P-51 Cockpit

[Sfbagger]

Okay folks,
I'm a newbie here, and this has, of course, nothing to do with shaving.
It's simply a 360 view of the cockpit of a P-51; in my opinion one of the most beautiful warbirds/weapons ever created.
http://www.stclairphoto-imaging.com/360/P51-Mustang/P51_swf.html

Magnificent.

Enjoy.

Jeff

 

[GFlanagan3]

that is awesome! thanks for posting!

 

[firehydrant]

Amazing! Thanks.

 

[ImaWestie]

You can post more of those in here any time. As long as you explain it real well for the dummies.

Like myself!

 

[ginantonix]

Very, very cool! Thanks for sharing.

 

[BCatl]

You can post more of those in here any time. As long as you explain it real well for the dummies.

Like myself!

+1. And me.

 

[Bertilak]

Now that's pretty impressive! Both the P-51 and the 360 degree image.

 

[GDCarrington]

Now that's pretty impressive! Both the P-51 and the 360 degree image.

Yes. She was and is a beautiful winged machine!

 

[vern]

Magnificent!!

 

[gearchow]

That is truly awesome! When I lived in Santa Cruz and the Watsonville Air Show was happening, you would hear the P-51 before you saw it and know you were about to see something cool.

I wish my dad was still alive, he started out wrenching Navy 'reciprocating' engines, spent his whole Navy career in aircraft maintenance. I could ask him this question:

Why does Manifold Pressure (MP) give the plane more get up and go but RPMs don't? (look at the engine limitations panel right hand side)

Wartime Emergency 5min, 3000 RPM, 67MP
Military 15min, 3000 RPM, 61MP
Max Continous, 2400 RPM, 46MP

I always though engine RPM made the blade spin faster which makes the plane go faster.

-jim

 

[lenard]

That was cool

 

[David in Boston]

That was amazing!

 

[evandood]

I am guessing that this is a P51-B, notice the lack of the bubble canopy. I believe the P51-D first had the bubble. The B model was widely used but the D and H are the classic Mustangs.

 

[Obi Wan]

Thanks for posting!

 

[KarthVader]

Awesome! Thanks for sharing!

 

[BladeRunner001]

I love that plane. The P-51 Mustang was one of my favorite planes too.

View attachment 132286

 

[BobK1]

That is truly awesome! When I lived in Santa Cruz and the Watsonville Air Show was happening, you would hear the P-51 before you saw it and know you were about to see something cool.

I wish my dad was still alive, he started out wrenching Navy 'reciprocating' engines, spent his whole Navy career in aircraft maintenance. I could ask him this question:

Why does Manifold Pressure (MP) give the plane more get up and go but RPMs don't? (look at the engine limitations panel right hand side)

Wartime Emergency 5min, 3000 RPM, 67MP
Military 15min, 3000 RPM, 61MP
Max Continous, 2400 RPM, 46MP

I always though engine RPM made the blade spin faster which makes the plane go faster.

-jim

I replied to Jim via PM and he insisted on my actually posting the answer on here so others could read it. I personally don't think it is good enough for the masses, but, I will give you all a chance.


The answer will take a couple of steps, and a disclaimer.

Disclaimer: I am not a pilot, nor an aircraft mechanic, however I do know a thing or two about engines and aircraft in general, and I and my family were in the engine monitoring instrumentation business for 42 years.

A propeller, or prop, has an RPM limit. At a point beyond that limit the prop will fail by actually blowing itself apart. This has to do with the tip speed, the act of constantly changing direction (it spinning remember) and the forces generated at the hub by the blades trying to fly away. If you ever held something fairly heavy and swung your arm around you would feel this effect. Well, the blades are fairly heavy and spinning quite a bit faster than your arm. Plus at some point, the tip speed will exceed the speed of sound, opening up a whole new can of worms.

The engine itself has a limit of RPM where it too will self destruct. This has less to do with rotation itself, but rather the masses involved with the pistons reversing directions at the end of each stroke, and the associated inertia(s) involved.

