Merlin negative G cutout too quick?

[klem]

Originally Posted by 41Sqn_Stormcrow

For the document you are right, but unless I am wrong we discuss the carburator and its behaviour here so I think the acceleration at carburator location is interesting. That is why I said the cockpit reading cannot be transposed 1:1 to the acceleration experienced by the carburator.

My thesis is that the acceleration experienced by the carburator can be slightly different for different plane types even if pilot acceleration is equal due to distance differences between plane cog and carburator. I cannot tell however how big this difference could be (basically I do not want to make the calculation ).

I understand the point you are making but I don't think the carburettor location is important. Well, except perhaps in my first point below.

It is unlikely that the accelerometer would be placed at the carburettor location unless they specifically wanted to look only at that issue. The accelerometer would have been used for other tests too. However if it were at the carburettor then, having accepted at what G level the cutout occurs, MG would have to decide how to simulate that in the FM design or calculate a reasonable estimate for their accelerometer wherever it may be located. Just following on from that, a 0.1G level at the carburrettor would be lower than in the cockpit or at the CoG due to the 'moment arm' point you are making so a cockpit or CoG G level could be say 0.15, 0.2, 0.3 -I'm not going to try to calculate it

More realistically, the Accelerometer would be at the pilot position or CoG. Now, I don't know where it is placed by convention but it is highly probable that the same convention was used back then as now and I would guess its the CoG. These were not the 'kite and string' guys of 1912, they were highly qualified experts who, among other things, had won the Schneider trophy and were no doubt sharing knowledge and conventions across the aviation world until a certain Mr Hitler turned nasty.

So, if we can accept say the CoG as the convention (I'm sure an aviation design expert will put me right if not) I will argue that the carburettor location does not matter because:-

It is the cutout itself that is being recorded and it is being recorded using the available instrument, the accelerometer at its conventional location. When the accelerometer is reading 0.1G the carburrettor may be at 0g or 0.05G or -0.5G but that in itself does not matter, the cutout is recorded when it happens and noted using the available accelerometer reference and that reference can be repated in the next aircraft etc.

There is one point to note and that does come back to the 'moment arm' issue. The moment arm (distance from carburettor to accelerometer) may be different in a Spitfire and a Hurricane so there could be minor differences in the cutout reading in the different aircraft but I think that would be quite small.