Very interesting!

Would you happen to have some documentation on that device? I'd love to study it's details!

double ignition gives an overall better burn performance, but it's more relevant on small engines than on large bore ones. A 100RPM drop on a 1650HP engine is negligible compared to the same drop on a 150HP. Besides don't give credit to stuff just because you read it on the internet dude, there are several inaccuracies in that "report", which by the way is on the detonation issue..
In a high performance military aeroplane redundancy has priority, especially considering the huge amount of power available.



it's probably because you don't know how to read them. And that's also why many planes now have backup generators.

...so how can they freeze? And even if they did, batteries are not used during flight, it's all fed through the generator. Another thing, they're not continuously charged since they could overcharge. The circuit overload is controlled by means of breakers that... hang on a minute, have a read for yourself: this is the P-51 Pilot's manual, not some random guy's dissertation on detonation
P-51 Mustang Pilot's Manual

browse words like "battery" and read about how the electrical circuit works.. also read the engine turn off procedure and see how you want to switch the plane off. Magnetos go OFF.

It's all down to the kind of aeroplane we're talking about.

again, it's all down to the plane. See what a Pilatus Porter pilot thinks of generator failures ;)

...and again, I don't mean to sound harsh guys, it's just that I'm writing this stuff mostly on the run, no hard feelings, just get your facts right please, again it's for the sake of the sim.

Why don't you point out exactly which inaccuracies you've seen in that report?

Backup generator, APU's etc... not much room to put them in a fighter back then. I know of multi-engined planes having multiple generators.

Why don't you send me an electric schematic of an aircraft of that period with the request to explain it to you? I haven't learned modern high-voltage AC systems but that old stuff is pretty transparent.

First of all, of course you switch mags off, but the sequence differs per engine or situation. I never suggested leaving the plane with mags still on.

I read nothing new in that P51 manual. Very standard tech for that period. I hoped to find something new but that small portion about the electrical system is not interesting. The only thing I like is the automatic manifold pressure regulator, That means in the future P51 drivers in IL2 or SOW will have less risk of wrecking their virtual engine. Maybe the Rolls Royce Merlins have it as well...

Overcharging happens when a voltage regulator fails, not before. A voltage regulator back then was an electromechanical device which dynamically relayed overvoltage into one or more resistors, changing the power into heat. Now i've seen a lot of those old things broken and even nowadays the electronic versions often break before the alternator itself does. Usually those old flight systems operated at 14V or 28V while the battery provided 12V or 24V. The extra 2V or 4V was, and is still used, to charge the battery. A battery won't charge to it's full capacity if input voltage is the same as battery rated voltage.
Now if the voltage regulator fails, you might wreck your battery very soon because electrolysis increases in an enormous rate, producing a lot of heat. But, the battery is a buffer, it usually keeps the increase in voltage within around 50% but it's capacity starts to drop rapidly. Some batteries can burst. If a battery bursts or when it cooks dry, it's capaciting effect stops and the peak voltage can grow with 200% or even 400%! I've seen it happen. One guy touched the lead of a running alternator which normally produced 6 volts, he got a jolt and jumped in the air. I've also seen a very hot and deformed battery which got us all nervous, the alternator provided 18 volts instead of 14 regardless if the mechanical voltage regulator was connected or not. I had to pick four regulators off the shelf, the first three were broken.

That's what those switches are for, Battery on/off is for switching power when you park or want to start, generator off for the safety of your electrical system. The generator provides the power to the plane's systems when running enough RPM, the battery is the buffer which compensates for peaks & jolts which cannot be compensated for by a failing voltage regulator, and heavy undervoltage situations. These can distort the functions or be harmful or even fatal to delicate systems like radio, navigation, instruments or radar.

Remember that generators provide DC and they start to provide a meaningful voltage at higher RPM's than the later DC rectified alternators. The fact that the P51's generator only starts at 1500 RPM while a modern alternator does that at 850, is the perfect proof. It also means that an engine that runs too slow while a lot of electrical systems are running can create a system's wide voltage drop, possibly more than the 2V or 4V, which is more than the margin the electronic equipment was designed for. The battery compensates for those moments, adding up where the generator fails to provide.
Another problem which generators have is the fact they can be used as an electric motor, with the battery providing it's power. A problem alternators don't have. This was the time before the invention of the high-power diode. The voltage regulator had a built-in function to disconnect the generator from the system when generator voltage output dropped below that of the battery.

I think ANY pilot would get nervous if his generator fails ;-)

Pilatus Porter manual from 1972:

http://avsimrus.com/f/documents-16/f...n=download&hl=

Page 1-17.

Have fun!

S!

Good stuff here. At work when the guys flying the propellor planes(trainers/liasion), they do cut the engine by using mixture IMMEDIATELY followed by turning off ignition and hanging the key. Then they consider the engine OFF.

Here a link to the startup & shutdown procedure of the Allison:

http://rwebs.net/avhistory/opsman/pursuit/section2.htm

And here procedures for the P51, Only the D variant is mentioned so it must be the Packard Merlin variant.

http://rwebs.net/avhistory/opsman/pursuit/section7.htm

However, I'm starting a new topic to try and combine as much official manuals of WW2 aircraft we can find.

I'm sorry mate but "we" who? You really switch off your propeller plane by cutting the mixture? That is one helluva dangerous game man.. If I did something like this with my instructor would have kicked my ar$e, you switch off the engine by bringing the engine to idle and cutting both magnetos off, that is like the first thing they teach you..



Most piston planes I've been in involve shutting off the engine by setting the mixture it to idle/cut off, thats why it's called "cut off". The idea is that you starve the engine of fuel, so that you are not left with unburned fuel in the cylinders or manifold. After the engine is off, the mag switch and battery master switch goes to OFF and your safe.

I have mainly flown 172s and 152s but the shutdown/parking checklist was generally something like:


mixture to the idle cut-off position.
fuel selector valve to the "off" position
turn off the master switch
turn off and remove key


A random google turned up this 172 POH in pdf format:

http://www.redskyventures.org/doc/ce...o7-scanned.pdf

It has no standard shutdown checklist but the shutdown due to engine fire in flight emergency procedure starts with mixture to idle cutoff.

The "securing aircraft" checklist does mention electrical first but by that stage the engine has been shutdown.

...so rumours of a "seat of the pants" in the box are exaggerated then...