Legends 08 Video

Interesting Merlin posts

I found the last postings, particularly the one from Merlin Pete, most informative. My Father worked on Merlins during the war (seafires) so I’ve always had a particular interest in the type.
Unfortunately, I missed the engine runs at Flying Legends on Sunday, although I heard them as we were walking the flight line.

Here are a couple of videos from Saturdays Flying legends The originals look fine but YouTube must be using very heavy compression so they are a bit blocky.

Spitfire Mk 1a
http://www.youtube.com/watch?v=hLBpuFof17g

Blériot XI
http://www.youtube.com/watch?v=XOXOrax41v0

I will post some more after i come back from holiday.

Hi all , Nice video Mauld & great display by Jonathon.

Steve

Fantastic stuff. ‘213 is certainly a stunner 🙂

And another sincere word of thanks for your fantastic engine runs at Legends..a great counterpoint to the flying, I just love the pulsing synchronisation (or desynchronisation?) when 2 are running together. Awesome noise, and a lot of very happy looking blokes!

Aha…Miss Shilling’s Orifice !!

Perhaps it’s in response to opening the throttle after coasting over the top of the loop?

This delay is caused by a secondary issue which is what causes the black smoke.
The first effect of negative G is to cause the fuel to go to the top of the float chamber and thus starve the jets at the bottom, so the engine leans out and stops (or tries to). The next stage is that the fuel pump is able to supply fuel at sufficient flow for max power through the forced-open float valves which causes a rich mixture, hence the black smoke.
On unmodified SU carbs during and before the Battle of Britain, the fuel pump was able to supply an almost unlimited torrent of fuel which caused a “rich cut”, thus causing the engine to flood and stop running, and whilst an engine will restart easily after a fuel shortage, it will not do so nearly as easily after a rich cut, or flood.

I don`t know which mark of Merlin this one is, but it will almost certainly have the required modifications, introduced around the start of 1941, which prevent both rich and weak cutting out, but still cause the mixture to go all over the place, hence the smoke. In theory, if you are running at full combat power in negative G with a modified SU carb, it should run with little or no black smoke. (and Jonathan wasn`t, I hope :eek:)

Very interesting to see in such detail on this video.

Pete

Perhaps it’s in response to opening the throttle after coasting over the top of the loop?

Fuel starvation in the Merlin

I’m aware that, as you say, the Merlin would be starved of fuel if a Spitfire pilot put his aircraft into a steep dive. Hence the escape choice of the Me109e pilot being to bunt, knowing that his fuel injected engine would keep going and the Spitfire would begin to stall if it followed without a half roll to negate the affect of G forces on the fuel in it’s carb. I notice on a second viewing of the video that the Spit emits black smoke as it begins it’s dive rather than at the top of the loop as I stated earlier.

A loop is either a manouevre pulling almost no G at the top, or some positive G at the pull out. The Merlin carburettor would not function under negative G, in other words if you stuffed the nose down in a bunt. The Spitfire would have to half roll, pull positive G and then roll out to maintain the fuel flow. That was always my understanding of the situation.

Spitfire loop

Nice continuous footage of the looping Spitfire, it’s interesting to see the classic puff of black smoke at the top of the loop as the G forces act on the petrol in the carburetor, starving the engine momentarily of fuel.

Nice video mate, checked out some others of yours too;)