Merlin negative G cutout too quick?

Did anybody ever compare the behaviour at low g of the Spit and the Hurri? My impression is that the Hurri is less sensitive though still quite sensitive.

I too think it is a bit overdone. The slightest dip will lead to a significant performance loss.

I do understand that when you carefully push the stick this will reduce the lateral g from 1g to something like let's say 0.9g or 0.8 g which will lead to reduced hydraulic pressure at the fuel outlet of the fuel tanks hence reducing the fuel flow hence leading to a leaner mixture. Cut-out only should happen when the total pressure at tank outlet (including hence the hydraulic pressure) is equal or less to the necessary pressure for combustion in the cylinder heads plus the pressure losses in the feed lines. Pressure losses are a function of fuel flow and decrease with decreasing mass flow rate as the flow velocity decreases. I though do not know at which g this could happen.

Up to now I just wonder why there was no mechanical blocking of the forward movement of the stick as even levelling out from climb is extremely tricky.

Just to get me right: If it was historically this sensitive I wish to keep the effect. Currently I have some slight doubts.

[jdbecks]

Originally Posted by 41Sqn_Stormcrow

Did anybody ever compare the behaviour at low g of the Spit and the Hurri? My impression is that the Hurri is less sensitive though still quite sensitive.

I too think it is a bit overdone. The slightest dip will lead to a significant performance loss.

I do understand that when you carefully push the stick this will reduce the lateral g from 1g to something like let's say 0.9g or 0.8 g which will lead to reduced hydraulic pressure at the fuel outlet of the fuel tanks hence reducing the fuel flow hence leading to a leaner mixture. Cut-out only should happen when the total pressure at tank outlet (including hence the hydraulic pressure) is equal or less to the necessary pressure for combustion in the cylinder heads plus the pressure losses in the feed lines. Pressure losses are a function of fuel flow and decrease with decreasing mass flow rate as the flow velocity decreases. I though do not know at which g this could happen.

Up to now I just wonder why there was no mechanical blocking of the forward movement of the stick as even levelling out from climb is extremely tricky.

Just to get me right: If it was historically this sensitive I wish to keep the effect. Currently I have some slight doubts.

Your misunderstanding as to why the engine cuts out during negative G maneuvers.

Naw naw. I understand why the engine cuts out under NEGATIVE g manoeuvers.

The thing is I don't understand why any slight push of the stick should lead to negative g

You only get negative g when the total acceleration acting upward exceeds gravitational acceleration in horizontal flight. I don't see why this should happen at any slightest forward move of stick even in horizontal flight ... but perhaps you can enlighten me.

[klem]

I hope to get into the library this week but please don't hold out too much hope on that as if there were a publication I'm sure someone would have popped up with it by now. The chances of bumping into a Hurricane pilot are extremely thin!

However, on this general subject, a small point for the devs:

To confirm the reversed Rich/Lean problem, if you open an info Window you can see that the Hurricane lever in the rear 'Rich' position is giving 0% Rich and in the forward 'Lean' position is giving 100% Rich. You get the same results whether you are using an Axis or Keys for your mixture control. I assume that is what is feeding into the simulation and its not just showing my Axis position.

On the Rotol prop Hurri FT-N, when you close the throttle it pushes the mixture lever to the rearward opsition, i.e. Lean not Rich (remember its backwards) which is not what you want when starting the engine, you want Rich, and I have to move the Throttle forward to around halfway up the Rich-Lean gate so that I can move the mixture lever out of fully Lean to start the engine. My point for the devs: Strangely, when I then close the throttle the info window shows the mixture doesn't change until I give my axis a slight tweak when it goes to 0%. Just another tweak needed when they can.

Rich for the Spit should be forward and Lean backwards. It just reads the wrong way in the cockpit model. Physically it is correctly implemented.

[klem]

Originally Posted by 41Sqn_Stormcrow

Rich for the Spit should be forward and Lean backwards. It just reads the wrong way in the cockpit model. Physically it is correctly implemented.

I'm sorry but that's wrong:

http://spitfiresite.com/2010/07/anat....html/03it_001

also some 'gathered' notes checked over by a Spitfire pilot
http://forum.keypublishing.co.uk/arc...p?t-72714.html

Also this is from the A2A Simulations "Accusim" Spitfire which seems to be a well repsected simulation of the Spitfire MKI amd MKII which particularly models engine behaviour, wear etc.:

Mixture Controls - The Mk I and II have an automatic mixture control which will weaken (lean) the mixture as height is increased, regardless of whether the mixture control handle is set rearward to RICH, or set forward to WEAK (lean). If the mixture control handle is set to WEAK an extra weak mixture will be provided with a 3% drop in R.P.M. DO NOT use the extra-weak mixture at more than +2 ¼ lbs./sq. in. Boost.

As you'll know the Spitfire has two position mixture control, unlike the Hurricane which is adjusted by hand and again the Rear position is Rich.

The actual effect on mixture is reversed.

Mh. I thought to have read in the Pilot's note of the Spit that mixture should be forward for rich. I try to find this passage.

EDIT: You're right. I must have mixed some stuff up. The pilot notes say richt is backwards and lean is forwards. So actually the lever positions in CoD are wrong.

PS: However I know how mixture ratio works for the early Merlin nonethelss

I understand what you want to say and I agree to it when it boils down to simulate ingame the thing.

I would like to know now if the cut out was an either on or off event with nothing in between.

Here is the drawing:


Is this pre- or post-modification?

As far as I understand the floater shall restrain fuel from flowing into to chamber when negative g's occur. That's above all in terms of function I can see.

Depending on the damping due to hinge friction my guess is that initially the floater will go up when one pushes the stick forward due to inertia that forces all objects to remain in the state they are until the forces get the better of them. So when it shortly gets up it will reduce the pressure loss at the reservoir entry by opening it. Hence more fuel will flow into the reservoir for a short time.

[klem]

Originally Posted by 41Sqn_Stormcrow

I understand what you want to say and I agree to it when it boils down to simulate ingame the thing.

I would like to know now if the cut out was an either on or off event with nothing in between.

Here is the drawing:


Is this pre- or post-modification?

As far as I understand the floater shall restrain fuel from flowing into to chamber when negative g's occur. That's above all in terms of function I can see.

Depending on the damping due to hinge friction my guess is that initially the floater will go up when one pushes the stick forward due to inertia that forces all objects to remain in the state they are until the forces get the better of them. So when it shortly gets up it will reduce the pressure loss at the reservoir entry by opening it. Hence more fuel will flow into the reservoir for a short time.

That design is post-production and covered in Viper2000's excellent post here:
http://forum.1cpublishing.eu/showpos...0&postcount=94
Especially read the pasted in section headed 'Appendix VI'

What is the function of the needle like thing? It doesn't seem to do anything. Also without the floater valve (K) what did the floater do?