With this in mind, most aircraft engines utilize an adjustable pitch prop. This allows two things, one the engine will almost always be running at a higher RPM where it is more reliable, (less likely to stall, or sputter) and two, the engine/prop combination will not exceed the limits of their respective components. Sometimes (if not always) this is called a constant speed prop. If the concept of "pitch" is not known, think of two screws, one a machine screw with a fine thread and one a wood screw with a coarse thread. In the machine screw, the screw might have to turn thirty or forty times to travel one inch, where with the wood screw, the same may happen after only ten to twelve turns. Now imagine a propeller as a "screw" that has been machined down to only a few little legs that once were an entire circle around the screw. Now further imagine that the angle (pitch) of said blades could be changed at will. Now you would have a screw that (for a given rotational speed) could be made to drive itself into the material at varying speeds without having to change the rotational speed at all.

Now a short primer on manifold pressure.

We will think in terms of a car engine at this point as it's basically the same as an aircraft for this discussion and besides it's conceptually easy to relate to.

An engine will attempt to draw in as much air as possible during the intake stroke. In order to prevent this from leading to the destruction of the engine, and to allow some form of control over the engine RPM, we install a throttle plate of some type in the intake system. On traditional carburetors this is part of the carb itself, with fuel injection it is part of the throttle body. This has the effect of limiting the amount of air (and by default the air/fuel mixture) into each cylinder, thereby effectively limiting the produced power and indirectly the RPM. On a traditional car this creates what is known as manifold vacuum. The engine is sucking air and we are limiting the flow, thereby creating what we on the ground think of as vacuum. (less pressure than atmospheric pressure) This is a rather intuitive way of thinking for folks on the ground (at or near sea level) The vacuum is usually measured in "inches of mercury" where 0 inches is atmospheric pressure itself, and 30 is a perfect vacuum (more or less impossible to achieve) On some cars there is a gauge to indicate this vacuum, and sometime it's referred to as an "economy gauge" We all know that in general city driving uses more fuel than highway driving due to the need to accelerate to speed. When we stomp on the gas pedal we open the throttle plate and no longer limit the airflow into the engine, this has the effect of reducing the vacuum present in the intake manifold. The engine provides the maximum amount of power for the present RPM, and away we go. While at cruising speed the throttle plate limits the airflow and induces a "vacuum" in the manifold where a balance is achieved, and the speed of the engine (RPM) and thereby the speed of the car is fixed. To achieve some level of economy, we will not simply stomp of the pedal, but rather will only depress it slightly, opening the throttle plate slightly, and cause the manifold vacuum to drop only a little bit. This is why the vacuum gauge is often called an "economy gauge" as if we can train ourselves to apply as little throttle as needed (as reflected instantly on the vacuum gauge) to actually accelerate to the desired speed, we will achieve maximum economy.

Now, we will add a supercharger or turbocharger into the mix. We now have a condition where the air may well be forced into the cylinder rather than simply drawn by suction alone. The same basic principals apply, however, now we can achieve less than 0 vacuum and have pressure instead. If you have ever driven a car with a turbocharger you may have noticed a gauge indicating turbo "boost" This often has a "-30 - 0 - xx" indication and when the engine is off, the needle is at the 0, while running it is somewhere closer to the negative 30 and when applying the throttle it moves toward the 0 then beyond into the positive numbers (indicating boost) The same basic principals apply, and again it is intuitive for those of us on the ground. However, now for a given RPM, we can actually force extra air into the cylinder and create extra power in relation to the naturally aspirated engine.

All this talk of vacuum and pressure is just fine for us on the ground, but in an airplane where the altitude will vary quite a bit, the atmospheric pressure will vary quite a bit as well, so we need a way of thinking that will correctly reflect on the conditions of the manifold in an accurate manner. So we stop thinking of vacuum and simply reference pressure itself, in what is referred to as "absolute" With this system the same basic principals apply, however we now have a gauge that indicates 0 when there is no pressure at all (a perfect vacuum), 30 when we are at sea level, and more when we are in a boost condition (at sea level anyway) So, if we were at an altitude where the atmospheric pressure was only 20 inches of mercury the gauge would indicate 20 while the engine was off, but more than that, it would correctly indicate the level of power that would be achieved at that altitude. As the atmospheric pressure is less, the amount of air that the cylinder receives will be less as well. (for a given set of identical conditions)We now have an overly basic understanding of propeller pitch and manifold pressure. We also understand that there are limits on both the engine and prop in relation to RPM.

