Inverted fuel supply

[Annette Carson]

In Oliver Stewart's 'Words and Music for a Mechanical Man' he describes intensely experimenting with aerobatics in his Sopwith F1 Camel (110hp Le Rhone) at Orfordness in 1917. "At first I had no inverted fuel system," he reports, "and no one at that time seemed to have any useful ideas on how one could be devised, though ideas flowed soon afterwards when ‘cigarette tin’ inverted systems allowing several minutes of inverted flight with full power were introduced." I wonder if any member has come across this 'cigarette tin' inverted system and can explain when it was developed and, more importantly, how it worked?

 

The subject of my biography, D.V. Armstrong, had a second Rotherham fuel pump installed on his Le Rhone Camel in 1918 and it seems logical to associate this with the regular displays of aerobatics he was detailed to perform. It would be enlightening to know whether anyone has come across any other Camel similarly fitted. 

 

Thanks for any ideas or suggestions.

 

[Interested]

This is my opinion, others more expert might provide a different explanation: The Camel fuel tank sat behind the pilot seat close to the centre of gravity so that fuel consumed wouldn't affect flight balance.  The tank was pressurised initially by a hand pump and also by an air-driven pump, and the fuel feed to the carburettor/engine came out of the bottom of the tank.  Before the modification, when flying inverted the fuel ended up at the top of the tank and air at the bottom so no fuel would reach the engine.  They then fitted a small auxiliary tank above the main tank, fed from the pressurised main tank, and from which a second engine feed was taken.  This auxiliary fuel tank had a feed pick-up that worked OK when inverted.  The pilot had a control to switch between the main tank and the auxiliary tank, so I assume he had to "flip the switch" as he approached the inverted position, and remember to switch it back later.  If the engine cut out I think the airflow through the propellor would re-start the engine once the fuel flow re-started.

Hope this helps.

Philip

[Lawryleslie]

The Rolls Royce Merlin suffered similarly in WW2. Spitfire pilots called it "negative G engine cut out" which was exploited by the Luftwaffe pilots in dog fights. Initially partially overcome by an invention by a female engineer at RAE Farnborough called Miss Shilling's Orifice which would allow short bursts of negative G and inverted flight without losing power. The problem was finally overcome fully by the introduction of pressurised fuel injection carburettors that replaced the old SU carbs in 1943.

Edited 7 February , 2018 by Lawryleslie

[Interested]

Ah, the lovely Miss Shilling, a Lady of many talents.

 

 

[Annette Carson]

Thanks, Interested, this sounds a good deal more professional than Oliver Stewart's description 'cigarette tin' - or perhaps that's just what the fliers nicknamed it. I wonder if it had an official name, or indeed whether it was factory fitted? Also, have you any idea when it came into use (bearing in mind Stewart didn't have access to any such aid to inverted flight in 1917)?  Any clues as to whether it was available on Camels in 1918 would be greatly appreciated.

 

I'm still interested to know whether anyone has come across the twin Rotherham pumps I mentioned. 

 

 

 

[Interested]

The problem of fuel starvation when flying inverted would have been a well-known issue to all concerned, I'm sure.  From Oliver Stewart's description is it possible he was experimenting perhaps before full production release?

A temporary solution could have been devised by the technicians possibly using a cigarette tin soldered up to provide a small reservoir of fuel.  Totally my speculation of course, I have no proof of any of this, sorry.

The production arrangement I described above was a properly engineered solution, not "Heath Robinson" in any way.  I don't know when it would have been introduced though.  As far as I know, the Camel Mark F1 was the model supplied to all RNAS and RFC Squadrons on the Western Front from June 1917 so I'm assuming they all had the dual tank arrangement.

I reiterate, I'm no expert, so I think more research is needed if you want a definitive answer.

[Annette Carson]

I'll check with my current Camel pilot source, but he didn't recognize any such aid to inverted flight when I mentioned it. Yes, Oliver Stewart was given a free hand to experiment to his heart's content with his tame Camel at Orfordness, but if he had nailed together an auxiliary tank he would certainly have said so. That he fails to say whose ideas 'flowed soon afterwards' is a clear indication that they weren't his!  I'm glad to know this was factory engineered as it ought to make identifying it that little bit easier. Many many thanks for the insights. 

[Annette Carson]

I've just returned to my research notes for my history of aerobatics (never a bad idea) and I see that a team of test pilots was set up at the RAE in 1919 to investigate negative manoeuvres, prompted by a spate of Camel accidents involving inverted spins. I suspect it was tests carried out here that probably led to devising the auxiliary tank you describe. I'll see if I can find out more.

