Carburator problems on the D.VII?

[Hauksbee 103]

It seems that every time I go inverted with a D.VII, the engine starts to run rough and sounds like it wants to quit. Did the D.VII have carburator problems in real life?

[Jammer28 0]

Don’t know about the D.VII. I’m sure one of the more knowledgeable folks here could answer that. I do know that the WWII Spitfire carburetor was gravity fed and would almost cut out when flying inverted. 

[Cameljockey 3]

If I'm not mistaken, the carbs were gravity fed and don't like negative Gs or being inverted. Try climbing in the DVII and then abruptly diving. The engine loses power every time.

 

CJ

[Bletchley 8]

Ther Mercedes D.IIIau and BMW IIIa engines both had float-chamber carburettors that would not feed fuel to the engine when inverted. This is true of nearly all the stationary aero engines of both sides.

 

Bletchley :)

 

http://www.hants.gov.uk/shop/product.php?p...at=0&page=1

[Wels 2]

Hello Bletchley,

 

thanks, that is also what i read in all forums, but i still wonder: Which engines or planes were able to fly inverted due to a special carburettor ? If you are fast enough the centripetal forces during a looping will even feed your engine when you are at the top flying inverted, but i do not mean that. I read of the Etrich Taube, where Hirth was able to perform stunts flying inverted with his "Taube" before the war. I heard of special carburettors his, and some other Argus engines were fitted with, and if i think of a pressured tank instead of a fuel pump, the engine should be able to be fed under almost all circumstances, assuming a special carburettor and second "inverted float" with a valve was installed (?) Also Udet writes about flying his Albatros inverted (which was it then, and was there some change to the engine setup?), but losing height quickly - certainly possible he just glided with stopped engine, but reading this it did not make this impression.

 

This would not be possible with a small reserve gravity tank (in german "Falltank") used in some planes, but for the pump-pressured main tank. I also heard of this in-tank float and even have some drawings of the time, but it would not be too difficult to change this technically - did no one do it ?

 

And what about rotary engines ? I think those were indeed fed by gravity, not pressure ?

 

Thanks and greetings,

Catfish

Edited March 25, 2009 by Wels

[Bletchley 8]

Hello Catfish

 

I guess stunt-pilots or others may have had specialised carburettors to prevent the engine cutting out when inverted. The problem with the standard float-chamber carburettors (and they were all very similar in this respect, as far as I can tell), has little to do with pressurisation - the main fuel tank was pressurised to deliver fuel either to a smaller gravity tank and/or directly to the float chamber. Then the fuel in the float chamber was "sucked" (technically, pushed) through a tube leaving the bottom of the float chamber to the fuel jet(s) in the carburettor by the difference in air pressure between the venturi and the float chamber (lower at the venturi, higher in the float chamber). When the standard float chamber was in an inverted position the exit tube was on top, and the fuel level was below it, so no fuel would exit from the float chamber.

 

Rotary engines also had pressurised main fuel tanks (pressurised either by the running engine or by a hand pump, or by a small 'windmill' fixed to a strut known as a 'Rotherham pump'). These normally fed a smaller gravity tank, and the fuel would then be gravity fed from this to the fuel jet in the tampier carburettor. I think the only engine that was 'fuel injected' in any way, with pressurised fuel being fed directly to the engine, was the monosoupapes - they delivered a rich mixture to the crankcase under pressure, and from there to the cylinders to be 'leaned' by fresh air entering via the exhaust valve. Because the mixture was so rich at the crankcase, there was no danger of a 'blow-back' from these engines, and so they could be fed by fuel directly from the pressurised main tank (or at least, I think this is the case - I am writing at the moment from memory, so someone else might have to correct me on this. And so I guess that an aircraft with a monosoupape engine might, therefore, have been flown inverted?).

 

Some of the Maybach engines also had a rather complicated system of delivering fuel to the engine, but from memory I think they all relied on a combination of main tank pressure and a gravity-feed, and I know very little about the Argus engines so they may have had a non-standard carburettor. But the Mercedes engines all, to the best of my knowledge, had a standard-type float chamber carburettor.

 

Bletchley

Edited March 25, 2009 by Bletchley

[Hauksbee 103]

Thanks Bletchley, and Catfish. I guess that's got it. Oh, and Cameljockey too. Lately I'd tried a quick dive and the D.VII spluttered so bad SE-5 got away. [Probably lost him in the ground clutter, but still...] I've found that the best way to deal with it is to do a sharp wing-over. The engine still coughes, but at least you have your nose pointed in the right direction, and gravity is now on your side. It also seems that the engine recovers a little faster.

 

Also, I'm not seeing the famed ability to "hang on the prop". True, the D.VII is more stall-resistant than the E.III or the Pfaltz, but I was expecting more. Much more actually, seeing as so many writers comment on it.

Edited March 25, 2009 by Hauksbee