(We are in a plane now) So, when we want to go faster, we apply more throttle, and the manifold pressure goes up. This produces more power and attempts to increase the RPM, but the propeller (actually the mechanism in the hub) will respond by increasing the pitch of the prop to limit the RPM and simply take a bigger bite of the air instead. We now go faster. Furthermore, because the RPM is going to be more or less constant in this scenario, the manifold pressure gauge is a direct way to indicate the actual power produced by the engine. As the power has no place to go other than into the prop, and the prop varies automatically, the result is attained speed (in theory at least)

We don't live in a perfect world, and the pilot must maintain an eye on his instruments to ensure that the actual RPM does not exceed the limits, that's why the chart denoting max RPM and also time limits for given RPM and power (manifold pressure) to ensure that both the mechanical destruction of prop and or engine does not happen. (The times may have more to do with heat removal rates than anything else.)

With this little bit of nifty information at our fingertips we can apply our knowledge into something useful. If you take a car, and put a vacuum gauge in it, you can achieve better driving habits (in relation to fuel economy) both when accelerating AND while cruising.

Accelerating we already discussed and it is straightforward, both in concept and practice. But while cruising? can we actually achieve improved millage while cruising? YES! At some point while in cruising conditions we will see an almost direct relation of vacuum gauge indication vs speed. For example at 45 mph we might see 18 at 50 we might see 16 at 55 we might see 14 etc. (notice that there is a fairly direct relation of (in this example at least) of vacuum to to speed of 2 inches of vacuum to 5 mph) Now, predictably at 70 we should see 8 but we will really see maybe 4. What just happened? If we were paying attention we might have noticed that at somewhere between 65 and 70 the needle suddenly dropped dramatically in relation to the speed increase of the vehicle. We just passed the point of maximum economy (at high cruising speeds that is) So, if we simply cruise at something like 65 we will achieve a couple of miles a gallon more than at 70. This will vary from car to car, speed to speed, temperature, wind speed and direction etc. That's why the gauge can be so helpful. Now in a newer car with fairly good mileage in the first place it will not make too much of a difference on your pocketbook, but in a truck or rv, where you may be getting only 3 to 8 miles to the gallon an extra mile or two adds up really fast. This is also why you will see some truckers (driving trucks that you know have the power to do otherwise) will allow the truck to slow on a small hill rather than force the truck to maintain speed. At the top they will more than likely regain all lost speed as it will probably be downhill after and in the end, there will only be a couple of minutes difference in arrival time, (even if the trip is a lengthy one) but the trip may well cost a few hundred dollars less in fuel. Besides, unlike you on a trip, when you get home, you go in, they often cannot unload until a set time at their destination, and will have to kill time once there anyway.

So, now you have some understanding of the answer to your question, as well as a way to apply said newly gained knowledge to the real world and perhaps into actual savings on fuel and wear and tear on your vehicle.

Hope this was clear and understandable enough, if you require some clarification please let me know.

Bob

 

[Clovis Man]

The easy way to boil this all down is to equate it to a car with a manual transmission --

RPM = gear. High RPM=first gear. Try running wide open in first gear for very long and you'll blow the engine to smithereens -- piston slap, timing chain, etc. You might even break the crankshaft. This would be like running 3000 RPM in the Mustang all the time.

Manifold pressure = throttle setting. Put your car in high gear and floor the accelerator at too slow a speed and your engine might ping or even shake apart. This is the same as running 67" MP at 2000 RPM or less.

Not to step on BobK1's toes or anything... hope I didn't...

 

[the beav]

I am guessing that this is a P51-B, notice the lack of the bubble canopy. I believe the P51-D first had the bubble. The B model was widely used but the D and H are the classic Mustangs.

More likely it's the P-51C as shown here:

http://www.redtail.org/?p=181

 

[evandood]

More likely it's the P-51C as shown here:

http://www.redtail.org/?p=181

I thought the "C" was aerial recon and training, although I could be wrong. That cockpit has 2 seats in your example.