[Interested]

Interesting problem!  If Camels were going into spins during inverted flight, it suggests to me that inverted flight in itself wasn't a problem, i.e. the auxiliary tank was being used.  Then you would need to ask what causes a spin when flying inverted, and what action a pilot needs to take to recover controlled flight.  The aerodynamics of this is a bit beyond me, I'm afraid, so you'll need to find someone who can answer this - a stunt pilot would probably know all about the problem.

[Annette Carson]

On 08/02/2018 at 20:30, Interested said:

The problem of fuel starvation when flying inverted would have been a well-known issue to all concerned, I'm sure.  From Oliver Stewart's description is it possible he was experimenting perhaps before full production release?

A temporary solution could have been devised by the technicians possibly using a cigarette tin soldered up to provide a small reservoir of fuel.  Totally my speculation of course, I have no proof of any of this, sorry.

The production arrangement I described above was a properly engineered solution, not "Heath Robinson" in any way.  I don't know when it would have been introduced though.  As far as I know, the Camel Mark F1 was the model supplied to all RNAS and RFC Squadrons on the Western Front from June 1917 so I'm assuming they all had the dual tank arrangement.

I reiterate, I'm no expert, so I think more research is needed if you want a definitive answer.

Forgive me if I'm doing you a disservice, Interested, but on re-reading your description it sounds to me as if you're describing the Camel's gravity tank (capacity 32 litres). This was part of the standard design. The standard Camel was capable of about half a minute of inverted flight, and indeed Oliver Stewart had this at his disposal. Stewart was referring to a later modification when he spoke of the 'cigarette-tin' arrangement, i.e. something that wasn't available to him in 1917/18. 

 

The RAE team were investigating why the aircraft had a tendency to (accidentally) spin inverted, not that spins occurred when flying upside-down. It's a truism that accidental spins were frequent with rotary engines, and avoidance and recovery procedures were learnt early on, but the Camel's specific design (CofG, instability, etc.) accentuated the rotary's precessional forces which meant that a mis-handled Camel, or one buffeted by wind, could easily flip over and spin inverted. A very fine touch was needed in control inputs including spin recovery. Many spins, whether inverted or upright, were secondary spins, i.e. caused either by over-compensation in initial recovery inputs or by the pilot's eagerness to pull out early instead of waiting until the correct angle of attack for normal flight was achieved. Aerodynamics were imperfectly understood at the time, and pilots usually thought in terms of 'flying speed' and 'stalling speed', which was why  tests like the RAE investigations were new and valuable in the understanding of airflow. I've located a selection of their reports but most aren't digitized and would necessitate a visit to Farnborough. Rather outside my budget when I don't even know whether the 'cigarette-tin' idea originated in that context!

 

Armstrong's second strut-mounted 'windmill' pump might have been for redundancy, since in a steep dive the single standard pump could sometimes fail to raise fuel tank pressure sufficiently to overcome the rapidly increasing atmospheric pressure, and a busy pilot would rather not change hands on the stick in order to operate the hand pump. And pilots also liked having it in sight to check it was still present and working! Or it might JUST have been to pressurize a private-enterprise fuel system for more sustained inverted flight, who knows? The twin windmills haven't been encountered by the Camel experts I've asked, but the pipework would need some engineering skill.

 

Anyway, thanks to those who've been kind enough to discuss this. 

Regards, Annette

 

[Interested]

Farnborough is just down the road from me, and I have a colleague who was with the RAE with whom I play bridge weekly (or should that be...weakly!).

If you have a contact there and would like to set up a meeting for me to grill someone, or look in the library, let me know and I'll see what I can do.

Anything to help.

Regards,

Philip

[Annette Carson]

Philip this is uncommonly good of you. I do indeed have a contact at Farnborough who is also being helpful beyond the call of duty. IIRC he said he went there on a weekly basis (not weakly I hope!) so I suggest I email him and ask his agreement to get together with you. I think he's identified about three reports from the period I'm thinking of. Your additional insight into what I hope to find could be very valuable. I'll get back to you. 

[alex revell]

On a lighter note. I showed the story about the talented Miss Shilling to my wife. Being interested in motorbikes she was interested in the actual bike Ms Shilling was on. She pointed out the strange, unusual  frame. Anybody any idea what make of bike it was.

Incidently, I've had a great deal of trouble  in attempting  to write and post this reply. The usual method of reply to this post just took me to a link which only showed the Submit button but no space to write a reply. Contact Us gave exactly the same, leaving me no possible way to ask for help. Yes, I was signed in in both instances. Only solved by  it by going to Long Long Trail and then clicking on its Back to Forum link

Edited 19 February , 2018 by alex revell
extra words

[pete-c]

Looks to me like a Norton (International) - circa 1935 - rigid frame with girder front forks.

