Schweizer 300CBi Hover Performance Chart

[RtrCFI]

Greetings. For the following question I refer you to Figure 5-7 in the Schweizer PIM/POH. "In Hover Ground Effect Ceiling Versus Gross Weight."

 

1.) Simply put, I am confused by the vertical dashed line labeled "8000 FT Density Altitude" What is the significance of being to the RIGHT of the line? (Full throttle?)

 

2.) Furthermore, what happens in conditions to the LEFT of the line?

 

3). Page 5-1 of the PIM/POH mentions a hovering ceiling of 4600 altitude (2 ft skid height) Is this to mean that the helicopter will not hover AT ALL above 4600'?

 

Any help is appreciated.

[Helix]

Hi, as far as question three goes that is at max gross weight and standard day (15C and 29.92"). So yes that means it will not hover above that altitude (4600ft). Now if the air cools down or you have a lighter load then it will hover at higher altitudes. I'm flying the 300C and the other charts you mention aren't the same so I'm not sure. Sometimes it takes awhile just staring at them and figuring out the general idea, keep one number the same and slide along the other variable for example.

[Jeff]

Greetings. For the following question I refer you to Figure 5-7 in the Schweizer PIM/POH. "In Hover Ground Effect Ceiling Versus Gross Weight."

 

1.) Simply put, I am confused by the vertical dashed line labeled "8000 FT Density Altitude" What is the significance of being to the RIGHT of the line? (Full throttle?)

 

2.) Furthermore, what happens in conditions to the LEFT of the line?

 

3). Page 5-1 of the PIM/POH mentions a hovering ceiling of 4600 altitude (2 ft skid height) Is this to mean that the helicopter will not hover AT ALL above 4600'?

 

Any help is appreciated.

 

There are two ways to use that graph. The first is to find your pressure altitude (PA) on the left side, and draw a line horizontally to the right until it intersects the temperature. Then go straight down to find the maximum weight the helicopter can be to hover IGE.

 

The second way is to find the gross weight of the helicopter on the bottom, and draw a line vertically upward until it intersects the temperature. Then draw a line horizontally to the left to find the maximum PA you can hover at under those conditions of weight and temperature.

 

When using the graph in the manner I described first, and the horizontal line you draw from the current PA at your field will not intersect a temperature line, then you stop the horizontal line at the dashed "8000 ft Density Altitude" line. Looking straight down from there, you will find the maximum gross weight the helicopter can be to hover IGE.

 

When using the graph in the manner I described second, and your gross weight is at or to the left of the dashed line, then 8000 feet is the maximum density altitude (DA) at which you can hover the helicopter IGE. In this case, you must calculate the DA at your airport or locataion to make sure it is not over 8000 feet.

 

Theoretically, you could extrapolate the temperature lines, but Schweizer has put a limitation of 8000 feet DA on the helicopter for IGE hover.

 

So to directly answer your questions 1 & 2, if your gross weight is to the right of the dashed line, then you have to find the max PA for HIGE using the graph. If your gross weight is to the left of the dashed line, then 8000 feet DA is the limit.

 

~Jeff