Yes. In my above post, I tried to use the same terminology as found in the Corky Meyer quote, which was a bit different than the one I was used to.
OK.
The superchanger sequence "Neutral Gear, Low Gear, High Gear" you pointed out is what I'm familiar with, too, and the Corky Meyer quote seems to use "Low Gear, Main Stage, High Gear" instead. (Maybe I misunderstood that.)
I haven’t seen the quote to which you refer. But frankly, this doesn’t make any sense. It would be a very inefficient to fly the plane in this matter. Maybe it was a mis-speak, or an error.
The R-2800-8 makes more power at sea-level in neutral blower than in low-blower. And it makes more power at medium altitude in low-blower than it would in neutral. On top of that, at medium altitude, in neutral, there would be no ram effect.
Yes that's the normal sequence. However, it seems that this is not what happens in the BuAer data set for the F6F-5:
http://www.history.navy.mil/branche...-ac/fighter.htm
That’s exactly what happens. Neutral, Low, and High are all represented at both Military Power and Combat Power on both the climb and speed charts – in the correct order of use. You’d get a wild looking chart if they were represented in the “low-neutral-high” sequence.
The problems I have with the BuAer graph can maybe explained best using the climb graph.
You can see that at MIL, the full throttle height of Neutral Gear is just below 2000 ft.
The “full throttle” term is mucking things up at this point and perhaps it’s a point of confusion..
That point to which you refer at the 2,000 foot mark in Military Power is the critical altitude of the engine in neutral blower at Military Power. The plane would not be at full throttle at that point. The throttle would be at the military power setting. The full throttle position would have made put it at combat power.
At the higher boost at Combat Power, full throttle height would be about -500 ft, so Neutral Gear is not used in climb at Combat Power.
No, neutral blower is used in the combat power climb. Both the Military Power and the Combat Power climb lines are in three clear stages, and that represents the three blower stages. Have a look:
The neutral blower (the red line) is used in the initial climb stages at both military power and combat power. They are used up to their critical altitudes. The critical altitude of the engine in neutral blower is higher at combat power than it is at military power. Once the critical altitude is reached, power begins to drop off. That drop-off is represented by the first bend and the more horizontal portion of the red line. Once it reaches the point where low-blower can develop maximum power, the blower is shifted from neutral to low (green line). That shift is represented by the upward turn in the line (the point where the line turns from red to green).
It starts all over again. Low blower (the green line) is used up to its critical altitude (represented by the bend in the green line). At that point, power begins to drop off. Once a point is reached where high blower can develop maximum power, low blower is shifted (where the green line meets the blue line) to high blower (the blue line).
At Military Power, the shift from low to high occurs at about 18,000 feet. At Combat Power, the shift occurs at about 20,000 feet.
Once the plane is in high blower, it continues to climb until its critical altitude is reached – about 21,000 feet according to the chart. As you can see from the chart, once the blower is shifted to high, the military power line and the combat power line quickly converge – at about 20,000 feet.
(Note: critical altitudes for military power and for combat power in low and high blower are achieved at the same altitudes)
The entire Combat Power climb is pretty much a “full throttle climb.” The Military power climb is not a “full throttle” climb until an altitude is reached where full throttle is necessary to develop military power. That’s where the top and longest portion of the blue lines comes in.
When the high-blower combat power critical altitude is reached, the throttle is as far forward as it will go. That is the highest point where combat power can be maintained. After that, combat power can no longer be maintained and power begins to drop. And there is nothing the pilot can do about it. Sooner or later, power drops off to the point where even full throttle will not maintain Military power.
That’s where this chart is a little confusing. The military power critical altitudes in low and high blower should be a little higher than the combat power critical altitudes. That’s because you can maintain a lower power at higher altitude when you may not be able to maintain high power at that same altitude.
Hm, do you mean a power chart? Ram would be automatically taken into account for flight test data.
Regards,
Henning (HoHun)
No, I have the power charts for the R-2800-8, the engines used in the Hellcat. I don’t think ram is taken into consideration. These things were usually tested in chambers where atmospheric pressure could be altered to simulate a particular altitude. No ram was possible in the chambers, so many engine power charts don’t take ram into consideration. Some charts are “corrected” to take ram into consideration, but I don’t think mine are. If mine do represent power with ram, then I’d have to say emphatically that there is no benefit to using low blower at sea-level. Not only is there no benefit, it would be detrimental to performance.