Edited 19 February , 2018 by pete-c

[Interested]

It's a bit of a digression and the Mods might pull it for wasting time and space, and being post-1918, but here's another of Ms Shilling in competitive mode.

I think it is at Brooklands, given the fishtail exhaust.  A cammy Norton?

 

 

[alex revell]

Hi Pete-C and Interested. Not be able to thank you before this for your posts because I have been unable to reply to posts or initiate new ones. My thanks to the admin people for resolving this problem.

Alex

[pete-c]

40 minutes ago, alex revell said:

Hi Pete-C and Interested. Not be able to thank you before this for your posts because I have been unable to reply to posts or initiate new ones. My thanks to the admin people for resolving this problem.

Alex

 

No problem Alex.

 

Peter.

[Annette Carson]

On 18/02/2018 at 20:30, Interested said:

Farnborough is just down the road from me, and I have a colleague who was with the RAE with whom I play bridge weekly (or should that be...weakly!).

If you have a contact there and would like to set up a meeting for me to grill someone, or look in the library, let me know and I'll see what I can do.

Anything to help.

Regards,

Philip

Hi Philip - Just an update from me. I have a colleague who's interested in some of the other aerodynamic investigations by that RAE team, and if getting digitized copies proves affordable we're going halfsies on the cost. Meanwhile Geoff at Farnborough says he's happy for me to give you his email address in case you would like to arrange to visit the museum and meet him anyway. If so, I'll PM you his address. If your interest doesn't extend beyond checking the records we've been discussing,  stand by for an update, because we may still call on your services if these reports lead to further investigations!!!

Best regards, Annette

[Interested]

Hi Annette - Looking forward to helping, if I can.  Of course, being inquisitive I recently googled and found John S Shaw's website (johnsshawaviation.co.uk) but unfortunately I can't tell where he's based.  He builds replica Camels using period parts (and I notice he's built a reproduction hand-pump for priming the fuel tank prior to flight) so he probably has a diagram of the fuel feed set-up, and might be able to help with your search too.

Philip

 

[Interested]

Hi Alex,

Your thanks are appreciated, and I'm pleased to help where I can.

BTW, I think most of the British pre-WW2 bikes had girder forks and rigid back ends, although BSA might have had a rear sprung hub.  I had a circa 1935 150cc Francis Barnett like that once.

Philip 

[Annette Carson]

24 minutes ago, Interested said:

Hi Annette - Looking forward to helping, if I can.  Of course, being inquisitive I recently googled and found John S Shaw's website (johnsshawaviation.co.uk) but unfortunately I can't tell where he's based.  He builds replica Camels using period parts (and I notice he's built a reproduction hand-pump for priming the fuel tank prior to flight) so he probably has a diagram of the fuel feed set-up, and might be able to help with your search too.

Philip

 

Yeah, I'm familiar with John S. Shaw's build ... and with the Shuttleworth Collection Camel and its pilot Dodge Bailey. The trouble is that people who build / restore historic aeroplanes with original engines don't make them available for aerobatic flying, least of all flying upside down! My late friend Brian Lecomber, for all his credentials and experience, gave up experiments doing anything tricky with the (Warner Scarab) Camel he was displaying, for the simple reason that the moment you substitute an engine it wasn't designed for, you introduce airframe stresses in places where you never knew you had places. And even though Dodge is an engineer he couldn't offer me an opinion on how one might jury-rig a Camel with an inverted system without some very complex pipe-and-valve-work. However ... the interesting thing is that Captain Armstrong came from a family of engineers and had some years of experience with different airframes and engines. If it were not for that mysterious dual windmill-pump set-up on C.6713 I wouldn't be pursuing this, but hey, what else am I to do with the Beast from the East depositing some inches of snow outside my front door? ;-) 

[alex revell]

Hi Annette, I know this is a very, very long shot, but I've learnt over the years not to make them. Would it be  possible to ask your friend Geoff if there are any photographic records at Farnborough. If so if there is a photograph  of Jimmie McCudden's SE5a C1126 that was built at Farnborough. McCudden took a very hands on approach while the aeroplane was being built and I've always been amazed that he didn't take a photo of it himself, he always took such a lot of aircraft and people. There was one taken by someone who worked at Farnborough, but his son, who knew of it, could never find it. If one could be found it would be like the Holy Grail. :-)

Edited 28 February , 2018 by alex revell

[Annette Carson]

Hi Alex - I've sent you a PM.

Cheers

Annette