue, but that'd make it the July issue - why do they do that:confused:confused of blighty)....very interesting read:ok:

Twochai,`google` AAIB+DeH Mosquito....,in summary,badly set-up carburettors...

Good point about the black smoke indication a rich condition. Shoulda thought of that.

:-)

Thanks for the replies everyone.

Smoke during roll
 

If you get to see the Hurricane sequence in "Reach for the Sky" when Bader (Kenneth Moore) takes over at 242 Squadron and gives them a quick demo to make a point, the sequence shows several rolls all of which give a slight cut and black smoke.
The Hurrricane 11 (as in RFTS) would most likely have had a Merlin xx fitted and therefore be liable to the normal limitations with the standard carb set up.

Quite possibly. I was a few miles north aerobatting the Chippy at the time so only saw it on video, but (in my view) respected based aeros pilots who witnessed it were critical of the technique being employed for 'wing-overs'. There was no doubt a carb issue, but was it primary to the tragedy?

twochai No.

Shaggy Sheep Driver
If you wish to read the report of the very thorough accident investigation, click: AAIB Bulletin No: 6/97


FL

Yup, read that thanks FL.